Foraging ecology of leatherback sea turtles in the Western North Atlantic determined through multi-tissue stable isotope analyses

Leatherback turtles, Dermochelys coriacea, are highly migratory, spending most of their lives submerged or offshore where their feeding habits are difficult to observe. In order to elucidate the foraging ecology of leatherbacks off Massachusetts, USA, stable isotope analyses were performed on leatherback tissues and prey collected from 2005 to 2009. Stable isotope ratios of nitrogen and carbon were determined in whole blood, red blood cells, blood plasma, muscle, liver, and skin from adult male, female, and subadult leatherbacks. Isotopic values were analyzed by body size (curved carapace length) and grouped by sex, and groups were tested for dietary differences. Gelatinous zooplankton samples were collected from leatherback foraging grounds using surface dip nets and stratified net tows, and prey contribution to leatherback diet was estimated using a two-isotope Bayesian mixing model. Skin and whole blood δ¹³C values and red blood cell δ¹⁵N values were correlated with body size, while δ¹³C values of red blood cells, whole blood, and blood plasma differed by sex. Mixing model results suggest that leatherbacks foraging off Massachusetts primarily consume the scyphozoan jellyfishes, Cyanea capillata and Chrysaora quinquecirrha, and ctenophores, while a smaller proportion of their diet comes from holoplanktonic salps and sea butterflies (Cymbuliidae). Our results are consistent with historical observations of leatherback turtles feeding on scyphozoan prey in this region and offer new insight into size- and sex-related differences in leatherback diet.     

Sex differences in the ontogeny of social behavior in pikas: possible relationships to dispersal and territoriality

Summary A laboratory study on the ontogeny of social behavior in pikas (Ochotona princeps), an alpine lagomorph, was conducted to determine the role of early relationships between adult females and young and among siblings in the development of territorial and dispersal behaviors. Sex differences during development were examined because field studies have reported greater dispersal distances in young females than young males. At birth, females were significantly heavier than males. There were no sex differences in nursing frequency until after the 2nd week of age, when males initiated more nursing attempts than females. By the end of the weaning period (weeks 5 and 6), adult females became non-interactive with young, but aggression of young toward littermates and the mother increased until the eighth week. At this time, young males outweighed their sibling females. Young were dominant over their mothers by the age of 5 weeks, and young males were dominant over their sibling females.Sex differences were observed in aggression, scent-marking, exploratory activity, and submissive vocalizations, with higher rates in young males, except for submissive vocalizations, which were higher in females (Table 2). Vocalizations and scent-marking behavior increased over time, and were positively correlated with interaction rates.These data support the hypothesis that female young disperse farther than male young largely as the result of unsuccessful competition with male siblings for available territories close to the birthplance. A dispersal strategy for pkkas is proposed.     

Reproductive status and body condition of Atlantic bluefin tuna in the Gulf of Maine, 2000–2002

The reproductive status and body condition of 195 (≥185 cm curved fork length, CFL; assigned age 7 and above) Atlantic bluefin tuna were assessed in the Gulf of Maine during the commercial fishing season of June–October, 2000–2002. Given the distance between known spawning and feeding grounds, the prevailing paradigm for Atlantic bluefin tuna (Thunnus thynnus thynnus, L.) suggests that the most likely histological state for females arriving in the Gulf of Maine after spawning would be a resting or quiescent state with little or no perigonadal fat. Alternatively, the presence of mature or mature-inactive histological states in some females supports a more varied or individualistic model for bluefin reproduction. No relationship was found between body condition and reproductive status. Males were found in all reproductive stages, but were more likely to be in spawning condition (stages 4 and 5) or a mature-inactive state (stage 6) in June and July. Female bluefin tuna were found in stage 1 (immature or non-spawning) and stage 6 (mature-inactive). Stage 6 females were only present in June and July and smaller females (<235 cm CFL) were more likely to be in stage 6 than large females (>235 cm CFL) sampled during those same months. The presence of smaller females in stage 6 arriving at the same time as larger females in stage 1 indicates that Western Atlantic bluefin tuna may have an asynchronous reproductive schedule and may mature at a smaller size than the currently accepted paradigm suggests.     

