Zoological Studies

Vol. 50 No. 4, 2011

Oocyte Production, Fecundity, and Size at the Onset of Reproduction of Tripalea clavaria (Cnidaria: Octocorallia: Anthothelidae) in the Southwestern Atlantic

Adriana C. Excoffon1, María L. Navella1, Fabián H. Acuña1,2,*, and Agustín Garese1,2

1Departamento de Ciencias Marinas, Facultad de Ciencias Exactas y Naturales, Univ. Nacional de Mar del Plata, Funes 3250, Mar del Plata 7600, Argentina
2National Council for Scientific and Technical Research of Argentina (CONICET), Rivadavia 1917, Buenos Aires, Argentina

Adriana C. Excoffon, María L. Navella, Fabián H. Acuña, and Agustín Garese (2011) The octocoral Tripalea clavaria is a gonochoristic species distributed in the southwestern Atlantic from Rio de Janeiro to the Magellan Strait and is restricted to waters with temperatures of < 20°C. Female colonies are significantly more abundant than males, and their gonads are present throughout the entire year. Male fertile colonies were found only in Dec.-June, because the spermatogenic cycle is shorter than oogenesis, as is characteristic of other octocorals. Fertilization is probably internal, taking place within polyps of female colonies in Mar.-May. Planulae of T. clavaria were found in Apr.- June. The length of larvae was 554-1980 µm, and a maximum of 4 planulae was observed per polyp. The high number of large oocytes per polyp implies that this species allocates most of it energetic resources to sexual reproduction. Regarding the variability of volume of oocytes per polyp, the lowest value was 1.35 × 10-5 mm3, and the highest was 0.17 mm3. Although the reproductive features of T. clavaria are similar to those of other gorgonian octocorals, it has some exceptional features. Despite having small and unbranched colonies, this species exhibits a small colony size at 1st reproduction (2.7 cm) and is highly fecund, producing high numbers of large oocytes compared to other octocorals. Such reproductive traits could explain its successful recruitment on the limited available substrate of rocky outcrops, often characterized by strong currents and turbulence.

Key words: Octocoral, Tripalea clavaria, Sexual reproduction, Southwestern Atlantic.

*Correspondence: Tel: 54-223-4753554. Fax: 54-223-4753150. E-mail:facuna@mdp.edu.ar