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A 1994 SURVEY FOR UNIONIDS FROM THE HEADWATERS OF THE ROOT RIVER SYSTEM, SOUTHEASTERN MINNESOTA TO THE MISSISSIPPI RIVER.
MARIAN E. HAVLIK, Malacological Consultants, 1603 Mississippi
Street, La Crosse, Wisconsin 54601-4969.
Phone/FAX: 608-782-7958.
Minnesota's Root River system apparently has never been surveyed for unionids. We sampled from 6 - 17 June 1994 at 117 bridge and road access sites between the Root River headwaters and the Mississippi River. We also sampled on the nearby Upper Iowa (2 sites) and Little Iowa Rivers (8 sites), for a total of 127 sites.
A popular canoeing river, the main stem of the Root River starts NE of Lanesboro, MN, at the confluence of the North and Middle Branches of the Root River, and flows easterly to its confluence with the Mississippi River, between La Crescent and Brownsville, MN, opposite La Crosse, WI. Sampling consisted of wading and shoreline searches in the headwaters and middle reaches of the river system, and shoreline searches by boat in the lower six miles of the Root River from Hokah, MN, to the river's mouth.
This survey included the main stem and all four major tributaries, and yielded at least 16 unionid species. However, only three species were found alive, represented by five living mussels: Venustaconcha e. ellipsiformis (Conrad, 1836), Ellipse (3), and Lampsilis radiate luteola (Lamarck, 1819), Fatmucket (1) were found at one South Branch site, 0.5 mi N of Etna, MN, and one Anodontoides ferussacianus (Lea, 1834) Cylindrical Papershell, was found at a North Branch site, 4 mi NW of Dexter, MN. A number of the remaining species were represented by fairly fresh-dead shells.
The most species (12) were found in the North Branch Root River, among 22 sites, however the most shells were found in the South Branch among 40 sites (nine species). Eleven species were found among eight sites on the Middle Branch Root River. The most common species found, both dead and alive, Venustaconcha e. ellipsiformis, also lives in the Cannon and Zumbro Rivers of southeastern Minnesota, but, strangely enough, was not found in western Wisconsin for over 60 years, until 1992 - 1994.
Our data show severe impacts to the Root River system. Since we have not finished sampling the river system, we were unable to pinpoint the precise impacts that led to this situation. Our preliminary conclusions are that cumulative impacts, primarily agricultural (livestock in streams, and farm and road chemicals) are apparently responsible. The only refugia appear to be the headwaters and small tributaries. Since the Zebra Mussel is exploding in the Mississippi system, we must quickly identify tributary molluscan fauna, or risk losing unique populations before they can be identified. We hope to have additional funding to complete sampling of the river system, including tributary creeks. This project was funded by the Minnesota Nongame Wildlife Program from contributions to the Minnesota Nongame Wildlife Tax Checkoff.
SOUTHERN REGION MUSSEL SURVEYS AND STUDIES.
LEIGH ANN McDOUGAL, U.S. Forest Service, 110 Southpark Drive,
Blacksburg, VA 24060.
Phone: 540-552-4641. FAX: 540-552-4376.
In case anyone is interested in this information, listed below are mussel surveys and studies that have been funded by the Southern Region of the Forest Service in the last 5 years. For more detailed information, please call the contacts listed for each Forest.
ALABAMA - National Forests in Alabama
Contact: April Hargis, 334-832-4470
1. A Mussel Survey of the Streams Draining Bankhead National Forest
and the Oakmulgee Division of Talladega National Forest, Alabama.
Conducted by Stuart McGregor with the Alabama Geological Survey
(1992).
2. A Survey of the Unionid Mussels of the Talladega National Forest,
Shoal Creek and Talladega Ranger Districts. Conducted by Malcolm
Pierson, an aquatic biologist with Alabama Power (1992).
3. A Qualitative Assessment of the Unionid fauna Found in Streams in
and near the Tuskegee National Forest. Conducted by Monte McGregor, a
graduate student at Auburn University (1993).
4. A Survey of the Mollusks of Conecuh National Forest, Escambia and
Covington Counties in South-Central Alabama. Conducted by Doug
Shelton with Vittor & Associates, Inc. (1995).
5. Mel Warren and Wendell Haag with the Southern Forest Experiment
Station in Oxford, MS began a mussel study on the Bankhead District
in 1993. The objectives of this study were to characterize aspects of
the mussel communities including species composition and density,
demographic structure, fish hosts, and physical habitat
characteristics; and to develop survey and monitoring protocols that
could be used by National Forest personnel. The study was expanded in
1995 to include the Shoal Creek District. Call Mel or Wendell at
601-234-2744 for more information.
ARKANSAS/OKLAHOMA - Ouachita National Forest
Contact: Rich Standage, 501-321-5202 or Betty Crump,
501-356-4187
1. Stream Inventory of Lampsilis powellii Populations on National
Forest Lands. Conducted by Arthur and Kristine Brown with ECOLAB
(1989).
2. Survey of the Freshwater Mussels of the South Fourche LaFave River
and Major Tributaries. Conducted by John Harris with Arkansas State
University (1992).
3. Mussels of the Phase III Ecosystem Management Project Watershed
(Alum Fork, Saline River Drainage, Arkansas). Conducted by Carol
Johnston with the Southern Forest Experiment Station, Oxford, MS
(1993).
4. Survey for Arkansia wheeler) and Other Rare Unionids in the Tiak
District. Conducted by Caryn Vaughn, Christopher Taylor, Kelly
Eberhard and Mathew Craig with the Oklahoma Biological Survey,
Oklahoma Natural Heritage Inventory (1994).
5. Microhabitat and Population Analysis of Lampsilis powellii in the
South Fork Ouachita River, Montgomery County, Arkansas. Conducted by
John Harris (1994).
6. Survey of the Freshwater Mussels of the Poteau River Drainage in
Arkansas. Conducted by John Harris (1994).
7. 1996 - Cooperative agreements signed for Caryn Vaughn to survey a
portion of the Glover River in Oklahoma; an John Harris to survey
mussel beds in the upper Ouachita River.
Ozark-St. Francis National Forests
Contact: Craig Hilburn, 501-968-2354
1. Mulberry River Freshwater Mussel Survey. Conducted by Joe
Stoeckel, Lindsey Lewis, and Shannon Shook with Arkansas Tech
University (1995).
FLORIDA - National Forests in Florida
Contact Bob Grinstead, 904-669-3153
1. St. Johns River System Preliminary Mollusk Survey - conducted by
TVA, Forest Service and Fish and Wildlife Service personnel
(1993).
GEORGIA - Chattahoochee and Oconee National Forests
Contact: Mitzi Pardew, 770-536-0541
1. Mussel Survey of some streams on the Armuchee District. Conducted
by Forest Service personnel (1995).
KENTUCKY - Daniel Boone National Forest
Contact: Vicki Bishop, 606-745-3100
1. A Survey of the Unionids of Middle Fork, Rockcastle River,
Kentucky. Conducted by Ron Cicerello with the Kentucky State Nature
Preserves Commission (1992).
2. A Survey of the Unionids of the Rockcastle River, Billows,
Kentucky, to the Cumberland River. Conducted by Ron Cicerello, KSNPC
(1994).
