A field survey of hematopoietic neoplasia (Hn) in the soft shell clam Mya arenaria (L.) was undertaken using an immunoperoxidase diagnostic technique.

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The objectives of this study were to: (1) determine which fishes were consistently eating zebra mussels Dreissena polymorpha in Lake Champlain and document their feeding behaviour and (2) quantify the diet composition of the fish predators that were found to consume zebra mussels. From 2002 to 2005, freshwater drum Aplodinotus grunniens, pumpkinseed Lepomis gibbosus, yellow perch Perca flavescens and rock bass Ambloplites rupestris all consumed zebra mussels at varying frequencies and amounts. Aplodinotus grunniens and L. gibbosus chewed clumps of zebra mussels, expelling shells, whereas P. flavescens and A. rupestris swallowed small individuals whole. Lepomis gibbosus consumed zebra mussels at the highest frequency (65-89% of prey consumed) and zebra mussels comprised a large part of this fish's diet (up to 40% by dry mass). Zebra mussels were also an important component of the diet of A. grunniens (up to 59% of the diet by dry mass, 40-63% frequency of consumption). The percentage of the diet comprising zebra mussels in P. flavescens and A. rupestris varied significantly from year to year but never exceeded 10%. Because A. grunniens and L. gibbosus crushed zebra mussels, the nutritional return from consuming zebra mussels would be similar to other prey; for P. flavescens and A. rupestris zebra mussels were only partially digested and the nutritional return would probably be low. As predation on zebra mussels is widespread and significant, it is possible that fish predators could contribute to regulating the population of zebra mussels in Lake Champlain.

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CAPUZZO, J . M., and B. A. LANCASTER. 1979. Larval development in the American lobster: changes in metabolic activity and the O:N ratio. Can. J. Zool. 57: 184.5-1848. The rates of oxygen consumption under conditions of feeding and starvation and the rates of ammonia excretion after feeding increased with each larval stage of the American lobster (Homrrrus rrmeric,trnus Milne Edwards) and decreased with the first postlarval stage. There was no significant difference in the 0 : N ratio of the first three larval stages (-26.5), but a significant reduction ( P i 0.01) was measured among stages IV and V. It appears that, whereas protein catabolism may be the principal source of energy. some of the energy yield during larval development is from lipid or carbohydrate catabolism; the use of the latter substrates is diminished in the last larval and first postlarval stages. CAPUZZO, J . M., et B. A . LANCASTER. 1979. Larval development in the American lobster: changes in metabolic activity and the O:N ratio. Can. J. Zool. 57: 1845-1848. Le taux de consommation d'oxygene chez des animaux nourris et des animaux prives de nourriture et le taux d'excretion d'ammoniaque apres alimentation augmentent h chaque changement de stade larvaire chez le homard (Homrrrus nmerictrnus Milne Edwards) et diminuent au premier stade post-larvaire. I1 n'y a pas de difference significative du rapport O:N chez les trois premiers stades larvaires (-26.5), mais il se produit une diminution appreciable (P < 0.01) de ce rapport entre les stades IV et V. I1 semble que, bien que le catabolisme des proteines soit la principale source d'energie. une partie de I'energie liberee durant le developpement vienne du catabolisme des lipides ou des hydrates de carbone; I'utilisation de ces substrats diminue durant le dernier stade larvaire et le premier stade post-larvaire.[Traduit par le journal]