Browsing by Author "Gatenby, Catherine M."

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    An Assessment of Suitable Feed Quantity and Quality for Riffleshell Mussels (Epioblasma spp.) Held in Captivity
    Bush, Amy L. (Virginia Tech, 2008-01-30)
    Optimum feed ration was determined for riffleshell mussels (Epioblasma spp.) held in captivity. Mussels were fed one of four rations (0.49, 0.72, 1.28, or 1.73 mg dry wt/l) of algae Neochloris oleoabundans for 2-h trials in spring, summer, fall, and winter. The test ration resulting in the most feed absorbed per hour (net absorption rate, mg/h) was determined to be the optimum feed ration. Mussels absorbed the greatest amount of food when fed the highest ration. Suggested feed rations for captive adult Epioblasma species are 1.73 mg/l when held at moderate temperatures (i.e., 15-19C), and 1.28 mg/l when held at cool temperatures (i.e., near 11C). Seasonal utilization of protein by oyster mussel (E. capsaeformis) and rainbow mussel (V. iris) was examined with O:N ratios. Ratios were determined for mussels fed a low or high-protein diet (0.11, or 0.31 mg protein/mg dry algal feed), and for mussels held in a hatchery or in the Clinch River, in spring, summer, and winter. Significant differences in O:N ratios were not observed between mussels fed a low or high-protein diet (p > 0.05). The O:N ratios were significantly highest in spring and summer, and lowest in winter (p < 0.05). Mussels primarily utilized protein in spring and summer, and conserved protein in winter. A diet high in energy was suggested in spring and summer, and a diet high in protein was suggested in winter.
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    Development of a diet for rearing juvenile freshwater mussels
    Gatenby, Catherine M. (Virginia Tech, 1994-04-15)
    Over 100 species of freshwater mussels (Unionidae) are endangered or threatened in the United States, and another dozen species support a declining commercial harvest of shells for the cultured pearl industry in Asia. Because of these Significant declines in abundance, a study was undertaken to develop a diet for rearing juvenile mussels, with the goal of long-term propagation of rare species. Three trials were conducted to test various tri-algal and commercial diets and to determine the influence of silt in survival and growth of the rainbow mussel (Villosa iris) and giant floater (Pyganodon grandis). After 45 days post-metamorphosis, juvenile V. iris fed algae with silt exhibited a two-fold increase in shell length (532 μm), and 63.5% survival. Juvenile P. grandis exhibited similar results at 45 days post-metamorphosis. In comparison, all juvenile mussels fed algae without the presence of silt exhibited no increase in shell length after 45 days post-metamorphosis. However, survival varied between species. Survival after 45 days was 5.0% for V. iris and 43.3% for P. grandis. P. grandis is probably more tolerant of a variety of environmental conditions. Analysis of covariance showed that growth rate over time (120 days) of P. grandis was significantly greater than that of V. iris. Shell lengths of P. grandis juveniles fed algae in the substrates kaolin, sterilized silt, sterilized silt plus Aqua Bacta-Aid, and bacteria-colonized silt were Similar, indicating that bacteria were not essential to juvenile digestion or nutrition. Shell lengths of V. iris juveniles fed algae in kaolin or algae in bacteria-colonized silt also were similar after 60 days. Juvenile mussels appear to be pedal-feeding for approximately 120 ± 30 days, depending on the species; hence, silt probably serves as a physical substratum for pedal-feeding mussels to collect food particles. Subsequent tests indicated that growth was significantly correlated with algae high in oils which contain polyunsaturated fatty acids (PUFA). V. iris juveniles fed a tri-algal diet, consisting of Neoehloris oleoabundans~ Phaeodactylum tricornutum, and Bracteacoccus grandis (NPB), with silt substratum showed the best growth over time. Individuals achieved a mean shell length of 1747 μm and had 30.0% survival after 140 days postmetamorphosis. All other tri-algal diets tested enhanced growth over the commonly used green tri-algal mix of Chlorella, Ankistrodesmus, and Chlamydomonas (CAC), and all algae diets enhanced growth over a silt-only diet. Commercial yeast diets did not support growth. After 272 days post-metamorphosis, V. iris fed CAC in silt achieved a maximum shell length of 4520 μm (17-fold increase in length), with a mean length of 2968 μm and approximately 5% survival. After 195 days postmetamorphosis, P. grandis achieved a maximum shell length of 7846 μm (22- fold increase in length), with a mean of 4877 μm and approximately 12% survival. Results of all feeding trials indicate that algae are a suitable food source for rearing early juvenile freshwater mussels. A tri-a1gal diet high in oils resulted in greater growth than all other diets tested. Resident bacteria in riverine sediments were not essential to growth and survival of juvenile mussels. Silt provided some nutritional value, but primarily served as a physical substratum for pedal-feeding juveniles.
