Reproduction of the whitesnout guitarfish Rhinobatos leucorhynchus in the Ecuadorian Pacific Ocean

Abstract

Biological sampling of whitesnout guitarfish Rhinobatos leucorhynchus, caught as by-catch in the commercial fisheries on the Pacific coast of Ecuador, was conducted from specimens caught between April 2013 and January 2015, in order to provide further information on the reproductive biology of this species, for which data are limited. Samples comprised 1024 specimens (458 males and 566 females), with the sex ratio (1:1·23) significantly in favour of females. The total length (LT) ranged from 20·5 to 106·0 cm and showed sexual dimorphism, with females attaining a larger size. The relationship between body mass (MT) and LT was not significantly different between sexes. The length at 50% maturity for males based on internal reproductive organs was 60·9 cm LT , which was slightly larger than when based on clasper condition alone (58·5 cm LT). The LT at 50% maturity for females was 57·8 cm, and the LT at maternity was 65·1 cm. Fecundity ranged from one to seven embryos and LT at birth was 20-26 cm. According to oocyte development, two peaks of ovulation were observed (May to June and November to December). The ovarian cycle was estimated at 6 months and gestation between 5 and 6 months. Embryos showed different sizes all year-round, indicating an asynchronous cycle.

Reproductive biology of the Brazilian guitarfish, Pseudobatos horkelii (Müller & Henle, 1841) from southeastern Brazil, western South Atlantic

“…Clasper length presented a sigmoid growth pattern, a common pattern observed in several elasmobranchs (Oddone, Amorim, Mancini, Norbis, & Velasco, ; Romero‐Caicedo & Carrera‐Fernández, ; Serra‐Pereira et al., ). This suggests that clasper growth is faster when individuals are close to attaining sexual maturity.…”

First record of clasper malformation of Pseudobatos buthi (Chondrichthyes: Rhinobatidae) in the Gulf of California

“…The sperm flow could be related to the storage times of the spermatozoa in the seminal vesicle. If we consider that P. buthi is a coastal ray without long migrations, it might not store sperm like other species of the same genus (Romero-Caicedo & Carrera-Fernández, 2015;Martins et al, 2018).…”

Presence of pregnant females of the Gorgona guitarfish, Pseudobatos prahli, in the Mexican tropical Pacific

“…This means that the development of embryos and oocytes occurs at the same time; therefore, a gravid female gives birth, and ovulation and fertilization occur immediately after. This is supported by the fact that it is a characteristic of most species in the Rhinobatidae family (Capapé & Zaouali, 1994; Grijalba‐Bendeck et al ., 2008; Márquez‐Farías, 2007; Romero‐Caicedo & Carrera‐Fernández, 2015; Seck et al ., 2004). Nonetheless, the duration of vitellogenesis and embryogenesis is not known, and future studies should investigate what occurs from April to February to establish the duration of the P. prahli reproductive cycle.…”