Histochemical and histophysical aspects of silk secretion in Melipona quadrifasciata (Hym., Apoidea)

Summary Acid and neutral polysaccharides exist in the secretion of the silk glands of Melipona quadrifasciata during the entire functional stage, except in the late 5th instar. However, only from the 3rd instar on is a molecularly oriented structural protein present. The following evidence indicates that this protein is not collagen: (1) the optical sign of its birefringence does not become reversed after von Ebner's reaction, and (2) its secretion can be detected when the cell nucleus attains a ploidy degree optimal for secretory activity. This is at first observed in the distal part of the glands and then throughout the organ.Stipendiat der Alexander von Humboldt-Stiftung.     

Electrophoretical studies of proteins of the hypopharyngeal glands and of the larval food ofMelipona quadrifasciata anthidioides Lep. (Hymenoptera,Meliponinae)

Summary The electrophoretical protein patterns of hypopharyngeal glands, larval food ofMelipona, and royal jelly ofApis were compared.Since protein patterns of hypopharyngeal glands from newly emerged workers, brood cell provisioners and foragers are similar to freshly deposited larval food, the identical protein bands probably represent actual gland secretion. This suggests that, as inApis, the glands secrete proteins to the larval food, and maintain this ability throughout life, although at slightly different intensities, according to the activity of the bees.The similarity on the electrophoretic profiles of the major larval food protein inApis andMelipona is an interesting finding because of its probable evolutionary significance.     

Histochemistry of the cuticle from proventriculus in stingless bee, Melipona quadrifasciata anthidioides (Hymenoptera, Apidae)

Histochemical study of the proventriculus from stingless bee Melipona quadrifasciata anthidioides revealed for the first time the presence of cysteine-rich proteins in the cuticle that covers the bulb of the proventriculus and its associated hair-like process. The presence of tyrosine-rich proteins was observed in the same structure, but not in hair-like projections. The cuticle of the crop and a small portion of the proventriculus contained no acid carbohydrates or fats and small amounts of neutral carbohydrates. These results are discussed in relation to different composition of insect cuticle depending on its different functions.     

Inheritance pattern of RAPD markers in Melipona quadrifasciata (Hymenoptera: Apidae, Meliponinae).

Melipona quadrifasciata is an important pollinator agent in several regions of Brazil. Data concerning the genetics of this species are scarce in the literature. In this work we used the random amplified polymorphic DNA (RAPD) technique to determine the degree of polymorphism and the inheritance pattern of these molecular markers in this species. Our ultimate goal is to establish tools to be used in the study of the genomic organization of M. quadrifasciata. Genomic DNA from progenies F(1) and BC(1) were assayed with 79 different primers, yielding an average of 6.67 bands and 1.68 polymorphisms per primer. Three types of polymorphisms were detected: band presence/absence, band intensity, and fragment-length polymorphisms. Most of the observed polymorphisms were band presence/absence, typical of RAPD-dominant markers. The number of observed polymorphisms and their segregation in accordance with a Mendelian proportion confirm the importance of this technique for genome analysis of species like M. quadrifasciata that are poorly studied at the genetic level.     

Histochemistry,refractometry, and fine structure of excretory globules in larval Malpighian tubes ofMelipona quadrifasciata (Hym., Apoidea)

Summary The authors have studied excretory globules in the Malpighian tubes ofMelipona larvae. By means of histochemical methods for fats, micro-interferometry and electron microscopy, glycerides surrounded by a lipoprotein or phospholipid layer were tentatively recognized in the globules. They resemble in composition the brochosomes reported in Homoptera and are found in the cell borders and in the lumina of the tubes. Yellow-green autofluorescent granules are seen within the cells, in the honeycomb borders and in the lumina of the tubes. It was not determined whether there are two distinct kinds of globules or only one kind in different physiological stages.This research was partly supported by FundaÇÃo de Amparo à Pesquisa do Estado de SÃo Paulo.     

