Seasonal morphology and histology of the androgenic gland of the crayfish, Orconectes nais

Abstract Male Orconectes nais were hatched in the spring and completed an unknown number of Form II growth molts during the summer. The population molt from the sexually inactive Form II to the sexually active Form I occurred in late August and early September. The population molt from Form I back to Form II occurred in the spring. Some males, smaller than the norm for the population in late summer, remained in Form II during their first year and completed the first molt cycle in their second year. Crayfish older than 1 year represented a small percentage of the population; however, the limited data establish that some males complete more than one molt cycle and more than one period of reproductive activity. The androgenic gland of the youngest crayfish examined consisted of a small number of small cells with dense, homogeneous cytoplasm and closely associated with the vas deferens; no foci of cellular degeneration were observed. The androgenic gland increased greatly in size during the summer. The gland proliferated as a sheet-like arrangement of masses of cells and parallel and anastomosing cords; however, the cells enlarged only slightly and the cytoplasm remained homogeneous. Occasional foci of cellular degeneration were observed and involved from as few as two cells to a much larger number. The androgenic gland attained its maximum size a week or two prior to the population molt from Form II to Form I. The gland changed from the previous sheetlike arrangement to one of entwined cords. Further, the cells were largely hypertrophied and contained vesicular cytoplasm; areas of cellular degeneration were both common and extensive. Testicular maturation and spermatogenesis occurred early in the summer, and generally spermatogenesis was absent in August, although sperm were retained in the vas deferens during the winter. Thus, testicular activity largely preceded the proliferation of the androgenic gland and occurred when the androgenic gland contained primarily the small cell and only occasional areas of cellular degeneration. The molt from Form II to Form I and the subsequent period of reproductive activity were associated with an androgenic gland of maximum size that contained primarily hypertrophied cells with vesicular cytoplasm and numerous, extensive areas of cellular degeneration. The observations indicate that the androgenic gland possesses sufficient activity prior to and during its proliferation to stimulate testicular maturation and spermatogenesis but insufficient activity to stimulate the differentiation of the Form I gonopod; the differentiation of the sexually active gonopod and the reproductive activity that follows the molt from Form II to Form I may occur in response to an increase in the activity of the androgenic gland. Although some activity must be assumed for the androgenic gland prior to and during the proliferation of the gland, the cells responsible for the activity remain unknown. If the foci of cellular hypertrophy and degeneration represent holocrine secretion, the small areas of degeneration occasionally observed during the proliferation of the androgenic gland could account for the low level of activity suggested to be responsible for testicular maturation and spermatogenesis; the increase in the number of hypertrophied cells and the more numerous and extensive areas of cellular degeneration could account for the suggested increase in the activity of the androgenic gland prior to the molt from Form II to Form I. However, cellular degeneration was most common after the animals molted to Form I. Alternatively, the small cells must be assumed to have sufficient activity to account for testicular growth and spermatogenesis. The suggested increase in the androgenic gland activity could be due to the increase in the size of the gland and/or the increase in the number of the hypertrophied cells; cellular degeneration may represent the termination of the secretory cycle. The androgenic gland regressed during the winter. The spring molt from Form I back to Form II occurred when the androgenic gland was small and contained only the small cells. The data indicate that the second molt cycle and the second reproductive period are similar to those of first year crayfish, although differences do occur. Testicular activity begins immediately following, or possibly even prior to, the spring molt from Form I to Form II and at a time when the androgenic gland is small and contains only the small cells. Further, unlike the first year crayfish, the androgenic gland of older animals undergoes massive degeneration that is well-advanced at the time of the spring molt to Form II and appears to represent a permanent loss of activity.