Embryological Comparison of Lepomis macrochirus X macrochirus and Lepomis macrochirus X gibbosus
The bluegill, Lepomis macrochirus Rafinesque, and the pumpkinseed, Lepomis gibbosus (Linnaeus), were crossed by an artificial fertilization technique. This resulted in two types of offspring; that is, Lepomis macrochirus X macrochirus and Lepomis macrochirus X gibbosus. A comparative study was made: (1) to determine the incubation time, (2) to determine the per cent hatched, (3) to compare standard length of the early larva, and (4) to compare heart development. The results were: (1) the hybrid cross, under the specific circumstances of the experiment, had a 3.1 hour faster mean incubation time than the pure cross, (2) the hybrid cross gave the higher per cent hatched, 63.4% (625) as compared to 51.7% (834) for the pure cross, (3) no significant standard length difference was found, and (4) heart differentiation began with a tubular heart and ended with the development of a series of four chambers. No morphological difference in heart development was observed. There were, however, differences in heart positioning and maturation. © 1969 Taylor & Francis Group, LLC.