The effect of refuge on Dermestes ater (Coleoptera : Dermestidae) predation on Musca domestica (Diptera : Muscidae): Refuge for prey or the predator?

It is believed that habitat heterogeneity can change the extent of predator-prey interactions. Therefore, in this study we examined the effect of habitat heterogeneity (characterized here as an addition of refuge) on D. ater predation on M. domestica. Predation of D. ater on M. domestica larvae was carried out in experimental habitats with and without refuge, and examined at different prey densities. The number of prey eaten by beetles over 24 h of predator-prey interaction was recorded, and we investigated the strength of interaction between prey and predator in both experimental habitats by determining predator functional response. The mean number of prey eaten by beetles in the presence of refuge was significantly higher than in the absence of refuge. Females had greater weight gains than males. Logistic regression analyses revealed the type II functional response for both experimental habitats, even though data did not fit well into the random predator model. Results suggest that the addition of refuge in fact enhanced predation, as prey consumption increased in the presence of refuge. Predators kept in the presence of refuge also consumed more prey at high prey densities. Thus, we concluded that the addition of refuge was an important component mediating D. ater-M. domestica population interactions. Refuge actually acted as a refuge for predators from prey, since prey behaviors detrimental to predators were reduced in this case.

Relationship Among Phenolic Contents, Seed Predation, and Physical Seed Traits in Mimosa bimucronata Plants

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

THE EXTENT of SEED PREDATION BY BRUCHINE BEETLES (COLEOPTERA: CHRYSOMELIDAE: BRUCHINAE) IN A HETEROGENEOUS LANDSCAPE IN SOUTHEASTERN BRAZIL

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Bottom-up and top-down effects in a pre-dispersal seed predation system: are non-predated seeds damaged?

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Feeding habits of the spider crab Libinia spinosa H. Milne Edwards, 1834 (Decapoda, Brachyura) in Ubatuba Bay, São Paulo, Brazil

The main goal of this study was the identification of the items of the diet of the L. spinosa, based on the stomach contents analysis. The crabs were obtained from Ubatuba region north-eastern shore of São Paulo State. In the laboratory, all the individuals were dissected, the stomach was retreated and fixed in 10% formaline. The alimentary items were identified under stereomicroscope and analysed by the method of Frequency of Occurrence. A total of 194 stomachs was analysed and nine alimentary items were obtained. Unindentified material was found in 98% of analysed stomach and poriferan were present in less then 1% of stomachs. These results pointed a diversified diet explored by this crab, as well as the employment of some different methods for food intake. This suggested that these crabs could occupy different position in the trophic chain.

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)

Dispersal and predation behavior in larvae of Chrysomya albiceps and Chrysomya megacephala (Diptera : Calliphoridae)

Chrysomya albiceps and Chrysomya megacephala are exotic blowfly species known by producing myiasis in humans and other animals and by transmitting pathogens mechanically. C. albiceps stand out by being a facultative predator of other dipteran larvae. In this paper we investigated the influence of larval predation on the dispersal of larvae of C. albiceps and C. megacephala single and double species for three photophases. An experimental acrylic channel graduated and covered with wood shavings was used to observe the larval dispersal. The results showed that C. albiceps attacks C. megacephala larvae during dispersal and keeps an aggregated pattern close to the release point, in single and double species, independently of the different photophases. Chrysomya megacephala single species exhibited the same pattern, but in double species this was changed to a random distribution.

Larval predation on different instars in blowfly populations

Chrysomya albiceps (Diptera: Calliphoridae) é uma predadora facultativa sobre outras moscas-varejeiras, durante o terceiro instar larval. Nesse estudo, nos investigamos a taxa de predação de C. albiceps sobre larvas de primeiro, segundo e terceiro instar de C. megacephala e C. macellaria comparando a vulnerabilidade dos instares larvais frente à predadora. Para as presas de primeiro e segundo instar, C. albiceps apresentou maior taxa de predação sobre C. megacephala. Já sobre larvas de terceiro instar a predadora consumiu mais C. macellaria. O comportamento de C. albiceps sobre as duas espécies de presas sugere uma mudança na estratégia de forrageio da predadora e essa mudança pode ter influencia sobre a comunidade de dípteros necrófagos.

Larval dispersal and predation in experimental populations of Chrysomya albiceps and Cochliomyia macellaria (Diptera: Calliphoridae)

In this study we investigated the larval dispersal associated with larval predation in experimental populations of Chrysomya albiceps and Cochliomyia macellaria. Frequency distribution of sampling units (G test) in the substrate was used to evaluate variation in larval dispersal. An experimental acrylic channel (1 x 0.1 x 0.2 m) covered with wood shavings was used to observe larval dispersal prior to pupation. The acrylic channel was graduated at 0.05 m intervals, each representing a sampling unit; hence, 20 sampling units were set up. A Petri dish containing third instar larvae of single and double species was deposited at one edge of the acrylic channel allowing larvae to disperse. The number of buried pupae (0, 1, 2, n) present in each sampling unit was recorded. For double species, the number of recovered larvae of C. albiceps was similar to the number initially released on the dish Petri. on the other hand, the number of recovered larvae of C. macellaria was significantly smaller than the initially released number. The results show that C. albiceps attacks C. macellaria larvae during the larval dispersal process. The larval distribution of C. albiceps did not differ significantly from C. macellaria in double species, but it differed significantly in single species. The larval aggregation level of C. macellaria decreased when C. albiceps was present and the larval aggregation level of C. albiceps increased when C. macellaria was present. The implications of such findings for the population dynamics of these species are discussed.

Postlarval stages and growth patterns of the spider crab Pyromaia tuberculata (Brachyura, Majidae) from laboratory-reared material

The spider crab Pyromaia tuberculata was introduced into southeastern Brazil; ovigerous material was collected and reared in the laboratory. Morphologic changes and growth patterns of post-larval development are reported. Results show that within-stage size variation is lowest in mature stages, especially in the case of females in which there is an apparent size threshold for the last juvenile stages to undergo the puberty molt. A prepuberty molt taking place at the fourth crab stage is indicated by analyzing the allometric growth of the abdomen in females. In contrast, the same procedure using the allometric growth of chelae failed in detecting both the prepuberty and puberty molts in males. Conversely to females, which develop a complex brood chamber at the puberty molt, the enlargement of chelae was not consistent in all postpuberty males. The short instar sequence of this species, in no case exceeding nine stages, is marked by conspicuous morphologic alterations achieved at each molt. Almost all stages can be identified by examining diagnostic features of rostrum, abdomen, sternum, and pleopods.

Reproductive output of the spider crab Epialtus bituberculatus (H. Milne Edwards, 1834) (Crustacea, Decapoda, Brachyura) associated with beds of the alga Sargassum cymosum (C. Agardh, 1820) on the southeastern Brazilian coast

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effect of architectural angularity on refugia selection by the brown spider, Loxosceles gaucho

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)