An independently evolved Dipteran silk with features common to Lepidopteran silks

Male hilarine flies (Diptera: Empididae: Empidinae) present prospective mates with silk-wrapped gifts. The silk is produced by specialised cells located in the foreleg basitarsus of the fly. In this report, we describe 2.3 kbp of the silk gene from a hilarine fly (Hilara spp.) that was identified from highly expressed mRNA extracted from the prothoracic basitarsus of males. Using specific primers, we found that the silk gene is expressed in the basitarsi and not in any other part of the male fly. The silk gene from the basitarsi cDNA library matched an approximately 220 kDa protein from the silk-producing basitarsus. Although the predicted silk protein sequence was unlike any other protein sequence in available databases, the architecture and composition of the predicted protein had features in common with previously described silks. The convergent evolution of these features in the Hilarini silk and other silks emphasises their importance in the functional requirements of silk proteins.     

Ultrastructure of the sexually dimorphic tarsal glands and tegumental glands in gonyleptoid harvestmen (Opiliones,Laniatores)

In at least four closely related families of the diverse harvestmen lineage Gonyleptoidea, males may possess sexually dimorphic tarsal glands in the swollen tarsomeres of the basitarsus and/or metatarsus of leg I. The first histological and ultrastructural examination of the sexually dimorphic tarsal glands in leg I focused only on Manaosbiidae. In this study, we examine the morphology and ultrastructure of the sexually dimorphic glands, and their associated glandular openings, found in the basitarsus and/or metatarsus of leg I of males representing Cosmetidae, Gonyleptidae, and Cranaidae (glandular openings only). In cosmetids and gonyleptids, the tarsal glands are made up of 20–60 glandular units that form distinct groups within the prolateral and retrolateral half of the tarsomere. Each glandular unit consists of a pair of terminal secretory cells, an intercalary cell wrapped around the receiving canal, and a canal cell tightly wrapped around the length of the conducting canal. Cosmetidae, Gonyleptidae, and Cranaidae exhibit remarkably similar tarsal glands and gland openings although the location of the glands in the leg differs slightly among them. Males of these three families exhibit markedly different glands and glandular openings compared to males of the family Manaosbiidae. The sexually dimorphic tarsal glands may provide an important morphological character for determining phylogenetic relationships among gonyleptoid families. Finally, we provide morphological and ultrastructural data for the common tegumental glands. These data indicate that the sexually dimorphic tarsal glands are strikingly similar to, and may possibly be derived from, the tegumental glands. J. Morphol. 274:1203–1215, 2013. © 2013 Wiley Periodicals, Inc.     

Female genital system of the folding-trapdoor spider Antrodiaetus unicolor (Hentz, 1842) (Antrodiaetidae, Araneae): ultrastructural study of form and function with notes on reproductive biology of spiders

The genitalia of the female folding-trapdoor spider Antrodiaetus unicolor are characterized by two pairs of spermathecae that are arranged in a single row and connected to the roof of the bursa copulatrix. Each single spermatheca is divided into three main parts: stalk, bowl, and bulb, which are surrounded by the spermathecal gland. The epithelium of the spermathecal gland is underlain by a muscle meshwork and consists of different types of cells partly belonging to glandular cell units (Class 3 gland cells) that extend into pores in the cuticle of the stalk and bowl. Interestingly, the bulb lacks glandular pores and is characterized by a weakly sclerotized cuticle. This peculiarly structured bulb probably plays an important role in the discharge of the sperm mass. It is suggested that by contraction of the muscle layer the sperm mass may be squeezed out, when the bulb invaginates and expands into the spermathecal lumen, pushing the sperm to the uterus lumen. Each glandular unit consists of usually one or two central secretory cells that are for the most part surrounded by a connecting cell that again is surrounded by a canal cell. The canal cell, finally, is separated from the other epithelial cells (intercalary cells) located between the glandular units by several thin sheath cells that form the outer enveloping layer of the unit. The secretions are released through a cuticular duct that originates proximally between the apical part of the connecting cell and the apical microvilli of the secretory cells and runs into a pore of the spermathecal cuticle. The glandular products of the Class 3 gland cells likely contribute to the conditions allowing long-term storage of the spermatozoa in this species. Details regarding the ovary, the uterus internus, and the uterus externus are reported. Most of the secretion that composes the chorion of the egg is produced in the ovary. Glandular cell units observed in the uterus externus differ structurally from those in the spermathecae and likely play a different role. Finally, we briefly discuss our results on the female genitalia of A. unicolor in the light of knowledge about the reproductive biology of spiders.     

