A description of the bat star nervous system throughout larval ontogeny.

Larvae represent a distinct life history stage in which animal morphology and behavior contrast strongly to adult organisms. This life history stage is a ubiquitous aspect of animal life cycles, particularly in the marine environment. In many species, the structure and function of the nervous system differ significantly between metamorphosed juveniles and larvae. However, the distribution and diversity of neural cell types in larval nervous systems remains incompletely known. Here, the expression of neurotransmitter and neuropeptide synthesis and transport genes in the bat star Patiria miniata is examined throughout larval development. This characterization of nervous system structure reveals three main neural regions with distinct but overlapping territories. These regions include a densely innervated anterior region, an enteric neural plexus, and neurons associated with the ciliary band. In the ciliary band, cholinergic cells are pervasive while dopaminergic, noradrenergic, and GABAergic cells show regional differences in their localization patterns. Furthermore, the distribution of some neural subtypes changes throughout larval development, suggesting that changes in nervous system structure align with shifting ecological priorities during different larval stages, before the development of the adult nervous system. While past work has described aspects of P. miniata larval nervous system structure, largely focusing on early developmental timepoints, this work provides a comprehensive description of neural cell type localization throughout the extensive larval period.