The comparative morphology of epidermal glands in Pentatomoidea (Heteroptera)

The Heteroptera show a diversity of glands associated with the epidermis. They have multiple roles including the production of noxious scents. Here, we examine the cellular arrangement and cytoskeletal components of the scent glands of pentatomoid Heteroptera in three families, Pentatomidae (stink bugs), Tessaratomidae, and Scutelleridae (shield-backed bugs or jewel bugs). The glands are; (1) the dorsal abdominal glands, (2) the tubular glands of the composite metathoracic gland, and (3) the accessory gland component of the composite metathoracic gland. The dorsal abdominal glands are at their largest in nymphs and decrease in size in adults. The metathoracic gland is an adult-specific gland unit with a reservoir and multiple types of gland cells. The accessory gland is composed of many unicellular glands concentrated in a sinuous line across the reservoir wall. The lateral tubular gland is composed of two-cell units. The dorsal abdominal glands of nymphs are composed of three-cell units with a prominent cuticular component derived from the saccule cell sitting between the duct and receiving canal. The cuticular components that channel secretion from the microvilli of the secretory cell to the exterior differ in the three gland types. The significance of the numbers of cells comprising gland units is related to the role of cells in regenerating the cuticular components of the glands at moulting in nymphs.     

Dry under water: Comparative morphology and functional aspects of air‐retaining insect surfaces

Superhydrophobic surfaces prevent certain body parts of semiaquatic and aquatic insects from getting wet while submerged in water. The air layer on these surfaces can serve the insects as a physical gill. Using scanning electron microscopy, we investigated the morphology of air‐retaining surfaces in five insect species with different levels of adaptation to aquatic habitats. We found surfaces with either large and sparse hairs (setae), small and dense hairs (microtrichia), or hierarchically structured surfaces with both types of hairs. The structural parameters and air‐film persistence of these surfaces were compared. Air‐film persistence varied between 2 days in the beetle Galerucella nymphaea possessing only sparse setae and more than 120 days in the bugs Notonecta glauca and Ilyocoris cimicoides possessing dense microtrichia (up to 6.6 × 10⁶ microtrichia per millimeter square). From our results, we conclude that the density of the surface structures is the most important factor that affects the persistence of air films. Combinations of setae and microtrichia are not decisive for the overall persistence of the air film but might provide a thick air store for a short time and a thin but mechanically more stable air film for a long time. Thus, we assume that a dense cover of microtrichia acts as a “backup system” preventing wetting of the body surface in case the air–water interface is pressed toward the surface. Our findings might be beneficial for the development of biomimetic surfaces for long‐term air retention and drag reduction under water. In addition, the biological functions of the different air retention capabilities are discussed. J. Morphol., 2011. © 2011 Wiley‐Liss, Inc.     

The metathoracic scent gland system in Hydrocorisae (Heteroptera: Nepomorpha)

Abstract. The metathoracic scent gland system is a basic feature of the order Heteroptera. It occurs widely not only in the terrestrial forms (Geocorisae) and water-surface bugs (Amphibicorisae) but also in the totally aquatic bugs (Hydrocorisae) and their littoral relatives (Ochteridae, Gelastocoridae). In Hydrocorisae the metathoracic scent gland conforms to Carayon's (1971) omphalian type (orifice median and undivided or, if divided, orifices close together towards the mid-ventral line) but shows marked differences in structure and physiological function between species from different families. There is taxonomic interest in the distribution of the three distinctly different types of metathoracic occlusion apparatus. Naucoridae and Belostomatidae have a median lip-valve, Notonectidae and Gelastocoridae a pair of stop-valves, Corixidae a median flap-valve. The valve opener muscles are usually dorso-ventral but are ventral in Corixidae; the cuticular microsculpture in the metathoracic efferent system specifically in Hydrocorisae with stop-valves (Notonectidae, Gelastocoridae) is similar to that widely present in Geocorisae. Groupings of Hydrocorisae from variations in the metathoracic occlusion apparatus differ from others based upon variations in the chemical constitution of the secretions. It is considered that the facts now known on metathoracic scent gland structure and function accord well with the hypothesis that Hydrocorisae constitute a polyphyletic assemblage.     

