and heavier (Students f-test, P < 0.001) at the end 

 of the experiment than the group fed plankton 

 (Fig. 3). 



The brine shrimp-fed lobsters were observed to 

 routinely leave their burrow in order to obtain the 

 brine shrimp which was fed to them daily. They 

 would then return and eat inside of their shelters. 

 The plankton-fed lobsters behaved differently. After 

 the plankton was placed in their tray, they would 

 begin vigorous pleopod-fanning while remaining in 

 their shelters. Plankton was seen being drawn into 

 their shelters by this fanning. 



The average dry weight of the plankton fed to 

 the lobsters daily was 2.6 + 1.4 mg, while the 

 average dry weight of the brine shrimp fed to the 

 lobsters daily was 5.0 + 4.7 mg. The water tem- 

 perature ranged from 18.5° to 10°C, averaging at 

 14.7°C. 



Discussion 



Emmel (1908) found that Stage IV lobsters could 

 molt to Stage V without being fed when they were 

 kept in flowing unfiltered water. Daniel et al. (1985) 

 showed that early juveniles can survive and grow 

 on a diet of frozen barnacle larvae. Budd et al. (1978) 

 showed that the young crayfish, Orconectes im.mu- 

 nis, can filter feed on algae by creating a feeding 



current and catching the algae in a filter formed by 

 the first maxillipeds and their maxillae. Factor 

 (1978) suggested that the mouthparts of larval 

 lobsters have enough setae placed appropriately to 

 make filter feeding a possibility. Upon close exam- 

 ination of Factors's data on Stage IV lobsters, it is 

 seen that this stage has even more setae than the 

 three previous stages. Recently, Kari Lavalli' has 

 extended Factor's study, finding that lobsters, at 

 least up to Stage VI, continue to have appropriate- 

 ly placed setae for catching plankton. Thus, mor- 

 phologically, postlarval lobsters seem to be capable 

 of catching plankton. 



This experiment has shown that while the unfed 

 postlarval lobsters all died, lobsters fed plankton sur- 

 vived as well as lobsters fed brine shrimp. The 

 lobsters fed plankton also showed a significant in- 

 crease in carapace length and weight. Therefore, 

 these lobsters were able to catch and consume live 

 plankton resulting in a net energy gain. Templeman 

 (1936) found that lobsters held at 13°C took 29 to 

 30 days between their fifth and sixth molt; there- 

 fore, the rate of molting in the brine shrimp-fed 

 group fell well within the rate of normal, nonfood 

 limited molting at a temperature of 15°C. 



■Kari Lavalli, Boston University Marine Program, Marine Bio- 

 logical Laboratory, Woods Hole, MA 02543, pers. commun. 1988. 



Z 



u 

 u 



CL 

 D_ 



a: 



CE 



u 



5TH BTH 



RRTEMIR 



5TH BTH 



PLRNKTON 



X 



□1 



I 

 ID 



2 



5TH GTH 

 RRTEMIR 



5TH BTH 

 PLRNKTON 



Figure 3.— The (A) carapace length and (B) weight of the Artemia (brine shrimp) fed lobsters and plankton- 

 fed lobsters at Stage V and Stage VI, (C) water temperature over the time course of the experiment. 



368 



