Marine invertebrates at various trophic levels point at an important role in many ecosystems. Echinoderms (Greek for "spiny skin") is a phylum which contains only marine invertebrates. The adults are recognizable by their radial symmetry (usually five-point) and include starfish, sea urchins, sand dollars, and sea cucumbers, as well as the sea lilies. Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone. The phylum contains about 7000 living species, making it the second-largest grouping of deuterostomes (a superphylum), after the chordates (which include the vertebrates, such as birds, fishes, mammals, and reptiles). Echinoderms are unique among
Spiny mouse organism to study menstruation and reproductive disorders, as Mus musculus, the common laboratory mouse, does not menstruate. At least two species of African spiny mice, "Acomys kempi" and "Acomys percivali", are capable of autotomic release of skin upon being captured by a predator. They are the only mammals known to do so. They can completely regenerate the autotomically released or otherwise damaged skin tissue - regrowing hair follicles, skin, sweat glands, fur and cartilage with little or no scarring. It is believed that the corresponding regeneration genes could also function in humans. In a research article published on May 16,