Continuous and non-seasonal reproductive cycle of the alien species Diopatra neapolitana (Onuphidae, Annelida) in a tropical bay of SW Atlantic

Abstract

Taxonomic studies on onuphids collected at Baía do Araçá (Araçá Bay), Southwestern Atlantic, Brazil, using morphological and molecular data, confirmed that members of Diopatra neapolitana Delle Chiaje, 1841 occur in the area, although that species was originally described from the Gulf of Naples, Italy, Mediterranean Sea. Following the confirmation of the identity of the species, an annual study, with monthly samplings, was conducted, to investigate the reproductive cycle of those animals, based on the presence of coelomic gametes. The specimens were found to have asynchronous, non-seasonal reproduction, with reproductive cycle regulated rather ontogenetically than seasonally. We also studied the spermatogenesis of the specimens from Araçá Bay and noticed that it is characterized by the presence of cytophores, as also occurs in many other polychaetes; after the spermiogenesis, spermatozoids can be stored free in the coelomic fluid, or in clusters, the spermatic morulae. The sequential hermaphroditism, characterized by the presence of spermaducal papillae, showed intraspecific variation on sexual maturity and gender transition, resembling a sequential hermaphroditism, with gender transition occurring earlier in SW Atlantic specimens than among a Spanish population of D. neapolitana.