Costs and benefits of freezing behaviour in the harvestman Eumesosoma roeweri (Arachnida, Opiliones)

Animals present an enormous variety of behavioural defensive mechanisms, which increase their survival, but often at a cost. Several animal taxa reduce their chances of being detected and/or recognized as prey items by freezing (remaining completely motionless) in the presence of a predator. We studied costs and benefits of freezing in immature Eumesosoma roeweri (Opiliones, Sclerosomatidae). Preliminary observations showed that these individuals often freeze in the presence of the syntopic predatory spider Schizocosa ocreata (Araneae, Lycosidae). We verified that harvestmen paired with predators spent more time freezing than when alone or when paired with a conspecific. Then. we determined that predator chemical cues alone did not elicit freezing behaviour. Next, we examined predator behaviour towards moving/non-moving prey and found that spiders attacked moving prey significantly more, suggesting an advantage of freezing in the presence of a predator. Finally, as measure of the foraging costs of freezing, we found that individuals paired with a predator for 2 h gained significantly less weight than individuals paired with a conspecific or left alone. Taken together, our results suggest that freezing may protect E. roeweri harvestmen from predatory attacks by wolf spiders, but at the cost of reduced food and/or water intake. (C) 2009 Elsevier B.V. All rights reserved.

Extremely slow feeding in a tropical drilling ectoparasite, Vitularia salebrosa (King and Broderip, 1832) (Gastropoda: Muricidae), on molluscan hosts from Pacific Panama

This study documents one of the slowest feeding behaviors ever recorded for a muricid gastropod in one of the most biotically rigorous regions on the planet. In Pacific Panama, Vitularia salebrosa attacks mollusks by drilling through their shells. The duration of attacks estimated by isotope sclerochronology of oyster shells collected during attacks in progress range from 90 to 230 days, while experimental observation of interactions documented one attack greater than 103 days. The prolonged nature of attacks suggests that V. salebrosa is best characterized as an ectoparasite than as a predator, which is the ancestral condition in the Muricidae. An ectoparasitic lifestyle is also evident in the unusual interaction traces of this species, which include foot scars, feeding tunnels and feeding tubes, specialized soft anatomy, and in the formation of male-female Pairs, which is consistent with protandrous hermaphroditism, as is typical in sedentary gastropods. To delay death of its host, V. salebrosa targets renewable resources when feeding, such as blood and digestive glands. A congener, Vitularia miliaris from the Indo-Pacific, has an identical feeding biology The origin and persistence of extremely slow feeding in the tropics challenges our present understanding of selective pressures influencing the evolution of muricid feeding behaviors and morphological adaptations. Previously, it has been suggested that faster feeding is advantageous because it permits predators to spend a greater proportion of time hiding in enemy-free refugia or to take additional prey, the energetic benefits of which could be translated into increased fecundity or defenses. The benefits of exceptionally slow feeding have received little consideration. In the microhabitat preferred by V. salebrosa (beneath boulders), it is possible that prolonged interactions with hosts decrease vulnerability to enemies by reducing the frequency of risky foraging events between feedings . Ectoparasitic feeding through tunnels by V. salebrosa may also reduce competitive interactions with kleptoparasites (e.g., crabs, snails) that steal food through the gaped valves of dead or dying hosts.

Segregated anatomical input to sub-regions of the rodent superior colliculus associated with approach and defense

