Protected development in deep-sea invertebrates. The rule in the southwestern Atlantic?

PAMELA RUTH RIVADENEIRA; GUIDO PASTORINO; VALERIA TESSO; MARIANO I. MARTÍNEZ; DANIEL LAURETTA; JUAN JOSÉ BERECOECHEA; MARTÍN IGNACIO BROGGER; JONATHAN NAHUEL FLORES; RENATA PERTOSSI; SANCHEZ, NOELIA CAROLINA; PABLO E. PENCHASZADEH

Monterey, California

Congreso; Deep-Sea Biology Symposium 2018 (DSBB 2018); 2018

Deep-Sea Biology Society (DSBS)

Biological deep-sea research off Argentina (beyond 1200 m) started since 2012 with focus in the Mar del Plata submarine canyon (up to 3500 m). Many of the more than 200 species found of benthic cnidarians, mollusk and echinoderms are being studied and new species are being described. Previous studies from different authors have pointed out the unusual proportion of species showing protective adaptations for its offspring in the Southern Sea, particularly in Antarctica. Many new cases were observed in the study area in different phyla showing some kind of protected development, with avoidance of a free swimming larval stage. Among Cnidaria, oocyte gigantism was found in the black coralDendrobathypathes grandis with a diameter of up to 1.5 mm, when oocytes in Antipatharia are usually under 0.2 mm. Many deep-sea gastropods show encapsulated direct development, by the presence of supplementary food for the embryo as nurse eggs, adelphophagia (Buccinidae, Calyptraeidae), proteins in theintracapsular liquid (Naticidae, Volutidae), or by means of gigantic eggs of about 1.8 mm in diameter (Cochlespiridae). Peculiar egg mass morphologies are reported, i.e. in the moon snail Bulbus carcellesi where the egg capsules are the largest ever recorded for this family (8.8?14.1 mm in diameter vs 3 mm of the largest previously known). Brooding is found in the five classes ofEchinodermata. The sea star Ctenodiscus australis protects its broods in the dorsal side between paxillae; the crinoid Isometra vivipara shows two phases, one with eggs brooded in a marsupium and a second phase in the cirrus. In some sea cucumbers (Cladodactyla crocea, Psolus patagonicus, and Psolus lawrencei)broods could be found in pouches, sole or brooding chambers. The sea urchin Austrocidaris canaliculata, protect their young in the apical system. Brooding chambers have been also reported in ophiuroids as Astrotoma agassizi and Ophiochondrus stelliger. All this new evidence contributes to the understanding of the scenery for so many cases of parental care and the avoidance of planktonic larvae in the southwestern Atlantic.