This species (Ophionereis annulata) is common in the lower to middle intertidal zone.In this environment, adults are commonly found living underneath rocks, in various types of algae, or in the sand (Ricketts 155). Juveniles are often found in sponge beds or among masses of barnacles (Morris 184).
Experiments have determined that individuals of Ophionereis Annulata living in the Mexican Pacific are the preferred hosts of the scale worm Malmgreniella cf. variegate (Polychaeta, Polynoidae). The worm shows differing behaviors based on the level of light (Granja-Fernandez, et al. 86).
Upon approaching Ophionereis annulataunder daylight conditions the worm climbs onto the dorsal arm plates of the brittle star before immediately moving to the ventral plates, before crawling to the oral side of the center disk (Granja-Fernandez, et al. 87). Under low light conditions the worm remains on the dorsal side of Ophionereis annulata, and takes up residence on the aoral side of the central disk.
In all trials conducted chose Ophionereis annulata as its host over Ophiocoma aethiops, and Ophiocoma alexandri, two similar species of brittle stars with overlapping ranges(Granja-Fernandez, et al. 89).
Feeding is accomplished either by grasping food with the tip of the arm, then coiling the whole arm to bring it to the mouth, or by transporting particles to the mouth with the elongate tube feet (Ricketts 154). These two methods are used if the food particles are comparativelylarge, or small, respectively.
The arms of juvenile Ophionereis annulataare in general more flexible, and thinner in proportion to the size of their main disk, than those of adult specimens. (Morris 184).
Unlike the majority of species belonging to the Ophiuroid family, adult specimens of Ophionereis annulata move with a “stepping action” of their podia rather than by whole arm movements (Ricketts 155).
Ophionereis annulata larvae have the barrel like shape, and transverse bands of cilia characteristic of vitellaria larvae. They also subsist on yolk, as vitellaria larvae do, rather than feeding (Hendler 431). They are differentiated from most vitellaria larvae, however in that they have the vestiges of the pluteus-like skeleton that is typically only found in feeding, ophiopluteus, larvae.
The presence of this vestigial skeleton, but not the arms, digestive tract, or single ciliary band, typically found in ophionereisannulata larvae suggests that this species diverged from its feeding common ancestormore recently than some related species such as ophionereissquamulosa, which have no trace of a larval skeleton (Hendler 437).
