a salinity jump would make it expolde???
This is some info borrowed from TDWyatt on another site
One of the features that distinguish echinoderms from all other animals is the presence of the ambulacral system, a relatively high-pressure hydraulic system that is used to power Asteroidea body movements. This hydrovascular system is a set of vascular vessels that use body fluids and seawater to extend and contract their tube feet. Tube feet are extensions of the final branches of this hydrovascular system. Although is was long thought that the tube feet used the hydrovascular system to produce suction that allowed the tube feet to “grab” the substrate, etc., it is now known that the base of the tube feet use a 2 substance system of adhesive/adhesive-resolver to literally “glue” the tube feet to the objects they come in contact with and unglue them to release them.
The presence of the hydrovascular system is probably one of the major limitations for keeping Asteroidea in the home aquarium. The ambulacral system is made up of many membranes and delicate tissues that simply do not respond well to repeated challenges by fluctuations in the salinity of the environment. If the changes are abrupt enough, the tissues/membranes will respond by rupturing due to the osmotic gradient across these membranes. Most echinoderms simply cannot tolerate fluctuations in the salinity of the water column. Echinoderms are some of the oldest living extant spp. of marine creatures, and have over millions of years adapted to living in fully marine (as opposed to estuary or brackish or freshwater) conditions, with the salinity at 35 to 36 PPT (1.026 S.G.at 84° F). Water does not enter the water vascular system passively; rather, it is actively pumped into the hydrovascular system through an as yet incompletely understood metabolic pathway. Fluctuations in salinity of the water column result in ruptures in the membranes of the hydrovascular system. This often leads to the ultimate death or at least the “explosion” of the sea star. This demise often occurs over several days to weeks, with pieces of flesh falling off the main body mass after the damage to the ambulacral system has occurred. See
blinkia for some pictures of the effects of salinity swings and poor acclimatization methodology on Linckia levegata. Some times the remaining rays will re-grow the central disk, so it is possible to maintain the pieces to recover and re-grow full bodies if there are few scavengers… most often though the sea star never recovers.
In addition to the possible assault on the hydrovascular system, Linckias have another target of salinity weaknesses. The aboral surface of stars is often covered with small, delicate, filmy projections of the main body cavity of the creature through holes in the body wall. These are the dermal gills, considered to be the primary site of gas exchange. These projections are filled with fluid from the body cavity, which is circulated through the structures by cilia. These dermal gills are also subject to osmotic rupture and damage during periods of salinity fluctuation. Consequently, although sea stars can survive a wide number of environmental challenges, from poor water quality to temperature fluctuations, they simply cannot tolerate fluctuations of salinity. Handling these creatures may damage these dermal gills as well, so the physical manipulation and relocation of these creatures should be discouraged.
