Geographic and Temporal Variation in Numbers of Myomeres in Fish Larvae from the Lower Mississippi River

摘要

There was statistically significant geographic and temporal variation in numbers of myomeres in larval freshwater drum Aplodinotus grunniens, river carpsucker Carpiodes carpio, and bluegill Lepomis macrochirus collected throughout the 1978 spawning season from the Mississippi River at Eudora, Arkansas, and St. Francisville, Louisiana. The mean number of total myomeres in each species usually was higher at St. Francisville than 400 river kilometers north at Eudora. Freshwater drum larvae at Eudora had fewest myomeres during periods of warmer water temperatures; freshwater drums at St. Francisville, and river carpsuckers and bluegills at both locations, had either stable or fluctuating myomere counts as the season progressed. Such variation in diagnostic characters should be accounted for when local or regional keys are constructed for fish larvae.