Development and distribution of the peptidergic system in larval and adult Patiriella: Comparison of sea star bilateral and radial nervous systems

Abstract

Development of the larval peptidergic system in the sea star Patiriella regularis and structure of the adult nervous system in Patiriella species were documented in an immunofluorescence investigation using antisera to the sea star neuropeptide GFNSALMFamide 1 (S1) and confocal microscopy. P. regularis has planktotrophic development through bipinnaria and brachiolaria larvae. In early bipinnaria, two groups of immunoreactive cells appeared on either side of the anterior region and proliferated to form a pair of dorsolateral ganglia. The ganglia gave rise to fine varicose fibres that innervated the preoral and adoral ciliated bands. Peptidergic cells also innervated the postoral ciliated band, and a nerve tract connected the pre- and postoral bands. Fully developed bipinnaria had a well-developed peptidergic system, the organisation of which reflected the bilateral larval body plan. As the brachiolar attachment complex differentiated at the anterior end, the ganglia became positioned on either side of the anterior projection, from which they innervated the complex. It is suggested, based on the distribution of S1-like immunoreactivity in association with ciliary and attachment structures, that the peptidergic system functions in modulation of feeding, swimming, and settlement. The larval peptidergic system degenerates as the larval body is resorbed during metamorphosis. In adults, S1-like immunoreactivity was intense in the axonal region of the ectoneural nervous system and in hyponeural perikarya. Immunoreactive cells in the neuroepithelium connected with the surface and may be sensory. Examination of immunoreactivity in several Patiriella species attests to the highly conserved organisation of the peptidergic system in adult asteroids.

Expression of tryptophan 5‐hydroxylase gene during sea urchin neurogenesis and role of serotonergic nervous system in larval behavior

“…In echinoderm larvae, on the other hand, the axons from serotonergic and peptidergic neurons distribute closely to the ciliary bands Burke, 1986, 1987;Moss et al, 1994;Beer et al, 2001;Byrne and Cisternas, 2002). However, the neurotransmitter secretion and the presence of their receptors have not been reported.…”

Hemichordata

“…Of course, taxon-specifi c traits are present, but the general neural body plan of an apical organ with sensory cells resting in the apical ciliary band and nerves along the neotroch is present (Hay-Schmidt 2000; Burke et al 2006 ;Byrne et al 2007 ). As in hemichordate tornariae, the echinoderm larval nervous system contributes little if anything to the pentameral nervous system of the juveniles (Byrne and Cisternas 2002 ;Cisternas and Byrne 2003 ;Nakano et al 2006 ). Because of numerous resemblances between the morphology of hemichordate tornariae and echinoderm larvae, they have been grouped together under the term dipleurula-type larvae (Metschnikoff 1881 ).…”

Development of nervous systems to metamorphosis in feeding and non-feeding echinoid larvae, the transition from bilateral to radial symmetry

“…Evolution of non-feeding larvae is associated with deletion of the ciliary bands, although they swim propelled by their ciliary cover (Bisgrove and Raff 1989;Morris 1995;Byrne et al 2001;Byrne and Cisternas 2002). There is a single study of the nervous system of the vestibula larva, documented for the larva of Heliocidaris erythrogramma (Bisgrove and Raff 1989).…”