Reproductive biology and energetics of the brooding sea star Anasterias antarctica (Equinodermata: Asteroidea) in the Beagle Channel, Tierra del Fuego, Argentina

PEREZ, A.; FRAYSSE, C.; BOY, C.C.; EPHERRA, L.; CALCAGNO, J.

REVISTA DE BIOLOGíA TROPICAL

REVISTA DE BIOLOGIA TROPICAL

Lugar: Turrialba; Año: 2017 vol. 65 p. 221 - 232

0034-7744

The brooding sea star Anasterias antarctica is distributed from the coasts of Patagonia to northern Península Antártica. The females of A. antarctica of Beagle Channel, brood their eggs for seven months and do not feed during this period. In both sexes gonadal maturation occurs in summer and gametogenesis, in winter. The endoparasite Dendrogaster argentinensis (Crustacea: Ascothoracica) has been recorded in several species of the genus Anasterias and has been reported as causing castration. The aim of this study was to enlarge knowledge on reproductive biology of the brooding sea star A. antarctica and present an approach to bioenergetics studies. Moreover, it was also studied the prevalence and the possible consequences of the presence parasite D. argentinensis on A. antarctica. Four samplings of adults of A. antarctica were randomly collected in Tierra del Fuego National Park, Argentina, in May, August and October of 2009 (brooding period) and January 2010 (non-brooding period). Individuals sampled during the brooding period were classified as brooding females, non-brooding females, and males. Individuals sampled during the non-brooding period were classified as mature females, non-mature females and males. The gonad (GI) and pyloric caeca index (PCI) were calculated as organ wet weight (g) x 100/total wet weight (g). Each individual was sexed by the microscopic examination of gonads. The prevalence of infection with D. argentinensis was also estimated. Sex ratio, brooding females/non-brooding females and mature females/non-mature females´ ratios did not differ significantly of 1:1. The male GI reached maximum values in January, when most individuals were sexually mature. During brooding period, the GI of non-brooding females reached its maximum during October when it was significantly higher than those of brooding females. The PCI was minimum in October and were lower in brooding females than non-brooding females (August and October). During non-brooding period, mature females had a significantly higher GI than non-mature females. The PCI did not vary significantly in males or between females during non-brooding period. Prevalence of D. argentinensis in A. antarctica was 11.06% and all specimens without gonads were parasitized. Towards the end of the brooding period, non-brooding females showed a higher GI than the brooding females, being explained by proliferation and increase of the oocytes size of the non-brooding females. Mature females showed a raised GI with presence of mature oocytes, while the non-mature females exhibited previtelogenic oocytes. On the other hand, males showed synchronicity in reproductive condition. The females that have not brooded, presented a process of active gametogenesis reaching the summer with a high GI and becoming mature females, while the females that have brooded probably have not energy enough to grant a new gonadal maturation and face a new period of incubation. The pyloric caeca would be performing the role of a reserve organ in the brooding females, decreasing its size during the brooding period. D. argentinensis was recorded in sea stars lacking gonads therefore these infected hosts could have been castrated.