20 



Larval fish behavior -anchovy larva, alive and under ex- 

 perimental conditions in the laboratory. 



While Lasker was in Aberdeen he took advantage 

 of access to an electron-microscope to continue his 

 studies on the mechanism of salt excretion of the Pacitlc 

 sardine larvae under different salinities. The studies in- 

 volved examination of sections of the larval skin. The re- 

 sults showed that in both hypotonic and hypertonic en- 

 vironment all larval sardine skin cells increase in volume 

 and subsequently return to normal or near normal despite 

 continued immersion in the test solution. No morpho- 



G. Mattson 



logical changes occur within the normal skin cells, but 

 changes are profound in the microtubular structure of 

 the "chloride cells." It now seems probable from the 

 accumulated evidence that these cells do in fact partici- 

 pate in osmoregulation of the sardine larva. 



A further study of osmoregulation has begun, ui 

 collaboration with the California Department of Fish and 

 Game, on the effect of increasing salinity on the success 

 of fertilization, larval mortality, and development offish 

 larvae in the Salton Sea in California. 



The long-term study of the energy budget of the 

 Pacific sardine has reached the stage at which a first syn- 

 thesis may be made. R. Lasker has found that growth ac- 

 counts for 18.5 percent of the assimilated energy of the 

 average sardine during its first year of life. Energy needed 

 for growth declines in succeeding years to as little as 1 .0 

 percent in the sixth year. Respiration is the dominant 

 energy-consuming process throughout the sardine's life, 

 requiring 82 to '■)'•) percent of the assimilated calories, 

 and reproduction accounts for only about 1.0 percent of 

 this energy. 



.i^n annual fat cycle was shown to alternate with 

 the reproductive cycle. Fat accumulated at the peak of 



l:xperimental physiology -croaker eggs and larvae from 

 the Salton Sea, alive and just hatching in salinity toler- 

 ance experiments. G. Mattson 



