1800 



Thompson, V. P., W. H. Johnson, and J. L. Katz. 1971. 



The large filaments from catch muscles: pH and ionic strength dependence of 

 aggregation. Biophys . Soc. , Progr. and Abstr. , 15th Ann. Meeting: 205a 

 (Abstract WPM-L15) . 



Large filaments (500-1,500 A diam) can be isolated from white adductor muscle 

 of Meraenaria meraenaria. These filaments form long (200-500 u) longitudinally 

 oriented aggregates as pH is lowered from 7.0 to 6.3. Preparations of purified 

 large filaments were made by centrif ugation at ionic strength 0.02-0.10. Actin, 

 then myosin, were removed selectively by varying pH and ionic strength in 

 presence of ATP-EGTA. Ionic strength requirements for aggregation follow in 

 general the solubility curve for ethanol-extracted paramyosin. Native 

 filaments (with myosin on the surface) showed a shift of pH of aggregation with 

 ionic strength, which differs from that of paramyosin filaments (with myosin 

 removed) . When temp was raised from usual 2 to 4°C to 25°C, native and 

 paramyosin filaments, as well as ethanol-extracted paramyosin solutions, 

 aggregated in a narrow range of pH (7.0 to 6.8) as pH was lowered from 7.0, 

 suggesting a strong similarity between behavior of pure paramyosin and 

 filaments containing this protein. Presence of actin does not appear to 

 alter aggregation properties of filaments. - modified authors' abstract - 

 J.L.M. 



1801 



Thorson, Gunnar. 1956. 



Marine level-bottom communities of recent seas, their temperature adaptation 

 and their "balance" between predators and food animals. Trans. N.Y. Acad. 

 Sci., Ser. II, 18(8): 693-700. 



Animals that live on the bottom of the sea fall into 2 distinct ecological 

 groups, epifauna and infauna. Epifauna are much more diverse, including more 

 than 4/5 of all bottom-dwellers. For hundreds of millions of years the small 

 numbers of genera that make up the infauna, and live in uniform level-bottom 

 areas, must have covered much larger and more uniform areas than the epifaunas. 

 These infauna will provide the "guide fossils" of our period. Whereas typical 

 epifaunal groups show a marked increase in number of species from Arctic to 

 tropical seas, pronounced infaunal groups seem not to increase from high to 

 low latitudes. In sandy bottoms in shallow water are found "chains" of 

 parallel Venus communities, different species replacing each other with 

 latitude and temp. An Arctic community at 0°C shows roughly a similar 

 metabolic rate, similar rate of growth, and similar feeding habits, as a 

 boreal community at 8°C or a Mediterranean community at about 12 °C, or a 

 tropical community at a higher temp. Thus, observations on predation, mode 

 of feeding, competition, or growth made at any specific coastal area may be 

 of direct help in explaining similar phenomena in other similar communities. 

 The author describes how modern experience with level-bottom communities might 

 be used by paleoecologists to understand a prehistoric level-bottom community, 

 for example by study of shells found in a fossil bed. Teamwork in conducting 

 coordinated studies of level-bottom communities worldwide, or even around the 

 coasts of the United States, would yield much valuable knowledge. - J.L.M. 



1802 



Thorson, Gunnar. 1958. 



Parallel level-bottom communities, their temperature adaptation, and their 

 "balance" between predators and food animals. In Perspectives in Marine 

 Biology. A. A. Buzzati-Traverso (ed.). Univ. Calif. Press, Berkeley: 67-86. 



Series of parallel Venus communities, dominated by Venus and Spisula or 

 Mactra, are known from sandy bottoms in shallow water from East Greenland, 

 western Atlantic coast, North Sea, Mediterranean, and Persian Gulf. Each 

 shows uniform features qualitatively and quantitatively, irrespective of 

 latitude. A sandy, muddy, or mixed bottom has roughly the same appearance 

 and structure in cold or warm seas, and contains roughly the same number of 

 invertebrate species per square unit in the Arctic or the tropics. The only 

 fundamental difference is temp of water. Most marine invertebrates are 

 totally adapted, or nearly so, to temps at which they normally occur. This 

 applies especially to different species of the same genus that replace each 



498 



