marized by Dow and Wallace (1961), suggest 

 that this condition may be a general sign of 

 physiological disturbance.) Uzmann considered 

 C. myae to be the same species as that reported 

 by Stafford (1912) from the soft-shell clam in 

 the Gulf of Saint Lawrence. Hutton (1953) 

 believed that the larvae were members of the 

 genus Gymnophallufi. Stunkard and Uzmann 

 (1958) discussed gymnophallid sporocysts and 

 cercariae from the soft-shell clam, and Stunk- 

 ard (1960) found echinostome metacercariae 

 of the genus Himasthla in palps and gills of 

 clams from the Maine coast. Three species were 

 recognized. Earlier, Stunkard (1938) had dem- 

 onstrated experimentally that cercariae of 

 Himasthla would penetrate and encyst in the 

 gills of Mya arenaria and a number of other 

 bivalves, and Uzmann (1951) had reported 

 natural occurrence of Himasthla quissetensis 

 (Miller and Northrup) in M. arenaria. Sus- 

 ceptibility and response of a number of marine 

 pelecypods, including four species of clams, to 

 cercariae of H. qnissetensis was tested experi- 

 mentally by Cheng, Shuster, and Anderson 

 (1966). Metacercariae were found in all clams 

 and mussels but not in oysters used in the 

 study. 



Several larval trematodes have been reported 

 from clams of the genus Donax. Giard (1897, 

 1907) identified bucephalid and gymnophallid 

 cercariae. Rees (1939) found gymnophallid 

 metacercariae, and Young (1953) described the 

 life cycle of a monorchid, Postmonorchis dona- 

 cis, whose larvae occur in the California bean 

 clam. Hopkins (1958) identified sporocysts and 

 cercariae of three species, and metacercariae 

 of two .species, in coquina clams, Donax varia- 

 bilis Say, from the Texas coast. Infections by 

 larval trematodes were considered by Pelseneer 

 (1896, 1906, 1928) to be responsible for re- 

 duced abundance of Donax vittatus in France, 

 and Coe (1946) held that trematode parasites 

 (probably Postmonorchis donacis) were impor- 

 tant in controlling population size in California 

 Donax gonldi. 



Fujita (1906, 1907, 1913) has described two 

 larval trematode parasites of asari clams, Tapes 

 philippinarnm Adams and Reeve, from Japan. 

 Parasitic castration of the hosts was ob.served. 



Hopkins' (1957a) brief but excellent exposi- 

 tion of the role of parasitism in marine com- 



munities referred to an interesting interrela- 

 tionship of host, parasite, and hyperparasite in 

 the case of Donax trnnciilus parasitized by 

 trematodes, which in turn were parasitized by 

 the haplosporidan lU-osporidinm pelseneeri 

 (Caullery and Chappellier). The often severe 

 fluctuations in abundance of this clam have 

 been attributed to shifts of balance in this 

 tripartite relationship (Caullery and Chappel- 

 lier, 1906; Cepede, 1911). Other haplosporidan 

 and microsporidan hyperparasites of Donax 

 have also been described (Guyenot, Naville, and 

 Pon.se, 1925; Dollfus, 1946; Mackin and Loe.sch, 

 195")). 



MacGinitie and MacGinitie (1949) surveyed 

 a number of species of clams from the Pacific 

 coast of the United States for parasitization by 

 larval tapeworms. Encysted larvae of the ces- 

 tode genus Anabothrinm were found, occasion- 

 ally in large numbers, in the foot mu.scles of 

 the gaper clam, Schizothaerus nuttallii Conrad. 

 The definitive host of the Anabothrinm sp. 

 found in clams was identifie-'. by MacGinitie 

 and MacGinitie as the bat stingray, Myliobatis 

 californicus. 



Sparks and Chew (1966) described remark- 

 able levels of parasitization of littleneck clams, 

 Venernpis staminea (Conrad), from Humboldt 

 Bay, Calif., by larval tetraphyllidean cestodes 

 of the genus Echencibothrinm. Cy.sts of the 

 worm were closely packed throughout the tissues 

 of the clams, which were abnormally exposed on 

 the surface of gravel beds. Adult Echeneiboth- 

 rium, with bothridia similar to tho.se of larvae 

 in clams, were found in bat stingrays caught 

 in the same area. 



Diseases ("oused by Parasitic Oiistaceans 



Clams, like certain other bivalves, harbor 

 parasitic copepods. Hoshina and Kuwabara 

 (1959) described Mi/tilicola mactrac from Jap- 

 anese Mactra veneriformis Reeve. About half 

 the clams in a sample of 69 were infested. 

 Yamaguti (1939) described another species 

 from Bnichidontcs senhausi (Reeve), and 

 Humes (1954) found M. porrecta in a single 

 hard clam, Mercenaria niercenaria (L.), from 

 the Gulf of Mexico. 



Tumors 



Hueper (1963) reported cauliflowerlike pap- 

 illary tumors at the anterior end of soft-shell 



350 



U.S. FISH AND WILDLIFE SERVICE 



