Andrology of Shortnose Guitarfish Zapteryx brevirostris (Müller & Henle, 1841) (Chondrichthyes, Trygonorrhinidae).

Abstract

The andrological study of a species comprises from the macro- and microscopic analysis of the internal reproductive organs to the evaluation of seminal parameters and ultrastructural characteristics of the spermatozoa. As in other vertebrates, the male reproductive tract in chondrichthyans is composed of testes and reproductive ducts (efferent duct, epididymis, Leydig's gland, ductus deferens and seminal vesicle). In this study we used three adult specimens of Zapteryx brevirostris from wild capture and kept at the Ubatuba Aquarium, Brazil. Semen collection was performed by abdominal massage, over the location of the seminal vesicle, preceded by ultrasonographic evaluation. The semen collected was diluted 1:200 and submitted to quantitative and morphological analysis. Ultrastructural analysis was performed by transmission and scanning electron microscopy. Correlation was observed between successful collection and ultrasonographic image of an engorged seminal vesicle, as well as testicles with easily delimitable margins and higher echogenicity. It was possible to identify free spermatozoa with helical filiform appearance, as well as spermatozeugmata. The average sperm concentration resulted in 5 million packets per ml and 140 million spermatozoa per ml. The sperm nucleus showed cone shape, parachromatin sheath less dense than the chromatin of the nucleus, smooth depression of the nuclear fossa, abaxial axoneme 9+2 and accessory axonemal columns in position 3 and 8 and oval shaped, with flattened inner surface in cross section. These results broaden the knowledge about the andrology of this species, contributing to ex situ breeding programs.