Recruitment in a Freshwater Unionid (Mollusca : Bivalvia) Community Downstream of Cave Run Lake in the Licking River, Kentucky

7 Pages·1999·3.1 MB·English

by  S E Mcmurray

Recruitment in a freshwater unionid (Mollusca: Bivalvia) community
downstream of Cave Run Lake in the Licking River, Kentucky
Stephen E. McMurray1 Guenter A. Schuster, and Barbara A. Ramey
,
DepartmentofBiological Sciences, Eastern Kentucky University, Richmond, Kentucky 40475 U. S. A.
Abstract: Unionids,fish,andglochidiawerecollectedtodeterminewhyrecruitmenthadceasedorhadbeendramaticallydecreasedinaspecioseunion-
idcommunityintheLickingRiveratMooresFerry,Kentucky, 35.4kmdownstreamofCaveRunLake. Onlysixunionidglochidiawerecollectedwithdrift
nets,andonlysix fishcollectedhadinfestationsofglochidia. Asmallpercentage(10.1%)oftheunionidsobservedhadtheirgillsmodifiedasmarsupia. An
analysisofwatertemperatureanddischargeindicatednosignificantdifferenceinaveragemonthlydischarge(p>0.05)andasignificantdecreaseintemper-
ature (p < 0.05) between pre- and post-impoundment periods. Average monthly discharge and temperature may not be as biologically important as the
spikesofdischargeandcorrespondingsuddendecreasesintemperaturethatarecausedbyreleasesofhypolimnionicwaterfromthereservoir.
Key Words: Unionidae,recruitment,gametogenesis,impoundments, Kentucky
North America has the richest unionoidean (mussel) Chandler, 1996). One of the most severe and perplexing
(Bivalvia: Unionidae) fauna in the world. This fauna has problems facing freshwater mussels is the documented loss
disproportionately more endangered, threatened, and spe- of recent recruitment (reproduction) in unionid communi-
cial concern taxa than all the groups of terrestrial organ- ties that were previously thought to be healthy.
isms. Only 70 of the 297 taxa known from the United Recent research hypothesized that recruitment had
States are considered stable (Williams et al, 1993). Ofthe ceased or had been dramatically decreased in a diverse
freshwater unionid taxa recognized from the United States unionid community in the Licking River at Moores Ferry,
and Canada, 35% (103 taxa) are known to occur, or have Kentucky (Kane, 1990; Smathers, 1990). The present study
occurred in Kentucky, which ranks this state third in faunal was an attempt to determine if recruitment had ceased or
richness behind Tennessee and Alabama (Cicerello et al, had been decreased in this diverse unionid community, and
1991). Human activities in the Commonwealth have severe- ifso, to determine where in the life cycle reproduction was
ly impacted unionid populations during the last 200 years, breaking down. This study was also an attempt to deter-
making this group oforganisms the most endangered in the mine what effects, if any, the hypolimnionic discharges
state (Cicerello etal, 1991). from Cave Run Lake were having on the mussels in the bed
Freshwater mussels are impacted by anthropogenic at Moores Ferry. It was hypothesized that the loss of
factors such as the additions oftoxic substances into aquat- recruitment in this bed was either directly or indirectly the
ic systems, sedimentation, habitat destruction, loss of their result ofthe dam, located approximately 35.4 km upstream,
host fish(es), introduced species, and commercial harvest- which has altered both the natural temperature and flow
ing (van der Schalie and van der Schalie, 1950; Fuller, regimes ofthe river.
1980; Bogan, 1993; Williams et al, 1993). The construc-
tion of dams along the course of several rivers in North
METHODOLOGY
America has resulted not only in the loss of taxa, but also
of whole beds (e. g., van der Schalie and van der Schalie, STUDY AREA
1950; Bates, 1962; Miller et al, 1984; Miller et al, 1992; The Licking River is a sixth order tributary to the
Williams et al, 1992; Layzer et al, 1993; Sickel and Ohio River, originating on the Unglaciated Allegheny
Plateau in the Appalachian Province of eastern Kentucky.
