Biologia reprodutiva de Sabellaria wilsoni (Polychaeta: Sabellaridae) na ilha de Algodoal-Maiandeua (Pará)

Abstract

The Polychaeta Sabellaria wilsoni occurs from the Gulf of Mexico to Argentina, building sandy reefs from the intertidal zone to 25 m depth. These reefs play an important role in structuring and functioning of sandy beach ecosystems in the Amazon Coast. This work studied the reproductive biology of S. wilsoni in Algodoal Island (PA, Brazil), describing sex ratio, gametogenic process and breeding period. Sampling occurred monthly between May 2008 and April 2009. In the laboratory 100 individuals were randomly chosen and measured (total length – from the operculum to the beginning of the anal funnel); and from these, 20 specimens were prepared for histological studies. Slides were observed under optical microscope to describe reproductive structures, and to determine sex and maturation stage (based on a four grade scale). The size of organisms ranged from 4.5 ± 1.89 mm to 11.5 ± 2.83 mm, with females larger and more numerous than males (sex ratio 0.6:1 - M:F). Female gametes develop on projection of blood vessels and are subsequently released into the coelom. In males spermatogenesis is associated with intersegmental septa wall, and sperm is released into the coelom. Gametes are released to the environment through nephridia and fertilization is external. Reproduction occurs all year round with peaks on September-November and March-April. The main cues to reproduction are an increase in hydrodynamics on August, as an adaptation of the Polychaeta to the future reef destruction, which occurs between October and November; and an increase of space available for colonization, after the reef destruction.