Abstract
AbstractIn this report, seasonal changes in testicular structure and spermatogenesis in several shark species are reviewed, and new information concerning the bonnethead shark, Sphyrna tiburo, is presented. Shark species are separated into four categories based on the relationship between testicular GSI and mating season: 1) species that have a defined seasonal cycle in GSI and a defined mating season, 2) species that have a defined seasonal cycle in GSI and that mate year‐round, 3) species that show no seasonal change in GSI but that have a defined mating season, and 4) species that show no seasonal change in GSI but that mate year‐round. The testis of S. tiburo differs from the few species that have been examined in that 1) not all spermatogenic stages are present at all times of the year, 2) an annual zone of degeneration that progresses through the testis is not present, and 3) there appears to be complete testicular regression and recrudescence.
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