Saltcorner: Article: Q&A

The blue sea star to which you are referring is Linckia laevigata, but despite it's beauty and the frequency with which these animals are imported, there is very little known about the natural history of this animal. It is known that the animal gets it color from a blue pigment called linckiacyanin and some accessory yellow carotenoids which gives the star its rich blue color, but little is known about the exact feeding requirements or biology of the star. There is a fair bit of variation in color among these stars, and there are areas throughout its range where L. laevigata range from blue to brownish or even orange in color. It is unclear whether there is any genetic component of coloration in these animals, however, because a variety of genetic studies in Australia show no significant differences among populations dominated by different color morphs.

You don’t tell me anything about your tank, but I will assume that you have a reef tank to which you plan to add this star. Hopefully it is a fairly large reef aquarium (50g or more), because these stars rarely do well for long periods of time in small tanks. There is very little known about the natural history of these stars, despite the fact that Linckia is one of the most common and obvious sea stars on Indo-pacific reefs. L. laevigata is thought to be primarily an opportunistic scavenger, perhaps even saprophytic (preferring to consume dead items as they begin to decay), but as also been observed to feed on algae and microbial films. L. multifora, (the Red Linckia) on the other hand, is thought to derive most of its nutrition from suspension feeding, although it has also been observed to consume microalgae and microbial films. In both cases, much of the nutrition for these species probably comes from diatoms, bacteria and other filming organisms found on live rock. These stars often reject any attempts at artificial feeding and will typically crawl off pieces of fish, shrimp, squid or prepared food that other stars (such as the popular Chocolate Chip star, Protoreaster nodosus) will readily consume. Because they generally prefer surface films, they are unlikely to do well in a tank that is recently (i.e., < 6 months) set up, or one in which there is not enough live rock for them to continually find new surface films from which to graze. Another consideration is that these animals can get quite large (30cm or more across) and the amount of food they require will increase with their size -- obviously the amount of established rock in your tank will have to be quite large to support a grazing star which is about 30 cm in diameter!!

You do not really have to worry about compatibility beyond the basic tank requirements for feeding, because these animals are not aggressive (eating slime on rocks does not threaten many animals in a reef tank), and the stars themselves are chemically defended from predators (they possess antifeedon compounds called saponins). These saponins are highly effective in discouraging predators, and Linckia actually shares some of these compounds with the highly distasteful Crown of Thorns starfish (Acanthaster planci). Unlike the chemical defenses of sea apples (Pseudocolchirus spp.) and some sponges and tunicates, however, these chemical defenses do not pose a risk to tank-mates, and should not be a concern to anything other than predators which try to nip at the star.

Assuming that you can provide for the requirements of the star, and are set on doing so, there are a few considerations before buying one. First, make sure that the star is active, firm to the touch and without any discolored patches across the body. As I mentioned above, there are several species of Linckia, and not all of them are blue, or even a single color. It is hard to recognize discolored patches from mottled colors on some animals, but unless you are familiar with the coloration of the species, it is best to err on the side of caution and avoid mottled Linckia. More so because there are a multitude of similar stars occasionally misidentified as “Linckia” offered for sale. Various Fromia species as well as Leiaster, Ophidiaster, Echinaster and Nardoa species are occasionally offered for sale as Linckia in petshops, and I have even seen "Knobby Linkcia" (really the predatory star, Gomophia egyptiaca) offered for sale in a prominent San Francisco fish store. Many of these misidentified "Linckia" are predatory on colonial tunicates, sponges, or other nonmotile marine invertebrates. If you are reasonable confident about the identity of the star, check to see if the animal is at least partially hidden from intense illumination and actively crawls about (it should move on at least an hourly basis). If not, I would wait until you see one that does behave in this way before buying it. Be patient – it often takes a while to find one in really good shape at the local pet shop, but a little patience will be repaid if the animal survives and grows well in your tank. There is nothing quite so disheartening as getting an exciting new animal, only to watch it slowly disintegrate into goo because the animal was not healthy from the beginning.

Another consideration is that these stars are particularly prone to parasitic infections, and in some regions as many as 1/4 of the Linckia are infected with the small parasitic snails (Thyca crystallina). You should check for these snails clinging to or boring into the underside of the arms before you pay for the star. Females of these parasitic snails have a proboscis (elongated mouth) that penetrates the skin of the sea star and sucks the hemolymph (the echinoderm equivalent of blood) almost like a shelled, marine mosquito. Unlike a mosquito, however, the adult snail actually becomes fused to the sea star, and should not be picked off, because it is attached and ripping the snail off will almost certainly result in more damage than leaving the snail attached. Other than a slight alteration in some of the skeletal elements around the proboscis, the main effect of these snails on the star appears to be the loss of tube feet under the snail’s shell (which probably has no effect on the health of the star in the long-term). Although research suggests that these parasitic snails cause little harm to their hosts, their presence is an additional stress that the stars do not need when being moved to an aquarium, and provides a potential vector for infection.

A big problem with these stars, even more so than other echinoderms, is that they ship poorly, and it is important to start with a healthy specimen if you decide to keep one of these animals. Therefore, it is exceptionally important to acclimate this animal carefully (of course, all animals should be acclimated carefully, but it’s particularly important with these stars). If you can find a healthy star, bring it home quickly (long periods of time in a bag are hard for them as well), and then acclimate it to your tank water slowly to minimize the stress on the animal as it is transplanted into your aquarium. Personally, I usually use a drip system to acclimate the animals, but this is a hassle, and most people find the cup method to be much easier. First, float the sealed bag for about 15 minutes to equalize the water temperature. Then, add about 1 cup of water every five minutes until you’ve filled the bag. Once the bag is full, dump half of that water down the drain (not into your tank) and repeat this until the bag is full again (fill the bag at least twice, if not three times before releasing the star). Once you have completed the acclimation, remove the star from the bag (discarding the water left behind), and place the animal onto an open rock area in your tank. The star should promptly adhere to the rock, and then move off in search of a partially shaded area to begin feeding.

Although these stars require extra care in the initial selection, once they are successfully introduced into a large, well established aquarium with plenty of live rock to explore, they are quite hardy and a beautiful addition to any reef aquarium.

L. laevigata has a 28 d planktotrophic larval phase, Acanthaster planci has a 14 d larval phase

Q&A - Linckia

Authored by: Rob Toonen