Thermal preference in Drosophila

Environmental temperature strongly affects physiology of ectotherms. Small ectotherms, like Drosophila, cannot endogenously regulate body temperature so must rely on behavior to maintain body temperature within a physiologically permissive range. Here we review what is known about Drosophila thermal preference. Work on thermal behavior in this group is particularly exciting because it provides the opportunity to connect genes to neuromolecular mechanisms to behavior to fitness in the wild.     

Potential effects of El Niño-South Oscillation (ENSO) on growth of the American crocodile, Crocodylus acutus (Crocodylia: Crocodilydae) in captivity

Temperature affects growth rate of crocodiles. However, no information exists about the effects of temperature by El Niño-South Oscillation (ENSO) on crocodiles. In this paper, we present information about the effect of ENSO on total length and body mass of Crocodylus acutus in captivity during 1997–2001. We did not observe differences in total length among years, but we did so in body mass. Furthermore, we observed that warm episodes of ENSO were associated with a higher average total length and cold episodes represented a higher average of body mass. Sea surface temperature (SST) was significantly related with total length; however, the relationship between SST and body mass was unclear. We suggest that ENSO effects on growth rates of crocodiles need to be considered as an important factor on the management of captive populations.     

Nudibranch-sponge feeding dynamics: Benefits of symbiont-containing sponge to Archidoris montereyensis (Cooper, 1862) and recovery of nudibranch feeding scars by Halichondria panicea (Pallas, 1766)

Selected interactions between the encrusting sponge Halichondria panicea and its primary predator, the dorid nudibranch Archidoris montereyensis, were investigated in a high-latitude rocky intertidal community spatially dominated by H. panicea. Feeding experiments were conducted in which A. montereyensis pairs were provided with sponge containing symbiotic zoochlorellae or sponge in which the zoochlorellae population had been reduced or removed by shading. Nudibranchs consuming H. panicea with symbiotic zoochlorellae had higher feeding, growth, and egg production rates than individuals eating aposymbiotic sponge. We simulated A. montereyensis predation on H. panicea by creating typically sized feeding grooves in the sponge. H. panicea's response was high linear growth rates into the experimental feeding grooves, generally recovering most of the groove area within 4 weeks. Overall, the sponge's rapid response to tissue damage minimizes grazing impacts and substrate loss and reduces susceptibility to wave removal.     

Effect of intestinal erythrocyte agglutination on the feeding performance of Triatoma brasiliensis (Hemiptera: Reduviidae)

Triatoma brasiliensis is an important vector of Trypanosoma cruzi in Brazil. The feeding efficiency on its hosts depends on several parameters including the maintenance of the ingested blood at low viscosity, which could be modulated by the anterior midgut (crop) anticoagulant and haemagglutinant activities. In the present study, we characterized T. brasiliensis crop haemagglutination activity and evaluated its importance in the feeding process. Soluble crop contents (SCC) of T. brasiliensis were able to agglutinate rat, mouse and rabbit eryhtrocytes, but had no activity on cattle and Thrichomys apereoides, a rodent species commonly associated with T. brasiliensis in the wild. The haemagglutination was characterized by the immediate formation of several clusters of erythrocytes connected by flexible elastic-like fibers. The feeding efficiency of T. brasiliensis on rat (agglutinated by SCC) was almost double that from T. apereoides (not agglutinated by SCC). The influence of haemagglutination on feeding was confirmed by artificially feeding bugs on a diet composed of cattle or rat erythrocytes. The bugs fed on cattle erythrocytes had lower ingestion rates in comparison to those fed on rats. The results indicate that, in addition to other parameters, haemagglutination brought about by SCC has an important role in the feeding efficiency of T. brasiliensis.     

Evolutionarily conserved thermal biology across continents: The North American lizard Plestiodon gilberti (Scincidae) compared to Asian Plestiodon

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The lizard genus Plestiodon (Scincidae; formerly Eumeces) is widespread in North America and Asia, but the thermal biology of only a few species has been studied.     

