Surface behavior of pelagic juvenile loggerhead sea turtles in the eastern North Atlantic

Sea turtles bask at the ocean surface, but little is known about the patterns and ecological context of surface behavior in the wild. This study investigated the surface behavior of ten juvenile loggerhead sea turtles (34 - 58 cm straight carapace length) satellite tagged in Madeira, in the pelagic eastern North Atlantic. During a total of 2273 tracking days, turtles moved through oceanic areas with a mean depth of ~3400 m. On average, turtles spent one third of the time at the surface (0 - 1 m depth), spending 43% of the time at the surface during the day and 29% of the time during the night. Generalized linear mixed modelling showed that the proportion of time at the surface was significantly larger during the day, particularly during spring and summer. Time spent at the surface during the day increased with elevated air temperatures and weak winds, probably to maximize the benefits of solar absorption. Conversely, the probability of being at the surface during the day decreased as horizontal search effort increased, suggesting a trade-off between basking and daytime foraging activities. At night, time spent at the surface was not associated with air temperature or wind speed but was instead positively associated with moon illumination. As turtles tend to dive deeper during clear nights, increased surface time may be needed to recover from deeper dives. This study presents important aspects of the behavioral ecology of the species during the oceanic juvenile phase. The findings reported here may be relevant for species management and conservation, including correction of census data and management of interactions with surface fishing gear and other anthropogenic activities.info:eu-repo/semantics/publishedVersio

Blood biochemistry reference values for wild juvenile loggerhead sea turtles (Caretta caretta) from Madeira archipelago

Standard biochemical parameters were determined in wild juvenile loggerhead sea turtles Caretta caretta living offshore Madeira Island, northeast Atlantic. We analyzed the influence of age, sex, sea surface temperature, and body condition index on biochemical parameters including uric acid, total bilirubin, total cholesterol, creatinine kinase (CK), glucose, total protein, urea nitrogen, lactate dehydrogenase, aspartate aminotranspherase (AST), gamma-glutamyl transferase (GGT), albumin, alkaline phosphatase (ALP), sodium (NA), potassium (K), chloride, calcium, phosphorus, and magnesium. Significant positive correlations were found between turtle body size and total cholesterol, total protein, and albumin. Total protein and the enzymes AST and CK were lower than reported levels in adults. Calcium levels were lower than those reported in adult or captive turtles, but similar to wild juveniles from Australian waters, and were interpreted as normal for this age category. These data may be useful to evaluate the health status of stranded or injured animals and to improve veterinary care at rehabilitation centers.info:eu-repo/semantics/publishedVersio

Larval cestodes infecting the deep-water fish, Cataetyx laticeps (Pisces: Bythitidae) from Madeira Archipelago, Atlantic Ocean

Parasites of deep-water fishes are less known in comparison to the parasites of fishes living in the demersal and epipelagic ocean zones. In the present research note we report the occurrence of larval trypanorhynch cestodes in a rare deep-water fish, the deep-water brotula, Cataetyx laticeps. Based on the 28S rDNA (region D1-D3) sequence homology and the phylogenetic analysis, the larval cestodes are putatively assigned to the genus Grillotia. It is suggested that the definitive host of this trypanorhynch is a batoid.info:eu-repo/semantics/publishedVersio

Identification of likely foraging habitat of pelagic loggerhead sea turtles (Caretta caretta) in the North Atlantic through analysis of telemetry track sinuosity

Changes in the behavior of individual animals in response to environmental characteristics can provide important information about habitat preference, as well as the relative risk that animals may face based on the amount of time spent in hazardous areas. We analyzed movement and habitat affinities of ten log gerhead turtles (Caretta caretta) tagged with satellite transmitters in the spring and fall of 1998 near Madeira, Portugal for periods of 2–10 months. We analyzed the behavior of these individuals in relation to the marine environment they occupied. As a measure of behavior we calculated the straightness index (SI), the ratio of the displacement of the animal to the total distance traveled, for individual weekly seg ments of the 10 tracks. We then extracted information about chlorophyll a concentration, sea-surface temperature (SST), bathymetry, and geostrophic current of the ocean in a 20-km buffer surrounding the tracks, and examined their relationship to the straightness index using generalized linear models. Chlorophyll a value, bathymetry and SST were significantly related to the straightness index of the tracks of all ten animals, as was the circular standard deviation of the geostrophic current (Wald’s test: p = 0.001, p = 0.008, p = 0.025, and p = 0.049, respectively). We found a significant negative relationship between straightness index and chlorophyll, and positive relationships with ocean depth and SST indicat ing that animals are spending more time and searching more thoroughly in areas with high chlorophyll concentrations and in areas that are shallower, while moving in straight paths through very warm areas. We also found a positive relationship between straightness index and the circular standard deviation of surrounding geostrophic currents suggesting that these turtles are more likely to move in a straight line when in the presence of diffuse, less-powerful currents. Based on these relationships, we propose that conservation planning to reduce overlap of turtles with fishing operations should take into account the locations of bathymetric features such as seamounts and upwelling locations where chlorophyll concen trations are high. This analysis is an effective way to characterize areas of high-use habitat for satellite tagged marine vertebrates, and allows for comparisons of these characteristics between species and among individuals.info:eu-repo/semantics/publishedVersio

