Reproductive performance of the generalist predator Hypoaspis aculeifer (Acari : Gamasida) when foraging on different invertebrate prey

In this study, we assessed the influence of prey quality and prey biomass during a standardized 3-week test on adult survival and reproductive output of the predatory mite Hypoaspis aculeifer when fed one of six different diets: springtails (Folsomia candida and Folsomia fimetaria), a storage mite (Caloglyphus cf. michaeli), an oligochaete (Enchytraeus crypticus), a nematode (Turbatrix silusiae), and a 1:1:1 mix of F. candida:F.fimetaria:E. crypticus. Our results revealed that a single prey species may be nutritionally sufficient for a 3-week period, as H. aculeifer performed equally well, or better, on a diet based on a 1:1:1 mix of F. candida:F. fimetaria:E. crypticus. However, when fed C. cf. michaeli, H. aculeifer had a poor reproductive output (< 200 juveniles) and a reduced survival (60-70%). Thus, investigators should validate their choice of prey prior to testing H. aculeifer performance during toxicant exposure. (c) 2007 Elsevier B.V. All rights reserved.

Efeito da densidade de ninfas de Aphis gossypii Glover, 1877 (Hemiptera, Aphididae) no consumo alimentar e aspectos biológicos de Orius insidiosus (Say, 1832) (Hemiptera, Anthocoridae)

Effect of ninfal density of Aphis gossypii Glover, 1877 (Hemiptera, Aphididae) on feed consumption and biological aspects of Orius insidiosus (Say, 1832) (Hemiptera, Anthocoridae). The influence of different densities of A. gossypii (10, 20, 30, 40, 50, 60 nymphs/day) on consumption rate, development time, survival, and reproduction of Orius insidiosus (Say, 1832) was investigated. The trials were carried out in climatic chamber at 25 ± 1 °C, 70±10% RH, and photoperiod 12:12h (L:D). Consumption rates of nymphs and adults increased under a linear form as the densities of aphids increased. Development time was longest when reared in 10 nymphs density (15.4 days). Nymphal survival was different under the densities of A. gossypii and no significant difference for the periods of preoviposition (4.8 days) and oviposition (8.9 days) were found. The oviposition increased with the prey densities (2.00, 11.33, 10.67, 21.30, 17.89 and 53.38 eggs), as well as the viability: 0.00, 52.49, 57.86, 58.14, 50.11 and 72.89%, respectively. Nymphs of A. gossypii as prey were suitable for the complete development of O. insidiosus.

Necrophagous diptera associated with wild animal carcasses in southern Brazil

Necrophagous Diptera associated with wild animal carcasses in southern Brazil. The aim of this study was to acquire a better knowledge concerning the diversity of necrophagous Diptera that develop on wild animal carcasses. For this purpose, the decomposition of six wild animal carcasses was observed in order to collect and identify the main species of necrophagous flies associated with the decomposition process. The carcasses were found on highways near the cities of Pelotas and Capão do Leão in the initial stage of decomposition, with no significant injuries or prior larval activity. Four wild animal models were represented in this study: two specimens of Didelphis albiventris Lund, 1840; two Tupinambis merianae Linnaeus, 1758; one Nothura maculosa Temminck, 1815; and one Cerdocyon thous Linnaeus, 1766. A total of 16,242 flies from 14 species were reared in the laboratory, where Muscidae presented the greatest diversity of necrophagous species. Overall, (i) carcasses with larger biomass developed a higher abundance of flies and (ii) the necrophagous community was dominated by Calliphoridae, two patterns that were predicted from published literature; and (iii) the highest diversity was observed on the smaller carcasses exposed to the lowest temperatures, a pattern that may have been caused by the absence of the generalist predator Chrysomya albiceps (Wiedemann, 1819). (iv) An UPGMA analysis revealed a similar pattern of clusters of fly communities, where the same species were structuring the groupings.

Does the Ingestion of Isoxaflutole Herbicide Affect the Midgut and Salivary Glands of Pentatomidae Predators?

Podisus nigrispinus is a generalist predator naturally occurring in agricultural and forestry systems that effectively contributes to the population balance of phytophagous insects, especially defoliating caterpillars. Histological changes were evaluated in the salivary glands and midgut of P. nigrispinus caused by ingestion of systemic herbicide isoxaflutole. These predator females were fed with leaves of eucalyptus plants, Tenebrio molitor pupae or water, contaminated or not by herbicide. Salivary glands and midguts were dissected, processed and analyzed under a light microscope. Activity level and cell morphology of the salivary glands and midgut showed differences among insects fed on plants, contaminated water or pupae. The epithelia of the salivary gland and midgut of individuals which had no contact with the herbicide showed homogeneous cytoplasm, nucleus with predominance of decondensed chromatin and evident nucleoli, intense cell activity features. As for the insects in contact with contaminated food, they presented undeveloped nucleus and condensed chromatin. The luminal contents of the salivary glands in the contaminated insects had become more acidophilus than in insects without poisoning, as well as having heterogeneous and granular secretion, being more evident in the bioassay in which the insects fed on contaminated water. There was a marked morphological change in the midgut cells in contaminated insects. High degree of apoptosis, disorganization and secretory vacuoles in the epithelial cytoplasm were observed. The apical portion of the midgut cells proved undeveloped, irregular and partially destroyed. It is concluded that isoxaflutole causes morphological changes in the digestive system of the predator P. nigrispinus.