Carbon and nitrogen relationships in the feeding and growth of the Pacific oyster, Crassostrea gigas (Thunberg)

Bivalve molluscs, in common with consumers in general, use behavioral and physiological mechanisms to balance metabolic requirements with available nutrients. This study considered how the Pacific oyster, Crassostrea gigas, meets the demands of growth and maintenance, measured in terms of carbon and nitrogen, in a variable food environment. Stoichiometry theory helped to evaluate: a) whether feeding behaviour modifies the intake of C and N given seasonal variability in food quality: b) how rates of metabolism and excretion, and C and N growth efficiencies, respond to mismatch between nutrient intake and the oysters' needs. Two field experiments in the Port Stephens estuary, near Sydney, Australia, measured feeding behaviour, metabolic and growth rates relative to seasonal changes in food supply. In a laboratory experiment, relationships between physiological rates and growth were measured to test a model of growth as a function of absorption of C and N. Potential metabolic targets for compensation were the C/N ratios of body tissues, maintenance and/or of soft tissue added as growth. C/N of whole soft issues varied little during the year (mean 5.4). In July (a time of low food availability of poor quality) growth was negligible and the C/N (maintenance) target was 6.7. In March (abundant food of high quality) growth was rapid with a high N-demand; the C/N of growth was 3.9. In November (medium food quality) there was an enhanced C-demand for glycogen storage; the C/N of growth was 7.9. Feeding behaviour changed the balance between C and N intake across months, primarily due to changes in the selection efficiency for nitrogen, which was highest at low filtration rates on particles of high C/N ratio. Nitrogen intake was favoured over C in July. In November, C-intake increased relative to N. In March, when abundant food nitrogen coincided with a high demand for growth, feeding behaviour was neutral with respect to C/N ratios. In all cases C/N of absorbed matter was greater than the C/N of growth. Growth efficiencies for carbon declined with increased C/N of ingested matter due to higher metabolic increments (SDA) when feeding on lower food quality; the metabolic costs of growth did not vary. In contrast, growth efficiencies for nitrogen did not alter with C/N for ingested matter, due in part to increased nitrogen losses, relative to tissue nitrogen content, when feeding on low C/N food. Nitrogen was therefore conserved metabolically relative to C. Both feeding and metabolic processes contributed to compensation for the mismatch between seasonally variable food quality and the demands of growth.     

Seasonal variability in feeding behaviour, metabolic rates and carbon and nitrogen balances in the Sydney oyster, Saccostrea glomerata (Gould)

To establish if nutrients limit the growth of bivalves requires information not only on the quality of food available, but also the animals' feeding behaviour and endogenous metabolic demands. We hypothesized that growth of the Sydney rock oyster (Saccostrea glomerata) would vary in response to seasonal changes in food quality rather than quantity. We also predicted that the oysters would show feeding preferences for nitrogen over carbon, and this behaviour would result in carbon/nitrogen (C/N) ratios for ingested and absorbed matter that would be lower than the C/N of both the seston and the oysters' estimated metabolic maintenance requirements. The experiments were done in two phases under natural conditions. In phase 1, feeding behaviour was assessed on a single occasion and the results used to pose hypotheses for testing in phase 2, which included measurements made on three occasions encompassing autumn, winter and spring conditions. Growth rates varied with changes in ambient food quality and not with the concentration of total suspended matter. Feeding behaviour responded to food quality and, in most cases, resulted in nitrogen enrichment. For example, when nitrogen was potentially limiting to growth and/or maintenance, due to high food C/N (July) or high nitrogen demand (March), pre-ingestive selection ensured nitrogen enrichment of ingested matter and C/N ratios of ingested matter which were below the maintenance requirement. However, in November, when endogenous demands indicated an increased requirement for carbon, feeding behaviour resulted in carbon enrichment, an increase in carbon conversion efficiency, and ingested C/N ratios greater than the maintenance requirement. The results support the assertion of variable feeding physiology in oysters, responsive to both exogenous (seasonal differences in carbon and nitrogen availability) and endogenous (cycles of reproduction and growth) factors.     

Morphological and behavioural adaptations to the rocky substrate by the fiddler crab Uca panamensis (Stimpson, 1859): preference for feeding substratum and feeding mechanism

The fiddler crab Uca panamensis (Stimpson, 1959) inhabits rocky shores. We examined its preference for feeding substratum—sand or rock—and its manner of feeding. The crab made its burrow in the sand among rocks but preferred to feed on rocks. The feeding time decreased as the distance between the burrow and the rock increased. We consider this to be a result of exclusive interaction among the crabs because they defended their feeding area on the rocks against others.The crab wetted a small area of rock with water held in the branchial chambers before and during feeding. It pinched up the wetted surface in the minor chelipeds, which have bundles of setae on the posterior tips of the dactyl and pollex, and put the material into its buccal cavity. It never expelled sand pellets while feeding on rock, which indicates that it swallowed the food particles directly, without sorting. The bundles of setae retained water by capillary attraction, which suggests that they capture the suspended fine food particles scraped from the rock. The wetting action may prevent the fine materials from dispersing. We consider that morphological alteration of the minor chelipeds, the application of water from the branchial chambers, and direct swallowing permit the fiddler crab to feed on fine materials attached to rocks.     

