Ultrastructure of the chemosensitive basiconic single-walled wall-pore sensilla on the antennae in adults and embryonic stages of Locusta migratoria L. (Insecta,Orthoptera)

Summary The structure and embryonic development of the two types (A, B) of basiconic sensilla on the antennae of Locusta migratoria were studied in material that had been cryofixed and freeze-substituted, or chemically fixed and dehydrated. Both types are single-walled wall-pore sensilla. Type-A sensilla comprise 20–30 sensory and 7 enveloping cells. One enveloping cell (thecogen cell secretes the dendrite sheath); four are trichogen cells, projections of which form the trichogen process during the 2nd embryonic molt. The trichogen cells form two concentric pairs proximally. Two tormogen cells secrete the cuticular socket of the sensillum. The dendritic outer segments of the sensory cells are branched. Bifurcate type-A sensilla have also been observed. Type-B sensilla comprise three sensory and four enveloping cells (one thecogen, two trichogen and one tormogen). The trichogen process is formed by the two trichogen cells, each of which gives rise to two projections. The trichogen cells are concentrically arranged. The dendritic outer segments of the sensory cells are unbranched. In the fully developed sensillum, all trichogen and tormogen cells border on the outer receptor lymph cavity. It is suggested that the multicellular organization of the type-A sensilla can be regarded as being advanced rather than primitive.Supported by the Dcutschc Forschungsgemeinschaft (SFB 4/G1)     

Volume and surface of receptor and auxiliary cells in hygro-/thermoreceptive sensilla of moths (Bombyx mori,Antheraea pernyi,and A. polyphemus)

Summary The thermo/hygroreceptive sensilla styloconica of the silkmoths Bombyx mori, Antheraea pernyi, and A. polyphemus were reconstructed from serial sections of cryofixed and chemically fixed specimens. The volume and surface area of the different sensillar cells were calculated from the area and circumference of consecutive section profiles. In addition, data are provided on the length and diameter of the outer and inner dendritic segments of the receptor cells. The morphometric data obtained from the three species are highly consistent and significantly different from those of olfactory sensilla trichodea of the same species. In each sensillum two type-1 receptor cells (hygroreceptors) are associated with one type-2 cell with a lamellated outer dendritic segment, a comparatively thick inner dendritic segment, and a particularly large soma (thermoreceptor). In contrast to olfactory sensilla, the thecogen cell is the largest auxiliary cell forming an extensive apical labyrinth bordering the inner sensillum-lymph space, whereas an inconspicuous trichogen cell and a medium-sized tormogen cell border a comparatively small outer sensillum-lymph cavity. Moreover, both sensillum-lymph spaces are separated from each other not only by the dendrite sheath, but also by the trichogen cell. The results are discussed with regard to recent electrophysiological observations and current hypotheses on the function of sensilla.     

Ultrastructure of a possible new type of crustacean cuticular strain receptor in Carcinus maenas (crustacea,decapoda)

A hitherto unknown sensillum type, the “intracuticular sensillum” was identified on the dactyls of the walking legs of the shore crab, Carcinus maenas. Each sensillum is innervated by two sensory cells with dendrites of “scolopidial” (type I) organization. The ciliary segment of the dendrite is 5–6 μm long and contains A-tubules with an electron-dense core and dynein arm-like protuberances; the terminal segment is characterized by densely packed microtubules. The outer dendritic segments pass through the endo- and exocuticle enclosed in a dendritic sheath and a cuticulax tube (canal), which is suspended inside a slit-shaped cavity by cuticular lamellae. The dendrites and the cavity terminate in a cupola-shaped invagination of the epicuticle. External cuticular structures are lacking. Three inner and four to six outer enveloping cells are associated with each intracuticular sensillum. The innermost enveloping cell contains a large scolopale that is connected to the ciliary rootlets inside the inner dendritic segments by desmosomes. Scolopale rods are present in enveloping cell 2. Since type I dendrites and a scolopale are regarded as modality-specific structures of mechanoreceptors, and since no supracuticular endorgan is present, the intracuticular sensilla likely are sensitive to cuticular strains. The intracuticular sensilla should be regarded as analogous to insect campaniform sensilla and arachnid slit sense organs.     

