MAY: EFFECTS OF DELAYED INITIAL FEEDING 



the first time on this day (SS-^f)— Table 4. 

 However, on days 7, 10, and 13 the feeding in- 



Table 4. — Feeding incidence of previously fed and un- 

 fed larvae. Larvae were exposed to Artemia nauplii for 

 1 hr, after which they were examined for evidence of 

 feeding. 



Age 

 (days) 



Larvae previously fed 



Number 

 of larvae 

 feeding 



Number 



of larvae 



not 



feeding 



Percent 

 feeding 



Lorvae previously unfed 



Number 

 of larvae 

 feeding 



Number 



of larvae 



not 



feeding 



Percent 

 feeding 



4 

 7 

 10 

 13 

 16 



22 

 21 

 22 

 20 



88.0 

 91.3 

 91.7 

 83.3 



9 



23 



24 



8 



4 



17 

 I 

 1 

 2 



34.6 

 95.8 

 96.0 

 80.0 

 100.0 



cidence was similar (between 80 and 96%) in 

 larvae which had fed and those which had not 

 fed prior to the test. On day 16, the darkly 

 pigmented abdomen of previously fed larvae 

 made it impossible to determine their feeding 

 incidence, but all of those larvae tested which 

 had received no food prior to day 16 did con- 

 sume food on this day. The failure of pre- 

 viously fed larvae to show a feeding incidence 

 of 100% in these experiments probably reflects 

 the stress associated with transfer between con- 

 tainers. 



FOOD INTAKE AND CONVERSION 



On day 1, the mean dry weight of the larval 

 yolk supply was 0.027 mg (range, 0.015-0.039 

 mg), and on day 4, fed larvae retained 0.003 



mg of yolk (range, 0-0.011 mg) while starved 

 larvae had no yolk left. 



In the quantitative feeding experiments, con- 

 ducted in small, 300-ml containers, some larvae 

 did not survive the 6-day experimental period, 

 and some exhibited erratic swimming behavior. 

 Only data from the surviving larvae which dis- 

 played normal behavior have been retained. Lar- 

 vae did not begin feeding until day 2, although 

 food was available to them on day 1. The num- 

 ber of nauplii consumed daily per larva increased 

 as larvae grew, from less than 50 in first-feeding 

 larvae to almost 300 in larvae 2 weeks old and 

 older. Table 5 gives the total food consumption, 

 growth, and conversion efficiencies of all healthy 

 larvae which survived the feeding experiments 

 in small containers. Larvae which displayed 

 growth comparable to that of larvae in 10-liter 

 containers may be expected to give the most 

 reliable conversion efficiency values and are 

 identified by asterisks in Table 5. One larva, fed 

 from day 1, showed the extremely high efficiency 

 of 73 % . Table 5 suggests a trend toward de- 

 creasing conversion efficiency as larvae get older. 

 In the experiment begun on day 7, the previously 

 unfed larva for which data are available showed 

 a much higher eflSciency than the previously fed 

 larva. 



BODY COMPOSITION 



Results of the analyses of carbon, hydrogen, 

 nitrogen, and ash in sampled larvae are given 



Table 5. — Food consumption, growth, and conversion efficiencies of individual larvae in small con- 

 tainers during 6-day feeding experiments. Asterisks identify larvae which exhibited growth comparable 

 to that of larvae in large containers and hence probably provide the most reliable conversion efficiency 

 figures. 



419 



