What do Coelenterates have on their tentacles?

Answer 1

Coelenterata is a term no longer in favor to describe members of two very interesting phyla of sea creatures, Ctenophora (comb jellies) and Cnidaria (coral animals, true jellies, sea anemones, sea pens, etc). Cnidaria are the stinging phyla; I will assume these are who you mean. Cnidaria contains some of the most interesting and unusual animals on earth. They are what one might think of as a "hive mind" and, in fact, each seemingly single animal is actually a group of animals that have no heads and, their "ends" (if one can call them that) are referred to as nearest to and furthest from the mouth (oral and aboral, respectively). But you asked about tentacles. Each member of the family Cnidaria possesses nematocysts, which are "multiple, highly developed stinging units" that can penetrate human skin. Each tentacle may fire thousands of these into human skin upon contact. The problem seems to be less one of poison than of mass penetration, as if by multiples of multiple thorns. While stings from box jellies have, of course, been responsible for deaths, most are not. Vinegar, of all things, seems to be one of the best topical medicines. But don't just leave your research here. Caveat stingee, delve further.