Assessment and individual recognition of opponents in the pygmy swordtails Xiphophorus nigrensis and X. multilineatus

We examined factors that determine the outcome of agonistic encounters between male pygmy swordtail fish. Xiphophorus nigrensis and X. multilineatus males formed dominance relationships based on body size in staged laboratory encounters. There was a significant negative correlation between size asymmetry and fight intensity, suggesting that males assessed size in the encounters. However, a significant proportion of the variation in fight intensity in contests that escalated to bites could not be explained by size asymmetry. Aggressive motivation may also influence the outcome of contests and could be assessed in agonistic encounters. Theory suggests that signals of aggressive intention will be evolutionarily stable if individuals can recognize opponents and encounter one another repeatedly. In addition, individual recognition is one way that dominance hierarchies can be maintained. Here we demonstrate that males from both species can recognize individuals. In addition, at least some X. nigrensis males were site-faithful in the field, suggesting males encounter the same opponents repeatedly.Communicated by G.M. Klump     

Prenatal diagnosis of conjoined twins

A case of conjoined twins with open spina bifida prenatally diagnosed at the twenty-third week of gestation is presented. The early detection of this rare and unusual malformation was initiated by the observation of markedly elevated maternal serum alphafetoprotein values. Ultrasound evidence of a misshaped cephalic pole and the appearance of one fetal body on real-time ultrasound was strongly suggestive. Elective midtrimester termination confirmed the prenatal diagnosis and was followed by a benign postpartum course.     

Forests in climate policy: technical,institutional and economic issues in measurement and monitoring

Despite the economic and environmental significance of the world’s forests, we have limited data about them. Estimates of deforestation in tropical countries and rates of reforestation or afforestation in boreal and temperate countries are inconsistent. Accordingly, estimates of emissions released in deforestation vary widely and range from 7% to 17% of all sources of greenhouse gas (GHG) emissions. The lack of good data severely hampers efforts to shape climate policy because it is difficult to model the role of forests both in the physical global carbon (C) cycle and in cost-effective regimes to abate GHG. Data limits strain the capacity of even the best models to estimate marginal cost functions for forest carbon (C) sequestration. It is technically possible to obtain better information, but for institutional and economic reasons these technologies have not yet been fully deployed. The emergence of carbon (C) trading or tax policy in which forest carbon (C) storage becomes valued would strengthen incentives to supply better data, as would nonmarket regulation if it elicited a shadow value of forest carbon (C) in substituting for reductions in greenhouse gas emissions. “Geo-wiki” may provide a short-term solution to at least part of the data problem. The ultimate solution is the development of a comprehensive forest monitoring system involving remote sensing and on-the-ground truthing. This paper briefly discusses the role of forests in climate policy and then describes data gaps, the capability of technology to fill them, the limits of institutions and budgets in realizing this capability, and possible near-term solutions.     

A pilot study to assess residential endotoxin and blood IgE in a group of pregnant women from Trujillo, Peru

OBJECTIVE: This November 2003 pilot study investigates the correlation between serum IgE and residential endotoxin levels from a group of 18 pregnant women living in Trujillo, Peru, and investigates the impact of the demographic and lifestyle factors of this group on the IgE and endotoxin levels measured. METHODS: Serum samples were collected from 19 subjects and analyzed for IgE. Dust samples were collected from the mattresses of 18 subjects and measured for endotoxin levels. A questionnaire was used to obtain demographic, socioeconomic, and lifestyle information for each subject. RESULTS: Geometric means for IgE and endotoxin were 246.8 (GSD=4.3, n=19) IU/mL and 66.5 EU/mg (GSD=1.7, n=18), respectively. Log-transformed IgE and endotoxin were not correlated (R2=0.02; p=0.60). CONCLUSIONS: Residential endotoxin and serum IgE were not correlated in this group. Potential selection bias and sample size are major limitations of the study. However, 74% (14/19) of the subjects in this study had an IgE over 100 IU/mL, a level generally considered elevated.     