3. A Survey of the Unionids of Marsh Creek, McCreary County,
Kentucky. Conducted by Ron Cicerello, KSNPC (1995).
4. A survey of the Redbird River is in progress this year (1995).
LOUISIANA - Kisatchie National Forest
Contact: Emlyn Smith, 318-765-3554 or Dave Peterson,
409-639-8541
1. Field Notes from a Survey of Margaritifera hembeli on U.S.F.S.
property, Catahoula Ranger District, Kisatchie National Forest.
Conducted by Paul Johnson and Kenneth Brown with Louisiana State
University (1994).
MISSISSIPPI - National Forests in Mississippi
Contact: Rick Dillard, 601-965-5484
1. Current Distributional Information on Freshwater Mussels in
Mississippi National Forests. Literature and museum review conducted
by Wendell Haag and Mel Warren with the Southern Forest Experiment
Station (1995).
NORTH CAROLINA - National Forests in North Carolina
Contact: Donley Hill, 704-257-4205
1. Croatan National Forest Inventory: Mollusks, Crayfish, and
Mammals. Conducted by John Alderman, Therese Conant, Thomas Henson
and Chris McGrath with the NCWRC Nongame and Endangered Wildlife
Program (1994).
2. Uwharrie Mountains Inventory: Mollusks, Crayfish, and Mammals.
Conducted by John Alderman and Chris McGrath, NCWRC (1994).
3. Mussel Survey on a portion of the Nolichucky River. Conducted by
Forest Service personnel (1995).
4. Mills River and tributaries. Conducted by Jim Layzer and Lesa
Madison with TN Tech University (in progress).
SOUTH CAROLINA - Francis Marion and Sumter National Forests
Contact: Kelly Russell, 803-561-4067
1. Freshwater Mussels of the Chattooga River. Conducted by Jenny
Adkins with NRCS (1995).
2. Freshwater Mussel Inventory of the Stevens Creek Subbasin, Long
Cane Ranger District, Sumter National Forest, South Carolina.
Conducted by John Alderman (1995).
TENNESSEE - Cherokee National Forest
Contact: Jim Herrig, 423-476-9751
1. The Cherokee National Forest has been conducting mussel surveys in
the de-watered section of the Hiwassee River since 1993 with the help
of biologists from many different agencies. In 1996, they hope to
initiate a study with the Southern Forest Experiment Station to
compare the contents of muskrat middens to actual mussel populations
in the Hiwassee.
TEXAS - National Forests in Texas
Contact: Dave Peterson, 409-639-8645
1. Stephen F. Austin University conducted mussel surveys of the Davy
Crockett and Angelina National Forests in 1994 and the Sam Houston
and Sabine National Forests in 1995.
VIRGINIA - George Washington and Jefferson National Forests
Contact: Mark Hudy, 540-564-8300.
1. Annual Reports, Distribution
of the James Spinymussel in Streams of the Jefferson and George
Washington National Forests - conducted by Martin O'Connell and Dick
Neves with Virginia Tech (1991- 1992).
2. Mussel Survey of Clinch River tributaries on the Clinch Ranger
District - conducted by Forest Service personnel (1995).
SUBMITTED BY: Don Hubbs, Comm. Mussel Program Supervisor
(615)781-6575
Tennessee Wildlife Resources Agency
P.O. Box 70
Camden, TN 38320
Commercial Mussel Harvest Status: Exploitation of Federal listed endangered mussel species by Kentucky Reservoir mussel harvesters continues. Thus far eight specimens of endangered mussel species (7 Plethobasus cooperianus, 1 Lampsilis abrupta) have been confiscated from commercial shell buyers and harvesters. Five of the eight specimens were fresh dead (all were Plethobasus cooperianus). Commercial mussel harvesters and shell buyers have demonstrated their inability to separate this species from Cyclonaias tuberculata, which constitutes approximately 0.1% of the shells normally harvested. Based on this information, I have recommended that the Tennessee Wildlife Resources Commission (TWRC) remove all species which might be confused with P. cooperianus. This list includes Cyclonaias tuberculata, Quadrula pustulosa, and Q. nodulata. This action would not impose significant economic hardship on the mussel harvesters or buyers, since all three species combined make up only 0.16% of the annual shell harvest. I expect the TWRC to take action on this matter during their November meeting. If the TWRC does not remove these species, I expect commercial musselers will continue indiscriminately harvesting P. cooperianus. This would be a tragedy, in that the majority of the P. cooperianus examined from the harvest appear to be relatively young specimens, evidence of recruitment within the last 10 to 15 years.
Commercial Mussel Stock Restoration: During October, 1994 approximately 300 blue and channel catfish were infected with Megalonaias nervosa glochidia. A conservative estimate of S0 glochidia per fish yields a total infection of about 15,000 encysted glochidia released into Kentucky and Barkley reservoirs. Transformation was not confirmed, however a sample of both fish species held in a floating cage in Kentucky Reservoir carried the glochidia until May, when the water temperature reached 65 - 70-oF. In August, heavy infections of Amblema p. plicata on hybrid sunfish (Lepomis macrochirus x L. microlophus) were obtained via an improved infection technique. Transformed juveniles were collected within 5 days post infection (water temp. 80-oF), from fish held in test aquariums. Propagation test sites were established on Old Hickory and Kentucky reservoirs. At each site a quantity of sunfish bearing A. p. plicata glochidia were held in floating cages anchored over favorable substrate. Approximately 14 days post infection, fish were inspected for unshed glochidia and released. The cages were constructed to allow the transformed juveniles to pass through the cage and settle in the vicinity. These test sites will be monitored for evidence of production during 1997.
Zebra Mussel status: The sky has yet to fall on Kentucky Reservoir. Although zebra mussels were encountered with greater frequency during Spring harvester surveys; Summer surface water temperatures exceeding 95-oF(83-oF at depth 50 ft.) and predation by fish appear to have thwarted a zebra mussel explosion for another year. TVA's zebra mussel monitoring station at TRM 100.5, New Johnsonville, TN Fossil Plant, revealed fewer zebra mussels per square meter at Summers end than were collected earlier in the year during both 1994 and 1995 (Bernie Kerley and Johnny Buchanan, personal communication). Scientists who years earlier predicted that the zebra mussel would destroy Kentucky Reservoir's commercial mussel industry within 2 years of the first collection failed to adequately consider the predation power of the existing fish assemblage and veliger mortality during the spawning season. If the zebra mussel ever does develop into a threat to the mussel industry, it will require several more years than predicted.
An Evaluation of Relocation and Holding of Unionid Mussels in an Artificial Pond
Authors: Teresa Naimo1, Pamella Thiel2, and
Kurt Welke3
Address: 1National Biological Service, Upper Mississippi
Science Center, LaCrosse, WI
2USFWS, LaCrosse Fishery Resources Office, Onalaska,
WI
3Wisconsin Department of Natural Resources, Prairie du
Chien, WI
Phone: Naimo (608-783-6451), Thiel (608-783-8431), Welke
(608-326-0233)
In many large rivers, unionid mussels are at risk from the exotic zebra mussel. The use of artificial ponds, such as those found in National Fish Hatcheries, are being evaluated as temporary holding locations for mussels until the immediate threat of zebra mussels has passed or until artificial propagation has been successfully developed. Data on growth and survival of mussels relocated to an artificial pond was compared to similar data obtained from mussels treated similarly but relocated to a natural setting within the upper Mississippi River (UMR). In May 1995, we obtained 1392 mussels representing five species (Amblema plicata, Fusconaia flava, Leptodea fragilis, Obliquaria reflexa and Quadrula quadrula) from the UMR. Each mussel was scrubbed 'free' of zebra mussels and placed into a quarantine pond. After 34 days, unionids were re-inspected for zebra mussels, individually tagged, and length, height, and wet weight were recorded. Mussels were randomly assigned to treatments at either a 1.2 acre pond at a National Fish Hatchery, or the UMR. The treatments were the physical structures used to hold the mussels and consisted of suspended mesh bags, buried and suspended trays containing dredge spoil, and corrals around the natural substrate. There were four replicates of each treatment, each containing 24 mussels.