Reproductive strategies and parasitization behavior of Ageniaspis citricola, a parasitoid of the citrus leafminer Phyllocnistis citrella

We 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.     

Morphology and histology of secretory setae in terrestrial larvae of biting midges of the genus Forcipomyia (Diptera: Ceratopogonidae)

Apneustic larvae of the genus Forcipomyia possess unique secretory setae located on the dorsal surface along the body in two rows, one pair on each thoracic and abdominal segment and two pairs on the head. Morphological and histological studies of secretory setae in fourth instar larvae of Forcipomyia nigra (Winnertz) and Forcipomyia nigrans Remm indicate they are modified mechanoreceptors (sensilla trichodea) in which the trichogen cell is a glandular cell producing a hygroscopic secretion. The cytoplasm of the glandular trichogen cell fills the lumen of a secretory seta, which shows one or more pores on the apex. The cytoplasm contains numerous microtubules responsible for transportation of proteinaceous vesicles, and an extremely large polyploid nucleus typical of gland cells. The main role of the hygroscopic secretion is to moist the body and thus facilitate cuticular respiration.     

Ultrastructural investigation of a salivary gland in a centipede: structure and origin of the maxilla I-gland of Scutigera coleoptrata (Chilopoda, Notostigmophora)

The maxilla I-gland of Scutigera coleoptrata was investigated using light and electron microscopy methods. This is the first ultrastructural investigation of a salivary gland in Chilopoda. The paired gland opens via the hypopharynx into the foregut and extends up to the third trunk segment. The gland is of irregular shape and consists of numerous acini consisting of several gland units. The secretion is released into an arborescent duct system. Each acinus consists of multiple of glandular units. The units are composed of three cell types: secretory cells, a single intermediary cell, and canal cells. The pear-shaped secretory cell is invaginated distally, forming an extracellular reservoir lined with microvilli, into which the secretion is released. The intermediary cell forms a conducting canal and connects the secretory cell with the canal cell. Proximally, the intermediary cell bears microvilli, whereas the distal part is covered with a distinct cuticle. The cuticle is a continuation of the cuticle of the canal cells. This investigation shows that the structure of the glandular units of the salivary maxilla I-gland is comparable to that of the glandular units of epidermal glands. Thus, it is likely that in Chilopoda salivary glands and epidermal glands share the same ground pattern. It is likely that in compound acinar glands a multiplication of secretory and duct cells has taken place, whereas the number of intermediary cells remains constant. The increase in the number of salivary acini leads to a shifting of the secretory elements away from the epidermis, deep into the head. Comparative investigations of the different head glands provide important characters for the reconstruction of myriapod phylogeny and the relationships of Myriapoda and Hexapoda.     

Ultrastructure et maturation de la glande accessoire de la spermatheque chez Speonomus delarouzeei fairm. (Coleoptera : Catopidae) du milieu souterrain

The maturation, histology and ultrastructure of the spermathecal accessory gland of Speonomus delarouzeei (Celeoptera : Catopidae) were studied. The functional units of the epithelium surrounding the gland cavity consist of 2 cells: one secretory cell and one ductile cell, which allows the secretory products to pass into the central lumen. The complete development of this gland takes 24 – 32 days after emergence. When the glandular cells are fully developed, their secretory products reach the pouch of the spermatheca. From then on a high percentage of females copulate.     