Evidence for trophic differences between live and bycatch oceanic juvenile loggerhead sea turtles

The loggerhead sea turtle Caretta caretta is a vulnerable migratory species that spends its frst years of life in the open sea. During this developmental phase, loggerheads can be found foraging in the epipelagic zone of the waters surrounding the Madeira Archipelago, providing a rare opportunity to gather information on the ecology of its oceanic developmental stage. In this study, we characterized the isotopic niche of these juveniles, using stable isotope analysis. We assessed two groups of turtles, turtles captured alive (n=24) and turtles captured as bycatch on local longlines (n=12), and explored whether animals caught in the local fshing gear represented a random sample of the population, or whether there is some evidence for a specialized foraging behaviour. We found that turtle bycatch had a signifcantly higher mean stable nitrogen isotope value in whole blood (δ15N=8.5±0.6‰ SD) compared to the group of turtles captured alive in the same period (δ15N=7.6±0.5‰ SD), indicating that they had a diferent diet. While there was a tendency for turtle bycatch to be slightly larger, we found no efect of body size on δ15N values. We propose a distinct foraging behaviour strategy hypothesis, with a group of turtles being more susceptible to interactions with fsheries and thus having a higher mortality risk, which should motivate the implementation of existing guidelines to reduce sea turtle bycatch.info:eu-repo/semantics/publishedVersio

Compensatory growth in oceanic loggerhead sea turtles: response to a stochastic environment

Compensatory growth (CG, accelerated growth that may occur when an organism that has grown at a reduced rate as a result of suboptimal environmental conditions is exposed to better conditions) is considered an adaptation to variable en vironments. Although documented thoroughly under captive conditions, CG has rarely been studied in wild populations. In their first years of life, oceanic-stage loggerhead sea turtles (Caretta caretta) have relatively little control over their geographic position or movements and thus have an extremely stochastic lifestyle with great variation in food availability and temperature. This environmental variation results in variable growth rates. We evaluate somatic growth functions of oceanic-stage loggerheads from the eastern Atlantic based on skeletochronology that allowed us to assign age and cohort to each individual. We demonstrate CG in these turtles based on three different analytical approaches: changes in coefficients of variation in size-at-age, generalized additive model regression analyses of somatic growth, and linear regression of age-specific growth rates. As a result of CG, variation in size-at-age in these juvenile loggerheads is substantially reduced. Thus, size is a better predictor of age than expected based on variation in growth rates. CG decreases with age, apparently as loggerheads gain greater control over their movements. In addition, we have evaluated for the first time in wild sea turtles the time-dependent nature of somatic growth by distinguishing among age, year, and cohort effects using a mixed longitudinal sampling design with assigned-age individuals. Age and year had significant effects on growth rates, but there was no significant cohort effect. Our results address critical gaps in knowledge of the demog raphy of this endangered species.info:eu-repo/semantics/publishedVersio

Considerations on the biology of Plesionika narval (Fabricius, 1787) in the Northeastern Atlantic

Life history traits of Plesionika narval were studied in the Northeastern Atlantic, Madeira archipelago including growth, age, sexual maturity, recruitment pattern and mortality. A total of 28,262 specimens were sampled over a period of 8 years comprising two time series from 1991 to 1995 and 2004 to 2008. The relative growth pattern showed a negative allometric nature of growth for combined sexes, males, females, non ovigerous and ovigerous females. Estimated asymptotic carapace length (CL∞) and growth coefficient (K) showed higher values in females (CL∞=30.21 mm, K=0.450 year-1 ) comparatively to males (CL∞=28.61 mm, K=0.430 year-1 ), resulting in better overall growth performance in females. The maximum life span (tmax) was estimated at 6.81 years for combined sexes, 6.97 for males and 6.66 for females, however 99.95% of the individuals were younger than 3 years. Although a seasonal spawning season was evident from late summer to late autumn, reproduction may be prolonged throughout the year since ovigerous females are present in all months and achieving sexual maturity at 14.61 mm. The recruitment pattern was continuous throughout the year with a major peak occurring in spring. The total mortality (Z) and fishing mortality (F) were higher in females than in males while natural mortality (M) was similar between groups.info:eu-repo/semantics/publishedVersio

