Comparative embryonic development patterns in three deep-water skates from the southwest Atlantic

Abstract

Embryonic development is a vulnerable and key period during the life cycle of an oviparous elasmobranch. Captivity studies are difficult to carry out on non-coastal species; hence, embryonic development can be analysed from samples collected from the seabed. Here, embryonic development of three shelf and deep-water skates from the southwest Atlantic Ocean, Bathyraja brachyurops, B. macloviana and Amblyraja doellojuradoi was studied. Egg cases containing embryos in different stages were collected from 84 to 1006 m depth in the northern part of the Argentinean continental shelf and continental slope (36°S-41°S), including the Mar del Plata Canyon (38° S). Common development patterns were observed among the three species and also with other skate species previously studied. Anatomical structures and embryo features were similar among species in initial, early and middle stages. Advanced and pre-hatching embryos showed species-specific differences regarding pigmentation and spinulation. This study sheds light on the identification of neonates of shelf and deep-water species, which could be useful to recognize specific nursery areas in the deep ocean. In addition, this embryological comparative study expands the existing database on the different chondrichthyan lineages, thus making a step forward towards understanding of their phylogenetic relationships.