Developmental study of the ventral scent gland of the Mongolian gerbil]

Male and female in bred Mongolian gerbils aged 4, 5, 10, and 20 weeks were examined for the presence of a ventral scent gland macroscopically and histologically. It was found in about half of the gerbils aged 4 weeks and in all of the gerbils aged over 5 weeks. In adult male gerbils it weighed three times as much as in females. The ventral scent gland exhibited a sebaceous-like structure which consists of giant glandular cells with small vacuoles in the cytoplasm and the glandular cells displayed eosinophilic bodies contained within a duct, which are extruded through the lumen as holocrine-type secretion.     

Hormonal stimulation and in vitro cellular differentiation in the integument of the desert locust Schistocerca gregaria (author's transl)

Spontaneous cellular differentiation (glandular units appearance with a well-defined duct) is observed in larval integument of Schistocerca cultured in an hormone free medium. Hormonal stimulations modify the expression of this phenomenon, particularly the frequency of new elaborated duct cells belonging to secretory units. The most effective factor is supplied by the prothoracic glands. Complete secretory units can be observed but the glandular cells are in an undifferentiated and unfunctional state. They appear active if the corpora allata act after the prothoracic glands. Corpora allata alone or synthetic juvenile hormones have an inhibitory effect. The addition of alpha-ecdysone permits only cellular divisions, a preliminary and indispensable condition for ulterior differentiation. Between cuticles deposited with beta-ecdysone, new formed ducts take place in the theorical imaginal exuvia. These observations prove that the elaboration and the activity of imaginal glandular units are conditioned by the larval hormonal context: by contrast, sex dimorphism is only a genetic dependant process.     

Male antennal gland of Amitus spiniferus (Brethes) (Hymenoptera : Platygastridae), likely involved in courtship behavior

The functional anatomy of integumentary adjacent glands of the 4th male antennomere, termed male sex-antennomere (MSA4), of Amitus spiniferus (Brethes) (Hymenoptera : Platygastridae), is described. Externally, the lateral side of the MSA4 presents an elliptical, glabrous, and elevated plate with about 20 scattered pores. Internally, there is a glandular area consisting of some 20 isolated, 2-celled secretory units beneath the elevated plate. Each gland has a secretory cell, forming a cuticular receiving canal, and a canal cell, forming the conducting canal, which connects the receiving canal to the external glandular opening. The abundant secretion appears on the cuticular surface in cylindrical forms and as droplets, and probably acts as a recognition and/or an aphrodisiac pheromone during mating. This hypothesis is discussed with regard to behavioral observations reported for only 3 other known cases of similar glands in parasitoids. Modified antennomeres with specialized structures are briefly reviewed, and their secretory function and taxonomic importance in parasitic Hymenoptera, suggested.     

Tarsal taste sensilla of the autumn gum moth, Mnesampela privata: morphology and electrophysiological activity

Mnesampela privata Guenée (Lepidoptera: Geometridae: Ennominae) is a native Australian geometrid that conducts considerable host assessment prior to ovipositing on its host plants, which belong to the genus Eucalyptus . The leaves of some of their hosts are covered with a particularly thick and waxy cuticle and we have shown that epicuticular waxes influence the oviposition preferences of females. This necessitates that M. privata has evolved specific chemosensory organs to assess the identity and perhaps even the quality of its hosts. In this work, we examined the morphology of tarsal taste sensilla and the sensitivity of their sensory neurones to a range of primary metabolites possibly influential on host assessment and oviposition. The ventral surface of the fifth tarsomere of females bear two parallel rows of up to eight sensilla, each loosely aligned with two parallel rows of five spines. Salts, sugars, and amino acids elicited phasi-tonic multicellular neuronal responses of variable magnitude and form. Two pairs of sensilla are closely apposed to the most distal spine in each row; the sensory neurones associated with these sensilla exhibited notably larger responses to alanine and serine compared with those of all other sensilla. The arrangement of the taste sensilla in close proximity to prominent tarsal spines is unique and could represent an adaptation that enables them to penetrate the wax layer and be brought into contact with primary metabolites present closer to the leaf surface.     

