Larval aggregation and competition for food in experimental populations of Chrysomya putoria (Wied.) and Cochliomyia macellaria (F.) (Dipt., Calliphoridae)

In blowflies, larval aggregation in patches of food can be both intra- and interspecific, depending upon the degree to which competitors are clumped among the patches. In the present study, the implications of spatial aggregation for larval competition was investigated in experimental populations of the introduced blowfly Chrysomya putoria and the native Cochliomyia macellaria, using data from survival to adulthood in a range of single- and double-species larval cultures. The reduction in C. macellaria survival rate in the presence of C. putoria suggests that the former species is the inferior competitor. The results on survival to adulthood for both species in single- and double-species cultures can be explained in the light of the relationship between the level of intra- and interspecific aggregation and the efficiency of the larval feeding process. The possible implications of these results for the population biology of both species in natural environments are discussed.

Toxocariasis: Serological diagnosis by indirect antibody competition elisa

Toxocariasis is caused by infection of man by Toxocara canis and Toxocara, cati larvae, the common roundworm of dogs and cats. Because larvae are difficult to detect in tissues, diagnosis is mostly based on serology. Non specific reactions are observed mainly due to cross-reactivity with Ascaris sp antigens. This investigation aimed at developing and evaluating an indirect antibody competition ELISA (IACE) employing a specific rabbit IgG anti-Toxocara canis excretory-secretory antigens as the competition antibody. in order to improve indirect ELISA specificity performed for toxocariasis diagnosis. For that, the rabbit IgG was previously absorbed by Ascaris suum adult antigens. Sensitivity and specificity of IACE were first evaluated in 28 serum samples of mice experimentally infected with T. canis embryonated eggs. Adopting cut-off value established in this population before infection, sensitivity and specificity were 100% after 20 days post-inoculation. For human population IACE was evaluated using sera from 440 patients with clinical signs of toxocariasis and the cut-off value was established with 60 serum samples from apparently healthy individuals. Using as reference test the indirect ELISA performed by Adolfo Lutz Institute, sensitivity was 60.2%, specificity was 98% and concordance was 77.3%. Repeatability of IACE was evaluated by the inter-reactions variation coefficient (2.4%).

Regression of the lateral oviducts during the larval-adult transformation of the reproductive system of Melipona quadrifasciata and Frieseomelitta varia

Toward the end of the larval phase (pre-pupa), the reproductive systems of Melipona quadrifasciata and Frieseomelitta varia workers are anatomically similar. Scanning electron microscopy showed that during this developmental phase the right and left ovaries are fused and form a heart-shaped structure located above the midgut. Each ovary is connected to the genital chamber by a long and slender lateral oviduct. During pupal development, the lateral oviducts of workers from both species become extremely reduced due to a drastic process of cell death, as shown by transmission electron microscopy. During the lateral oviduct shortening, their simple columnar epithelial cells show some signs of apoptosis in addition to necrosis. Cell death was characterized by cytoplasmic vesiculation, peculiar accumulation of glycogen, and dilation of cytoplasmic organelles such as mitochondria and rough endoplasmic reticulum. The nuclei, at first irregularly contoured, became swollen, with chromatin flocculation and various areas of condensed chromatin next to the nuclear envelope. At the end of the pupal phase, deep recesses marked the nuclei. At emergence, worker and queen reproductive systems showed marked differences, although reduction in the lateral oviducts was an event occurring in both castes. However, in queens the ovarioles increased in length and the spermatheca was larger than that of workers. At the external anatomical level, the reproductive system of workers and queens could be distinguished in the white- and pink-eyed pupal phase. The metamorphic function of the death of lateral oviduct cells, with consequent oviduct shortening, is discussed in terms of the anatomical reorganization of the reproductive system and of the ventrolateral positioning of adult worker bee ovaries. (C) 2000 Wiley-Liss, Inc.

Protein requirements in larvae and adults of Scaptotrigona postica (Hymenoptera: Apidia, Meliponinae): Midgut proteolytic activity and pollen digestion

The number and degree of digestion of pollen grains in the midgut and rectum, the midgut proteolytic activity and the time of pollen grain passage through the digestive tract in the stingless bee Scaptotrigona postica (Latreille) have been analyzed. The results show similar protein requirements among larvae, nurse bees and queens, as well as between forager bees and old males, but these requirements are higher in individuals from the former groups than in those from the latter. Although protein requirements have been demonstrated to vary according to a bee's activity in the colony, they are similar among bees from different castes or sexes. These changes in feeding behavior are related to the bee's function and to less competition for nourishment among individuals of the colony. It is also noted that pollen grains took between 6 and 28 h to pass through the digestive tract. Pollen grains are irregularly accumulated in the various regions of the midgut, which may reflect functional differentiation throughout the midgut. © 2001 Elsevier B.V.

