Show Summary Details

Page of

Printed from Oxford Research Encyclopedias, Neuroscience. Under the terms of the licence agreement, an individual user may print out a single article for personal use (for details see Privacy Policy and Legal Notice).

date: 30 September 2023

Urochordate Nervous Systemslocked

Urochordate Nervous Systemslocked

  • Kerrianne RyanKerrianne RyanDepartment of Psychology and Neuroscience, Dalhousie University
  •  and Ian A. MeinertzhagenIan A. MeinertzhagenDepartment of Psychology and Neuroscience, Dalhousie University


Urochordates are chordate siblings that comprise the following marine invertebrates: the sessile Ascidiaceae, or sea squirts; planktonic Larvacea; and the pelagic salps, doliolids, and pyrosomes (collectively the Thaliacea), each more beautiful than the next. Tadpole larvae of ascidians and adult larvaceans both have a body plan that is chordate, with a notochord and dorsal, tubular nervous system that forms from a neural plate. Thalaciacea have a ganglion developed from a tubular structure, which has been compared to the vertebrate mes-metencephalic region, and while salps have well developed eyes, other anterior brain components are absent, and the connections within their central nervous system, as well as the neurobiology of other Thaliacea are all little reported. The ascidian tadpole larva is extensively reported, especially in the model species Ciona intestinalis, as is the caudal nerve cord in the larvacean Oikopleura dioica.

Chordate features that share proposed homology with vertebrate features include ciliary photoreceptors that hyperpolarize to light, descending decussating motor pathways that resemble Mauthner cell pathways, coronet cells in the ascidian larva and saccus vasculosus of fishes, the neural canal’s Reissner’s fiber; secondary mechanoreceptors that resemble hair cells; and ascidian bipolar cells that are like dorsal root ganglion cells.


  • Invertebrate Neuroscience

You do not currently have access to this article


Please login to access the full content.


Access to the full content requires a subscription