Comparison of fecal glucocorticoid metabolite concentrations in hand- versus parent-reared whooping cranes (Grus americana)

Endangered whooping cranes (Grus americana) have been produced in captivity for reintroduction programs since the 1980s, using techniques such as artificial insemination, multiple clutching, and captive-rearing to speed recovery efforts. Chicks are often hand-reared (HR) by caretakers in crane costumes, socialized into groups and released together, unlike parent-reared (PR) cranes that are raised individually by a male/female crane pair and released singly. HR cranes historically exhibit greater morbidity rates during development than PR cranes, involving musculoskeletal and respiratory system disease, among others. We hypothesized that HR crane chicks exhibit a higher baseline fecal glucocorticoid metabolite (FGM) concentrations during the development compared with PR chicks. Fecal samples were collected between 15 and 70 days of age from HR (n = 15) and PR (n = 8) chicks to test for differences in FGM concentrations using a radioimmunoassay technique following ethanol extraction for steroids. Linear mixed model analysis suggests increasing age of the chick was associated with an increase in FGM (p < .001). Analysis also supported the interaction between rearing strategy and sex of the crane chick (p < .01). Female PR chicks had greater FGM concentrations than all other groups (PR male, p < .01; HR female, p < .001; and HR male, p < .001). This result suggests that there may be an effect of rearing strategy on stress physiology of whooping crane chicks, especially among females. Further research is needed to investigate whether the FGM concentrations are reflective of true differences in stress physiology of young cranes and whether this may impact health and conservation success.     

Male-male competition and repeated evolution of terrestrial breeding in Atlantic Coastal Forest frogs*

Terrestrial breeding is a derived condition in frogs, with multiple transitions from an aquatic ancestor. Shifts in reproductive mode often involve changes in habitat use, and these are typically associated with diversification in body plans, with repeated transitions imposing similar selective pressures. We examine the diversification of reproductive modes, male and female body sizes, and sexual size dimorphism (SSD) in the Neotropical frog genera Cycloramphus and Zachaenus, both endemic to the Atlantic rainforest of Brazil. Species in this clade either breed in rocky streams (saxicolous) or in terrestrial environments, allowing us to investigate reproductive habitat shifts. We constructed a multilocus molecular phylogeny and inferred evolutionary histories of reproductive habitats, body sizes, and SSD. The common ancestor was small, saxicolous, and had low SSD. Terrestrial breeding evolved independently three times and we found a significant association between reproductive habitat and SSD, with shifts to terrestrial breeding evolving in correlation with decreases in male body size, but not female body size. Terrestrial breeding increases the availability of breeding sites and results in concealment of amplexus, egg-laying, and parental care, therefore reducing male-male competition at all stages of reproduction. We conclude that correlated evolution of terrestrial reproduction and small males is due to release from intense male-male competition that is typical of exposed saxicolous breeding.     

Trophic ecology and metabolism of two species of nonnative freshwater stingray (Chondrichthyes: Potamotrygonidae)

The stingrays Potamotrygon amandae and Potamotrygon falkneri are nonnative species established in the Upper Paraná basin. Although they are widely distributed, few studies on their diets or respective metabolic responses exist. Therefore, the aim was to evaluate the dietary composition, trophic niche breadth and lipid/protein concentrations in muscle and hepatic tissues of these two species, as well as the interrelationships between them. The individuals were collected in two areas on the Upper Paraná River. The stomachs and samples of muscle and liver tissues were taken for analysis. A broad dietary spectrum was observed for both species, along with differences in dietary composition, with a higher consumption of detritus by P. amandae and Baetidae by P. falkneri. No differences were observed in the trophic niche breadth. Regarding the metabolic variables, differences were only found in the hepatic protein, with a higher content observed in P. falkneri. A significant positive correlation was observed between items of animal origin and detritus with muscle protein for this species. This shows that such feeding habits, which are characteristic of a generalist, influenced the metabolism of the species and possibly contributed to the successful adjustment of the species to new habitats in the Upper Paraná River.

     

Trophic niche partitioning of five skate species of genus Bathyraja in northern and central Patagonia,Argentina

Overexploitation of marine communities can lead to modifications in the structure of the food web and can force organisms like elasmobranchs to change their feeding habits. To evaluate the impact that fisheries have on food webs and on the interactions between species, it is necessary to describe and quantify the diet of the species involved and follow it through time. This study compares the diet of five skate species using the data obtained from the by-catch of the Argentine hake (Merluccius hubbsi) fishery in north and central Patagonia, Argentina. Diet composition was assessed by analysing the digestive tract contents and trophic overlapping between species of the genus Bathyraja: Bathyraja albomaculata, Bathyraja brachyurops, Bathyraja macloviana, Bathyraja magellanica and Bathyraja multispinis. A total of 184 stomachs were analysed. The diets of B. albomaculata and B. macloviana mainly comprised annelids, whereas that of B. brachyurops primarily comprised fish, including hake heads discarded by the fishery. The diets of B. magellanica and B. multispinis were largely based on crustaceans. Despite the morphological similarities and their shared preference for benthic habitats, no complete diet overlaps were found between the different species. These results suggest that these skate species have undergone a process of diet specialisation. This is a common feeding strategy that occurs to successfully eliminate competition when resources are limited, which corresponds to the conditions found in an environment being affected by the pressures of overfishing.     

