The Population Decline and Extinction of Darwin's Frogs

Darwin's frogs (Rhinoderma darwinii and R. rufum) are two species of mouth-brooding frogs from Chile and Argentina. Here, we present evidence on the extent of declines, current distribution and conservation status of Rhinoderma spp.; including information on abundance, habitat and threats to extant Darwin's frog populations. All known archived Rhinoderma specimens were examined in museums in North America, Europe and South America. Extensive surveys were carried out throughout the historical ranges of R. rufum and R. darwinii from 2008 to 2012. Literature review and location data of 2,244 archived specimens were used to develop historical distribution maps for Rhinoderma spp. Based on records of sightings, optimal linear estimation was used to estimate whether R. rufum can be considered extinct. No extant R. rufum was found and our modelling inferred that this species became extinct in 1982 (95% CI, 1980-2000). Rhinoderma darwinii was found in 36 sites. All populations were within native forest and abundance was highest in Chiloé Island, when compared with Coast, Andes and South populations. Estimated population size and density (five populations) averaged 33.2 frogs/population (range, 10.2-56.3) and 14.9 frogs/100 m(2) (range, 5.3-74.1), respectively. Our results provide further evidence that R. rufum is extinct and indicate that R. darwinii has declined to a much greater degree than previously recognised. Although this species can still be found across a large part of its historical range, remaining populations are small and severely fragmented. Conservation efforts for R. darwinii should be stepped up and the species re-classified as Endangered

Dietary and digestive constraints on basal energy metabolism in a small herbivorous rodent

McNab (1986, 1988) has hypothesized that mammals using food with low energy content should exhibit basal metabolic rates (BMR) lower than those expected on the basis of their body mass (mb). That is, those species that exploit food with low energy content and/or high cost of digestion tend to have low, mass-independent metabolic rates. To date there is not an experimental test of this pattern. The aim of this work was to examine experimentally the effect of diet quality on BMR, digestive efficiency, and the relationship between digestion and energy expenditure in a small herbivorous mammal. We used as a model the herbivorous caviomorph burrowing rodent Octodon degus (mb nearly 200 g), an inhabitant of semi-arid and mediterranean communities of northern and central Chile. Individuals maintained during 27 wk with a diet high in dietary fiber showed significantly lower BMRs (28%) than those feeding on low fiber. Daily food intake and ingestion rates (energy and dry matter) of individuals under a high-fiber diet were significantly higher than animals maintained with a low-fiber diet. The same pattern was obtained for total feces production and rate of feces production. The total intake and rate of ingestion of proteins were not significantly different between treatments. However, a significantly higher amount of protein was excreted by the individuals exposed to a high-fiber diet. Apparent digestibility of dry matter, energy, and protein were consistently lower in individuals maintained with high fiber. However, nonsignificant differences were observed between gut contents in the two treatments (P > .58), but a significantly higher digesta turnover rate was observed in animals exposed to a high-fiber diet (P < .05). A significant correlation was found between digestibility and the basal metabolic rate of individuals (r, = 0.781, P < .01), suggesting that elevated digestibilities on high-quality diets allow increased basal rates of metabolism. We suggest that, although small mammals like degus may select sparsely distributed plants of high quality in their habitat, their capability to drop their metabolic demands may help them meet their nutritional and energy requirements when nutritional conditions in the environment deteriorat

Gut size variation among Bufo spinulosus populations along an altitudinal (and dietary) gradient

To date, digestive flexibility has been studied in dozens of vertebrate species. However, practically all of these works has ignored the importance of intraspecific physiological variability across populations inhabiting different habitats. Here, we compare the digestive tract gross morphology of three populations of the Andean toad (Bufo spinulosus), inhabiting along an altitudinal gradient and feeding on different food items. Results support a core prediction of digestive theory, i.e., intestinal length increases in parallel with the content of indigestible material in the natural diet. The present study suggest how variation in the abiotic environment associated with altitude (e.g., temperature, water availability, soil quality) can change biotic conditions (e.g., vegetation cover, prey availability), affect feeding behavior of individuals (e.g., width and composition of trophic niche), and, ultimately, individuals' digestive features (e.g., gut morphology)

Colder is better: The differential effects of thermal acclimation on life history parameters in a parasitoid fly