'PresentAddress: Kentucky Division ofWater, WaterQuality Branch, 14 The river flows through an extremely variable topography
ReillyRoad,Frankfort, Kentucky 40601 U.S.A. in a northwesterly direction through the Blue Grass region
AmericanMalacologicalBulletin,Vol. 15(1)(1999):57-63
57
58 AMER. MALAC. BULL. 15(1) (1999)
ofthe Commonwealth for 496 km until its confluence with snorkeling, or by wading with the use of water scopes.
the Ohio River near Covington, Kentucky, at Ohio River After identification, the shell ofeach unionid was carefully
km 757.2 (Harker et al, 1979, Hannan, et al., 1982, Burr opened with a small screwdriver, and the gills examined for
and Warren, 1986). This drainage encompasses approxi- signs of gravidity. The species name was recorded and
mately 10% of the Commonwealth (9601 km2) and covers notes were made on the condition of the gills. Except for
all oraportion of21 counties (Harkeretal, 1979). individuals of two target species retained for histological
In 1974 the Licking River was impounded to form examination, all unionids were returned to the river. Three
Cave Run Lake, a warm oligotrophic lake (Clinger, 1974). to five individuals of the two most common species in the
The lake has a surface area of3347 ha that inundates 61 km bed at Moores Ferry (Smathers, 1990), Actinonaias liga-
ofthe mainstem and the lower reaches ofseveral small trib- mentina (Lamarck, 1819) and Elliptic/ dilatata (Rafinesque,
utaries (Burr and Warren, 1986). The Licking River 1820), were chosen for histological examination from each
drainage has a speciose unionid fauna with 53 taxa, over collecting period. These species represented both of the
half of the state's native mussel fauna, historically existing breeding regimes of freshwater mussels, they were both
in the drainage (Cicerello et al, 1991). A recent survey commonly encountered throughout their respective ranges
below the reservoir indicated that 50 taxa still reside in that (Oesch, 1995), and neither had any federal or state protec-
portion ofthe river(Laudermilk, 1993). tion status in Kentucky (Kentucky State Nature Preserves
Moores Ferry, Kentucky, is a ford approximately Commission [KSNPC], 1996).
35.4 km downstream from Cave Run Lake (Fig. 1). The Individuals were prepared for histological examina-
watershed at this site is utilized mainly for agriculture. tion by placing them into a 10% formalin solution, then
Discharge at this site is affected by releases of water from transferring them to 70% ethanol in the laboratory. The
Cave Run Lake, which at times causes drastic water level valves were opened by cutting the adductor muscles and
fluctuations. Substrata consisted mainly of cobble, gravel, portions of the gonadal and gill tissues were removed and
rubble, and some boulders with intermixed sandy areas placed into either 70% ethanol or Bouins fixative. These
(Smathers, 1990). The unionid community at this site had a were then dehydrated through a series of alcohols and
rich assemblage of unionid species, with 35 known present embedded in paraffin (Humason, 1967). Sections were
orhistorical taxa (Smathers, 1990; Laudermilk, 1993). made at a thickness of 10 urn using an American Optical
820 Microtome. Slides were stained with Ehrlich's hema-
SAMPLING AND LABORATORY PROCEDURES toxylin and eosin was used as the counterstain (Humason,
Five collections of glochidia, fish, and unionids 1967). Sections were mounted with Permount. The sections
were made from July through October 1995. High water were then examined under a compound microscope (400-
conditions prevented collections during Spring 1996. For 430X) to determine a sex ratio for both species; to deter-
each collection period a drift net was haphazardly placed in mine if gametogenesis was occurring, and, if so, to try to
the bed to collect glochidia. After one hour, the contents of quantify it; and to determine the contents of the marsupia.
the drift net were removed and preserved in 70% ethanol All drift net, fish, and unionid collections were deposited in
and returned to the laboratory. Drift net collections were the Branley A. Branson Museum of Zoology, Eastern
examined using cross-polarized light microscopy (Johnson, Kentucky University (EKU).
