The Star of the Clean Up Crew

The common Brittle Star is just that, very common indeed. In fact, there are places in the Caribbean where more than 30 of these stars have been found in an area roughly three feet square. There are stars in the same family that have been reported in densities nearing 1000 stars in the same amount of space!!! Sources vary on how Brittle Stars get their name. Some say it is from their brittle appearance, but others (and this seems more likely) say the name comes from the stars ability to autotomate.

Oxford says Autotomy is “casting off of a part of the body by an animal under threat”. All Brittle Stars have this ability to “lose” a leg at various points on the leg and also have the ability to regenerate the limb later. This allows them time to get away from a predator who might otherwise eat the whole star. In a wide spectrum of studies, from 40% to 100% of the stars counted were missing one or more limb.

In a similar vein, Ophiocoma echinata has the ability to reproduce asexually, by basically emptying out its insides and splitting itself in half, then regenerating the missing half on each side of the split. They are also capable of sexual reproduction, in a much less dramatic event. Sperm and eggs are released into the water column where external fertilization happens. There is a larval period before they turn into recognizable, but really small, brittle stars via a process called metamorphasis.

In the home aquarium Brittle Stars are very useful scavengers for fish and reef tanks alike. They can trap floating detritus in a mucus web between the spines on their legs, but they also move about searching under rock, sand and in crevasses for food. They can live in a tanks as small as 20 gallons without much issue if they are more frequently feed supplemental foods. A better size would be 55 gallons and up, where there is more rock and more hiding places for uneaten food and fish waste to collect. Other than avoiding tankmates with a penchant for eating brittle stars (looking at you Harlequin Tuskfish) and avoiding copper, there isn't a ton of specific husbandry that one needs to direct at keeping brittle stars. If you can provide reasonably tropical temperatures, an occasional nocturnal feeding and avoid copper, your star will help you keep your aquarium clean for a long time to come.