The superior colliculus (SC) is responsible for sensorimotor transformations required to direct gaze toward or a way from unexpected, biologically salient events. Significant changes in the external world are signaled to SC through primary multisensory afferents, spatially organized according to a retinotopic topography. For animals, where anunexpected event could indicate the presence of either predator or prey, early decisions to approach or avoid are particularly important. Rodents' ecology dictates predators are most often detected initially as movements in upper visual field (mapped in medial SC), while appetitive stimuli are normally found in lower visual field (mapped in lateral SC). Our purpose was to exploit this functional segregation to reveal neural sites that can bias or modulate initial approach or avoidance responses. Small injections of Fluoro-Gold were made into medial or lateral sub-regions of intermediate and deep layers of SC (SCm/SCl). A remarkable segregation of input to these two functionally defined areas was found. (i) There were structures that projected only to SCm (e.g., specific cortical areas, lateral geniculate and suprageniculate thalamic nuclei, ventromedial and premammillary hypothalamic nuclei, and several brain-stem areas) or SCl (e.g., primary somatosensory cortex representing upper body parts and vibrissae and parvicellular reticular nucleus in the brainstem). (ii) Other structures projected to both SCm and SCl but from topographically segregated populations of neurons (e.g., zona incerta and substantia nigra pars reticulata). (iii) There were a few brainstem areas in which retrogradely labeled neurons were spatially overlapping (e.g., pedunculopontine nucleus and locus coeruleus). These results indicate significantly more structures across the rat neuraxis are in a position to modulate defense responses evoked from SCm, and that neural mechanisms modulating SC-mediated defense or appetitive behavior are almost entirely segregated.

Feeding habits of Guiana dolphins, Sotalia guianensis, from south-eastern Brazil: new items and a knowledge review

This study presents new information on feeding habits of Guiana dolphins, Sotalia guianensis, in south-eastern Brazil, together with new regression equations to evaluate the weight and length of fish from otoliths, showing an overview on the knowledge about this species' diet in this area. Eighteen stomach contents had been analysed and compared to 180 samples collected in another eight feeding studies. The analysed specimens were either incidentally caught in gillnets used in coastal waters by the fleet based in the Cananeia main harbour (25 degrees 00'S 47 degrees 55'W), south of Sao Paulo State, or found dead in inner waters of the Cananeia estuary between 2003 and 2009. Based on the index of relative importance analysis, the most important fish species were the banded croaker, Paralonchurus brasiliensis. Doryteuthis plei was the most representative cephalopod species. Stellifer rastrifer was the most important fish species observed in dolphins in inner estuarine waters and P. brasiliensis in recovered dolphins from coastal waters. Loliguncula brevis is the only cephalopod species reported from dolphins found in inner estuarine waters up to date. Doryteuthis plei was the most important cephalopod species observed in coastal dolphins. When considering other feeding studies, the most representative fish family in the diet of S. guianensis was Sciaenidae, which is mainly represented by demersal fishes. The main preys of S. guianensis are abundant in the studied areas, which may indicate an opportunistic feeding habit. The majority of them are not the most important target species by the commercial fishery in south-eastern Brazil.

Prey-capture efficiency between juveniles and adults, feeding habitat and abundance of Wattled Jacana foragers in northern Pantanal, Mato Grosso state, Brazil

The choice of foraging strategies implies an attempt at gaining energy by predators. Supposedly, the difference in employing the "sit and wait" or "active foraging" behavior lays in hunter skills, experience and the kind of prey consumed. With the hypothesis that "active foraging" demands no learning, in this study we compared the prey capture efficiency among Wattled Jacana juveniles and adults, and also present descriptive information about feeding habitat and the abundance variation of foragers throughout the day in the northern Pantanal. Prey capture efficiency did not differ significantly among juveniles and adults, corroborating our initial hypothesis that "active foraging" is an instinctive behavior and demands no experience to be effective. However, future work is necessary to compare the energetic quality of consumed items by juveniles and adults, searching for differences explained by adults' experience. Foraging individuals were found at an average distance of 14 m ranging from 2 to 42 m) from the margin of the sampled swamps, however 64% of the foragers were found closer to the margins. The average depth of foraging sites was 17 cm, ranging from 5 to 40 cm, although no preference for specific classes of depth was found (p > 0,05). Despite the accepted general pattern of birds being more active in the early morning, the largest number of individuals foraging was observed between 11:00 and 12:00 AM, but no significant difference was found in the abundance of foraging individuals among different periods of the day. Factors, which were not analyzed, such as food availability and presence of competitors and predators need to be studied to reveal the main factors of the spatial and temporal distribution of the Wattled Jacana.

