Copepoda 221 



Order copepoda 



CULTURE METHODS FOR PELAGIC MARINE COPEPODS 



George L. Clarke, Woods Hole Oceanographic Institution and Harvard University 



PELAGIC marine copepods are extremely delicate and sensitive to 

 slight changes in their environment and no completely satisfactory 

 technique for culturing them has yet been worked out. The methods 

 described below are the result of preliminary experiments which have 

 been undertaken at Woods Hole using the following species: Centro- 

 pages typicus and C. hamatus, Labidocera aestiva, Acartia tonsa, and 

 Calanus finniarchicus. 



Collecting. The copepods were collected by making short hauls with 

 a plankton net from the laboratory power boat. Each haul was just 

 sufficiently long (%-4 min.) to obtain the desired number of specimens 

 (50-200), and no more, in order to avoid overcrowding. The mesh of 

 the net was selected according to the size of the copepods desired, the 

 coarsest possible net being used in each case so that the amount of other 

 plankton material taken at the same time might be reduced to a mini- 

 mum. The animals were protected from harmful crowding and abrasion 

 by closing the tail of the net with a 2 -liter glass jar. At the end of the 

 haul the glass jar was removed from the net and in the case of Centro- 

 pages, Acartia, and Labidocera, which were obtained in Woods Hole 

 Harbor and Vineyard Sound not more than 15 minutes' run from the 

 laboratory, the copepods were left undisturbed in the jar (but protected 

 from the sun) until the laboratory was reached. But in the case of 

 Calanus, which could be obtained only in Vineyard Sound off No Man's 

 Land (near the bottom) — requiring a 3 -hour trip back to the labora- 

 tory — the catch was diluted and kept at a low temperature by placing 

 the containers in the boat's ice box. Immediately upon arrival at the 

 laboratory the copepods were transferred by means of a large-mouthed 

 pipette to the containers to be used for culturing. 



Containers. The suitability of a variety of containers, including large 

 battery jars, beakers, Erlenmeyer flasks, and small crystallizing dishes 

 was tested. The size and shape of the container was not found to have 

 any significant effect on survival as long as the animals were not unduly 

 crowded. When the culture water was not changed, an allowance of 

 20 cc. of water per copepod appeared to be adequate provided that the 

 animals did not tend to cluster in one part of the culture dish. For the 

 purpose of keeping track of the condition of individuals small containers 

 were found most suitable. Erlenmeyer flasks of 250-500 cc. capacity, 

 which were plugged with cotton stoppers or covered with inverted petri 

 dishes, were used, and small crystallizing dishes (50 x 35 mm.), a num- 



