After 4 days, the animals were removed and 

 allowed to clear their gut. Animals were then 

 placed in flasks, and air was passed through 

 the water and then through an absorbent to 

 collect the respired CO 2- Aliquots of the ab- 

 sorbent were placed in a liquid scintillation 

 counter to determine if radioactivity was 

 present. If these animals utilized detritus as 

 food, C Oo was collected in the absorbent. 



Other experiments were carried out to de- 

 termine if bacterial degradation increased the 

 utilization of detritus. Results from animals 

 fed labeled grass that had not been subjected 

 to bacterial action were compared with results 

 from animals fed grass that had been subjected 

 to bacterial action for 10 days. Also, animals 

 fed labeled detritus along with labeled bacteria 

 were compared with aninnals fed unlabeled 

 detritus but with labeled bacteria to determine 

 if they fed on the detritus, the associated 

 bacteria, or both. 



Results: 



Experiments are still in progress, but pre- 

 liminary data indicate the following about the 

 grass shrimp, Palaemonetes pugio, the domi- 

 nant crustacean in the eel grass beds: 



1. It feeds mostly on nondetrital nnatter but 

 also feeds to some extent on detritus. 



2. It also can assimilate dissolved organic 

 nnatter from the water as indicated by the 

 uptake of carbon 14 by the controls. 



3. It appears to feed on both detritus and 

 the associated bacteria. 



THE NUTRITIONAL VALUE OF MARINE 



PHYTOPLANKTON TO CRUSTACEAN 



LARVAE 



Lowell V. Sick 



Objective: 



To investigate the source of nutrition for 

 crustacean larvae, the efficiency of utilization 

 of food, and the potential capacity of the larvae 

 to transfer energy to the ecosystem. 



Justification: 



Although studies have been carried out on the 

 nutritional value of unicellular algae, on the 

 filtering efficiency of crustacean decapods, and 

 on the feeding of marine organisms on uni- 

 cellular algae, our present knowledge is not 

 extensive or definite enough. A need exists to 

 investigate the relation between primary pro- 

 ducers and larvae that are believed to feed 

 exclusively on phytoplankton. Only larval stages 

 have been considered because they offer the 

 best index of growth, development, and sur- 

 vival. 



Experimental Procedure: 



Thirteen species of marine unicellular algae, 

 cultured under constant conditions of tempera- 

 ture, light, pH, and salinity, were analyzed for 

 protein and carbon content. In addition, content 

 of the cell wall and thickness of the cell wall 



were determined. Dry weight and cell volumes 

 were related to logarithmic growth rates for 

 each species. Similarly, total protein and 

 carbon were determined for the nauplii of brine 

 shrimp; three zoeal stages of grass shrimp, 

 Palaemonetes vulgaris and P. pugio ; and the 

 protozoeal stages of the pink shrinnp, Penaeus 

 duorarum . 



Filtering rates, ingestion rates, and assim- 

 ilation indices for larvae of brine shrimp and 

 Penaeus were determined using algal cells 

 labeled with zinc 65. Radioactive brine shrimp 

 nauplii were used to establish filtering rates 

 and assimilation indices of Palaemonetes zoea. 

 The assinnilation indices were computed by 

 comparing the daily rate of protein and carbon 

 consunnption minus excretion with the total 

 amount of protein and carbon present during 

 any given larval stage. Variations in growth, 

 development, and survival were compared for 

 animals fed on different algal species in the 

 same growth phase, for animals fed on the 

 same algal species in different growth phases, 

 and for animals which were not fed. 



The total lipid constituent of algal cells and 

 its assimilation by larvae of the species men- 

 tioned above will be studied in future experi- 

 ments. The nutritional value of phytoplankton 

 grown in the laboratory under varying environ- 

 ments also will be determined. The items to 

 be measured and the experimental procedures 

 will be the same as those above. 



Bacteria-free algal cultures were developed 

 to determine how bacteria affect the nutritional 

 value of phytoplankton. Pure cultures of ma- 

 rine phytoplankton were repeatedly washed in 

 a special Millipore aseptic filtration system. 

 Cultures were then treated with penicillin, and 

 all algal transfers and larval culture inocula- 

 tions were performed within an ultraviolet 

 light chamber. Comparison between the growth 

 of larvae fed on bacteria-free algae and those 

 fed on regular algal cultures illustrated the 

 effect of bacterial infection in nutrition ex- 

 perinnents. 



Results: 



1. The carbon and protein contents and wall 

 thickness differ significantly among different 

 species of algae. In different growth phases 

 within a given species the variation is statisti- 

 cally significant. 



2. Algal biochemistry and morphology are 

 critical to the growth and development of 

 phytoplankton-consuming larvae. At a given 

 temperature, salinity, and pH, the growth, de- 

 velopment, and survival of such larvae can be 

 predicted according to the amount, species, 

 and growth stage of unicellular algae upon 

 which the nauplii and larvae graze. 



3. The total carbon and protein contents 

 vary significantly among different species of 

 shrimp larvae after equal periods of growth. 

 A difference of 24 hours of growth in a given 

 species produces significant variation. 



