Luminal composition and maturation of spermatozoa in the genital ducts of the African elephant (Loxodonta africana).

The mean spermatocrit and sodium, potassium and protein concentrations of fluid collected from the rete testis of the elephant were similar to values described for the ram. Sperm maturation, as assessed by the location of the cytoplasmic droplet in the middle pice, occurred in the distal head and the isthmus of the epididymis (middle segment). Spermatocrit determinations indicated that 96% of the fluid leaving the testis was reabsorbed by the efferent ducts and proximal initial segment, and 53% of the remainder was reabsorbed in the more distal parts of the head of the epididymis (initial and proximal middle segments). Sodium was reabsorbed in the same concentration as luminal fluid and not in amounts equimolar with potassium. The potassium concentration increased from 12.1 mequiv./l in rete testis plasma to 64.8 mequiv./l in the proximal head of the epididymis. About two thirds of the protein in rete testis fluid (3.8 mg/ml) was reabsorbed by the efferent ducts and more was absorbed by the head of the epididymis.