Abstract
An aquatic plant,Elodea densa (Planchon)Caspary, and gravel filter combination was employed in a closed system to rear the planarian mosquito predator,Dugesia dorotocephala (Woodworth). The predator population increased 88 times in 95 days by fission. Filtration improved yields 270%. In unfiltered units the water fouled andDugesia reproduction ceased after 65 days. The reduction was probably caused by accumulating nitrogenous wastes: 0.22 vs 0.02 ppm nitrite-N, 2.2 vs 0.8 ppm ammonia-N, and 16 vs 3.3 ppm for nitrate-N in unfiltered and filtered replicates, respectively, The dissolved O2 decreased to 1.8 ppm in the unfiltered water, but remained supersaturated at 8.8 ppm with filtration through the activity of theElodea colony. The higher dissolved O2 permitted greater nitrite oxidation by bacteria inhabiting the filter bed. Planaria could be induced to rise to the water surface by halting filtration for 24 h, which facilitated harvesting. Prolonged storage of mature planarians in irrigation water at 10°C resulted in only a 10% mortality after 6 months, but caused a 2.5-fold decrease in body length.
Résumé
Une combinaison d'Elodea densa (Planchon)Caspary et d'un filtre à graviers a été employée dans un système fermé pour élever la planaire prédatrice de moustiques,Dugesia dorotocephala (Woodworth). La population du prédateur a augmenté de 88 fois en 95 jours par scissiparité. La filtration a amélioré la production de 270%. Dans les lots non filtrés, l'eau s'infectait et la reproduction deDugesia a cessé après 65 jours. La cause de la réduction était probablement l'accumulation de l'azote des déjections: 0,22 contre 0,02 ppm de nitrite, 2,2 contre 0,8 ppm d'ammoniaque et 16 contre 3,3 ppm de nitrate dans les variantes non filtrées et filtrées, respectivement. L'oxygène dissous a diminué jusqu'à 1,8 ppm dans l'eau non filtrée, mais est resté sursaturé à 8,8 ppm dans le cas de filtration, à cause de l'activité de la colonie d'Elodea. Une quantité plus importante d'oxygène dissous permettait une meilleure oxydation des nitrites par les bactéries du filtre. Les planaires pouvaient être amenées à la surface de l'eau en arrêtant la filtration pour 24 heures, ce qui facilitait la récolte. Le stockage prolongé des planaires mûres dans l'eau d'irrigation à 10°C a provoqué une mortalité seulement de 10% après 6 mois mais a causé une diminution de 2,5 fois de la longueur du corps.
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Research partially supported by funds from a special appropriation for mosquito research authorized by the California State Legislature during 1976.
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Legner, E.F., Tsai, S.C. Increasing fission rate of the planarian mosquito predator,Dugesia dorotocephala, through biological filtration. Entomophaga 23, 293–298 (1978). https://doi.org/10.1007/BF02373104
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DOI: https://doi.org/10.1007/BF02373104