A Quantitative Analysis of Secretion-Grooming Behaviour in the Water Bug Plea minutissima Leach (Heteroptera,Pleidae): Control by Abiotic Factors

The pigmy backswimmer, Plea minutissima, from time to time leaves the water to apply its antimicrobial metathoracic gland secretion to its water-repellent ventral pubescence (“secretion-grooming”) which is enclosed by an air sheath when submerged and has a respiratory function. Secretion-grooming keeps the hairs free of microbial contamination and thus hydrophobous and functional. The grooming behaviour is regulated by abiotic factors. It is released by an increase in light intensity or water temperature, with a sudden rise in temperature being particularly effective. The higher the temperature and light intensity, the faster the grooming act is performed and completed. The grooming motivation is higher at a higher ambient temperature, but declines once the behaviour has been brought to completion. As a consequence the highest grooming activity in the field is observed in summer on the first sunny day after a prolonged period of overcast days. The tying of secretion-grooming to abiotic factors probably serves to destroy epizoic microorganisms before they begin to multiply more rapidly at higher temperatures. The mechanisms regulating the secretion-grooming behaviour of Plea may be of significance also for the regulation of certain other insect behaviours (e.g., flight behaviour).     

A quantitative analysis of underwater oviposition by the mosquito Mansonia titillans

ABSTRACT. Formation of the rosette-like egg mass of the neotropical mosquito Mansonia titillans Walker is described from video recordings of thirteen females ovipositing on the undersurfaces of water lettuce ( Pistia stratiotes ) leaves in the laboratory. The female abdomen executes symmetrical stroking behaviour to the right and left of centre line. Outstrokes consist solely of scratching, in which spines on the eighth tergite abrade the leaf surface preparatory to oviposition. A row of eggs is glued to the leaf only on instrokes, which are of longer duration than outstrokes, and may be interrupted by scratches and pauses. Scratching precedes oviposition of each of the first four eggs, which are laid without stroking behaviour. The egg mass is enveloped in an air bubble which is transported underwater on the hydrofuge female abdomen. The deposition of eggs on instrokes is homologous to the behaviour used by Culex and Culiseta mosquitoes in the construction of free-floating egg rafts.     

The adult scent glands and scent of nine bugs of the superfamily Coreoidea

In most of the six coreoid genera examined there are differences in the scent gland complex. This comprises a median, ventral, metathoracic reservoir with either one, two, or three pairs of accessory glands.

The nine adult bugs examined all produced a colourless, single-phase scent, the components of which were similar although the relative proportions varied. Either n-hexanal or n-hexyl acetate, or both, were usually the major constituents (about 90 per cent of the total) and n-hexanol and acetic acid were also present in amounts varying from traces to about 10 per cent. In one species n-butanal was detected and in two species n-butyl butyrate and (probably) butyric acid were present.

The characteristic, ester odour of these coreoid bugs is quite unlike that of pentatomid bugs examined so far and the two groups do not possess a single component in common; nevertheless there are interesting analogies between the scent components of both groups.     

Sebum-storing flank gland hairs of the musk shrew, Suncus murinus viridescens

Lipid droplets discharged from the disintegrating holocrine cells of the flank gland of the Indian musk shrew, Suncus murinus viridescens (Blyth) are stored in the lumen of the sebaceous acini and eliminated to the exterior through the glandular ducts. Specialized hairs developed on the surface of the flank gland of the shrew are deep rooted. The osmetrichia of the flank gland of both sexes of the shrew have flattened and thickly packed culicular scales. These scales are morphologically different from the largeconical-shaped scales of the dorsal body hairs. The surface of osmetrichia is soaked with the oily secretory materials of the flank gland. The medulla of osmetrichia is developed into Special chambers which are filled with the glandular secretory droplets.     

