Sensilla Squamiformia Research Articles

Sensilla on the Antennal Funiculus of the Maize Weevil, Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae): A Morphological Investigation

Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae) has a great capacity to destroy stored grain worldwide. We report on the sensilla on the antennal funiculus of S. zeamais, using classical anatomical methods and scanning electron microscopy to obtain a detailed database of the antennal sensilla for each sex. The antenna is composed of eight antennomeres. Average antennal length is 781.58±20.64 µm for males and 808.91±11.80 µmfor females. Six types and subtypes of sensilla were identified on the funiculus: squamiform, basiconic (2 subtypes), chaetic (2 subtypes), and coeloconic. Sensilla squamiformia are distributed evenly but in few numbers on male and female antennomeres. Sensilla basiconica can be divided into subtypes, SB1 and SB2, according to the shape of the cone. Both subtypes occur on the last antennomere of the flagellum and there are fewer SB2 than SB1. Sensilla chaetica appear in the same position as sensilla basiconica and have two subtypes, SC1 and SC2. Significant differences were not found in the types of sensilla on the antennae of the two sexes, but a difference was found in the number of sensilla.

Ultrastructure observations on antennal sensilla of Heortia vitessoides the most serious pest of Aquilaria sinensis

Heortia vitessoides is the most serious pest of Aquilaria sinensis,which is an economically important evergreen tree native to China and is the principal source of Chinese agarwood. In severe infestations,the insects completely eat up the leaves of A. sinensis,causing severe economic losses. In a more recent study,we found that the antennal sensilla of adult play important roles in the host location,mating and oviposition of H. vitessoides. Here,the external morphology of the antennal sensilla of H. vitessoides were examined using scanning electron microscopy. The result showed that the antennae of both sexes of H. vitessoides were filiform in shape,which consist of the scape,pedicel and about 64 segments of flagellomeres. Eight morphological sensilla types were recorded in both sexes,including sensilla trichodea,sensilla chaetica,sensilla basiconica,sensilla coeloconica,sensilla styloconica,sensilla auricillica,sensilla squamiformia and böhm bristle. Major differences were recorded in the distribution and quantity of different sensilla types in each segment of antenna. The sensillas are almost confined to the ventral and lateral surfaces rather than the back side of antennae. Antennal flagella contained the most sensilla while the scape and pedicel segments only contained böhm bristles and sensilla squamiformias. Sensilla trichodea Ⅲ were only found on male antennae. These results are discussed in relation to the possible roles of the sensilla types in the host location,mating and oviposition selection behavior of H. vitessoides.

A New Type of Mythimna Separata (Lepidoptera: Noctuidae) Antennal Sensilla

ABSTRACT: The Oriental armyworm, Mythimna separata Walker (Lepidoptera: Noctuidae), is a major polyphagous pest with a wide range of hosts in Asia and Oceania. Scanning electron microscopy was used to further elucidate the function of the antennal sensilla and their type, number, and distribution in M. separata. The antenna of M. separata is filamentous. On each three-segmented antenna, from the basal scape, there is a pedicel and a flagellum composed of 70–80 subsegments. Eight morphologically distinct types of sensilla were found on the antennae, including sensilla trichodea, two types of sensilla chaetica, sensilla basiconica, sensilla styloconica, sensilla coeloconica, sensilla squamiformia, sensilla auricillica and Bohm bristles. Sensilla auricillica were found on the antennae of both sexes of M. separata for the first time. The sensilla auricillica in females were located on flagella F23–F44, while they were located on flagella F5–F80 in males.

Structure and distribution of the sensilla on the antennae of Tuta absoluta (Lepidoptera: Gelechiidae)

The tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae), is a widespread devastating pest that develops on tomato and other economically important solanaceous crops. Current semiochemically-based management strategies still fail to significantly reduce damages and need to be improved. Here we describe under scanning and transmission electron microscopy the structure and distribution of the sensilla that are displayed on adult antennae. These were similar in size between males (3424.4±135.3μm) and females (3292.1±111.5μm), being segmented into a scape, a pedicel, and a distal filiform flagellum. Eight morphological sensilla types were observed on both sexes: Böhm’s bristles, sensilla squamiformia, sensilla trichodea, sensilla basiconica (two subtypes), sensilla chaetica, sensilla coeloconica, sensilla auricillica, and sensilla styloconica. The main sexual dimorphism was related to the higher abundance of sensilla trichodea in males, twice as abundant as in females. The putative functional significance of the different sensilla types regarding the insect ecology is discussed based on the available literature. This work provides descriptions of the antennae and related sensory structures. We expect these results to help develop further electrophysiological investigations aiming to a better understanding of T. absoluta olfaction.