Development of the rat salivary glands. II. The identification of a trypsinlike protease in the submaxillary gland

Trypsinlike protease activity at pH 9.2 was measured in tissue extracts of adult rat salivary glands by using a fluorometric assay in which β-naphthylamine is released by the hydrolysis of benzylarginine β-naphthylamide. The submaxillary gland contains high levels of this activity, and the parotid and sublingual glands have a maximum of 2000-fold and 200-fold less. After polyacrylamide disc gel electrophoresis at pH 8.3, the protease activity of submaxillary extracts is associated with a major protein band. Neither this protein band nor its protease activity is detectable in extracts of parotid or sublingual glands. Homogenates of newborn submaxillary gland do not have this protease activity at detectable levels, suggesting that its major accumulation is postnatal.     

Development and encapsulation of the endoparasitoid,Microplitis croceipes (Hym.: Braconidae), in six candidate host species (Lep.)

Encapsulation and development of the endoparasitoid,Microplitis croceipes (Cresson), were studied in six atypical lepidopteran host species whose usual host isHelicoverpa zea (Boddie). The candidate hosts examined were: the fall armywormSpodoptera frugiperda (J. E. Smith); the beet armyworm,Spodoptera exigua (Hübner); the cabbage looper,Trichoplusia ni (Hübner); the greater wax moth,Galleria mellonella (L.); the Indian meal moth,Plodia interpunctella (Hübner); and the diamondback moth,Plutella xylostella (L.). BothS. exigua andT. ni were completely unsuitable forM. croceipes development due to the high rate of eggs that were encapsulated within three days after parasitism. Encapsulation inS. frugiperda included mainly parasitoid eggs and was first detected six days after parasitization at 25°C and two days at 30°C. Encapsulation inG. mellonella occurred only in the larval stage of the parasitoid. InP. interpunctella, parasitoid larvae reached the 3rd stadium, but none of them pupated. OnlyS. frugiperda andG. mellonella supported successful development ofM. croceipes from egg to adult. The percentage of parasitoids reaching the adult stage in these hosts was higher at 30°C than at 25°C (13% vs. 4% inS. frugiperda, and 21% vs. 3% inG. mellonella, respectively). However, these percentages were too low to substitute them as a more economical host for rearingM. croceipes. This biological information will be useful in additional laboratory studies directed toward reducing the rate of encapsulation (e.g., manipulation of host rearing temperature) to increase production ofM. croceipes on these hosts.     

Structural changes in the salivary glands of Ixodes ricinus larvae

The authors analysed the structure of Ixodes ricinus (L.) larvae in specimens immediately after leaving the egg sheaths, in those which have not fed for 2 months after hatching, and in feeding larvae on the second day of feeding. The results showed that salivary glands in tick larvae are formed by alveoli aligned in strands on both sides of the central nervous system. These alveoli open into central efferent ducts via short ducts. The constituent elements of salivary glands include pyramidal alveoli (with numerous lipid droplets) and granular alveoli of varied structure. It is worth noting that salivary alveoli containing secretory material are present even in the larvae which had just left egg sheaths and were still endowed with deutoplasm.     

The evolution of food-producing glands in eusocial bees (Apoidea,Hymenoptera)1

A food-producing role for cephalic exocrine glands has arisen independently in both taxa of highly eusocial bees, Apis and Meliponini. With several exceptions, there is little evidence that food is produced by glands of solitary bees or by most bees at lower levels of sociality. We suggest that this association with sociality is due to four adaptive features of these glands: (1) food from the glands allows feces from queens and larvae to have a small volume, (2) the queen's fecundity can be increased, (3) nutrient recovery via cannibalism can be facilitated, and (4) rearing of emergency replacement queens is accelerated. Acceleration of the rearing of other castes and of queens in the normal process of colony fission is not clearly an advantage ascribed to these glands. Trophic eggs produced by meliponine colony workers are analogous to the secretions from food-producing glands in Meliponini and Apis workers.     

