3rd Antennal Segment Research Articles

Characterization of Antennal Sensilla and Immunolocalization of Odorant-Binding Proteins on Spotted Alfalfa Aphid, Therioaphis trifolii (Monell).

The spotted alfalfa aphid [Therioaphis trifolii (Monell), Homoptera, Drepanosiphidae] is a well-known destructive pest that can significantly reduce alfalfa yields. Herein, the morphology of antennal sensilla of T. trifolii has been examined by using scanning electron microscopy and the ultrastructure of sensilla stellate and placoidea was described by transmission electron microscopy. Stellate sensilla, placoid sensilla, and coeloconic sensilla were found on the 6th segment, and a single sensillum placoidea was located on the 5th segment. Placoid sensilla were also present on the 3rd antennal segment of alate and apterous aphids, and the number was similar between two morphs. Two types of trichoid sensilla and coeloconic sensilla were found on the antennae, respectively. The results of ultrastructure showed that stellate sensilla are innervated by three neurons, while placoid sensilla present three groups of neurons, equipped with 2–3 dendrites in each neuron group. Immunocytochemical localization of odorant-binding proteins (OBPs) was performed on ultrathin sections of sensilla stellate and placoidea, and we observed that the antiserum against OBP6 intensively labeled all placoid sensilla from both primary and secondary rhinaria. OBP7 and OBP8 could also be detected in placoid sensilla, but less strongly than OBP6. In addition, OBP6, OBP7, and OBP8 were densely labeled in stellate sensilla, suggesting OBP6, OBP7, and OBP8 may sense alarm pheromone germacrene A in T. trifolii.

New species of the aphid tribe Macrosiphini (Homoptera, Aphididae, Aphidinae) from Kazakhstan

Two new species of the genera Uroleucon Mordvilko, 1914 and Pleotrichophorus Borner, 1930 are described from Kazakhstan. Uroleucon dzhungaricum sp. n. feeding on Senecio nemorensis L. (Asteraceae) in the Dzhungar Ala Tau is closely related to U. minor (Borner, 1940). Both these species differ from the closely related U. solidaginis (Fabricius, 1794) in a smaller length ratio between the processus terminalis and the 3rd antennal segment (0.8–1.0 versus 1.0–1.5). The new species differs from U. minor (Born.) in a greater number of the secondary rhinaria on the 3rd antennal segment of the apterous viviparous females (21–37 versus 15–21), in a fewer number of hairs on the cauda (10–16 and 15–23), and in the host plant. Pleotrichophorus ugamicus Kadyrbekov, sp. n. feeding on Artemisia santolinifolia Turcz. is described from the Sairam-Ugam Natural Park (Southern Kazakhstan). The new species is similar to P. glandulosus (Kaltenbach, 1846) and P. achilleae Holman, 1965. Pleotrichophorus ugamicus sp. n. differs from these species in the length ratio of the processus terminalis to the base of the 6th antennal segment (4.1–5.0 versus 5.0–9.0 and 5.1–6.2), in that of the ultimate rostral segment to the 2nd segment of the hind tarsus (0.68–0.76 versus 0.80–0.97 and 0.80–0.90), and in the host plant. This species differs from P. glandulosus in the ratio of the length of dorsal hairs on tergites I–V to the basal diameter of the 3rd antennal segment (1.0–1.2 and 1.4–1.7). In addition, the new species differs from P. achilleae in the length ratio of the 3rd antennal segment to the 6th segment (0.56–0.66 versus 0.70–0.87) and to the processus terminalis (0.67-0.82 versus 1.39–1.80), as well as in the shape of the dorsal hairs. A key to the Palaearctic species of the genus Pleotrichophorus is presented.