Ultrastructure and receptor cell responses of the antennal grooved peg sensilla of Triatoma infestans (Hemiptera: Reduviidae)

Ultrastructural examination of grooved-peg (GP) sensilla on the antenna of fifth instar Triatoma infestans nymphs by scanning electron microscopy and transmission electron microscopy reveal that they are 8–18 μm long with a diameter of about 2–2.8 μm at the non-articulated base. Some pegs have a terminal pore. These double-walled wall-pore (dw-wp) sensilla have an outer cuticular wall with 13–18 longitudinal grooves at the distal part of the peg. Groove channels are present at the bottom of the grooves from which radial spoke channels lead into the inner sensillum-lymph cavity. A dendrite sheath connects the tip of the thecogen cell to the inner cuticular wall thus forming separated outer and inner sensillum-lymph cavities. Four or five bipolar receptor cells are ensheathed successively within the GP sensilla by the thecogen cell, trichogen and tormogen cells. The inner dendritic segments of each sensory cell give rise at the ciliary constriction to an unbranched outer dendritic segment which can reach the tip of the sensillum.Electrophysiological recordings from the GP sensilla indicate that they house NH₃, short-chain carboxylic acid and short-chain aliphatic amine receptor cells and can be divided into three functional sub-types (GP 1–3). All GP sensilla carry a receptor cell excited by aliphatic amines, such as isobutylamine, a compound associated with vertebrate odour. GP type 1 and 2 sensilla house, in addition, an NH₃-excited cell whereas the type 2 sensilla also contains a short-chain carboxylic acid receptor. No cell particularly sensitive to either NH₃ or carboxylic acids was found in the grooved-peg type 3 sensilla. GP types 1, 2 and 3 represent ca. 36, 10 and 43% of the GP sensilla, respectively, whereas the remaining 11% contain receptor cells that manifest normal spontaneous activity but do not respond to any of the afore mentioned stimuli.     

Fine structure of the pheromone-sensitive sensilla on the antenna of the hawkmoth, Manduca sexta

The flagellar antenna of the male hawkmoth Manduca sexta carries about 42,000 pheromone-sensitive sensilla trichodea, which are arranged in 'baskets' on the single segments. Each sensillum consists of a cuticular hair up to 500 mum long and is innervated by two bipolar sensory neurons. Each neuron sends an unbranched dendrite into the hair shaft. The dendrite is subdivided by a short ciliary region into an inner and an outer segment. The inner segment is especially rich in smooth vesicles, which accumulate beneath the ciliary region where they seem to fuse with the dendritic membrane. The outer dendritic segment often shows conspicuous 'beads' along its length. Three auxiliary, or enveloping, cells belong to each adult sensillum. These are the thecogen, the trichogen, and the 'outer' cell. Most probably, the latter is not homologous with the 'traditional' tormogen cell from a genealogical point of view.     

Antennal sensilla ofNeomysis integer (leach)

Summary The most frequent type of the hair sensilla on the antennae ofNeomysis integer is investigated by electron microscopic methods. The cellular properties of the sensilla are compared with those of other arthropods in order to detect possible homologies.The hairs are innervated by 2, 3, 6, 8, 9, or 10 sensory cells. The dendrites show an inner and outer dendritic segment. Five or six enveloping cells belong to a sensillum. In intermoult stage, processes of all the enveloping cells except the innermost one extend into the hair shaft. The sensory hairs possess only a single liquor cavity, which morphologically is homologous to the inner lymph cavity of insect sensilla. Around the liquor cavity, a supporting structure is located which seems to be identical to the scolopale of chordotonal organs. The six-to tenfold-innervated hairs possess two groups of differently structured dendrites which are regularly arranged on opposite sides of the liquor cavity. The outer dendritic segments are enclosed in a dendritic sheath. It is secreted by the innermost enveloping cell (= dendritic sheath cell of insect sensilla). All the outer dendritic segments terminate in the distal region of the hair shaft which shows a pore at its tip. The possible function of the sensilla is discussed. The double and triple-innervated hairs are considered to be mechano-receptors, whereas the sensilla associated with six to ten sensory cells might be mechano-chemoreceptors.     

