Pink heelsplitter (Potamilus alatus) mussels collected from Kentucky Lake, TN were held at two bottom locations (0.6 m, 2.5 m) and suspended in pocket nets (at depth about 1.0 - 1.5 m) in a pond at the Freshwater Mollusk Conservation Center (FMCC), Virginia Tech, for 1 yr. Survival of mussels after 1 yr was significantly different, with poorest survival (30 %) in the bottom of the deep end; and no difference between the shallow end (83.3 %) and the suspended pocket nets (63.3 %). Survival of mussels was inversely related to water temperature (r = - 0.72); lowest monthly survival occurred in summer, resulting in a significant difference among the three locations with a similar trend after 1 yr. The glycogen reserves of mussels in captivity for 1 yr differed by pond location, higher in mussels at the shallow end than those in suspended pocket nets and at the deep end. Therefore, the shallow end of pond was more suitable for holding mussels long-term, while the suspended pocket nets are an alternative site for holding captive mussels. Additionally, dissolved oxygen was very low at the deep end (1.9 mg/L) in summer, while it was adequate (range from 5.7 - 6.4 mg/L) at the location of suspended pocket nets, and 5.0 mg/L at the shallow end (24.7 °C). Data for 40 specimens indicated that sexual dimorphism in valve shape occurred in P. alatus. Female mussels had a significantly (p < 0.0001) greater ratio of height (H) to length (L) (52.3 %) and width (W) to length (31.8 %) than males (H/L: 48.4 %; W/L: 28.8 %), respectively. The posterior ends were somewhat round to oval in males and bluntly squared or truncated in females. Female mussels were more inflated than males. These morphological differences can be used to distinguish females from males during field collections. The red drum (Sciaenops ocellatus) was identified as a new fish host for P. alatus, as 48 active juveniles were transformed by this species, which is not a natural host. Four glochidia were observed on the fins versus 2,307 on the gills of five red drum. Freshwater drum also was verified as a suitable host fish, but black crappie (Pomoxis nigromaculatus), banded sculpin (Cottus carolinae), yellow perch (Perca flavescens) and nile tilapia (Oreochromis nilotica) did not support transformation of glochidia to juveniles. Survival and growth of propagated juveniles of P. alatus were assessed regarding the effects of algal diets (Nannochloropsis oculata and Neochloris oleoabundans) and substrate type (fine sediment and sand). Overall, survival of juveniles after 17 d ranged from 23.8 to 66.8 %, with mean of 48.5 %; however, survival dramatically declined during the next 2 wk period to only 5.8 % (range of 1.8 to 7.8 %). Survival rate of juveniles was significantly different (p = 0.027) between substrates, but not in diets (p = 0.520), with the lowest survival rate of 23.8 % in sand substrate and fed N. oculata. Juveniles grew faster in fine sediment (23.0 % increase in shell length) than in sand substrates (10.5 % increase) (p = 0.002). Moreover, mean growth rate of juveniles was 4.9 &#956;m/d during the first 2 wk, but decreased to 0.2 &#956;m/d in the remaining 2 wk. Therefore, fine sediments seemed more appropriate for juvenile culture compared to sands. Both species of algae, N. oculata and N. oleoabundans, can be used to feed juveniles in the laboratory. Adult pink heelsplitters were used to study feasibility of pearl production by using two surgical implants (non-nucleated implant = NNI, and image pearl implant = IPI) in two ponds of different nutrient levels (FMCC pond and Duck pond). NNI and IPI pearls with purple or purplish luster were successfully produced in P. alatus. Pearl weight was not significantly different (p = 0.562) between two ponds. No differences in monthly survival rates of mussels were observed in either pond (p = 0.051), or among mussels with surgical implants and the no-surgery control mussels (p = 0.881). Consequently, P. alatus can be considered a potential species for producing purple pearls in pearl culture. Additionally, mussels in the Duck pond had higher (p < 0.0001) glycogen levels, similar to those in wild collected mussels, than those in the FMCC pond, indicating that this pond environment may be more suited for holding implanted mussels in captivity. / Master of Science

The federally endangered tan riffleshell (<I>Epioblasma florentina walkeri</I>) is restricted to only one known reproducing population, in Indian Creek, Tazewell County, Virginia. Attempts to recover this species by augmenting relic populations throughout its historic range are aided through knowledge of its population biology and requirements in culture environments. Infestations of host fish (fantail darters, <I>Etheostoma flabellare</I>), obtained from four river drainages, with tan riffleshell glochidia showed that significantly more juveniles transformed per fish from infestations on fantail darters from Indian Creek (mean = 59.22 ± 10.01) than on fantail darters from the Roanoke River (mean = 9.45 ± 10.64) (p = 0.024). Number of juveniles from fantail darters collected from Elk Garden and the South Fork Holston River were not significantly different from those of either Indian Creek fish or Roanoke River fish. These results support the hypothesis that mussel-host fish relationships are likely mediated by fish immune responses. Furthermore, this study suggests that this compatibility has resulted from coadaptation between the tan riffleshell and fantail darter populations in Indian Creek. The tan riffleshell population in Indian Creek was estimated to be 1078 adults (95% CI= 760 - 1853), using Schumacher's modification of Schnabel's maximum likelihood estimator. The sex ratio and size distribution of males and females were approximately equal. Specimen ages, determined from thin-sections of shells, showed that mussels aged by external annuli on shells likely underestimates the true ages of individuals. Appropriate culture conditions for this species were examined using juveniles of the wavyrayed lampmussel (<I>Lampsilis fasciola</I>) as a surrogate. In the first experiment, juvenile growth and survival was compared between four substratum types (fine sediment, < 120μm; fine sand, 500 μm-800 μm; coarse sand, 1000 μm-1400 μm; and mixed sediment, < 1400 μm) and two light treatments in open versus covered recirculating troughs (2.8 m). Juveniles in fine sediment substratum and covered troughs fared poorest, with 7% survival and growth to only 0.86 mm in length after 16 wk. Juveniles in mixed sediment and open troughs fared best, with 26% survival and growth to 1.09 mm after 16 wk. Additionally, juveniles in fine sand in covered troughs had significantly higher survival (23.1%) than juveniles in fine sediment (p = 0.04), and juveniles in fine sand survived consistently better between light treatments than in the other substrata. There were no significant differences among the other treatments. A second experiment was performed to determine whether juveniles were responding directly to the presence of light or whether only the increased autochthonous production improved growth and survival. One-half of each of three 2.8 m troughs were covered with 50% shade cloth, while the other sides were left open to ambient light. Additionally, the best and worst sediments from the first experiment (fine sand and fine sediment) were used again to verify the results from the previous experiment. In this case, juveniles in both sides of the troughs grew equally well, but juveniles in the open sides had significantly poorer survival (open mean: 1.78%, sd = 5.01; covered mean: 7.4%, sd = 5.01) (p = 0.046). Fine sediment yielded significantly higher growth of juveniles than fine sand (p = 0.009), with shell lengths of 2.63 mm (sd = 0.075) in fine sediment and 1.94 mm (sd = 0.102) in fine sand. The differences in survival and growth between the two experiments were attributed to differential numbers of chironomids and platyhelminths, which are predators of young juveniles. Additionally, the fine sediment was more tightly packed in the first experiment than in the second, which may have restricted movement and subsequently reduced survival. Light alone likely did not affect juvenile survival and growth; rather, it was seemingly the greater abundance of aufwuchs available as food. This hypothesis was corroborated by a juvenile behavior experiment, which showed that juveniles did not act differently when in tanks not exposed to light versus those open to ambient light. / Master of Science