1663 



Shumway, S. E. 1977. 



Effect of salinity fluctuation on the osmotic pressure and Na + , Ca 2+ and Mg 2+ 

 ion concentrations in the hemolymph of bivalve molluscs. Mar. Biol. 41(2)- 

 153-177. 



Mercenaria mercenaria was not investigated. All species studied were 

 osmoconformers. Responses of some species were different when valves were 

 closed than when open. Reference is made to work on M. mercenaria by Hoyeaux 

 et al. (1976), abstracted elsewhere in this bibliography. - J.L.M. 



1664 



Shumway, Sandra E., Peter A. Gabbott , and Arthur Youngson. 1977. 



The effect of fluctuating salinity on the concentrations of free amino acids 

 and ninhydrin-positive substances in the adductor muscles of eight species of 

 bivalve molluscs. J. Exper. Mar. Biol. Ecol. 29(2): 131-150. 



Eight bivalve molluscan species, including Mercenaria mercenaria, were used as 

 test animals, normal and wedged open. Hard clam showed an initial increase in 

 concentration of ninhydrin-positive substance (NPS) in adductor muscle during 

 exposure to decreasing salinity, then a fall in NPS level. These changes were 

 repeated during the second cycle. Increased NPS concentration always occurred 

 as salinity declined, but the subsequent fall in NPS took place immediately 

 following the initial rise in hard clam and some other species, later in the 

 cycle in others. Hard clam was capable of sustained tonic closure, and in 

 normal animals the NPS increase was measured after shell closure had occurred. 

 Wedged-open clams also showed an increase in NPS, at the same time as closed 

 animals. Normal hard clams showed an increase in total free amino-acid (FAA) 

 especially glycine content of adductor muscle tissue after 3 hrs in a 

 sinusoidal salinity profile, but no significant change in NH3. Species like 

 hard clam, oyster, and mussels tend to close their valves when external 

 osmotic concentration reaches a critical level and remain closed until the 

 concentration rises. These species also are less strongly euryhaline than 

 Scrobicularia plana and Mya arenaria. Valve closure will produce tissue 

 hypoxia, and this could account, partly at least, for observed increases in 

 the FAA pool. At the same time, reductive amination of keto-acid intermediates 

 will prevent accumulation of ammonia. It is suggested that NPS and FAAs are 

 used as osmotic effectors in marine bivalves exposed to constantly lowered 

 salinities, but are not used for the same purpose under cyclic salinity 

 changes. - J.L.M. 



1663 



Shuster, Carl N. , Jr. 1954. 



A method for recording measurements of certain molluscs, arthropods, and 

 fishes. Prog. Fish- Culturist 16(1): 39-40. 



The method includes enclosure of graph paper within a protective jacket of 

 aluminum foil. - J.L.M. 



1666 



Shuster, Carl N. , Jr. 1957. 



On the shell of bivalve mollusks. Proc. Natl. Shellf. Assn. 47: 34-42. 



Shells usually were prepared for sectioning by embedding in gypsum and cutting 

 with a hacksaw or carborundum circular saw. Cut edges were smoothed on a glass 

 plate covered with water and carborundum powder and polished with cleansing 

 powder. Some shells were treated with diluted HC1 or CH3COOH. The laminated 

 structure of Mercenaria mercenaria shell is clearly visible. Prominent laminae 

 of translucent material in the inner portion of the shell pass to the outer 

 surface through two regions of opaque shell of different color and texture. 

 The outer opaque region is cream-colored and not as hard as the inner. Purple 



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