Histological Differentiation along Turtle Ductus Epididymidis, with a Note on Secretion of Seminal Proteins as Discrete Granules

Histological analysis of the male reproductive tract of the peninsular flap-shelled turtle Lissemys p. punctata revealed that several minute ductuli efferentes reach the epididymis to form into a large thin-walled duct which probably, forms a temporary storage region of sperm arriving from the testis. Originating from this duct, the single long ductus epididymidis takes a highly tortuous course when it differentiates along its length, in terms of diameter and epithelial organization, into four regions, viz., the initial segment, caput, corpus and cauda. Turtle ductus epididymidis differs from that of lizards in the extensive pattern of folding of the epithelium of caput, corpus and cauda regions. The differentiation along the ductus epididymidis of the turtle signifies different functional attributes to the different regions. The epithelium of the initial segment of the turtle epididymis secretes large glycoprotein granules (4-8 μm) and that of the caput secretes minute granules (1-2 μm). The large granules possess a central core and a peripheral coat, whereas the minute granules are uniformly dense. Thus, turtle ductus epididymidis differentiates into initial segment, caput, corpus and cauda regions, and the initial segment and caput secrete seminal proteins in the lacertilian pattern as discrete granules.