Microhabitat selection by the fishfly larva, Parachauliodes japonicus, in relation to its mode of respiration

SUMMARY. 1. Larvae of Parachauliodes japonicus (Megaloptera: Corydalidae) were tracked in streams using miniature radio-transmitters.
2. Larvae usually stayed under stones in shallow water for several days, but occasionally moved about on the stream bed at night.
3. Larvae possess a pair of respiratory tubes on abdominal segment VIII, which can be used as a snorkel to obtain oxygen from the atmosphere. Because respiratory rates decreased as dissolved oxygen decreased, larvae turned to air-breathing under lowered oxygen conditions. When in shallow water, they can alter respiratory mode from aquatic respiration to air breathing instantly by raising their caudal respiratory tubes to the surface of the water.
4. Microhabitat selection and respiratory behaviour are compared with those obtained previously for Protohermes grandis larvae, which belong to the same family and often inhabit the same stream as P. japonicus , but which have gill tufts on abdominal segments I-VII instead of respiratory tubes. The respiratory constraint on microhabitat preference by aquatic insects is discussed.     

Surface properties of Culex pipiens pipiens eggs and the behaviour of the female during egg-raft assembly

ABSTRACT. Eggs of the mosquito Culex pipiens pipiens L. float vertically because a flexible corolla at the anterior (lower) pole has a hydrophilic lower surface and a hydrofuge upper surface. The corolla assumes different configurations in the egg raft; the surface forces operating on eggs are briefly analysed. The outer surface of the chorion is hydrofuge, but in eggs floating on water there is a jacket of water surrounding the egg in the spaces between the tubercles of the exochorion, below the meshwork connecting them. The humidity over natural water can be low enough to cause continuous evaporation from the jacket; water is replenished through openings within the lower surface of the corolla. The disposition of the corolla prevents the uptake of materials confined to the water surface outside, but the mechanism could concentrate solutes in the jacket, with possible deleterious consequences. Eggs are joined together by inter-digitation of the regularly spaced tubercles. The behaviour by which the female assembles the egg raft is described in detail, explaining the form of the raft and the patterns in which eggs are packed.     

Food level reaction norms in size-selected milkweed bugs (Oncopeltus fasciatus)

Abstract. 1. The hypothesis that the small size of nonmigratory milkweed bugs from Puerto Rico (relative to large migratory bugs from Iowa) might be an adaptation to low food levels was tested with bugs selected for large and small size as the consequence of positive genetic correlation between body size and wing length. The test involved examining reaction norms of life history traits to different food levels.
2. When nymphs were reared on 3 milkweed seeds per nymph from hatch to adult eclosion, large bugs were adversely affected with only 50% and 60% in each of two replicates reaching adulthood. Control (unselected) and small bugs, however, were unaffected at this food level. None of the lines was affected at levels of 6 and 12 seeds per nymph.
3. When adults were reared from eclosion on 12, 18 or 24 milkweed seeds per bug, large bugs were adversely affected relative to control and small bugs at all three food levels. At each food level fewer large bugs produced eggs than either small or control bugs which did not differ.
4. The evidence from the food level reaction norms suggests that larger bugs will be selected against during periods of food shortage of the sort likely to occur in Puerto Rico.     

Gripping ease in southern green stink bugs Nezara viridula L. (Heteroptera: Pentatomidae): Coping with geometry,orientation and surface wettability of substrate

