Effects of variation in quality of leaf detritus on growth of the eastern tree-hole mosquito, Aedes triseriatus (Diptera: Culicidae)

Growth of larvae of the eastern tree-hole mosquito, Aedes triseriatus (Say), measured as survival to adulthood, development time, and body mass at adult emergence, was significantly better when larvae were provided with fresh rather than senescent beech leaves as food substrate. Leaf type affected larval growth performance independently of ration of leaf available per larva when the ration level was high and larvae were not densely crowded, but leaf type and ration level had interactive effects on larval growth performance when ration was more limiting and larvae denser. Fresh leaves contained about twice as much nitrogen, had a lower carbon:nitrogen ratio, leached more mass into water, and contained significantly more soluble protein and carbohydrate than did senescent leaves. Thus, the observed growth responses could be explained on the basis of variation in nutrient content of, and greater leaching from, the fresh leaves. Larval growth was also significantly better on intact senescent beech leaves than on leaves that had been leached to remove soluble protein and carbohydrate; it was also significantly better on leaves whose surfaces had flourishing bacterial growth than on leaves with disinfected surfaces. Growth of female larvae fit well a pupation window model where larvae attained a minimum mass to emergence past a minimum development time across a range of leaf substrates varying in quality and quantity. RCsumC : La croissance des larves du moustique Aedes triseriatus (Say), une donnke tenant compte de la survie jusqu'a l 'ige adulte, de la durke du dkveloppement et de la masse au moment de l'kmergence, est significativement meilleure lorsque les larves sont nourries de feuilles fraiches que lorsqu'elles sont klevkes sur des feuilles sknescentes de hCtre. Le type de feuille affecte la performance de la croissance indkpendamment de la quantitk disponible par larve lorsque la quantitk est klevke et la densitk des larves, faible, mais le type de feuille et la quantitk ont des effets interactifs sur la performance de la croissance lorsque la quantitk est plus limitke et la densitk des larves, plus klevke. Les feuilles fraiches contiennent environ deux fois plus d'azote, le rapport carbone : azote y est plus faible, elles lessivent une plus grande partie de leur masse dans l'eau et contiennent significativement plus de protkines et d'hydrates de carbone solubles que les feuilles sknescentes. Les rksultats obtenus peuvent donc s'expliquer par les diffkrences dans le contenu en klkments nutritifs et le lessivage plus importants des feuilles fraiches. La croissance larvaire est aussi significativement plus rapide sur les feuilles sknescentes entikres que sur les feuilles qui ont kt6 lessivkes de leurs protkines et hydrates de carbone solubles; elle est aussi plus rapide sur les feuilles dont la surface est couverte de colonies bactkriennes que sur les feuilles a surface dksinfectke. La croissance des larves femelles correspond bien a un modkle de fenCtre de nymphose ou les larves atteignent une masse minimale a l'kmergence aprks un dkveloppement de durke minimale, sur des substrats de feuilles de qualitk et de quantitk varikes. [Traduit par la Rkdaction] Introduction brates consume leaf detritus directly by shredding coarse particulate detritus or by gathering finer detritus, but for macroinvertebrates inhabiting freshwater ecosystems these guilds, the efficiency of conversion of leaf material into utilize allochthonous leaf detritus as food. Some inverteinvenebrate tissue is usually low (Berrie 1976; Slansky and I Scriber 1985). Other invertebrates, including mosquito larReceived August 26, 1996. Accepted November 18, 1996. E.D. Walker1 and R. W. Merritt. Department of Entomology, Michigan State University, East Lansing, MI 48824, U. S. A. M.G. Kaufman. Kellogg Biological Station, Michigan State University, Hickory Corners, MI 49060, U . S . A. M.P. Ayres. Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, U.S.A. M.H. Riedel. Justus-Liebig University of Giessen, College of Veterinary Medicine, FrankfurterstraRe 92-107, 35398 Giessen, Germany. ' Author to whom all correspondence should be addressed (e-mail: walker@pilotw .msu .edu). vae, exploit leaf detritus by filtering, scraping, or browsing microorganisms in the biofilm on the leaf surface (Cummins and Klug 1979; Fish and Carpenter 1982; Walker and Merritt 1991; Merritt et al. 1992). Invertebrate growth on leaf detritus varies with feeding mode, quantity of leaf detritus, chemical composition of leaf detritus, decomposition rate of leaves, and microbial conditioning of the leaf material (Kaushik and Hynes 197 1; Berrie 1976; Anderson and Sedell 1979; Cummins and Klug 1979; Merritt et al. 1984). Water-filled containers, both natural ("phytotelmata") and anthropogenic (e.g., discarded tires), are common habitats of mosquitoes and other insects in temperate and tropical areas Can. J. Zool. 75: 706-718 (1997) O 1997 NRC Canada