1048 



Langston, W. J. 1978. 



Persistence of polychlorinated biphenyls in marine bivalves. Mar. Biol. 

 46(1): 35-40. 



Elimination of dichlorobiphenyl from Cerastoderma edule was much more rapid 

 than from Macoma balthioa or Mercenaria mercenaria. - J.L.M. 



1049 



LaRoche, Gilles, G. R. Gardner, Ronald Eisler, E. H. Jackim, P. P. Yevish, and 

 G. E. Zaroogian. 1973. 



Analysis of toxic responses in marine poikilotherms. In Bioassay techniques 

 and environmental chemistry. Gary E. Glass (edj . Ann Arbor Sci. Publishers, 

 Inc., Ann Arbor, Mich.: 199-216. 



Short-term bioassays and field observations are valuable in identifying 

 toxicological responses, but realistic appraisal of environmental exposure 

 also is necessary. Subtle damage which could affect survival should be 

 sought and identified. Fig. 2 8 shows gill areas of a control Mercenaria 

 mercenaria illustrating in histological section the ciliated gill lamellae. 

 Fig. 29 shows changes produced by as little as 0.25 mg/1 or 250 mg/1 (ppb) 

 of CUCI2 over 96 hrs . The ciliated columnar cells at tips of gill lamellae 

 have disappeared. Columnar epithelium appears to have been replaced by 

 cuboidal cells, which may be interpreted as an aspect of the regenerative 

 process from destructive action of Cu + +. Without cilia, it is realistic to 

 conclude that the clam would starve. Anatomical 'changes suggest that loss 

 of cilia would limit survival in an animal exposed to sublethal concentrations 

 of CuCl2- - J.L.M. 



1050 



Larsen, Peter F. 1979. 



The distribution of heavy metals in the hard clam, Mercenaria mercenaria, 

 in the lower Chesapeake Bay region. Estuaries 2(1): 1-8. 



Populations of hard clam were sampled at 30 sites in lower Chesapeake Bay 

 in 1972 and 1973. Subsamples were taken for analysis of cadmium, copper, 

 and zinc. Highest values of all three metals occurred in the James River. 

 Absolute levels, in parts per million, varied from zero to 0.8 for cadmium, 

 1.1 to 7.9 for copper, and 5.0 to 112 for zinc. Relatively high and re- 

 latively low values often occurred within the same sample. Concentrations 

 of zinc are generally comparable to those found by others in the U.S. and 

 Britain. Broader ranges in Chesapeake Bay were caused by larger numbers of 

 sites and individuals sampled. Average copper values also were comparable 

 from all North American sites, but higher concentrations were found by 

 others in the U.S. and U.K. Average values of cadmium were also comparable, 

 except for one published in the U.K. The higher levels in the James River 

 shows that this river probably is contaminated by these metals. Salinity 

 of the sampling site must be considered before cadmium and zinc data can be 

 interpreted. A standard action-level would be adequate to denote pollution 

 by copper. - J.L.M. 



1051 



Lavelle, S. M. 1970. 



Observations on the anti-growth activity of Mercenaria clam extract. 10th 

 Internatl. Cancer Congr. , Abstr. 1298: 789. 



Deep-frozen extract of Mercenaria (mercenene) was tested for effect on growth 

 of methylcholanthrene tumors, promotion and initiation of 2-stage carcino- 

 genesis of mouse skin, regeneration of amputated newt forelimb, and healing 

 of through wounds of rabbit ear. Extract was applied twice daily to test 

 areas. Mercenene reduced growth of tumors in initiated and promoted skin, 

 and slowed regeneration and wound repair. It had less action on complete 

 carcinogenesis. Mercenene appears to contain a general inhibitor of growth. 

 - J.L.M. 



294 



