Histological and Morphological Aspects of Reproduction in Male Blackspotted Smooth-HoundMustelus punctulatusin the Adriatic Sea (Eastern Mediterranean Sea)

Abstract

We present first data on reproductive biology of male blackspotted smooth-houndMustelus punctulatusin the Adriatic Sea and first histological examination of gonads at different maturation stages and seasonal cycles for this species. We collected samples from 117 male specimens ofM. punctulatusranging in length from 44.6 to 126.5 cm, caught by commercial bottom trawls in the North-Central Adriatic Sea. Microscopic observation revealed a diametric development of testes, in which round-shaped spermatocysts have zonal arrangement, showing seven different stages of development. Males began to mature when they were between 61 and 88 cm body length, which was indicated by the presence of functional claspers or appearance of the spermatogenic cysts. While the smallest mature shark was only 80 cm long, all animals longer than 89 cm were sexually mature. The seasonal analysis of the testes indicated that mature spermatozoa dominated in testes during the first half of the year with a peak in May and June, after which followed less active period during July and August.

Revealing Spermatogenesis in Smooth-Hound Sharks Mustelus mustelus: Insights into the Morphological and Macromolecular Composition of Spermatogenic Cells

“…In this type of testis, the direction of spermatogenesis is clearly distinguishable, with different areas characterized by cysts at the same developmental phase ( Figure 1 ). In mature males, spermatogenesis is characterized by the proliferation and differentiation of both germinative cells and Sertoli cells and occurs through seven different phases, as already reported for other species of the Mustelus genus [ 28 , 29 , 30 , 31 ]. The count of spermatogenesis phases may vary based on the subjective discretion of different authors.…”

“…Also, apoptotic events involving both germinal and Sertoli cells, observed during spermatogenesis in some elasmobranch species, may offer valuable information to characterize distinct spermatogenic mechanisms given their species-specific nature [ 27 ]. The genus Mustelus , similarly to all the members of the Carcharhinidae family, presents a diametric testis, in which spermatogenesis occurs diametrically from the germinal zone (GZ), located on one wall of the testis, to the opposite wall where the efferent ductulus collects the spermatozoa [ 28 , 29 , 30 , 31 ]. In this type of testis, the direction of spermatogenesis is clearly distinguishable, with different areas characterized by cysts at the same developmental phase ( Figure 1 ).…”

Contrasting life‐history traits of two sympatric smooth‐hound species: implication for vulnerability

“…This result is in line with a latitudinal pattern of maximum size and size at sexual maturity observed in the Mediterranean Sea in the small‐spotted catshark Scyliorhinus canicula L 1758 (Finotto et al ., ) and, among the few other sharks for which data are available, in the starspotted smooth‐hound Mustelus manazo Bleeker 1855 in the Pacific Ocean (Yamaguchi et al ., ). A further study, performed using histological analyses of gonads, estimated the size at maturity of M. punctulatus males in the north‐eastern side of the Adriatic Sea, revealing slightly smaller minimum sizes at maturity (80 cm; Gračan & Lacković, ), possibly related to the different methods used to assess maturity. Nonetheless, all specimens >89 cm were sexually mature (Gračan & Lacković, ), a result quite similar to that obtained in this study (Table ).…”

“…A further study, performed using histological analyses of gonads, estimated the size at maturity of M. punctulatus males in the north‐eastern side of the Adriatic Sea, revealing slightly smaller minimum sizes at maturity (80 cm; Gračan & Lacković, ), possibly related to the different methods used to assess maturity. Nonetheless, all specimens >89 cm were sexually mature (Gračan & Lacković, ), a result quite similar to that obtained in this study (Table ).…”