324 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



first protozoea in the IG- and 32-ounce jars by 

 adding approximately one medicine dropper full 

 of tlie culture per 32 oimces of water per day, and 

 although the digestive tracts of many of the larvae 

 were colored green, this food appeared to be in- 

 adequate. Another factor that caused high 

 mortality was entanglement of the setae of the 

 larvae by algae, by the shrimp's own excrement, 

 which is emitted in long strands, and by other 

 particles that are found in the water. The larvae 

 so entangled settled to tlie bottom wliere they 

 could not feed. 



Eggs, the five nauplial stages, and the first pro- 

 tozoea were presented in sufficient quantity during 

 this experiment to describe these stages. 



Third Experiment 



The third rearing experiment took place from 

 June 3 to June 6. Twenty-two shrimp were 

 brought to the laboratoi-y on June 3, and wei-e 

 placed in three 15-gallon aquariums. Eggs were 

 found in two of the aquariums on the morning of 

 June 6 and were removed and placed in 12 1-gallon 

 jars. Approximately 400,000 units of penicillin 

 were added to six of these jare, and the water in 

 one was agitated mechanically. A number of the 

 eggs developed, and two newly hatched nauplii 

 were seen. Several hours later, however, eggs 

 removed from the jars were not viable, and no 

 additional nauplii were fomid. 



Fourth Experiment 



In the foin-th rearing experiment, July 20-27, 

 approximately 20 female shrimjJ were placed in 

 three 15-gallon aquariums at the laboratory in the 

 early afternoon of July 20. The following morn- 

 ing eggs and newly hatched nauplii were found in 

 each aquarium and were removed to six 1-gallon 

 jars and a 4-gallon bell jar. Approximately 5 

 millilitei-s of the broad- spexitnma antibiotic were 

 added to three of the 1-gallon jare and about 20 

 millilitei-s were added to the bell jar. The latter 

 was agitated mechanically by a glass plunger. 

 The water was not changed in these containers 

 during the course of this experiment. 



The lai-A'ae had advanced to the fifth nauplial 

 stage by the late aftenioon of July 22, and the 

 following morning all the jars werB fomid to con- 



tain first protozoea. Tiiey wei-e fed a culture of 

 Dunaliella sp. ( whicli was used as food for oyster 

 and clam larvae by Davis and Guillard, 1958), by 

 adding approximately 4 millilitei-s to each 1-gal- 

 lon jar and 10 milliliters to the bell jar daily. 



Higli mortality again occurred in the fii-st pro- 

 tozoeal stage. The lai"vae held in tlie jars to 

 wliich no antibiotic was added were all dead by 

 the afternoon of July 24, and by the moniing of 

 July 27 all of the larvae in tlie other jars had died. 

 None of the larvae molted into the second pro- 

 tozoea despite the fact that feeding had taken 

 place. 



During tliis experiment, photomicrographs of 

 the egg in various stages of development and of 

 the nauplial and first protozoeal stages were taken. 



Conclusions 



To rear Penafns duormiim, successfully, suitable 

 food and the prevention of crowding of the larvae 

 are necessary. Hudinaga (1942) was successful 

 in raising larvae of Penaeus ']apon'wus through the 

 critical protozoeal stage by feeding them the 

 diatom SheJetoivema costatum.. He reported that 

 the mysis stage could be raised on that diatom 

 alone, although good results were obtained by mix- 

 ing the nauplius of P. japonicus with the diatoms. 

 Heldt (1938) found that the protozoea of several 

 species of penaeids prospered on small copepods if 

 the individual larva was isolated and the debris 

 and excrement removed from the water. 



Broad (1957) reported that caridean larvae fed 

 on algae did no better than those that were not 

 fed. He reared larvae to the young adult stage by 

 feeding them Artemia nauplii, and limited the 

 number of larvae placed in each 4-inch finger bowl 

 to 10. Costlow and Bookhout (1959) were suc- 

 cessful in rearing zoeae of the blue crab, Calli- 

 nectes sapidus, by placing them in plastic com- 

 partmented boxes with one zoea per compartment 

 and feeding them Arhacia eggs and Artemia nau- 

 plii. The author (unpublished data) succeeded 

 in rearing the larvae of several species of carideans 

 by placing from 1 to 10 larvae in each compart- 

 ment of plastic compartmented boxes and feed- 

 ing them on Artemia nauplii. Each compartment 

 contained from 50 to 75 ml. of sea water, and the 

 water was changed each morning. 



