Genital morphology of the male South American fur seal (Arctocephalus australis) and biological implications

Abstract

Male capacity for spreading genes to a great number of descendents and to determine population dynamics depend directly on the genital organs. Morphological studies in pinnipeds are scarce and the functional meaning of some characteristics has never been discussed. We hypothesized that Arctocephalus australis (A. australis) shows morphophysiological adaptations in order to guarantee the perpetuation of the species in the unique annual mating season. Seven males, dead from natural causes, had their genital organs collected and fixed for morphological description. Some features differ from other described mammalian males and are closely related to the biology and reproductive cycle of this species, as the scrotal epidermis, absence of glandular portion in the ductus deferens and spermatogenic epithelium suggest a recrudescent testis period. The corona glandis exhibits a singular arrangement: its erectile border looks like a formation of petals and its association with the os penis gives a "lily-flower" form to this region. We propose the name margo petaliformis to this particular erectile border of the corona glandis because of its similarity to a flower corola. The male genital organs of A. australis show morphological features compatible with adaptation to environment requirements and reproductive efficiency.

Morphology of the male reproductive tract of Eira barbara

“…In domestic animals, the gonads appear in an upright position in ruminants, are inclined (or oblique) in pigs and felines and are horizontal in canines and horses. The shape of the testicles is ovoid in wild carnivore species such as the southern sea wolf (Machado et al, 2012), the coati (Franciolli et al, 2007), the ocelot (Carneiro et al, 2010; Machado et al, 2020), the tiger (Meireles et al, 2012) and irara in the present study.…”

“…reported that the testicles are ellipsoid in shape and that their volume has no fixed relationship with body size.Their orientation within the scrotum and the direction of the longitudinal axis vary according to the species. In domestic animals, the gonads appear in an upright position in ruminants, are inclined (or oblique) in pigs and felines and are horizontal in canines and horses.The shape of the testicles is ovoid in wild carnivore species such as the southern sea wolf(Machado et al, 2012), the coati(Franciolli et al, 2007), the ocelot(Carneiro et al, 2010;Machado et al, 2020), the tiger(Meireles et al, 2012) and irara in the present study.The length and shape of the spermatic funicle may vary according to the testis position and orientation. The funicle includes the testicular artery and veins, lymphatic vessels, nerves, bundles of F I G U R E 3 Photomacrography of the penile bone with a rounded distal end with a small "C" shaped border.…”

“…It is located in the dorsal portion of the initial urethra and is a compact organ, with glandular and muscular parts. There is no division into lobes; rather, the gland has a spherical shape in a single lobe (Machado et al,2012). Differing to the Micomarcai that have two lobes in prostate gland, a dorsocranial and a dorsolateral, and had ampullar gland (Siqueira et al, 2018).…”

“…In this species, the baculum is triangularly shaped and is flattened laterally with epiphyses dilations. The caudal end has a larger diameter and no region for urethral insertion (Machado et al, 2012). In dogs, partial closure of the urethra within the groove of the penile bone prevents the passage of urethral stones, which, therefore, tend to lodge at the caudal end of the bone (Dyce et al, 2010).…”