Degree Name

Master of Science (MS)

Semester of Degree Completion


Thesis Director

Edward O. Moll


Thirty-seven male Chelydra s. serpentina were collected from Illinois, Louisiana, Mississippi, Tennessee, and Wisconsin during months of activity from May, 1969 to June 1971. Carapace length for each specimen was measured, and testes and epididymides were dissected out, weighed, measured, fixed, and preserved in Baker's neutral formalin within seven days of capture. Paraffin sections were stained with hematoxylin and eosin. Frozen sections were stained with Sudan IV.

The spermatogenic cycle was similar to those of other Chelonians and reptiles exhibiting post-nuptial spermatogenesis. In Illinois spermatocytogenesis begins in late March or early April. Meiosis is evident throughout May and early June. Spermiogenesis begins by mid June and continues through October. The germinal epithelium is quiescent from November through March. Free sperm are in tubule lumina and probably enter the epididymides from late August through October. Rough estimates of latitudinal variation in spermatogenic timing were made comparing Illinois specimens to those from extremes of the range. Wisconsin snapping turtles were approximately four to five weeks behind Illinois, whereas those from Louisiana and Mississippi were possibly four to six weeks ahead. A testicular lipid cycle complements the spermatogenic cycle. Genesis of cholesterol-positive lipids occurs within tubules and within interstitial and boundary cells at cessation of spermatogenesis. Lipids are depleted with the advent of spermatogenesis. During the breeding and mating period sparse cholesterol-positive reactions in intratubular areas indicated that little sex hormone was produced by the Sertoli cells. Small amounts of hormone might initiate growth and secretion in interstitial cells. Interstitial and boundary cells were rich in cholesterol-positive lipids indicating possible hormone production for controlling sexual behavior and spermatogenic development. Data on lipid activity suggests a spring and fall mating peak. Spermatogenesis begins in March or April when photoperiod and temperature are increasing, and sperm are evident in late June near the solstice. Declining day length appears to have little effect on spermatogenesis.

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