Ontogenetic change in the body length–mass relationship concomitant to the onset of vitellogenesis in female blackmouth catshark Galeus melastomus (Chondrichthyes: Scyliorhinidae)

Abstract The examination of the total length (L) vs. body mass (W) relationship in the blackmouth catshark from the southern Adriatic Sea showed the occurrence of two development phases or growth stanzas in females. The passage from the first stanza (L range: 22.8–37.4 cm) to the following one (L range: 39.7–51.4 cm) was marked by an inflection in the power equation correlating body mass to total length, occurring at about 38.6 cm of length (change point). After the change point, growth became positively allometric. This catshark is a lecitotrophic oviparous continuous spawner, and follicles in different stages of development are simultaneously present in the ovary. The histological analysis of the ovary showed that the smallest vitellogenic follicles were about 2 mm in diameter; the diameter of the largest observed oocyte was 18 mm. The change point occurred slightly before the onset of vitellogenesis (smallest vitellogenic female L = 41.0 cm) and appeared to be related to the activation of the reproductive axis.