Sampling was done by escalator dredge on 150 ft x 150 ft plots. A plot was 

 considered worked out when harvest rate was less than 1 bu/hr. Total 

 catches/acre varied from 78.5 to bu. Average catch was less than 25 bu/ 

 plot. Growth in the 1968-69 period was the highest recorded since experi- 

 mental planting began in the fall of 1967. Growth is believed correlated 

 with river flow and salinity change. Growth at Hampton Flats was greater 

 than at Gloucester Point and Yorktown. In 1971-72 there was total mortality 

 in upper York River because Agnes reduced salinity to about 1.6°/ 00 for a 

 long period. Littleneck and cherrystone sizes were reached in about 2 1/2 

 and 4 1/2 yrs, respectively, at Hampton Flats, 4 and 8 yrs in lower York River. 

 Growth of planted clams at Wachapreague was underestimated because inadequate 

 numbers were recovered, but far superior to planted western shore clams in 

 1971-72 (salinity at Wachapreague was not affected by Agnes) . - J.L.M. 



2144 



Higgins, William J. 1977. 



5-Hydroxytryptamine-induced tachyphylaxis of the molluscan heart and con- 

 comitant desensitization of adenylate cyclase. J. Cyclic Nucleotide 

 Research 3(4) : 293-302. 



High concentrations of 5HT first excite isolated ventricle of Mevcenavia 

 mevcenavia and then specifically desensitize it to further additions of the 

 neuropeptide. This 5 HT-induced tachyphylaxis is paralleled by a 5HT- 

 specific desensitization of the myocardial adenylate cyclase and a decrease 

 in intracellular eyelid AMP. However, FMRF-NH 2 , a cardioexcitatory tetra- 

 peptide, can still increase contractility, eyelid AMP, and the adenylate 

 cyclase activity of a tachyphylactic -ventricle. These results are consis- 

 tent with the hypothesis that 5HT augments molluscan myocardial contrac- 

 tility by elevating intracellular cyclic AMP. - author's summary - J.L.M. 



2145 



Higgins, William J. 1977. 



Inhibition of protein synthesis does not prevent 5HT-induced tachyphylaxis 

 of the molluscan ventricle or desensitization of adenylate cyclase. Am. 

 Zool. 17(4): 959 (abstract 567). 



High concentrations of 5-hydroxytryptamine (5HT) first excite the isolated 

 ventricle of Mevcenavia mevcenavia and then specifically desensitize it to 

 further additions of the neurohumor. This 5HT-induced tachyphylaxis is 

 paralleled by a 5HT specific desensitization of the myocardial adenylate 

 cyclase and a decrease in intracellular cyclic AMP. The mechanism of de- 

 sensitization and tachyphylaxis was examined using cycloheximide (100 uM) 

 and actinomycin D (20 yM) . Neither agent prevented 5HT-induced desensiti- 

 zation or tachyphylaxis, nor did they alter the time course of the restora- 

 tion of hormone responsiveness following the removal of 5HT. However, both 

 agents inhibited the incorporation of 3 H-leucine into trichloracetic acid- 

 precipitable material, suggesting that in molluscan muscle, unlike many 

 mammalian tissues, desensitization does not depend upon protein synthesis. 

 - modified author's abstact - J.L.M. 



2146 



Hill, B. J. 1976. 



Molluscan viruses: their occurrence, culture and relationships. In Proc. 

 First International Colloquium on Invert. Pathol, and IXth Ann. Meeting, 

 Soc. Invert. Pathol. Printing Dept. , Queens Univ.: 25-29. 



One virus isolate has been obtained from hard clam, Mevcenavia. mevcenavia, 

 from Whitstable in southeast England. The virus designation is CVL-1. 

 There is no firm evidence at present that this group of viruses affecting 

 molluscs can be virulent for their host. - J.L.M. 



597 