Diet and Spatial Pattern of Foraging in Ectatomma opaciventre (Hymenoptera: Formicidae) in an Anthropic Area

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Ecologia alimentar das quatro espécies dominantes da anurofauna de serapilheira em um gradiente altitudinal na ilha de São Sebastião, SP

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

(Table 1) Stable carbon and nitrogen isotopic ratios of potential prey species of bearded seals (Erignathus barbatus), Svalbard

Changing patterns of sea-ice distribution and extent have measurable effects on polar marine systems. Beyond the obvious impacts of key-habitat loss, it is unclear how such changes will influence ice-associated marine mammals in part because of the logistical difficulties of studying foraging behaviour or other aspects of the ecology of large, mobile animals at sea during the polar winter. This study investigated the diet of pregnant bearded seals (Erignathus barbatus) during three spring breeding periods (2005, 2006 and 2007) with markedly contrasting ice conditions in Svalbard using stable isotopes (d13C and d15N) measured in whiskers collected from their newborn pups. The d15N values in the whiskers of individual seals ranged from 11.95 to 17.45 per mil, spanning almost 2 full trophic levels. Some seals were clearly dietary specialists, despite the species being characterised overall as a generalist predator. This may buffer bearded seal populations from the changes in prey distributions lower in the marine food web which seems to accompany continued changes in temperature and ice cover. Comparisons with isotopic signatures of known prey, suggested that benthic gastropods and decapods were the most common prey. Bayesian isotopic mixing models indicated that diet varied considerably among years. In the year with most fast-ice (2005), the seals had the greatest proportion of pelagic fish and lowest benthic invertebrate content, and during the year with the least ice (2006), the seals ate more benthic invertebrates and less pelagic fish. This suggests that the seals fed further offshore in years with greater ice cover, but moved in to the fjords when ice-cover was minimal, giving them access to different types of prey. Long-term trends of sea ice decline, earlier ice melt, and increased water temperatures in the Arctic are likely to have ecosystem-wide effects, including impacts on the forage bases of pagophilic seals.

Do predators aggregate in response to pest density in agroecosystems? Assessing within-field spatial patterns

1. The spatial heterogeneity of predator populations is an important component of ecological theories pertaining to predator-prey dynamics. Most studies within agricultural fields show spatial correlation (positive or negative) between mean predator numbers and prey abundance across a whole field over time but generally ignore the within-field spatial dimension. We used explicit spatial mapping to determine if generalist predators aggregated within a soybean field, the size of these aggregations and if predator aggregation was associated with pest aggregation, plant damage and predation rate. 2. The study was conducted at Gatton in the Lockyer Valley, 90 km west of Brisbane, Australia. Intensive sampling grids were used to investigate within-field spatial patterns. The first row of each grid was located in a lucerne field (10 m from interface) and the remaining rows were in an adjacent soybean field. At each point on the grid the abundance of foliage-dwelling and ground-dwelling pests and predators was measured, predation rates [using sentinel Helicoverpa armigera (Hubner) egg cards] and plant damage were estimated. Eight grids were sampled across two summer cropping seasons (2000/01, 2001/02). 3. Predators exhibited strong spatial patterning with regions of high and low abundance and activity within what are considered to be uniform soybean fields. Ground-dwelling and foliage-dwelling predators were often aggregated in patches approximately 40 m across. 4. Lycosidae (wolf spiders) displayed aggregation and were consistently more abundant within the lucerne, with a decreasing trap catch with distance from the lucrene/soybean interface. This trend was consistent between subsequent grids in a single field and between fields. 5. The large amount of spatial variability in within-field arthropod abundance (pests and predators) and activity (egg predation and plant damage) indicates that whole field averages were misleading. This result has serious implications for sampling of arthropod abundance and pest management decision-making based on scouting data. 6. There was a great deal of temporal change in the significant spatial patterns observed within a field at each sampling time point during a single season. Predator and pest aggregations observed in these fields were generally not stable for the entire season. 7. Predator aggregation did not correlate consistently with pest aggregation, plant damage or predation rate. Spatial patterns in predator abundance were not associated consistently with any single parameter measured. The most consistent positive association was between foliage-dwelling predators and pests (significant in four of seven grids). Inferring associations between predators and prey based on an intensive one-off sampling grid is difficult, due to the temporal variability in the abundance of each group. 8. Synthesis and applications. This study demonstrated that generalist predator populations are rarely distributed randomly and field edges and adjacent crops can have an influence on within-field predator abundance. This must be considered when estimating arthropod (pest and predator) abundance from a set of samples taken at random locations within a field.

