Meeting Abstract
Spionid annelids are small (1 mm–5 cm) tubiculous (tube-dwelling) worms with a pair of long palps, that dominate shallow benthic sediments. Studies on annelid development are relatively extensive, although spionid developmental diversity has not been investigated with confocal laser scanning technology. Here, we describe development of musculature, ciliation patterns and serotonergic-positive elements of the nervous system during larval formation in Pseudopolydora sp. Adult worms were collected from the Indian River Lagoon in Florida during summer of 2017, and checked for egg capsules. Larval stages were isolated and prepared for compound and confocal laser scanning microscopy. Preliminary analyses show progressive anterior-posterior development of musculature associated with chaetal sacs, digestive system and larval body, as well as serotonergic nerves in the brain, circumesophageal connectives, and both cell bodies and axons along a pair of ventral nerve cords with posterior growth cones. Serotonergic elements also are associated with the chaetal sacs, and in planktotrophic larvae, left and right ventral cords connect in a looping pattern, anterior to the pygidium. Ciliation is extensive and includes multiple compound ciliary cells around the head, on and within the stomodeum and gut, and on the pygidium. Completely circularized trochal bands were not observed in these larval stages. Although developmental studies in annelids have increased over the last decade, the most detailed studies were performed with laboratory cultures of non-model species (e.g. Platynereis dumerilii, Capitella teleta). Comparative studies using confocal microscopy with understudied groups will broaden our understanding of evolutionary developmental patterns across Annelida.
