For educational purposes only;:
Information on the basics of Invertebrate Zoology
Kingdom: Animalia, Phylum: Brachiopoda
CLICK on underlined file names and included illustrations to enlarge:
The Brachiopoda are entirely marine organisms that were very abundant during the Paleozoic Era but which today constitute a relatively small group. They are bivalve shells, the dorsal and ventral shells being unequal in size and shape. This differs from clam shells that are lateral. There is a stalk at the posterior end called the peduncle and which serves for attachment. A lophophore occupies the whole anterior half of the shell and serves as a feeding mechanism similar to that found in the Bryozoa. There is a U-shaped digestive tract and a true coelom. But there are no special respiratory organs. Nephridia are present that serve for excretion. These are a pair of ciliated tubes, which open into the coelom on one side and to the outside of the organism on the other side.
Circulation.-- There is a heart with several vessels.
Musculature.-- There is a well developed musculature, especially in the stalk and for the two valves.
Nervous System.-- A nerve string and ganglia are present
Sense Organs.-- Various sense organs occur on the area of the lophophore.
Reproduction.-- Gonads lie on the mantle, which is a thin flap of the body wall. Most species are hermaphroditic. Cavities of the coelom extend into the mantle and these then hold the gonads. Gametes leave the body by way of the nephridia. Fertilization is external. Ciliated larvae are formed, which swim out, settle down, and develop into a new individual.
Please see following plates for Example Structures of the Brachiopoda:
Plate 62 = Phylum: Brachiopoda: Lingula sp., Laqueus sp. & fossil