Ultrastructure of antennal sensilla of the peach aphid Myzus persicae Sulzer, 1776

The antennal sensilla of alate Myzus persicae were mapped using transmission electron microscopy and the ultrastructure of sensilla trichoidea, coeloconica, and placoidea are described. Trichoid sensilla, located on the tip of the antennae, are innervated by 2–4 neurons, with some outer dendrites reaching the distal end of the hair. Coeloconic sensilla in primary rhinaria are of two morphological types, both equipped with two dendrites. Dendrites of Type II coeloconic sensilla are enveloped in the dendrite sheath, containing the sensillum lymph. In sensilla coeloconica of Type I, instead, dendrites are enclosed by an electron opaque solid cuticle, with no space left for the sensillum lymph. The ultrastructure of big placoid sensillum reveals the presence of three groups of neurons, with 2–3 dendrites in each neuron group, while both small placoid sensilla are equipped with a single group of neurons, consisting of three dendrites. Both large and small placoid sensilla bear multiple pores on the outer cuticle. The function of these sensilla is also discussed. J. Morphol. 276:219–227, 2015. © 2014 Wiley Periodicals, Inc.     

Ultrastructure and distribution of sensilla on the antennae of female fig wasp Eupristina sp. (Hymenoptera: Agaonidae)

In the species‐specific and obligate mutualism between the fig (Moraceae: Ficus spp.) and its pollinator (Hymenoptera: Agaonidae), the continuity of lifecycle of both partners completely depends on the female pollinator's ability to detect receptive figs. To better understand the chemical location mechanism, we examined the antennae and their sensilla of the female fig pollinator Eupristina sp. using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The antennae of female Eupristina sp. are geniculated, and in total, there were seven types of sensilla found on the antennae: two types of multiporous placoid sensilla (type 1 is sausage‐like and type 2 is rounded), sensilla trichodea (ST), basiconic sensilla (BS), chaetica sensilla (ChS), coeloconic sensilla (CoS), and one specialized sensillum classified as sensillum obscurum (SO). We described external morphology, abundance, distribution, ultrastructure and discussed putative functions. We inferred from their ultrastructures as chemoreceptors that two types of multiporous placoid sensilla, BS and CoS, were innervated by sensory neurons. The aporous type ST, ChS, and SO were not innervated by dendrites which may function as mechanoreceptor/proprioceptor. These results were also discussed in relation to the interaction between Eupristina sp. and its host fig.     

External morphology of antennal sensilla of trichogramma australicum girault (Hymenoptera : Trichogrammatidae)

External morphology of antennal sensilla on female and male Trichogramma australicum (Hymenoptera : Trichogrammatidae) was examined using scanning electron microscopy. Antennae show strong sexual dimorphism in structure and types of sensilla. The female antenna displays 14 types of sensilla: basiconic capitate peg sensilla (types 1 and 2), campaniform sensilla, chaetica sensilla (types 1–3), coeloconic sensilla, falcate sensilla, placoid sensilla (types 1 and 2), styloconic sensilla and trichoid sensilla (types 1–3). The male antenna displays 12 types of sensilla: basiconic capitate peg sensilla (type 2), campaniform sensilla, chaetica sensilla (types 1–5), coeloconic sensilla, placoid sensilla (type 1), and trichoid sensilla (types 3–5). Falcate and styloconic sensilla occur only on the female antenna. Both sensilla probably are associated with host examination, host discrimination and oviposition behaviour. Male antennal trichoid sensilla types 4 and 5 are probably associated with courtship behaviour, because these types occur only on the male. We propose the term “falcate sensilla” for a unique female antennal sensilla; the number of falcate sensilla may be used for identification of Trichogramma spp. In addition, we report the presence of placoid sensilla type 2 and difference in structure of coeloconic sensilla in T. australicum. Variation in structure and position of antennal sensilla are discussed.     