New species of the genus Klimaszewskia Szelegiewicz, 1979 (Homoptera, Aphididae) from Kazakhstan

Two new species of the genus Klimaszewskia were described from aphid collections made in 2010–2011 in the “Katon-Karagaiskii” State National Natural Park (the Kazakhstan part of the Altai Mountains). Klimaszewskia altaica Kadyrbekov, sp. n. inhabiting Nepeta sibirica and K. katonica Kadyrbekov, sp. n. inhabiting Dracocephalum grandiflorum differ from the other known species of this genus in a smaller number of hairs on the ultimate rostral segment and on the 2nd segment of the hind tarsus and also in the presence of indistinct, strongly flattened marginal protuberances. They differ in the length ratio between the processus terminalis and the base of the 6th antennal segment (3.6–4.6 in the former, and 4.2–5.2 in the latter species), the siphunculi and the body (0.17–0.24 versus 0.25–0.27), and the cauda and the 2nd segment of the hind tarsus (1.7–2.2 and 2.25–2.35), as well as in the length of hairs on the frons, antennae, and tergites, in the number of hairs on tergite VIII (8–10 and 2–3), and in the number of secondary rhinaria on the 3rd antennal segment (3–12 compared to 0–2). The holotypes and some paratypes of the new species are deposited in the collection of the Institute of Zoology (Almaty, Kazakhstan). Some part of the paratypes is kept in the Zoological Institute of the Russian Academy of Sciences (St. Petersburg, Russia).

Two New species of the dipteran genus Dolichopus Latreille (Diptera, Dolichopodidae) from Siberia and Mongolia

Two new species of the genus Dolichopus Latreille (Diptera, Dolichopodidae) are described from Mongolia and Siberia. Dolichopus tschernovi Negrobov, Barkalov et Selivanova, sp. n. is similar to Dolichopus bayaticus Negrobov, 1976, but differs in the presence of one seta on the hind metatarsus, the shorter 3rd antennal segment, and in the structure of the hypopygium. Dolichopus lenensis Negrobov, Barkalov et Selivanova, sp. n. resembles Dolichopus setitarsis Negrobov et Barkalov, 1977, but differs in the slightly widened 2nd–4th segments of the middle tarsus, in the presence of one seta on the hind metatarsus, and in the structure of the hypopygium. Drawings of the antennae, tarsi, and hypopygium of the new species are given. The holotypes of the new species are deposited in the Zoological Institute, the Russian Academy of Sciences (St. Petersburg).

Immunolocalization of Odorant-Binding Proteins on Antennal Chemosensilla of the Peach Aphid Myzus persicae (Sulzer)

The antennal sensilla of Myzus persicae were mapped using scanning and transmission electron microscopy. Placoid sensilla and coeloconic sensilla were found on the 6th segments, whereas 2 types of trichoid sensilla were present all through the length of the antenna. A single sensillum placoideum was located on the 5th segment, whereas alate aphids also presented placoid sensilla on the 3rd antennal segment. Immunocytochemical localization of odorant-binding proteins (OBPs) was performed on ultrathin sections of antennal chemosensilla. The antiserum against OBP7 intensively labeled all placoid sensilla from both primary and secondary rhinaria, with gold granules concentrated in the lymph surrounding the dendrite. OBP6 and OBP3 could also be detected in placoid sensilla, but less strongly than OBP7. Barely significant reaction or no reaction was observed with antibodies against OBP8.

Morphological variation in Glossina pallidipes Austen (Diptera: Glossina pallidipes Austen (Diptera:Glossinidae) over its geographical range

Morphometric studies were carried out on Glossina pallidipes from Zimbabwe in southern Africa and Uganda in eastern Africa. Ten and seven characters were used in the multivariate discriminant analysis for the male and female populations respectively. All the characters showed highly significant morphological discrimination «0.001) between the two populations. These were further confirmed by the separate scatterplot for each sex population. The consistent discriminant characters between the male and female population are: 2nd and 3rd antennal segment length, head narrowest point width arid eye base to bucca tip length. The most powerful discriminator between the male populations is the 2nd and 3rd antennal segments length whereas in the female populations it is the eye base to bucca tip length. The percentage of “grouped” cases correctly classified for each sex populations was 100 with no overlap. The morphological variations observed between the allopatric populations in relation to biological species concepts are discussed.