The southern green stink bug Nezara viridula L. (Heteroptera, Pentatomidae) is highly polyphagous, preferring apically situated seeds and fruits on more than 150 plant species belonging to over 30 plant families all over the world. This forces them to move over highly variable terrains, including plant stems, leaves, pods and buds, which requires efficient attachment. Stink bugs have long slender legs and feet (tarsi) equipped with paired curved claws, paired soft adhesive pads (pulvilli), and flattened lanceolate hairs (setae), which arise ventrally on the first and second foot segments (tarsomeres). To characterize their attachment abilities on well‐defined test substrates, here we comparatively measured and analyzed the traction forces of bugs walking horizontally and vertically on hydrophilic (water attractive) and hydrophobic (water repellent) glass plates and rods. The latter correspond to the geometry of preferred feeding sites of stink bugs in the field. The results show a clear contribution of tarsal flattened lanceolate hairs to the stink bug's attachment. Higher traction forces are generated on a glass rod than on a glass plate, corresponding to up to individual maximum of 43 times the stink bug's body weight. Substrate hydrophobicity promotes the attachment, while the measured forces are up to eight times lower when tarsal hairs are disabled. The combination of smooth and hairy tarsal pads results in a remarkable attachment ability, which enables N. viridula to climb unstable apical plant parts, and supports their invasive behavior and global dispersion.     

The skin of primates. XLI. The skin of the silver marmoset—Callithrix (= Mico) Argentata

The skin of the silver marmoset, Callithrix (= Mico) argentata Linnaeus, has many outstanding characteristics. The unusually thin epidermis and dermis are generally devoid of melanotic melanocytes. The surface of the interramal gular region is peppered with small, elevated papillae; that of the corpus penis is characterized by keratinized, proximally directed hollow spines in whose cavities are organized nerve end-organs and capillary loops. Cholinesterase-reactive papillary nerve end-organs and Meissner corpuscles populate all volar friction surfaces. A highly vascular dermis and subcutaneous fat pad partially contribute to the characteristic rubicund color of the face, external ears, and anogenital region. Many body surface hairs are accompanied by the classic Haarscheibe of Pinkus. Sinus hairs are plentiful; a circumscribed vibrissa-bearing eminence is located on the ventral ulnar aspect of each wrist. Alkaline phosphatase-positive, stellate-shaped cells are found on the outer root sheath and epithelial sac of active and quiescent hairs in all cephalic regions; such cells are not argyrophilic, aurophilic, or osmiophilic. Hairs grow in linear perfect sets of 3 to 5 follicles; they do not grow singly on the cheek. Large sebaceous glands contain alkaline phosphatase in their peripheral acini; extensive fields of gigantic multilobular sebaceous glands contribute to the distinct, opaque-white color of the scrotal skin. Numbers of apocrine sweat glands are diminished in cephalic regions but one gland occurs with each hair follicle in the axilla, scrotum, suprapubic region, and ulnar eminence. Relatively avascular eccrine sweat glands are confined to the volar friction surfaces. Their secretory coils contain sporadically distributed glycogen and phosphorylase and surrounding nerves are much more reactive for acetyl- than butyrylcholinesterase.     

The adhesive organ of the blowfly, Calliphora vomitoria: a functional approach (Diptera: Calliphoridae)

The external morphology of the terminal region of the fifth tarsal segment of the blowfly, Calliphora vomitoria (L.) has been studied using light and scanning electron microscopy (S.E.M.). The pulvilli, with their numerous tenent hairs of spatulate form projecting from the ventral surface, are responsible for adhesion to smooth surfaces. The two large claws are believed to be important in clinging to irregularities in surfaces. Two footplates, possibly sensory organs, lie in close association with the base of the large ventral seta, the empodium. Blowflies release a non-volatile lipid secretion on to the spatulate ends of the tenent hairs and this secretion is essential to the adhesion process on smooth surfaces. The force of adhesion has been measured for tethered blowflies on glass using both vertical and lateral pulls; lateral pulls gave much greater forces. It is concluded that surface tension of the lipid secretion under tenent hairs is sufficient to enable successful adhesion to smooth surfaces by blowflies.     

