In varying amounts, depending on the species, Sarcophyton leathers will warp their upper surface and direct the water flow by forming ridges that lead to feathery pinnules on their tentacles. These feathery pinnules are designed to sieve the water for nutrients. The capitulum (top) has autozooid and siphonozooid polyps that are rather long when extended. When the polyps are completely retracted, the surface has a very smooth look to it.
Lambis truncata is the largest and heaviest of spider shells, up to 40 cm. Lambis truncata is similar to Lambis lambis but with a more squarish outline. Younger shells are creamy white; columella and lip usually mauve brown when older.
Evolutionarily, Diadema setosum is considered one of the oldest of the known extant species in the genus Diadema.
Genetic analysis of the Diadema have placed D. setosum at a basal branch on a cladogram, having it as the sister group to all the other remaining members of the genus. Morphological analysis confirms this conclusion, adding weight to the concept of D. setosum being the most basal of the Diadema and possibly the oldest extant species in the genus.
Linckia lavegiata or blue starfish, because -you know- the one that we usually found is blue. But if the population is healthy they might exhibit other colours such as orange, peach, pink and even green. =]