The reproductive biology of Amathys lutzi, an ampharetid polychaete from hydrothermal vents on the Mid‐Atlantic Ridge

Abstract

Abstract. The reproductive biology of polychaetes includes a diverse array of characteristics that sometimes have been related to features of the habitat and others times appear to be phylogenetically constrained. The reproductive biology of polychaetes from deep‐sea hydrothermal vents is of particular interest, given the continuing supply of food when vents are active and the ephemeral nature of the vent environment. As part of a survey of reproductive attributes of vent polychaetes, we undertook a descriptive study of the anatomy of the ampharetid polychaete, Amathys lutzi, which lives in mucus‐lined tubes attached to mussel shells or rocks at hydrothermal vent sites along the Mid‐Atlantic Ridge. Reproductive features of ampharetids from the Logatchev vent site were examined with serial sections under light microscopy and with transmission electron microscopy. Members of A. lutzi are gonochoric and lack external sexual dimorphism. Gonads are associated with 3 pairs of mixonephridia found laterally in the anterior region of the polychaete. Oocytes undergo extraovarian oogenesis and are released into the coelom in the previtellogenic phase. Maximum oocyte diameter is∼190 μm, suggesting lecithotrophic development. Within individual females, oocyte size‐frequencies suggest the presence of cohorts of maturing oocytes, consistent with periodic release of gametes. There is no evidence for sperm storage in females. Early stages of developing sperm are also found in the coelom; mature sperm fit the general description of ect‐aquasperm. These reproductive characteristics of individuals of A. lutzi are similar to those of the Pacific vent ampharetid, Amphisamytha galapagensis.