Scanning electron microscopy of antennal sensilla of the eight Anopheles species of the Hyrcanus Group (Diptera: Culicidae) in Thailand

Abstract

Antennal sensilla were first investigated in the eight medically and veterinary important Anopheles mosquito species (Anopheles argyropus, Anopheles crawfordi, Anopheles nigerrimus, Anopheles nitidus, Anopheles paraliae (= Anopheles lesteri), Anopheles peditaeniatus, Anopheles pursati, and Anopheles sinensis) of the Hyrcanus Group in Thailand, using scanning electron microscopy (SEM). Four types of sensilla, including sensilla chaetica (large and small), sensilla trichodea (sharp- and blunt-tipped), sensilla basiconica or grooved pegs (types I, II, and III), and sensilla coeloconica (large and small), were observed on the female antennae of the eight species. The greatest number of sensilla found along the flagellum of all the Anopheles species consisted of sensilla trichodea. Grooved pegs type II were not found on the antennae of An. peditaeniatus. Interestingly, clusters of 10-15 grooved pegs type III, with blunt-tipped and unevenly grooved-lengthwise sensilla, and a sunken group of 7-12 grooved pegs type III, with slightly curved and point-tipped sensilla, were found distally on flagellomeres 3-7 of An. argyropus and An. peditaeniatus, respectively. In addition, the key for species identification, based on fine structure and morphometrics of antennal sensilla among the eight species, was constructed and differentiated successfully. However, in order to focus intensively on the exact function of these sensilla, further electrophysiological study is needed in understanding their significant role in mosquito behavior, especially when these insects seek hosts for transmitting pathogens to humans.

An effective method for the identification and separation of Anopheles minimus, the primary malaria vector in Thailand, and its sister species Anopheles harrisoni, with a comparison of their mating behaviors

“…The same morphological types of sensilla were recognized by Pitts and Zwiebel [ 36 ] and Hempolchom et al [ 30 ] in their studies of Anopheles mosquitoes, and by Hill et al [ 35 ] in their study of Culex quinquefasciatus . Hempolchom et al [ 30 ] constructed a key based on differences in antennal sensilla to reliably distinguish eight species of the An. hyrcanus group in Thailand.…”

“…Following dehydration, they were dried in a critical point dryer. The antennae were carefully dissected from the head capsule under a stereomicroscope, as described by Hempolchom et al [ 30 ]. Antennae were mounted on aluminum stubs with double-sided carbon adhesive tape and sputter-coated with gold.…”

“…Researchers have attempted to find effective methods for the identification of Anopheles vectors based on morphological attributes, e.g. light microscopy of antennal sensilla [ 26 ] and scanning electron microscopy (SEM) of eggs and antennal sensilla [ 27 – 30 ]. However, no studies of the antennal sensilla of members of the Minimus Complex have been conducted.…”

Ultrastructural characterization of sensilla and microtrichia on the antenna of female Haematopota pandazisi (Diptera: Tabanidae)

“…The distribution of these sensilla in H. pandazisi is similar to that reported for A. fulvus (Faucheux 1981) and H. pluvialis (Elizarov and Chaika 1977). Two types of coeloconic sensilla have been described in other haematophagous Diptera belonging to the subfamily Anophelinae (Diptera: Culicidae) (Boo 1980;Pitts and Zwiebel 2006;Hempolchom et al 2017;Taai et al 2017), in Lutzomyia longipalpis (Lutz and Neiva) (Diptera: Psychodidae) (Fernandes et al 2008), and in H. irritans irritans (White and Bay 1980). Coeloconic sensilla bearing a single peg without longitudinal grooves have also been described in Anopheles maculipennis Meigen (Ismail 1964) and Anopheles stephensi Liston (Diptera: Culicidae) (Boo and McIver 1975;Boo 1980).…”

Morphological Aspects of Antennal Sensilla of theRhodnius brethesiMatta, 1919 (Hemiptera: Reduviidae) from the Negro River, Amazon Region of Brazil

“…In Triatominae, certain sensilla (e.g., trichobothria) may have taxonomic value in Triatomine [4] whereas sensilla reflect selective pressure on insect habitat and hosts. As antennae are the main environmental sensors, the host species and habitat specialization of each species may be reflected by differences in their sensory characteristics, as suggested by mosquitoes [5,6], beetles [7], and hymenopterans [8].…”