Diversity and function of male antennal glands in Cynipoidea (Hymenoptera)

The functional anatomy of antennal glands located either on the 3rd or on the 3rd and 4th antennomeres in males of several species of cynipoids was investigated. SEM observations revealed variously modified antennomeres with elevated plates, tyloids and excavated areas. In all the cases, the antennomeres are equipped with cuticular pores, corresponding internally to cuticular ducts. TEM studies showed the presence of type III integumentary glands, as classified by Noirot & Quennedey. Each glandular unit is made up of an innermost secretory cell, producing the secretion, and an outermost canal cell, producing the evacuating duct. The secretion passes through the duct and reaches the cuticular pores, concentrated in a ventro-lateral portion of the antennomere called the 'release and spread structure'. Both in Cynipidae and in Eucoilinae (Figitidae), the courtship behaviour includes a pre-copulatory phase characterized by intense antennal stroking. Bioassays in the eucoilins Leptopilina boulardi and L. heterotoma showed that these glands are the production site of a contact sex recognition pheromone, necessary for the female to accept the male.     

Antennal courtship and functional morphology of tyloids in the parasitoid wasp Syrphoctonus tarsatorius (Hymenoptera: Ichneumonidae: Diplazontinae)

Courtship behaviour and associated morphological characters are believed to evolve under diversifying sexual selection. In Hymenoptera, sexually dimorphic antennal structures, the ‘tyloids’, show a large variability. Although crucial for functional interpretation, the link between tyloid morphology and courtship behaviour has gained only limited attention. Here, we investigate antennal morphology and antennal courtship in the parasitoid wasp Syrphoctonus tarsatorius (Hymenoptera: Ichneumonidae: Diplazontinae). We confirm the glandular nature of the tyloids by light and scanning electron microscopy. Moreover, we report a new form of antennation during courtship, antennal double-coiling, which links morphology and behaviour by bringing the tyloids in direct contact with the antennae of the female, thus probably facilitating the transfer of a contact pheromone. We show that a change in haemolymph pressure is the activator of the antennal movement and that it can be reproduced in the laboratory using amputated antennae. Investigations of antennal structure and movement in three additional hymenopteran species suggest that the number and location of tyloids coincide with the modality of antennal coiling. Our method for simulating antennal movement will enable retrieving information about courtship behaviour from museum specimens, thus leading to a better understanding of the evolution of courtship behaviour in Hymenoptera.     

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.     

Communication in the courtship of a madagascan hissing cockroach. II. Effects of deantennation

The role of the antennae in courtship was studied by removing the antennae bilaterally from both male and female cockroaches, which were then paired with intact animals. These experimental pairings were compared with each other and with pairings of normal animals. Significant deviation from normal behaviour occurs in both the deantennated and the intact members of experimental pairs. When males are deantennated and paired with intact females the timing of courtship is prolonged and male cockroaches misdirect many of their copulation attempts. Under these conditions the intact female cockroaches perform some behaviours more frequently, in particular mounting and palpation. When deantennated females are paired with intact males, very little courtship ensues. The results suggest that information important to the progress of courtship is provided by both antennal inputs and antennal movements, and that the cockroaches are capable of some behavioural flexibility when deprived of this information.     

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.     

The ultrastructure and function of the silk-producing basitarsus in the Hilarini (Diptera: Empididae)

The tribe Hilarini (Diptera: Empididae), commonly known as dance flies, can be recognised by their swollen silk-producing prothoracic basitarsus, a male secondary sexual characteristic. The ultrastructure and function of the silk-producing basitarsus from one undescribed morphospecies of Hilarini, 'Hilarempis 20', is presented. Male H. 20 collect small parcels of diatomaceous algae from the surface of freshwater creeks that they bind with silk produced by the gland in the basitarsus. The gift is then presented to females in a nearby swarm, composed predominately of females. The basitarsus houses approximately 12 pairs of class III dermal glandular units that congregate on the ventral side of the cavity. Each gland cell has a large extracellular lumen where secretion accumulates. The lumen drains to the outside via a conducting canal encompassed by a canal cell and a duct extending through the shaft of a specialised secretory spine. The secretory spines lie in pairs in a ventral groove that runs the length of the basitarsus. A comparison of the basitarsal secretory spines with sensilla on the basitarsi of non gland-bearing legs of males, and with non gland-bearing prothoracic basitarsi of females, suggests that the glandular units are derived from contact chemosensory sensilla.     