Comparison of the antennal sensilla of females of four fig-wasps associated with Ficus auriculata

A comparison was performed of the antennal sensilla of females of four chalcid wasp species Ceratosolen emarginatus Mayr, 1906, Sycophaga sp., Philotrypesis longicaudata Mayr, 1906, and Sycoscapter roxburghi Joseph, 1957, which are specific and obligatory associated with Ficus auriculata (Lour, 1790). The four species exhibit different oviposition strategies in the fig ovules where their offspring hatch and develop. Antennal sensilla morphology was evaluated using scanning electron microscopy. Females of the four species present 11 morphologically similar types of sensilla: trichoid sensilla, sensilla obscura, chaetica sensilla 1 and 2, which all have mechanosensory functions; uniporous basiconic sensilla, which are presumably contact chemosensilla; basiconic capitate peg sensilla, coeloconic sensilla 1, multiporous basiconic and placoid sensilla, which may be regarded as olfactory sensilla, and coeloconic sensilla 2 and 3, which are presumed to be proprioreceptors or pressure receptors. The four species have significant differences in the abundance and arrangement of trichoid sensilla and chaetica sensilla 1 on the flagellum. The coeloconic sensilla and sensilla obscura only occur on the antennae of C. emarginatus that enter figs. The chemosensilla which are presumably involved in host discrimination, i.e., basiconic sensilla, multiporous placoid sensilla and basiconic capitate peg sensilla, are similar in shape and configuration, although they present some differences in abundance. These findings provide practical information on the adaptations of fig wasps and the relationship between multisensory antennae and functions in fig wasp behaviour.     

Antennal sensilla of whiteflies: Trialeurodes vaporariorum (Westwood), the glasshouse whitefly,Aleyrodes proletella (Linnaeus), the cabbage whitefly,and Bemisia tabaci (Gennadius), the tobacco whitefly (Homoptera : Aleyrodidae). Part 1: External morphology

Scanning electron microscopy has revealed the detailed structure of the antennae of three species of whitefly, Trialeurodes vaporariorum, Aleyrodes proletella, and Bemisia tabaci (Homoptera : Aleyrodidae). All 3 species have microtrichia and 5 types of sensilla on the antennae: chaetica, campaniform, basiconic, coeloconic, and pegs with digitate tips, the latter 3 of these being unique to the flagellum. The number and distribution of the sensilla unique to the flagellum vary among the species studied. The cuticle of the basiconic and the coeloconic sensilla is pitted and grooved, respectively, a prerequisite for an olfactory and/or a thermo-, hygroreceptive function. A sexual dimorphism does occur with respect to the position of the basiconic sensilla on flagella segment 5 of A. proletella, but not T. vaporariorum or B. tabaci.     

Morphological and functional heterogeneity in olfactory perception between antennae and maxillary palps in the pumpkin fruit fly,Bactrocera depressa

The morphology and ultrastructure of the olfactory sensilla on the antennae and maxillary palps were investigated through scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and their responses to five volatile compounds were measured using electroantenogram (EAG) and electropalpogram (EPG) techniques in the pumpkin fruit fly, Bactrocera depressa (Shiraki; Diptera: Tephritidae). Male and female B. depressa displayed distinct morphological types of olfactory sensilla in the antennae and maxillary palps, with predominant populations of trichoid, basiconic, and coeloconic sensilla. Basiconic sensilla, the most abundant type of olfactory sensilla in the antennae, could be further classified into two different types. In contrast, the maxillary palps exhibited predominant populations of a single type of curved basiconic sensilla. High‐resolution SEM observation revealed the presence of multiple nanoscale wall‐pores on the cuticular surface of trichoid and basiconic sensilla, indicating that their primary function is olfactory. In contrast, coeloconic sensilla displayed several longitudinal grooves around the sensillum peg. The TEM observation of individual antennal olfactory sensilla indicates that the basiconic sensilla are thin‐walled, while the trichoid sensilla are thick‐walled. The profile of EAG responses of male B. depressa was different from their EPG response profile, indicating that the olfactory function of maxillary palps is different from that of antennae in this species. The structural and functional variation in the olfactory sensilla between antennae and maxillary palps suggests that each plays an independent role in the perception of olfactory signals in B. depressa.     

