On the development of the oviducal gland in the Rajid brown ray, Raja miraletus Linnaeus, 1758

The oviducal gland, in oviparous cartilaginous fishes, plays the important role to produce the egg capsules containing fertilized eggs and to storage sperms in some species. To better understand the reproductive strategies of these animals, in this work we reported the first investigation on the macroscopical and microscopical structure of Raja miraletus’ oviducal gland from Sardinian waters (central western Mediterranean). Macroscopical analysis showed that the size of the oviducal gland increased with maturity reaching the largest width at the extruding stage, and having a consequent decline in regressing and regenerating ones. Histological study displayed that its development started at the maturing stage and completed at mature one. The previous analysis also permitted to discern the four zones composing the gland: club, papillary, baffle and terminal. Periodic acid-Schiff (PAS) and alcian blue (AB) histochemical staining highlighted that the club zone stained AB+, PAS+ and AB+/PAS+; papillary showed a mixture of PAS+ and AB+; baffle seemed not react to this staining technique and the terminal zone was positive to AB and PAS near to the lumen. Furthermore, not aggregated sperms were observed in the secretory ducts of the baffle zone, near to the lamellae and the terminal zone. The histological measurements allowed, also, to observe an increase in size of the glandular area of each zone with maturity. Baffle zone, which has the task to form the egg capsule, represented the largest glandular zone in each stage reaching about 70% of the total area in mature females.