866 



Hopkins, Hoyt S. 1924. (Vol. 29 of Anat. Rec. is dated 1925 but the issue 

 no. 2 was dated Dec. 1924J 



Respiration in the tissues of mollusks in relation to age. Anat. Rec. 29(2): 

 91 (abstract) . 



Amounts of 02 used by excised adductor muscle of Venus meraenaria of similar 

 dimensions is proportional to surface area rather than mass, which suggests 

 that O2 is utilized mainly at the surface. Rates are higher for muscles of 

 small clams. Assuming that rings on shell of Venus are laid down annually, 

 it appears that tissue metabolism is inversely proportional to age, high in 

 young animals (2-5 yrs old) , falling off to nearly 1/3 in clams over 10 yrs 

 old. Using adductor muscle has an advantage over using intact living animals 

 by eliminating the effects of nervous system, blood supply and hormones on 

 metabolism. - J.L.M. 

 867 



Hopkins, Hoyt S. 1930. 



Age differences and the respiration in muscle tissues of mollusks. J. Exp. 

 Zool. 56(2): 209-239. 



Study of excised adductor muscles of Venus meraenaria showed a falling off in 

 oxygen respiration with age, which was not accounted for by changes in amount 

 of active indophenol peroxidase. Rate of respiration and peroxidase content 

 were greater in "closing" muscle than in non-striated, nacreous portion of 

 adductor. Respiratory rate in the 2 kinds of muscle in adductor was 

 correlated with their catalase activity. It was assumed that red portion of 

 the adductor of Venus was closing muscle, and thus probably displays more 

 activity than the white part. Its homologue in bay scallop, Peeten irradians , 

 is the striated portion of adductor. Unlike its homologue in scallop, red 

 muscle appears to retain its tonic properties in large measure, thus differs 

 little from white muscle. Red muscle of Venus was higher in catalase than 

 white. Respiration was somewhat higher in red than in white adductor muscle. 

 Peroxidase activity was considerably higher in red than in white muscle. 

 Various workers have differed as to whether age can be determined accurately 

 from concentric lines of growth on external surface of Venus shell. When the 

 valve is broken across from umbo to margin a stratified nacreous layer is 

 exposed which has alternate lamellae of bluish-white and cream-colored 

 material. Cream-colored strata correspond to concentric ridges on the surface, 

 bluish-white to depressions between. The inner shell surface of clams 

 collected alive in summer almost always has some color, thus the pigment may 

 be derived from abundance of plant food ingested in summer. Study of nearly 

 700 shells by this method detected all ages up to 24 yrs. A few had 40 or 

 more growth layers, so thin near the margin that interpretation was difficult. 

 These apparently old clams were only about 8 cm long, whereas the largest 

 collected (11 to 14.5 cm) rarely exceeded 20 yrs, which suggested that great 

 size is incompatible with long life. This may be an illustration of Rubner's 

 principle, in which length of life is inversely proportional to rate of 

 metabolism. Causes of differences in rate of growth of hard clam have not 

 been determined. - J.L.M. 



868 



Hopkins, Hoyt S. 1934. 



Catalase and oxidative processes in animal tissues as possible factors in 

 adaptation. Biol. Bull. 67(1): 115-125. 



O2 consumption of thin sections of muscle in seawater saturated with O2 

 varied widely between species. Venus meraenaria in 2 hrs at 27.5°C used 

 33.8 mm 3 /g of tissue/hr, V. aampechiensis 28.9 mm 3 (6 and 4 experiments 

 respectively) . Inadequate diffusion of O2 into tissue seemed to be 

 unimportant as a factor limiting rate of O2 consumption. Depletion of 

 catalase in unsectioned muscle during 4 hrs after excision did not exceed 

 10%. In 60 experiments with 30 Venus meraenaria (290 mg of muscle) C7 used 

 was 38.5 mm 3 /g/hr, catalase 19.8 mm 3 /g/hr, ratio 02/catalase 2.16-0.80; 12 

 experiments with 10 V. campeahiensis (289 mg muscle) used 35.6 mm-vg/hr Oj 

 and 11.5 mm3/g/hr catalase, ratio 02/catalase 4.33*1.83. V. meraenaria did 

 not bear mutilation well; removal of a shell segment without visible injury 



242 