A comparative study of the integument of the camel, Dorcas gazelle and jerboa in relation to desert life

Comparative histological studies of the integuments of the Dorcas gazelle, jerboa and camel have revealed the presence of tubular sweat glands in the skin of the Dorcas gazelle and the camel but not in the jerboa.
Hairs occur in groups in the skin of jerboa and camel but occur singly in the Dorcas gazelle where they are of two types; short under hairs and long covering hairs. Each hair follicle is associated with a sebaceous gland. Both the unkeratinized epidermis and its horny layer are comparatively thin in the jerboa and gazelle, and in dry air this may permit greater loss of water by transpiration than in the camel which has a comparatively thick epidermis.     

Fine structure and physicochemical analysis of the metathoracic scent glands of Lincus Malevolus (Rolston) and L. Spurcus (Rolston) (Heteroptera : Pentatomidae)

Bugs of the genus Lincus (Heteroptera : Pentatomidae) are attracted by volatile compounds emitted from the inflorescences of fertile palms. To define the basis of their chemical ecology, we have studied the metathoracic scent glands (MTG) of males and females of 2 species, L. spurcus and L. malevolus. The metathoracic scent gland system belongs to the diastomien type. The 2 glandular pores located between the mesothoracic and metathoracic coxae are associated with “crescent-like” evaporation areas. The large median reservoir, which is composed of one type of flattened pigmented epithelial cells, is flanked by multitubular lateral glands. These glands result from the apposition of 2 cell-type glandular units. The strip-like accessory gland is embedded in the reservoir wall. At its level, the thinner cuticular intima forms finger-like invaginations where a protein secretory product is secreted. Extracts of the volatile fraction of the metathoracic gland secretion were analyzed by capillary gas chromatography (GC) and by GC-mass spectrometry (GC-MS). These analyses exhibited a typical pentatomid MTG composition. The glands of L. spurcus and L. malevolus males and females contain 11 compounds: (E)-2-hexenal, 4-keto-(E)-2-hexenal, (E)-2-hexenoic acid, decane, (E)-2-octenal, undecene, undecane, (E)-2-octenly acetate, (E)-2-decenal, tridecane and (E)-2-decenyl acetate, including 3 major compounds, which represent 60–85% of the secretion in the 2 species: (E)-2-hexenal, (E)-2-octenal, and n-undecane. The 4-keto-(E)-2-hexenal is present only in the L. malevolus MTG, and represents 26% of its secretion. The female extracts of both species are characterized by the presence of (E)-2-hexenoic acid, which was detected in the male extracts as traces.     

Periphyton communities in a pristine mountain stream above and below heavy metal mining operations

SUMMARY. 1. Changes in species composition of the periphyton on introduced substrates were determined in an oligotrophic mountain stream subject to long-term heavy metal contamination.
2. At the upstream control site, the numerically most abundant taxa were Bacillarioph yta i( Achnanlhes minutissima, Achnanthes microcephala and Achnanthes linearis ) as well as, in summer, the Chlorophyta ( Mougeotia spp. and Ulothrix subtilissima ).
3. At the downstream contaminated site the periphyton community was totally dominated by Bacillariophyta throughout the sampling period. A, minutissima and A, microcephala were co-dominants during spring. Seasonal succession patterns did not parallel those at the upstream site. Chlorophyta were virtually absent and A. minutissima comprised 94% of the community during summer.
4. Species diversity, species evenness and dissimilarity index were utilized to detect differences in species composition, abundance and number. Slight differences were found in spring samples while summer samples indicated major differences between sampling sites.     

Respiratory morphology of the Abedus herberti Hidalgo egg chorion (Hemiptera: Belostomatidae)

Although giant water bugs (Hemiptera: Belostomatidae) are large, aquatic insects known for their obligate paternal egg brooding behaviors, little research has focused on the structure of their eggs. The respiratory requirements of developing embryos likely created selection for brooding, so a thorough understanding of the respiratory morphology of belostomatid eggs could help explain how brooding behaviors facilitate embryonic gas exchange. This study used scanning electron microscopy to document the respiratory microstructure of the eggs of Abedus herberti, a back brooding giant water bug. The exochorion is similar to that of other belostomatids in texture and organization except that the respiratory region is confined to the uppermost quarter of the egg. This is the area exposed to the atmosphere by encumbered males. A plastron network made up of densely packed vertical projections demarcates the boundary between the respiratory and nonrespiratory regions of the chorion. The internal chorion is composed of alternate air‐filled and denser layers that likely facilitate the movement of oxygen from the aeropyles at the top of the eggs to the developing embryonic tissues. J. Morphol., 2011. © 2011 Wiley‐Liss, Inc.     

