Care
Brittle Stars, or ophiuroids, are echinoderms in the class Ophiuroidea, which are closely related to the true starfish (Asteroidea). These fascinating bottom-dwellers are able to move across the substrate with rapidity, on account of their highly flexible, whip-like arms. The flattened central disk is very distinct from the arms and contains a mouth on the underside in addition to all the viscera; the internal organs do not enter the arms as is seen in the Asteroidea. There are currently some 2000 described ophiuroid species worldwide, most of which typically inhabit shallow reef environments, congregating underneath rocks and in small gaps between and amongst sessile invertebrates. Brittle Stars are a favourite with marine hobbyists, on account of their ability to get into unseen crevices that the aquarist cannot reach, cleaning, aerating, and stirring up detritus as they go. Most ophiuroid species are nocturnal, so you won't get to see a great deal of these creatures during daylight hours, except for a tell-tale arm or two protruding out from under the rockwork. A dim moon light that is run during the evening hours will allow you to view your Brittle Stars as they go about their business under the subdued illumination. The vast majority of species are reef-safe and attain a sensible size for keeping in the home aquarium. However, avoid keeping alongside hermit crabs, which may inflict damage. A mature tank with sandy substrate and plenty of rockwork is requisite. Brittle Stars are extremely sensitive to changes in water chemistry and should be acclimatised very carefully and slowly over the course of a few hours via drip acclimatisation, in order not to shock them with any differences in salinity or pH. Please beware of the closely related Green Brittle Star (Ophiarachna incrassara), a predatory species which grows large and has a nasty habit of arching up on the tips of its legs and positioning itself over unsuspecting resting fish at night, suddenly plunging the central disk downwards and trapping the unfortunate prey. It is not known as the 'Green Death' for nothing - avoid.
Feeding
Will scavenge amongst all the nooks and crannies in the aquarium in an ongoing search for food, consuming micro fauna, uneaten fish food, and detritus as they go. Also offer regular supplemental target feedings with meaty fish foods e.g. Mysis shrimp, spirulina-enriched brineshrimp, baby brineshrimp (Artemia nauplii), finely chopped krill etc. Some species also filter feed by raising the arms vertically in the passing water current, catching miniscule food particles with the tube feet (small spines that cover the arms) and passing them along to the mouth.
Breeding
Various species of Brittle Star have been known to reproduce in the home aquarium, with spawning occurring at night, often following a water change/increase in flow. Fertilisation is external. The Brittle Stars will all emerge from their hiding places and stand on the tips of their arms with the central disk raised as high off the substrate as possible. A cloud of gametes will be released from the bursal slits - oocytes from the females and spermatozoa from the males. Mass broadcast spawning of this kind ensures greater success. The resultant embryos hatch into free-swimming planktotrophic larvae and later metamorphose into tiny brittle stars which sink down the bottom where they grow into the adult form. Some species are known to brood developing larvae in the bursae.