Influence of host plants on feeding, growth and reproduction of Papilio polytes (The common mormon)

We studied the feeding, growth and reproductive behaviour of Papilio polytes (common mormon butterfly) on five different host plants, Murraya koenigii, Toddalia asiatica, Glycosmis pentaphylla, Aegle marmelos and Citrus medica. The growth rate of P. polytes was fastest on M. koenigii followed by T. asiatica, C. medica, G. pentaphylla and A. marmelos. We related this to the nutrient contexts of the five plants. The plants T. asiatica and C. medica had higher water contents, which influenced the growth rate of the insect. M. koenigii was found to contain rich quantities of carbohydrate. M. koenigii, T. asiatica and C. medica were also rich in protein when compared to A. marmelos and G. pentaphylla. Total amino acid levels were comparatively higher in M. koenigii, T. asiatica, C. medica rather than A. marmelos and G. pentaphylla.     

Local immune response against larvae of Rhipicephalus (Boophilus) microplus in Bos taurus indicus and Bos taurus taurus cattle

Bos taurus indicus cattle are less susceptible to infestation with Rhipicephalus (Boophilus) microplus than Bos taurus taurus cattle but the immunological basis of this difference is not understood. We compared the dynamics of leukocyte infiltrations (T cell subsets, B cells, major histocompatibility complex (MHC) class II-expressing cells, granulocytes) in the skin near the mouthparts of larvae of R. microplus in B. t. indicus and B. t. taurus cattle. Previously naïve cattle were infested with 50,000 larvae (B. t. indicus) or 10,000 larvae (B. t. taurus) weekly for 6 weeks. One week after the last infestation all of the animals were infested with 20,000 larvae of R. microplus. Skin punch biopsies were taken from all animals on the day before the primary infestation and from sites of larval attachment on the day after the first, second, fourth and final infestations. Infiltrations with CD3⁺, CD4⁺, CD8⁺ and γδ T cells followed the same pattern in both breeds, showing relatively little change during the first four weekly infestations, followed by substantial increases at 7 weeks post-primary infestation. There was a tendency for more of all cell types except granulocytes to be observed in the skin of B. t. indicus cattle but the differences between the two breeds were consistently significant only for γδ T cells. Granulocyte infiltrations increased more rapidly from the day after infestation and were higher in B. t. taurus cattle than in B. t. indicus. Granulocytes and MHC class II-expressing cells infiltrated the areas closest to the mouthparts of larvae. A large volume of granulocyte antigens was seen in the gut of attached, feeding larvae.     

Systematics and evolution of the genus Torrubiella (Hypocreales, Ascomycota)

Torrubiella is a genus of arthropod-pathogenic fungi that primarily attacks spiders and scale insects. Based on the morphology of the perithecia, asci, and ascospores, it is classified in Clavicipitaceae s. lat. (Hypocreales), and is considered a close relative of Cordyceps s. 1., which was recently reclassified into three families (Clavicipitaceae s. str., Cordycipitaceae, Ophiocordycipitaceae) and four genera (Cordyceps s. str, Elaphocordyceps, Metacordyceps, and Ophiocordyceps). Torrubiella is distinguished morphologically from Cordyceps s. lat. mainly by the production of superficial perithecia and the absence of a well-developed stipitate stroma. To test and refine evolutionary hypotheses regarding the placement of Torrubiella and its relationship to Cordyceps s. lat., a multi-gene phylogeny was constructed by conducting ML and Bayesian analyses. The monophyly of Torrubiella was rejected by these analyses with species of the genus present in Clavicipitaceae, Cordycipitaceae, and Ophiocordycipitaceae, and often intermixed among species of Cordyceps s. lat. The morphological characters traditionally used to define the genus are, therefore, not phylogenetically informative, with the stipitate stromata being gained and/or lost several times among clavicipitaceous fungi. Two new genera (Conoideocrella, Orbiocrella) are proposed to accommodate two separate lineages of torrubielloid fungi in the Clavicipitaceae s. str. In addition, one species is reclassified in Cordyceps s. str. and three are reclassified in Ophiocordyceps. The phylogenetic importance of anamorphic genera, host affiliation, and stipitate stromata is discussed.     