Ultrastructure of the salivary glands of Pachycondyla (=Neoponera) villosa (Fabricius) (Formicidae: Ponerinae): Functional changes during the last larval instar

The cells of secretory region of the salivary glands of Pachycondyla (=Neoponera) villosa at the time of enzyme production presents the basal cellular membranes profusely folded and the intercellular junctional membranes present a few enlarged spaces. The rough endoplasmic reticulum and the Golgi bodies shift from being flat and small vesicular cisternae to enlarged vesicular cisternae according to the cell physiological state and characterize an asynchronic cell cycle. Enzymes are released into the lumen by microapocrine secretion. The stage of silk production is detected after a behavioral act, when the nurse worker separates the mature larva. At this time, the salivary gland cells present only one physiological state (synchronized secretory cycle): this state was characterized by basal cellular membrane poorly folded, intercellular junctions presenting some small spaces, rough endoplasmic reticulum compounded by flat cistenae, enlarged Golgi bodies with fibrous material inside and a few secretory vesicles containing silk, which undergo exocytosis. The silk in the lumen shows 2 forms: tactoid and flocculent material.

Cell nucleus activity during post-embryonic development of Apis melliferaL. (Hymenoptera: Apidae). Intranuclear acid phosphatase

We report nuclear acid phosphatase activity in the somatic (intra-ovariolar and stromatic) and germ cells of differentiating honey bee worker ovaries, as well as in the midgut cells of metamorphosing bees. There was heterogeneity in the intensity and distribution of electron dense deposits of lead phosphate, indicative of acid phosphatase activity in the nuclei of these tissues, during different phases of post-embryonic bee development. This heterogeneity was interpreted as a variation of the nuclear functional state, related to the cell functions in these tissues.

Ovarian growth during larval development of queen and worker of Apis mellifera (Hymenoptera: Apidae): a morphometric and histological study.

The present work reports the differences between the ovarian grow in queen and worker larvae of A. mellifera, from the start of differential feeding. The observations made of the growth rates in larvae of both castes showed that the queen and worker larvae have the same rates of cephalic capsule growth from one instar to another but the weight gain is greater in queens. In the same way, the draw areas of ovaries of queens increase more and continuously, while from the 5th instar on the ovaries of workers decrease in size. The decrease is due to a loss of ovariole numbers that starts early in the worker larvae and increases in the 4th-5th instar. The ovarian shape in queens and workers became different in the last larval instars.

Desenvolvimento inicial e distribuição temporal de larvas e juvenis de Bryconamericus stramineus Eigenmann, 1908 (Osteichthyes, Characidae) na planície alagável do alto rio Paraná, Brasil

The aim of this paper was to analyze initial development and temporal distribution of larvae and juveniles of Bryconamericus stramineus and their relationship with some environmental variables of Ressaco do Leopoldo in the Upper Paraná River floodplain. The samples were taken from February 1991 to February 1992. The larvae and the juveniles were identified and described according to the with its morphologic and meristic characteristics. The larvae presented scarce pigmentation, subterminal mouth, medium anal opening and myomeres varying 35-40 (16-21 pre and IT-22 postanal). The greater densities of larvae and juveniles were verified in December 1991 and November 1991, respectively, mainly during the night. The larvae density was only correlated with precipitation.

Ultrastructural and Cytochemical Aspects of Metamorphosis in the Midgut of Apis mellifera L. (Hymenoptera: Apidae: Apinae)

The midgut of Apis mellifera is remodeled during metamorphosis. The epithelium and, to a lesser extent, the muscular sheath degenerate between the end of the last larval instar and the onset of pupation (prepupa).The larval epithelium is shed to the midgut lumen and digested, while a new epithelium is reconstructed from larval regenerative cells. During pupation, some reorganization still occurs, mainly in brown-eyed pupae. In pharate adult, the midgut wall shows the characteristics of adult, although some cells have pycnotic nuclei. The localization of alkaline and acid phosphatases showed that these enzymes were not involved in the reabsorption of the midgut wall.

Variation of genetic expression during development, revealed by esterase patterns in Aedes aegypti (Diptera, Culicidae)

Polyacrylamide gel electrophoresis was used to analyze esterase patterns during development of Aedes aegypti from the cities of Marília and São José do Rio Preto (SJRP), Brazil. The zymograms showed a total of 23 esterase bands, 22 of which were in the specimens from Marília and 19 in those from SJRP. These esterase bands were considered to be the product of 23 alleles distributed tentatively in eight genetic loci. Most of the alleles were developmentally regulated. The larval stage expressed the greatest number of them (19 alleles, from the eight loci, in Marília; and 17 alleles, from seven loci, in SJRP). The pupal stage expressed 10 alleles from seven loci, in both populations, and the adult stage expressed 8 alleles from five and six loci in SJRP and Marília, respectively. Some alleles that were active in every stage were developmentally controlled at the level of expression (amount of product). A single allele was constitutively and highly expressed, in larvae, pupae, and adults, in both populations. Differences in esterase synthesis among stages are probably due to regulatory mechanisms acting in agreement with the requirements of a variable number of processes in which esterases are involved. The larval stage is the most active in developmental processes and shows very intense intake of food and very high mobility. These features may demand increased esterase production at that stage. Comparison of the two populations examined showed (besides the existence of alleles that they do not share) that they exhibit differences in the control of expression of other alleles. Such findings may reflect genetic differences between founders in each population, but the possibility of involvement of the intensive use of insecticides in SJRP is also discussed.

