Abstract:

【Objective】This study aimed to identify the types, distribution, quantity, and sexual dimorphism of antennal sensilla in Xanthogaleruca aenescens through ultrastructural observation. The findings provide a basis for understanding the genetic evolution, morphological classification, and the role of olfactory sensilla in host volatile detection in leaf beetles.【Method】The antennae of adult female and male X. aenescens were cleaned, air-dried, and gold-coated for scanning electron microscopy (SEM). SEM was used to observe and photograph the morphological characteristics of the antennae and sensilla of both sexes, as well as to identify the types of sensilla present. Independent sample t-tests were conducted to compare differences in antennal length, sensilla length, base diameter, and the number of sensilla between the sexes, and the distribution of sensilla across the antennae was also examined.【Result】The antennae of X. aenescens were linear and consist of the scape, pedicel, and nine flagellar subsegments. The average length of male antennae was (4 558.01 ± 104.15) μm, while that of females was (4 488.75 ± 224.33) μm. Males have slightly longer antennae than females, although this difference was not statistically significant. Both males and females possessed eight types of antennal sensilla: sensilla trichodea (St), sensilla chaetica (Sc), sensilla basiconica (Sb), sensilla styloconica (Sst), Böhm bristles (Bb), sensilla gemmiformium (Sg), sensilla coeloconica (Sco), and sensilla auricillica (Sau). St and Sb each have four subtypes, Sc has two subtypes, and Sst has three subtypes. The female antennal flagellum has Sst 2, while the male flagellum contains Sst 3. The most abundant sensilla are St, followed by Sb, while Sco is the least common. St 4, Sb 1, Sb 3, and Sau exhibit micropores on their surfaces, indicating their role as olfactory sensilla. The total number of antennal sensilla in females was significantly greater than in males (P < 0.01). Specifically, the numbers of St 2, Sb 2, and Sst 1 were significantly higher in females (P < 0.05). St 4 and Sb 3 is significantly higher in females than in males (P < 0.01), while Sau was significantly fewer in females compared to males (P < 0.01). No significant differences were observed in the number of other sensilla. In both sexes, the tips of antennal subsegments F2 to F8 had inwardly concave areas with a high density of sensilla, and a similar concave area was present at the middle of the terminal segment F9. The density and number of sensilla increased from the base to the tip of the antenna. Additionally, the ventral surface of the male antennal flagellum (F1 to F8) exhibited a more densely packed area of epidermal depressions, a feature absent in females.【Conclusion】Both female and male X. aenescens have the same types of antennal sensilla, but there are clear sexual dimorphisms in sensilla subtypes, quantity, and distribution. Different subtypes of Sst were observed in males and females, with variations in the size of sensilla between the sexes. The total number of sensilla in males was significantly lower than in females. The specific roles of these sensilla in environmental perception, host detection, and mating behaviors should be further explored using transmission electron microscopy, electrophysiology, and other advanced techniques.

Key words: Xanthogaleruca aenescens, antennal sensilla, scanning electron microscopy, sex dimorphism, antennal morphology, ultrastructure