Oviducal gland microstructure ofRaja miraletusandDipturus oxyrinchus(Elasmobranchii, Rajidae)

Abstract

We studied the morphology and histology of the oviducal gland (OG) in the brown ray (Raja miraletus) and the long-nosed skate (Dipturus oxyrinchus) to understand its functional role in the reproductive strategy of these species. The external morphology of the gland was similar in both species, with lateral extensions like those found in other members of the Rajidae. Microscopic analysis showed a similar internal organization in both species. Immature and developing glands did not react to histochemical techniques. On reaching maturity, the OG had the largest width due to an increase in the production of secretory materials. In both species, the club zone of the gland showed a strong reaction to Periodic acid-Schiff (PAS) and alcian blue (AB) stains, indicating production of neutral and sulfated acid mucins. The secretory material produced by the papillary zone varied greatly between the two species. Both displayed tubular glands similar to those observed in the club zone, but in D. oxyrinchus the region near the lumen was intensely PAS+, whereas the last row of tubules of the brown ray stained intensely for a mixture of neutral and sulfated mucins. The baffle zone was the most conspicuous and extensive segment of all OGs, and it did not react to PAS/AB. The terminal zone, which is responsible for production of hair filaments, differed between the two species in terms of composition and organization of serous and mucous glands. This difference probably is related to the different substrates in which they release the egg capsules. Individual sperm detected in the brown ray baffle lamellae could be the result of a recent mating, whereas their presence in the deep recesses of the baffle and in the terminal zone of the long-nosed skate might indicate sperm storage.

Morphological descriptions of the eggcases of skates (Rajidae) from the central-western Mediterranean, with notes on their distribution

“…As a general rule, eggcases covered by fibers were produced by mixed gland tubules (mucous and serous) situated deep in the terminal zone of the oviducal gland as reported for many Rajidae species (e.g. D. oxyrinchus, R. montagui, R. brachyura, R. clavata and R. undulata) by Maia et al [38] and Marongiu et al [41]. L. melitensis differed from the remaining species, because its eggcases were smooth, devoid of fibres on their surface.…”

“…Furthermore, D. nidarosiensis, D. oxyrinchus and R. brachyura eggcases were the most robust. This feature was certainly related to their oviducal gland microarchitecture, characterized by a higher number of lamellae of the baffle zone [38,41], if compared with the eggcases from R. miraletus characterized by a lower number of lamellae [41]. From an ecological perspective, these features, probably due to the length of the developmental period, may represent an advantage against predation and water turbulence [38] considering that their big dimensions did not allow a proper camouflage.…”

Life‐history traits of the long‐nosed skate Dipturus oxyrinchus

“…This asynchrony suggests that populations could be sexually segregated and mating could occur prior to egg‐laying. Dipturus oxyrinchus females are known to be able to store sperm inside the oviducal gland (Marongiu et al ., ), which could explain the presence of spawning females throughout the entire year.…”

“…oxyrinchus have been studied in Turkish (Yigin & Ismen, ) and Tunisian waters (Kadri et al ., ). In addition, a few other papers have been published on other biological aspect of this species, such as feeding behaviour (Kadri et al ., ; Yigin & Ismen, ; Mulas et al ., ) and oviducal gland morphology (Marongiu et al ., ).…”

Glycan expression as a tool for a deeper understanding of a reproductive gland in a skate of economic importance

“…The baffle zone forms the tertiary envelopes of the egg and the egg's ornamentations are produced in the terminal zone. Some species are also known to store sperm in the terminal zone (Maia et al ., 2015; Marongiu et al ., 2015; Moura et al ., 2010; Serra‐Pereira et al ., 2010).…”