title: The larval nervous system of the penis worm Priapulus caudatus (Ecdysozoa).
abstract: The origin and extreme diversification of the animal nervous system is a central question in biology. While most of the attention has traditionally been paid to those lineages with highly elaborated nervous systems (e.g. arthropods, vertebrates, annelids), only the study of the vast animal diversity can deliver a comprehensive view of the evolutionary history of this organ system. In this regard, the phylogenetic position and apparently conservative molecular, morphological and embryological features of priapulid worms (Priapulida) place this animal lineage as a key to understanding the evolution of the Ecdysozoa (i.e. arthropods and nematodes). In this study, we characterize the nervous system of the hatching larva and first lorica larva of the priapulid worm Priapulus caudatus by immunolabelling against acetylated and tyrosinated tubulin, pCaMKII, serotonin and FMRFamide. Our results show that a circumoral brain and an unpaired ventral nerve with a caudal ganglion characterize the central nervous system of hatching embryos. After the first moult, the larva attains some adult features: a neck ganglion, an introvert plexus, and conspicuous secondary longitudinal neurites. Our study delivers a neuroanatomical framework for future embryological studies in priapulid worms, and helps illuminate the course of nervous system evolution in the Ecdysozoa.
authors.affiliation: Sars International Centre for Marine Molecular Biology, University of Bergen, Thormøhlensgate 55, Bergen 5008, Norway chema.martin@uib.no.
authors.forename: José M
authors.identifier: http://orcid.org/0000-0002-2572-1061
authors.initials: JM
authors.lastname: Martín-Durán
authors.affiliation: Department of Neuroscience, School of Mind, Brain, and Behavior, University of Arizona, Tucson, AZ 85721, USA.
authors.forename: Gabriella H
authors.identifier: http://orcid.org/0000-0002-0075-4975
authors.initials: GH
authors.lastname: Wolff
authors.affiliation: Department of Neuroscience, School of Mind, Brain, and Behavior, University of Arizona, Tucson, AZ 85721, USA Center for Insect Science, University of Arizona, Tucson, AZ 85721, USA.
authors.forename: Nicholas J
authors.identifier: http://orcid.org/0000-0002-1115-1774
authors.initials: NJ
authors.lastname: Strausfeld
authors.affiliation: Sars International Centre for Marine Molecular Biology, University of Bergen, Thormøhlensgate 55, Bergen 5008, Norway andreas.hejnol@uib.no.
authors.forename: Andreas
authors.identifier: http://orcid.org/0000-0003-2196-8507
authors.initials: A
authors.lastname: Hejnol
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002490:Central Nervous System / Q000254:growth & development* / Q000378:metabolism; D019835:FMRFamide / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D007448:Invertebrates / Q000033:anatomy & histology* / Q000196:embryology / Q000254:growth & development*; D007814:Larva / Q000033:anatomy & histology / Q000254:growth & development; D018978:Molting / Q000502:physiology; D059326:Serotonergic Neurons / Q000166:cytology / Q000502:physiology
chemical_list: D019835:FMRFamide
keywords: Ecdysozoa; Priapulida; arthropoda; larva; nematoda; nervous system