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

RIVADENEIRA, P.R.; PASTORINO, G.; TESO, V.; MARTINEZ, M.I.; LAURETA, D.; BERECOECHEA, J.J.; BROGGER, M.I.; FLORES, J.N.; PERTOSSI, R.M.; SÁNCHEZ, N.; PENCHASZADEH, P.E.

Monterey, California

Simposio; 15th Deep-Sea Biology Symposium; 2018

Deep-Sea Biology Society

Biological deep-sea research off Argentina (beyond 1200 m) started since2012 with focus in the Mar del Plata submarine canyon (up to 3500 m). Many ofthe more than 200 species found of benthic cnidarians, mollusk and echinodermsare being studied and new species are being described. Previous studies fromdifferent authors have pointed out the unusual proportion of species showingprotective adaptations for its offspring in the Southern Sea, particularly inAntarctica. Many new cases were observed in the study area in different phylashowing some kind of protected development, with avoidance of a free swimminglarval stage. Among Cnidaria, oocyte gigantism was found in the black coral Dendrobathypathes grandis with adiameter of up to 1.5 mm, when oocytes in Antipatharia are usually under 0.2mm. Many deep-sea gastropods show encapsulated direct development, by thepresence of supplementary food for the embryo as nurse eggs, adelphophagia (Buccinidae,Calyptraeidae), proteins in the intracapsular liquid (Naticidae, Volutidae), orby means of gigantic eggs of about 1.8 mm in diameter (Cochlespiridae). Peculiaregg mass morphologies are reported, i.e. in the moon snail Bulbus carcellesi where the egg capsules are the largest everrecorded for this family (8.8?14.1 mm in diameter vs 3 mm of the largestpreviously known). Brooding is found in the five classes of Echinodermata. Thesea star Ctenodiscus australisprotect its broods in the dorsal side between paxillae; the crinoid Isometra vivipara shows two phases, one witheggs brooded in a marsupium and a second phase in the cirrus. In some seacucumbers (Cladodactyla crocea, Psolus patagonicus and Psolus lawrencei) broods could be foundin pouches, sole or brooding chambers. The sea urchin Austrocidaris canaliculata, protect their youngs in the apicalsystem. Brooding chambers have been also reported in ophiuroids as Astrotoma agassizi and Ophiochondrus stelliger. All these newevidences are willing to contribute to the understanding of the scenery for somany cases of parental care and the avoidance of planktonic larvae in the southwesternAtlantic.