Ultrastructure of sensilla of antennae and ovipositor of Sitotroga cerealella (Lepidoptera: Gelechiidae), and location of female sex pheromone gland

The Angoumois grain moth, Sitotroga cerealella, is a serious pest of stored grains worldwide. Presently, the best effective control against the moth is to disrupt the sexual communication between sexes. Sexual communication in moths includes two processes in which females produce and release pheromones from the sex pheromone gland and males detect and respond to them with a relatively sophisticated olfactory system in their antennae. To better understand these processes, we studied the ultrastructure of antennal and ovipositor sensilla of S. cerealella and determined the location of the female sex pheromone gland. Seven types of antennal sensilla were identified on both sexes: sensilla trichodea, sensilla chaetica, sensilla coeloconica, sensilla styloconica, sensilla auricillica, sensilla squamiformia and Bӧhm bristles. Of these sensilla, the sensilla trichodea were significantly more abundant on male antennae than on those of females, suggesting that these sensilla may detect the sex pheromones. On the ovipositor, only sensilla chaetica of various lengths were found. The sexual gland was an eversible sac of glandular epithelium that was situated dorsally in the intersegmental membrane between the 8th and 9th abdominal segments. These results will lead to a better understanding of mate finding with sex pheromones for this worldwide pest species.

Ultrastructure of Chemosensilla on Antennae and Tarsi ofEctropis obliqua(Lepidoptera: Geometridae)

Tea geometrid Ectropis obliqua Prout (Lepidoptera: Geometridae) is a devastating defoliator throughout the tea plantations in China. To explore the putative functions of chemosensilla involved in host selection, the morphology and ultrastructure of antennal and tarsal sensilla in E. obliqua moths were visualized by scanning and transmission electron microscopy. Eight types (including 15 subtypes) of sensilla were identified. On antennae, sensilla trichodea (STR I and STR II) were the most abundant sensillum type characterized by porous cuticle and dendrites in the sensillum lymph. Sensilla chaetica (SCH I–SCH III) possessed a terminal pore and thick nonporous wall, with dendrites in the inner lymph cavity. Three subtypes of sensilla basiconica (SBA I–SBA III) and one type of sensilla auricillica were equipped with thin porous cuticular walls and multiple dendrites in the lymph. Sensilla styloconica were equipped with two or three dendrites that lacked cuticular pores. Sensilla coeloconica possessed four to seven dendrites and were double walled with spoke channels. Böhm bristles and sensilla squamiformia were also observed on the antennae. On tarsi, two subtypes of sensilla chaetica (SCH IV and SCH V) comprised the majority of chemosensilla, and are believed to function in gustatory perception. We summarize the validated functions of related sensilla, and propose potential functions of the corresponding sensilla in E. obliqua . These findings provide a working basis for investigating sensillum function and sensory mechanisms in this pest species.

Insight Into the Ultrastructure of Antennal Sensilla of Mythimna separata (Lepidoptera: Noctuidae).

The oriental armyworm, Mythimna separata (Walk), is one of the most serious pests of cereals in Asia and Australasia. The structure and distribution of the antennal sensilla of M. separata were studied by scanning electron microscopy and transmission electron microscopy. The results showed that antennae of both female and male M. separata are filiform in shape. Three groups and seven morphological sensillum types were recorded in both sexes, including uniporous sensilla (sensilla chaetica), multiporous sensilla (sensilla trichodea, basiconica, coeloconica, and styloconica), and aporous sensilla (sensilla squamiformia and Böhm bristles). S. trichodea, which were the most abundant sensilla, was made of three subtypes (ST I, ST II, and ST III) according to external features and two subtypes of s. basiconica (SB I and SB II) and s. coeloconica (SCo I and SCo II) were identified, respectively. Sexual dimorphisms in sensilla of M. separata were mainly perceived as the variations in the numbers of several sensilla subtypes. Also, the possible functions of the antennal sensilla were discussed. These results contribute to our understanding of the function of antennae in the behavior of M. separata.