Structure and development of the style base in Abildgaardia, Bulbostylis, and Fimbristylis (Cyperaceae,Cyperoideae, Abildgaardieae)

The Abildgaardieae tribe within the family Cyperaceae comprises six or seven genera, among which Abildgaardia, Bulbostylis and Fimbristylis pose a challenge regarding their morphological delimitation. Molecular phylogenetic analyses including species of Abildgaardieae are rare, but in most of those studies, Abildgaardia and Fimbristylis appear as more closely related to each other than to the Bulbostylis genus. Duration of the style base has been one of the most widely used characters for delimiting these three genera. The style base is a persistent structure in most species of Bulbostylis and deciduous in Abildgaardia and Fimbristylis. The reasons why the style base may persist or fall off have been scarcely discussed. The assumption that abscission layers are present in the style base of all three genera and the fact that tracheids have been observed in the style base of Bulbostylis suggest that this structure might have histological complexity. In view of this, a complete ontogenetic and anatomical study of the gynoecium has been carried out for all these three genera. It turned out that the style base is histologically simple in Abildgaardia, Bulbostylis and Fimbristylis and shows similar structure and development in all three genera. The fact that the style base has a shorter duration in Abildgaardia and Fimbristylis than in Bulbostylis might be related to the lower number of sclerotised cells that make up such structures in the mature fruit of the former two genera. Abscission of the style and style base may be the result of much simpler reasons than the differentiation of an abscission layer, resulting merely from mechanical shear force effects. Differences among genera have been observed in the shape of the style base and the development of the style. The histological simplicity of the style base is consistent with the homoplastic appearance of this structure in genera that are not closely related (e.g. Rhynchospora). Because of this, while the presence of the thickened style base seems to be a synapomorphy in species of Abildgaardieae, its persistence on or detachment from the fruit might have emerged repeatedly during this clade evolution and might not be a suitable character for genera delimitation.     

Feeding behavior and differential absorption of biochemical components by the infaunal bivalve Mulinia edulis and the epibenthic Mytilus chilensis in response to changes in food regimes

We measured changes in the feeding rate and food absorption efficiency of two suspension feeding bivalves, cross-trasplanted between habitats with special emphasis on their capacity for differential absorption of biochemical components from their food supply. Mulinia edulis were moved from the intertidal zone to the subtidal zone, and Mytilus chilensis from the subtidal to the intertidal zone for a period of 7 days, and then compared with animal that had not been transplanted. Experimentally prepared diets similar to those available in the two different environments were offered to the bivalves, and their rates of feeding and differential uptake of biochemical components were determined and statistically compared. The two species did not achieve complete acclimation of their feeding behaviour during the transplant period since the highest ingestion rates for biochemical components occurred under dietary conditions that reflected their habitats of origin. Absorption efficiency showed greater acclimation than the other physiological parameters measured, indicating the capacity of these species to modulate their enzymatic-digestive activity depending on food composition. We conclude that both Mytilus and Mulinia have a certain degree of physiological plasticity in their feeding behaviour and assimilatory balance of biochemical components, being greater in Mytilus. When both species encounter ambient food conditions characteristic of their normal habitats, they show maximum values of food absorption, while under conditions where their typical diets are exchanged (Mytilus in intertidal and Mulinia in subtidal), the energy absorbed declines in each, but in ways very different between the two species. Thus, Mytilus exposed to high concentrations of low quality seston reduced the energy absorbed by 31.7% compared to its normal habitat, while Mulinia exposed to low concentrations of high-quality food reduced their energy absorption by 64%.     

Variability in response of four populations of Amblyseius largoensis (Acari: Phytoseiidae) to Raoiella indica (Acari: Tenuipalpidae) and Tetranychus gloveri (Acari: Tetranychidae) eggs and larvae

Raoiella indica (Acari: Tenuipalpidae) is a phytophagous mite that recently invaded the Neotropical region. A predatory mite Amblyseius largoensis (Acari: Phytoseiidae) has been found associated with R. indica in Florida. This study evaluated A. largoensis by determining its likelihood of consuming eggs and larvae of R. indica and Tetranychus gloveri (Acari: Tetranychidae) under no-choice and choice conditions. To detect variations in the response of A. largoensis to R. indica, four populations of predators were examined: (1) predators reared exclusively on R. indica in the laboratory for 2 years, (2) predators reared on T. gloveri in the laboratory for 2 months but reared on R. indica for 2 years previously, (3) predators collected from a field infested with R. indica, and (4) predators collected from a field that had never been infested with R. indica. Results of this study suggest that A. largoensis is likely to accept and consume high numbers of R. indica eggs regardless of their previous feeding experience. In contrast, all populations consumed relatively fewer R. indica larvae than the other prey tested. Predators previously exposed to R. indica were more likely to consume R. indica larvae. By contrast, predators not previously exposed to R. indica showed the lowest likelihood of choosing to feed on this prey item. Plasticity in the response of A. largoensis to R. indica larvae could be associated to selection, learning, or a combination of both. The possible implications of the observed differences in terms of biological control of R. indica are discussed.     

