Pulsed Light Stimulation Increases Boundary Preference and Periodicity of Episodic Motor Activity in Drosophila melanogaster

Mating experience modifies locomotor performance and promotes episodic motor activity in Drosophila melanogaster

Sexual behavior is a routine among animal species. Sexual experience has several behavioral consequences in insects, but its physiological basis is less well-understood. The episodic motor activity with a periodicity around 19 s was unintentionally observed in the wildtype Canton-S flies and was greatly reduced in the white-eyed mutant w¹¹¹⁸ flies. Episodic motor activity co-exists with several consistent locomotor performances in Canton-S flies whereas reduced episodic motor activity is accompanied by neural or behavioral abnormalities in w¹¹¹⁸ flies. The improvements of both episodic motor activity and locomotor performance are co-inducible by a pulsed light illumination in w¹¹¹⁸. Here we show that mating experience of w¹¹¹⁸ males promoted fast and consistent locomotor activities and increased the power of episodic motor activities. Compared with virgin males, mated ones showed significant increases of boundary preference, travel distance over 60 s, and increased path increments per 0.2 s. In contrast, mated males of Canton-S showed decreased boundary preference, increased travel distance over 60 s, and increased path increments per 0.2 s. Additionally, mated males of w¹¹¹⁸ displayed increased power amplitude of periodic motor activities at 0.03-0.1 Hz. These data indicated that mating experience promoted fast and consistent locomotion and improved episodic motor activities in w¹¹¹⁸ male flies.

Frequency-specific modification of locomotor components by the white gene in Drosophila melanogaster adult flies

The classic eye-color gene white (w) in Drosophila melanogaster (fruitfly) has unexpected behavioral consequences. How w affects locomotion of adult flies is largely unknown. Here, we show that a mutant allele (w¹¹¹⁸ ) selectively increases locomotor components at relatively high frequencies (> 0.1 Hz). The w¹¹¹⁸ flies had reduced transcripts of w⁺ from the 5' end of the gene. Male flies of w¹¹¹⁸ walked continuously in circular arenas while the wildtype Canton-S walked intermittently. Through careful control of genetic and cytoplasmic backgrounds, we found that the w¹¹¹⁸ locus was associated with continuous walking. w¹¹¹⁸ -carrying male flies showed increased median values of path length per second (PPS) and 5-min path length compared with w⁺ -carrying males. Additionally, flies carrying 2-4 genomic copies of mini-white⁺ (mw⁺ ) in the w¹¹¹⁸ background showed suppressed median PPSs and decreased 5-min path length compared with controls, and the suppression was dependent on the copy number of mw⁺ . Analysis of the time-series (i.e., PPSs over time) by Fourier transform indicated that w¹¹¹⁸ was associated with increased locomotor components at relatively high frequencies (> 0.1 Hz). The addition of multiple genomic copies of mw⁺ (2-4 copies) suppressed the high-frequency components. Lastly, the downregulation of w⁺ in neurons but not glial cells resulted in increased high-frequency components. We concluded that mutation of w modified the locomotion in adult flies by selectively increasing high-frequency locomotor components.

Assessment of microalgae as a new feeding additive for fruit fly Drosophila melanogaster

Animal food wastes are a concern due to the large amounts of commercial food required for model animals during the biological and biomedical research. Searching for sustainable food alternatives with negligible physiological effects on animals is critical to solve or reduce this challenge. Microalgae have been demonstrated to be suitable for both human consumption and animal feed. In this study, the possibility of using Chlorella vulgaris and Senedesmus obliquus as a feed replacement to Drosophila melanogaster, one of the fly models commonly used in biomedical studies, was investigated. Characteristics including the fly locomotor activity, motor pattern, feeding behavior, lifespan and body weight were assessed. Results showed that compared to control, the flies fed on 80% microalga (80-flies) in the total weight (w/w) had the double increased apparent step size, while both 60-flies and 80-flies exhibited longer travel distances (60%: 27.77 ± 1.99 cm; 80%: 31.50 ± 3.70 cm) most likely due to the starvation and varied serotonin levels in flies fed on high percentages microalgae. Subsequently, 40-flies exhibited less optimal growth performance with decreased body weights (0.51 ± 0.006 mg vs 0.60 ± 0.005 mg for control) and shorter mean lifespan (36 days vs 55.8 days for control. However, 20-flies showed no statistical differences in all parameters tested with respect to control flies, indicating that 20% microalgae treatment did not greatly change the primary food component such as carbohydrate which might play a critical role in fly performance. Therefore, the inclusion of 20% microalgae could be an alternative to fly standard food without compromising fly physiological performance.

Different age-dependent performance in Drosophila wild-type Canton-S and the white mutant w1118 flies

Aging has significant effects on the locomotor performance of insects including Drosophila. Using a protocol for the high-throughput analysis of fly locomotion in a circular arena, we examined age-dependent behavioral characteristics in adult flies. There are widely used wild-type and genetically engineered background lines including the Canton-S strain and the w1118 strain, which has a null mutation of the white gene. Under standard rearing conditions, we found similar survival and median lifespans in Canton-S (50days) and w1118 (54days) strains, however, w1118 flies maintained stable body mass for up to 43days, whereas Canton-S flies gained body mass at young age, followed by a gradual decline. We also tested the behavioral performance of young and old flies. Compared with young w1118 flies (5-10days), old w1118 flies (40-45days) had an increased boundary preference during locomotion in small circular arenas, and increased speed of locomotor recovery from anoxia. Old Canton-S files, however, exhibited unchanged boundary preference and reduced recovery speed from anoxia relative to young flies. In addition, old w1118 flies showed decreased path length per minute and reduced 0.2s path increment compared with young flies, whereas old Canton-S flies displayed the same path length per minute and the same 0.2s path increment compared with young flies. We conclude that age-dependent behavioral and physiological changes differ between Canton-S and w1118 flies. These results illustrate that phenotypic differences between strains can change qualitatively, as well as quantitatively, as the animals age.