Embryogenesis and larval development of the seastar Astropecten armatus

Astropectinid seastars typically develop as either feeding bipinnaria larvae or nonfeeding, barrel-shaped larvae. Understanding the direction and frequency of evolutionary transitions between these larval nutritional modes requires knowledge of the distribution of developmental diversity in the family, but the development of only a few astropectinids is known. Here we describe embryogenesis, larval development, and metamorphosis of Astropecten armatus, an astropectinid common in soft-sediment subtidal habitats in southern California. Adults were reproductively mature all year except during the winter months (December–February). Oocytes averaged 137 μm in diameter, the smallest reported in the genus. Fertilized oocytes developed into feeding bipinnaria larvae that fed in the plankton for at least 4 weeks, and in some cases up to 33 weeks, before metamorphosis. The tube feet of juveniles were adhesive, but lacked suckers, contrary to some previous descriptions of suckered tube feet in the juveniles of paxillosidans.