than Vi of an inch long. Those of average size are so 

 small that they are easily overlooked, even when a 

 cupful of pond water or sea water contains several 

 hundreds of them. 



The copepod encountered most frequently in fresh 

 water is Cyclops, named for the one-eyed giant of 

 Greek mythology. Cyclops seldom reaches a length 

 of 'i,j of an inch and appears to the unaided eye as 

 a translucent milky white mote jerking along slowly 

 through the water. It does have a single eye in the 

 middle of the front of the head. If the individual is a 

 female with eggs, her two egg masses may be almost 

 as large as she is and suggest saddle bags. If a male is 

 attending his mate, he holds to her with his second 

 pair of antennae and they swim in tandem hour after 

 hour while he transfers enough sperm cells to ferti- 

 lize several batches of eggs. 



Copepods in the drifting plankton near the surface, 

 whether in fresh water or the ocean, tend to be highly 

 transparent and colorless. Those associating with the 

 bottom in shallow water may be pink or green or 

 blue, whereas those in the black abysses of the ocean 

 are more often black or blood red. All of them use 

 fans of bristles on their feet to gather in microscopic 

 plants or other nourishing particles as food. Often di- 

 gestion is rapid enough that the digestive tract re- 

 mains inconspicuous even when the body itself is 

 glass-clear. 



Most copepods hatch as six-legged, one-eyed crea- 

 tures and undergo a number of molts before this 

 "nauplius" stage is succeeded by the adult body form. 

 An adult usually has many pairs of legs and no eyes, 

 or one, or several. Yet the role of eyes is not easy to 

 demonstrate, for even eyeless copepods tend to make 

 long vertical migrations every day, swimming down- 

 ward around daybreak and up again in late after- 

 noon. 



Some of these daily journeys are spectacular. The 

 abundant marine copepod Calamis finmarchicus. 

 about the size of a big grain of rice, travels from its 

 daytime hideaway 11 00 to 1500 feet below the sur- 

 face to the topmost 150 feet of water at a speed of 

 about 150 feet per hour. Before dawn it heads down 

 again, diving about three times as fast. 



These movements are not dependent upon light or 

 the availability of food, for they are shown by cap- 

 tive animals in an endless ring-shaped tube at the 

 same times of day in complete darkness. For a 1/2- 

 inch crustacean to travel up a thousand feet and 

 down again each day at half an inch each second is 

 equivalent to a man's dog-trotting for the same length 

 of time at four miles an hour — covering forty-six 

 miles daily to reach a vegetable plate! 



The number of animals performing these vertical 

 migrations daily in the sea is unimaginable. With the 

 copepods go slightly larger crustaceans and the small 

 fish that prey upon them. With the small fish go larger 



fish and squids in fantastic abundance. So dense is 

 this migratory population during the day that the 

 most modern sonar depth-measuring devices on ship- 

 board sometimes cannot distinguish between the DSL 

 (deep scattering layer) and the true bottom. The 

 "phantom bottom" reflects the sound waves but of- 

 fers no discernible resistance to the line and lead 

 weight with which depth was formerly tested. 



Directly or indirectly, the copepods provide a tre- 

 mendously important link between the microscopic 

 green algae that create foodstufts in the sea with the 

 energy of sunlight, and the multitude of larger ani- 

 mals that live far from shore. Vitamins elaborated 

 by the algae and transferred into the copepods and 

 then into the carnivorous crustaceans of the krill 

 turn up in the oil of whale livers and then in the 

 bottled concentrates for human dietary supplements. 

 Proteins of plant cells, transformed into copepod 

 proteins, are reorganized into the flesh of herring 

 and salmon, cod and tuna. 



Some copepods turn the tables on the fish, attack- 

 ing these larger denizens of the ocean and sucking 

 their blood or lymph as food. Many a marine fish, 



The one-eyed Cyclops is a fresh-water copepod. This 

 is a male, about l'i,i inch long; the female usually car- 

 ries a cluster of eggs attached to each side of her 

 body. (P. S. Tice) 