The fine structure of the female reproductive system of Zorotypus caudelli Karny (Zoraptera)

The general structure of the female genital system of Zorotypus caudelli is described. The ovarioles are of the panoistic type. Due to the reduction of the envelope (tunica externa) the ovarioles are in direct contact with the hemolymph like in some other insect groups, Plecoptera included. The calices are much larger in Z. caudelli then in Zorotypus hubbardi and their epithelial cells produce large amounts of secretions, probably protecting the surface of the eggs deposited on the substrate. Eggs taken from the calyx bear a series of long fringes, which are missing in the eggs found in the ovariole, and in other zorapteran species. The long sperm of Z. caudelli and the long spermathecal duct are likely related to a sexual isolating mechanism (cryptic female choice), impeding female re-mating. The apical receptacle and the spermathecal duct - both of ectodermal origin - consist of three cell types. In addition to the cells beneath the cuticle lining the lumen, two other cell types are visible: secretory and canal cells. The cytoplasm of the former is rich in rough endoplasmic reticulum cisterns and Golgi complexes, which produce numerous discrete dense secretory bodies. These products are released into the receiving canal crossing the extracellular cavity of secretory cells, extending over a series of long microvilli. The secretion is transported towards the lumen of the apical receptacle of the spermatheca or to that of the spermathecal duct by a connecting canal formed by the canal cells. It is enriched by material produced by the slender canal cells. Before mating, the sperm cells are enveloped by a thick glycocalyx produced at the level of the male accessory glands, but it is absent when they have reached the apical receptacle, and also in the spermathecal duct lumen. It is likely removed by secretions of the spermatheca. The eggs are fertilized at the level of the common oviduct where the spermathecal duct opens. Two micropyles at the dorsal side of the equator level possibly facilitate fertilization. The presence of these two micropyles is a presumably derived feature shared with Phasmatodea. The fine structure of the female reproductive system of Z. caudelli does not allow to assess the phylogenetic position at the present stage of knowledge. The enlarged calyx and the temporary presence of long fringes on the eggs are potential autapomorphies of Z. caudelli or may indicate relationships with other Zorotypus species.     

Cycles of mating behaviour, oestrogen and progesterone in the thick-tailed bushbaby (Galago crassicaudatus crassicaudatus) under laboratory conditions

Vaginal smears and blood samples were taken throughout the reproductive cycle of female Galago c. crassicaudatus. Blood plasma was assayed for oestradiol and progesterone, and vaginal smears were initially classified dioestrus or vaginal oestrus. During vaginal oestrus the females were tested daily for sexual receptivity by being placed with a male. Those days on which the male achieved intromission were reclassified as behavioural oestrus. During dioestrus the females were tested weekly with males. Female receptivity increased and then declined across a 6-day period of behavioural oestrus during the 44-day cycle. Fully cornified smears were characteristic of the period of maximal receptivity and oestradiol secretion. The luteal phase lasted 24 days with a plasma progesterone peak midway through dioestrus.     

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.     

Some relationships between the process of pair formation and gamete maturation in Harmothoë imbricata (L) (Annelida: Polychaeta)

Male and female Harmothoë imbricata form pairs in preparation for spawning although the individuals are normally mutually antagonistic. This change in behaviour is due to a reduction in aggression shown by the females as they approach maturity. Immature males attempt to mount but are normally repulsed by the aggressive immature females. No obvious behavioural change occurs during the period of final gamete maturation in the male. Pair formation results in the paired female spawning sooner than would an equivalent female kept in isolation. Release of sperm over the newly formed egg mass is ensured by receptors on the ventral cirri which inform the male that the female has spawned.     

Location and ultrastructure of sex pheromone glands in female Callosobruchus maculatus (Fabricius) (Coleoptera : Bruchidae)

The ultrastructure of the female sex pheromone glands in Callosobruchus maculatus (Coleoptera : Bruchidae) were localized using a masking technique, combined with eiectro-antennography and by a comparison of the glandular cells of sexually active (flightless) females and non-sexually active (flight-form) females. Each unicellular gland is an invagination of the integumental membrane capped by a single secretory cell. These glands are situated on the fine intersegmental membrane, which joins the pygidium to the ovipositor. The secretory cells of the glands of active females are characterized by well-developed microvilli, with many elongated mitochondria among the latter. The high metabolic activity of these cells is revealed by the presence of heterogeneous secretion vesicles, some of which contain abundant crystallized material. Deep basal invaginations indicate the uptake of substances from the haemolymph. The receptor canal is a network of fine cuticular filaments which have the same structure regardless of the female's sexual status. Cells from the glands of non-sexually active females are underdeveloped and show no invaginations of the basal membrane and very few microvilli. The localization of these glands was made possible by the use of SEM, TEM and EAG as well as by masking the suspected zones and by comparing females in different physiological states: flightless females, which were sexually active and producing pheromones; and flight-form females, non-sexually active and producing no sex pheromones. Only by adopting such a stringent method was it possible to confirm the function of the glands whose ultrastructure was studied.     

