Entomophaga

, Volume 21, Issue 4, pp 415–423 | Cite as

Environmental stimulants to asexual reproduction in the planarian,Dugesia dorotocephala

  • E. F. Legner
  • T. C. Tsai
  • R. A. Medved
Article

Abstract

Studies of environmental factors that stimulate asexual reproduction in the planarian,Dugesia dorotocephala (Woodworth), feeding onCulex pipiens quinquefasciatusSay revealed that unchlorinated well and irrigation waters were superior to buffered aqueous media for fission. Constant darkness also was superior to constant light; although, a 12/12-hr photoperiod also allowed good asexual reproduction. Fluctuating dissolved oxygen levels between 3 and 8 ppm apparently stimulated fission. A coarse gravel substrate was superior to smooth plastic. Daily temperature increases of 0.8°C/day between 22.5° and 28.9°C also stimulated fission. Fission rates decreased with increased densities ofD. dorotocephala in unfiltered aquaria, contrary to earlier results obtained in filtered aquaria. The addition of the ostracods,Cypridopsis vidua (Müller) andPhysocypria pustulosaSharpe, to a diet of mosquito larvae increased fission. Brine shrimp (Artemia sp.) and red tubifex worms (Tubifex sp.) were not as suitable as mosquito larvae for food, apparently because the planaria had difficulty capturing these prey.D. dorotocephala was tolerant of salinities between 250–1,000 ppm, but feeding activity was impaired above and below this range. Mechanical sectioning of individuals was not a practical method for mass production; although if sectioning were coupled with media filtration, some reproductive acceleration might result.

Keywords

Asexual Reproduction Brine Shrimp Mosquito Larva Constant Light Dissolve Oxygen Level 

Résumé

Les études sur les facteurs de l'environnement qui stimulent la reproduction asexuée chez la planaire,Dugesia dorotocephala (Woodworth), se nourrissant deCulex pipiens quinquefasciatusSay ont mis en évidence que les puits d'eau ordinaires et les eaux d'irrigation sont supérieurs à d'autres milieux aqueux pour la division; et que le noir total est supérieur à la lumière totale bien qu'une photopériode de 12/12 soit aussi un optimum. Des niveaux variables d'oxygène dissous entre 3 et 8 ppm semblent stimuler la reproduction. Un substrat de gros gravier est supérieur à une surface de plastique lisse et des augmentations quotidiennes de température de 0,8°C/jour entre 22,5° et 28,9°C ont stimulé la partition. La fréquence de multiplication a été diminuée par l'augmentation de la densité enDugesia dans les aquariums non-filtrés, contrairement aux résultats antérieurs dans les aquariums filtrés. L'addition des ostracodes,Cypridopsis vidua (Müller) etPhysocypria pustulosaSharpe à un régime alimentaire à base de larves de moustiques a augmenté la reproduction. Les crevettes de saumure,Artemia sp., et les vers rougesTubifex sp., ne conviennent pas autant que les larves de moustiques comme aliment, à cause des difficultés, semble-t-il, de capture de ces proies.D. dorotocephala a supporté des salinités entre 250–1,000 ppm, mais l'activité alimentaire a été diminuée au-dessus et audessous de ces extrêmes. Le sectionnement mécanique des individus n'est pas une méthode pratique pour une production massive, bien que, associé à une filtration, il soit possible d'obtenir une accélération de la reproduction.

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Copyright information

© Le François 1976

Authors and Affiliations

  • E. F. Legner
    • 1
  • T. C. Tsai
    • 1
  • R. A. Medved
    • 1
  1. 1.Division of Biological ControlUniversity of CaliforniaRiversideUSA

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