Ultrastructure of the epidermal maxilla II-gland of Scutigera coleoptrata (Chilopoda, Notostigmophora) and the ground pattern of epidermal gland organs in Myriapoda

The epidermal maxilla II-gland of Scutigera coleoptrata was investigated using light and electron microscopy. The glandular epithelium surrounds a spacious integumental cavity at the base of the maxilla II. The gland is formed as a compound gland organ that is composed of thousands of epidermal gland units. Each of them consists of four different cell types: a secretory cell, an accessory or intermediary cell, and a proximal and distal canal cell. The intermediary and the two canal cells form a conducting canal. Only in the most distal part of the intermediary cell is the canal lined by a cuticle. In the area of the two canal cells, the conducting canal is completely covered by a cuticle. The canal passes through the cuticle and opens into the spacious integumental cavity, which serves as a secretion reservoir. The structural organization of the epidermal maxilla II-gland was compared to that of other compound epidermal gland organs in Chilopoda and Diplopoda. All these glandular organs in Myriapoda share the same ground pattern.     

Fine structure of the ventral and dorsal lobes of the prostate in the young adult Syrian hamster, Mesocricetus auratus

The normal ventral and dorsal prostatic lobes of the young adult Syrian hamster were examined at the light and electron microscopic levels. Each lobe is composed of branched tubular secretory units separated from each other by loose interacinar connective tissue and draining into the urethra. The lumen of each acinus is lined by a simple epithelium composed of columnar secretory cells with occasional small basal cells. The epithelial layer, with the thin underlying lamina propria, forms a mucosa that is often highly folded. The whole acinus is bounded by a thick muscular stroma. In each of the ventral lobes, there are three main ducts, each one formed of tubular branched tributary secretory units. The walls of the secretory acini are moderately folded. Microvilli dominate the lumenal surface of the secretory epithelial cells. The Golgi complex is very extensive and shows dilated cisternae and secretory vesicles and vacuoles of various sizes. Membrane-bounded secretory granules populate the Golgi and apical areas and are released into the acinar lumen by exocytosis. The rough endoplasmic reticulum is dispersed throughout the cytoplasm, except in the region of the Golgi apparatus. In each of the dorsal lobes, there are several main tubular ducts that open into the urethra. Both proximal (ductal) and distal portions of the glandular tree are secretory in nature. Microvilli and cytoplasmic bulges and blebs dominate the lumenal surface of the secretory cells. The cells are also characterized by highly dilated cisternae of rough endoplasmic reticulum. The secretory cells show heterogeneity in the degree of dilation and distribution of rough endoplasmic reticulum, and this heterogeneity may reflect location in the glandular tree.(ABSTRACT TRUNCATED AT 250 WORDS)     

Morphology and electrophysiology of water receptors on legs of the cricket Gryllus bimaculatus

To identify the sensory organs that are sensitive to water stimuli in the cricket Gryllus bimaculatus, cuticular structures on the legs and the number of sensory neurons innervating them were studied. Some small hair sensilla on the legs were innervated by 2-5 sensory neurons. All such sensilla had a tiny pore at the tip of their hairs. The diameter of the pore was approximately 0.2 mum. These findings suggest that these are chemosensitive hairs (LCS: leg chemosensillum). Of the three pairs of legs, the anterior legs (forelegs) possessed the largest number of LCSs. Of the five leg segments (i.e., coxa, trochanter, femur, tibia and tarsus), the tarsus possessed the largest number of LCSs on each leg. Electrophysiological investigation by tip recording revealed that some of the LCSs contained water-receptor cells. Because the basitarsus possessed a larger number of LCSs than the other tarsomeres, the distribution of water-receptor-containing LCSs in the basitarsus of a foreleg was investigated morphologically and electrophysiologically. LCSs that contained water-receptor cells were mainly distributed on the ventral surface of the basitarsus. There were two types of water receptor that showed different response patterns to a stimulus, that is, phasic- and tonic-type water receptors. From the distribution of LCSs on the legs, the roles of these different types of water receptors in behavioral selection, that is, the initiation of swimming and the inhibition of flying, will be discussed.     

