Effect of Temperature on the Identification of Larval Black Crappies, White Crappies, and F₁ Hybrid Crappies

Abstract

Myomere counts have been used to differentiate larval black crappies Pomoxis nigromaculatus and white crappies P. annularis; however, both hybridization and water temperatures during egg development can influence myomere numbers and thereby interfere with identification of larval crappies. We artificially produced pure black crappies, white crappies, and their F₁ hybrids and allowed them to develop at different temperatures. We then compared counts of preanal, postanal, and total myomeres among taxa and water temperatures. Although white crappies had significantly more preanal myomeres and significantly fewer postanal myomeres than the black crappies or the F₁ hybrids, counts of these myomeres overlapped too much to be useful for identification purposes. Some of the overlap of myomere numbers was caused by variation due to natal water temperature differences. Higher temperatures caused the anus to develop more posteriorly in larval crappie, influencing the number of preanal and postanal myomeres. Because myomere counts overlap so much and because hybridization and natal water temperature can induce variation in myomere numbers, myomere counts are not useful for discriminating between the two species of Pomoxis.