1995), with a portion of the sample being delivered into a Five cell types of spermatogenesis (Garner, 1993)
watch-glass with a gridded bottom. Each square in the grid were used to determine the stage of gametogenesis in
was then systematically searched under cross-polarized males. Stage 1 males were those that had only spermatogo-
light (10-20X) for glochidia, which were counted and nia present in their acini, and Stage 5 males had mature
removed along with any juvenile Corbicula fluminea spermatozoa present. Stages 2, 3, and 4 corresponded
(Miiller, 1774). respectively to sperm morulae, spermatocytes, and sper-
Fish were collected for one hour using a minnow matids being present in the acini. Three cell types ofooge-
seine. All fish retained were initially preserved in a 10% nesis (McMurray, 1997) were used to determine the stage
formalin solution and then transferred to 70% ethanol in the of gametogenesis in female Elliptio dilatata. Stage 1
laboratory for final preservation. Following sorting and females were those with oogonia as the dominant cell type
identification, the fins and scales of each individual were in their alveoli, Stage 2 were those with oocytes dominant,
examined under a dissecting microscope (10-30X) for and Stage 3 were those with mature ovadominant.
attached glochidia. The opercular flaps were removed, and Marsupia were classified according to theircontents
each gill arch was carefully examined under a dissecting as being empty (EM), or containing mature glochidia
microscope for attached glochidia (Bruenderman and (MG), early embryos (EE), or advanced embryos (AE)
Neves, 1993). (Garner, 1993). In the case of known females that did not
Unionids were collected by hand for one hour by have their gill tissues examined, the marsupia were consid-
McMURRAY ETAL. IMPOUNDMENTS AND FRESHWATER MUSSEL RECRUITMENT 59
\
MooresFerry
Fig.1.LocationoftheMooresFerrystudysite. InsetshowsthelocationoftheLickingRiverdrainagein Kentucky.
ered to be empty since sections were made of any gill that Widlak, 1987).
showed signs ofgravidity. Marsupia with mature glochidia Only 11.3% of the 399 fish collected were suitable
were those that had glochidial shells and the single adductor hosts for unionids in the bed (Watters, 1994). Of the fish
muscle visible in the section. collected only six specimens had attached glochidia: one
Temperature and discharge data were obtained from Micropterus punctulatus (Rafinesque, 1819); three Percina
the United Stages Geological Survey (USGS) for the copelandi (Jordan, 1877); one P. evides (Jordan and
Licking River gauging station at Farmers, Kentucky, which Copeland, 1877); and one P. oxyrhyncha (Hubbs and Raney,
isjust upstream ofMoores Ferry. Data were obtained for a 1939). Even though a small fish may successfully carry sev-
pre-impoundment (1966-1970) and a post-impoundment eral hundred glochidia (Lefevre and Curtis, 1910), low
(1991-1994) period. Daily temperature and discharge data infestation rates appear to be common (Kitchell, 1985;
from the months of May through September for each of Neves and Widlak, 1988; Bruenderman and Neves, 1993;
these years, with the exception of 1994 (May-June), were Weiss and Layzer, 1995). The attachment of glochidia to
analyzed to determine if any correlation existed between their hosts is dependent upon several factors such as infes-
discharge and watertemperature. tations ofhosts by copepod parasites (Wilson, 1916), age of
the host, immunity caused by previous infestations (Parker
etal., 1984), and watertemperature (Matteson, 1948).
RESULTS AND DISCUSSION A total of288 unionids were collected from Moores
Ferry (Table 1). Of these, only 10.1% (29 individuals) had
A total ofonly six unionid glochidia were collected their gills modified as marsupia, indicating an 8.93:1 male
using drift nets, compared to 185 juvenile Corbiculaflu- to female ratio if modified gills are taken to represent
minea. The large number ofjuvenile C.fluminea was large- females. Marsupial condition is probably not a true repre-
ly the result of a single collection of 127 individuals. Drift sentation of the actual male to female ratios, but most
net collections were made between 1000 and 1700 hours unionids are not sexually dimorphic (McMahon, 1991), and
(EST), which corresponds to the period when glochidial the only way to determine the sex of an individual without
densities should have been at their highest (Kitchell, 1985). using histological techniques is to examine the gills for
The high number of C. fluminea present may impactjuve- signs of gravidity. However, it would still be expected that
nile unionids through resource competition (Neves and at least 50% of the individuals collected would have had
60 AMER. MALAC. BULL. 15(1) (1999)
Table 1. Unionids with and without gills modified as marsupia from the alveoli of the ovaries, as was observed in the testes of the
LickingRiveratMooresFerry, Kentucky. males. Most of the E. dilatata were in the second stage of
oogenesis with oocytes dominating the alveoli. One female
With Without
Modified Modified was categorized as unknown because the stage ofoogenesis
Taxa Gills Gills Totals could not be determined due to technical difficulties.