We found no zebra mussels on any live unionids after the 34-day incubation. Mean survival of mussels during the quarantine period was 83% and ranged from 55% in L. fragilis to 97% in Q. quadrula. In September 1995, we randomly retrieved mussels from the treatments. We found no zebra mussels on any unionid relocated to the pond, but mussels relocated to the UMR contained an average of 3.1 zebra mussels per unionid. Survival, combined over all five species, was significantly different between the pond (71%) and river-relocated mussels (95%). In addition, survival was significantly different among treatments; highest survival rates were found in the suspended trays, while poorest survival was generally found in the buried trays. Finally, we observed species-specific differences in survival. In the pond, fragile papershells (L. fragilis) did not fare well, with only 49% surviving the first few months. In contrast, survival ranged only from 91% to 97% among all species in the river. Both the pond and river-relocated mussels will be monitored for growth and survival at least once a year for a minimum of two years.
Host research on round pigtoe glochidia
Mark C. Hove
University of Minnesota, Department of Fisheries & Wildlife
1980 Folwell Avenue, St. Paul, MN 55108
(612) 624-3019
e-mail: mh@finsandfur.fw.umn.edu
The round pigtoe is a freshwater mussel found in rivers throughout a large portion of the Mississippi River drainage, and parts of the Great Lakes drainage (Williams et al. 1993). Pleurobema coccineum is listed as Endangered in Iowa and of Special Interest in Ohio (Cummings and Mayer 1992).
Little is known about the host requirements of P. coccineum glochidia. Round pigtoe glochidia have been observed naturally infesting the gills of bluegill, Lepomis macrochirus (Surber 1913, Coker et al. 1921).
A gravid P. coccineum collected from the St. Croix River released glochidia in the laboratory on 17 July 1995. Glochidia were tightly packed into conglutinates which were slightly negatively buoyant. Conglutinates were white, thin, tapered at both ends, and 4-6 mm wide, 10-15 mm long. Most conglutinates were released individually, although some were released in groups of two to four attached at one end.
Seven species of fish collected from lakes and streams not known to contain P. coccineum were exposed to glochidia in the laboratory. Three cyprinid genera facilitated glochidia metamorphosis to the juvenile stage (Table 1). Table 1. Suitable and unsuitable fish hosts for Pleurobema coccineum glochidia.
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Literature Cited
Coker, R E., A. F. Shira, H. W. Clark, and A. D. Howard. 1921. Natural history and propagation of fresh-water mussels. Bull. U. S. Burl Fish. 37: 75-181.
Cummings, K. S., and C. A. Mayer. 1992. Field guide to freshwater mussels of the Midwest. Illinois Natural History Survey Manual 5. 194 pp.
Surber, T. 1913. Notes on the natural hosts of fresh-water mussels. Bull. U.S. Burl Fish. 32: 101-115.
Williams, J. D., M. L. Warren, Jr., K. S. Cummings, J. L. Harris, and R. J. Neves. 1993. Conservation status of freshwater mussels of the United States and Canada. Fisheries 18(9): 6-22.
Suitable fish hosts of the lilliput, Toxolasma parvus
Mark C. Hove
University of Minnesota, Department of Fisheries & Wildlife
1980 Folwell Avenue, St. Paul, MN 55108
(612) 624-3019
e-mail: mh@finsandfur.fw.umn.edu
Toxolasrna parvus is found in streams and rivers throughout east-central North America The distribution and abundance of this species is currently considered stable (Williams et al. 1993).
Various centrarchids are believed to serve as hosts for T. parvus glochidia. Toxolasrna parvus glochidia have been observed infesting the gills of Lepomis gulosus (Wilson 1916). Lepomis gulosus. L. cyanellus, L. humilus, L. macrochirus, and Pomoxis annularis are considered hosts for T. parvus glochidia (Fuller 1974).
A gravid T. parvus was collected from sandy substrate at 10 cm depth from the Mississippi River north of Minneapolis, MN during July 1995. The female released individual glochidia in the laboratory. Three fish species collected from lakes not known to contain T. parvus were exposed to a bath of glochidia for 2.75 hours. Fish species were held in separate aquaria which were siphoned three times a week to collect juvenile mussels.
Of three species exposed to T. parvus glochidia, only L. cyanellus facilitated glochidia metamorphosis (Table 1). Over 300 juveniles were collected from the aquarium holding the year-old L. cyanellus.
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Literature Cited
Fuller, S. L. H. 1974. Clams and mussels (Mollusca: Bivalvia). Pages 215-273 in C. W. Hart and S. L. H. Fuller, eds. Pollution ecology of freshwater invertebrates. Academic Press, Inc., New York, New York. 389 pp.
Williams, J. D., M. L. Warren, Jr., K. S. Cummings, J. L. Harris, and R. J. Neves. 1993. Conservation status of freshwater mussels of the United States and Canada. Fisheries 18(9): 6-22.
Wilson, C. B. 1916. Copepod parasites of fresh-water fishes and their economic relations to mussel glochidia. Bulletin of the U.S. Bureau of Fisheries 34: 331-374.
FRESHWATER MUSSEL SURVEYS OF RIO GRANDE TRIBUTARIES IN CHIHUAHAU, MEXICO
Robert G. Howells and Gary P. Garrett
Texas Parks and Wildlife Department
Heart of the Hills Research Station
Ingram, TX 78025
Within the Rio Grande drainage of Texas and Mexico, four freshwater mussel species (Unionidae) were endemic and a fifth occurred both in the Rio Grande and in Central Texas. Relatively few studies have addressed these species in this century (Taylor 1967; Metcalf 1974, 1982; Neck and Metcalf 1988) and their recent status is largely undocumented. After Texas Parks and Wildlife Department's (TPWD) Heart of the Hills Research Station began statewide unionid surveys in 1992, it quickly became apparent the continued secure existence of these five species was in doubt.
Among the endemic taxa, Quadrula couchiana has not been reported in many decades. Truncilla cognata has not been reported since 1972 (Metcalf 1982). Popenaias popei was last reported by Murray (1975) and not found again until TPWD recovered a single, recent shell in 1992. Potamilus (Disconaias) salinasensishas been represented recently only by fresh shells in 1972 (Metcalf 1982) and a single, recent shell found by TPWD in 1992. Additionally, Quincuncina mitchelli has been found only as subfossil fragments in Central Texas rivers in TPWD surveys; none were found in the Rio Grande drainage.