Temperature control on CO2 emissions from the weathering of sedimentary rocks

Sedimentary rocks can release carbon dioxide (CO2) during the weathering of rock organic carbon and sulfide minerals. This sedimentary carbon could act as a feedback on Earth’s climate over millennial to geological timescales, yet the environmental controls on the CO2 release from rocks are poorly constrained. Here, we directly measure CO2 flux from weathering of sedimentary rocks over 2.5 years at the Draix-Bléone Critical Zone Observatory, France. Total CO2 fluxes approached values reported for soil respiration, with radiocarbon analysis confirming the CO2 source from rock organic carbon and carbonate. The measured CO2 fluxes varied seasonally, with summer fluxes five times larger than winter fluxes, and were positively correlated with temperature. The CO2 release from rock organic carbon oxidation increased by a factor of 2.2 when temperature increased by 10 °C. This temperature sensitivity is similar to that of degradation of recent-plant-derived organic matter in soils. Our flux measurements identify sedimentary-rock weathering as a positive feedback to warming, which may have operated throughout Earth’s history to force the surface carbon cycle

Elastic biodegradable starch/ethylene-co-vinyl alcohol fibre-mesh scaffolds for tissue engineering applications

The fabrication of a biomaterial scaffold, with adequate physical and structural properties for tissue engineering applications, is reported. A blend of starch with ethylene-vinyl alcohol (50/50 w/w, SEVA-C) is used to produce 3D fibre-mesh scaffolds by wet-spinning. The scaffolds are characterized in terms of morphology, porosity, interconnectivity, and pore size, using scanning electron microscopy (SEM) and microcomputed tomography (μCT). The degradation behavior, as well as the mechanical properties of the scaffolds, is investigated in presence of alpha-amylase enzyme at physiological concentration. Scaffolds with porosities ranging from 43 to 52%, interconnectivity of ∼70.5% and pore size between 118 and 159 μm, can be fabricated using the proposed methodology. The scaffolds exhibit an elastic behavior in the wet state with a compressive modulus of 7.96±0.32 MPa. Degradation studies show that SEVA-C scaffolds are susceptible to enzymatic degradation by alpha-amylase, confirmed by the increase of weight loss (40% of weight loss after 12 weeks) and presence of degradation products (reducing sugars) in solution. The diameter of SEVA-C scaffolds decreases with degradation time, increasing the overall porosity, interconnectivity and pore size. In vitro cell studies with human osteosarcoma cell line (SaOs-2) showed a nontoxic and cytocompatible behavior of the developed fibre mesh scaffolds. The positive cellular response, together with structural and degradable properties, suggests that 3D SEVA-C fibre-meshes may be good candidates as tissue engineering scaffolds. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40504. Copyright © 2014 Wiley Periodicals, Inc.This work was supported by national funds through the Portuguese Foundation for Science and Technology under the scope of the project PTDC/CTM/67560/2006 and by the European Regional Development Fund (ERDF) through the Operational Competitiveness Programme “COMPETE” (FCOMP-01-0124-FEDER-007148)

Anti-Plasmodium activity of ceramide analogs

BACKGROUND: Sphingolipids are key molecules regulating many essential functions in eukaryotic cells and ceramide plays a central role in sphingolipid metabolism. A sphingolipid metabolism occurs in the intraerythrocytic stages of Plasmodium falciparum and is associated with essential biological processes. It constitutes an attractive and potential target for the development of new antimalarial drugs. METHODS: The anti-Plasmodium activity of a series of ceramide analogs containing different linkages (amide, methylene or thiourea linkages) between the fatty acid part of ceramide and the sphingoid core was investigated in culture and compared to the sphingolipid analog PPMP (d,1-threo-1-phenyl-2-palmitoylamino-3-morpholino-1-propanol). This analog is known to inhibit the parasite sphingomyelin synthase activity and block parasite development by preventing the formation of the tubovesicular network that extends from the parasitophorous vacuole to the red cell membrane and delivers essential extracellular nutrients to the parasite. RESULTS: Analogs containing methylene linkage showed a considerably higher anti-Plasmodium activity (IC(50 )in the low nanomolar range) than PPMP and their counterparts with a natural amide linkage (IC(50 )in the micromolar range). The methylene analogs blocked irreversibly P. falciparum development leading to parasite eradication in contrast to PPMP whose effect is cytostatic. A high sensitivity of action towards the parasite was observed when compared to their effect on the human MRC-5 cell growth. The toxicity towards parasites did not correlate with the inhibition by methylene analogs of the parasite sphingomyelin synthase activity and the tubovesicular network formation, indicating that this enzyme is not their primary target. CONCLUSIONS: It has been shown that ceramide analogs were potent inhibitors of P. falciparum growth in culture. Interestingly, the nature of the linkage between the fatty acid part and the sphingoid core considerably influences the antiplasmodial activity and the selectivity of analogs when compared to their cytotoxicity on mammalian cells. By comparison with their inhibitory effect on cancer cell growth, the ceramide analogs might inhibit P. falciparum growth through modulation of the endogenous ceramide level