Remote sensing technology and land use analysis in food security assessment

ABSTRACT

Climate change and a rapidly growing human population have put ever greater strains on the global food system. Although the number of food insecure people in the world has reached a record low, changing land use and climate variability will threaten our ability to maintain this progress. Profound changes in the structure of economies around the world have affected agricultural production and how food is delivered to the consumer. This paper explores connections between land use, environmental change and food availability, access, and utilization. Each of these elements of food security has vulnerabilities to changing environmental conditions and land use that can be explored using satellite remote sensing observations. Technology is a key way environmental changes can be quantified and used in food security assessment.     

Compensatory responses to loss of warming-sensitive plant species

Climate warming-induced plant species loss is likely to be nonrandom and based on species-specific susceptibility to changing climate. We examined the ecological consequences of losing shallow-rooted forbs, a group of species we predict to be adversely affected by climate change based on their response to experimental warming. After three years of experimental species removal, tap-rooted forbs and grasses were able to fully compensate for the loss of shallow-rooted forbs with increased biomass production. Moreover, the remaining plant community yielded a larger biomass response to nitrogen addition when shallow-rooted forbs were removed, possibly because removal led to increased soil moisture. We conclude that, although shallow-rooted forbs share a common response to warming, their loss did not affect community-level biomass. However, the loss of shallow-rooted forbs could result in increased sensitivity to perturbations, such as changing nutrient availability. Our results demonstrate that realistic, nonrandom scenarios of species loss do not necessarily follow the general pattern of decreased productivity and dampened response to nitrogen addition with species loss that is predicted by theory and many experimental results. Further examinations of nonrandom species loss in other ecosystems are needed to further improve our understanding of the consequences of human-driven species loss.     

Variability of albacore (<Emphasis Type="Italic">Thunnus alalunga</Emphasis>) diet in the Northeast Atlantic and Mediterranean Sea

This study aims to describe the variability of albacore (Thunnus alalunga) diet in the Northeast Atlantic and Mediterranean Sea and to identify possible relationships between this variability and the features of different feeding areas, the behavior, and the energetic needs of albacore. Stomach contents from albacore caught in five zones of the Bay of Biscay and surrounding waters (n = 654) and three zones of the Mediterranean Sea (n = 152) were analyzed in terms of diet composition and stomach fullness. Carbon and nitrogen stable isotope and C/N ratios were measured for white muscle and liver from albacore in the Bay of Biscay (n = 41) and Mediterranean Sea (n = 60). Our results showed a spatial, seasonal, inter-annual, and size-related variability in the diet of albacore. Albacore diet varied by location in the Mediterranean Sea, with a particularly high proportion of cephalopods, and low δ¹⁵N values in the Tyrrhenian Sea. In the Northeast Atlantic, albacore consumed a higher proportion of crustaceans and a lower proportion of fishes in the most offshore sampling zone than inshore. The digestion states of the major prey reflected a diurnal feeding activity, indicative of feeding in deeper waters offshore, whereas on the continental slope, feeding probably occurred in surface waters at night. Important seasonal and inter-annual diet variability was observed in the southeast of the Bay of Biscay, where preferred albacore prey appeared to be anchovy (Engraulis encrasicolus). Stomach fullness was inversely related to body size, probably reflecting higher energetic needs for smaller individuals. Albacore from the Bay of Biscay had significantly lower δ¹³C and higher δ¹⁵N values compared with albacore from the Mediterranean Sea, indicative of regional baseline shifts, and trophic position and muscle lipid stores in albacore increased with body size.