Ultrastructure Of Antennal Sensillae Of Ten Insect Pests Infesting Stored Products

Psocids belonging to Psocoptera(including Liposcelis bostrychophila Badonnel,L. entomophila Enderlein,L.tricolor Badonnel,L.decolor Pearman,and L.paeta Pearman),and beetles belonging to Coleoptera(including Callosobruchus chinensis L.,C.maculatus Fabricius, Tribolium castaneum Herbst,Sitophilus zeamais Motschulsky,and Oryzaephilus surinamensis(L.)) are important insect pests of stored-products.The economic losses caused by these pests' infestation to stored grains and other stored products are very serious.The antennae of adult insects have various types of sensilla with different functions,which are playing an important role in host location,discrimination behaviors,and mating.In this study,the external morphology,types, abundance,distribution,and internal structure are described using scanning electron microscopy (SEM) and transmission electron microscopy(TEM).The possible functions of these sensilla are discussed.Future functional antennal morphology,electrophysiological and molecular biology studies are needed to confirm these proposed functions.The main results are as follows:1 Antennal sensillae of five stored-product psocids pestsThe external morphology,types,and distribution of antennal sensillae in both male and female adults of five psocid species,Liposcelis bostrychophila,L.entomophila,L.tricolor,L.decolor,and L.paeta(Psocoptera:Liposcelididae) are described using SEM.The filiform antennae of the liposcelids are made up of the scape,pedicel,and a long flagellum composed of thirteen flagellomeres.Four morphological types of sensillae are recorded in both male and female species, including B(o|¨)hm bristles,chaetal sensillae,microtrichial sensillae,and basiconic sensillae.The abundance and distribution of four of these sensilla types on the antennae of male and female are not significantly different in the five psocids species studied.The most abundant sensilla is microtrichial sensillae.In addition,the possible physiological functions of the above sensilla types are discussed in light of previously published literature,including mechanoreception(B(o|¨)hm bristles and microtrichial sensillae) and olfaction(chaetal and basiconic sensillae).2 Antennal sensilla of two bruchid beetlesThe external morphologies of the antennal sensilla on the antennae of both female and male adults of two bruchid beetles,C.chinensis and C.maculatus(Coleoptera:Bruchidae),are described using SEM.Antennae of both species are made up of the scape,pedicel,and nine segments of flagellomeres.Antennae of female and male C.maculatus and female of C.chinensis are serrate in shape,while those of male C.chinensis are pectinate.Eight morphological sensilla types are recorded in both sexes,including b(o|¨)hm bristles(BB),two types of sensilla trichoid(ST1,ST2), sensilla chaetica(SC),two types of sensilla basiconic(SB1,SB2),grooved pegs(GP) and sensilla cavity(SCa).The number of ST1 and SB1 of the male were significantly different to those of the female of C.chinensis,and the number of ST2 and SB1 of the male were significantly different to those of the female of C.maculatus.The possible physiological functions of the above sensilla types are discussed in light of previously published literature.At least two olfactory sensilla,two sex-pheromone receptors,and two chemoreceptors are described on the antennae of both sexes.3 Antennal sensillae of T.castaneum,S.zeamais,and O.surinamensisThe external morphology,types,and distribution of antennal sensillae in both male and female adults of three beetles,T.castaneum,S.zeamais,and O.surinamensis are decribed using SEM.The antennae of female and male of T.castaneum are 11 antennomeres,the terminal three segments are prominent expanding to hammer in shape;the morphology of adult female and male of S.zeamais is geniculation,8 segments with swollen scape.The terminal flagellomere is oval.The filiform antennae of O.surinamensis are made up of the scape,pedicel,and a long fagellum composed of nine flagellomeres.The antennae of these three pests are not sexual dimorphism.Five morphological sensillae types are observed in both sexes of T.castaneum,including b(o|¨)hm bristles,sensilla trichoid (2 subtypes),sensilla chaetica,sensilla basiconic(4 subtypes),and sensilla styloconica.The antennae of female and male of S.zeamais are recorded only three types of sensillae,sensilla trichoid,sensilla chaetica,and sensilla basiconic(2 subtypes).Four major types of sensillae are observed on the antennae of female and male O.surinamensis:b(o|¨)hm bristles,sensilla trichoid,sensilla chaetica, sensilla basiconic.The number and distribution of each type sensilla on the antennae of female and male are not significantly different in the three species pests.Sensilla basiconic and sensilla styloconica are mostly assemblely distributed on the last three flagellomeres of T.castaneum.A sensilla cluster including sensilla chaetica and sensilla basiconic,is located on the terminal segment of the antennae of S.zeamais.Sensilla chaetica and sensilla basiconic are aggregated on the terminal three segments of antennae of both sexes O.surinamensis.In addition,the possible physiological functions of the above sensilla types are discussed in light of previously published literature.B(o|¨)hm bristles are mechanoreceptors,sensilla trichoid and sensilla basiconic of T.castaneum,S.zeamais, and O.surinamensis play a important role in olfaction,sensilla chaetica have dual chemo-and mechanoreceptors functions,sensilla styloconica is a thermo- or hygro-reception.4 Internal structure of antennal sensilla of C.chinensis,C.maculatus,and T. castaneumThe internal morphology of the various types of antennal sensillae on the antennae of both female and male adults of C.chinensis,C.maculatus,and T.castaneum are described using TEM. The internal structure of six types of antennal sensillae including b(o|¨)hm bristles(BB),two types of sensilla trichoid(ST1,ST2),two types of sensilla basiconic(SB1,SB2),and grooved pegs(GP) are described on the antennae C.chinensis.The cross sections of b(o|¨)hm bristles(BB),two types of sensilla trichoid(ST1,ST2),and two types of sensilla basiconic(SB1,SB2) are recorded on the antennae C.maculatus.The cross sections of six sensillae including b(o|¨)hm bristles(BB),two types of sensilla trichoid(ST1,ST2),sensilla chaetica(SC) and two types of sensilla basiconic(SB2,SB3). The intermediate of cross section of b(o|¨)hm bristles is an empty lumen with no dendritic branching. The cross sections of sensilla trichoid with thick walls and wall pores,are observed with abundant dendritic branches in the lumen.The internal structure of sensilla chaetica and sensilla basiconic are high densities of dendritic branches.The stalk of the grooved pegs consists of 11 fingerlike projection,that join at the tip of the stalk.There are deep grooves between the finger projections.Its lumen is encircled by a thick nonporous wall and is innervated by one unbranched dendrite.The possible physiological function of these sesilla are further discussed based on their internal structures.