In an effort to determine if any of these species persist within the Mexican drainage of the Rio Grande, G.P. Garrett and the HOH staff incorporated collection of freshwater mussels as part of TPWD desert fishes surveys in Chihuahua in 1994 and 1995. In August 1994, sites were sampled on the Rio Conchos (Cuchillo Parado, Wow Julimes and Valle de Zaragosa), the Rio Chuviscar and the hot springs at San Diego de Alcala, Ojo de Talmantes (Rio Florido tributary), Rio San Pedro south of Satevo, Rio Santa Isabela (upstream and at Riva Palacio), headwaters of the Rio Conchos, and Ojo del Rey near Angostura in October 1995, seven more sites in northern Chihuahua were also sampled. These were Ojo W Alamo (NW of Coyame), Rio Coyame and adjacent hot springs at Coyame, Ojo de Laguna (endorheic drainage N of Ciudad Chihuahua), headwaters of the Rio Chuviscar in two locations, and the Rio Chuviscar and the hot springs at San Diego de Alcala
No living unionids were found at any of these locations. Indeed, the only evidence of freshwater mussels obtained was the collection of one long-dead and several subfossil valves of an unidentified unionid taken in the Rio Conchos just downstream of Julimes. Many sites showed signs of dewatering, scouring, agricultural impacts, or general lack of acceptable mussel habitat Many of the Mexican tributaries of the Rio Grande appear to have suffered the same habitat modifications and mussel losses found during TPWD surveys on the Texas side of the border.
Several more wide-ranging taxa (e g., Cyrtonaias tampicoensis, Quadrula apiculata, and others) still persist at a number of sites in the Rio Grande. Other locations both in Texas and Mexico remain to be surveyed. However, except for one shell each of P. popei and P. salinasensis in 1992, no evidence of these five, unique Rio Grande unionids has been found by TPWD. Thus far, Mexican tributaries appear to have offered little refuge for these mussels.
REFERENCES Metcalf, A.L. 1974. Fossil and living freshwater
mussels (Unionacea) from the Pecos River, New Mexico and Texas.
Bulletin of the American Malacological Union 1973:47-48.
Metcalf, A.L. 1982. Fossil unionacean bivalves from three tributaries
of the Rio Grande. Pages 43-59 in J.R. Davis (ed.).
Proceedings of the symposium on recent benthological investigations
in Texas and adjacent states. The Texas Journal of Science, Austin,
278 pp.
Murray, H.D. 1975. Melanoides tuberculata (Muller) in Las
Moras Creek, Brackettville, Texas. Bulletin of the American
Malacological Union 1975:43. Neck, R.W., and A.L. Metcalf. 1988.
Freshwater bivalves of the lower Rio Grande, Texas. The Texas Journal
of Science 40:259-268.
Taylor, D.W. 1967. Freshwater mollusks collected by the United States
and Mexican boundary surveys. The Veliger 10:152-158.
Society for the Conservation of Margaritiferidae
A new society was formed at the Twelfth International Malacological Congress in Vigo, Spain, September 1995, to promote the conservation and management of margaritiferid species around the world. The freshwater pearlshells of the family Margaritiferidae include 25 nominal genera that inhabit rivers of North America and Eurasia, with some species and many populations in imminent danger of extinction or extirpation, respectively. The SCM was formed by a multinational cadre of scientists for the purpose of coordinating international efforts for research, management, and the protection of habitats critical to these species. We propose to evaluate and respond through correspondence to threats to this faunal group, as identified by members throughout the world.
At this time, we seek new members to SCM, to further the conservation goals of the society. There are no membership fees currently, and we ask only that you assist the society by providing information on the status of pearlshells in your locale, and informing us of new threats to which SCM can voice its opinion. One of the long-term goals of SCM is to create an international monograph on the systematics, distribution, ecology, and status of margaritiferids globally. A symposium and possible field expeditions are contemplated within the next few years.
If you are interested in joining SCM, please send your name, mailing address, telephone and fax numbers, email address, and main interest (species or topic) to the SCM Secretary or President identified below.
Richard Neves, Secretary, SCM
Department of Fisheries and Wildlife Sciences
106 Cheatham Hall, Virginia Tech
Blacksburg, VA 24061-0321
PHONE: 540-231-5927 FAX: 540-231-7580
email: FISHHEAD@VTVM1.CC.VT.EDU
Valery Ziuganov, President, SCM
Institute of Developmental Biology
Russian Academy of Sciences
Vavilov Str. 26
Moscow, 117808, Russia
FAX: 095-135-8012
email: VZIUG@IBRRAN.MSK.SU
G. Thomas Watters & Scott O'Dee
Aquatic Ecology Laboratory, Ohio State University
1314 Kinnear Rd., Columbus, OH 43212
voice: 614-292-6170
fax: 614-292-0181
email: gwatters@magnus.acs.ohio-state.edu
New publications:
Watters, G. T. 1995. Sampling freshwater mussel populations: the bias of muskrat middens. Walkerana 7: 63-69.
Shells of freshwater mussels collected from middens of muskrats (Ondatra zibethicus) often are used in unionid survey work as indicative of the in situ population. The relative abundance of mussel species in samples collected from middens was compared with adjacent beds in the lower Muskingum River in Ohio. All samples from middens differed significantly in both mussel diversity and relative abundance from the beds from which they were derived. Samples collected from muskrat middens represent a biased sample that may lead to erroneous conclusions concerning population and community structure of the parent bed.
Watters, G. T., & H. L. Dunn. 1995. The Unionidae of the lower Muskingum River (RM 34.1-0), Ohio. Walkerana 7: 225-263.
The lower 55 km (34 miles) of the Muskingum River were surveyed in October 1992 for Unionidae by hand-picking, brailing, and diving. Muskrat middens were examined from October 1992 through October 1993. Forty species and 11,145 individuals were found. Nine of these were encountered only as weathered shells and are presumed extirpated from the study area. Five federally endangered taxa were found, although only Cyprogenia stegaria (Rafinesque, 1820) was collected alive. Other federally endangered taxa found as weathered shells were: Lampsilis abrupta (Say, 1831), Plethobasus cicatricosus (Say, 1829), Pleurobema clava (Lamarck, 1819), and Pleurobema plenum (Lea, 1840). Fourteen Ohio endangered species were found (including federally endangered species). Four of these appear to be reproducing and may occur nowhere else in the state: Ellipsaria lineolata (Rafinesque, 1820); Plethobasus cyphyus (Rafinesque, 1820); Pleurobema cordatum (Rafinesque, 1820); and Quadrula cylindrica cylindrica (Say, 1817). Mussels are distributed in six beds located downstream of the first five km of each of four locks and dams. Average bed densities ranged from 3.1 to 41.9 individuals/m2, with a maximum density reaching 124 individuals/m2. The fauna is dominated by five species, all of which have some commercial value: Obliquaria reflexa Rafinesque, 1820; Quadrula pustulosa (Lea, 1831); Amblema plicata (Say, 1817); Pleurobema cordatum, and Quadrula quadrula (Rafinesque, 1820). The commercially valuable Megalonaias nervosa (Rafinesque, 1820) is becoming established in the lowest pool with recruitment evident. The State of Ohio is closed to commercial collecting, although poaching pressure for the cultured pearl industry is a serious threat to these beds.