The coelocapitular sensillum,an antennal hygro- and thermoreceptive sensillum of the honey bee,Apis mellifera L.

Summary The sensillum coelocapitulum, a hygro- and thermoreceptive sensillum of the honey bee, Apis mellifera, was investigated by electron microscopy. The cuticular apparatus of the sensillum is a mushroomshaped protrusion, devoid of pores, set in a narrow cylindrical pit positioned centrally within a cuticular, shallow depression. There may be three or four receptor cells. Three receptor cells have unbranched sensory cilia, containing densely packed microtubules, which extend distally into the cuticular apparatus and completely fill its cavity. These connecting cilia are of the usual 9+0 type. The fourth receptor, if present, has a thin sensory cilium which terminates beneath the cuticular apparatus. Its connecting cilium has armed outer doublets. The outer cavity is formed by two enveloping cells and is completely sealed off. Lipid deposits are present within the cavity and the tormogen cell. The thecogen cell has scolopale rod-like structures around the inner cavity. Features common to the insect hygro- and thermoreceptive sensilla are discussed in comparison with those of other insects.     

Atlas of olfactory organs of Drosophila melanogaster 2. Internal organization and cellular architecture of olfactory sensilla

Antennae and maxillary palps of Drosophila melanogaster were studied with the electron microscope on serial sections of cryofixed specimens. The number of epidermal cells roughly equals the number of sensilla, except for regions where the latter are scarce or absent. Each epidermal cell forms about two non-innervated spinules, a prominent subcuticular space and a conspicuous basal labyrinth, suggesting a high rate of fluid transport through the sensory epithelium. The internal organization and fine structure of trichoid, intermediate and basiconic sensilla is very similar. Receptor cell somata are invested by thin glial sheaths extending distad to the inner dendritic segments. Further distally, the thecogen cell forms a sleeve around the dendrites, but an extracellular dendrite sheath is absent. At the base of the cuticular apparatus, the inner sensillum-lymph space around the ciliary and outer dendritic segments is confluent with the large outer sensillum-lymph space formed by the trichogen and tormogen cells. All three auxiliary cells exhibit many features of secretory and transport cells but extend only thin basal processes towards the haemolymph sinus. The bauplan and fine structure of coeloconic sensilla differs in the following aspects: (1) the ciliary segment of the dendrites is located deeper below the base of the cuticular apparatus than in the other sensillum types; (2) a prominent dendrite sheath is always present, separating inner and outer sensillum-lymph spaces completely; (3) the apical microlamellae of the auxiliary cells are more elaborate, but free sensillum-lymph spaces are almost absent; (4) there are always four not three auxiliary cells. Morphometric data are presented on the diameter of inner and outer dendritic segments and on the size of receptor cells, as well as of the receptor and auxiliary cell nuclei. The special fine structural features of Drosophila olfactory sensilla are discussed under the aspects of sensillar function and the localization of proteins relevant for stimulus transduction.     

Fine structure and molting of aesthetasc sense organs on the antennules of the isopod,Asellus aquaticus (Crustacea)