DNA barcoding identifies a cosmopolitan diet in the ocean sunfish

The ocean sunfish (Mola mola) is the world’s heaviest bony fish reaching a body mass of up to 2.3 tonnes. However, the prey M. mola consumes to fuel this prodigious growth remains poorly known. Sunfish were thought to be obligate gelatinous plankton feeders, but recent studies suggest a more generalist diet. In this study, through molecular barcoding and for the first time, the diet of sunfish in the north-east Atlantic Ocean was characterised. Overall, DNA from the diet content of 57 individuals was successfully amplified, identifying 41 different prey items. Sunfish fed mainly on crustaceans and teleosts, with cnidarians comprising only 16% of the consumed prey. Although no adult fishes were sampled, we found evidence for an ontogenetic shift in the diet, with smaller individuals feeding mainly on small crustaceans and teleost fish, whereas the diet of larger fish included more cnidarian species. Our results confirm that smaller sunfish feed predominantly on benthic and on coastal pelagic species, whereas larger fish depend on pelagic prey. Therefore, sunfish is a generalist predator with a greater diversity of links in coastal food webs than previously realised. Its removal as fisheries’ bycatch may have wider reaching ecological consequences, potentially disrupting coastal trophic interactions.

DNA barcoding identifies a cosmopolitan diet in the ocean sunfish

The ocean sunfish (Mola mola) is the world’s heaviest bony fish reaching a body mass of up to 2.3 tonnes. However, the prey M. mola consumes to fuel this prodigious growth remains poorly known. Sunfish were thought to be obligate gelatinous plankton feeders, but recent studies suggest a more generalist diet. In this study, through molecular barcoding and for the first time, the diet of sunfish in the north-east Atlantic Ocean was characterised. Overall, DNA from the diet content of 57 individuals was successfully amplified, identifying 41 different prey items. Sunfish fed mainly on crustaceans and teleosts, with cnidarians comprising only 16% of the consumed prey. Although no adult fishes were sampled, we found evidence for an ontogenetic shift in the diet, with smaller individuals feeding mainly on small crustaceans and teleost fish, whereas the diet of larger fish included more cnidarian species. Our results confirm that smaller sunfish feed predominantly on benthic and on coastal pelagic species, whereas larger fish depend on pelagic prey. Therefore, sunfish is a generalist predator with a greater diversity of links in coastal food webs than previously realised. Its removal as fisheries’ bycatch may have wider reaching ecological consequences, potentially disrupting coastal trophic interactions.

Contribuição para a avaliação da dieta do golfinho-comum (Delphinus delphis) na costa continental portuguesa

O golfinho-comum (Delphinus delphis) é uma das espécies de cetáceos mais abundantes e mais amplamente distribuídas em todo o planeta, sendo a espécie mais abundante ao longo da costa continental portuguesa. Algumas das suas principais presas apresentam um elevado interesse comercial estando por isso, muitas vezes, associado a capturas acidentais em artes de pesca. Contudo, estudos mais recentes sobre os hábitos alimentares desta espécie na costa portuguesa são escassos. Assim, este estudo visa contribuir para a avaliação da ecologia alimentar deste cetáceo na costa portuguesa através de índices de importância numérica, ocorrência e do peso estimado, permitindo descrever a dieta não só em termos qualitativos, mas também em termos quantitativos. Foram examinados os conteúdos estomacais de 55 golfinhoscomuns arrojados na costa continental portuguesa (norte e centro) entre 2004 e 2015. De um total de 6699 presas identificadas, 66% pertenciam à classe dos peixes, 32% eram cefalópodes e 3% eram crustáceos. As espécies-presa de peixes mais importantes em termos de importância numérica foram os góbios (Gobiidae) e o carapau (Trachurus sp.). Em relação à ocorrência foram o góbio (Gobiidae) e a sardinha (Sardina pilchardus), seguidas de carapau, as espécies predominantes. Relativamente ao peso, a sardinha foi a espécie-presa predominante, seguida de faneca (Trisopterus luscus) e carapau. Quanto aos cefalópodes, a lula-bicuda (Alloteuthis sp.) foi a espécie mais importante, tanto em termos de importância numérica como em termos de ocorrência. A lula-comum (Loligo sp.) foi a mais importante em termos de peso total estimado. As espécies demersais dominaram a dieta do golfinho-comum, com uma percentagem numérica de 40%. Foram detetadas diferenças entre machos e fêmeas na composição da dieta relativamente à sardinha. Foram detetadas diferenças entre indivíduos maturos e imaturos na composição da dieta relativamente à lula-bicuda. A diversidade de presas observada nos conteúdos estomacais do golfinho-comum sugere um comportamento oportunista, consumindo as presas mais abundantes, localmente. As interações com as artes de pesca podem levar a uma elevada mortalidade destes mamíferos marinhos. Deste modo, a realização de estudos sobre os hábitos alimentares de cetáceos permitem uma melhor compreensão das possíveis interações com a pesca, e a melhoria de estratégias de conservação para evitar a morte destes animais.