The role of the androconia in the mating behaviour of the European skipper, Thymelicus lineola, and evidence for a male sex pheromone

Abstract. Laboratory experiments were carried out to determine the role and characteristics of male scent scales (androconia), located in patches (stigmata) on the forewings of Thymelicus lineola (Ochsenheimer) (Lepidoptera: Hesperiidae). In behavioural tests, there were 30—40% fewer matings of virgin females by males with the stigmata removed or where females had their antennal sensilla covered with nail polish, when compared to sham-treated controls. These reductions occurred despite a large increase in male courtship activity. No physical contact was observed between male wings and female antennae during mating. A scanning electron microscope study of male wings and female antennae showed that: (1) lysis zones form over time on the androconia and pieces (osmo-phores) distal to these zones break off; (2) while few of these zones are present at emergence they are numerous in-day-old males; (3) during a single episode of courtship and mating approximately two-thirds of the available osmophores break off, yet the commonly observed courtship between males does not appear to result in osmophore release; and (4) osmophores were never observed on the female antennae. Electroantennogram recordings (EAGs) indicated that: (1) female antennae responded strongly to odours from male forewings but not from other parts of either males or females; (2) female antennae responded more strongly to young field-collected males than to newly-emerged or old, field-collected males; (3) female antennal response to male forewings was reduced if the androconia were scraped off, and was eliminated if the stigmata were removed; (4) male antennae gave weak EAG responses to both male and female forewings. We conclude that males release pheromone via the breakage of osmophores during courtship. We propose that the frequently observed refusals by females of courting males are at least partially dependent on the quantity or quality of male pheromone released, which are in turn correlated with the male's age and mating status.     

Fine structure of postgonopodial glands of a myriapod Glomeris marginata (Villers)

The postgonopodial gland of the myriapod Glomeris marginata (Villers), which produces a pheromone, is an integumentary gland comprising numerous functional secretory units. Each secretory unit consists of two proximal secretory cells, an intermediary cell lacking secretory characteristics and a canal cell surrounding the canal, which is secretory in nature. Secretory proximal cells exhibit a zone of small channels originating from invaginations of the plasma membrane and through which secreted material is released. Apposing each invagination of these cells is a corresponding invagination of the intermediary cell: the two units in the centre of the intermediary cell join another which communicates with the canal. Secretion produced by the latter passes through the canal wall and blends with secretion of the two proximal cells. The most striking feature of all these cells is the abundance of tubules and fibrils in the small canal zone in the proximal cells, which also exhibits a centriole; in the intermediary cell around cytoplasmic membrane invaginations where a diplosome is present, and in almost the entire canal cell.     

Courtship in two species of periodical cicadas, Magicicada septendecim and Magicicada cassini

Courtship behaviour of two species of periodical cicadas, Magicicada septendecim and M. cassini, was studied in the field during the 1970, 1973, and 1974 emergences of these insects. In areas where both species were courting there were differences in both male and female courtship patterns, both in acoustic and behavioural components. Experiments with models showed that male M. septendecim were more likely to court crude models of females than were M. cassini males. When females were ‘courted’ with models that could imitate some of male courtship, they were more receptive when the models' ‘songs’ were those of conspecific males. Acoustic differences between species are probably used by females in mate selection, maintaining species separation even in areas where the two species overlap in both space and time.     

Effect of metanotal secretion ingestion on oviposition in a tree cricket, Truljalia hibinonis (Orthoptera: Gryllidae)

The female Truljalia hibinonis ingests metanotal secretions of the male during copulation. The effect of ingestion on oviposition behavior was compared between three female groups: females that copulated once with an intact male (a male that had not been manipulated; M group); females that copulated once with a male from which most of the metanotal secretion had been removed (NO group); and females that copulated once with an intact male followed by being artificially supplied with metanotal secretion three times (MS group). There were no obvious differences in female fecundity across the three groups. However, within the MS group, intake of an optimal amount of metanotal secretion increased the number of eggs laid. This effect appeared quickly after ingestion and was most effective on the first bout (eggs laid during the first few days after copulation) after ingestion of the metanotal secretion. In contrast, the number of eggs laid had a negative correlation with the amount of metanotal secretion ingested when the amount exceeded the optimal in this experimental arrangement.     