The preimaginal stages of the ensign wasp Evania appendigaster (Hymenoptera, Evaniidae), a cockroach egg predator

Evania appendigaster is a cosmopolitan wasp that deposits eggs in the oothecae of some species of cockroaches; its larvae then consume the cockroach eggs and embryos. It is a candidate for the biological control of cockroaches, but little is known about its basic biology. Here we describe the external morphology of all immature stages of E. appendigaster and compare them with the larvae of related species. The life cycle of E. appendigaster includes three larval instars, each with 13 body segments. Their mouthparts were generally reduced, except for the mandibles, which were always sclerotized and toothed, and were especially robust in second-instar larvae. Antennal and mouthpart sensilla were basiconic and difficult to observe. Larvae of E. appendigaster are similar in form to other described evaniid larvae, but quite different from the two available descriptions of larvae of gasteruptiid and aulacid wasps. Further descriptions of evaniid larvae will be useful in determining how widespread this morphology is within the family, and in understanding phylogenetic relationships within Hymenoptera.

Feeding ecology of the American freshwater goby Ctenogobius shufeldti (Gobiidae, Perciformes) in a sub-tropical estuary

The feeding ecology of the American freshwater goby Ctenogobius shufeldti in a low salinity salt-marsh habitat in the Paranagua Bay estuarine complex (Brazil) was assessed through the gut analysis of 632 individuals. The effects of a set of abiotic factors (type of sediment, salinity, temperature and estuarine reach), season and body size on dietary composition were analysed. Seasonal and size-related changes in feeding strategy, feeding intensity and trophic level were assessed. The effects of gape and body size on prey size use were also analysed. The results showed that C. shufeldti is a typical omnivorous, generalized benthic predator of low trophic levels throughout the seasons and size classes, feeding on 56 dietary items; tanaids, chlorophyte algae, ostracods, gastropods, detritus and benthic diatoms made up the bulk of its diet. The tanaid Kalliapseudes schubarti was the main prey item in both numerical and volumetric terms. The gut fullness was persistently high across the seasons. As expected for a typical generalized, opportunistic omnivorous feeder: (1) seasonal and spatial-temporal variability of abiotic factors had a significant effect on diet structure, (2) season accounted for most of the dietary variation and (3) diet composition and the size of prey consumed did not vary across the size classes.

FEEDING HABITS OF THE ATLANTIC SPOTTED DOLPHIN, Stenella frontalis, IN SOUTHEASTERN BRAZIL

This study presents new information on the feeding habits of the Atlantic spotted dolphins, Stenella frontalis, in the Western South Atlantic. Nine stomach contents of S. frontalis incidentally caught in fishing operations conducted by the gillnet fleet based on main harbour of Cananeia (25 degrees 00' S; 47 degrees 55'W), southeastern Brazil, were analyzed. These specimens were captured between 2005 and 2007. A total of 1 422 cephalopod beaks, 147 otoliths and three crustaceans were recovered from the stomach contents. The dolphins assessed preyed on at least eight different fish species of the families Trichiuridae, Carangidae, Sparidae, Merluccidae, Engraulidae, Sciaenidae, Congridae and Scombridae, five cephalopod species of the families Loliginidae, Sepiolidae, Tremoctopodidae and Thysanoteuthidae, and one shrimp species of the Penaeidae family. Based on the analysis of the Index of Relative Importance (IRI), the Atlantic cutlassfish, Trichiurus lepturus, was the most important fish species represented. Of the cephalopods, the squid Doryteuthis plei was by far the most representative species. Several items were reported for the first time as prey of the S. frontalis: Xiphopenaeus kroyeri, Tremoctopus violaceus, Semirossia tenera, Merluccius hubbsi, Pagrus pagrus and Paralonchurus brasiliensis. S. frontalis presented teuthophagous and ichthyofagous feeding habits, with apparent predominance of the first, and preyed mainly on pelagic and demersal items.