In this article, we assessed the effect of the rearing temperature on life history traits of the poorly known fly Phasmovora phasmophagae (Diptera: Tachinidae), a parasitoid of Agathemera crassa (Phasmatodea: Agathemeridae) in order to: i) test the effect of ambient temperature on life history traits and ii) assess the potential trade-off between reproduction and survival. Parasitoids were obtained from a population of hosts located in the Andes range of central Chile. Upon emergence from the host parasitoids were randomly allocated to three thermal treatments (15 °C, 22.5 °C and 30 °C) and several life history traits were measured. We recorded higher survival at 15 °C and 22.5 °C and a lower survival at 30 °C.We found differences for both body mass and head width among thermal treatments. In females, body mass was higher at 15 °C than at 30 °C. An effect of breeding temperature and sex was observed only for developmental time. In addition, males reared at different temperatures during the pupal stage and held as adults at 22.5 °C, exhibited no differences in longevity between treatments. A significant effect of temperature on the mass of ovaries and lipid was recorded in females. These patterns suggest a trade-off between reproduction and survival. Overall, data seem to support the “colder is better” hypothesis, because Andean parasitoid P. phasmophagae inhabiting and experimentally reared in colder environments have a higher performance in all environments.Fondecyt 1080072 / CAPES, FB 0002–201

Ontogenic development of intestinal disaccharidases in the precocial rodent Octodon degus (Octodontidae)

We studied the ontogeny of the intestinal brush border disaccharidases sucrase and lactase in the precocial rodent Octodon degus. Sucrase hydrolyze sugars from plants while lactase hydrolyzes sugars from milk. Enzyme expression varied inversely with dietary changes according to the developmental pattern. All new-born pups had high lactase and low sucrase activities. Also, a negative correlation between sucrase and lactase activity was found, supporting the economic design hypothesis for the intestinal tract. Profiles for development of sucrase expression exhibit some differences among precocial species, and in O. degus is correlated with the slower transition from milk to solid food consumption at weaning

Microhabitat selection in the sand recluse spider (Sicarius thomisoides): the effect of rock size and temperature

In spiders, temperature is considered an important environmental variable for microhabitat selection. In this study, we evaluated the effect of temperature and rock size on the presence of the sand recluse spider Sicarius thomisoides and the degree of selectivity in different locations. This species is a large spider that lives under rocks in desert and semi-desert climates and is particularly active during the summer. In Chile, these spiders can be found at both coastal and inland locations under different thermal conditions, where usually the temperatures are lower near the coast. If large-scale climatic conditions are important for this species, they may be expected to select lower rock temperatures on the coast than at inland locations. In addition, we would expect that the spiders would choose larger rocks in inland compared to coast locations, which reduce the effect of high temperatures. We found that the probability of finding individuals of this species increased according to rock temperature and rock size in the field. Our results suggest that S. thomisoides prefers larger and warmer rocks to shelter under during the day, this selectivity being similar at both coastal and inland locations. Thus, this species tends to select rocks with the same thermal and structural conditions, independent of the climatic conditions.CONICYT 2113001

Biomechanical and ecological relationships of wing morphology of eight chilean bats

