Ultrastructure of antennal sensilla of Copidosomopsis nacoleiae (Eady) (Hymenoptera: Chalcidoidea: Encyrtidae), a parasitoid of Diaphania angustalis (Snellen) (Lepidoptera: Crambidae)

Abstract

The antennal sensilla of Copidosomopsis nacoleiae (Eady) (Hymenoptera: Chalcidoidea: Encyrtidae) were observed under scanning and transmission electron microscopy in this study. The antennae of C. nacoleiae are geniculate, and the flagellum is composed of five subsegments in males and six in females. Six types of sensilla were observed, including sensilla trichodea, sensilla chaetica, sensilla basiconic capitate pegs, sensilla placodea, sensilla basiconica, and Böhm's bristles. Sensilla trichodea were evenly distributed throughout the antennae. Sensilla chaetica, sensilla basiconic capitate pegs and sensilla placodea were found on the flagellomeres. Sensilla basiconica were only found on the club, and Böhm's bristles were found on the radicle and the pedicel. Sensilla trichodea, sensilla placodea, sensilla chaetica, and sensilla basiconic capitate pegs were found to be the most common sensilla of the parasitoids in the superfamily Chalcidoidea. The external and internal characteristics, types, number, distribution, and dimensions of these sensilla are described, and their possible functions are discussed in accordance with host‐detection behavior. Future studies on the host location mechanisms of C. nacoleiae will be based upon these observations.

Morphology and Distribution of Antennal Sensilla in an Egg Parasitoid Wasp,Anastatus disparis(Hymenoptera: Eupelmidae)

“…Like most Hymenopteran parasitoids, A. disparis has sexually monomorphic, geniculate antenna made up of four basic segments, the radicula, scape, pedicel, and flagellum. The radicula is the most proximal segment and joins the antenna to the head; the radiculae of both sexes were consistent in morphology with those of other parasitoid wasps ( Amornsak et al 1998 , Onagbola and Fadamiro 2008 , Meng et al 2012 , Roh et al 2019 , Wong et al 2021 , Zhang et al 2021 , Zhu et al 2021 ). The wasp radicula is generally considered a separate segment, as it is wholly separate from the scape and contains different types of sensilla ( Onagbola and Fadamiro 2008 , Roh et al 2019 , Wong et al 2021 , Zhang et al 2021 , Zhu et al 2021 ).…”

“…The radicula is the most proximal segment and joins the antenna to the head; the radiculae of both sexes were consistent in morphology with those of other parasitoid wasps ( Amornsak et al 1998 , Onagbola and Fadamiro 2008 , Meng et al 2012 , Roh et al 2019 , Wong et al 2021 , Zhang et al 2021 , Zhu et al 2021 ). The wasp radicula is generally considered a separate segment, as it is wholly separate from the scape and contains different types of sensilla ( Onagbola and Fadamiro 2008 , Roh et al 2019 , Wong et al 2021 , Zhang et al 2021 , Zhu et al 2021 ). Nonetheless, use of the term ‘“segment”’ is typically limited to structures with their own musculature, and additional research would be required to verify that the A. disparis radicula is indeed a separate segment ( Chapman 1998 ).…”

“…SBII were morphologically distinct sensilla observed in A. disparis whose locations and structure were similar to those of basiconic sensilla-3 in M. parasaissetiae ( Zhou et al 2013 ), sensillum chaetica type 4 in Anaphes victus (Hymenoptera: Mymaridae) and A. listronoti ( van Baaren et al 1999 ), sensilla basiconica type 1 in M. croceipe ( Ochieng et al 2000 ), uniporous pit pore sensilla trichodea D in T. nubilale ( Olson and Andow 1993 ), and sensilla basiconica in C. nacoleiae ( Zhang et al 2021 ). SBII are limited to the antennal apex of A. disparis and numerous other pteromalids, indicating that they are likely to function as contact chemoreceptors ( Weseloh 1972 , Amornsak et al 1998 ) involved in host recognition and acceptance ( Roux et al 2005 , Zhou et al 2013 , Zhang et al 2015 ).…”

“…STI are thought to function as mechanoreceptors, and their different morphological features have been characterized in many Hymenopteran families ( Olson and Andow 1993 , Isidoro et al 1996 , Amornsak et al 1998 , Ochieng et al 2000 , Pettersson et al 2001 , Bleeker et al 2004 , Roux et al 2005 , Gao et al 2007 , Dweck and Gadallah 2008 , Onagbola and Fadamiro 2008 , Zhang et al 2021 ). Our results showed that STI were the most numerous and widespread sensilla on the A. disparis antenna.…”

“…SBI morphology in A. disparis was similar to that of sensilla described previously in many parasitoid wasps ( Navasero and Elzen 1991 , Olson and Andow 1993 , Isidoro et al 1996 , Bleeker et al 2004 , Onagbola and Fadamiro 2008 ). These sensilla have been termed basiconic sensilla-2 in M. parasaissetiae ( Zhou et al 2013 ), sensilla trichodea TP in Cotesia glomerata (Hymenoptera: Braconidae) and C. rubecula ( Bleeker et al 2004 ), uniporous chaetica sensilla in P. cerealellae ( Onagbola and Fadamiro 2008 ), and sensilla chaetica I and II in Copidosomopsis nacoleiae (Hymenoptera: Encyrtidae) ( Zhang et al 2021 ). SBI are distinguished by the presence of cuticular fingers and numerous apical pores; they have been suggested to function as gustatory chemoreceptors for host recognition and to participate in contact chemoreception ( Altner and Prillinger 1980 , Olson and Andow 1993 , Pettersson et al 2001 , Roux et al 2005 ), including gustatory functions ( Isidoro et al 1996 , Barbarossa et al 1998 , Gao et al 2007 , Onagbola and Fadamiro 2008 ).…”