Care
The Longspine Heart Urchin is known from sandy intertidal areas and seagrass beds, to depths of 60m (197ft). These curious creatures often congregate in large numbers, feeding amongst the substrate on detritus and dead organic matter. Longspine Heart Urchins are seldom seen in the trade, but make very interesting aquarium specimens when they are available. Their main requirements are mature, spacious aquaria with open expanses of crushed coral/coarse sand at least 10cm (4") in depth, where they can happily forage about for food and bury beneath the surface as and when they choose. Avoid really fine sand or muddy substrates though, as there is a danger that they may suffocate. The specific gravity of the water should be stable, and it is of utmost importance that the urchins are acclimatised very, very carefully, ideally using the drip method "“ too rapid a change in salinity can be fatal. Never expose the urchins to air. Excellent water quality is required at all times, so powerful filtration, water movement and protein skimming should be considered essential. Urchins do not take well to even the smallest changes in water chemistry. These fascinating creatures belong to the Class Echinoidea and are known as 'irregular urchins/echinoids' (the Irregularia); they are very closely related to the Sand Dollars. The oval to heart shaped body is dorsoventrally compressed and mostly white, with an obvious front and back end (which is not seen in regular Sea Urchins). The internal skeleton is formed from large ossicles that are fused together into plates in multiples of five, and is hollow but rigid. Heart Urchins lack the specialised jaws that the globular Sea Urchins have. The sparse long spines are directed backwards, are banded brown/orange and white, and are nestled in amongst the abundant shorter, moveable white spines. It is these shorter spines which aid locomotion and allow the Heart Urchin to dig into the substrate. The spines are not venomous, but they can inflict a painful wound (particularly if a small barb breaks off), so always take care when handling or carrying out maintenance in the aquarium. The petaloid, a series of tiny holes in the skeleton that form a petal shape on the dorsal surface, is brown in colour, and tiny tube feet emerge through these holes so that the urchin can breathe through them. There are usually four obvious petals with the fifth being somewhat reduced and found towards the posterior of the animal. On the underside is a pale orange petaloid around the mouth. Observe these largely nocturnal animals carefully to ensure that they can move freely in all open areas of the aquarium and that there are no places where they could become trapped. Some consideration must be given to tankmates, as although the spines are a fearsome deterrent, some larger, belligerent fish species may not be able to resist a nibble just to see whether it is palatable (e.g. some large tangs, large angelfish, large wrasse, parrotfish, puffers, triggers etc). Crabs should also be avoided and there should not be too many direct food competitors housed in the same aquarium. As with other invertebrates, do not use copper-based medications if you have Heart Urchins in the tank. Heart Urchins do lose the occasional spine from time to time, but excessive spine dropping is not a good sign and is usually an indicator of stress/illness due to poor water quality, too rapid a change in water chemistry, or nutritional issues.
Feeding
Longspine Heart Urchins are sediment feeders and process the edible bits of food found in the substrate as they burrow. In the aquarium, they require a mature, deep, coarse sand bed which will provide an ongoing source of natural foodstuffs, and where the urchins will bury and search out uneaten food and detritus.
Breeding
Longspine Heart Urchins have not been bred in the home aquarium. The sexes are separate and they practice external fertilisation, simultaneously releasing eggs and milt into the water column. Heart Urchin larvae look nothing like the adults and undergo drastic metamorphosis, changing from a bilaterally symmetrical form that drifts amongst the plankton, to one that eventually settles and develops into miniatures of the adults. This process takes several months.
