|From Wikipedia.. they are GREAT! Go give them some money!|
Why? Because its name is LITERALLY translated as "pillow or cushion" but for comparison, there's another similar looking beast called Halityle regularis. I see the two mistaken for one another all the time.. so here's the two genera for comparison...
This one is Halityle regularis. One species known, widely occurring from the Indian Ocean (Madagascar) to southern Japan (the Ryukyu Islands) and Australia and New Caledonia.
Interestingly, there are two colors I've seen on Flickr... This red one from Indonesia.
Haltyle has a very strongly defined net-like diamond pattern on the top surface and with the distinct colored region on the oral sufrace...
Here is Culcita!
In terms of appearance, Culctia is a bit chubbier, and more compact, but the patterns on the surfaces are more cloud-like and are not as distinct.
Especially on the oral surface, which depending on species is a bit rougher, almost spiny
We don't know that much about Culctia, but we know a little. The most widely occuring species, C. novaeguineae also eats coral but nowhere near the volume or severity that the dreaded crown-of-thorns starfish does.. Culctia's role is just as important though, in that it aids in community structure.. It feeds on certain kinds of coral and this influences how coral colonies grow...
And finally, the most widespread species in the Pacific
C. novaeguineae is HIGHLY variable.. it comes in MANY colors throughout its very wide range, in the Pacific, including Hawaii, Japan, the Philippines, Singapore, New Caledonia, and elswhere....which suggests it is possibly a bunch of cryptic species...
Surface on these is largely covered by granules or tiny spinelets....None of which seem to get very large.
Colors in this species are HIGHLY variable.. what is the significance? Different species? Different food? Simple random variation??