FOOD AND FEEDING 



Sub-Order Copopoda. Body small, distinctly segmented, the fore- 

 most segment fusfid with the head; antennae, mandables and maxillae well 

 developed, six pairs of swimming feet in the free-swimming freshwater 

 forms, which consist of the Cyclops and Canthocamptus. 



Cyclops. Fig. 70. Ten or twelve closely allied forms abound in 

 still and stagnant water. Their size is i to 1.5 millimeter. The segmen- 

 tation of the body is perfect, the Crustacean being 

 covered with a carapace of which the first segment 

 is fused with the head. Two long antennas are 

 present and but a single eye. The swimming 

 legs are attaches to the thorax, and the lengthen- 

 ed abdomen is provided with caudal appendages. 

 Their food is organic substances, infusoria and 

 algae, and their movements are steady and regular 

 FIG. 70— Cyclops ihomasi. as though propelled by driving wheels. The most 

 Greatly enlarged. generally distributed are C. thomasi, C. gyrinus, C. 



agilis, C. edax, C. modestas, C. ater and C. viridis. Canthocamptus is rare in 

 the Eastern and Middle states and occasionally occurs as an unrecognized 

 species. 



These Copopods possess extraordinary fecundity. In the winter they 

 seek the bottom and hibernate, but when the water reaches a temperature 

 of 45° to 50° F. they revive, their increase being greatest at G^" to 70° F.; 

 when the female every two days develops two egg sacs or external uteri, 

 wherein 16 to 32 eggs are hatched. In two days these become detached, 

 fall to the bottom where the young, almost globular cyclops, having four 

 legs but no tail, undergo a molting In about 15 days, when the other feet 

 and the tail form. In another 15 days they mature and reproduce. Car- 

 bonate of lime Is necessary In the formation of their shells. They thrive 

 in water infused with vegetal matter in decomposition, but as it does not 

 contract any odor of decomposition it Is probable that they live on the 

 Infusoria. Potamogeton, Ceratophyllum and Fountain cress, upon which 

 algae and voucheria will form are usually present to sustain the infusoria. 

 Young goldfishes usually reject Cyclops when they can obtain Daphnla. 

 It has also been observed that some species of Cyclops feed upon fish spawn 

 and will attack very young fishes. 



Malocostraca. These highly organized Crustacea have the thorax 

 of eight and the abdomen of seven segments. The sub-order Amphipoda 

 are shrimplike forms with stalked eyes; the Isopoda have depressed or flat- 

 tened bodies and gills borne on the abdomenal appendages; and the 

 Becapoda have the thoracic segments united with the head in a carapace, 



