Development of the deep-sea viviparous quill worm Leptoecia vivipara (Hyalinoeciinae, Onuphidae, Annelida)

Abstract

Development of Leptoecia vivipara, a brooding deep-sea onuphid polychaete with a circum-Antarctic distribution, was studied using light microscopy, scanning and transmission electron microscopy, and histology. All specimens examined were brooding viviparous females or juveniles; no male gametes were detected. Anterior segments of juvenile and adult worms bore paired compact ovaries with clusters of vitellogenic oocytes. In adults, the mid-body region formed a chamber containing up to 12 offspring at different stages of development, from oocyte to 13 chaetigers. Mature oocytes freely floated in the coelomic fluid, while embryos and juveniles were enclosed in peritoneal envelopes. Chaetal replacement in juveniles and the morphology of the provisional maxillae are described. Leptoecia vivipara is argued to be a progenetic species with juvenile-like external morphology and accelerated sexual maturation. These traits may have arisen as adaptations to epibenthic life in a high-latitude deep-sea environment affected by seasonal pulses of organic matter. © 2014, The American Microscopical Society, Inc.