Towards "natural" reproduction of freshwater mussels in enclosures - preliminary results
With the current efforts to remove mussels to hatcheries and other enclosures to avoid mortality from zebra mussels, it is important to determine if mussels can reproduce while in captivity We have established two host-mussel populations in outdoor enclosures to determine whether this is feasible. The first enclosure contains twenty hatchery raised largemouth bass and twenty Amblema plicata. The sex ratio of the mussels has not been determined. The second enclosure contains twenty hatchery raised largemouth bass and ten male and ten female Lampsilis radiata siliquoidea. Enclosures are 3028 liter [800 gallon] tubs with a 1.8 m base diameter. Mussels are kept in sediment-filled containers. Glochidia samplers are placed in the bottom and checked every other day. No effort is made to control water temperature or quality. Lampsilis individuals have been in place for four months, Amblema individuals three. To date, no mussels have been lost. Five bass have died, primarily to leaping out of the tubs. To date, no glochidia have been found in the Amblema tub.
We have recorded three Lampsilis "release events," in which living glochidia were found in the samplers. These events have diminished in strength and become less narrowly focused over time as water temperatures have fallen. The initial event involved approximately 4000 glochidia, subsequent ones several hundred glochidia. No metamorphosed glochidia have yet been found in the samplers. However, a dead bass was examined and found to have numerous glochidia attached to its gills. These glochidia appear to be overwintering on the hosts rather than metamorphosing at this time.
We believe that this is the first published report of freshwater mussels completing their parasitic life cycle in an enclosure under "natural" conditions. If we must salvage mussels by removing them to hatcheries, these results suggest that we may be able to maintain reproducing populations where hosts are known, rather than simply holding individual mussels for an uncertain future. We plan to continue these studies for as long as possible. This project is a cooperative effort between the Ohio Division of Wildlife, the Ohio State University, and the Ohio River Mussel Mitigation Trust Fund.
Jennifer Szymanski
U.S. Fish and Wildlife Service
620 South Walker Street
Bloomington, IN 47403
(812)334-4261.204
The U.S. Fish and Wildlife Service (FWS) is soliciting data for a rangewide status assessment for Leptodea leptodon. To date the following information is lacking: historic and current status information for Mulberry, Saline, and Casatot rivers and Frog Bayou; existing threats to these waterbodies; and historic and current records for the St. Lawrence drainage. Although this information is critical, any data on the distribution and status of L. leptodon would be helpful.
Research and conservation plan on Unio elongatulus aleroni
Cristian R. Altaba
Institut d'Estudis Avancats de les Illes Balears (CSIC-UB)
Ctra. de Valldemossa, Km 7.5
07071 Palma de Mallorca (Illes Balears, Spain)
phone: (34) - 71- 41 98 32
fax- (34) (71) 17 32 48
e-mail: ieacra4@ps.uib.es
The genus Unio includes several distinctive taxonomic entities in the Mediterranean region. Most often, these have been lumped under the name U. elongatulus. However. it is clear from anatomical, conchological, and distributional data that five geographically isolated taxa are present in the Mediterranean drainages of the Iberian Peninsula. In order to keep the legal protection given by European law to U. elongatulus, I prefer for the rime being to consider them 'subspecies."
Unio e. aleroni was described from French Catalonia, although it lived on the mountain streams of the Eastern Pyrenees at both sides of the Spanish-French border. In the last 20 years virtually all populations became extinct as a consequence of increased pollution and hydraulic works. Three years ago, a living population, possibly the last surviving one, was found. A special recovery plan was then started for this taxon
The studied population consists of ca. 5000 mussels, and is restricted to the lower five Km of the Ser river, a tributary of the Fluvia. This part of the Ser valley is narrow, totally forested, and with no settlements. Its fish fauna is considered one of the best preserved in Spain. Although it benefits from no protection status, it is adjacent to the Garrotxa Volcanic Zone Natural Park. However, urban areas and pig farms further upstream are responsible for the dramatic lowering of water quality observed in the last two years. The impact of wastewater is the main factor causing the decline of this population: its age structure shows that there has been no recruitment in the last four or five years.
In order to ensure the survival of Unio e. aleroni, a captive population was established at the Park's headquarters. Infection of fish hosts was successful, and this summer large numbers of juveniles were recovered. The conservation plan to be carried during the next five years involves further study of the wild population, large-scale infection of fish hosts, and artificial propagation to restored habitats. All freshwater mussels are now protected by law in Catalonia, the Ser valley is proposed as a nature reserve, and acceptable wastewater management is expected to be operational 1n the next few months. We are now planning to extend these activities to other endangered unionoids, such as Margaritifera auricularia
New record of Pleurobema clava in Middle Island Creek drainage, West Virginia
Janet L. Clayton and Craig Stihler
WVDNR
PO Box 67
Elkins, WV 26241
304-637-0245
Only one record of Pleurobema clava had previously been recorded for Middle Island Creek north of West Union, West Virginia. The record was reported by Taylor and Spurlock in 1980 but did not indicate if it was alive or relic. In September and October 1995, 5 live individuals of Pleurobema clava (range 66.4 to 85.4 mm) were found in Meathouse Fork of Middle Island Creek, upstream of Smithburg. Meathouse Fork and Buckeye Creek join to form Middle Island Creek. While surveying 16 additional sites in 1994 and 1995 between Smithburg and the mouth, no additional P. clava were found. This indicates the importance of surveying upstream portions of a drainage before determining this species is not present.
A Qualitative Unionid Mussel Survey of the Blue River, Indiana
Bernard E. Sietmanl, Mary A. Furman1, and F.
Allen Pursell2
1Ecological Specialists, Inc., 114 Algana Ct., St. Peters,
MO 63376 (314-447-5355)
2The Nature Conservancy, P.O. Box 5, Corydon, IN 47112
(812-738-2087)
The Blue River drainage is considered to be one the most significant natural areas in southern Indiana. As a result, The Nature Conservancy funded a survey to determine the current status of unionids in this drainage.
From 18 - 24 September 1995, we searched for unionids at 80 sites along a 91 km section of the Blue River main stem between Fredricksburg and Leavenworth, IN. Snorkeling and wading were the primary methods of collecting.
We found evidence of 35 species including 3 species not previously recorded, however, only 20 of these species were represented by live animals. Weilbaker et al. (Proc. Ind. Acad. Sci. 94:687-691, 1985) and Baker and Forsyth (unpubl. report) found 8 additional species, bringing the total to 43. Amblema plicata, Cyclonaias tuberculata, Elliptio dilatata, Lampsilis cardium, Lampsilis siliquoidea, and Tritogonia verrucosa were the most common species, comprising 67% of the live individuals collected. These species were also the most widely distributed, occurring at most of the sample sites. Although previously reported, we found no specimens of the federally endangered Pleurobema rubrum or Obovaria retusa, and we found only extremely weathered shells of Pleurobema clava.
At least one live mussel was found at 64% of the sites, but 60% of the 620 live individuals were collected from only 8 sites, indicating a patchy distribution. At sites where live mussels were collected, the mean number of live species was 3 (range 1 - 9), whereas the mean number of live and dead species combined was 9 (range 3 - 21).
These data suggest that a significant portion of the Blue River's historic unionid fauna has been lost, as is the case with many rivers in the Ohio River drainage.