External anatomy of adult antennal sensilla of the fly, Trichopoda pennipes F. (Diptera: Tachinidae)

Antennae of both sexes of the feather-legged fly, Trichopoda pennipes F. (Diptera : Tachinidae) are described based on SEM observation. Socketed bristles and microtrichia were found on scape and pedicel, while a large number of different types of sensilla, interpersed with numerous microtrichia, were present on the entire surface of the 3rd antennal segment (funiculus). Seven types of sensilla, at least 3 of them olfactory, were observed and classified on the basis of external anatomical characteristics, such as shape, pore presence and density. A single deep pit, containing groups of sensilla, was present in both sexes on the lateral side of the funiculus.

Structure of superficial chemoreceptive sensilla on the third antennal segment of Ceratitis capitata (Wiedemann) (Diptera : Tephritidae)

The number, distribution, and morphology of the sensilla on the 3rd antennal segment of Ceratitis capitata (Diptera : Tephritidae) were studied with scanning and transmission electron microscopy. Four types of sense organs were identified: basiconic (subtypes I, II and III), clavate, trichoid, and grooved sensilla. Basiconic, clavate, and trichoid sensilla conform to the single-walled, multiporous receptors, having a pore-tubule system. The basiconic and clavate sensilla are thin-walled and their cuticle is penetrated by many small pores uniformly distributed over the surface. The trichoid sensilla are clearly visible in the apical region of the hair. An olfactory function has been proposed for these sensillar types. The grooved sensilla conform to the double-walled sensilla with spokechannels, which extend through the cuticular wall. An olfactory function has also been suggested for this sensillum.

Internal proprioceptive organs of the distal antennal segments in Allacma fusca (L.) (Collembola : Sminthuridae): Proprioceptors phylogenetically derived from sensillum-bound exteroceptors

The internal proprioceptive organs of the distal antennal segments of Allacma fusca (Collembola : Sminthuridae) were examined with light, scanning, and transmission electron microscopy. There are 2 such organs, each belonging to the sensory equipment of a sensory peg. These pegs are part of the sensory organs of the 3rd antennal segment (SO - AIII), and show characteristics of both hair sensilla and chordotonal organs. They have 5 sensory cells of which 4 can be regarded as chemoreceptors, because the walls of the pegs are pierced by pores. The 5th cells are the proprioceptors. Their dendritic outer segments are connected to the base of the SO - AIII peg but show no specializations. Their dendritic inner segments are distally joined to a thecogen cell containing a scolopale. Proximally, they span the hemolymph space within the antenna. The perikaryon of one of the organs is located on a muscle that deflects the 3rd antennal segment (IP - AIII). The perikaryon of the other is attached to the antennal nerve near a point where it is connected to a muscle that deflects the 4th antennal segment (IP - AIV). There is a conspicuous membrane system, associated with microtubules and a prominent ciliary rootlet within the dendritic inner segment of the IP - AIII. The cytological features of the organs are discussed with reference to 2 problems, the phylogeny of chordotonal organs and the process of mechanosensory transduction.

Sensilla on the third antennal segment of Drosophila melanogaster meigen (Diptera : Drosophilidae)