Structure and distribution of antennal sensilla in the Indianmeal moth, Plodia interpunctella (Hübner, 1813) (Lepidoptera: Pyralidae)

The Indianmeal moth, Plodia interpunctella, is an important primary pest of stored products worldwide. To better understand the chemical orientation of this insect towards its host products, we determined the structure and distribution of antennal sensilla of P. interpunctella by light and scanning electron microscopy (SEM). The results show that the antenna is filiform and made of three parts, a scape, a pedicel, and a flagellum. The female antenna was found slightly longer (5.20 ± 0.37 mm) than the male antenna (4.37 ± 0.23 mm). In both sexes, eight main types of sensilla were observed: Böhm bristles, sensilla basiconica, sensilla chaetica, sensilla coeloconica, sensilla styloconica, sensilla auricillica, sensilla squamiformia, and sensilla trichodea. The latter type was made of three subtypes according to their length: short sensilla trichodea, medium sensilla trichodea, and long sensilla trichodea. The sexual dimorphism in the antenna of P. interpunctella was mainly perceived as a variation in flagella length and sensilla distribution and size. External structure and distribution of these sensilla are compared to those of other pyralids and possible functions of the antennal sensilla are discussed.

Ultrastructure of antennal sensilla of four skipper butterflies in Parnara sp. and Pelopidas sp. (Lepidoptera, Hesperiidae).

Most species of Parnara and Pelopidas (Hesperiidae) are important pests of rice. In this study, the antennal morphology, types of sensilla, and their distribution of four skipper butterflies, including Parnara guttata (Bremer & Grey), Pa. bada (Moore), Pelopidas mathias (Fabricius) and Pe. agna (Moore), were observed using a scanning electron microscope. Six distinct morphological types of sensilla were found on the antennae of all of these species: sensilla squamiformia, sensilla trichodea, sensilla chaetica, sensilla auricillica, sensilla coeloconica, and Böhm sensilla. The sensilla trichodea are the most abundant sensilla among the four skipper butterflies, and the sensilla auricillica are confirmed on the antennae of butterflies for the second time. In addition, the possible functions of these sensilla are discussed in the light of previously reported lepidopteran insects, which may provide useful information for further study of the function of these antennal sensilla and for related pests control by applying sex pheromones.

Antennal Morphology and Sensilla of the Black-Back Prominent Moth,Clostera anastomosisLinnaeus (Lepidoptera: Notodontidae)1

ABSTRACT We observed the antennal morphology and sensilla of the black-back prominent moth, C. anastomosis, by scanning electron microscopy (SEM). Antennae of both sexes of C. anastomosis are bipectinate, feather-like in shape, consisting of two basal segments, scape and pedicel, followed by a long distal flagellum with more than 30 segments, each having a pair of lateral branches. Twelve major sensillar types were identified: two types of sensilla trichodea (ST), two types of sensilla chaetica (SCh), three types of sensilla squamiformia (SSq), two types of sensilla basiconica (SB), two types of Bohm bristles (BB), sensilla coeloconica (SCo), sensilla auricillica (SA), sensilla styloconica (SSt), sensilla cavitata-peg (SCP), sensilla gemmiformia(SG), sensilla basiconic-mastoid (SBM) and sensilla cylindrica (CY). Sensilla cylindrica and sensilla gemmiformia only exist on female antennae, while sensilla basiconic-mastoid are only on male antennae. The morphology, number and distribution of various sensilla ...

Sensilla on the antennae, legs and ovipositor of Spathius agrili Yang (Hymenoptera: Braconidae), a parasitoid of the emerald ash borer Agrilus planipennis Fairmaire (Coleoptera: Buprestidae)