Temporal expression and steroidal regulation of piRNA pathway genes (mael, piwi, vasa) during Silurana (Xenopus) tropicalis embryogenesis and early larval development

It has been extensively documented that exposure of amphibians and teleost fish to exogenous steroid hormones like estrogen, androgen, xenoestrogen or steroid biosynthesis inhibitors can impair their gonadal development or induce sex reversal against genotypic sex. However, the molecular pathways underlying sexual development and the effects of sex steroids or other exogenous hormones in these aquatic vertebrates remain elusive. Recently, a germ plasm-associated piRNA (piwi-interacting RNA) pathway has been shown to be a determinant in the development of animal gonadal germline cells. In the current study, we examined whether this piRNA pathway is involved in the regulation of sex steroid hormones in gonadal development. We firstly established developmental expression patterns of three key piRNA pathway genes (mael, piwi and vasa), during Silurana (Xenopus) tropicalis embryogenesis and early larval development. All three genes exhibit high expression at early developmental stages and have significantly decreased expression thereafter, indicating a very active involvement of piRNA pathway at the beginning of embryogenesis. We further examined gene expression changes of those genes in frog larvae exposed to two sex steroid biosynthesis inhibitors, fadrozole and finasteride, both of which are known to result in male-biased or female-biased phenotypes, respectively. We found that fadrozole and finasteride exposures increased the expression of piRNA pathway genes such as mael and vasa at the larval stage when the expression of piRNA pathway genes is programmed to be very low. Therefore, our results indicate that the piRNA pathway is likely a common pathway by which different sex steroid hormones regulate gonadal sex differentiation.     

Thermal ecology of five Cnemidophorus species (Squamata: Teiidae) in east coast of Brazil

In this study we compared the body temperature of 16 populations belonging to five species of the genus Cnemidophorus from restinga habitats along the eastern coast of Brazil in order to evaluate the importance of how some environmental factors affect lizard body temperatures. Cloacal body temperatures (T_b) were taken immediately after capture with a quick-reading thermometer (Schultheis). Substrate temperatures (T_s) and air temperatures (T_a; approximately 1 cm above the substrate) were taken as close as possible to the point when each lizard was initially sighted. Most of the mean body temperatures in activity of the different populations and species of Cnemidophorus along the coast of Brazil ranged from 36.5 to 39.3 °C, except for Cnemidophorus lacertoides (T_b=35.2 °C) in the restinga of Joaquina, SC and for Cnemidophorus ocellifer (T_b=34.8 °C ) in the restinga of Praia do Porto, SE. Some studies show that the body temperature of lizards is more related to phylogenetic than ecological factors, suggesting that species of the same genus tend to have similar body temperatures even occurring in different types of environments. In general, regardless of the locality and latitude along the eastern coast of Brazil, the different species of lizards of the genus Cnemidophorus and their respective populations have similar body temperatures in activity and the apparent differences result from the influence of the local thermal environment of each restinga.     

Thermal behavior of the Pacific sardine (Sardinops sagax) acclimated to different thermal cycles

The study of thermal behavior of fishes provides useful data to enable predictions of the effect of climatic change on populations so as to ensure good management of fisheries. The Pacific sardine has a complex population dynamics; three subpopulation have been proposed (cold, temperate and warm).We exposed Sardinops sagax caeruleus (temperate sub-population) to two different thermal cycles, which were chosen to be consistent with the temperatures reported in two distant places Cedros Island (CIc: 18–23 °C) and San Pedro (SPc: 13–18 °C).The thermal behavior of the SPc and CIc sardines was affected by acclimation treatment: the interval of thermal preference was 17.1–19.9 and 16.0–18.8 °C, while the lethal temperatures interval (LT50) was 7.7–25.6 and 6.9–24.3 °C, and the critical limits CTMax and CTMin were 7.1–32.2 and 5.5–30.4 °C, respectively.The results of thermal behavior showed that sardines of the temperate subpopulation are more tolerant to cold; this might suggest that they would be more able to survive in California and Oregon than in Baja California Sur and the Gulf of California.