Morphogenesis during sexual and asexual reproduction in Amphipolydora vestalis (Polychaeta: Spionidae)

Abstract

Both sexual and asexual reproduction occur in Amphipolydora vestalis, a small, sponge‐dwelling spionid polychaete. Sexual reproduction occurs through adelphophagy, where offspring are provided with extra‐embryonic yolk in the form of nurse eggs. Ingestion of nurse eggs sustains development until offspring hatch at late larval and early juvenile stages (22 days). Hatched young have an advanced morphology and alternatively crawl and swim, suggesting that a dispersive phase is brief or absent. Asexual reproduction occurs through architomy, in which a parent fragments into 4–6 pieces and each regenerates a complete body plan within 8 days. Asexual propagules remain within the parental tube until growth and differentiation are almost complete. Both reproductive modes were found at the same time in the same population, and asexual fragments often had well developed gametes in the coelom. Both reproductive modes facilitate local recruitment and a reduced dispersal potential. This is the first description of development within the genus Amphipolydora. Aspects of morphogenesis during asexual reproduction suggest that Amphipolydora is closely related to Polydorella, and that architomy in the Spionidae evolved from a widespread ability to regenerate, while paratomy is secondarily derived.

Keywords:

• adelphophagy
• embryogenesis
• larva
• blastema
• regeneration
• Amphipolydora
• spionid
• Polydora complex
• architomy
• paratomy

Notes

Author for correspondence.