Phasmids are unicellular
sensilla
A sensillum (plural ''sensilla'') is an arthropod sensory organ protruding from the cuticle of exoskeleton, or sometimes lying within or beneath it. Sensilla appear as small hairs or pegs over an individual's body. Inside each sensillum there are ...
in the lateral tail region of certain species of
nematode
The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...
s. They are similar in their structure to
amphid sensilla, but smaller. Phasmid
neurons were recently shown to function in modulation of
chemorepulsion behavior.
References
Nematode anatomy
{{Nematode-stub