Charles Lydeard and Kevin J. Roe
University of Alabama Department of Biological Sciences
Box 870344
Tuscaloosa, AL. 35487
205-348-1792 (fax:1786)
E-mail: clydeard@biology.as.ua.edu, kroe3@ualvm.ua.edu
We are continuing with our research on systematics, conservation and evolution of unionids. One of us (CL) has submitted an article in collaboration with Dr. Margaret Mulvey (Savannah River Ecology Lab, Drawer E, Aiken, S.C. 29802) and Dr. George Davis (Academy of Natural Sciences of Philadelphia) to the Journal of the Royal Society of London on generic level relationships of North American unionids based on the 16S rRNA, and another article on the conservation genetics of two unionid genera (Amblema and Megalonaias) also co-authored with Dr. Mulvey and others is in preparation.
One of us (KJR) has begun generating DNA sequence data for an examination of the systematic relationships within the genus Potamilus. In addition KJR has completed a summer study and identified the fish host of the threatened inflated heelsplitter (Potamilus inflatus) as the freshwater drum (Aplodinotus grunniens). This finding confirms suspicions that the genus Potamilus parasitizes A. grunniens almost exclusively. This fact has implications for the recovery of this species, which is restricted to several populations in the Black Warrior River in Alabama, and the Amite River in Louisiana.
Karen Moore
TNC-Clinch Valley Bioreserve
102 S. Court Street
Abingdon, Virginia 24210
The Clinch Valley Bioreserve office of The Nature Conservancy is conducting a muskrat midden monitoring program at Pendleton Island preserve on the Clinch River in Virginia. The monitoring program is designed to determine if muskrat predation is a serious threat to mussels at Pendleton Island. With the help of TNC volunteers, we are collecting middens every two to four weeks between June and October along the banks of the entire island. Significant middens (middens with eight or more native shells) arc mapped, and any observed muskrat lodges along the banks are mapped. All mussel shells are counted and sorted and the native shells are sent to Dr. Dick Neves at Virginia Tech for identification and size information.
We will be conducting a muskrat census at the island with help from Virginia Tech's Wildlife Biologist Dr. Jim Parkhurst. We will combine baseline data on local muskrat population with midden data and evaluate to determine next steps. We plan to continue monitoring during 1996.
Data from both monitoring seasons will be compiled and interpreted by early 1996.
Author: Madeleine Lyttle
Address: Lake Champlain Fish and Wildlife Resources Office
11 Lincoln Street
Essex Junction, Vermont 05452
Phone Number: (802) 951-6313
ISSUE: The Lake Champlain Fish and Wildlife Resources Office is conducting an assessment of the ecological impacts of Bayer 73 (5% granular) used in lamprey control treatments on mussel and snail populations and participating in a lake-wide survey of mussels and snails. Previous studies concluded that pelecypoda (mussels) and gastropoda (snails) did not recover to pre-treatment numbers one year after the initial lampricide treatments (1990). Concern over the potential loss of mussel and snail species on deltas treated with Bayer 73 has prompted this study.
STATUS:
The Lake Champlain Fish and Wildlife Resources Office, in cooperation with the Vermont Department of Environmental Conservation and the Lake Champlain Fish and Wildlife Management Cooperative has collected data to assess mussel and snail abundances and population structures on the Ausable and Little Ausable Deltas.
The occurrence of the species of mussels and snails found on the two deltas will be qualitatively assessed at sites throughout the lake. This project will provide information on the potential lakewide impacts to mussels and snails by repeated treatments of selected deltas with Bayer 73.
New England Interstate Water Pollution Control Commission (NEIWPCC) approved the work plan on June 26, 1995. Christopher Buerkett was hired as a full time NEIWPCC employee, stationed at LCFWRO under the supervision of Madeleine Lyttle, Principal Investigator.
U.S. Fish and Wildlife divers from the Ohio River Islands NWR completed mussel surveys on the Ausable and Little Ausable Delta areas during July 10-14, 1995. Vermont Department of Environmental Conservation assisted with on-site mussel identification and aging.
An interim report is due December 31, 1995. It will compare data from previous studies with the data collected in 1995.
A GIS map of the lakewide locations of targeted mussel and snail species and a GIS map and literature review of waterfowl usage will be included in this report.
A final report developing the draft and incorporating all reasonable comments of representatives of the New York Natural Heritage Group, staff from the Adirondack Park Agency, and the Fisheries and Wildlife Working Groups is due March 3, 1996.
NOTE: The following is not a complete list of all the conference abstracts. Only those abstracts that addressed freshwater mussels are included here.
Abstracts
edited by
Angel Guerra, Emilio Rolan, and Francisco Rocha
Published on behalf of Unitas Malacologica by the Istituto
de Investigaciones Marinas (CSIC, Vigo), Spain. August 1995.
Printed by FEITO, S.L.
Hernan Cortes, 13-15 (Int.), 36203 Vigo, Spain.
Deposito Legal: Vg. -556 - 95
ISBN: 84/606/2602/4
CONSERVATION OF NORTH AMERICA'S FRESHWATER MUSSEL FAUNA (UNIONIDAE) AND THE THREAT POSED BY THE EXOTIC ZEBRA MUSSEL (Dreissena polymorpha)
Richard J. Neves
National Biological Service, Department of Fisheries and Wildlife Sciences, Virginia Tech, Blacksburg, Virginia 24061-0231, USA.
The Unionid fauna of North America included 297 species and
subspecies, distributed primarily in the Mississippi River Basin and
Gulf Coast drainages of the southeastern United States. Roughly 213
taxa are considered to be endangered, threatened, or the special
concern on the continent, and less than 25% of the taxa are
considered stable at this time. The zebra mussel (Dreissena
polymorpha) likely entered the Great Lakes in 1986, and first
appeared in Lake St. Clair in 1988. Since its introduction, this
species has spread rapidly and practically eliminated the native
unionids from Lake St. Clair portion of take Lake, the Detroit River,
and other localized water bodies in the region. Zebra mussels passed
from Lake Michigan to the Illinois River in 1991, and now infest the
Ohio, Mississippi, Missouri, Tennessee, Cumberland, Tombigbee,
Hudson, and numerous other mainstem rivers in the eastern and central
United States. Populations fluctuate widely in density, achieving
maximum densities of more than 50,000/m2 in the Illinois
River in 1993, but declining to less than 10,000/m2 in
1994.
To protect native unionids at greatest risk to the zebra mussel
invasion, the feasibility of using ponds as refugia for riverine
species is being tested in Virginia. Mussels collected from the
Tennessee and Cumberland rivers were cleaned and quarantined for 1
month, and distributed to ponds for long-term monitoring. Fifteen
species of unionids are being held in plastic-screen cages with
flotation collars, and in various racks and pocket nets to monitor
survival. After one year, mean survival was 72% with significant
differences among species. Elliptio spp. exhibited the highest
survival rate (85%), whereas Ellipsaria lineolata and
Lampsilis ovata had the lowest survival (14-15%). Unionids
maintained at the lower end of a trout hatchery experienced high
mortality, presumably due to low dissolved oxygen or elevated ammonia
levels from the decomposition of pelleted feed. Because many
populations of federally protected unionids will eventually be
colonized by zebra mussels, a geographic network of refugia is being
considered to prevent a spasm of extinctions in the United States
unequaled in modern times.
