Instead, they continued to grow and many retained a functional velum until 

 260-270 ]i even though they also had a well-developed foot and gills. Thus, 

 clam larvae may under certain conditions grow considerably larger than the 

 size at which metamorphosis usually is complete. In all the other 

 experiments the larvae metamorphosed in 10 to 12 days. In 5 yrs of culture 

 work no larva larger than 240 u with a functional velum had been seen. - J.L.M. 



452 



Davis, H. C. f and V. L. Loosanoff. 1955. 



A fungus disease in bivalve larvae. Proc. Natl. Shellf. Assn. 45: 151-156. 



An organism tentatively identified as a fungus was found in many dead or 

 dying larvae of Venus mortoni and hybrids of V. movtoni and V. meTcenari,a. 

 In many clam larvae, growth occupies a large proportion of the space within 

 the larval shell, so crowded together that details of thallus organization 

 cannot easily be seen. Segments of the thallus mature into sporangia, each 

 with an exit tube which releases zoospores to the surrounding water. A few 

 infected larvae were found in many cultures. Only in a few cases did fungus 

 become epizootic, but then within 2 to 4 days killed most of the culture. 

 Larvae of all ages have been found parasitized. Optimum temp and salinity 

 are not known, but all cultures have been about 19-27°C and 21°/°°. Most 

 infected larvae soon drop to the bottom, stop growing, and die. The fungus 

 has been identified tentatively as Sivolpidium sp. Attempts to control 

 fungus with fungicides and ultraviolet light were not successful. - J.L.M. 



453 



Davis, H. C, and R. Ukeles. 1961. 



Mass culture of phytoplankton as foods for metazoans. Science 134(3478): 

 562-564. 



454 



Davis, H. C, V. L. Loosanoff, and C. L. MacKenzie, Jr. 1961. 



Progress in development of methods of chemical control of shellfish 

 predators: Field tests of a chemical method for the control of marine 

 gastropods. U.S. Fish Wildl. Serv. , Biol. Lab., Milford, Conn., Bull. 

 25 (3) : 3-9. 



Solutions of Sevin in orthodichlorobenzene (O.D.) were mixed with sand as 

 an inert carrier and spread on shellfish grounds in Long Island Sound and 

 Great South Bay. Gastropods of all kinds were affected strongly. The foot 

 swelled greatly and snails were immobilized with the swollen foot extended, 

 soon to be attacked by fishes, crabs, and sea stars. Sea Stars were 

 affected but not killed. Most other animals, including hard clam and oyster, 

 were affected little or not at all, and treatment appeared to have no 

 effect on setting of oysters or sea stars. It was emphasized that this is 

 primarily a method of control, not complete eradication. J.L.M. 



455 



Davis, K. C, V. L. Loosanoff, W. H. Weston, and C. Martin. 1954. 



A fungus disease in clam and oyster larvae. Science 120(3105): 36-38. 



Larvae of Venus meroenavia are especially suitable for experimental work. 

 Usually they can be cultured through metamorphosis without difficulty. 

 Heavy occasional mortalities appear to be associated with a fungus 

 organism. The fungus appeared to be endemic in cultures, a few infected 

 larvae appearing in many experimental lots. Preliminary observations 

 showed certain distinctive features. Larvae of all stages of development 

 may be infected, as well as juvenile quahogs . Culture temps ranged from 

 19 to 27°C at salinity approximately 21°/°°. Once infected, most larvae 

 stop growing and die. It is not known if infected larvae can recover and 

 develop normally. Fungus is transmitted by biflagellate zoospores which 

 are released to the exterior of infected larvae. Within larvae, fungus 

 develops as a contorted, looped, and sparsely branched torulose thallus with 

 constrictions at intervals between swollen and often lobed segments. Seg- 

 ments mature into sporangia, each with a zoospore exit tube to the exterior, 



127 



