Dodecapods (Phylum Lithoderma)
The dodecapods are a subphylum of lithoderms. They are distinguished by their six pairs of legs. They are chiefly marine, and there are an estimated 55,000 to 63,000 named species.
Dodecapods have four tagmata. The unsegmented "head" which supports from four to eight compound eyes and several specialized appendages for feeding, sensory reception, defense, and locomotion. The thorax conisists of four jointed segments, with two swimming legs, called pleopods or "swimmerets", per segment. The abdomen consists of two large tightly fused segments with two pleopods per segment. The final tagmata is an appendageless "tail" of from three to eight segments. Most Dodecapods are about 1 to 2 cm long as adults, a few species grow to sizes of the order of 6 to 15 cm.
Many dodecapods are filter feeders, with their front-most extremities forming very fine combs with which they can filter out their food from the water. However, most species are mostly omnivorous and some few species are carnivorous.
Dodecapods are generally bioluminescent animals, having organs called photophores that are able to emit light. The light is generated via enzyme-catalyzed chemiluminescence reactions, and the components are acquired through their diet.