COMPARATIVE MORPHOLOGY OF THE MYOMERES AND AXIAL SKELETON IN 4 GENERAOF CENTRARCHID FISHES

We used X-rays and dissection of myotomes to quantify the axial morpho logy of four species of centrarchid fishes (Micropterus salmoides, Amb loplites rupestris, Pomoxis nigromaculatus, and Lepomis macrochirus). Proceeding from dorsal to ventral, we designated the two epaxial and t wo hypaxial portions of the myomeres AB, BC, CD, and DE, respectively. For each of 11 myomeres, spaced at 10% increments along the length of the fish, a total of 14 variables described the length and orientatio n of each portion, the dorsal-ventral symmetry, and the overall height and longitudinal span of the entire myomere. Nine variables described the lengths, orientation, and symmetry of the vertebral centra, neura l and hemal spines, and ribs. Analysis of variance revealed that, with one exception, all 23 morphological variables varied significantly bo th among species and among longitudinal locations within a species. Ho wever, the extent of longitudinal and interspecific variance differed considerably among different variables. Maximal myomeric height ranged from about 45% of the standard length (SL) in Lepomis to 27% SL in Mi cropterus. Longitudinal and interspecific increases in overall height of the trunk myomeres resulted primarily from greater lengths of CD. C ompared to other portions of the myomere, the length of BC was most co nservative both longitudinally and interspecifically. Dorsal-ventral s ymmetry of the myomeres and axial skeleton was greater in the caudal r egion than in the trunk in all species, and the myomeric morphology di verged least among species in the posterior caudal region. The overall longitudinal span of superficial myomeric landmarks varied from 6% to 18% SL, and, including the deep portions of the myomeres, the longitu dinal span varied from about 7 to 10 vertebrae. Within each of the spe cies, myomeric and skeletal variables were often not significantly cor related, but for the pooled data of all species there were usually hig hly significant correlations between myomeric and skeletal morphology. For example, strong correlations existed between BC and the underlyin g neural spines, and between CD and the underlying ribs and hemal spin es. In contrast, the longitudinal spans of entire myomeres and underly ing axial skeletal segments were only weakly associated. (C) 1994 Wile y-Liss, Inc.