Influence of crucifer cropping system on the parasitism ofPlutella xylostella (Lep., Yponomeutidae) byCotesia plutellae (Hym., Braconidae) andDiadegma semiclausum (Hym., Ichneumonidae)

Field experiments were conducted to study the influence of cabbage monoculture and mixed cropping on the parasitism of diamondback moth,Plutella xylostella (L.), a destructive pest of all crucifers, by 2 larval parasites,Diadegma semiclausum Hellén andCotesia plutellae Kurdjumov. There was no significant difference in parasitism by either species whether cabbage was planted in insecticide-free monoculture or in mixed cropping with 8 noncrucifers which were sprayed twice a week with chemical insecticides mevinphos, methamidophos and permethrin. Population ofP. xylostella increased as the cabbage plants grew older. Parasitism byC. plutellae was higher soon after cabbage transplanting but decreased as the plants grew older. Parasitism byD. semiclausum was very low soon after cabbage planting but increased as the plants grew older. A significant negative correlation was found betwen parasitism byC. plutellae andD. semiclausum. In a caged field study where only one parasite species was used in an individual cage, parasitism ofP. xylostella by both species decreased as theP. xylostella population increased. This is believed to be due to the absence of competition between the two parasites inside the cage. There was no relationship between host-plant age and parasitism ofP. xylostella larvae by either parasite species.     

The labral glands in Centropages typicus (Copepoda,Calanoida). II. Sites of secretory release

Two groups of external excretory pores associated with glandular units (AU and LPU) were observed on the labrum, one pair laterally and three pairs posteriorly. Each external pore leads to an underlying conical, flask-shaped epidermal chamber. The wide base of this chamber is perforated by an internal pore that delivers secretions from the excretory duct of a glandular unit. The chambers serve to protect the internal pores from turbulence in the outside environment. Expulsion of secretions from the chambers is probably brought about by contraction of labral striated muscles, which synchronizes opening of the AU and LPU pores. A complex funnel-shaped structure forms the internal end of the excretory duct between each chamber and the corresponding pole of accumulation for the secretory product of a glandular unit. This structure, composed of an epidermal syncytium lined by a sleeve of several aligned auxiliary cells, probably ensures a tight connection between the epidermal chamber and the syncytium. The dorsalmost glandular units (LDU) have no pores in the vicinity of their poles of accumulation. Instead they secrete through cuticular ducts delimited by aligned auxiliary cells. External pores for these canals have not yet been located. The secretions of lateral pores may be mucopolysaccharides that play an essential role in agglutination of food particles soon after capture, while the secretions of posterior pores may contain glycoproteins that mix with food only after ingestion into the buccal cavity and probably start the process of digestion.     

The salivary glands of the cockroach Nauphoeta cinerea (Olivier)

The innervation of the salivary gland of the cockroach Nauphoeta cinerea (Olivier) has been investigated with the use of light and scanning electron microscopy. Light microscopy of methylene blue stained glands reveals the presence of a dual innervation arising from the ventral nerve cord and the stomodeal nervous system; the principal innervation is that from the ventral nerve cord which passes to the gland via the reservoir ducts. Branches of these nerves form a plexus on the acinar surface, the axons of which exhibit swelling at irregular intervals. The presence of this surface plexus and the axonal swellings was confirmed by scanning electron microscopy both in normal glands and in those in which the basal lamina had been removed by means of an HCl-collagenase digestion method. No acinar plexus was seen to be formed by branches of the stomatogastric nerve that were associated with the gland. However, other branches of this nerve were clearly connected with a complex network of multipolar neurones on the surfaces of the anterior regions of both salivary reservoirs.     

Musculature,nervous system and glands of metasomal abdominal segments of the male of Nomia melanderi Ckll. (Hymenoptera,Apoidea)

