Igama elithi "abactinal" liyisichasiso esisetshenziswa ngokuyinhloko kubhayoloji, ikakhulukazi uma kubhekiselwa kuma-echinoderms (njenge-starfish nama-sea urchins). Kubhekiselwa ohlangothini noma ebusweni besilwane obuphambene nomlomo waso noma indawo yomlomo. Ikakhulukazi, iphathelene nendawo engaphezulu ye-echinoderm, evamise ukusetshenziselwa ukuzivikela noma ukuhambahamba.
