ZOOLOGICAL SOCIETY BULLETIN 



FRESH-WATER SHRIMP WITH EGGS IN BROOD POUCH 

 Actual size lunim. 



minute lump of mud. or the cast shell of an- 

 other shrimp. In sitting out with the prize, 

 the creature swims in a spiral, and it is to be 

 suspected that the English species (G. pulcr), 

 assuming that it acts in the same manner, de- 

 rived its name of "Fresh-water Screw" from 

 this curious habit, rather than from its method 

 of twisting about when removed from the water, 

 as some naturalists have suggested. 



If a particle of food is too heavy for one to 

 lift, two or three will convey it together, kicking 

 the while and disputing — if mutely, at least 

 forcefully — for individual possession; and if it 

 is too heavy to be carried at all, the shrimps 

 will settle upon it from all sides, forming a liv- 

 ing, heaving, olivaceous rosette that does not 

 break up until every edible atom has been con- 

 sumed. It is not the shrimps' preference to eat 

 in this fashion, like pigs at a trough, and they 

 endeavor to tear off small portions of the mass, 

 that each may sail away and enjoy his share 

 alone. Their legs are too long and numerous 

 and their antennae too delicate, to make close 

 herding pleasant. They apparently have little 

 or no sense of smell, for one may alight within 

 a fraction of an inch of a bit of food and remain 

 there indefinitely without discovering it. Only 

 by lighting directly upon it does the shrimp 

 discover the food, and if one is carrying a bit 

 of debris and lights upon a piece of fish, it does 

 not drop the debris, but swims away with it. 

 evidently unaware of the feast it is missing. 



In captivity the shrimps thrive on aquatic 

 plants and lettuce, microscopic particles gath- 

 ered in the bottom mud. and macerated clam. 

 fish and meat. 



The eyes are reniform in structure, that is 

 to say. arranged in small, irregular cubes of pig- 

 ment, and the sight is consequently poor. The 

 long antennae arc constantly used to acquaint 

 them with the nature of surrounding objects. 

 (The two pairs of antennae are sometimes called 



"first and second antennae." sometimes "ante- 

 rior and posterior antennae," and again, "an- 

 tennules and antennae." For greater clearness 

 they are here designated as long and short 

 antennae.) 



The shrimps frequent the surface, nestling 

 in the plants, and a tap on the vegetation will 

 send them to the bottom in showers. They 

 abound in the roots of duckweed, salvinia. and 

 other floating plants. Much time is also spent 

 in ploughing through the sediment at the bot- 

 tom. As explained, they swim in a spiral after 

 taking possession of a particle of food or other 

 object suitable for carrying about, and they 

 swim habitually on their backs, with the body 

 held out straight; whereas in walking, the tail 

 is curled under like that of a lobster and the 

 legs are all employed. The head is always 

 pointed in the direction in which they are going. 

 When swimming in a horizontal line, they as- 

 sume a horizontal position. When ascending 

 direct to the surface, they swim perpendicularly, 

 head up. In descending, they swim perpen- 

 dicularly, head down, and there is usually a 

 "head-on collision" when they strike bottom. 

 head foremost and upside down ; but the curved 

 head and smooth, shelly back, offer ample pro- 

 tection. 



As in other crustaceans, molting occurs, the 

 new body working out through the dorsal open- 

 ing of the old head segment at its juncture with 

 the first thoracic segment. The body is suc- 

 cessively contracted and expanded much as one 

 opens and closes the palm, and finally emerges 

 very quickly, leaving a ghostlike shell with the 

 head hanging loose. 



The U. S. Fish Commission has recommend- 

 ed the transplanting and breeding of fresh- 

 water shrimps for the consumption of fishes in 

 the home ponds, and various fish breeders have 

 asserted that the flesh of trout fed upon shrimps 

 has a pink tinge and a delicacy of flavor so 



FRESHWATER SHRIMP WITH YOUNG MOVING 

 BROOD POUCH 



