Plastic and evolutionary responses of cell size and number to larval malnutrition in Drosophila melanogaster.

Both development and evolution under chronic malnutrition lead to reduced adult size in Drosophila. We studied the contribution of changes in size vs. number of epidermal cells to plastic and evolutionary reduction of wing size in response to poor larval food. We used flies from six populations selected for tolerance to larval malnutrition and from six unselected control populations, raised either under standard conditions or under larval malnutrition. In the control populations, phenotypic plasticity of wing size was mediated by both cell size and cell number. In contrast, evolutionary change in wing size, which was only observed as a correlated response expressed on standard food, was mediated entirely by reduction in cell number. Plasticity of cell number had been lost in the selected populations, and cell number did not differ between the sexes despite males having smaller wings. Results of this and other experimental evolution studies are consistent with the hypothesis that alleles which increase body size through prolonged growth affect wing size mostly via cell number, whereas alleles which increase size through higher growth rate do so via cell size.

Characterisation of Culex quinquefasciatus (Diptera: Culicidae) larval habitats at ground level and temporal fluctuations of larval abundance in Córdoba, Argentina

The aims of this study were to characterise the ground-level larval habitats of the mosquito Culex quinquefasciatus, to determine the relationships between habitat characteristics and larval abundance and to examine seasonal larval-stage variations in Córdoba city. Every two weeks for two years, 15 larval habitats (natural and artificial water bodies, including shallow wells, drains, retention ponds, canals and ditches) were visited and sampled for larval mosquitoes. Data regarding the water depth, temperature and pH, permanence, the presence of aquatic vegetation and the density of collected mosquito larvae were recorded. Data on the average air temperatures and accumulated precipitation during the 15 days prior to each sampling date were also obtained. Cx. quinquefasciatus larvae were collected throughout the study period and were generally most abundant in the summer season. Generalised linear mixed models indicated the average air temperature and presence of dicotyledonous aquatic vegetation as variables that served as important predictors of larval densities. Additionally, permanent breeding sites supported high larval densities. In Córdoba city and possibly in other highly populated cities at the same latitude with the same environmental conditions, control programs should focus on permanent larval habitats with aquatic vegetation during the early spring, when the Cx. quinquefasciatus population begins to increase.

A comparison of larval, ovitrap and MosquiTRAP surveillance for Aedes (Stegomyia) aegypti

In Brazil, the entomological surveillance of Aedes (Stegomyia) aegypti is performed by government-mandated larval surveys. In this study, the sensitivities of an adult sticky trap and traditional surveillance methodologies were compared. The study was performed over a 12-week period in a residential neighbourhood of the municipality of Pedro Leopoldo, state of Minas Gerais, Brazil. An ovitrap and a MosquiTRAP were placed at opposite ends of each neighbourhood block (60 traps in total) and inspections were performed weekly. The study revealed significant correlations of moderate strength between the larval survey, ovitrap and MosquiTRAP measurements. A positive relationship was observed between temperature, adult capture measurements and egg collections, whereas precipitation and frequency of rainy days exhibited a negative relationship.

She’s a femme fatale: low-density larval development produces good disease vectors

Two hypotheses for how conditions for larval mosquitoes affect vectorial capacity make opposite predictions about the relationship of adult size and frequency of infection with vector-borne pathogens. Competition among larvae produces small adult females. The competition-susceptibility hypothesis postulates that small females are more susceptible to infection and predicts frequency of infection should decrease with size. The competition-longevity hypothesis postulates that small females have lower longevity and lower probability of becoming competent to transmit the pathogen and thus predicts frequency of infection should increase with size. We tested these hypotheses for Aedes aegypti in Rio de Janeiro, Brazil, during a dengue outbreak. In the laboratory, longevity increases with size, then decreases at the largest sizes. For field-collected females, generalised linear mixed model comparisons showed that a model with a linear increase of frequency of dengue with size produced the best Akaike’s information criterion with a correction for small sample sizes (AICc). Consensus prediction of three competing models indicated that frequency of infection increases monotonically with female size, consistent with the competition-longevity hypothesis. Site frequency of infection was not significantly related to site mean size of females. Thus, our data indicate that uncrowded, low competition conditions for larvae produce the females that are most likely to be important vectors of dengue. More generally, ecological conditions, particularly crowding and intraspecific competition among larvae, are likely to affect vector-borne pathogen transmission in nature, in this case via effects on longevity of resulting adults. Heterogeneity among individual vectors in likelihood of infection is a generally important outcome of ecological conditions impacting vectors as larvae.

