1990. Dynamics of filter feeding in Corbiculafluminea (Bivalvia: Corbiculidae). Can J. Zool. 68: 115-120. Filtration rates of Corbiculafluminea were measured using 2-pm microspheres from three riverine habitats which differed in ambient suspended particle concentration; rates were measured at particle concentrations spanning the range for the three habitats. Filtration rates were significantly different across the three habitats, and were inversely correlated with the mean ambient suspended particle concentrations: 66.4 mL/h for 1 1 mg/L, 100.2 mL/h for 7 mg/L, and 144.9 mL/h for 4 mg/L for the Tombigbee, Ouachita and Tangipahoa rivers, respectively. However, the weight of particles filtered by clams from the three rivers was not significantly different. These results indicate that C.fluminea can make physiological adjustments to its filtration rate to achieve some "optimal" rate of particle removal. Within each habitat, particle concentration had a significant effect on filtration rates for the Tombigbee River and Tangipahoa River populations; maximal filtration rates were observed in the range of ambient particle concentrations for each habitat. The effects of particle size and type on filtration rates were examined for clams from the Tombigbee River. Filtration rates were measured with microspheres of various sizes, natural suspended particles, and Chlorella. Filtration rates were highest with natural suspended particles; these particles were also the smallest in size (3 X 5 pm). Rates were also highest when measured with particles representative of the size range encountered in the field. There was no significant difference in filtration rates measured with similar-sized microspheres and Chlorella. Pseudofeces were produced by all sizes of clams from each population at particle concentrations greater than 12 mg/L. For the Tombigbee River population, pseudofeces were produced by all sizes of clams at particle sizes greater than or equal to 16 pm. These data indicate that there are potential morphological constraints on the clam gill that limit the range of particle concentrations and sizes that can be processed. Laboratory observations also demonstrated the capacity for deposit feeding in C.fluminea. Our data indicate that filter feeding in C.flumineu is a complex phenomenon, requiring an understanding of how the physiological process of feeding is influenced by morphological constraints imposed upon gill functioning and by the temporal effects of environmental variables. In addition, the plasticity in the filter-feeding response and the capacity for alternative feeding modes contribute to the success of C.fluminea as an invasive species. WAY, C. M., HORNBACH, D. J., MILLER-WAY, C. A., PAYNE, B. S., et MILLER, A. C. 1990. Dynamics of filter feeding in Corbiculafluminea (Bivalvia: Corbiculidae). Can J. Zool. 68 : 1 15-120. Les taux de filtration ont t t t mesurts au moyen de microsphkres de 2 pm chez des Corbiculafluminea provenant de trois cours d'eau a concentrations difftrentes de particules en suspension; l...

The pisidiid clams, Pisidium variabile (Prime) and Pisidium compressum (Prime), from permanent ponds in southwestern Ohio are iteroparous, bivoltine, and have approximate longevities of 1 year. Intrapopulation differences in life history characteristics are discussed in relation to environmental heterogeneity. For the P. variabile population, only age at first reproduction (110 and 226 days for the spring and fall generations, respectively) is different for both annual generations. This is due to differences in environmental variables (temperature, dissolved oxygen levels, food availability) which set physiological limits on growth, reproduction, and maintenance functions. The spring and fall generations of P. compressum show differences in several life history characteristics: age at first reproductive (122 and 270 days, respectively), net reproductive rate (8.7 and 3.7, respectively), r (0.005 and 0.003, respectively), and the number of broods per year (2 and 1, respectively). The results of this study tend to question the validity of using current theories (e.g, r- and K-selection, bet-hedging) which attempt to predict the set of demographic characteristics that should be found in populations under varying environmental circumstances.

No abstract

No abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.