REPRODUCTIVE ECOLOGY OF FRESHWATER MUSSELS (BIVALVIA: UNIONOIDA): SHELL VOLUME AND WEIGHT
William H. Heard and M. Bowie Kotrla
Department of Biological Science Flonda State University Tallahassee, Florida 32306-2043, U.S.A.
Freshwater mussels brood embryos and subsequent larvae in all four (tetrageny) or only the outer two (ectobranchy) or only the inner two demibranchs (endobranchy) for about one month (tachytixis) or 8-12 months (bradytixis) before, in most species, the mature larvae (glochidia, lasidia, or haustoria) are discharged to undertake a two- to fourweek parasitic existence on the gills or fins of fishes or a few other aquatic vertebrates. Smaller individuals (i.e., younger or environmentally stunted animals, or different species) have smaller gonads that produce fewer gametes than do larger individuals. Moreover, smaller females house smaller broods in smaller marsupial demibranchs than do larger females.
Marsupial demibranchs undergo at least a five-fold increase in width upon becoming gravid, which observation suggests that females require and thus display a greater shell width (directly measured with calipers) or convexity (estimated by the volume of water contained between the two valves) than do males of the same size (shell length or height), especially in tetragenous species. In addition, if, as is claimed by developmental biologists, more energy is required to produce eggs than to produce spermatozoa, one might expect that the shells of females weigh less than do shells of conspecific males of the same size (length, height, or width).
However, none of the animals from the 31 populations of 15 tetragenous, ectobranchous, tachytictic, and bradytictic species showed a statistically significant sexually dimorphic difference in shell width or convexity, even in Unionidae: Lampsilinae with sexually dimorphic shape. And, only the tetragenous, tachytictic "Fusconaia" succissa had a statistically significant sexual difference in shell weight.
Studies on production, biomass, and energetics of unionoids should also compare conspecific males and females, especially in conjunction with the gametogenic/vitellogenic cycles because males and females do not always undergo the corresponding phase simultaneously.
NOTE: Statistical tests used include: stepwise discriminant function analyses and stepwise multiple regressions
TESTING HYPOTHESES OF DISPERSAL AND GENE FLOW IN EUROPEAN UNIONIDAE
Karl-Otto Nagel
Gebirgstra§e 23 D. 79426 Buggingen, Germany.
Recent works have helped to clarify the general systematics of European Unionoidea by a multidisciplinary approach integrating anatomical and morphological studies with population genetics (Nagel et al., in press). While basic questions about the nature and number of species were settled at least for Western and Central Europe, the inter- and infraspecific relationships still offer some problems. For instance, the status of the two species Unio pictorum (L. 1758) and U. mancus (Lamarck 1819) (= elongatulus (C. Pfeiffer 1825)) as well as of the South European members of the genus Anodonta Lamarck 1799 is not yet clear. Furthermore, the extent to which species are differentiated on a subspecific level is under debate for most of the European unionids. I will address these problems by looking at the levels of genetic differentiation among groups of populations using gene flow statistics (Porter, 1990; Weir, 1990). On a local scale, I will also use this method to evaluate possible genetic effects of man-made habitat fragmentation. Besides the identification of taxonomic units their geographic distribution is a problem in itself. There are different opinions about the relative roles of geological and biological events or human activities that would explain the actual distribution of unionids. It seems, however, that hydrogeographic situations and landscape development in the past are the most important determinants (Ehrmann, 1950; Modell. 1951, 1964). Genetic distances between populations now can be used to evaluate different hypotheses of common history and dispersal pathways (Arter. 1990). For this purpose I will confront the patterns of genetic distances to physical distances derived from geographic connectivity matrices. These mataces Will for instance depict various periods in the development of river systems in Western and Central Europe. In this case the degree of matrix correspondence will be used to test the explanatory power of the underlying paleohydrologic assumptions for the present distribution of unionid taxa.
Literature cited
Arter, H.E. 1990. Spatial relationship and gene ftow paths between populations of the alpine snail Arianta arbustorum (Pulmonata: Helicidae). Evolution 44: 966-980.
Modell. H. 1951. Die Najaden Vorderasiens. Rev. Fac. Sci. Univ. Istanbul, Ser. B, 16: 351-366.
Modell, H. 1964. Das naturliche System der Najaden. 3. Arch, Molluskenk, 93: 71-126.
Nagel, K.-0. Badino, G. & Celebrano. G. Systematics of European naiades: a review and some new aspects. Malacol. Rev., in press.
Porter. A.H. 1990. Testing nominal species boundaries using gene flow statistics: the taxonomy of two hybridizing admiral butterflies (Limenitis: Nymphalidae). Syst. Zool. 39: 131-147.
Thienemann, A. 1950. Verbreitungsgeschichte der SuBwassertierwelt Europas. Die Binnengewasser XVIII. Stuttgart, E. Schweizerbart'sche Verlagsbuchhandlung, xvi + 809 pags., 11 pls.
Weir, B.S. 1990. Intraspecific differentiation. Chapter 10: 373 410. In Hillis, D. & Moritz, C. (eds.): Molecular Systematics. Sunderland MA, Sinauer.
MODERN DISTRIBUTION OF FRESHWATER PEARL MUSSEL Margaritifera margaritifera L. IN THE RUSSIA
Victor V. Beletsky, Ekaterina G. Popkovich. Valery V. Ziuganov and Alexey A. Zotin
Institute of Developmental Biology, Vavilov Street 26. Moscow 117808, Russia.
The freshwater pearl mussel Margaritifera margaritifera L. has been entered in the [UCN Invertebrate Red Data Book as a vanishing species. Its number reduced by over 90% during the XX century. Therefore the investigations of modern distribution and number of M. margaritifera are of great importance. We found 8 populations of M. margaritifera in north-west of Russia. Four of them consist of more than I million specimens. The largest population inhabit Varzuga River, Kola peninsula consisting of more than 100 million individuals. The numbers of specimens in other populations are: 1, about 6 million (Keret River, Karelia), 2, about 4 mln (Umba River, Kola peninsula), 3, about 1 mln (Gridina River. Karelia), 4, more then 4,000 (Torma Creek, Kola peninsula), 5, about 3,000 (Olanga River. Karelia), 6, about 1,500 (Nuris River, Karelia), 7, about 300 (Vodopad Creek,. Karelia). The age structure of large populations has been studied. The reasons of extinction and conservation measures are discussed.
THE PUMPING ACTIVITY OF UNIONID MUSSELS FROM THE RIVER THAMES
A.D. Berrie and Barbara J. Boize
Department of Zoology, University of Reading, Whiteknights, Reading, RG6 2AJ. U.K. and
Freshwater Biological Association, River Laboratory, East Stoke, Wareham, BH20 6BB. U.K.*
Anodonta anatina and Unio pictorum were attached to perspex stands and kept in aquaria with water circulated from the river. Water entering the inhalant siphon of individual mussels was measured at intervals throughout the day with a flow meter. Maximum rates were not sustained for long and mean rates were calculated from the data.
Mean pumping rates ranged from 0.1 1 hr-l in small mussels to l.0 l hr-l in large mussels. Pumping rates were directly related to shell length and to ctenidial area.
Mussels rarely pumped water when the water temperature was below 10-oC. This means that there was little pumping for 5 to 6 months of the year .
