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Disease transmission by insect vectors will depend on integrated physiological responses to interacting environmental variables. We explored how interactions between temperature and sucrose concentration affected immunity and fecundity, two variables that contribute to vectorial capacity, in Culex pipiens Linnaeus, 1758 mosquitoes. We provided female C. pipiens with either 2% or 20% sucrose and exposed them to low (22 [degrees]C), moderate (25 [degrees]C), or high (30 [degrees]C) temperatures for 8 days. We then measured the strength of the melanization response in one subpopulation of females and the number of eggs laid as a measure of fecundity in another subpopulation. Temperature interacted with diet to weaken immunity under 2% sucrose at 22 and 25 [degrees]C. This effect disappeared at 30 [degrees]C, suggesting that high temperatures allowed mosquitoes to compensate for the effects of decreased sucrose. Conversely, increasing temperature increased egg production on a diet of 20% sucrose, but heat exposure on a diet of 2% sucrose decreased fecundity. Overall, we suggest that heat exposure requires investment in thermal protection, which may prompt reconfiguration of the immune system and (or) decreased investment in reproduction. Thus, our understanding of the effects of climate change rest on which physiological system we measure and under which combinations of stressors. Key words: vector, insect, multiple stressors, heat, Culex pipiens, mosquitoes, diet. La transmission de maladies par des insectes vecteurs dépend des réactions physiologiques intégrées à des variables environnementales qui interagissent entre elles. Nous avons examiné l'incidence des interactions entre la température et la concentration de sucrose sur l'immunité et la fécondité, deux variables qui jouent un rôle dans la capacité vectorielle, chez le moustique domestique, Culex pipiens Linnaeus, 1758. Nous avons donné à des C. pipiens femelles des solutions de 2 % et 20 % de sucrose et les avons exposées à des températures faible (22 [degrees]C), modérée (25 [degrees]C) ou élevée (30 [degrees]C) pendant 8 jours. Nous avons ensuite mesurélaforcedelaréactiondemélanisation dans une sous-populationdefemellesetlenombre d'oeufs pondus, comme mesure de la fécondité, dans une autre sous-population. L'interaction de la température avec l'alimentation se traduit par une baisse de l'immunité pour une concentration de sucrose de 2 % à 22 et 25 [degrees]C. Cet effet disparaît à 30 [degrees]C, donnant à penser que des températures élevées permettent aux moustiques de pallier les effets d'une faible concentration de sucrose. À l'inverse, une augmentation de la température accroît la production d'oeufs à une concentration de 20 % de sucrose, mais l'exposition à la chaleur combinée à une concentration de sucrose de 2 % réduit la fécondité. Globalement, nous proposons que l'exposition à la chaleur nécessite un investissement dans la protection thermique, qui pourrait entraîner une reconfiguration du système immunitaire ou réduire l'investissement dans la reproduction. Ainsi, la compréhension des effets des changements climatiques dépend du système physiologique mesuré et de la combinaison de facteurs de stress examinée. [Traduit par la Rédaction] Mots-clés : vecteur, insecte, facteurs de stress multiples, chaleur, Culex pipiens, moustiques domestiques, régime alimentaire., Introduction The incidence and severity of disease is changing as the climate changes, largely due to alterations in the physiology of both hosts and parasites under new environmental conditions (Harvell [...]

