Life-history and behavioural adaptations to xeric environments in fossorial amphibians

Amphibians are particularly sensitive to environmental water availability due to their particularities in physiology, mainly related to permeable tegument and ectothermy, to their water-dependent reproduction, and their reduced mobility compared to other vertebrates. However, amongst anurans, some fossorial species have adapted to xeric environments, either extremely dry or drastically seasonal and unpredictable in precipitation distribution. The present study aims at advancing the understanding of the complexity of life-history adaptations and behavioural strategies that allow fossorial anurans to survive in such demanding environments, through each particular stage in the life-cycle of the study organism (larvae, juveniles, adults, and finally reproduction and egg-laying). To test the research predictions, a seasonally dry tropical forest located in the Pacific Ecuador, Arenillas Ecological Reserve, was chosen as the study site. The climate at this location is characterized by severe seasonality in terms of precipitation regime, but with a minimal variation in temperature throughout the year. The project is focused on the Pacific horned frog Ceratophrys stolzmanni, the only fossorial anuran present at the study site. The effects of water limitations were evident in the species starting with the first and most sensitive life-stage, the aquatic tadpoles. The larvae responded to both tested types of cues related to the danger of pond desiccation: an increase in tadpole density as well as a decrease in water level, by rapidly modifying their development and growth in response to the environmental conditions. When not experiencing water limitations, tadpoles were able to capitalize on favourable aquatic conditions by intensifying their growth rates, delaying their transition to terrestrial habitat and metamorphosing at large size. The size at metamorphosis was a particularly important parameter for the fitness of individuals, since the detrimental conditions experienced during larval development were carried-over to the juvenile stage, and froglets metamorphosing at a small size experienced higher mortality and achieved lesser performance in food acquiring and predator avoidance traits. The activity of the horned frogs was strongly related to the precipitation pattern, individuals coming out of the ground mainly during or shortly after rains. This means that at the study site there are a limited number of opportunities for them to acquire food even during the short rainy season. However, the species showed intense growth rates both before and after metamorphosis, and both males and females were able to sexually mature in their first year of life. Some of the investigated behavioural strategies contribute to reduce their overall energetic expenditures: low individual mobility, the choice of burrows depth in accordance with substrate humidity and an abbreviated mating season. Additionally, to diversify the modalities of resource exploitation, the Pacific horned frogs employed some mechanisms that are rather unusual for most anurans. Amongst them, they exhibited a divergence in temporal niche between terrestrial life-stages, which probably reduces intraspecific interactions and allows increased access to food for the smaller juveniles. The other mechanism refers to the capacity to consume a wide variety of prey items, including vertebrates. The intense growth rates and rapid maturation probably come at a cost of increased mortality, reflected in the low longevity of individuals from the studied population. In this aspect, the permanence of the species in such an unpredictable environment suggests that mass tadpole mortality caused by pond desiccation is rather uncommon. This is due at least partially to the synchronized reproduction that takes place at the first heavy storm of the rainy season, as soon as breeding pond become available, giving the tadpoles the longest interval possible to develop. Additionally, the female investment in a relatively large number of eggs and the overall short larval duration should contribute to successful yearly recruitment. Our study enhances the understanding of this poorly-known species and of the potential risks to its long-term survival. Due to the strong influence of rainfall regime on all life-stages, the predicted changes in precipitation patterns are likely to lead to further restriction of the activity of the frogs and to reductions of recruitment or juvenile fitness. Additionally, the short reproductive lifespan of the species makes the persistence of the population vulnerable to persistent droughts of 2–3 consecutive years. The population parameters that we provide in this thesis serve as base-line information for the present welfare of the population, and can be a starting point for the detection of potential declines. This knowledge should be included in future management plans for the effective conservation of the species

What does a Pacman eat? Macrophagy and necrophagy in a generalist predator (Ceratophrys stolzmanni)

We describe for the first time the feeding ecology of the Pacific horned frog (Ceratophrys stolzmanni), as inferred through gastrointestinal tract content analysis and behavioural observations in its natural habitat. Ingested prey in adults ranged from mites and various insects to frogs and snakes. Prey items predominantly consisted of gastropods, non-formicid hymenopterans, and centipedes. We found no relationship between the size of the predator and the prey ingested, in terms of prey size, volume or number of items ingested. Additional direct observations indicate that all post-metamorphic stages are voracious, preying on vertebrates and engaging in anurophagy, cannibalism, and even necrophagy. Our study sheds light on the feeding habits of one of the least known species of horned frog