These results will be combined with data on the population densities and age structures of the mussels in the river to calculate the potential intake of food that could be achieved from the volumes of water filtered.
PHENETIC APPROACH TO THE STUDY OF THE INTRASPECIFIC ORGANISATION OF Unio pictorum (BIVALVIA, UNIONIDAE)
Sergey D. Scherbak
Institute of Hydrobiology, 254210, Kiev, Ukraine.
The intraspecific organisation of mollusks of Unionidae family, the group dominating in the benthic communities has been studied incompletely, while such a studing aspect has become especially actual within the population conception as an unite of exploitation and protection.
The present work was done with the purpose of searching the discret feature system, allowing to establish the horogenetic structure of some species of the family The wide spread mass species Unio pictorum Linneus, 1758 was chosen as a model. The material was collected at the depth of 0.3-1.5 m, on the sandy and sandy silt covered bottom in the lower reaches of the Desna river in summer, 1987. 143 specimens were treated. The value was determined and the full correlative analysis of the main exterior indexs was held. Values distribution of the exterior indexs submits to the normal distribution law. There is no discretancy, the low value of dispersion confirms indirectly the ecological homogeneity of the location.
On the basis of number of shell morphological structures forming on the early stages of the ontogeny, the author points out the three groups of features considered as phenes: 1) "step" between the impresses of the front adductor and retractor of the right and left shell folds, 2) display symmetry of the first feature on the both fold, 3) morph in trees of the front pseudo-cardinal teeth of left and right folds. The left fold S-1 the tooth is rectangular. The surface is fine-serrated, straight, protuberant sometimes. S-2 is of the wrong shape. the surface is undulating, the serration isn't pronounced or market feebly S-3 is the teeth not corresponding to the description of S-1 and S-2. The right fold. D-1 is plastic, rounded triangle, the surface is fine-serrated. D-2 has the trapeziform shape, divided by the depression into 2 (not obligatorily equal) parts. D-3 is the teeth not corresponding to the description of D-1 and D-2. U. pictorum local population of the lower reaches of the Desna river following phenocomplex characterise: S-1-63%; S-2-8%; S-3-29%; D-1-7%; D-2-16%; D-3-77%; "step", 6%; symmetry of "step"-92%. No discrepancy in distribution of the values of exterior indexs doesn't allow to mark out, the intraspecific classification of any rank on ther base. The studied phenocomplex defines the specific intraspecific classification of U. pictorum. The additional research of the marked phenes arc necessary to make a conclusion the hereditary character. Based on 118 bibliographical sources (after critical revision of their content) and taking into account a lot of unpublished information, the distribution of each species in Greece was mapped and ecological remarks added whenever necessary. The most studied zones are the infralittoral and circalittoral, while few published information exists on the mediolittoral and bathyal zones. From data collected up to December 1994, it was seen that the total number of species known today amounts to 301 in comparison to 190 (known at the end of 1900) and 275 (known in 1990).
Regarding the distribution of bivalvia in geographical unities, it was found that the Aegean presents the greatest variety (273 species) in relation to the Ionian (196 species), Sea of Kythira (83) and Libyan Sea (50). However, the variety encountered at each area, can be attributed to the plethora of the bibliographical sources referring to the area, rather than to differentiation between areas.
Conclusively, when considering the ecological preferences and the bathymetric range of the species occurrence in combination with the fact that the number of species constantly increases with new studies in either unexplored bathymetric zones or overlooked geographical areas, it is believed that the eastern Mediterranean is as rich as the western Mediterranean.
SYMBIOSIS OF FRESHWATER PEARL MUSSELS AND ATLANTIC SALMON
Valery V. Ziuganov and Alexey A. Zotin
Institute of Developmental Biology, Vavilov Street 26, Moscow 117808, Russia
The symbiotic interrelations of freshwater pearl mussel Margaritifera margaritifera L. with Atlantic salmon Salmo salar L. are reported. Pearl mussel larvae (glochidia) develop in the gills of salmon and adult mussels effectively filter river water as well as improve bottom of the river. This creates optimal conditions for the reproduction of salmons. In this case it seems to be a matter of a principally new form of symbiosis with time-dissociated, mutually beneficial influence of the two species. Indeed, if the parasitising glochidia are taken as a starting point, it is only the fish that at this time can be said to be of use to glochidia that find the optimal osmotic mediums in their tissues, feed and disperse at its expense. Only several years later the grown up young mussel will pay their dept by filtering water and ensuring better survival of young salmons. Thus pearl mussels and salmonid fishes together form a new ecological system, in which each of the species finds optimal conditions for its existence.
DISTRIBUTIONAL DATA OF THE UNIONIDS IN BELGIUM (MOLLUSCA, BIVALVIA, UNIONIDAE)
E. Nijs and J. L. Van Goethem
Royal Belgian Institute of Natural Sciences, Malacology section, Vautierstreat 29, B-1040 Brussels, Belgium.
Six species of Unionidae belonging to three genera are currently fond in Belgium. The shells are more or less elongate, with a high variability in some species; adult shells always exceed 4 cm. in length. Diagnostic features are shape, umbonal sculpture, hinge characters and pattern of muscle scars. Unionids are dioecious and ovoviviparous; the number of eggs may be in the region of 500,000. The calcareously shelled glochidium larvae are first being brooded in the gills, which act as brood-pouches; later on, they are released as temporary parasites of fishes. The species inhabit slow rivers, canal, lowland lakes, reservoirs and ponds. For each species. a distribution map based on the UTM-grid with 10x10 km. squares is provided. Records pre-1950 and records 1950 onwards are marked by different symbols. At present 792 records of Unionidae pre-1950 and 294 records 1950 onwards are available. A dramatic decline of Unionid species in Belgium is not necessarily the first hypothesis. It rather seems that freshwater bivalve collecting in Belgium was more intensive and widespread before 1950. It is suggested to take advantage of the potential offered by large freshwater bivalves and develops their use for nature conservation issues, especially in the field of site protection.
THE SPECIES PROBLEM WITHIN MARGAR1TIFERIDAE FAMILY IN THE FAR EAST
Alexey A. Zotin and Valery V. Zioganov
Institute of Developmental Biology, Vavilov Street 26, Moscow 117808, Russia.
Within the family Margaritiferidae (Henderson) (freshwater pearl mussels) the species problems exist only for genus Margaritifera (Schumacher). Previously there was described 3 species of this genus from Sakhalin Island and Kuril Islands (Russia) (Zatravkin & Bogatov, 1987): Margaritifera laevis (Haas), M. kurilensis (Zatravkin & Starobogatov), M. shigini (Zatravkin & Bogatov). These species are recognised by shell dimensions: height to length ratio and convexity to length ratio. Our investigations indicate that these ratios are highly variable and can hardly serve as discriminating characters. Values of size ratios in populations described as different species overlap. Hence there are no reasons to recognise different freshwater pearl mussel populations from Sakhalin Island and Kuril Islands as different species. It is very likely that the rivers in this region are inhabited by only one species, Margaritifera laevis (Haas).
Zatravkin M.N. & Bogatov V.V., 1987. Large bivalve freshwater and brackish water molluscs of the Far East of the USSR. Vladivostok, lzd. AN SSSR,154 pages.
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