Dermastenas 



tmbricata 



Figure 21. Some common invertebrate pre- 

 dators in kelp forests. 



broad diet (over 40 prey items for P_. 

 giganteus in a central California kelp 

 forest LHarrold 1981] and 34 in southern 

 California [Rosenthal 1971]), as does 

 Astrometis sertul ifera . However, the 

 latter are less effective than Pycnopodia 

 at capturing large sea urchins. The 

 leather star Dermasterias imbricata 

 (Figure 21) will eat the smaller purple 

 sea urchin Strongylocentrotus purpuratus 

 (Rosenthal and Chess 1972) as well as the 

 anemones Corynactis cal ifornica , 

 Anthopleura xanthogrammica , A. 

 elegantissima and Metridium senile (Annett 

 and Pierotti 1984). Sebens (1983) 

 indicated that predation by Dermasterias 

 and shading by algae may prevent 

 Anthopleura spp. from occupying subtidal 

 habitats. Schmitt (1982) found that sea 

 stars and other predators affected the 

 distribution of Tegula spp. on subtidal 

 reefs at Catalina Island. In the Point 

 Cabrillo kelp forest in central 

 California, sea star and fish predation 

 limits T. brunnea to shallow water where 

 understory vegetation provides a partial 

 refuge from these predators (Watanabe 

 1984a). 



Schroeter et al . (1983) found that 

 the bat star Patiria miniata could affect 

 the distribution of the small white sea 

 urchin Lytechinus anamesus on a small 

 scale in a kelp stand near San Onofre (San 

 Diego County). Patiria could capture and 

 consume Lytechinus in experiments done in 



the laboratory. From the escape response 

 of Lytechinus noted in the laboratory, 

 these workers concluded that the small- 

 scale distribution of the species in the 

 kelp forest was the result of the 

 predatory activities of Patiria . 

 Preferential feeding on particular 

 bryozoans by Patiria also affects 

 succession in bryozoan assemblages (Day 

 and Osman 1981). 



4.4.4.2 Molluscs (Mollusca) . 

 Several species of octopus are found with- 

 in kelp forests. They feed on a wide 

 variety of animals, but mostly on gastro- 

 pods and crabs. Schmitt (1982) indicated 

 that predation by Octopus bimaculatus and 

 other animals can have important effects 

 on the distribution of Tegula spp. at 

 Catalina Island. 0. bimaculatus also prey 

 on Norrisia norrisi . Moreover, if this 

 snail is only damaged by 0. bimaculatus , 

 subsequent fouling by barnacles on the 

 damaged shell makes the snail less able to 

 cling to kelp plants, and reduces its 

 ability to escape from other benthic 

 predators such as sea stars (Schmitt et 

 al. 1983). Some species of octopus are 

 large and can even capture and consume 

 large abalone. The cryptic coloring and 

 reclusive nature of octopuses render them 

 difficult to observe in their natural 

 habitats. 



The common squid Lol igo opalescens is 

 an infrequent visitor to kelp habitats. 

 It feeds mainly on euphausids and other 

 shrimp-like crustaceans. 



Many species of nudibranchs are 

 commonly seen in kelp forests. The 

 opisthobranchs include some quite colorful 

 species, and provide a striking contrast 

 to the often drab surroundings of their 

 benthic habitats. They feed on sponges, 

 anemones, hydroids, and other 

 opisthobranchs. We have listed only two 

 large species, Navanax inermis and 

 Pleurobranchia cal ifornica (Table 8) . 



Predatory prosobranch gastropods are 

 abundant in kelp forests, particularly 

 around giant kelp holdfasts. The chestnut 

 cowrie Cypraea spadicea feeds on 

 gastropods, ascidians, and anemones. 

 Conus cal ifornicus , the California cone, 

 eats bivalves, polychaetes, gastropods, 

 and various other small animals (Morris et 



68 