Sexual reproduction of apicomplexan parasites in haematophagous arthropods requires that intracellular sexual stages of these protozoa escape vertebrate erythrocytes in the blood meal. Although cues that signal sexual stages of the human malaria parasite (Plasmodium falciparum Welch, 1897) to emerge from erythrocytes are well documented, such signals are poorly known for other blood-dwelling Apicomplexa. The objective of this comparative study was to investigate conditions required to induce in vitro emergence of sexual stages of Hepatozoon clamatae (Stebbins, 1905) from frog erythrocytes. Blood was drawn from Green Frogs (Rana clamitans Latreille in Sonnini de Manoncourt and Latreille, 1801 = Lithobates clamitans clamitans (Latreille in Sonnini de Manoncourt and Latreille, 1801)) infected with H. clamatae and treated with solutions of various concentrations of saline, pH, and xanthurenic acid at different temperatures. Hypertonic saline solutions of 200 and 222 mmol/L at pH 7.4 and 7.7 elicited emergence of nearly 100% of gamonts from frog erythrocytes, but at pH 8.0 resulted in decreased emergence. Solutions containing 1, 10, and 100 [xmol/L xanthurenic acid increased gamont emergence at saline concentrations of 156, 178, and 244 mmol/L, but decreased emergence at 200 and 222 mmol/L. Gamont emergence increased as incubation temperatures increased from 18 to 26 °C. These results suggest that conditions necessary for emergence of sexual stages of bloodstream Apicomplexa from erythrocytes vary among genera. Key words: Hepatozoon clamatae, Green Frog, Rana clamitans, gamont, mosquito, Culex territans, xanthurenic acid, malaria parasites, Plasmodium species, blood. La reproduction sexuee de parasites apicomplexes dans des arthropodes hematophages necessite que les stades sexues intracellulaires de ces protozoaires s'echappent des erythrocytes vertebres dans le repas de sang. Bien que des signaux qui indiquent aux stades sexues du parasite du paludisme humain (Plasmodium falciparum Welch, 1897) d'emerger des erythrocytes soient bien documentes, ce type de signaux demeure meconnu chez d'autres apicomplexes du sang. L'objectif de la presente etude comparative etait d'examiner les conditions requises pour provoquer l'emergence in vitro de stades sexues d'Hepatozoon clamatae (Stebbins, 1905) d'erythrocytes de grenouille. Du sang a ete preleve de grenouilles vertes (Rana clamitans Latreille in Sonnini de Manoncourt and Latreille, 1801 = Lithobates clamitans clamitans (Latreille in Sonnini de Manoncourt and Latreille, 1801)) infectees au H. clamatae puis traite avec des solutions de differentes concentrations de sel et d'acide xanthurenique a differents pH et a differentes temperatures. Des solutions salines hypertoniques de 200 et 222 mmol/L a des pH de 7,4 et 7,7 ont provoque l'emergence de pres de 100 % des gamontes des erythrocytes de grenouille, mais un pH de 8,0 s'est traduit pas une reduction du taux d'emergence. Des solutions contenant 1, 10 et 100 [xmol/L d'acide xanthurenique ont entrame une emergence accrue de gamontes pour des concentrations salines de 156, 178 et 244 mmol/L, mais une emergence reduite a 200 et 222 mmol/L. L'emergence de gamontes augmentait parallelement a l'augmentation de la temperature d'incubation de 18 a 26 °C. Ces resultats suggerent que les conditions necessaires a l'emergence de stades sexues d'apicomplexes du sang en dehors d'erythrocytes varient selon le genre. [Traduit par la Redaction] Mots-cles: Hepatozoon clamatae, grenouille verte, Rana clamitans, gamonte, moustique, Culex territans, acide xanthurenique, parasites du paludisme, espece de Plasmodium, sang., Introduction The phylum Apicomplexa contains species of many genera that parasitise the blood cells of vertebrates and use blood-feeding arthropods or annelids as definitive hosts. For all blood-dwelling Apicomplexa, with [...]

(Received 9 August 1997; accepted in revised form 23 December 1997) 1 Department of Fisheries and Oceans, Institute of Ocean Sciences, P.O. Box 6000, Sidney, British Columbia V8L 4B2, Canada; [...]

This study focuses on the effect of various processing and cooling conditions upon the subsequent melting and solidification behavior of blends of poly(butylene terephthalate) (PBT) and high density polyethylene (HDPE). Differential scanning calorimetry (DSC) measurements have shown that the crystallization of reprocessed PBT is different from the crystallization behavior of virgin samples. Two melting endotherms for PBT were observed for reprocessed PBT and for PBT-PE blends. The nature of each PBT peak is discussed in relation to processing history, solidification conditions, and composition. The presence of two crystallization peaks for the PE component in blends of PE and PBT are thought to be associated with the restriction of molecular motion of PE in the presence of the second component. The relative magnitudes of the two exotherms of PE vary with composition and cooling rate during solidification.

D.J. ST. AUBIN [1] S. DEGUISE [2] P.R. RICHARD [3] T.G. SMITH [4] J.R. GERACI [5] (Received 31 January 2000; accepted in revised form 10 August 2000) ABSTRACT. The capture [...]

P.R. RICHARD [1] M.P. HEIDE-JORGENSEN [2] J.R. ORR [1] R. DIETZ [3] T.G. SMITH [4] (Received 18 November 1999; accepted in revised form 25 January 2001) ABSTRACT. Twenty-one adult belugas [...]