Mariano I. Martinez

Echinoderms from Argentina: Biodiversity, Distribution and Current State of Knowledge

This chapter reviews the research on echinoderms that occur in the waters of Argentina. One hundred and thirty-four echinoderm species have been recorded. Two species of Crinoidea, 58 Asteroidea, 32 Ophiuroidea, 16 Echinoidea, and 26 species of Holothuroidea. The variety of marine environments and the main oceanographic processes in the region are described. Comprehensive information regarding historical and recent echinoderm research is included. A review of the biological, ecological, and chemical research of species inhabiting the Argentine Sea is also presented. Until recently studies on echinoderms in Argentina were very limited. Further studies should be carried out to increase knowledge of the biology and ecology of the fauna. In addition, systematic and phylogenetic studies of Asteroidea, Ophiuroidea and Holothuroidea are needed. Echinoderm fisheries have been sporadic occurring only in the Beagle Channel, especially for the local market. Benthic disturbance resulting from bottom trawling fisheries at various localities seems to be a major threat to echinoderms in the Argentine Sea.

Reproduction of the sea urchin Arbacia dufresnii (Echinoidea: Arbaciidae) from Golfo Nuevo, Argentina

Arbacia dufresnii is a common and abundant sea urchin in Argentinean waters. The gonad index cycle was studied for this species in Golfo Nuevo, Patagonia, from May 2001 to March 2003. Comparative studies of gonad index and gonad histology were performed for the three years of 2001, 2002 and 2003. The gonad index reflects gonadal stages, and the results showed two spawning peaks for the studied period. The first spawning event occurred during spring and a second major spawning occurred in summer. Proliferation and differentiation of gametes, and the presence of mature gonads were synchronous among males and females. Male and female individuals spawned synchronically. Gonad resorption was observed for males and females. Histological examination data reflected gonad index analysis, providing together a good estimation of the reproductive cycle of A. dufresnii. Statistical analyses showed a positive correlation between gonad index and photoperiod. The mean fresh oocyte diameter observed was 8 7 . 1 μm (SD = 1 . 3 μm) with a jelly coat of 12.7 μm (SD = 0.9 μm), which corresponds to planktotrophic larval development.

Benthodytes violeta , a new species of a deep-sea holothuroid (Elasipodida: Psychropotidae) from Mar del Plata Canyon (south-western Atlantic Ocean)

A new species of elasipodid holothuroid, Benthodytes violeta sp. nov., is described from the Mar del Plata Canyon off Buenos Aires Province (around 38ºS-54ºW). It was taken at four locations at depths ranging from 1500 to 1950 m. This new species has a violet gelatinous body of up to 200 mm in length, with eight pairs of dorsal appendages, lateral festooned edges and four rows of tube feet ventrally. Body wall ossicles comprise rods and crosses with three or four arms and a central bipartite apophysis borne on the primary cross; tentacles and gonad deposits comprise rods and crosses with three and four arms. This is the first report of a holothuroid from the Mar del Plata Canyon area.

A new species of Havelockia Pearson, 1903 from the Argentine Sea (Holothuroidea: Dendrochirotida: Sclerodactylidae)

Havelockia pegi sp. nov., is here described from shallow waters of the Argentine Sea. This new species is distinctive in the purple colouration of its tentacles, scarcity of body wall ossicles and the presence of rosette-shaped ossicles in both the introvert and the tentacles. It is not closely related to any of its congenors. This is the first record of a true sclerodactylid from Argentina. Thandarum hernandezi Martinez & Brogger, 2012, described in the family Sclerodactylidae, is now classified in the family Sclerothyonidae.