In Asellus aquaticus certain distal antennular segments bear single sensilla referred to as aesthetascs. These show a proximal stem and a distal bulbous region. Depending on its position, each aesthetasc is innervated by either 50-60 or 70-80 bipolar sensory cells, the perikarya of which are situated within the pedunculus. Within the antennular segment the dendrites develop unbranched cilia (9 X 2 + 0 structure). The sensory cells are unusual in that mono- as well as biciliary dendrites are present within a single aesthetasc, the ratio of both types being correlated with the number of sensory cells. Cilia and receptor lymph cavity are enveloped by a set of 3-4 inner and 13-14 outer sheath cells, which terminate at the base of the sensillum, so that the delicate and poreless cuticle of the bulbous region encloses only outer segments within the receptor lymph fluid. A new molting type in arthropods is described in which the outer sheath cells alone build the new cuticle, whereas the inner sheath cells most probably have a protective function. A definition of aesthetascs is proposed based on fine-structural criteria. Functionally the sensilla are considered to be chemoreceptors. This assumption is confirmed by experiments with diluted vital dye as well as lanthanum showing that dissolved substances penetrate the poreless cuticle instantaneously.     

Are the most numerous sensilla of terrestrial isopods hygroreceptors? Ultrastructure of the dorsal tricorn sensilla of Porcellio scaber

The ultrastructure of the tricorn sensilla of the woodlouse Porcellio scaber was investigated in cryofixed and freeze-substituted, or chemically fixed specimens. The tricorn sensilla have a foramenized triangular-shaped outer hair and bear a poreless rod-like inner hair. The conical base of the inner hair is connected to the base of the outer hair by a complex cuticular structure. Each sensillum contains three sensory cells. The tip of one of the three dendrites contains a tubular body and is clamped between two bulges of the dendritic sheath. The two other dendrites protrude to the tip of the inner hair, flush against the cuticular wall. The microtubules in the ciliary segments are arranged in nine double tubuli that have neither osmiophilic cores nor arms. The ciliary rootlets are small. The inner segment of the largest dendrite wraps around the two smaller dendrites and one of seven enveloping cells in a mesaxon-like manner. Although this ultrastructure deviates considerably from most crustacean mechanosensitive sensilla, it nevertheless suggests a mechanosensitive function, at least for one of the sensory cells. In many aspects, the tricorn sensilla resemble the thermohygrosensilla of insects. However, our results suggest that the structural criteria for thermo-hygro-sensitivity used in insects cannot simply be applied to crustaceans.     

Ultrastructure and ontogeny of the hair sensilla on the funicle of Calliphora erythrocephala (Insecta,Diptera)

Summary Four envelope cells are responsible for the formation of the basiconical sensilla of Calliphora. They are the thecogen, trichogen, and tormogen cells, and envelope cell 4. In early stages of development the still subepithelial sensory cilia are completely enclosed by the innermost thecogen cell. The first formation movements are initiated by a growth thrust of the hair-forming cell into the exuvial space. The sensory cilia only begin to grow into the hair anlage when the hair-forming cell has almost reached its final length. As soon as growth is completed the trichogen cell, tormogen cell, and envelope cell 4 start to excrete cuticular material. The trichogen cell forms the perforated part of the hair shaft and the stimulus-conducting system consisting of the pore tubules. The tormogen cell is responsible for the excretion of the basal non-perforated hair shaft and sheath cell 4 forms the proximal part of the socket region. The thecogen cell only begin to produce dendritic sheath material when the sensory hair is almost complete.Approximately 7–8 days after pupation the tormogen cell degenerates, having, by this time, produced about two-thirds of the sensilla cuticle. The surrounding envelope cells incorporate cell fragments of the tormogen cell. The trichogen cell continues the secretion where the tormogen cell left off. When the secretion of cuticle is finished the sheath cells begin to withdraw towards the proximal direction and to form microvilli on the apical membrane. The resulting outer receptor lymph space is bordered by envelope cell 4 and the trichogen and thecogen cells. The tormogen cell is absent in the sensilla of the imago.Abbreviations DS dendritic sheath - E4 envelope cell 4 - Ex exuvial space - G glial cell - iD inner dendritic segment - iRL inner receptor lymph space - oRL outer receptor lymph space - oD outer dendritic segment - P pore - PT pore tubules - S sensory cell - T thecogen cell - TO tormogen cell - TR trichogen cell Part 1 of a dissertation accepted by the Faculty of Bio- and Geosciences, University of Karlsruhe     