Amphibia, Anura, Bufonidae, Rhaebo ecuadorensis Mueses-Cisneros, Cisneros-Heredia & McDiarmid, 2012, and Anura, Hylidae, Phyllomedusa tarsius (Cope, 1868): range extensions and first records for Zamora-Chinchipe province, Ecuador

We report the first provincial records for Rhaebo ecuadorensis Mueses-Cisneros, Cisneros-Heredia & McDiarmid, 2012,and Phyllomedusa tarsius (Cope, 1868) in Zamora-Chinchipe, southern Ecuador. The new locations are significant because they represent the southernmost records in Ecuador as well as the westernmost limits of the ranges of these two species

Genetic delimitation of pristimantis orestes (lynch, 1979) and p. saturninoi brito et al., 2017 and description of two new terrestrial frogs from the pristimantis orestes species group (anura, strabomantidae)

peer reviewedIn the genus Pristimantis, species are often combined into taxonomic units called species groups. The taxonomy of these groups is frequently inaccurate due to the absence of genetic data from type series and repeated misidentifications generated by high morphological resemblance between taxa. Here, we focus on the P. orestes species group, providing the first genetic assessment of P. orestes sensu stricto from individuals collected from the type locality, with a reviewed diagnosis and description of advertisement calls. We find that two lineages previously named P. orestes are genetically distinct and should be separated into two different species. Based on genetic and morphological data, we name one of these species P. cajanuma sp. nov. This new species is morphologically distinct from other members of the group by having shagreen dorsal skin, evident dorsolateral folds, broader discs on toes and fingers and pale gray ventral coloration. Ad- ditionally, P. saturninoi is placed within the P. orestes species group based on genetic data from its type series. However, we find that one of its paratypes is genetically distinct and belongs to a clade containing a new species we name P. quintanai sp. nov. This new species is morphologically distinguished by lacking a tympanic membrane and vocal sacs in males, and by having expanded discs on toes and fingers, finely tuberculated dorsal skin and irregular white or cream spots in the groin and concealed surfaces of thighs. Our findings highlight the importance of providing genetic characterization and placement from the type series in taxonomic challenging groups, such as Pristimantis. We also suggest that the diversity of species within the P. orestes group will increase as more sampling is achieved in the southern Andes of Ecuador. © Veronica L. Urgiles et al

A new minute Pristimantis (Amphibia: Anura: Strabomantidae) from the Andes of southern Ecuador

We describe a new rainfrog species (Pristimantis), from the wetland complex Oña, Nabón, Saraguro and Yacuambi, in the Andes of southern Ecuador, at altitudes ranging between 3000–3400 m a.s.l. Pristimantis tiktik sp. nov. is a small frog, displaying sexual dimorphism (the males with dorsum of various shades of gray, brown, orange or green and a whitish or pinkish yellow venter; females with brownish gray or gray dorsum and a reticulated white and black venter), with SVL ranging between 19.7–20.4 mm in females (n = 3) and 16.1–18.4 mm in males (n = 6). The skin on dorsum is tuberculated, that on venter is coarsely areolate, dorsolateral folds are absent, tympanic membrane is absent but the tympanic annulus is evident, cranial crests are absent, discs on fingers just slightly expanded, heel is lacking enlarged tubercles, inner edge of tarsus is bearing a long fold, Toe V is slightly longer than Toe III and the iris coloration is bronze with fine black reticulations. The males have a large subgular vocal sac that extends onto the chest and vocal slits but lack nuptial pads. The unique advertisement call consists of long duration series of periodically repeated clicks: “tik”. Molecular analyses place the new species in the recently resurrected P. orestes group, as the sister species of the assemblage that contains P. bambu, P. mazar, P. simonbolivari and an undescribed species. © 2018 Székely et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Peer reviewe

HUNCHEST-II contributes to a shift to earlier-stage lung cancer detection: final results of a nationwide screening program

