278 



Carriker, Melbourne R. 1956. 



Biology and propagation of young hard clams, Mercenaria mercenaria. j 

 Elisha Mitchell Sci. Soc. 72(1): 57-60. 



Hard clam embryos developed into shelled, free-swimming veligers with a 

 velum in 24 hours after fertilization. In about 7 days the veligers 

 developed a foot and became pedoveligers . Pedoveligers exhibited searching 

 behavior. Soon a byssal gland formed and the velum was lost. Young clams' 

 alternated between byssal attachment and crawling for the next few weeks. 

 When clams grew to 7 mm the byssal gland became functionless and the foot 

 was used for maintaining position. Shortly after pedoveliger settled, 

 mantle edges fused and formed siphons which allow clam to burrow. Clams 

 were spawned artificially and larvae cultured in field laboratories. 

 Larvae were fed Chlorella and extracts of cereal pablum. The pedoveliger 

 stage was reached in 10-14 days. Only occasional cultures reached the 

 byssal stage. Hydrography of Home Pond was studied for its use for large- 

 scale hard clam culture. It was suggested the inlet to the pond be closed 

 at the onset of spawning season to prevent larvae being flushed out of the 

 pond. Clams were subject to excessive predation by mud, green, and blue 

 crabs. Larger clams are less vulnerable to predation than smaller ones. 

 Screening was found to be partly effective in protecting young clams from 

 predation. - D.L. 



279 



Carriker, M. R. 1957. 



Preliminary study of newly hatched oyster drills, Urosalphynx cinerea, 

 J. Elisha Mitchell Soc. 73: 328-351. 



Newly hatched drills reacted positively to external metabolites of newly set 

 Venus mercenaria. Clams were located readily by drills. A drill 1.5 mm 

 high perforated a Venus 0.6 mm long in 45 min, and removed the flesh in 

 another 45 min. In a day, one young drill consumed 1 to 19 young Venus. 

 Young drills can crawl through superficial layers of sediment; thus, young 

 clams cannot escape predation by burrowing shallowly. In the natural 

 environment buffer-food species probably reduce this predation rate. - J.L.M. 



280 



Carriker, Melbourne Romaine. 1959. 



The role of physical and biological factors in the culture of Crassostrea 

 and Mercenaria in a salt-water pond. Ecol. Monogr. 29(3): 219-266. 



Densest populations of Venus mercenaria lived in the vicinity of the inlet, 

 where continuous recruitment of young took place. An unusual population of 

 old Venus with maximum lengths of 5.5 inches was discovered in the head of 

 the pond. Venus and oysters, especially at the head of the pond, retained 

 conspicuous stores of glycogen throughout summer, indicating excellent food 

 conditions, which may be associated with high fertility of sediments and 

 minimal exchange in the upper portions. Venus grew fastest in the vicinity 

 of the inlet. Most spawning of Venus occurred in late spring, slight 

 spawning in summer, with a moderate peak in August. Most larvae settling 

 within the pond entered from the bay as veligers. Venus larvae set most 

 abundantly in the inlet, decreasing up the axis of the pond. Newly set 

 Venus are well adapted to survival in the unstable bottom conditions of an 

 inlet. Callinectes sapidus and xanthid mud crabs were the most conspicuous 

 predators. Unprotected young Venus were almost completely destroyed by 

 crabs in portions of the pond away from the inlet. As Venus grew larger 

 they became less vulnerable. Unstable sediments and swift currents in the 

 inlet provided protection. Over 80% survival of young Venus was obtained 

 in enclosures in contrast to negligible survival in the open, except in the 

 inlet, where about 40% of Venus survived. Larvae could be retained within 

 the pond by closing the inlet temporarily just before spawning and during 

 the larval period. It should be reopened as soon as spawning is complete. 

 - J.L.M. 



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