Development of antennal sensilla during moulting inNeomysis integer (Leach) (Crustacea,Mysidacea)

Summary The sensilla are associated with 6 enveloping cells. The innermost enveloping cell (e 1) secretes the dendritic sheath (=thecogen cell). All other enveloping cells are involved in the formation of the outer cuticular apparatus in secreting the cuticle of a definite region of the new hair shaft.The development of the new sensilla begins when an exuvial space expands between old cuticle and epithelium. The newly forming hair shafts lie folded back in an invagination of the epidermal tissue. Only a distal shaft part projects into the free exuvial space. The cuticle of the distal and middle shaft region is secreted by the three middle enveloping cells (e 2–e 4) (=trichogen cells), which are arranged around the dendritic sheath.The wall of the cylinder, in which the distal shaft is situated, is formed by the cuticle of the future proximal shaft region. It is secreted by the outer enveloping cells (e 5 and e 6). Furthermore, both enveloping cells form the hair socket (=trichogen-tormogen cells).The outer dendritic segments encased within a dendritic sheath run up through the newly formed hair shaft and continue to the old cuticular apparatus. The connection between sensory cells and old hair shaft is maintained until ecdysis. On ecdysis the old cuticle is shed and the newly formed shaft of the sensillum is everted like the invaginated finger of a glove. The dendritic sheath and the outer dendritic segments break off at the tip of the new hair shaft. Morphologically this moulting process ensures that the sensitivity of the receptors is maintained until ecdysis.The internal organization of the sensory cells shows no striking changes during the moulting cycle. An increased number of vesicles is accumulated distally within the inner dendritic segments and distributed throughout the outer segments of the dendrites. The cytoplasmic feature of the enveloping cells indicates that synthesis and release of substances for the cuticular apparatus of the new sensillum take place.     

Morphogenesis of the antenna of the male silkmoth. Antheraea polyphemus, III. Development of olfactory sensilla and the properties of hair-forming cells

During adult development of the male silkmoth Antheraea polyphemus, the anlagen of olfactory sensilla arise within the first 2 days post-apolysis in the antennal epidermis (stage 1-3). Approximately on the second day, the primary dendrites as well as the axons grow out from the sensory neurons (stage 4). The trichogen cells start to grow apical processes approximately on the third day, and these hair-forming 'sprouts' reach their definite length around the ninth day (stages 5-6). Then the secretion of cuticle begins, the cuticulin layer having formed on day 10 (stage 7a). The primary dendrites are shed, the inner dendritic segments as well as the thecogen cells retract from the prospective hair bases, and the inner tormogen cells degenerate around days 10/11 (stage 7b). The hair shafts of the basiconic sensilla are completed around days 12/13 (stage 7c), and those of the trichoid sensilla around days 14/15 (stage 7d). The trichogen sprouts retract from the hairs after having finished cuticle formation, and the outer dendritic segments grow out into the hairs: in the basiconic sensilla directly through, and in the trichoid sensilla alongside, the sprouts. The trichogen sprouts contain numerous parallel-running microtubules. Besides their cytoskeletal function, these are most probably involved in the transport of membrane vesicles. During the phase of cuticle deposition, large numbers of vesicles are transported anterogradely from the cell bodies into the sprouts, where they fuse with the apical cell membrane and release their electron-dense contents (most probably cuticle precursors) to the outside. As the cuticle grows in thickness, the surface area of the sprouts is reduced by endocytosis of coated vesicles. When finally the sprouts retract from the completed hairs, the number of endocytotic vesicles is further increased and numerous membrane cisterns seem to be transported retrogradely along the microtubules to the cell bodies. Here the membrane material will most probably be used again in the formation of the sensillum lymph cavities. Thus, the trichogen cells are characterized by an intensive membrane recycling. The sensillum lymph cavities develop between days 16-20 (stage 8), mainly via apical invaginations of the trichogen cells. The imago emerges on day 21.     