New classification of natural breeding habitats for Neotropical anophelines in the Yanomami Indian Reserve, Amazon Region, Brazil and a new larval sampling methodology

Here we present the first in a series of articles about the ecology of immature stages of anophelines in the Brazilian Yanomami area. We propose a new larval habitat classification and a new larval sampling methodology. We also report some preliminary results illustrating the applicability of the methodology based on data collected in the Brazilian Amazon rainforest in a longitudinal study of two remote Yanomami communities, Parafuri and Toototobi. In these areas, we mapped and classified 112 natural breeding habitats located in low-order river systems based on their association with river flood pulses, seasonality and exposure to sun. Our classification rendered seven types of larval habitats: lakes associated with the river, which are subdivided into oxbow lakes and nonoxbow lakes, flooded areas associated with the river, flooded areas not associated with the river, rainfall pools, small forest streams, medium forest streams and rivers. The methodology for larval sampling was based on the accurate quantification of the effective breeding area, taking into account the area of the perimeter and subtypes of microenvironments present per larval habitat type using a laser range finder and a small portable inflatable boat. The new classification and new sampling methodology proposed herein may be useful in vector control programs.

Immunohistochemical expression of fibronectin and C5b-9 in the myocardium in cases of carbon monoxide poisoning.

Even if there is clinical evidence that carbon monoxide poisoning determines cardiac damage, the literature on the cardiac pathomorphology in such cases is scarce. We investigated the immunohistochemical expression of two known markers of fresh cardiac damage, fibronectin and the terminal complement complex C5b-9, in both cardiac ventricles in 26 cases of CO intoxication (study group, 15 ♀, 11 ♂, mean age 47 years, mean COHb level 65.9%, min. 51%, max. 85%) compared to a group of 23 cases of hanging (n = 23, 4♀, 19♂, mean age 42 years) as well as to 25 cases of myocardial infarction (n = 25, 13♀, 12♂, mean age 64 years). Fresh cardiac damage was detected with the antibody fibronectin in cases of CO poisoning and was prevalently localised at the right ventricle.

Life-history consequences of adaptation to larval nutritional stress in Drosophila.

Many animal species face periods of chronic nutritional stress during which the individuals must continue to develop, grow, and/or reproduce despite low quantity or quality of food. Here, we use experimental evolution to study adaptation to such chronic nutritional stress in six replicate Drosophila melanogaster populations selected for the ability to survive and develop within a limited time on a very poor larval food. In unselected control populations, this poor food resulted in 20% lower egg-to-adult viability, 70% longer egg-to-adult development, and 50% lower adult body weight (compared to the standard food on which the flies were normally maintained). The evolutionary changes associated with adaptation to the poor food were assayed by comparing the selected and control lines in a common environment for different traits after 29-64 generations of selection. The selected populations evolved improved egg-to-adult viability and faster development on poor food. Even though the adult dry weight of selected flies when raised on the poor food was lower than that of controls, their average larval growth rate was higher. No differences in proportional pupal lipid content were observed. When raised on the standard food, the selected flies showed the same egg-to-adult viability and the same resistance to larval heat and cold shock as the controls and a slightly shorter developmental time. However, despite only 4% shorter development time, the adults of selected populations raised on the standard food were 13% smaller and showed 20% lower early-life fecundity than the controls, with no differences in life span. The selected flies also turned out less tolerant to adult malnutrition. Thus, fruit flies have the genetic potential to adapt to poor larval food, with no detectable loss of larval performance on the standard food. However, adaptation to larval nutritional stress is associated with trade-offs with adult fitness components, including adult tolerance to nutritional stress.

