SEGMENTED SCHIZOCOELS 



237 



Figure 14.12 Class Crustacea. Subclass Branchiopodo: 1, Order Anostraco, Eubranchipus, a fairy 

 shrimp (x 3), fresh water, in typical upside-down swimming position (the closely related brine 

 shrimps of saline waters look similar); 2, Order Notostraca, Apus, a tadpole shrimp ( x 1 ), fresh water; 

 3, Order Conchostraca, fs//ierjo, a clam or claw shrimp {x 3) with its head at maximum extent, fresh 

 water; 4, Order Cladocera, Dophnio, a water flea {x 15), fresh water; 5, Order Cladocera, Leptod- 

 ora, a water flea ( x 3), fresh woter. 



Subclass Copepodo: 6, Cyclops, a water hopper {x 25), fresh water; 7, Argu/us, a fish louse (x 15), 

 parasitic. Subclass Ostracodo: 8, Cyric/opsfS, on ostracod {x 20), fresh water. Subclass Cirripedio: 

 9, iepas, a gooseneck barnacle (x 1), marine; 10, Miiella, a gooseneck barnacle (small specimen), 

 marine; 1 1, 6a/onus, an acorn barnacle (small specimen), marine; 12, Soccu/*no, a parasitic barnacle 

 on a very small crab, the bulbous (stippled) moss is the only external indication of the parasite 

 (x ' :t). (Modified from various sources.) 



ORDER CONCHOSTRACA (Claw or Clam Shrimps) 



Diagnosis: eyes sessile; carapace bivalved, clam- 

 shell-like, enclosing the compressed body; tail often 

 with terminal claws. 



ORDER CLADOCERA (Water Fleas) 



Diagnosis: eyes sessile; carapace resembles that of 

 Conchostraca, and is often bivalved, but never en- 

 closes head; tail often with terminal claws; minute 

 to microscopic. 



All branchiopods, except for a few marine cladoc- 



erans, are found in fresh water; however, brine 

 shrimp occur in saline lakes. Many branchiopods 

 have a peculiar life cycle in which young of the sum- 

 mertime hatch from unfertilized eggs and the over- 

 wintering eggs are fertilized. 



Branchiopod feeding is accomplished by movement 

 of the bristle-covered legs. Leg bristles accumulate 

 protozoans, rotifers, and detritus which are moved 

 to the mouth along a groove on the underside of the 

 animals. Besides this basic diet Notostraca are also 

 known to feed upon the remains of larger animals 

 such as earthworms, mollusks, and frog tadpoles. 

 Anostraca and Conchostraca seem to be restricted to 