Die digitiformen Sensillen auf dem Maxillarpalpus von Coleoptera

Summary The digitiform sensilla on the distal segment of the maxillar palps ofAgabus bipustulatus (L.) andHydrobius fuscipes (L.) were investigated by electron microscopic methods. Each sensillum is innervated by a single bipolar sensory cell. The sensilla ofHydrobius are associated with three enveloping cells, which enclose an inner and outer receptor lymph cavity. A single enveloping cell only is found in the completely differentiated sensilla ofAgabus. These sensilla do not form an outer lymph cavity. The area beneath the hair base is filled by the distal process of the enveloping cell and by extensions of epidermal cells. Only one extra-cellular space exists, which seems to be homologous to an inner receptor lymph cavity.The outer dendritic segment surrounded by a dendritic sheath runs to the tip of the hair shaft. In the hair shaft the outer dendritic segment divides into several branches. The poreless hair shaft does not rise over the surface of the cuticle, but it is positioned in a narrow shallow groove. Special socket structures or a tubular body do not exist. The digiti-form sensilla possess neither the typical feature of mechanosensitive, nor gustatory or olfactory sensilla. The functional significance of the structural divergences in the sensilla of both species and the presumed function of the sensilla are discussed referring to hygro- and thermo-receptors.

Unserem verehrten Lehrer, Herrn Prof. Dr. H.Risler, dem wir für vielfache Förderung danken möchten, zum 65. Geburtstag gewidmet.     

The fine structure of thermo-/hygrosensitive sensilla in the silkmoth Bombyx mori: Receptor membrane substructure and sensory cell contacts

Summary The thermo-/hygroreceptive sensilla styloconica of the silkmoth Bombyx mori are located on the tips of the antennal branches. A small poreless cuticular peg is innervated by three sensory cells. The outer dendritic segments of two type-1 receptor cells, the presumed hygroreceptors, almost completely fill the peg lumen and are in close contact with each other. The outer dendritic segment of the third (type-2) receptor cell, the presumed thermoreceptor, forms lamellae below the peg base. The membranes of these lamellae are studded with knobs in orthogonal array, protruding into the extracellular space with the same orientation on facing lamellae. This Bossy Orthogonal Surface Substructure (BOSS) is assumed to play a role in thermoreceptor function. Contacts are observed between the outer dendritic segments, between the inner dendritic segments immediately below the ciliary segments, and between the sensory cell somata. These contacts, which are not found in the olfactory sensilla (s. trichodea and basiconica) of this species, indicate electrical interactions between the three sensory cells of the styloconic sensillum and possibly are involved in the antagonistic and/or bimodal response characteristics of thermo-/hygroreceptor cells.     

Fine structure of the galeal styloconic sensilla of larval Lymantria dispar (Lepidoptera: Lymantriidae)

Lepidopteran larvae possess two pairs of styloconic sensilla located on the maxillary galea. These sensilla, namely the lateral and medial styloconic sensilla, are each comprised of a smaller cone, which is inserted into a style. They are thought to play an important role in host-plant selection and are the main organs involved in feeding. Ultrastructural examination of these sensilla of fifth instar Lymantria dispar (L.) larvae reveal that they are each approximately 70 um in length and 30 um in width. Each sensillum consists of a single sensory peg inserted into the socket of a large style. Each peg bears a slightly subapical terminal pore averaging 317 nm in lateral and 179 nm in medial sensilla. Each sensillum houses five bipolar neurons. The proximal dendritic segment of each neuron gives rise to an unbranched distal dendritic segment. Four of these dendrites terminate near the tip of the sensillum below the pore and bear ultrastructural features consistent with contact chemosensilla. The fifth distal dendrite terminates near the base of the peg and bears ultrastructural features consistent with mechanosensilla. Thus, these sensilla each bear a bimodal chemo-mechanosensory function. The distal dendrites lie within the dendritic channel and are enclosed by a dendritic sheath. The intermediate and outer sheath cells enclose a large sensillar sinus, whereas the smaller ciliary sinus is enclosed by the inner cell. The neurons are ensheathed successively by the inner, intermediate, and outer sheath cells.     

