Anthozoa (corals & anemones) are interesting animals that live exclusively in seas and oceans. Since they are regarded as sessile organisms, their nervous system is not very advanced. In a previous post, I mentioned that all cnidarians have two diffuse neural nets, and that is true for Anthozoans as well. Multipolar nerve net neurons are connected with synapses, and they also possess sensory cells that are particularly numerous around the mouth and on the tentacles.
One paper investigated traveling of electrical waves in a coral nerve network in coral colonies in genus Palythoa. It was experimentally observed that this electrical wave spreads at the constant speed from the site of simulation. Furthermore, peptidergic neurons (the ones using neuropeptides to communicate) were also noted in Anthozoa.
Nematostella vectensis, also known as starlet sea anemone, is a species of Anthozoa that is known as a model organism – its genome and development have been carefully studied, including its nervous system. In this species, oral and pharyngeal nerve rings have been reported, as well as longitudinal tracts of neurites (neurites are usually axons or dendrites). These findings would suggest that some groupings of neural cells exist in at least some Anthozoan species after all. Sensory neurons, interneurons, motorneurons, and neurosecretory‐like gland cells were also reported to exist in N. vectensis.
Note: in case I didn’t mention this before, cnidocytes are often considered neural cells because they display mechanosensory properties and calcium dependent neural‐like properties as well.
Literature & more information:
Habdija et al: Protista-Protozoa, Metazoa-Invertebrata, Alfa, 2011, Zagreb
The rise of the starlet sea anemone Nematostella vectensis as a model system to investigate development and regeneration
Cnidarians and the evolutionary origin of the nervous system
Model of traveling waves in a coral nerve network