Larval endoparasitoids (Hymenoptera) of frugivorous flies (Diptera, Tephritoidea) reared from fruits of the cerrado of the State of Mato Grosso do Sul , Brazil

This paper presents a five years survey of endoparasitoids obtained from the larvae of frugivorous Tephritidae and Lonchaeidae flies. The insects were reared from cultivated and wild fruits collected in areas of the cerrado in the State of Mato Grosso do Sul, Brazil. The flies obtained from 14 host fruit species were eight Anastrepha species, Ceratitis capitata (Wiedemann, 1824) (Tephritidae); Dasiops sp. and Neosilba spp. (Lonchaeidae). Eleven parasitoid species were collected: Braconidae - Asobara anastrephae (Muesebek, 1958), Doryctobracon areolatus (Szépligeti, 1911), D. fluminensis (Costa Lima, 1938), Opius bellus Gahan, 1930 and Utetes anastrephae (Viereck, 1913); Figitidae - Aganaspis nordlanderi Wharton, 1998, Lopheucoila anastrephae (Rhower, 1919), Odontosema anastrephae (Borgmeier, 1935) and Trybliographa infuscata Gallardo, Díaz & Uchôa-Fernandes, 2000 and, Pteromalidae - Spalangia gemina Boucek, 1963 and S. endius Walker, 1839. In all cases only one parasitoid emerged per puparium. D. areolatus was the most abundant and frequent parasitoid of fruit fly species, as was L. anastrephae in Neosilba spp. larvae. This is the first record of A. nordlanderi in the midwestern Brazilian region.

Estudo da dispersão larval radial pós-alimentar em Chrysomya megacephala (Fabricius) (Diptera, Calliphoridae)

Blowflies utilize discrete and ephemeral sites for breeding and larval nutrition. After the exhaustion of food, the larvae begin dispersing to search for sites to pupate or to additional food source, process referred as postfeeding larval dispersal. Some of the most important aspects of this process were investigated in Chrysomya megacephala, utilizing a circular arena to permit the radial dispersion of larvae from the center. To determinate the localization of each pupa, the arena was split in 72 equal sectors from the center. For each pupa, distance from the center of arena, weight and depth were determined. Statistical tests were performed to verify the relation among weight, depth and distance of burying for pupation. It was verified that the larvae that disperse farther are those with higher weights. The majority of individuals reached the depth of burying for pupation between 7 and 18 cm. The study of this process of dispersion can be utilized in the estimation of postmortem interval (PMI) for human corpses in medico-criminal investigations.

Nutritional ecology of blowflies (Diptera, Calliphoridae): estimates of critical larval weight for pupation on two different

Under natural environmental conditions, blowflies utilize discrete and ephemeral feeding resources such as decaying carcasses. Competition for food on such feeding substrates is usually very severe, and only the individuals that are capable of attaining the critical larval weight for pupation will be able to survive. This critical weight is hitherto unknown for several blowfly species; therefore, the current work is aimed at obtaining such a critical value for four blowfly species of the genera Chrysomya and Lucilia, deploying two types of feeding substrate, namely, artificial diet and macerated bovine meat. On the whole, the critical weights ranged from 30 to 35 mg. The lowest larval weight which permitted pupation was 30.0 mg for Chrysomya megacephala reared on macerated bovine meat. This species was also the best adapted to pupation at low larval weights in relation to the maximum larval weight for males. Regarding the pupation of females, the best-adapted individual was a C. albiceps specimen exhibiting a critical weight that was equal to 39.20 % of the maximum value obtained. Concerning all the species and diet types, the female individuals exhibited the lowest critical weights that produced viable pupae, probably representing an evolutionary strategy that favoured the survival of females, responsible for the egg formation, contributing to the establishment of future generations. Regarding the loss (in percentage) of adult biomass in relation to the third instar larvae, the females of C. megacephala lost less weight than males in both feeding substrates. On the other hand, such a loss of weight occurred in males of C. albiceps and L. cuprina.