The cercal sensilla of the blowfly Lucilia cuprina. II. Structure of the enveloping cells and the basal regions of the sensory dendrites

The gustatory, olfactory, touch and stress receptors on the cerci of Lucilia cuprina Wied. (Diptera: Calliphoridae) have either two or three enveloping cells. The gustatory and olfactory sensilla have three enveloping cells: a tormogen, trichogen and thecogen cell. The tormogen and trichogen cells contribute to a sub-cuticular sensillar lumen which divides into two lobes basally. The thecogen cell forms a lumen around the dendrites. Distally the dendrites lie in the contents of the thecogen lumen within the dendritic sheath. Proximally the dendrites embed in the thecogen cell which has an expanded, microlamellate lumen basally. The sensillar lumen of the mechanosensory (trichoid mechanoreceptors and campaniform) sensilla is formed by a single enveloping cell: the presumptive tormogen cell. In trichoid mechanoreceptors the thecogen lumen is restricted to the region of the transitional region of the dendrite whereas the thecogen lumen of campaniform sensilla extends proximally although it is not as well-developed as that of the chemoreceptive sensilla. The dendrites of all sensillum types on the cerci have a granular body in the transitional region: a situation which has not been previously reported in chemoreceptive sensilla although common in the mechanoreceptors of Calliphoridae and Sarcophagidae.     

The chemosensilla on tarsi of Locusta migratoria (Orthoptera: Acrididae): Distribution,ultrastructure, expression of chemosensory proteins

The chemosensilla on the tarsi of Locusta migratoria were mapped using light microscopy, as well as scanning and transmission electron microscopy. Only chemosensilla chaetica were found on the tarsi. On the basis of their ultrastructure, these can be grouped into three main subtypes: short, long, and sunken sensilla chaetica. Short sensilla chaetica can be further divided into two groups containing 6 or 7 neurons. Long sensilla chaetica are mainly located on the lateral surface of the tarsi. Short sensilla chaetica were mainly found on the dorsal surface of the tarsi. Sunken sensilla chaetica were only found on the ventral surface, such as the pulvilli and arolium. Immunocytochemical localization of chemosensory protein (CSP) was performed on ultrathin sections of chemosensilla on tarsi. The antiserum against LmigCSP‐II intensively labeled all three types of sensilla chaetica. Gold granules were concentrated in the outer sensillum lymph surrounding the dendrite sheath, while the inner sensillum lymph containing dendrite branches was never labeled. Massive labeling with the anti‐LmigCSP‐II was also found in cuticle of the pulvilli on the ventral surface of tarsi. J. Morphol. 2009. © 2009 Wiley‐Liss, Inc.     

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.     

The quill mite <Emphasis Type="Italic">Syringophilopsis fringilla</Emphasis> (Fritsch) (Acari: Trombidiformes: Syringophilidae): the structure of sensory organs providing feeding of the parasite in the feather quill

The structure of the sensory organs situated on palps and chelicerae of the quill mite Syringophilopsis fringilla (Fritsch, 1958) was examined with the use of scanning and transmitting electron microscopy. The tarsal segment of the palps bears 8 sensilla of three types: two contact chemo-mechanoreceptor sensilla, a single chemoreceptor (olfactory) sensillum, and five tactile mechanoreceptor sensilla. All other sensilla situated on basal palpal segments and on cheliceral stylets are represented exclusively by tactile mechanoreceptors. A proprioceptor sensillum was revealed in the movable digit of chelicerae; the modified cilia of dendrites of 5 sensory neurons of this sensillum run inside the inner non-sclerotized core of the stylet and end at different levels in its apical part, attaching to electron-dense rods connected with a sclerotized sheath of the stylet. The authors assume that the proprioceptor sensillum of the stylet detects the strength of the pressure of the stylet of the movable digit on the quill wall during its piercing, and palpal sensilla determine the optimal place for this process.