Scanning electron microscopic studies of Trypanosoma cruzi in the rectum of its vector Triatoma infestans

The cuticular surface of the rectum of Triatoma infestans and its colonization by a Trypanosoma cruzi strain originating from the same locality as the bugs were studied by scanning electron microscopy at different weeks post infectionem. On the basis of the cuticular folding, the rectum can be subdivided into five regions. The rectal gland has the finest structure and the region anterior to the anus the deepest folds. Try. cruzi always prefers to colonize the rectal gland, while the other regions are colonized in varying densities. Most of the flagellates are epimastigotes (long and short), except in the region at the entrance of the midgut, where trypomastigotes predominate.     

Comparative morphology of the odoriferous system in three predatory stink bugs (Heteroptera: Asopinae)

The metathoracic scent system in Heteroptera produces and releases defensive volatile compounds. The odor produced by predatory stink bugs differs from phytophagous bugs, suggesting a variation between the structure and function of the metathoracic scent system. The anatomy and ultrastructure of the external thoracic efferent system, scent gland, and reservoir in the stink bug predators Brontocoris tabidus, Podisus nigrispinus, and Supputius cincticeps (Heteroptera: Pentatomidae: Asopinae) were studied. External thoracic efferent systems of B. tabidus, P. nigrispinus, and S. cincticeps have anatomical differences in ostiole, peritreme, and evaporatorium. Scent glands have a secretory portion and a reservoir. The reservoir has irregular projections, and in B. tabidus, it is enlarged and heart shaped, whereas in P. nigrispinus and S. cincticeps it is flattened and semicircular. The secretory tissue of the scent gland has well-developed globular secretory cells that produce odorous compounds, and the reservoir has a single layer of cubical cells lined by a cuticular intima. Secretory cells are type III with an intracellular end apparatus, well-developed nucleus with decondensed chromatin, and cytoplasm rich in mitochondria, lysosomes, granules, and smooth endoplasmic reticulum. These findings suggest that there are differences in physiological function of the odoriferous system and the volatile compounds produced by the secretory cells, which may indicate variation in defensive behavior of these species.     

ULTRASTRUCTURAL DEVELOPMENT OF CAPITATE GLANDULAR HAIRS OF CANNABIS SATIVA L. (CANNABACEAE)

The capitate-sessile and capitate-stalked glands of the glandular secretory system in Cannabis, which are interpreted as lipophilic type glandular hairs, were studied from floral bracts of pistillate plants. These glands develop a flattened multicellular disc of secretory cells, which with the extruded secretory product forms the gland head and the auxiliary cells which support the gland head. The secretory product accumulates beneath a sheath derived from separation of the outer wall surface of the cellular disc. The ultrastructure of secretory cells in pre-secretory stages is characterized by a dense ground plasm, transitory lipid bodies and fibrillar material, and well developed endoplasmic reticulum. Dictyosomes and dictyosome-derived secretory vesicles are present, but never abundant. Secretory stages of gland development are characterized by abundant mitochondria and leucoplasts and by a large vacuolar system. Production of the secretory product is associated with plastids which increase in number and structural complexity. The plastids develop a paracrystalline body which nearly fills the mature plastid. Material interpreted as a secretion appears at the surface of plastids, migrates, and accumulates along the cell surface adjoining the secretory cavity. Extrusion of the material into the secretory cavity occurs directly through the plasma membrane-cell wall barrier.