a decrease in the size of the adductor muscle. 

 There were also indications of a postspawning 

 die-off on the Cape Kennedy grounds (Roe, Cum- 

 mins, and Bullis, 1971). 



For the Cape Kennedy grounds, average 

 monthly mortality rates, primarily natural, cal- 

 culated for the period December to October were 

 about 20 '^r (Roe, Cummins, and Bullis, 

 1971). 



Associated Organisms 



Plants and animals associated with the calico 

 scallop undoubtedly influence its setting, growth, 

 and survival. 



Calico scallops have been reported to occur in 

 beds of turtle grass, Thalassia testudinum, in 

 Bermuda (Kirby-Smith, see footnote 3). 



Marine animals associated with the calico 

 scallop are categorized as follows: epifaunal 

 and endofaunal community (Wells, Wells, and 

 Gray, 1964) ; benthic invertebrates (Grassle, 

 1967); crustaceans (Hulings, 1961); mollusks 

 (Wells, Wells, and Gray, 1961; Hulings and 

 Hemlay, 1963; Porter and Wolfe, in press) ; echi- 

 noderms (Wells, Wells, and Gray, 1961, 1964; 

 Hulings and Hemlay, 1963; Gray, Downey, and 

 Cerame-Vivas, 1968) ; and fishes (Moe, 1963; 

 Anderson and Gehringer, 1965; Struhsaker, 

 1969a). A few animals associated with calico 

 scallops on the Cape Kennedy grounds are shown 

 in Figure 6. 



Marine invertebrates that live on and in the 

 calico scallop "probably reduce growth or repro- 

 ductive potential . . . rather than cause the scal- 

 lop's death," according to Wells, Wells, and Gray 

 (1964). Sindermann (1971) reported, however, 

 that "barnacles, tube worms, and corals can re- 

 duce survival of calico scallops." We have noted 

 that fouling by barnacles may prevent complete 

 closure of the valves and thus predators can be 

 admitted more easily (see footnote 2). 



Invertebrates reported as parasites (in some 

 cases, commensals) of the calico scallop are a 

 nematode Porrocaecum pectinis (Hutton, 1964); 

 a trematode Procfoeces sp. (Sindermann)"; the 



" Carl J. Sindermann, Laboratory Director, National 

 Marine Fisheries Service, Northeast Fisheries Center, 

 Sandy Hook Laboratory, Highlands, N.J. 07732. Per- 

 sonal communication, 1970. 



polychaetes Ceratonereis tridentata and Poly- 

 dora websteri (Wells and Wells, 1962) ; the 

 decapod crustaceans Pontonia margarita and 

 Pinnotheres maculatus (Wells, Wells, and Gray, 

 1964); and the gastropod mollusks Odostomia 

 seminuda (Wells and Wells, 1961) and Odosto- 

 mia bisutalaris (Cheng, 1967). 



Predators of the calico scallop are poorly 

 known and observations on food habits of the 

 many associated species would be useful. Re- 

 ported as known predators are the starfishes 

 Astropecten articukttus (Wells, Wells, and Gray, 

 1961) and Asterias (Roe, Cummins, and Bullis, 

 1971), and puffers Sphoeroides (Roe, Cummins, 

 and Bullis, 1971). Scallops held in cages on the 

 Cape Kennedy grounds were drilled by unidenti- 

 fied gastropod mollusks (see footnote 2). 



Reported as possible predators are the gastro- 

 pod mollusks Cantharus multangulus and Murex 

 fulvescens (Wells, Wells, and Gray, 1964); and 

 the thorny stingray Dasyatis centroura (Struh- 

 saker, 1969b). In addition, the Florida horse 

 conch Pleuroploca gigantea and an unidentified 

 octopus may be predators (see footnote 2). 



Behavior 



Calico scallop larvae are planktonic and appar- 

 ently occur at all levels in the water column 

 since young scallops were found attached to 

 fouling arrays distributed from surface to bot- 

 tom in 46 m of water in the northeastern Gulf 

 of Mexico (Pequegnat and Pequegnat, 

 1968). 



Small calico scallops attach byssally to a va- 

 riety of surfaces, including mollusk shell, tile, 

 and various synthetic materials. Although bys- 

 sal attachment is most pronounced in small scal- 

 lops (those less than about 25 mm in height), 

 scallops up to about 54 mm in height attached 

 to a fiber glass-coated water table (Allen, see 

 footnote 8) . 



Several observations have been made on the 

 swimming activity of the calico scallop. Accord- 

 ing to Mellon (1969), the calico scallop "has 

 heavy valves and swims only rarely." Zahl 

 (1969) reported, however, that the calico scal- 

 lop is a "champion" swimmer. From a submer- 

 sible on the Cape Kennedy grounds, "sporadic" 

 swimming by some calico scallops was noted al- 



io 



