Exploding Starfish?

[kathywithbirds]

a salinity jump would make it expolde???

[dobejazz]

Originally Posted by kathywithbirds

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.

[kathywithbirds]

holy cow. that's nuts.

Good read, dobe!!

[fireshrimp]

Wow, Thanks for all the info. The salinity was a little high 0.126 for a day, but I got that down to 0.125 and ph was good. I checked all the other levels and everything was normal. If I did have a mini cycle I totally missed it. :smck: I have been keeping an eye on everything else in there and they seem to be acting normal. I have done one water change since the rock was soaked and am doing another one this weekend. Hopefully all is good now and I don't loose anything else. Thanks again for all the info and for welcoming me to the group!

[Melanie]

Welcome fireshrimp!

OMG, that is crazy and the info that dobejazz posted is fascinating.

[framerguy]

Welcome Fireshrimp!! You want to keep the salinity on the high range for starfish any way, so "getting it down" is not really an issue. They like 35ppt and some as high as 38ppt. They are found in full salinity waters. It's the sudden spike that overloads their vascular system and kills them. Some more interesting info I've found about sea stars is that when you acclimate them ( over 6+ hours!) you should put the water back in the tank (unless you KNOW its contaminated), there is abundant research showing the theraputic affect that starfish and the water they traveled in have on tank systems.

[tbittner]

Fascinating! Simply fascinating!

[gonefishin]

I'm sure everyone knows if you cut an arm off of a starfish it will jus grow back... hhhmmm... don't think it works the other way though.

[tbittner]

I was wondering the same thing. I wonder if she would have left it in the tank if it would have redeveloped into a couple of sand sifters?