Antennal sensilla and their nerve innervation in first‐instar nymphs of Porphyrophora sophorae Arch. (Hemiptera: Coccomorpha: Margarodidae)

ABSTRACT Porphyrophora (Hemiptera: Coccomorpha: Margarodidae) is a genus of soil‐inhabiting scale insects. The antennal sensilla and their innervation in the first‐instar nymphs of Porphyrophora sophorae were studied using light microscopy and scanning and transmission electron microscopy to understand the function of these sensilla and determine the sensillar innervation feature on these small antennae. The results show that the six‐segmented antennae of these nymphs have 20–23 sensilla which can be morphologically classified into seven types, for example, one Böhm's bristle (Bb), one campaniform sensillum (Ca), one Johnston's organ (Jo), 13–16 aporous sensilla trichodea (St), two coeloconic sensilla (Co), one straight multiporous peg (Mp1), and one curvy multiporous peg (Mp2). According to their function, these sensilla can be categorized into three categories: mechanoreceptors, that is, Bb, Ca, Jo, and St; thermo/hygroreceptors, that is, Co only; and chemoreceptors, that is, Mp1 and Mp2. The dendrites that innervate the Mp1, Mp2, and Co sensilla combine to form a large nerve tract (NT1) in the antennal lumen. Because NT1 extends through and out of the antenna, the somata of these neurons are present in the lymph cavity of the insect's head. The dendrites that innervate the mechanoreceptors form another nerve tract (NT2). The somata of these neurons are located inside the scape and pedicel. J. Morphol. 277:1631–1647, 2016. © 2016 Wiley Periodicals, Inc.     

Comparison of antennal sensilla of Anaphes victus and A. listronoti (Hymenoptera, Mymaridae), egg parasitoids of Curculionidae

Antennal sensilla were compared in females and males of two sympatric mymarid Hymenoptera, Anaphes victus and A. listronoti which are, respectively, solitary and gregarious parasitoids of eggs of the carrot weevil Listronotus oregonensis (Coleoptera, Curculionidae). Both species are morphologically very similar in the area where they are sympatric. The external morphology of the sensilla was studied using scanning electron microscopy. Female antennae have seven different types of sensilla, morphologically similar in the two species: trichoid sensilla, which are putative mechanosensilla, sensilla chaetica types 1, 3 and 4, which are presumably contact chemosensilla, and sensilla chaetica type 2 and basiconic and placoid sensilla, which are presumed to be olfactory sensilla. The major difference between the two species is the number of sensilla chaetica type 4, of which 6–9 are found on the antennal club in A. victus, while 10–12 are present in A. listronoti. The antennae of the males of both species are similar in morphology and in the number and distribution of their four types of sensilla, i.e. trichoid sensilla, sensilla chaetica type 1 and basiconic and placoid sensilla. Accepted: 23 November 1998     

The gustatory sensilla on the endophytic ovipositor of Odonata

The present paper aims at describing the fine structure of coeloconic sensilla located on the cutting valves of the endophytic ovipositor of two Odonata species, the anisopteran Aeshna cyanea (Aeshnidae) and the zygopteran Ischnura elegans (Coenagrionidae), by carrying out parallel investigations under SEM and TEM. In both species these coeloconic sensilla are innervated by four unbranched neurons forming four outer dendritic segments enveloped by the dendrite sheath. One dendrite terminates at the base of the peg forming a well developed tubular body, while the other three enter the peg after interruption of the dendrite sheath. The cuticle of the peg shows an apical pore and a joint membrane. This last feature, together with the tubular body and the suspension fibers, represent the mechanosensory components of the sensillum while the pore and the dendrites entering the peg allow chemoreception. The ultrastructural organization of these coeloconic sensilla is in agreement with the one reported for insect gustatory sensilla. Our investigation describes for the first time typical insect gustatory sensilla in Odonata. Electrophysiological and behavioral studies are needed to verify the role that these structures can perform in sensing the egg-laying substrata.     

