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Most species in this order have five arms and two rows of tube feet with suckers. There are conspicuous marginal plates on the arms and disc. Some species have paxillae and in some, the main pedicellariae are clamp-like and recessed into the skeletal plates. [110] This group includes the cushion stars, [113] the leather star [114] and the sea ...
In these, there is a transitory hexamerous symmetry in what is a normally a pentamerously symmetrical genus. The immature individuals with 6 arms appear so different in appearance from mature individuals with 5 arms that they were at one time considered to be two genera, Hydrasterias and Sclerasterias. Juveniles with arms measuring between 8 mm ...
As different species of starfish breed at different times of year, Orchitophrya stellarum may move from one species to another in accordance with their reproductive cycles. In the Pacific Ocean, it may alternate between parasitising Evasterias troschelii and Pisaster ochraceus during the spring and summer and Leptasterias spp. in the winter.
The unusual animals have unique body plans arranged in five equal sections that differ greatly from the symmetric head-to-tail bodies of bilateral animals, which have left and right sides ...
An echinoderm (/ ɪ ˈ k aɪ n ə ˌ d ɜːr m, ˈ ɛ k ə-/) [2] is any animal of the phylum Echinodermata (/ ɪ ˌ k aɪ n oʊ ˈ d ɜːr m ə t ə /), which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". [3]
Additionally, female barn swallows, a species where adults have long tail streamers, prefer to mate with males that have the most symmetrical tails. [26] While symmetry is known to be under selection, the evolutionary history of different types of symmetry in animals is an area of extensive debate.
Animals mainly have bilateral or mirror symmetry, as do the leaves of plants and some flowers such as orchids. [30] Plants often have radial or rotational symmetry, as do many flowers and some groups of animals such as sea anemones. Fivefold symmetry is found in the echinoderms, the group that includes starfish, sea urchins, and sea lilies. [31]
A species of pufferfish and two triggerfish have been observed to feed on crown-of-thorns starfish in the Red Sea, and although they may have some effect on the A. planci population, no evidence exists of systematic predation. [37] In the Indo-Pacific waters, white-spotted puffers, and Titan triggerfish have also been found to eat this starfish ...