Embryonic diapause in the elasmobranchs

Abstract

Embryonic diapause is a temporary suspension of development at any stage of embryogenesis, which prolongs the gestation period, allowing parturition to occur in conditions that are more suitable for newborns. This reproductive trait is widespread among all vertebrates, including elasmobranchs. Although it has only been confirmed in two elasmobranchs (Rhizoprionodon taylori and Dasyatis say), evidence indicates that at least 14 species of rays and two sharks undergo diapause, suggesting that this form of reproduction exists within a wide range of elasmobranch reproductive modes, including lecithotrophs and matrotrophs. Where it has been studied, embryogenesis is arrested at the blastodisc stage and preserved in the uterus for periods from four to 10 months. There are still many questions that remain unanswered concerning the knowledge on the biology of most diapausing species but it is clear that species benefit differently from this reproductive trait. As in other vertebrates, it is likely that environmental cues and hormones (especially progesterone and prolactin) are involved in the control of diapause in elasmobranchs, however rigorous testing of current hypothesis remains to be carried out.

Reproductive Strategy of the Giant Electric Ray in the Southern Gulf of California

“…This study provides evidence that the Giant Electric Ray has a continuous annual reproductive cycle; one peak of ovulation occurs between July and September but two peaks of parturition occur (minor peak in January-February and REPRODUCTIVE BIOLOGY OF GIANT ELECTRIC RAY 589 major peak in August-September). These two peaks of births suggest that a majority of female Giant Electric Rays undergo embryonic diapause, as previously suggested by C. J. Villavicencio-Garayzar, M. E. Mariano, and C. H. Downtonn (abstract presented at the 6th Indo-Pacific Fish Conference, 2001) for this species, and similar to reports for other species of rays (Lessa 1982;Simpfendorfer 1992;Morris 1999;Waltrick et al 2012). Additionally, in contrast to previous reports of matrotrophy in this species (Villavicencio-Garayzar 2000), histological evidence of secretory material in endometrial tissue during late pregnancy suggests the Giant Electric Ray presents limited histotrophy as a reproductive mode.…”

Mechanisms of animal diapause: recent developments from nematodes, crustaceans, insects, and fish

“…Some species of reptiles may arrest development at up to three stages of development: one during early preoviposition development, a second (and most common) during late gastrulation, and perhaps a third in a prehatching embryo (55). Shark diapause occurs in early embryos at the blastodisc stage (190). Among the teleosts, diapause has been reported in autumn-spawning bitterling (98), and in the annual killifishes (197,198).…”

Reproductive cycle and maternal–embryonic nutritional relationship of shovelnose guitarfish Pseudobatos productus in the Gulf of California

“…Marquez‐Farías () did not find evidence to support the occurrence of this phenomenon in P. productus from the eastern region of the Gulf of California. The phenomenon of embryonic diapause has been described for many elasmobranch species (Waltrick et al ., ), including species in the genus Rhinobatos . Even though this trait does not occur in all the species, the genus appears to have pre‐disposition to easily evolve on this trait (Waltrick et al ., ).…”