Reproduction and developmental stages in the crinoid Isometra vivipara Mortensen, 1917 from the southwestern Atlantic

PERTOSSI, R.M.; BROGGER, M.I.; PENCHASZADEH, P.E.; MARTINEZ, M.I.

POLAR BIOLOGY

SPRINGER

Año: 2019 vol. 42 p. 807 - 816

0722-4060

Isometra vivipara Mortensen, 1917, which was described one hundred years ago, represents a particular case within thefeather stars of the southwestern Atlantic Ocean. This is a dioecious species in which the oocytes are fertilized in the ovaryand not externally as in other species. Some authors have pointed out that I. vivipara stores spermatozoa in the genital pinnules of the female, although there is still no detailed data on how they reach the pinnule. Besides, this species is characterized by possessing a second sexually dimorphic trait and presents two incubation stages: one in the genital pinnules, andthe second one attached in the cirri of the mother. In the present work, the reproduction and developmental stages of the I.vivipara were studied. Samples were taken from two cruises aboard the B/O ?Puerto Deseado? to Burdwood Bank/MPANamuncurá at 84?642 m depth, during March/April 2016 and April/May 2017. Four developmental stages were recognized:Embryo, Doliolaria larvae (inside the brood pouches), Cystidean, and Pentacrinoids (attached in the cirri of the mother).In addition, histological analysis showed that fertilization in I. vivipara could occur between the ovary and the marsupium.The egg measurements reached 0.35 mm in diameter?on of the largest egg size within South America and Antarcticacomatulids?whereas for the larvae the largest registered diameter was 0.77 mm. These results are compared and discussedwith all the available information of comatulids from South America and Antarctica.