ABSTRACT In this study we compared the wing morphology of eight species of bats inhabiting Chile, including two previous studied species. We correlated the results with ecological information. Aspect ratio, wing span, wing area, wing loading and the second moment of area of humerus midshaft were estimated for the molossid Mormopterus kalinowskii, the phyllostomidae Desmodus rotundus and the vespertilionids Histiotus montanus, Histiotus macrotus, Lasiurus borealis, and Lasiurus cinereus. The free-tailed bats T. brasiliensis and M.kalinowskii and D. rotundus, without uropatagyum, showed a low wing area, but whilst the molossids showed large aspect ratios, that of D. rotundus was only moderate. Desmodus rotundus showed the lowest wing span (relative to the expected one) and the largest wing loading. The second moment of area of the humerus midshaft of M. chiloensis is lower than the expected values from the allometric predictions, suggesting poorer resistance to bending and torsional forces. All other vespertilionids, showed a high second moment of area of humerus. This may be explained by the highly expensive form of locomotion, especially in species with high parasite power as a consequence of their long ears. The high I h of D. rotundus that can be explained by its high body mass which increase the torque produced by the weight and a low aspect ratio. The principal component analysis showed two orthogonal axes, the first correlated positively with the wing loading and negatively with the mass corrected wingspan and the second component with the aerodynamic efficiency parameter, AR. Four functional groups, one per quadrant, were described: (1) Desmodus rotundus, with high wing loading but low corrected wing span, was in the increased agility zone, with moderate power consumption during flight; (2) the molossids were located in the high speed flight and low total power zone, showing a high aerodynamic efficiency; (3) most of vespertilionids were in the zone of low speed but increased maneuverability, their aspect ratios and wing loading were relatively low; (4) Lasiurus cinereus was in the zone of fast speed flight and the low aspect ratio predicts an increased agility. The functional groups (2) and (3) exploit similar habitats but with different life styles, the molossids foraging in open areas at fast flight speed and the vespertilionids foraging in more wooded areas with maneuverable and slow flight. Desmodus rotundus clearly constitute a single group that may be related to flights from a far communal roost and their particular mode of locomotion. Key words: bats, biomechanics, flight. RESUMEN Comparamos la morfología alar de ocho quirópteros chilenos, incluyendo dos especies previamente estudiadas. Correlacionamos los hallazgos con la información ecológica disponible. Estimamos la razón de aspecto, envergadura, la superficie, y la carga alar del molosido Mormopterus kalinowskii, el phyllostomidae Desmodus rotundus y los vespertilionidos Histiotus montanus, Histiotus macrotus, Lasiurus borealis, and Lasiurus cinereus. Los murciélagos de cola libre, T. brasiliensis, M. kalinowskii y D. rotundus, sin uropatagio, mostraron una baja superficie alar, pero mientras los molósidos mostraron alta razón de aspecto, la de D. rotundus fue solo moderada. Desmodus rotundus mostró la menor envergadura alar, relativa a su masa, y la mayor carga alar. El segundo momento del área del húmero de M. chiloensis es menor que lo esperado a partir de las predicciones alométricas, sugiriendo una pobre resistencia a la fuerzas de flexión y a la torsión. Todos los demás vespertiliónidos mostraron un alto segundo momento del área, lo que puede ser explicado por su energéticamente costosa forma de locomoción, especialmente en especias con alta potencia parásita a consecuencia de sus largas orejas. El alto I h que mostró D. rotundus puede ser explicado por su moderada razón de aspecto y por su elevada masa corporal que incrementa el torque producido por el peso. El análisis de componentes principales mostró dos ejes, el primero asociado positivamente con la carga alar y 216 CANALS ET AL. negativamente con la envergadura alar, y el segundo con la razón de aspecto. Se pudieron reconocer cuatro grupos funcionales, uno por cada cuadrante: (1) Desmodus rotundus, con alta carga alar pero baja envergadura, ubicado en la zona de alta agilidad y vuelo rápido con consumo moderado de energía; (2) los molósidos en la zona de alta velocidad de vuelo y bajo consumo; (3) la mayoría de los vespertiliónidos en la zona de alta maniobrabilidad y baja velocidad; (4)&apos;L. cinereus, con alta velocidad y agilidad. Los grupos funcionales (2) y (3) explotan similares hábitat pero con diferentes formas de vida, los molósidos forrajeando en áreas abiertas a alta velocidad y los vespertiliónidos en áreas arboladas con vuelo maniobrable y lento. D. rotundus constituyó un grupo aparte relacionado con sus largos vuelos a sus sitios de descanso y su forma particular de locomoción. Palabras clave : quiróptetos, biomecánica, vuelo. flight are correlated with B and W L . Furthermore, the minimum drag (D min ) and the minimum power required to flight (P min ) are inversely correlated to the aspect ratio: D min = 2Mg(C r /πAR) 1/2 and P min = [0.95(Mg) 3/2 C

Consequences of sexual size dimorphism on energetics and locomotor performance of Grammostola rosea (Araneae; Teraphosidae)

Most male spiders are smaller than females; during sexual maturity, males change their behaviour, abandoning their web or nest to seek out receptive females actively, whereas females stalk prey near their web or nest and tend not to move away from it. Considering this behavioural difference to be associated with increased locomotor activity at maturity, it may be hypothesized that males will have traits that increase locomotor performance. The present study examines the kinetics and energetics of the movements of the mygalomorph spider Grammostola rosea Walckenaer, a large spider with sexual size dimorphism. It is found that males have a higher maximum aerobic speed, average speed, distance travelled and critical angle of climbing than females, indicating better performance. Males also have lower costs of transport than females. These results support the hypothesis that sexual dimorphism in wandering spiders with active males, which are characterized by smaller body size and longer legs than the larger and more static females, is associated with low transport cost, high velocity and better locomotor performance

The effect of short- and long-term fasting on digestive and metabolic flexibility in the Andean toad, Bufo spinulosus

Hibernation in ectothermic animals was historically considered as a simple cold-induced torpor state resulting from the inability to maintain a high body temperature at low ambient temperatures. During the last decades this vision changed and nowadays there is a myriad of studies showing that hibernation implies different adjustments at the genetic, molecular, biochemical and cellular levels. However, studies oriented to evaluate changes of whole organism structure and physiology still are scarce, which is particularly true for amphibians that hibernate on land. Accordingly, in the Andean toad (Bufo spinulosus), we investigated the effect of short-term fasting and hibernation on the hydrolytic activity of digestive enzymes, histology of the small intestine, gross morphology of digestive and other internal organs and standard metabolic rate. Based on the pattern of size variation, internal organs may be grouped into those that were affected by both season and feeding condition (small i