Ultrastructure of male accessory glands in the scorpionfly Sinopanorpa tincta (Navás, 1931) (Mecoptera: Panorpidae)

The ultrastructure of male reproductive accessory glands was investigated in the scorpionfly Sinopanorpa tincta (Navás, 1931) (Mecoptera: Panorpidae) using light and transmission electron microscopy. The male accessory glands comprise one pair of mesodermal glands (mesadenia) and six pairs of ectodermal glands (ectadenia). The former opens into the vasa deferentia and the latter into the ejaculatory sac. The mesadenia consist of a mono-layered elongated columnar epithelium, the cells of which are highly microvillated and extrude secretory granules by means of merocrine mechanisms. The epithelium of ectadenia consists of two types of cells: the large secretory cells and the thin duct-forming cells. These two types of cells that join with a cuticular duct constitute a functional glandular unit, corresponding to the class III glandular cell type of Noirot and Quennedey. The cuticular duct consists of a receiving canal and a conducting canal. The secretory granules were taken up by the receiving canal and then plunged into the lumen through the conducting canal.     

An exaggerated trait in insects: The prothoracic skeleton of Stictocephala bisonia (Homoptera: Membracidae)

The prothoracic skeleton of Stictocephala bisonia was investigated in adults and fifth-instar nymphs on a gross morphological (SEM, maceration) and light microscopic level. In both nymphs and adults, the prothoracic skeleton consists of the pronotum, episternum, epimeron, precoxale, sternum, trochantin, and two endoskeletal characters (furcal arms and pleural apophyses). In nymphs, the entire pronotum is a single-layered outgrowth of the integument communicating with the body cavity and filled with hemolymph and fat body cells (“spine”); the dorsal and ventral processes and the suprahumeral bud are extensions of this single-layered integument. In adults, the pronotum is composed of (1) a proximal, single-layered part, and (2) a larger, distal, double-layered part (“posterior reduplication”) with two cuticular layers separated by a thin lumen. The posterior reduplication is elevated above the body and forms hollow (air-filled) extensions (e.g., suprahumeral horns). Its two cuticular layers are connected through cuticular columns that appear on the external surface as pits. The lumen between these layers communicates with the body cavity and contains nerves and tracheae. In the lumen of newly eclosed adults, intercellular space, epidermal cells with long processes, and hemocytes with nonlipid granules are present. In the lumen of sclerotized adult pronota, the intercellular space has disappeared, together with definite cell boundaries. Several structures are associated with the external cuticle: two types of innervated sensilla trichodea that articulate in the center of external pits, sensilla campaniformia, sensilla coeloconica, and cuticular canals with exterior openings. The morphogenetic implications of pronotal construction, various aspects of adult prothoracic anatomy, and the value of glands and sensilla for an adaptive interpretation of the pronotum are discussed. J. Morphol. 238:157–178, 1998. © 1998 Wiley-Liss, Inc.     

Ultrastructural investigation of the vesicular glands in Scutigera coleoptrata (Chilopoda,Notostigmophora)

In the notostigmophoran centipedes, two pairs of vesicular glands have evolved. These paired glands are situated in the first and second trunk segment and open via cuticular ducts in the upper part of the particular pleura. The vesicular glands of Scutigera coleoptrata were investigated using light and, for the first time, electron microscopical methods. The glands consist of wide sac‐like cavities that often appear vesicular. The epithelia of both glands are identically structured and consist of numerous glandular units. Each of these units consists of four different cells: a single secretory cell, a small intermediary cell, and one proximal and one distal canal cell. The intermediary cell forms a conducting canal and connects the secretory cell with the canal cells. Proximally, the intermediary cell bears microvilli, whereas the distal part is covered with a distinct cuticle. The cuticle is a continuation of the cuticle of the canal cells. This investigation shows that the ultrastructure of glandular units of the vesicular glands is comparable to that of the glandular units of other epidermal glands in Chilopoda and Diplopoda, although the glands look completely different in the light microscope. Thus, it is likely that the vesicular glands and epidermal glands share the same ground pattern. With regard to specific differences in the cuticular lining of the intermediary cells, a common origin of epidermal glands in Myriapoda and Hexapoda is not supported. J. Morphol. 2009. © 2008 Wiley‐Liss, Inc.     