First observation of alternative food usage (extrafloral nectar) by the assassin bug Atopozelus opsimus (Hemiptera, Reduviidae)

First observation of alternative food usage (extrafloral nectar) by the assassin bug Atopozelus opsimus (Hemiptera, Reduviidae). Assassin bugs (Reduviidae) are voracious insects that prey on other arthropods. Recent evidences have pointed out that these predators also feed on plant derived substances in rare opportunities. The present study describes the feeding behavior of the reduviid Atopozelus opsimus on extrafloral nectaries of Inga vera (Fabaceae) in a Neotropical savanna area. It was investigated if the insects feed more frequently of extrafloral nectar or prey, and if individuals of different stages of development vary according to feeding behavior. Notably, the results suggest that the diet of all instars and adults consist mainly of extrafloral nectar (N = 1013), in detriment of captured prey ingestion (N = 18). Also, there was no variation on feeding behavior and life stage.

Toxicity of synthetic and natural compounds on Tetranychus urticae and the predator Phytoseiulus macropilis

The objective of this work was to evaluate the toxicity of synthetic and natural compounds on Tetranychus urticae and the predator Phytoseiulus macropilis. Mortality and growth rates of T. urticae and its predator were evaluated after applications of: abamectin, clofentezine, fenpropathrin, fenpyroximate, propargite, sulfur and spiromesifen, at their recommended concentrations; neem oils (Natuneem and Sempre Verde Killer Neem at 1%); and aqueous extracts at 10% of Dieffenbachia brasiliensis, Annona squamosa, Ruta graveolens, Agave angustifolia, Melia azedarach, Sonchus oleraceus, Mentha spicata x M. suaveolens, Allium cepa, Laurus nobilis, and Eucalyptus saligna. The acute toxicity and the influence of the compounds on the instantaneous growth rate of the mites were carried out in laboratory. Extracts of A. cepa, A. angustifolia, neem oil-based products, spiromesifen, propargite, fenpyroximate, abamectin and fenpropathrin caused mortality higher than 83% on T. urticae. Extract of A. angustifolia, Natuneem and clofentezine did not cause significant mortality rates on P. macropilis. Agave angustifolia and Natuneem did not affect significantly the growth rate of this predator. Propargite, fenpyroximate, abamectin, fenpropathrin, spiromesifen and extract of L. nobilis severely affected P. macropilis population.

SECONDARY METABOLITES FROM NUDIBRANCHS Tambja stegosauriformis, Hypselodoris lajenis AND Okenia zoobotryon AND FROM BRYOZOANS Zoobotryon verticillatum AND Bugula dentata FROM THE BRAZILIAN COASTLINE

SECONDARY METABOLITES FROM NUDIBRANCHS Tambja stegosauriformis, Hypselodoris lajenis AND Okenia zoobotryon AND FROM BRYOZOANS Zoobotryon verticillatum AND Bugula dentata FROM THE BRAZILIAN COASTLINE. The chemical investigation of the MeOH extract from the bryozoan B. dentata MeOH yielded tambjamines A (1), C (3), D (4), K (6), aldehyde 8 and the new tambjamine J1(9), while the extract of its predator, the nudibranch Tambja stegosauriformis, yielded tambjamines C and K, along with aldehyde 8. Furodisinin lactone (11) was isolated from the nudibranch Hypselodoris lajensis, a compound previously isolated from Dysidea sponges. The alkaloid 2,5,6-tribromo-N-methylgramine (12) was isolated from the nudibranch Okenia zoobotryon and from its prey, the bryozoan Zoobotryon verticillatum, the only source of 12 previously known.