Male behavior in colonies of the social wasp Polistes lanio (Hymenoptera, Vespidae)

Sixteen post-emergent colonies of Polistes lanio were studied while producing males in the course of the colonial cycle. Individually, they remained in the nest only 10.5 days (5-31, n=165). Twelve different male behaviors were observed: remaining immobile on the nest (82,8%), giving alarm (4,8%), flying out from the nest (2,4%), copulating on the nest (2,4%), being dominated (1,6%), self-grooming (1,2%), checking cells (1,2%), adult-adult trophallaxis (receiving food) (0,8%), larva-adult trophallaxis (0,8%), chewing prey and giving it to the larvae (0,8%), returning to the nest without food (0,8%), and fanning the nest (0,4%). In comparison to the behavioral repertory of females (28 items), they performed fewer tasks and remained immobile most of the time on the nest. Their behavior was largely related to self maintenance, but also included giving chewed prey to the larvae, giving alarm signals and fanning the nest.

Dynamics of handling time and functional response by larvae of Chrysomya albiceps (Dipt., Calliphoridae) on different prey species

One way to understand the behavioural patterns exhibited by a predator in response to prey density is to evaluate its functional response. Such evaluation yields information about basic mechanisms of prey-predator dynamics, and is an essential component of prey-predator models. In this paper we analysed experimentally the functional response and the handling time spent by Chrysomya albiceps on different prey species and larval instars of blowflies. The type II functional response was observed when second instar larvae of Chrysomya megacephala and Chrysomya macellaria were consumed. The handling time spent by the predator was significantly different between instars and species. The implications of the functional response and handling time for the interaction dynamics of Brazilian Chrysomyinae species are discussed.

Cloning and characterization of the cDNA for the Brazilian Cratomorphus distinctus larval firefly luciferase: Similarities with European Lampyris noctiluca and Asiatic Pyrocoelia luciferases

Studies on firefly (Lampyridae) luciferases have focused on nearctic species of Photinus and Photuris and Euroasiatic species of Lampyris, Luciola, Hotaria, and Pyrocoelia. Despite accounting for the greatest diversity of fireflies in the world, no molecular studies have been carried out on the highly diverse genera from the neotropical region. Here we report the luciferase cDNA cloning for the larva of the Brazilian firefly Cratomorphus distinctus. The cDNA has 1978 bp and codes for a 547-residue-long polypeptide. Noteworthy, sequence comparison as well as functional properties show the highest degree of similarity with Lampyris noctiluca (93%) and Pyrocoelia spp. (91%) luciferases, suggesting a close phylogenetic relationship despite the geographical distance separating these species. The bioluminescence emission spectrum peaks at 550 nm and, as expected, is sensitive to pH, shifting to 605 nm at pH 6. The kinetic properties of the recombinant luciferase were similar to those of other firefly luciferases. © 2004 Elsevier Inc. All rights reserved.

Macromolecular array patterns of silk gland secretion in social Hymenoptera larvae

The cocoon, produced by most holometabolous insects, is built with silk that is usually produced by the larval salivary gland. Although this silk has been widely studied in the Lepidoptera, its composition and macromolecular arrangement remains unknown in the Hymenoptera. The macromolecular array patterns of the silk in the larval salivary gland of some meliponids, wasps, and ants were analyzed with polarized-light microscopy, and they were compared with those of Bombyx mori (Lepidoptera). There is a birefringent secretion in the glandular lumen of all larvae, due to filamentous structural proteins that display anisotropy. The silk in the distal, middle and proximal regions of the secretory portion of Formicidae and Vespidae glands presented a lattice optical pattern. We found a different pattern in the middle secretory portion of the Meliponini, with a zigzag rather than a lattice pattern. This indicates that the biopolymer fibers begin their macromolecular reorganization at this glandular region, different from the Formicidae and the Vespidae, in which the zigzag optical pattern was only found at the lateral duct. Probably, the mechanism of silk production in the Hymenoptera is a characteristic inherited from a common ancestor of Vespoidea and Sphecoidea; the alterations in the pattern observed in the Meliponini could be a derived characteristic in the Hymenoptera. We found no similarity in the macromolecular reorganization patterns of the silk between the Hymenoptera species and the silkworm.