Phenotypic and genetic differentiation between diadromous and landlocked puyen Galaxias maculatus

This study reports the phenotypic and genetic differences between individuals of puyen Galaxias maculatus from two sites in the same river basin in Tierra del Fuego National Park, southern South America. Individuals from the two sampling sites presented morphometric and genetic differences. The morphometric differences indicated that individuals from Laguna Negra (LN) were short and more robust and had large eyes, whereas those from Arroyo Negro (AN) were thin and elongated and had small eyes. Genetic differences showed that AN individuals had a greater genetic structuration and an older demographic history than LN individuals. The results of this study affirmed that the individuals from the two sampling sites belong to different populations with a high degree of isolation. The demographic history could indicate that the individuals of G. maculatus which migrated to northern areas during the last glaciation settled in the Beagle Channel after its formation. The LN population could have originated after the retreat of the glaciers, migrating from AN.     

Visualization of embolism formation in the xylem of liana stems using neutron radiography

Background and Aims

Cold neutron radiography was applied to directly observe embolism in conduits of liana stems with the aim to evaluate the suitability of this method for studying embolism formation and repair. Potential advantages of this method are a principally non-invasive imaging approach with low energy dose compared with synchrotron X-ray radiation, a good spatial and temporal resolution, and the possibility to observe the entire volume of stem portions with a length of several centimetres at one time.

Methods

Complete and cut stems of Adenia lobata, Aristolochia macrophylla and Parthenocissus tricuspidata were radiographed at the neutron imaging facility CONRAD at the Helmholtz-Zentrum Berlin für Materialien und Energie, with each measurement cycle lasting several hours. Low attenuation gas spaces were separated from the high attenuation (water-containing) plant tissue using image processing.

Key results

Severe cuts into the stem were necessary to induce embolism. The formation and temporal course of an embolism event could then be successfully observed in individual conduits. It was found that complete emptying of a vessel with a diameter of 100 µm required a time interval of 4 min. Furthermore, dehydration of the whole stem section could be monitored via decreasing attenuation of the neutrons.

Conclusions

The results suggest that cold neutron radiography represents a useful tool for studying water relations in plant stems that has the potential to complement other non-invasive methods.     

Experimental evidence of habitat selection and territoriality in the Amazonian whip spider Heterophrynus longicornis (Arachnida, Amblypygi)

Animals that select and defend suitable habitats against conspecifics may be favored by maximizing prey encounter rate, gaining protection, or securing matings. However, the identification of habitat selection and territoriality may be hindered in observational studies in sedentary species with low-density populations, such as the whip spider Heterophrynus longicornis. To circumvent such difficulties, we adopted an experimental field approach to evaluate if H. longicornis selects and defends habitat in Central Amazon. To evaluate whether individuals perform habitat selection, we monitored the permanence of 29 experimentally released individuals in buttressed trees with a wide variation in diameter at breast height (DBH), with and without burrows at their bases. To evaluate whether individuals are territorial, we experimentally removed 21 individuals from their previously occupied trees and monitored the recolonization of these trees. If H. longicornis were territorial, we predicted that the recolonizers would be smaller than the removed individuals. We found 12 individuals in the trees where they were released on subsequent days, none of them in trees without burrows. The individual permanence was related to the presence of burrows, and not to DBH. There was recolonization by smaller males and females on ten trees from which the amblypygids were removed. In combination, the permanence of individuals in trees with burrows, the rapid recolonization of experimentally vacated trees by smaller individuals, and the preponderance of one individual per tree, suggest that both male and female H. longicornis perform habitat selection and also that after selecting a site, they defend it against conspecifics.     

Sequential foraging of dusky dolphins with an inspection of their prey distribution

The aim of this work was to analyze the sequential foraging behavior of dusky dolphins (Lagenorhynchus obscurus). Foraging sequences were defined when more than two feeding bouts occur with a traveling bout between them. We hypothesized that traveling costs of searching for prey patches were related to the time spent feeding on a patch. In addition, the distribution and seasonal variation of anchovy schools were studied in the area to better understand dolphins' behavior. We observed dolphins from a research vessel from 2001 to 2007, and recorded their location and behavior. Anchovy data were collected during two hydro‐acoustic surveys. Dusky dolphin behaviors varied seasonally; they spent a greater proportion of time traveling and feeding in the warm season (Kruskal‐Wallis: H = 172.07, P < 0.01). During the cold season dolphin groups were more likely to exhibit diving behavior and less surface feeding. We found a positive correlation between searching and foraging time (r = 0.88, P = 0.019), suggesting that the costs associated with searching were compensated by an increase in the energy intake during the foraging bout. There was an association between dusky dolphin and anchovy distribution, in that they co‐varied spatially and seasonally.     

Global biostratigraphic comparison and correlation of an early Cisuralian palynoflora from Bolivia

This paper presents new data about Early Permian (Cisuralian) strata, palynostratigraphy and absolute dating from the Copacabana Formation in central Bolivia. Recent stratigraphic and palynologic data from marine and transitional rocks at Apillapampa refine the age of Cisuralian palynomorphs in South America. Twelve samples interbedded with five volcanic ashes (processed and productive) yielded 94 palynomorph species arranged in two informal palynoassemblages: the lower assemblage Vittatina costabilis corresponds to one sample near the base of the Copacabana Formation and the upper Lueckisporites virkkiae assemblage occurs in overlying marine and coal-bearing transitional intervals. Ages were also independently refined by a modern review of conodonts, fusulinids, along with those U–Pb radiometric ages (Isotope Dilution Thermal Ionization Mass Spectrometry [ID-TIMS] of zircon-bearing interbedded tuffs). These data suggest that the lower marine member of the Copacabana Formation at this location is Asselian and Sakmarian. Lueckisporites virkkiae is a key species of palynomorph utilised in South American and global Permian biostratigraphic reconstructions. Hence, a thorough global comparison of these palynofloras and correlations is addressed in this contribution, considering first appearances of mainly cosmopolitan diagnostic taxa. Correlations are established with many similar Permian palynofloras, some also constrained with radiometric data, in South America (Brazil, Uruguay and Argentina) and elsewhere.