Actinonaiasligamentina(Lamarck, 1819) 20 135 155 Hermaphroditism, which has been reported for both of the
AlasmidontamarginataSay, 1818 0 0 0 target species (van der Schalie, 1970; Jirka and Neves,
Amblemaplicata(Say, 1817) 0 45 45 1992), was observed in one Actinonaias ligamentina indi-
Cyclonaiastuberculata(Rafinesque, 1820) 0 0 0 vidual. Most of the acini in this individual contained male
Elliptic!dilatata(Rafinesque, 1820) 0 18 18 gametes, and those with female gametes seemed to be
Fusconaiaflava(Rafinesque, 1820) 0 2 2
LampsiliscardiumRafinesque, 1820 2 6 8 degenerate. Even though the male to female ratios of the
Lasmigonacomplanata(Barnes, 1823) 0 0 0 target species were not significantly different from 1:1, a
L.costata(Rafinesque, 1820) 0 6 6 majority ofthe females hadempty marsupia(Table 2).
Leptodeafragilis(Rafinesque, 1820) 0 1 1 The post-impoundment water temperatures at
Megalonaiasnervosa(Rafinesque, 1820) 0 9 9
Farmers, Kentucky, which is located between Moores Ferry
ObliquariareflexaRafinesque, 1820 0 0 0
Potamilusalatus(Say, 1817) 1 2 3 and Cave Run Lake, were found to be significantly lower
Ptychobranchusfasciolaris(Rafinesque, 1820) 6 19 25 than pre-impoundment temperatures for the months ofMay
Quadrulametanevra(Rafinesque, 1820) 0 0 0 through July. There was no significant change in water
Q. nodulata(Rafinesque, 1820) 0 0 0 temperature for August, and a significant increase for
Q.pustulosa(Lea, 1831) 0 1 1 September (Table 3). A change in the temperature regime
Q. quadrula(Rafinesque, 1820) 0 7 7
Tritogoniaverrucosa(Rafinesque, 1820) 0 8 8 ofan aquatic system, especially adecrease, can have drastic
effects on freshwater mussels. Water temperature influ-
Totals: 29 259 288 ences the length of the period of development, the time of
fertilization (Matteson, 1948), the release of glochidia
(Yokley, 1972; Jirka and Neves, 1992), the survival of
their gills modified as marsupia if normal reproduction glochidia before they attach to a host (Tedla and Fernando,
were occurring. Histological examination revealed that the 1969), and it is the major environmental factor that regu-
male to female ratios for the two target species were not lates the period of glochidial attachment (Matteson, 1948;
statistically different from 1:1. Both ofthe target species, as Zale and Neves, 1982; Neves and Widlak, 1988).
well as other species of unionids, usually maintain a 1:1 Decreases in water temperature can also result in a
male to female ratio (Jirka and Neves, 1992). decreased production of the crystalline style (Allen, 1921),
Most of the males of the two target species had reduce the motility of adult unionids (Yokley, 1972) and
more than one stage of spermatogenesis present in their influence the growth ofadults (Hruska, 1992).
gonads, but usually the most advanced stage present domi- The average monthly discharge at Farmers,
nated the acini of the testes (Table 2). Spermatids were Kentucky, increased from pre- to post-impoundment for the
observed in most ofthe male Elliptio dilatata collected, but months of June through September and decreased during
all the cell types except spermatozoa were also observed. May, but none of these changes were statistically signifi-
All the cell types except spermatocytes were observed in cant (Table 3). Even though these changes were themselves
male Actinonaias ligamentina, with sperm morulae and not statistically significant, they were directly related to sig-
spermatids the most common. nificant changes in water temperature. The hydrological
All of the female Elliptio dilatata had each of the variability of a river influences the spatial distribution of
three egg cell types present in their ovaries (Table 2). The individuals in a freshwater mussel community (Di Maio
most advanced stage present did not always dominate the and Corkum, 1995), and stream velocity is a major factor
Table2.StagesofgametogenesisandmarsupialcontentsofActinonaiasligamentinaandElliptiodilatata from
theLickingRiveratMooresFerry, Kentucky.Seetextforstageandcontentdescriptions.
