One of, if not THE most rewarding experience I had when visiting Antarctica was finally getting to see this animal ALIVE.
When I began studying starfish many years ago, I was captivated by this paper by John H. Dearborn, K.C. Edwards & D.B. Fratt 1991 who very wonderfully described the feeding biology and behavior of Labidiaster annulatus...a large BENTHOPELAGIC predator in the Southern Ocean ecosystem!
yes, you heard that right. A starfish that EATS mobile SWIMMING prey. Not just the odd, errant sick fish..but small, fast moving krill on a regular basis!!
Labidiaster annulatus uses these crazy long arms (note the rings which contribute to the skeletal flexibility) to wrap around, nab or otherwise grab prey in conjunction with these helpful things....
Essentially, they are jaw/claw-shaped structures that literally cover the surface of the animal like a big dangerous, shaggy rug covered with bear traps.
When small krill or other prey settle, get too close or otherwise get within striking distance..the starfish GRABS the food with the pedicellariae or its arms and DRAGS the prey via the arms and tube feet down to the mouth, where it is digested immediately by the stomach.
Labidiaster does eat other food..moribund material, etc. as opportunity presents. But gut contents suggest that pelagic prey...amphipods, krill, etc. are its preferred prey. The picture below was taken after having fed a Labidiaster specimen at the Palmer station Marine Lab aquaria.
But even this is only PART of the picture. Other physical aspects contribute to the striking image of this beast:
1. Labidiaster is BIG. With arms outstretched...these animals can reach and possibly surpass a diameter of TWO FEET!
2. They PERCH. That is, they find places to crawl up onto in order to take advantage of water flow...so they sit like kings on sponges, rocks, or what have you and sit above the substratum with their immense arms outstretched like large deadly flowers.
3. Labidiaster is very abundant within its range. Basically, Labidiaster is one of the most numerous starfish to be found in the South Shetland Island/Antarctic Peninsula region (see Manjon-Cabeza et al. 2001)
These Antarctic benthos look like a scene out of some terrifying Lovecraftian-horror story...Large tentacled starfish sitting on their monstrous poriferan thrones ruling over the obsequious but ravenous brittle stars, swimming carnivorous ribbon worms, and who knows what other crazy stuff running amok!! But curiously...NO Fish!! Something I will go into further detail later on...