The distribution and morphology of the sensilla on the 3rd antennal segment of Drosophila melanogaster Meigen (Diptera : Drosophilidae) were studied with light and electron microscopy. Four types of hairs were identified. Three types of hairs innervated by dendrites are sensilla basiconica, sensilla coeloconica and sensilla trichodea. They occur amongst a large number of the 4th type of uninnervated hairs or spinules. Sensilla basiconica and coeloconica can be easily identified by light microscopy on staining with 0.1016 silver nitrate in 70% ethanol. The tips of sensilla basiconica and coeloconica appear dark brown. Most of the sensilla trichodea and spinules remain unstained. Sensilla basiconica conform to the single-walled, multiporous sensilla, having poretubules and branched dendrites. Sensilla coeloconica are double-walled and have longitudinal channels near the tip. No wall pores are found on sensilla trichodea. Dendrites do not branch in sensilla coelonica and trichodea. A mechanosensory dendrite with characteristic tubular body is absent in these sensilla. Populations of sensilla basiconica and sensilla trichodea occur in diametrically opposite, distinct regions on the 3rd antennal segment-the former in the dorsomedial and the latter in the ventrolateral regions, whereas sensilla coeloconica are distributed on most of the anterior and posterior surfaces, including the cavity walls of the sacculus. The axons are arranged in distinct groups in the antennal nerves at the stalk of the 3rd segment. This grouping becomes more pronounced in the nerve prior to its entry into the brain.

Geographic Variation in Scatella stagnalis (Diptera: Ephydridae)

A multiple discriminant functions analysis of Scatella stagnalis (Diptera: Ephydridae) from 40 localities in North America showed that only a small portion of the interlocality variation can be accounted for by the geographic positions of the localities. It was hypothesized that the observed variation was due to some combination of local selective pressures and non-selective factors. The data suggest that gene flow is of little importance in this species. Analysis of variance indicated significant interpopulational differences in all 12 characters measured for both males and females, except for the length of the 3rd antennal segment in males. Further analysis showed the females to be larger than the males with respect to all characters. The variational patterns found in males were only partially paralleled in females. This may be a reflection of the varying patterns of sexual dimorphism or it might indicate that males and females are being subjected to somewhat different selective pressures. The analysis indicated that the recognition of geographic races (subspecies) would be inappropriate.

The ‘head’ and ‘body’ races of Pediculus humanus L.

1. Measurements were made of the head length, head width, total body length, antenna length, length and breadth of 3rd antennal segment of head and body lice from natural infestations. In all measurements (except the last) the means were significantly different for. the two forms, but in all cases there was considerable overlap.2. Head lice reared continuously on the body for forty-three generations (over 2 years) did not change systematically in size. Body lice reared under similar conditions were likewise constant.3. There was a highly significant difference between mean measurements of all the samples of head lice reared for up to 2 years on the body when compared with body lice reared for a similar period in the same way. The means for lice worn 24 hr. per day were less than those worn 12 hr. per day in both strains. An experiment showed that this is probably due to a difference in average temperature.4. The mean live weights of head and body strains were even more distinct than linear dimensions on the several occasions when these were recorded.5. Measurements of the dimensions of the opercula of the eggs of the two races and the numbers of air cells in them were distributed in the same way as the body measurements: that is, distinct means but overlapping individuals.6. Ventral abdominal muscles in wild head lice are typically confined to segment 5. (The forty specimens examined adhered to this rule.) In wild body lice, muscles are usually also present in segment 4 as well.7. Hybrids (female body x male head louse) were fertile for several generations. In size, the F1 generation was intermediate, but the F2 and F3 generations became identical with the body louse strain.8. Eggs of the body louse strain hatched at the same time as those of the head strain, but the body strain reached a significantly higher percentage hatch.9. The times of moulting during development were studied in both races in relation to differing opportunities to feed (24, 12, 6 and 3 hr. per day). The two strains showed very similar reactions in regard to speed of development, but throughout there was a higher pre-imaginal mortality in the head strain.10. Head lice were shown to be considerably more susceptible to starvation than body lice.11. If adults of the two strains are mixed, there is no tendency towards homogeneous mating. Of the mixed matings, those between body louse males and head louse females are much more common than the reverse.12. Female head lice show a slight difference in their egg-laying preferences when offered a choice of hair, voile and tape.My thanks are due to Prof. P. A. Buxton, F.R.S., for a number of helpful suggestions based on his extensive knowledge of louse biology and to Dr J. O. Irwin for critical comments on the statistical issues.