Sensilla on antennae, ovipositor and tarsi of the larval parasitoids, Cotesia sesamiae (Cameron 1906) and Cotesia flavipes Cameron 1891 (Hymenoptera: Braconidae): a comparative scanning electron microscopy study

Abstract

Two braconid parasitoids of cereal stemborers in eastern Africa, Cotesia sesamiae and Cotesia fl avipes, have been shown to display a similar hierarchy of behavioural events during host recognition and acceptance. In order to understand the mechanisms underlying host recognition and acceptance, the morphology of antennal sensilla on the last antennomeres, on the ovipositor, and on the fi fth tarsomere and pretarsus of the prothoracic legs tarsi were studied using scanning electron microscopy followed by selective silver nitrate staining. It appeared that female C. sesamiae and C. fl avipes shared the same types and distribution of sensory receptors, which enable them to detect volatiles and contact chemical stimuli from their hosts. In both parasitoids, four types of sensilla were identifi ed on the three terminal antennomeres: (i) non-porous sensilla trichodea likely to be involved in mechanoreception, (ii) uniporous sensilla chaetica with porous tips that have gustatory functions, (iii) multiporous sensilla placodea, which are likely to have olfactory function, and (iv) sensilla coeloconica known to have thermo-hygroreceptive function. The tarsi of both parasitoids possessed a few uniporous sensilla chaetica with porous tips, which may have gustatory functions. The distal end of the ovipositor bore numerous dome-shaped sensilla. However, there were no sensilla coeloconica or styloconica, known to have gustatory function in other parasitoid species, on the ovipositors of the two braconid wasps.Résumé. Sensilles des antennes, de l'ovipositeur et des pattes de deux espèces de parasitoïde larvaire, Cotesia sesamiae (Cameron 1906) and Cotesia fl avipes Cameron 1891 (Hymenoptera : Braconidae) : une étude comparative en microscopie électronique à balayage. Deux espèces proches de guêpes parasitoïdes, Cotesia sesamiae et Cotesia fl avipes, présentent une similarité dans la hiérarchie des étapes comportementales associées à la reconnaissance et à l'acceptation de l'hôte. Afi n de développer des bases solides de recherche sur les mécanismes impliqués dans la reconnaissance et l'acceptation de l'hôte par ces deux espèces de parasitoïde, nous avons décrit la morphologie des sensilles situées sur les antennes (les derniers segments), l'ovipositeur et les tarses (le cinquième tarsomère et le prétarse des pattes antérieures). Des observations en microscopie électronique à balayage ont été menées et complétées par une coloration sélective au nitrate d'argent. Les femelles de C. sesamiae et C. fl avipes présentent les mêmes types de sensilles ayant les mêmes distributions leur permettant de détecter les volatils et les composés chimiques de contact provenant de leurs hôtes potentiels. Chez les deux espèces de parasitoïde, quatre types de sensilles sur les trois derniers segments antennaires ont été identifi és : (i) des sensilles trichoïdes non poreuses probablement impliquées dans la méchanoréception, (ii) des sensilles uniporeuses chaétiques (avec un pore terminal) potentiellement impliquées dans des fonctions gustatives, (ii...

Diverse Filters to Sense: Great Variability of Antennal Morphology and Sensillar Equipment in Gall-Wasps (Hymenoptera: Cynipidae)

“…Sensilla trichoidea type B also resemble the “ST 1 ” of Spathius agrili Yang (Braconidae) [104], the “sensilla chaetica type 1” of Cotesia spp. [75], the “sensillum chaeticum” of Telenomus reynoldsi Gordh & Coker (Platygastroidea: Scelioninae) [79] and the uniporous gustatory sensillum of T. basalis (Scelioninae) [55]. Sensilla trichoidea type C were observed in our study in all taxa, and represent the more numerous sensillar type on the cynipoid antennae, as also reported for other non-Aculeata lineages [55].…”

“…Also the number of SP per row seems to be higher in most Cynipoidea (>5 in 33 of the studied species) than in the other Proctotrupomorpha and in Ichneumonoidea (apparently no more than 4) [22], [26], [71]–[75], [80], which results in Cynipoidea having often SP narrowly or closely spaced in a row.…”

“…In Ichneumonoidea, SCa were observed in few Braconidae [74], though in most analysed species of this family it seems to be absent [18], [23], [25]–[27], [71], [75], [92]. Within Proctotrupomorpha excluding Cynipoidea, this sensilla type was observed in Scelioninae (Platygastroidea), Trichogrammatidae and Eupelmidae (Chalcidoidea) [22], [55], [88], [93], but is apparently absent in many other chalcidoid families such as Aphelinidae, Agaonidae, Pteromalidae, Eulophidae and Mymaridae [11], [29], [72], [76], [87].…”

Morphology, ultrastructure, and probable functions of the sense organs on the ovipositor stylets of the hymenoptran parasitoid, Venturia canescens (Gravenhorst)

“…Sense organs on the hymenopteran ovipositor stylets and sheath have been described by King and Fordy (1970), Ganesalingam (1972), van Lenteren (1972), Hawke et al (1973), Greany et al (1977), Le Ralec and Wagnberg (1990), Nénon et al (1997), Brown and Anderson (1998), Shah (1998), Cônsoli et al (1999), Quicke et al (1999), van Lenteren et al (2007), Dweck et al (2008), Boring and Sharkey (2009), Nacro and Nénon (2009), and Obonyo et al (2011) using electron microscopy.…”

The use of salivary α-amylase as an evolutionary solution to host selection in parasitoids

“…Previous studies have shown that VOCs do not convey reliable information to Cotesia flavipes species complex, which includes C. flavipes and C. sesamiae , on the suitability of caterpillar species but they are mere indicators of the presence of herbivores (Ngi-Song and Overholt, 1997; Obonyo et al, 2008). It is only when approaching the host that reliable information on host’ identity is perceived for which tactile and contact-chemoreception stimuli from the hosts play a major role in host recognition and oviposition, and it is hypothesized that protein(s) present in the host’s oral secretions are involved (Obonyo et al, 2010a; 2010b; 2011).…”