crabs, and cultured organisms produced the 

 disease experimentally in normal crabs. Similar 

 bacteria were also isolated from sea water in 

 Kachemak Bay. The authors concluded that the 

 disease would not affect the commercial fishery 

 seriously unless the catch of crabs was substan- 

 tially less than annual recruitment, since larger 

 individuals, which do not molt .mnually, were 

 more frequently infected. 



Fitiigi. — Eggs of blue crabs from lower 

 Chesapeake Bay were found to be parasitized 

 by a fungus Lagenidinm callinectes Couch 

 (Couch, 1942; Sandoz, Rogers, and Newcombe, 

 1944; Sandoz and Rogers, 1944; Newcombe and 

 Rogers, 1947; Rogers-Talbert, 1948). Infected 

 eggs either failed to hatch, or gave rise to ab- 

 normal zoea larvae. Infection levels were as 

 high as 90 percent of a sample of ovigerous 

 female crabs, and up to 25 percent of the eggs 

 in a "sponge" (egg mass). Penetration of the 

 egg mass was slow and did not exceed 3 mm. 

 This fact, combined with the short (2-week) 

 incubation time, permitted normal development 

 of much of the egg mass internal to the infec- 

 tion. Experimentally, the fungus developed 

 normally in salinities from 5 to 30 o oo. The 

 fungus was transmitted experimentally to the 

 eggs of two other species of crabs (the oyster 

 crab and the mud crab, Neopanope texiana 

 Rathbun) inhabiting the same Bay area. 



Pea crabs (Pinnotheres) taken from the sea 

 mussel at Plymouth, England, were parasitized 

 by the fungus Leptoleguia marina (Atkins, 

 1929, 1954a). The mycelium was usually found 

 in the gills but penetrated other body organs 

 and appendages as well. Zoosporangia devel- 

 oped in the appendages, and large numbers of 

 zoospores were released upon the death of the 

 host. No further growth of the fungus took 

 place in dead crabs, and no external develop- 

 ment, beyond papillae of zoospore exit tubes, 

 was seen. Atkins (1954b, 1955) described two 

 other fungi, Plectospira dubia and Pijthium 

 thalassiion, which infect eggs of pea crabs and 

 other Crustacea. 



Protozoa. — Gregarines are common parasites 

 of many Crustacea, and an extensive and at 

 times confusing literature has accumulated. 

 Many members of the group have been reported 

 from crabs. For example, species of the genus 

 Cephaloidophora occur in spider and fiddler 



crabs of the United States east coast (Watson, 

 1915, 1916a, 1916b; Kamm, 1922), in the 

 striped shore crab, Paclnjurapsus crassipes, of 

 the Pacific coast, and in the Mediterranean 

 "flat crab," Pachi/(iraj}siis t)ion)io)'atiis (Ball, 

 1938; Theodorides, 1961, 1962). As mentioned 

 in the discussion of oyster diseases, several 

 representatives of the genus Nemafopsis occur 

 in Atlantic species of mud crabs ( Prytherch, 

 1940; Ball, 1951; Sprague and Orr, 1955). Al- 

 though the gregarines are not usually consid- 

 ered serious pathogens of Crustacea, Ball 

 pointed out that masses of the parasites may 

 occlude the lumen of the intestinal caeca and 

 may cause sloughing or thinning of the 

 epithelium. 



Several microsporidans are parasites of 

 crabs. Sprague (1965a) described a species of 

 Nose ma parasitic in muscles of the blue crab. 

 Infected muscles became opaque with a coarse 

 fibrous texture, and heavy infections caused 

 lysis of myofibrils. He considered the parasite 

 to be common and widespread in Chesapeake 

 Bay, and believed it might be a significant fac- 

 tor in crab mortality. Sprague (1966b) also 

 described Plistophora cargoi from the skeletal 

 and cardiac muscles of a single blue crab from 

 the Patuxent River, Md. Earlier, Perez (1905a, 

 1905b) reported Nosema pidvis in the muscles 

 of the green crab, Carcinus maevas (L.), and 

 Perez (1907) also described ovarian infections 

 with a microsporidan, Thelohania niaoiadis. in 

 green crabs from Arcachon, France. The para- 

 site normally occurred in the body mu.scles. 



Ciliates are also significant parasites of 

 crabs. Serious mortalities of molting blue crabs 

 from Chesapeake Bay occurred in the summers 

 of 1965 and 1966. Their gills had a massive 

 infestation of peritrichous ciliates (fig. 7) of 

 the genera Lagenophnjs and Episti/his (Couch, 

 1966, 1967a). Mortalities were mo.st severe 

 among crabs in holding tanks just before or 

 after molting, but wild crabs were also heavily 

 infested, and fishermen reported mortalities. 

 Infestations of gills frequently seemed heavy 

 enough to interfere with respiration. 



Another ciliate, Anophnjs sarcophaga Cohn, 

 is found in the blood of green crabs. Originally 

 described as a free-living form (Cohn, 1866), 

 it was first seen in the blood of crabs by Cat- 

 taneo (1888). Poisson (1930) described the 



DISEASES OF THE MARINE BIVALVE MOLLUSCA AND CRUSTACEA 



353 