Ecología trófica del pulpo Octopus mimus Gould 1852 (Cephalopoda: Octopodidae) invierno 2013-2014 en la bahía del Callao

El pulpo Octopus mimus es un importante recurso de la pesquería artesanal bentónica, que se distribuye desde el norte del Perú a San Vicente, Chile. Se analizaron contenidos gástricos de 741 ejemplares obtenidos de la captura comercial en la bahía del Callao, durante agosto 2013-agosto 2014. Se determinó que las presas más importantes fueron crustáceos Decapoda: Petrolisthes desmarestii (%FO=24,13; %P=21,29%; N=27,10), Cycloxanthops sexdecimdentatus (%FO=16,35; %P=12,16%; N=15,99) y Allopetrolisthes angulosus (%FO=6,17; %P=6,05; %N=25,20). No hubo diferencias en la dieta entre machos y hembras en %FO y %P (Mann -Whitney U-test, p>0,05). Se observaron diferencias en el IR asociado a las fases de desarrollo gonadal en hembras, ejemplares madurantes/maduros mostraron mayor IR (0,17±0,17) que los desovados (0,08± 0,06), en machos no se observaron diferencias. El IR fue mayor en otoño (0,21±0,17) (Kruskal-Wallis test, p < 0,05). Los índices ecológicos mostraron que O. mimus es un depredador generalista (B’>3), observándose traslapo entre la dieta de machos y hembras (Cλ>0,6), por lo que se concluye que su alimentación está influenciada por una combinación de factores fisiológicos y ambientales.

Host plant specificity in several species of generalist mite predators

1. Species in the genus Neoseiulus are considered to be generalist predators. with some species used in biological control programmes against phytophagous mites and insects. 2. A general survey of Neoseiulus species in inland Australia indicated that different species are associated with particular tree species. This pattern of host plant use was investigated for four Neoseiulus species (N. buxeus, N. cappari, N. brigarinus, N. eremitus) by means of a sampling programme through time and across space. 3. Each species of Neoseiulus was collected entirely or mostly from one species of tree: little or no overlap was detected despite the tree species growing in well-mixed stands. Host plant specificity thus appears to be strong in this genus. 4. Species in two other genera (Pholaseius and Australiseiulus), also considered to be predatory, showed a similar association with particular tree species. 5. The implications for the use of these predators in biological control are considerable. In particular, phytoseiid species with specific needs in terms of host plants may not be suitable for use as general purpose predators. Meeting the needs of phytoseiids through the modification of host plant attributes may be a step towards enhancing their efficacy as biological control agents.

Functional benefits of predator species diversity depend on prey identity

1. Determining the functional significance of species diversity in natural enemy assemblages is a key step towards prediction of the likely impact of biodiversity loss on natural pest control processes. While the biological control literature contains examples in which increased natural enemy diversity hinders pest control, other studies have highlighted mechanisms where pest suppression is promoted by increased enemy diversity. 2. This study aimed to test whether increased predator species diversity results in higher rates of predation on two key, but contrasting, insect pest species commonly found in the rice ecosystems of south-east Asia. 3. Glasshouse experiments were undertaken in which four life stages of a planthopper (Nilaparvata lugens) and a moth (Marasmia patnalis) were caged with single or three-species combinations of generalist predators. 4. Generally, predation rates of the three-species assemblages exceeded expectation when attacking M. patnalis, but not when attacking N. lugens. In addition, a positive effect of increased predator species richness on overall predation rate was found with M. patnalis but not with N. lugens. 5. The results are consistent with theoretical predictions that morphological and behavioural differentiation among prey life stages promotes functional complementarity among predator species. This indicates that emergent species diversity effects in natural enemy assemblages are context dependent; they depend not only on the characteristics of the predators species, but on the identity of the species on which they prey.

Black sea urchins evaluate predation risk using chemical signals from a predator and injured con- and heterospecific prey

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)