Sexual dimorphism of antennal and ovipositor sensilla of Tetrastichus sp. (Hymenoptera: Eulophidae)

Tetrastichus sp. (Hymenoptera: Eulophidae) is a primary parasitoid of the Metisa plana (Lepidoptera: Psychidae), an oil palm bagworm. The sensilla on the surface of the antenna and ovipositor of Tetrastichus sp. were examined using a scanning electron microscope. The antennae of both male and female Tetrastichus sp. are geniculate in shape and hinged at the scape-pedicel joint. The female antenna is about 200 µm longer than the male antenna. However, the male antenna has an additional flagellomere compared to the female antenna. In total, eight different types of antennal sensilla were observed on the antenna of Tetrastichus sp.: trichoid sensilla type 1, 2, 3, 4, placoid sensilla type 1 and 2, basiconic sensilla, and campaniform sensilla. The antenna of the female Tetrastichus sp. lacks placoid sensilla type 2 and campaniform sensilla. The distribution and abundance of the antennal sensilla were compared between the male and female Tetrastichus sp. and discussed. On the ovipositor stylet of Tetrastichus sp., coeloconic sensilla, styloconic sensilla and campaniform sensilla were observed. Trichoid sensilla were observed at the medial part of the distal extremity of the ovipositor.     

木瓜榕传粉榕小蜂雌蜂触角感器的分布和超微形态

为探索木瓜榕传粉榕小蜂Ceratosolen emarginatus寄主定位机制, 应用扫描电镜和透射电镜观察了其雌蜂触角感器的类型、 分布和超微形态。结果显示： 木瓜榕传粉榕小蜂雌蜂触角呈膝状, 由柄节、 梗节和11个鞭小节组成的鞭节组成, 第3鞭小节着生一坚固的脊骨突。触角上共发现7类11种感器, 分别为毛形感器、 刺形感器、 锥形感器（包括单孔形和多孔形）、 多孔板形感器（包括长形和圆形）、 腔锥形感器（分为3种类型）、 栓锥形乳突状感器、 角锥形感器。结合表面特征和内部结构, 锥形感器、 多孔板形感器、 栓锥形乳突状感器和腔锥形感器类型1为有孔型, 为化学感器; 无孔型的毛形感器和刺形感器是机械感器, 但腔锥形感器类型2和3为本体感器或湿热压力感器; 最为特异的为角锥形感器, 其厚壁无孔, 逆向触角主轴, 为该科昆虫所特有, 推测可防止传粉榕小蜂进入榕果时滑脱。这些结果将有助于理解木瓜榕传粉榕小蜂特异性行为, 并为下一步开展电生理研究, 揭示其信息化学物质利用和分配模式奠定基础。     

Morphology and ultrastructure of sense organs on the ovipositor of Trybliographa rapae,a parasitoid of the cabbage root fly

The ovipositor of the parasitoid wasp Trybliographa rapae was examined by scanning and transmission electron microscopy. Characteristic peg-like sensilla with a cuticular ring at the base are found at the tip of the ventral valves, where they occur in a characteristic arrangement of triplets. The unusual basal structure probably protects the sensilla against damage during movement through the substrate and piercing of the host cuticle. These sensilla are each innervated by six dendrites, some of which have lamellated tips, generally considered to be characteristic of thermosensitivity. It is suggested that the remaining dendrites are gustatory, and as such probably respond to factors present in host haemolymph. A second type of peg-like sensillum is found on both the dorsal and the ventral valves. These are set in deep pits so that only the tip of the peg protrudes above the surface of the cuticle. These occur along the length of the ovipositor shaft and ultrastructural studies reveal the pegs to be innervated by a single mechanosensitive dendrite, probably monitoring the movement of the ovipositor through the substrate.     

Morphological and ultrastructural characterization of olfactory sensilla in Drosophila suzukii: Scanning and transmission electron microscopy

