PROCEDURES 



Our basic method of collecting data was to merely follow the movements 

 of individual Cyphoma as they browsed on gorgonaceans and moved from 

 one prey individual to another. To determine the effect of previous 

 experience on prey choice, we took Cyphoma from different prey species 

 and released them in positions where 2 or 3 species of gorgonaceans 

 arose from adjoined bases. The Cyphoma were placed lengthwise on the 

 border between two gorgonaceans so that its right half lay on one prey 

 species and its left half lay on the other. The removal of coenenchyme 

 by Cyphoma was measured at least once per day for each gorgonacean 

 prey. The daily increase in surface area of damaged tissue was 

 measured with Vernier calipers. Several branches of each gorgonacean 

 prey species were collected and permanent spicule mounts were made. 

 Identifications were based upon these specimens. 



RESULTS 



The population of Cyphoma gibbosum in Lameshur Bay preferentially 

 feeds on gorgoniid gorgonaceans and tends to reject plexaurids. This 

 is suggested in a comparison of the relative frequencies of gorgonacean 

 species in the diet with the frequencies of these species in the 

 environment (Table 1). An "index of electivity" (e) is used which 

 rates prey species on a scale from -1 to +1; "-1" indicates total 

 rejection of the prey species; "o"indicates that the prey is taken 

 precisely in proportion to its abundance; "+1" indicates preference 

 of the prey species to the exclusion of all others; while positive and 

 negative fractions indicate relative degrees of acceptance and 

 rejection (Ivlev, 1961). The gorgonacean abundances are based on 

 counts made in 11 quadrats of 4 m each. Only 8 Cyphoma were found 

 in these quadrats with 283 gorgonaceans, or 1 predator to every 35 

 potential prey. Cyphoma were found preying upon other gorgonaceans, 

 such as Pterogorgia quadalupensis , Muricea muricata or Muriceopsis 

 f lavida on sand or patch reef areas. Our discussion is limited to prey 

 found within the quadrats. 



Prey species* ^o.^ Pi No. in ri e = 

 44 m (7o) diet (%) 



r -P 



i i 



f •+P.= 



Gorgonia sp. 17 6.0 89 71.8 + .86 



Eunicea succinea 2 0.7 5 4.0 + .70 



Pseudopterogorgia 



americana 17 6.0 16 12.9 + .37 



Briareum asbestinum 43 16.2 6 4.8 - . 54 



Eunicea sp. 12 4.2 1 0.8 - .68 

 Plexaura homomalla 



f. kukenthali 15 5.0 1 0.8 - .72 



Pseudoplexaura 



flagellosi" 71 25.1 5 4.0 - .72 



Plexaura flexuosa 30 10.0 1 0.8 - .85 



Other gorgonaceans 



(about 8 spp.) 76 26.8 O^^O -1.00 



Table 1. The diet of Cyphoma gibbosum and the relative abundances of 



prey species on the reef at Lameshur Bay. Identification of prey tentative. 



VI-60 



