Volatile Compounds from Eggs of Three Fruit Fly Drive Aggregation and Oviposition

TL;DR

Three fruit fly species use egg volatiles to attract other females, leading to clustered egg-laying rather than avoiding competition.

Contribution

The study identifies species-specific volatile compounds from fruit fly eggs that drive aggregation and oviposition behavior.

Findings

B. dorsalis eggs produce the most unique volatile compounds and attract the most females.

Z. tau eggs show the least attraction and have the fewest unique volatiles.

Egg volatiles significantly influence interspecific oviposition behavior among the three species.

Abstract

Insect oviposition marks typically deter competitors via signaling compounds that structure resource utilization, yet certain Tephritidae exhibit reversed chemical communication. Females of Bactrocera dorsalis, Zeugodacus cucurbitae, and Zeugodacus tau are attracted to conspecific oviposition cues, resulting in aggregated egg-laying rather than resource partitioning. Using gas chromatography–mass spectrometry (GC–MS) to analyze volatiles from conspecific eggs, we identified species-specific attractive profiles. B. dorsalis females showed the strongest aggregation responses, correlating with distinct volatile signatures. These findings confirm that these species lack oviposition-deterring pheromones, instead utilizing attractive semiochemicals to facilitate aggregation.

Insects use oviposition secretions containing deterrent signals to regulate intra- and interspecific competition and structure resource partitioning; certain Tephritidae display a striking reversal of this strategy. Herein, we induced female aggregation and oviposition using eggs from the three fruit fly species (B. dorsalis, Z. cucurbitae, Z. tau) and characterized the eggs’ volatile profiles by GC–MS. Within 6 h, female attraction rates to egg stimuli varied significantly by species combination. B. dorsalis females were attracted to conspecific eggs at 39.33%, to Z. cucurbitae eggs at 28.67%, and to Z. tau eggs at 0%. Z. cucurbitae females showed attraction rates of 22.67% to B. dorsalis eggs, 13.00% to conspecific eggs, and 1.33% to Z. tau eggs. Z. tau females exhibited 27.67% attraction to B. dorsalis eggs, 13.67% to Z. cucurbitae eggs, and 18.33% to conspecific eggs. Oviposition assays confirmed strong interspecific effects, with B. dorsalis eggs stimulating the greatest egg-laying. GC–MS analysis revealed distinct volatile profiles, with B. dorsalis eggs producing the highest number of unique compounds (57), potentially explaining their strong behavioral effects. In total, 79 volatiles differed significantly between Z. cucurbitae and B. dorsalis eggs, 73 between Z. tau and B. dorsalis eggs, and 91 between Z. cucurbitae and Z. tau eggs. These findings reveal a behavioral hierarchy where B. dorsalis is the most responsive to egg volatiles, Z. cucurbitae is intermediate, and Z. tau is the least responsive, a ranking that correlates with significant differences in the eggs’ volatile compositions. This study directly links a behavioral status in interspecific oviposition to species-specific egg volatile profiles.

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