prepared in subsequent work — was reported to 

 reproduce the disease experimentally. 



Significant mortalities of lobsters accomi)a- 

 nied the shell disease; Taylor (1948) found 

 that 71 percent of infected captive lobsters died 

 from the disease, but observed no correlation 

 between mortality and intensity of external 

 shell erosion. Contraction of the disease by 

 healthy lobsters placed in sea-water tanks with 

 infected individuals indicated direct transmis- 

 sion. The disea.se develojied slowly, requiring at 

 iea.st 3 months before the advanced stages were 

 reached. Progress of chitin destruction was di- 

 rectly tem|)erature-dependent, and new shell 

 laid down after molting was not affected, ex- 

 cept by reinfection. 



Sawyer and Taylor (1949) observed that 

 shell disease produced thickening oi- complete 

 destruction of the chitinous layer of the gill 

 filaments. No living gill tissue was attacked, 

 but the authors postulated respiratory impair- 

 ment as an important consequence of the dis- 

 ea.se. The infection appeared to be entirely ex- 

 ternal, confined to the exoskeleton. and not 

 invading living tissue nor transmitted intern- 

 ally. Sawyer and Taylor also reported the dis- 

 ease to be present on the Maine coast as well 

 as in Canada, and considered it a potential 

 threat to the lob.ster industry, in view of the 

 ease of transmission and the observed mortali- 

 ties of captive individuals. The method of in- 

 fection of lobsters is unknown; lodging of 

 bacteria in pores and ducts of the shell was 

 proposed l)y Sawyer and Taylor as a route of 

 invasion. 



Another recently recognized disease of lob- 

 sters from the Maine coast, probably of fungus 

 etiology, is called "mottling disease." Charac- 

 terized by yellowish splotches in an otherwise 

 dark green exoskeleton (fig. 9), the condition 

 has been known for many years as a color vari- 

 ation. Affected individuals are called "leopard 

 lobsters" (Herrick. 1895, 1911). The shell con- 

 dition and color result from progressive growth 

 of areas of necrosis in underlying tissues and, 

 in advanced cases, even blisters of the shell. 

 The areas of necrosis expand slowly in lobsters 

 held in sea water tanks. Our histological ex- 

 amination of disea.sed tissues disclo.sed numer- 

 ous Schiff-positive, subspherical, heavy-walled 

 bodies 30 to 60/, in diameter. Tentatively, the 



Figure 9. — "Leopard lobster" with external signs of 

 mottling disease. 



organism is considered a chytrid fungus. Pre- 

 liminary attemj)ts at culture and transmission 

 have been unsuccessful. The disease occurs in- 

 fre(|uently in Gulf of Maine lobster populations 

 and has not been reported from other areas. 



Danncvig (1928, 1939) in a report on Nor- 

 wegian lobster hatcheries, described infection 

 and destruction of eggs on the female by the 

 suctorian Ephelota <icmmipura Hertwig. The 

 protozoan was found on newly caught individ- 

 uals, and increased tremendously on lobsters in 

 hati'hing boxes. Dannevig attributed substan- 

 tial decrea.ses (90 percent) in production of 

 larvae to the effects of the parasite. The organ- 

 ism was abundant only in certain years. 



358 



U.S. I-ISH AND WlLULllE SERVICE 



