Drosophila melanogaster, also known as fruit flies, are a common species of detritivore. An interesting study on cannibalism was conducted in Drosophila melanogaster larvae under laboratory conditions (Vijendravarma et al., 2013).
The experimental set up was as follow: sepia mutants were used as “prey” and were mixed with wild type larvae inside a vial without food. From this set up the rate of cannibalism was recorded (Vijendravarma et al., 2013). Results from this study by Vijendravarma et al. (2013) obtained several hypotheses:
(1) Nutritional stress drives the evolution of cannibalism
(2) Survival in food-deprived environments is dependent on cannibalism: larvae were observed to complete development solely by cannibalizing on other larvae.
(3) Cannibalism drove the evolution of mouthpart of larvae: higher cannibalism rate, showed higher number of teeth on mouth hooks.
Although the overall observations indicate that nutritional stress is the main factor that induces the cannibalistic behavior in these larvae, spontaneous cannibalism was also observed in overcrowded vials. In addition, assays conducted showed that even though larvae are cultured in food-abundant environment, they are still attracted to injured conspecifics and will cannibalize other wild type larvae (Vijendravarma et al., 2013).
Cannibalism is also common in several other Drosophila species whereby toxic microorganisms contaminated their food sources and cannibalizing their own conspecific would confer fitness to an individual, resulting in complete development. Conspecific cannibalism is also said to provide scarce nutrients in fruits like sodium, to the cannibal (Vijendravarma et al., 2013).
The experimental set up was as follow: sepia mutants were used as “prey” and were mixed with wild type larvae inside a vial without food. From this set up the rate of cannibalism was recorded (Vijendravarma et al., 2013). Results from this study by Vijendravarma et al. (2013) obtained several hypotheses:
(1) Nutritional stress drives the evolution of cannibalism
(2) Survival in food-deprived environments is dependent on cannibalism: larvae were observed to complete development solely by cannibalizing on other larvae.
(3) Cannibalism drove the evolution of mouthpart of larvae: higher cannibalism rate, showed higher number of teeth on mouth hooks.
Although the overall observations indicate that nutritional stress is the main factor that induces the cannibalistic behavior in these larvae, spontaneous cannibalism was also observed in overcrowded vials. In addition, assays conducted showed that even though larvae are cultured in food-abundant environment, they are still attracted to injured conspecifics and will cannibalize other wild type larvae (Vijendravarma et al., 2013).
Cannibalism is also common in several other Drosophila species whereby toxic microorganisms contaminated their food sources and cannibalizing their own conspecific would confer fitness to an individual, resulting in complete development. Conspecific cannibalism is also said to provide scarce nutrients in fruits like sodium, to the cannibal (Vijendravarma et al., 2013).
Image credits (left to right):
http://www.themunicheye.com/news/Why-do-some-animals-turn-cannibalistic%3F-2721; http://www.unil.ch/dee/page55300_en.html; http://www.unil.ch/dee/page55300_en.html