LAYBOURN-PARRY, J., ABDU LEAHI, B. A., and TINSON, S. V. Temperature-dependent energy partitioning in the benthic copepods Acanthocyclops viridis and Macrocyclops albidus. Can. J . Zool. 66: 270k -27 14.Energy acquisition and partitioning by the benthic copepods Acanthocyclops viridis (Jurine) and Macrocyclops abbidus (Jurine) from Esthwaite Water in the English Lake District were investigated at a range of temperatures within the normal environmental range (5 -2Q°C), in animals fed an excess of the ciliated protozoan Paramecium caudatum. Feeding rate increased with elevated temperature, while longevity, development time, adult size, clutch size, and interelutch period decreased. Temperature had a marked effect on the pattern of energy partitioning into reproduction: increasing temperature moved the balance towards reproduction. The ecological implications of temperature-induced changes on the energetics of these copepods is discussed. LAYBOURN-PARRY, J . , ABDU EEAHI, B. A., et TINSON, S. V. Temperature-dependent energy partitioning in the benthic copepads Acanthocyclops viridis and Macrocyclops albidus. Can. J. Zool. 66 : 2709 -27 14. h s gains CnergCtiques et le partitionnement de 1'Cnergie ont Ct C 6tudiCs 2t des tempCratures Cgales aux tempkratures du milieu (5 -2Q°C) c h a des co#podes benthiques Acanthocyclops viridis (Jurine) et Macrocyclops albidus (Jurine) pmvenant de Esthwaite Water, dms la n5gion des lacs en Angletern, et gardCs 2t un n5gime constituC de protozoaires ciliCs Paramecium cauQatum en quantit6s surabondantes. Les taux d'alimentation augmentaient en fonction directe de la tempkrature, alors que la longevite, la dude du developpement, la taille h l'ige adulte, le nombre d'oeufs et la @node entre les pontes diminuaient. ka tem#rature avait un effet marque sur le gartitionnement de 1'Cnergie et une tern#rature plus Clevk r$sultait en une canalisation plus grande de 1'Cnergie vers la reproduction. Les consCquences kologiques des changements de temp6rature sur les budgets CnergCtiques de ces co#podes font l'objet d'une discussion. [Traduit par la revue]

The response of four benthic cyclopoid copepods, Acanthocyclops viridis (Megacyclops viridis) (Jurine, 1820), Macrocyclops albidus (Jurine), Eucyclops agilis (Koch, Sars) (Eucyclops serrulatus) (Fischer, 185 1) and Paracyclopsfirnbriatus (Fischer), to hypoxia and anoxia was investigated. All of these species died within six hours when confronted by totally anoxic conditions, but all survived four days at oxygen saturation levels as low as 25%. Males succumbed to the effects of anoxia more rapidly than the larger females of each species, and larger species survived for shorter periods than smaller species. In artificially stratified columns, where the lower layer was anoxic, all four species displayed an upward migratory response towards oxygenated conditions. Where the artificial hypolimnion was hypoxic, however, the migratory response was not observed. The results suggest that some benthic copepods cope with seasonal anoxia in eutrophic stratified lakes by migration rather than the various physiological adaptations shown by planktonic and semi-planktonic species.

The spatial and temporal distribution of the benthic cyclopoid copepods, Acanthocyclops viridis, Acanthocyclops bicuspidatus, Eucyclops agilis, Paracyclops fimbriatus and Macrocyclops albidus in a small eutrophic lake Esthwaite Water, Cumbria was investigated in 1982 and 1983. The behavioural and physiological mechanisms by which these organisms cope with the conditions of hypoxia and anoxia prevalent during seasonal stratification of the lake waters was considered. During stratification all of these species, with the exception of resting stage A. bicuspidatus, disappeared from the profundal zone and were limited to the shallower margins of the lake. None of these copepod species entered the plankton and established planktonic populations, none appeared capable of sustained anaerobic respiration, although all can withstand some degree of hypoxia, and only A. bicuspidatus appeared capable of entering resting stages. The data suggest that in eutrophic lakes species normally found in the profundus deal with anoxia by lateral migration to shallow waters where oxygen is available.

The rate of oxygen consumption in all developmental stages of two benthic cyclopoid copepod species, Acanthocyclops viridis (Jurine) and Eucyclops agilis (Koch, Sars) was investigated at temperatures between 5° C-20° C, which are reflective of the environmental temperature range of the benthic zone in Esthwaite Water, Cumbria, from which the organisms were derived. The larger species, A. viridis was found to have a temperature insensitive metabolism, whereas E. agilis showed a marked temperature response in respiratory function. Gravid and non-gravid females had similar rates of respiration except at 15° C-20° C in E. agilis. Males exhibited much lower respiration rates than females, but higher weight specific respiration rates; these differences were largely attributable to size differentials between the sexes. Estimates of swimming activity were made and these were related to the patterns of respiratory function observed.