Each muscle of the third metasomal segment of the male of Nomia melanderi Ckll. is described in detail. The points of attachment of each muscle are compared with their homologs in other pregenital segments and with their homologs in the female. The function desgnated for each muscle describes its action alone or in conjunction with other muscle(s). New names are given to genital muscles by referring in the name to their points of attachment. Each intratergal muscle has homologous points of attachment in the pregenital segments of both sexes. The median tergo-dorsoplical muscle of the seventh segment and the oblique tergo-dorsoplical muscle of the eighth segment have changed their points of attachment. The intrasternal muscles are modified to suit the needs of courtship and mating, thus they are different from their homologs in the female. The spiracular muscles are well developed in all segments except the eighth, where the sterno-spiracular muscle is absent. The extrinsic genital muscles are derived from the intrasternal muscles of the eighth and ninth segments. The parameral and volsellar muscles are reduced in number. The aedeagal muscles, except the aedeago-phallic, have retained similar points of attachment to those found in primitive Hymenoptera. The topography of the metasomal nervous system is reported in detail by following each nerve and nervule to its termination. The study shows that (at least in Nomia) the criterion of nerve-concentration should not be used alone to indicate evolutionary levels. To accommodate the morphological changes in the terminal segments the Anterior and Posterior Lateral Nerves have migrated to new locations. The pattern of nerve topography (even at the nervule level) is homologous both in the different pregenital segments and between the sexes. The fact that homology does not exist between the external genitalia of the male and the modified ovipositor of the female supports the thesis that the male genital capsule is of phallic rather than prephallic origin. A pair of intersegmental membrane glands located between the seventh and eighth sterna is described. These glands may be the source of a pheromon responsible for gregariousness among “sleeping” males.     

Influence of the chickpea cropping system onHelicoverpa armigera (Lep.: noctuidae) populations and their rate of parasitism byCampoletis chlorideae (Hym.: ichneumonidae)

The effect of intercropping chickpea with coriander or linseed onHelicoverpa armigera Hübner egg and larval populations and on the rate of larval parasitism was examined. There were significantly moreH. armigera larvae per plot in the sole chickpea treatment than in the intercropped treatments. The reduction was not the result of a negative effect of the companion crops on the numbers of larvae attacking chickpea. Larval density on chickpea was higher in the intercropped plots than the plots of sole chickpea. The presence of the flowering companion crops did not result in either the attraction of otherwise uncommon parasitoids to the crop or an increase in the proportion ofH. armigera larvae parasitized byCampoletis chlorideae Uchida. The results suggest that chickpea is a more suitable host forH. armigera than coriander or linseed, and that the reduction in the density ofH. armigera larvae in the intercroped treatments was due to the lower number of chickpea plants in these treatments.     

Musculature, nervous system and glands of pregenital abdominal segments of the female of Nomia melanderi Ckll. (Hymenopters, Apoidea)

The gross anatomy of muscles, the topography of nerve tissues, and the histology of the pregenital abdominal glands of Nomia melanderi Ckll. are reported in detail. The movable and fixed points of muscle attachment were utilized in establishing a system of nomenclature for a typical abdominal segment. Names of nervules correspond to those of the tissues they innervate. The points of attachment of muscles of the fifth abdominal segment are essentially the same in both Nomia and Apis, except for the second tergo-sternal muscle which, in Nomia, has shifted its point of movable attachment to the membranous integument in front of the intersegmental membrane gland where it helps in relasing glandular secretion. The general plan of the nerves in the fifth abdominal segment in Nomia is more diffuse than in Apis, but there is no difficulty in establishing homology between the nervules of the two species. A pair of intersegmental stretch organs was found in abdominal segments 3–6. Glands of the sixth intersegmental membrane possess a reservoir with peripheral pouches both of which are absent in those of the fifth. Both types of glands have neither closing nor opening mechanisms, and neither is innervated. Release of glandular secretion is accomplished by the action of the tergo-sternal muscles.     

Development of the salivary glands in embryos of Ixodes ricinus (Acari: Ixodidae)

We examined Ixodes ricinus embryos between 18 and 28 days of development with light, scanning and transmission electron microscopy. The differences in inner structure attested to establish three successive developmental stages: days 18-20, day 23, and days 26-28. Between 18 and 20 days the embryos are at early stages of organogenesis. Salivary glands cannot be identified at that stage. In 23-day-old embryos salivary glands are already outlined but the structure of alveoles is still different from that in larvae in which the embryonic development has been completed. Gland cells start to form alveoles and become active between 26 and 28 days of the development.