To investigate the host-finding mechanisms of Spathius agrili Yang, a parasitoid of the emerald ash borer, Agrilus planipennis Fairmaire, a highly concealed insect pest of Fraxinus spp. The morphology and ultrastructure of sensilla on the antennae and legs of both sexes and on the ovipositors and ovipositor sheaths of females were observed using SEM. Results showed that abundant sensilla trichodea (ST) are distributed on the antennae of both females and males, with the sharp trichoid with a socket at the base being the most numerous sensillum. There are 6-7 sensilla placodea on each segment of the flagellum, arranged lengthways in parallel rows. There are very few sensilla styloconica on the female antennae. The tibiae have mostly sensilla chaetica, whereas three types of ST and the relatively plentiful sensilla chaetica are present on the tarsi. Besides ST, a mass of sensilla squamiformia and small short spines are distributed on the pulvilli. Basically there are no sensilla on the female ovipositor, only steering mechanisms for drilling bark and a variety of v-shaped grooves. However, a large numbers of short sensilla chaetica and microtrichia are found on the internal surface of ovipositor sheath. The outer surface of the ovipositor sheath also has ST. In addition, a clear spring-like extension structure can be observed on the fore parts of ovipositor sheath. These findings suggest that the main function of sensilla on the antennae is olfaction, while the sensilla on legs and ovipositor sheaths are mechanoreceptors and tactile sensors.

Ultrastructural observations on antennal sensilla of Coleophora obducta (Meyrick) (Lepidoptera: Coleophoridae)

Coleophora obducta (Meyrick) is an important defoliator of larch in northeast China. To further describe the mechanism of insect-plant chemical communication, we observed the antennae and their sensilla of C. obducta by scanning and transmission electron microscopy. In both sexes, antennae were threadlike, and in total there were eight types of sensilla found on the antennae: Sensilla placodea, Sensilla basiconica, Sensilla coeloconica, Sensilla styloconica, Sensilla trichodea, Sensilla squamiformia, Sensilla furcatea and Böhm bristles, respectively. We described ultrastructures and discussed possible functions. We inferred from their ultrastructures as chemoreceptors that S. placodea, S. basiconica and S. trichodea were innervated by sensory neurons. The neuron of S. styloconica terminated in a tubular structure which suggested gustatory/mechanosensory function, and the terminal sensory pegs might function as contact-chemoreceptors depending on their locations.

Distribution of chemo‐ and mechanoreceptors on the tarsi and ovipositor of female European grapevine moth, Lobesia botrana

AbstractWe describe the number, distribution, and function of sensilla located on different organs of Lobesia botrana (Lepidoptera: Tortricidae) females using scanning electron microscopy, selective staining, and contact electrophysiology. The tarsi of the prothoracic legs bear contact chemo‐mechanoreceptor sensilla chaetica (5–13 per tarsomere), arranged in rings mainly concentrated on ventral surfaces, and different mechanosensory structures (sensilla chaetica, sensilla squamiformia, sensilla campaniformia, and spines). A single contact chemo‐mechanoreceptor sensillum chaeticum is present between the claws on the pretarsus. The ventral surface of the ovipositor lobes is covered with numerous mechanosensory sensilla chaetica of different types, out of which 10 have a contact chemosensory function. Putative contact chemo‐mechanoreceptor sensilla were also observed on the proboscis and antenna. Longitudinal rows of alternated sensilla styloconica and basiconica are present on the distal part of the proboscis, and rings of sensilla chaetica are present at the antennal tip. The sensilla on these body parts may play different roles in the selection of an oviposition site.

An investigation of the surface of the cuticle and associated sensory structures of the terrestrial isopod, Porcellio scaber

The exoskeletal surface of the body of the terrestrial isopod, Porcellio scaber has been examined with the scanning electron microscope as part of a study of the structural changes associated with the transition from sea to land in the Isopoda. No sexual differences are apparent. The dorsal cuticular surface is characterized by large tubercles, minute plaques and pits, separated by amorphous areas. Apart from the eyes the only structures of apparent sensory function are relatively large setae which occur near the antero‐lateral and posterolateral edges of each epimeron, and sensilla squamiformia (tricorns). Tricorns are extremely numerous on the dorsal surface and appear to be formed from the fusion of a plaque and a sensillum which arises from a pit. Much of the ventral body surface is covered with closely‐set plaques, tricorns being restricted to the epimera. Along the sides of the mid‐ventral sternal groove occur numerous small tubercles each surmounted by a single seta. Similar, though smaller structures are found in a single row along the outer edge of the epimera. The water capillary system of this species is formed from spines which arise from plaques around the pereopodal sockets and along the junctions between the epimera and sternites. Most of the sensilla described appear to be mechanosensory and are probably associated with the thigmokinetic and proprioceptive responses of the woodlouse.