Drosophila suzukii is a serious horticultural and quarantine pest, damaging various berry crops. Although the active use of olfactory communication in D. suzukii is well-known, their olfactory sensory system has not been comprehensively reported. Therefore, the present study was carried out to understand the morphology, distribution and ultrastructure of olfactory sensilla present in the antennae and maxillary palps of D. suzukii, through scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The olfactory sensilla on the antennae of D. suzukii in both sexes could be classified into three major morphological types, basiconic, trichoid and coeloconic sensilla, according to their shapes. The antennal basiconic sensilla were further divided into three subtypes and the antennal trichoid sensilla into two subtypes, respectively, according to the size of individual sensillum. In contrast to the antennal olfactory sensilla showing diverse morphology, basiconic sensilla was the only type of olfactory sensilla in the maxillary palps of D. suzukii. The basiconic sensilla in the maxillary palps could be further classified into three subtypes, based on their size. Our SEM and TEM observations indicated that multiple nanoscale pores are present on the surface of all types of olfactory sensilla in the antennae and maxillary palps, except coeloconic sensilla. The difference in the morphological types and the distribution of olfactory sensilla suggests that their olfactory functions are different between antennae and maxillary palps in D. suzukii. The results of this study provide useful information for further studies to determine the function of olfactory sensilla in D. suzukii and to understand their chemical communication system.     

Morphology and untrastructure of the antennal sense organs in tenebrionid larvae <Emphasis Type="Italic">Tenebrio molitor</Emphasis> L. and <Emphasis Type="Italic">Zophobas rugipes</Emphasis> Kirsch (Coleoptera: Tenebrionidae)

The distribution, external morphology, and ultrastructure of various types of sensilla in the antennae of tenebrionid larvae Tenebrio molitor and Zophobas rugipes are studied by means of scanning and transmission electron microscopy. On the antennae of T. molitor there are sensilla of four basic morphological types: basiconic, styloconic, trichoid, and papillate sensilla. On the antennae of Z. rugipes, in addition to the aforementioned ones, there are placoid sensilla. Ultrastructure points to olfactory function of basiconic and placoid sensilla. Other sensillum types are contact chemoreceptors.     

The fine structure and possible function of the sensory setae of the penis of Balanus balanoides (L.)

The structure and innervation of the sensory setae which are present in large numbers on the penis of Balanus balanoides (L.) have been established by scanning and transmission electron microscopy. Each seta contains a small number of sensory dendrites surrounded by an extracellular supporting tube which is presumed to be secreted by the enclosing sheath cell. The dendrites, which distally extend beyond both the sheath cell and supporting tube, terminate at the tip of the seta within a pore-like invagination of the cuticle and thus are in direct contact with the environment. Proximally bundles of dendrites pass into the penis tissue where they are surrounded by several sheath cells. The supporting tube terminates at a point within the body of the penis where a series of intracellular rods arise. The ciliary character of the dendrites is evident in this region, the microtubules being organized into the (9 × 2) +2 pattern. It is deduced that the sensilla are chemosensory; their structure is compared with that of other crustacean sensilla which are presumed to be chemosensory.     

Morphology and distribution of antennal sensilla of the tarnished plant bug,Lygus lineolaris (Palisot de beauvois) (Hemiptera: Miridae)

Sensilla on the antennae of adult and last-instar nymphs of the tarnished plant bug, Lygus lineolaris (Hemiptera: Miridae), were examined with light, scanning and transmission electron microscopy. Six different types were identified in adult females and males and 5 types in last-instar nymphs: types 1 and 4 are sensilla trichodea, 2 and 3 are sensilla chaetica, and 5 and 6 are sensilla basiconica. Type 1 are located at distal region of terminal segment and type 2 are located at distal regions of proximal 3 segments in both adults and nymphs. Type 3 is present on all segments, more numerous on scape and pedicel and less abundant on distal third and fourth segments in both adult and nymphal stages. Types 4 and 6 are absent on the scape and present on the distal 3 antennal segments in adults, but they are present only on the distal-most antennal segment in nymphs. Type 5 sensilla are present only on second antennal segments in adults and are absent in nymphs. Sexual dimorphism is observed in total numbers: there are significantly more type(s) 3, 4, 5 and 6 sensilla in adult males than adult females. Types 1, 4 and 5 are multiporous with thin cuticle, branched dendrites and pore tubules which suggests an olfactory function. These sensilla have 3, 3 and 2 neurons, respectively. The type 6 sensillum has an apical pore and pores in the cuticular wall, and is innervated by 5 nerve cells with unbranched dendrites. Sensillar types 2 and 3 have thick cuticle, a single apical pore and nerve cells with unbranched dendrites. Type 2 has 1 neuron and type 3 has 2 chambers and 2 nerve cells.     

