Sexual dimorphism in antennal morphology and sensilla ultrastructure of a pupal endoparasitoidTetrastichus howardi(Olliff) (Hymenoptera: Eulophidae)

Abstract

Tetrastichus howardi (Olliff) (Hymenoptera: Eulophidae), a pupal parasitoid of a great number of Lepidoptera pests, has a great potential for biological control. To investigate the olfactory system of this parasitoid, we examined the morphology and ultrastructure of the antennal sensilla of both male and female T. howardi using scanning and transmission electron microscopic techniques. Antennae of male and female T. howardi were geniculate in shape, which consisted of scape, pedicel and flagellum with 5 and 4 flagellomeres, respectively. The sexual differences were recorded in the types, structure, distribution and abundance of antennal sensilla of T. howardi. Fourteen morphologically distinct types of antennal sensilla were found on the female antennae, while seventeen on the male antennae. They were: multiporous plate sensilla (MPS1-4), chaetica sensilla (CH1-3), multiporous trichodea sensilla (MTS), aporous trichodea sensilla (ATS1-5), multiporous grooved peg sensilla (MGPS), coeloconic sensilla (COS), campaniform sensilla (CAS), terminal finger-like hairy sensilla (TFI), cuticular pore (CP), and ventral sensory plaque (VSP). MPS4, ATS (3-5), and VSP only occurred on the male antennae, while MPS2 and MPS3 only on the female antennae. The MPSs, MTS, MGPS, TFI, and CP may function as olfactory sensilla involving in detecting odor stimuli whereas the ATSs, CHs, and CAS may serve as mechanoreceptors. COS were presumed to play a role as chemo-, thermo- or hygro-receptor. The results could facilitate future studies on the biology of olfaction in T. howardi.

Ultrastructure of Female Antennal Sensilla of an Endoparasitoid Wasp,Quadrastichus mendeliKim & La Salle (Hymenoptera: Eulophidae: Tetrastichinae)

“…Previous research on many Hymenoptera belonging to different families also suggested that Böhm may function as proprioceptors perceiving antennal movement (Xin et al, 2010; Hong et al, 2016). SCa have also been found in many insects, including Coleoptera and Hymenoptera species (Zheng et al, 2016; Faucheux & Kundrata, 2017). In the SCa, the curve of the sensory dome is modified by the stretching and muscular contractions of the pedicel, and also by external pressure on the sensillum dome.…”

“…Hierarchical cluster analysis was used to analyze similarities between 16 parasitoids of Eulophidae species based on the types of antennal sensilla, such as Tetrastichus hagenowii Ratzeburg (Barlin et al, 1981), Sympiesis sericeicornis Nees (Meyhofer et al, 1997), Aprostocetus fukutai Miwa & Sonar and Aprostocetus prolixus La Salle & Huang (Wang et al, 2007), Diglyphus isaea Walker (Zou et al, 2009), Microdonophagus levis Schauff and Microdonophagus woodleyi Schauff (Hansson, 2009), Tamarixia radiata Waterston (Onagbola et al, 2009), Tetrastichus brontispae Ferrière (Xin et al, 2010), Tetrastichus nigricoxae Yang (Wang et al, 2012), Chouioia cunea Yang (Xu et al, 2013), Tetrastichus planipennisi Yang (Gao et al, 2013), Tetrastichus howardi Olliff (Zheng et al, 2016), Tetrastichus septentrionalis Yang (Hong et al, 2016), and Trichospilus pupivorus Ferrière (Da Silva et al, 2016).…”

“…In China, three hymenopteran parasitoids of L. invasa have been found, including Quadrastichus mendeli Kim & La Salle (Eulophidae), Aprostocetus causalis La Salle & Wu (Eulophidae) and Megastigmus sichuanensis Doğanlar & Zheng (Torymidae) (Zheng et al, 2016; Doğanlar et al, 2017). Among these natural enemies, Q. mendeli is a uniparental and solitary idiobiont endoparasitoid.…”

“…The antennae, as an essential part of the olfactory system in parasitic Hymenoptera, are involved in various sensitivities caused by physical and chemical stimuli, including physical/mechanical cues (e.g., host vibration), habitat searching, host discrimination, host detection, host acceptance, and oviposition by using different types of sensilla (Isidoro et al, 1996). Antennal sensilla have been investigated in some hymenopteran parasitoids, including Trichogrammatidae (Amornsak et al, 1998), Pteromalidae (Onagbola & Fadamiro, 2008), Braconidae (Ahmed et al, 2013), Aphelinidae (Zhang et al, 2014), Encyrtidae (Fortuna et al, 2015), Eulophidae (Zheng et al, 2016), and Torymidae (Huang et al, 2017). To better understand host-detection mechanisms of Q. mendeli adults, the external and internal morphology, types, number, distribution, length, and width of antennal sensilla were investigated.…”

Morphological characterization of antennae and antennal sensilla of Diaphorina citri Kuwayama (Hemiptera: Liviidae) nymphs

“…On the antennae of the fourth-and fifth-instar nymphs, only one SCA was presented on the second segment of the antennae. The SCA seems to occur in aging nymphs (the fourth-instar nymph of A. dispersus and the fifth-instar nymph of P. pyricola) [27,32] or adults (Tetrastichus howardi and A. dispersus) [35,46]. Previous studies have reported that the SCA with no pores in their cuticular structure play the role of mechanoreceptors [29,37,[47][48][49][50][51], whereas the SCA with pores was involved in gustatory system as well as in humidity reception [52].…”