Probabilistic patterns of interaction: the effects of link-strength variability on food web structure

Patterns of species interactions affect the dynamics of food webs. An important component of species interactions that is rarely considered with respect to food webs is the strengths of interactions, which may affect both structure and dynamics. In natural systems, these strengths are variable, and can be quantified as probability distributions. We examined how variation in strengths of interactions can be described hierarchically, and how this variation impacts the structure of species interactions in predator-prey networks, both of which are important components of ecological food webs. The stable isotope ratios of predator and prey species may be particularly useful for quantifying this variability, and we show how these data can be used to build probabilistic predator-prey networks. Moreover, the distribution of variation in strengths among interactions can be estimated from a limited number of observations. This distribution informs network structure, especially the key role of dietary specialization, which may be useful for predicting structural properties in systems that are difficult to observe. Finally, using three mammalian predator-prey networks ( two African and one Canadian) quantified from stable isotope data, we show that exclusion of link-strength variability results in biased estimates of nestedness and modularity within food webs, whereas the inclusion of body size constraints only marginally increases the predictive accuracy of the isotope-based network. We find that modularity is the consequence of strong link-strengths in both African systems, while nestedness is not significantly present in any of the three predator-prey networks.

Demography and evolution of regional inequality

This paper addresses the importance of life cycle aspects in explaining the evolution of regional income inequality. The analysis of household microdata organized in age cohorts shows that Brazilian regional income inequality has different dynamics across generations, with income convergence being observed only for the older generations. The larger income share of younger generations produces a low speed of convergence in the country. When retirement payments, pensions, and other government transfers are excluded from income, convergence is not observed even for the older generations.

Assessment of trophic transfer of benzo(a)pyrene genotoxicity from the post-larval pink shrimp F. brasiliensis to the juvenile Florida pompano T. carolinus

In the present study, the polycyclic aromatic hydrocarbon (PAH) genotoxicity was investigated in a one-step predator-prey relationship with the trophic-related marine species. Florida pompanos were fed for 5 and 10 days with pink shrimp post larvae previously exposed to benzo(a)pyrene (BaP) concentrations. Parent BaP body burden was measured in samples of Farfantepenaeus brasiliensis. BaP metabolites were determined in bile samples of Trachinotus carolinus and DNA damage was assessed through the comet and erythrocyte nuclear abnormalities (ENAs) assays in fish erythrocytes. BaP body burden increased significantly with the PAH concentration in pink shrimp PLs as well as the fish bile BaP metabolites. Both, comet and ENAs assays indicated significant increase on erythrocyte DNA damage of Florida pompanos fed with BaP-exposed pink shrimp on both feeding periods. The trophic route of BaP genotoxicity is discussed as well as the PAH biotransformation as the inducing mechanism for the DNA damages observed.

How promising is Lasioseius floridensis as a control agent of Polyphagotarsonemus latus?

The blattisociid mite Lasioseius floridensis Berlese was found associated with the broad mite, Polyphagotarsonemus latus (Banks), on gerbera leaves in Mogi das Cruzes, State of Sao Paulo, Brazil. Blattisociid mites are not common on aerial plant parts, except under high air humidity levels. Some Lasioseius species have been mentioned as effective control agents of rice pest mites, but nothing is known about the biology of L. floridensis. The objective of this study was to evaluate whether the observed co-occurrence of L. floridensis and P. latus was just occasional or whether the latter could be important as food source for the former, assumed by laboratory evaluation of the ability of the predator to maintain itself, reproduce and develop on that prey. Biological parameters of L. floridensis were compared when exposed to P. latus and to other items as food. The study showed that mating is a pre-requisite for L. floridensis to oviposit and that oviposition rate was much higher on the soil nematode Rhabditella axei (Cobbold) (Rhabditidae) than on P. latus. Ovipositon on the acarid mite Tyrophagus putrescentiae (Schrank) was about the same as on P. latus, but it was nearly zero when the predator was fed the fungi Aspergillus flavus Link or Penicillium sp., or cattail (Typha sp.) pollen. Survivorship was higher in the presence of pollen and lower in the presence of A. flavus or Penicillium sp. than in the absence of those types of food. Life table parameters indicated that the predator performed much better on R. axei than on P. latus. To evaluate the potential effect of L. floridensis as predator of P. latus, complementary studies are warranted to determine the frequency of migration of L. floridensis to aerial plant parts, when predation on P. latus could occur.