StageofSpermatogenesis StageofOogenesis MarsupialContents
Taxa 1 2 3 4 5 1 2 3 UNK EE AE MG EM
Actinonaiasligamentina 1 4 0 4 1 11 2 0 3 12
Elliptiodilatata 1 2 3 7 0 2 4 0 2 1 5
12
Totals: 2 6 3 11 1 2 4 2 2 4 17
.
McMURRAY ETAL. IMPOUNDMENTS AND FRESHWATER MUSSEL RECRUITMENT 61
:
Table3.MeanmonthlywatertemperatureanddischargefortheLickingRiveratFarmers.
Kentucky,duringpre-(1966-1979)andpost-impoundment(1991-1994)periods.
WaterTemperature(°C) Discharge(m-Vs)
Month 1966-79 1991-94 Students-f 1966-79 1991-94 Students-f
May 16.3 13.4 3.0291* 48.1 27.7 0.8716
June 22.1 17.0 3.4908* 5.6 14.7 -1.2913
July 24.5 21.3 2.0554* 4.0 8.3 -1.4505
August 23.0 229 0.1184 7.6 9.0 -0.3339
September 20.7 23.0 -3.1114* 3.4 5.0 -1.0613
Statisticallydifferentata=.05
determining the presence or absence of different species Run Lake during important reproductive periods.
within a freshwater community (Home and Mcintosh, For example, during July 1966, before the comple-
1979). During periods of high discharge the dilution of tion of Cave Run Lake, water temperature averaged 26.4 ±
sperm and glochidia may occur (Miller and Payne, 1988), 0.85°C and the discharge averaged 3.2 ± 3.2 m-Vs (Fig. 2).
and continuous high-turbulence flow can impact adult During July 1991, after the construction of the lake, the
unionids by eroding the periostracum (Milleretal., 1984). average water temperature was 18.5 ± 2.82°C and the aver-
Even though there were no changes in discharge, age discharge was 16.8 ± 17.5 m3/s. There were large
and significant decreases in temperature (p < 0.05) only spikes of discharge during both of these months. During
during the months of May through July, the impacts of July 1966 discharge increased and then returned to normal
these changes were still biologically important. It is seven days later, resulting in only a 3°C decrease in temper-
believed that the average monthly discharge and tempera- ature that did not last long after the increased discharge had
ture may not be as important as the spikes ofdischarge, and subsided. During July 1991 the spike in discharge returned
the corresponding sudden decreases in temperature, that are to normal nine days later, and resulted in a 6.5°C decrease
caused by the releases of hypolimnionic water from Cave in temperature that did not return to its pre-release level
until fourdays later. This single spike ofdischarge impact-
ed the normal water temperature for a period of 13 days.
Sudden, drastic, temperature changes such as these have
been reported to cause the abortion of embryos and
glochidia (Matteson, 1948; Bruenderman and Neves, 1993).
ACKNOWLEDGMENTS
The authors would like to acknowledge the assistance ofC.
Abbruzzese,J. S. Board, M. C. Compton, M. D. Moeykens, A. R. T. Nix,
T. E. Oliver, M. A. Patterson, and D. Vey in the field and laboratory. R.
R. Cicerello (KSNPC)and P. A. Ceas(EKU) assistedwithfishidentifica-
tion. G. T. Watters(OSU) providedhelpful tipsontheuseofcross-polar-
ized light. We would also like tothank D. L. Batch(EKU) forservingon
the primary author's thesis committee. D. L. McClain, Water Resources
Division, USGS, Louisville, provided the temperature and discharge data
for the licking River. Two anonymous reviewers are thanked for their
comments on the manuscript. This research was funded by a grant from
the Kentucky Department ofFish and Wildlife Resources (Project No.
E-2-9).
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