Abstract
Drosophila melanogaster larvae excrete amylase and perform external digestion of their food. In this study, to investigate whether their external digestion ability varies in response to changes in the external environment, we measured the relative amount of amylase excreted by larvae using a new method: the iodine starch agar method (ISAM). Analysis using this method revealed that the amount of amylase excreted by larvae increased in accordance with the increase in the agar concentration. In addition, we investigated the effect on the larval growth rate of adding amylase to the diet. Pupation occurred 24 h later in food containing 1% amylase than in food containing no amylase. These results suggest that the larvae adjust their amylase excretion in response to changes in the external environment, and that its level has a marked influence on the larval growth rate.
Highlights
Humans digest food after putting it into their mouths
Consistent with previous reports, these results demonstrate that fruit fly larvae secrete amylase onto the food medium under our experimental conditions
To investigate whether larvae increase amylase secretion in response to an increase in food hardness, larvae were placed on blue-colored iodinated agar medium of different degrees of hardness
Summary
Bacteria and some animals such as Octopus vulgaris paralarvae, Pogonophora, and Drosophila melanogaster larvae perform digestion by excreting enzymes into the external environment (Ivanov, 1955; Gregg et al, 1990; Vicente et al, 2000; Bonner, 2001). D. melanogaster larvae facilitate external digestion by associating in clusters and producing more digestive enzymes. This phenomenon is called “social digestion” (Gregg et al, 1990). We predicted that larvae excrete digestive enzymes such as amylase, which physically soften the food and improve the efficiency of food ingestion. Food softening seems to help larvae to move around in the food
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