Morphology and distribution of antennal sensilla in the gall midge Gephyraulus lycantha (Diptera: Cecidomyiidae)

Morphological characterization of antennal sensilla in Toxorhynchites theobaldi, Toxorhynchites violaceus, and Lutzia bigoti adults: a comparative study using scanning electron microscopy

Some mosquitoes, including species of the genus Toxorhynchites, are known for actively preying on other mosquito larvae, making these predators valuable allies in the fight against vector-borne diseases. A comprehensive understanding of the anatomy and physiology of these potential biological control agents is helpful for the development of effective strategies for controlling vector populations. This includes the antennae, a crucial component in the search for hosts, mating, and selection of oviposition sites. This study utilized scanning electron microscopy to characterize the sensilla on the antennae of adult mosquitoes from two species that are exclusively phytophagous, including Toxorhynchites theobaldi and Toxorhynchites violaceus, as well as Lutzia bigoti, which females are allegedly hematophagous. The types of sensilla in each species were compared, and five basic types of antennal sensilla were identified: trichoid, chaetic, coeloconic, basiconic, and ampullacea. The analysis also found that they were morphologically similar across the three species, regardless of feeding habits or sex. The identification and characterization of basic types of antennal sensilla in T. theobaldi, T. violaceus, and L. bigoti suggest that these structures, which play a crucial role in the behavior and ecology, have common functions across different mosquito species, despite differences in feeding habits or sex.

Morphology and location of sensilla in the antennae and ovipositor of Sirex noctilio (Hymenoptera: Siricidae)

The woodwasp Sirex noctilio Fabricius is a major quarantine pest that was reported in China in 2013 and mostly damages Pinus sylvestris var. mongolica. Reverse chemical ecology, which uses chemical lures to catch or block insects from mating is the classic way to control forestry pests. This indicates that insect sensilla play a crucial role in detecting external chemical and physical stimuli. Nonetheless, the categorization and distribution of sensilla on the antennae and ovipositor of S. noctilio are insufficiently specific. In this paper, scanning electron microscopy (SEM) was used to observe the ultrastructure of the sensilla of S. noctilio on the antenna and ovipositor. It was found that the types and distribution of sensilla on the antennae of S. noctilio male and female are consistent, and six types of sensilla are found: sensilla trichodea (ST), sensilla chaetica (SC), Böhm bristles (BB), sensilla basiconica (SB), sensilla ampullacea (SA), and contact chemoreceptors (CC). Besides, there are five types of sensilla on the female ovipositor. In addition to ST, SC and BB, two more types of sensilla are also found: sensilla cavity (SCa) and sensilla coeloconica (SCo). Through identification of the morphology and distribution of the sensilla, the functions of different sensilla in the mating and host selection mechanisms of S. noctilio are proposed, thereby establishing a foundation for S. noctilio chemical communication research.

Comparative ultrastructure of the antennae and sensory hairs in six species of crayfish

Background

Antennae in crayfish are essential for gaining information about the local topography and localising food, chemicals, conspecifics or predator. There are still gaps in the research on the morphology of antennae in decapods compared to other arthropods.

Methodology

Biometrical and ultrastructural methods were applied using light and cryo-scanning electron microscopies to study the morphology of antennae in six different crayfish species, including marbled crayfish Procambarus virginalis, Mexican dwarf crayfish Cambarellus patzcuarensis, red swamp crayfish Procambarus clarkii, signal crayfish Pacifastacus leniusculus, common yabby Cherax destructor, and spiny-cheek crayfish Faxonius limosus to find their potential morphological differences.

Results

Significant differences in the antenna length, length and width of each segment to carapace length ratios, and the number of segments were found in the six crayfish species. The ultrastructure revealed differences in the distribution of sensory hairs on the antenna and the morphology of the antennal surface.

Conclusions

The different morphology of antennae might reflect adaptation to the conditions of their specific habitats. In addition, results showed that a combination of differences in the morphological features and biometrical measurements of antennae could be used for the distinguishment of different studied crayfish species.