Reproductive strategy of the Pacific cownose ray Rhinoptera steindachneri in the southern Gulf of California

Abstract

Rhinoptera steindachneri is one of the most common batoid species in the artisanal gill net fishery of the Gulf of California. In this study we investigated its reproductive biology based on 317 specimens caught in Bahía de la Paz, Mexico. Females measured up to 94.2-cm disc width (DW) and males reached 82.5cm DW; there were no significant differences in size or weight between sexes. The median size at maturity was estimated at 68.5cm DW for males and 71.8cm DW for females, and the median size at pregnancy was 84.3cm DW. Only the left ovary and uterus were functional; a maximum of six preovulatory vitellogenic follicles per female was recorded, although uterine fecundity was one embryo per female. Ovulation and birth occurred in May, June and July, with birth sizes ranging from 38.1 to 42cm DW. R. steindachneri in Bahía de la Paz exhibited low fecundity, large size at maturity and birth and a continuous and synchronous annual reproductive cycle.

Reproductive biology of the whitespotted eagle ray Aetobatus narinari (Myliobatiformes) captured in the coast of Paraíba and Pernambuco, Brazil

“…Myliobatiformes males, in general, have both testes functional, with little difference in size or mass, as observed for Rhinoptera steindachneri (Burgos-Vázquez et al, 2018), M. ridens and M. goodei (Araújo et al, 2016), Rhinoptera bonasus (Poulakis, 2013) and H. guttatus (Melo, 2016).…”

“…The males in this study showed no significant difference between the paired structures (testes and clasper glands). Both sides of the reproductive tract of A. narinari males were functional, with the greatest observed value for L C being 184 mm, for L CG 69 mm and for M TE 155 g. Myliobatiformes males, in general, have both testes functional, with little difference in size or mass, as observed for Rhinoptera steindachneri (Burgos‐Vázquez et al ., 2018), M. ridens and M. goodei (Araújo et al ., 2016), Rhinoptera bonasus (Poulakis, 2013) and H. guttatus (Melo, 2016).…”

Morphological abnormalities in seven American round ray specimens: A review of America's batomorph anomalies

“…However, this free‐living report should be considered doubtful. Recent biological information available for this species off the northwestern coast of Mexico confirms a birth size range between 381 to 420 mm DW (Burgos‐Vázquez et al., 2019; Ehemann et al., 2019) compared with the ≈200 mm DW abnormal specimen, meaning that the latter corresponded to a fully developed embryo. Although capture‐induced parturition has not yet been confirmed for this species (Adams et al., 2018), this scenario is also plausible to be considered for the abnormal Mexican cownose ray.…”

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

“…The OG has the same basic organization in most studied elasmobranchs, but the reproductive relevance of each glandular region varies (Hamlett et al ., 1998, 2005). Only the Narcinidae (electric rays, Torpediniformes) lack the OG (Prasad, 1945), and some species of Myliobatiformes have a vestigial OG (Burgos‐Vázquez et al ., 2018; Colonello et al ., 2013). Conversely, oviparous species have the largest OGs among chondrichthyans, since they produce not only the jellies that envelop the egg, but also an external capsule and all its ornamentations (Hamlett et al ., 2005; Serra‐Pereira et al ., 2010).…”