LILLELUND and LASKER: PREDATION BV MARINE COPEPODS 



ii-D' 



Figure 1. — Constant level device for maintaining copepods and fish larvae. The temper- 

 ature of the 3500-ml beaker (B) was kept constant with running seawater in a water 

 table (A) whose capacity was 610 liters. Plankton netting (0..333-mm mesh) was held 

 over the mouth of the 500-ml funnel (C) with a section of bicycle tire tube. Rubber 

 tubing showing constrictions as D and D' had screw-type clamps to regulate flow. E is 

 the drain. Note that the level of seawater is higher in the beaker than in the bath. The 

 drawing is not to scale. 



MARINE COPEPODS CAPABLE OF 

 KILLING ANCHOVY LARVAE 



Euaetideus acutus 

 Candacia bipinnata 



Before choosing Labtdocera and PonteUopsis 

 for experimental work we tested a number of 

 copepod species for their ability to capture or 

 fatally injure newly hatched yolk-sac larvae of 

 the northern anchovy. For each test, five fish 

 larvae were isolated in 200 ml of seawater in a 

 Petri dish at room temperature (20° C) usually 

 with two or three copepods of a particular species 

 to be tested. Of the local copepod species ob- 

 served, the following fatally injured anchovy 

 larvae by biting them or captured and ingested 

 them: 



Acartia dana and A. tonsa 

 Eiichirella rostvata and E. sp. 

 Labidocera jollae and L. trispinosa 

 Pleuromamma borealis 

 PonteUopsis occidentalis 

 Euchaeta acuta 



Because the two species of Labidocera listed 

 above are common to waters adjacent to San 

 Diego and were readily available, most of our 

 experimental work was done with them. When 

 PonteUopsis occidentalis became abundant, we 

 also collected some information about its preda- 

 tory behavior relative to fish larvae. 



Although capture and ingestion of fish larvae 

 was commonplace under laboratory conditions, 

 it is rare to find a copepod with a captured fish 

 larva in Formalin-preserved plankton. This may 

 be the result of the Formalin preservation com- 

 mon on shipboard which, we have observed, usu- 

 ally causes copepods to drop larvae.' 



' We have found that if a copepod has captured a 

 larva it will retain the larva if both are transferred to- 

 gether to a slight melted depression in an ice cube with 

 a pipette and preserved with a drop of 3% Formalin. 



657 