Can larval lacewings Chrysoperla externa (Hagen): (Neuroptera, Chrysopidae) be reared on pollen?

The aim of this study was to verify the viability of exclusive use of elephant grass pollen, Pennisetum purpureum (Schum), to feed larvae of the lacewing Chrysoperla externa (Hagen, 1861). The insects were kept at 24ºC and the duration and survival rate of each instar and the larval and pupal phases were recorded. The diet provided complete development of the larvae. The average duration of the first and second instars was the same (6.9 days), while the third instar lasted an average of 10.0 days and the pupal phase 13.2 days. The average survival of the larvae was above 80% for the first, second and third instars, and 70.0% and 33.3% for the larval and pupal phase, respectively. These results indicate that the exclusive use of elephant grass pollen can provide complete development of the immature stages of this predator.

Monitoreo larval y captación de semilla de la Concha de Abanico (Argopecten purpuratus) en la Bahía Paracas, Perú, durante 1984-85

Entre setiembre de 1984 y febrero de 1985 se determinó las concentraciones de larvas en 3 estaciones en la Bahía de Paracas. Simultáneamente se registró la temperatura superficial del agua, se calculó el índice gonadal de la Concha de Abanico y se captó semillas.

Bionomic data and larval density of Scarabaeidae (Pleurosticti) in sugarcane in the central region of Mato Grosso do Sul, Brazil

Bionomic data and larval density of Scarabaeidae (Pleurosticti) in sugarcane in the central region of Mato Grosso do Sul, Brazil. Phytophagous larvae of Scarabaeidae cause damage to diverse crops. Information on these pests is scarce; therefore, the objective of this study was to determine biological aspects and larval density of species occurring in an area of sugarcane. The studies were developed in Sidrolândia from April 2009 to March 2010. Scarab beetle larvae were collected in sugarcane roots every fifteen days, taken to the laboratory and reared to obtain the adults and determine biological parameters. A total of 2,656 larvae were collected, being 162 Liogenys fuscus, 120 Cyclocephala verticalis, 37 Cyclocephala forsteri, and 2337 Anomonyx sp. In January, 53.65 larvae m-2 were obtained, and the most abundant species was Anomonyx sp, representing 87.99% of the total larvae collected. From November to March, the greatest densities of Anomonyx were observed in the field. The adults of this species occurred from May to September, and egg laying from September to November. Eggs measured 1.1 x 1.7 mm, and incubation period last 15.4 days. First instar larvae were observed mainly in October; second instar larvae from November to April; and third instar from January to July. Pupae were observed from May to August. The most abundant scarab beetle, Anomonyx sp. in roots of sugarcane presents one generation per year in Sidrolândia, MS.

Description of the third larval instar and pupa of Geniates barbatus Kirby (Coleoptera, Scarabaeidae, Rutelinae)

Description of the third larval instar and pupa of Geniates barbatus Kirby (Coleoptera, Scarabaeidae, Rutelinae). The last larval instar and pupa of the Neotropical Geniatini Geniates barbatus Kirby, 1819 are described and illustrated. Biological notes and a key to the third instar larvae of Neotropical Rutelinae are also provided.

New method for rearing Spodoptera frugiperda in laboratory shows that larval cannibalism is not obligatory

New method for rearing Spodoptera frugiperda in laboratory shows that larval cannibalism is not obligatory. Here we show, for the first time, that larvae of the fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera, Noctuidae), can be successfully reared in a cohort-based manner with virtually no cannibalism. FAW larvae were reared since the second instar to pupation in rectangular plastic containers containing 40 individuals with a surprisingly ca. 90% larval survivorship. Adult females from the cohort-based method showed fecundity similar to that already reported on literature for larvae reared individually, and fertility higher than 99%, with the advantage of combining economy of time, space and material resources. These findings suggest that the factors affecting cannibalism of FAW larvae in laboratory rearings need to be reevaluated, whilst the new technique also show potential to increase the efficiency of both small and mass FAW rearings.