Female accessory reproductive gland activity in the yellow dung fly Scathophaga stercoraria (L.)

The role of the female accessory reproductive glands has been investigated in relatively few insects. Gland secretion has a number of potential functions, including lubrication during copula, involvement in fertilization and protection of eggs. Female yellow dung flies (Scathophaga stercoraria) have large paired accessory glands whose function(s) prior to this study were unknown. Our study indicated glands were involved in copulation and egg laying. The volume of secretion remaining in glands was negatively associated with copulation duration, and this effect was most pronounced in non-ovipositing females. Gland volume and secretion volume remaining in the glands were significantly smaller in females which were allowed to oviposit. In addition, there was a significant interaction between male size, female size and whether or not females were allowed to oviposit which affected the volume of the secretion remaining in the glands, with changes in secretion volume being greatest when males were large. Sperm were found in the accessory glands of some females and this was apparently not related to age, mating history of either sex, to female nutrition or male size. Our results indicate that either large males stimulate greater secretory responses from females or that females alter their responses based on male size.     

A new role for antennation in paper wasps (Hymenoptera,Vespidae): antennal courtship and sex dimorphic glands in antennomeres

Summary. Males of Polistes dominulus perform antennal vibrations and grasping of female antennae during pre-copulatory and copulatory phases. Male antennation plays a relevant role in mating success. In several antennomeres of males of P. dominulus and Vespa crabro, a further species in which we observed male antennation, we found secretory cells of class 1 and 3 associated to the same release site. In P. dominulus, class 3 cells with ampulla-like reservoirs and class 1 cells release their secretion through hairless multiporous areas. In V. crabro, tyloid-like structures are associated with large apodemes. The as yet unidentified secretion of these glands may act as a contact or low-volatile sex pheromone during courtship behaviour.Received 4 December 2003; revised 16 August 2004; accepted 7 September 2004.     

Annual cycle of a coypu (myocastor coypus) population: male and female strategies

Male and female strategies were compared for wild–living populations of coypu (Myocastor coypus Molina) censused during two years in marshlands of central–west France. In a habitat composed of a canal network bisecting pasture fields typically 0–5 ha in size, coypu movements were largely restricted to stretches of open water, though males explored further from water than females. Adults occupied home ranges with a mean size of 3–82 ha or 1. 19 km of canal, males on average moving faster over a larger area and using a greater length of canal than females. Movements within partially shared ranges were most positively coordinated between male–female pairs, while male–male interactions were less frequent. Juvenile coypus were largely absent from the late winter population. Synchronization of litters in March–April resulted in a peak of juveniles in early summer. The sex ratio of juveniles and sub–adults reversed from a male bias in summer to a female bias in autumn. Population densities peaked in November at 4 ha, with a significant female bias (1M: 1–6F). In the same month, a neighbouring population at lower density (1 ha^-l after treatment with rodenticide) was significantly male biased (2–7M:lF) and may therefore have been acting as a sink for males dispersing from the high density population. Transients comprised 63% of the population. Females were resident longer than males, 22% of females remaining at least 5 months against 6% of males. Dispersal was recorded only for males aged 6 months or older. The general result, of exploratory behaviour amongst males contrasting with the establishment of longer term home ranges by females, is discussed in terms of male reproductive success and the capacity for females to influence nutrient supply to their litters.     

Cytophysiological study of neurosecretory and pheromonal influences on sexual development in Ophryotrocha puerilis (Polychaeta,Dorvilleidae)

Summary

Prominent secretory nerve endings are found at the posterior margin of the supraesophageal ganglion in the protandric polychaete, Ophryotrocha puerilis. Solitary juveniles developing as primary males, and then as females, accumulate neurosecretory material in the nerve endings which thereby swell and become filled with granules. Females maintained in mass culture have similar terminals, whereas in secondary males (males which had been females before), these axon terminals are very small and contain no material. When such males are isolated, they accumulate neurosecretory material within the nerve endings and become females. When formerly isolated females are put together, their stores of neurosecretory material are rapidly discharged. Subsequently they lay egg masses and switch to the male state. These effects are mediated by a pheromone released during social contact of formerly isolated females. The complexity of the relationship between neurosecretory activity and sexual state is indicated by the situation in animals maintained in pairs, when both male and female partners have swollen nerve endings packed with secretory material.     

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.