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    Development of a suitable diet for endangered juvenile oyster mussels, Epioblasma capsaeformis (Bivalvia:Unionidae), reared in a captive environment
    Vincie, Meghann Elizabeth (Virginia Tech, 2008-08-25)
    Epioblasma capsaeformis, commonly named the oyster mussel, once occupied thousands of miles of stream reaches, but has now been reduced in range to small, isolated populations in a few river reaches. Due to this significant decline in population numbers, a study was conducted to develop a diet for propagating this endangered species under captive conditions. Oyster mussel juveniles were collected from several sites on the Clinch River and sacrificed for gut content and biochemical composition analyses in summer. Feces and pseudofeces from live river-collected juveniles were examined seasonally for algae, detritus, and bacteria to qualitatively determine diet of specimens. Two feeding trials also were conducted in this study to evaluate effect of diet (commercial and non-commercial diets), on growth and survival of oyster mussel juveniles. From examination of gut contents, fecal and pseudofecal samples, it was apparent that algae and a significant amount of detritus (~90%) composed wild juvenile diets. E. capsaeformis juveniles (1-3 y of age) could have fed on particles up to 20 µm in size and seemed they were mostly ingesting particles within the 1.5-12 µm size range. Protein content of sacrificed juveniles ranged from 313 to 884 mg/g and was highly variable. Glycogen content ranged from 49-171 mg/g. Caloric content of four juveniles ranged from 2,935.10 to 4,287.94 cal/g, providing a preliminary baseline range for future energetic studies on freshwater mussels. Growth was significantly higher in those juveniles fed the triple concentration algae-mix (62,076 cells/ml) than all other diets tested in trial 1. Results of both feeding trials indicated that survival of juvenile oyster mussels was enhanced when fed an algal diet supplemented by bioflocs.
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    A study of holding conditions, feed ration, and algal foods for the captive care of freshwater mussels
    Gatenby, Catherine M. (Virginia Tech, 2000-05-15)
    The use of glass racks and suspended pocket nets for holding freshwater mussels collected from the Ohio River and relocated to lined-ponds was studied over 3 years. Survival of mussels in ponds was 73 % after 1 y, 44 % after 2 y, and 5 % after 3 y. The glycogen levels of mussels in ponds for ly were significantly greater than that of mussels in ponds after 2.5 y and 3 y, indicating a chronic decline in body condition in mussels. Despite the presence of a diverse and dense assemblage of algae and organic detritus in the ponds, the stomachs examined at 3 y were empty and the bodies were emaciated. In the laboratory, I determined the amount of algae cleared by the rainbow mussel, Villosa iris (Lea, 1829) fed different algal rations, and estimated the algae concentration needed to maintain mussels in captivity. Filtration rate in the first feeding hour was highest in ration B (1.0 mg dry wt L⁻¹) and lowest in ration C (3.4 mg dry wt L⁻¹). After 1 h, filtration rates declined in ration B but increased in rations C and A. V.iris likely achieved gut satiation in the first hour using maximum filtration (712.5 mL h⁻¹g⁻¹) and then decreased filtration (259 mL h⁻¹g⁻¹) thereby regulating ingestion rate during the following 2 h. I estimate, therefore, that K V. iris daily maintenance requirement for carbon is 8.2 mg C (1.2 x 10⁹ cells of N. oleoabundans) or ca. 2.4% of dry body weight. Assimilation efficiencies (AE) and carbon budgets also were established for the rainbow mussel, Villosa iris (Lea 1829), using radio-labeled cultures of Neochloris oleoabundans (Chantanachat and Bold 1962) at three cell concentrations. Approximately 70% of the ingested carbon was assimilated (assimilation efficiency) by V. iris fed 5 x 10⁵ cells mL⁻¹) (3.4 mg dry weight L⁻¹). At 5 x 10⁴ cells' mL⁻¹) (0.34 mg dry weight L⁻¹), AE was 47.5 %. At 5 X 10³ cells mL⁻¹) (0.034 mg dry weight L⁻¹), AE was 40%. V. iris had the greatest amount of energy available for growth, reproduction, and body condition in captivity at 3.4 mg dry weight L⁻¹). The gross composition (protein, carbohydrate (CHO), and lipid) of four algae (Bracteacoccus grandis, Neochloris oleoabundans, and Scenedesmus quadricauda, and Phaeodactylum tricomutum) was examined at four different phases of growth. The CHO content (% algal dry wt) increased with growth phase (age of the algal culture) with the exception of B. grandis. N. oleoabundans and P. tricomutum contained the greatest CHO content (33.07 ± 6.89% and 39.37 ± 3.07%, respectively) at late stationary phase. The total lipid content increased with growth phase for N. oleoabundans and P. tricomutum. Lipid content of B. grandis decreased with age, and S. quadricauda showed no difference in lipid content (% algal dry wt) between growth phase. N. oleoabundans' lipid content (31.85 ± 9.4%) was greater than all other species. Generally, there was no effect of phase on the sterol content, with the exception of the sterol content of S. quadricauda increased with growth phase. The mean sterol content of the four algae ranged 1.0 % ± 0.4 to 1.8 ± 1.8 of the total lipid dry wt; maximum sterol % of lipid was 5 % for Scenedesmus and 4.4% for B. grandis. There was no effect of growth phase or species on the protein content (% of algal dry wt). The protein content ranged 60.6 ± 17.1 to 70.3 ± 9.5 % of algal dry wt.