Apical antennal sensilla in nymphs of Libellula depressa (Odonata: Libellulidae)

Abstract. In an ultrastructural study of the apical antenna of the last nymphal stages of Libellula depressa (Odonata: Libellulidae), we found long sensilla trichodea, 2 sensory pegs, and a coeloconic sensillum on the last article of the flagellum (the distal part of the antenna). The long sensilla trichodea are mechanoreceptors, almost identical to the long filiform hairs of some terrestrial insects and the first sensilla of this kind to be described in aquatic insects. Particular attention was given to the complex coeloconic sensillum, a compound sensillum innervated by 2 groups of 3 neurons wrapped in a dendritic sheath. A cuticular sleeve envelops the distal portion of the outer dendritic segment. The cuticle of the coeloconic sensillum shows wide channels and is contiguous to the underlying granular and fibrillar layer. Similar structures on the antennae of the adults of other dragonflies were identified as chemoreceptors in previous studies. We hypothesize that this larval coeloconic sensillum might likewise have a chemosensory function, responding to molecules that diffuse through the cuticle and the underlying granular and fibrillar layer, as no clear pore or pore-tubule system is visible. Alternative functions are also explored on the basis of morphological details.     

伪鞘榕小蜂雌雄成虫触角感器的超微形态、分布及适生意义

伪鞘榕小蜂Sycoscapter trifemmensis是一种寄生于鸡嗉子榕间花期榕果的专性寄生蜂,雌雄两性繁殖策略分化明显,为更好理解和诠释雌蜂寄主定位和雄蜂配偶识别机制,有必要对两性的触角感器进行观察。运用环境扫描电镜观察,对比和探讨了伪鞘榕小蜂雌雄成虫的触角和触角感器类型、分布、数量及其生态适应性。结果表明:雌蜂触角鞭节由11鞭小节组成,总长817.82±33.23μm,分布有毛形感器、刺形感器(类型1)、锥形感器(类型1)、多孔板形感器(类型1)、栓锥形乳突状感器5类5种;雄蜂触角鞭节仅由6鞭小节组成,全长为雌蜂的1/3,且各节有明显的缩短和增粗特征,着生感器包括毛形感器、刺形感器(类型2和类型3)、锥形感器(类型1和类型2)、多孔板形感器(类型2)、腔锥形感器5类7种。雌蜂触角感器的数量与分布显著高于雄蜂,且同类型感器在雌蜂上具有明显的延伸、增粗、分支的特征,以板形感器和锥形感器最为突出。伪鞘榕小蜂雌雄成虫的触角及其感器有明显的性二型,特别是与化学信息识别相关的感器,反映了雌雄蜂在不同生态环境和繁殖压力下的形态分化、行为策略和生态适应。     

Antennal sensilla of whiteflies: Trialeurodes vaporariorum (Westwood), the glasshouse whitefly,and Aleyrodes proletella (Linnaeus), the cabbage whitefly, (Homoptera : Aleyrodidae). Part 2: Ultrastructure

A transmission electron microscope study of the antennal sensilla of the whitefly Trialeurodes vaporariorum and Aleyrodes proletella (Homoptera : Aleyrodidae) revealed that of the sensilla unique to the antennal flagellum (basiconic, coeloconic and small digitate-tipped sensory pegs), basiconic and coeloconic sensilla occur as subtypes. Four subtypes of basiconic cone sensilla occur on the flagella of T. vaporariorum and 3 on A. proletella. All the subtypes of basiconic sensilla have an ultrastructure typical of olfactory sensilla and probably have a primary olfactory function. Two subtypes of coeloconic sensilla occur on the flagella of both species. Their ultrastructure suggests primarily a chemosensory function. The digitate-tipped sensory peg of both species possesses a triad of neurones which have ultrastructural characteristics similar to the known thermo-/hygroreceptors of other insect species. The other sensilla, which occur on the antennae of the whiteflies, include cheatae, campaniform and subcuticular sensilla, all of which have an ultrastructure typical of mechanoreceptors.