Histology and histochemistry of the accessory reproductive glands in the male hairy-nosed wombat (Lasiorhinus latifrons)

The accessory male reproductive glands of the hairy-nosed wombat, Lasiorhinus latifrons, are a prostate and three pairs of Cowper's glands. Component units of all are branched tubular structures of varying epithelial makeup and secretory content. The prostate has the carrotlike shape and three consecutive regions commonly found in marsupials. The regions differ in their tubular histology and histochemistry: all contain secretory globules in glandular lumina. Cowper's glands A and B are histologically identical except for the absence of interstitial mast cells from gland G: gland C is characterized by narrower tubules and larger epithelial cells. Histochemical tests for protein, carbohydrate and iron indicate that glycogen is a major secretory product of the prostate (largely posterior region), iron is also secreted (mainly posterior region) and a small quantity of acid mucin is produced (mainly central region). Glycogen is a feature also of anterior prostatic glandular epithelium and of the capping cells of the urethral transitional epithelium. Cowper's gland A has considerable protein in its secretion, gland B a neutral glycoprotein and gland C a sialomucin: the latter two also exhibit cytoplasmic glycogen in their secretory cells.     

Histology and histochemistry of the accessory reproductive glands in the male hairy-nosed wombat (Lasiorhinus latifrons)

Summary The accessory male reproductive glands of the hairy-nosed wombat, Lasiorhinus latifrons, are a prostate and three pairs of Cowper's glands. Component units of all are branched tubular structures of varying epithelial makeup and secretory content. The prostate has the carrotlike shape and three consecutive regions commonly found in marsupials. The regions differ in their tubular histology and histochemistry: all contain secretory globules in glandular lumina. Cowper's glands A and B are histologically identical except for the absence of interstitial mast cells from gland B: gland C is characterized by narrower tubules and larger epithelial cells. Histochemical tests for protein, carbohydrate and iron indicate that glycogen is a major secretory product of the prostate (largely posterior region), iron is also secreted (mainly posterior region) and a small quantity of acid mucin is produced (mainly central region). Glycogen is a feature also of anterior prostatic glandular epithelium and of the capping cells of the urethral transitional epithelium. Cowper's gland A has considerable protein in its secretion, gland B a neutral glycoprotein and gland C a sialomucin: the latter two also exhibit cytoplasmic glycogen in their secretory cells.     

Fine structure of the Nassonow's gland in the neotenic endoparasitic of female Xenos vesparum (Rossi) (Strepsiptera, Insecta)

Nassonow's gland consists of a number of cells with ducts that open on to the ventral surface of the brood canal in the cephalothoracic region of a neotenic female strepsipteran. The structural organization of the gland is reminiscent of the class 3 of the epidermal gland cells as defined by Noirot and Quennedey [Ann. Rev. Entomol. 19 (1974) 61], which consists of secretory and duct forming cells. The ultrastructure of the Nassonow's gland is described in female Xenos vesparum (Rossi) parasitic in the social wasp Polistes dominulus Christ. The large secretory cells are clustered in groups of three to four, rich in smooth endoplasmic reticulum and produce a secretion made up of lipids. In young females, just before mating, the ultrastructure of the cells and their inclusions indicate that they are active. In old-mated females the Nassonow's gland degenerates. Microvilli line an extracellular cavity and there are pores present in the irregularly thick cuticle of the efferent duct. The small duct forming cells, intermingle with epidermal cells, overlap secretory cells and produce a long efferent duct, the cuticle of which becomes thick close to its opening in the brood canal. Nassonow's gland could be the source of a sex pheromone, which might be capable of attracting the free-living male to a permanently endoparasitic female.