To study life history characteristics of the pleurocerid gastropod genus Elimia, direct measurements of shell growth of free-ranging marked snails were combined with analyses of temporal change in size structure of eight lotic populations: E. cahawbensis (3 populations), E. variata (1), E. carinifera (1), E. fascinans (3) from six streams throughout central Alabama. Although minor variation was apparent, the general pattern of oviposition, growth, and cohort structure was strikingly similar among populations, being characterized by: 1) the production of eggs over an extended period from spring through early summer and the appearance of juveniles in late summer and autumn, 2) two discrete periods of rapid growth confined to spring and summer during the 1+ yr and 2+ yr age classes, and 3) an age structure consisting of a minimum of three simultaneous cohorts. To estimate the minimum cohort duration for each population, an iterative bootstrap model was developed. This model predicted cohort durations ranging from a minimum of ∼2+ through 6+ yr among the populations studied and suggested that, even at relatively low latitudes (∼33°N), relatively long lifespans and complex cohort structure may be expected among populations of Elimia. A comparison of life history information derived in the present study with that available for other species of Elimia and other pleurocerid genera (Leptoxis, Pleurocera) shows a strong consistency among major aspects of life histories of the North American pleurocerids from northern temperate through essentially subtropical latitudes.
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