The introduction of low-dose CT (LDCT) altered the landscape of lung cancer (LC) screening and contributed to the reduction of mortality rates worldwide. Here we report the final results of HUNCHEST-II, the largest population-based LDCT screening program in Hungary, including the screening and diagnostic outcomes, and the characteristics of the LC cases.A total of 4215 high-risk individuals aged between 50 and 75 years with a smoking history of at least 25 pack-years were assigned to undergo LDCT screening. Screening outcomes were determined based on the volume, growth, and volume doubling time of pulmonary nodules or masses. The clinical stage distribution of screen-detected cancers was compared with two independent practice-based databases consisting of unscreened LC patients.The percentage of negative and indeterminate tests at baseline were 74.2% and 21.7%, respectively, whereas the prevalence of positive LDCT results was 4.1%. Overall, 76 LC patients were diagnosed throughout the screening rounds (1.8% of total participants), out of which 62 (1.5%) patients were already identified in the first screening round. The overall positive predictive value of a positive test was 58%. Most screen-detected malignancies were stage I LCs (60.7%), and only 16.4% of all cases could be classified as stage IV disease. The percentage of early-stage malignancies was significantly higher among HUNCHEST-II screen-detected individuals than among the LC patients in the National Koranyi Institute of Pulmonology's archive or the Hungarian Cancer Registry (p < 0.001).HUNCHEST-II demonstrates that LDCT screening for LC facilitates early diagnosis, thus arguing in favor of introducing systematic LC screening in Hungary.HUNCHEST-II is the so-far largest population-based low-dose CT screening program in Hungary. A positive test's overall positive predictive value was 58%, and most screen-detected malignancies were early-stage lesions. These results pave the way for expansive systematic screening in the region.• Conducted in 18 medical facilities, HUNCHEST-II is the so far largest population-based low-dose CT screening program in Hungary. • The vast majority of screen-detected malignancies were early-stage lung cancers, and the overall positive predictive value of a positive test was 58%. • HUNCHEST-II facilitates early diagnosis, thus arguing in favor of introducing systematic lung cancer screening in Hungary

Peri-operative red blood cell transfusion in neonates and infants: NEonate and Children audiT of Anaesthesia pRactice IN Europe: A prospective European multicentre observational study

BACKGROUND: Little is known about current clinical practice concerning peri-operative red blood cell transfusion in neonates and small infants. Guidelines suggest transfusions based on haemoglobin thresholds ranging from 8.5 to 12 g dl-1, distinguishing between children from birth to day 7 (week 1), from day 8 to day 14 (week 2) or from day 15 (≥week 3) onwards. OBJECTIVE: To observe peri-operative red blood cell transfusion practice according to guidelines in relation to patient outcome. DESIGN: A multicentre observational study. SETTING: The NEonate-Children sTudy of Anaesthesia pRactice IN Europe (NECTARINE) trial recruited patients up to 60 weeks' postmenstrual age undergoing anaesthesia for surgical or diagnostic procedures from 165 centres in 31 European countries between March 2016 and January 2017. PATIENTS: The data included 5609 patients undergoing 6542 procedures. Inclusion criteria was a peri-operative red blood cell transfusion. MAIN OUTCOME MEASURES: The primary endpoint was the haemoglobin level triggering a transfusion for neonates in week 1, week 2 and week 3. Secondary endpoints were transfusion volumes, 'delta haemoglobin' (preprocedure - transfusion-triggering) and 30-day and 90-day morbidity and mortality. RESULTS: Peri-operative red blood cell transfusions were recorded during 447 procedures (6.9%). The median haemoglobin levels triggering a transfusion were 9.6 [IQR 8.7 to 10.9] g dl-1 for neonates in week 1, 9.6 [7.7 to 10.4] g dl-1 in week 2 and 8.0 [7.3 to 9.0] g dl-1 in week 3. The median transfusion volume was 17.1 [11.1 to 26.4] ml kg-1 with a median delta haemoglobin of 1.8 [0.0 to 3.6] g dl-1. Thirty-day morbidity was 47.8% with an overall mortality of 11.3%. CONCLUSIONS: Results indicate lower transfusion-triggering haemoglobin thresholds in clinical practice than suggested by current guidelines. The high morbidity and mortality of this NECTARINE sub-cohort calls for investigative action and evidence-based guidelines addressing peri-operative red blood cell transfusions strategies. TRIAL REGISTRATION: ClinicalTrials.gov, identifier: NCT02350348

Pond drying cues and their effects on growth and metamorphosis in a fast developing amphibian

The hydroperiod of breeding habitats imposes a strong selection on amphibians and pond-breeding species usually exhibit a high degree of plasticity in the duration of larval period. However, the potential for phenotypic plasticity in fast developing species was investigated only in a small number of anurans, and the specific response to environmental cues such as low water versus decreasing water level, as well as the effects of such cues on particular developmental stages, are even less understood. In this context, we investigated the plastic response to pond desiccation in a neotropical species (Ceratophrys stolzmanni) by raising tadpoles in three water level treatments: constant high, constant low and decreasing. The growth rates were the highest reported for amphibian tadpoles (up to 0.3g/day) and the time to metamorphosis was short in all treatments, with the fastest developing tadpole metamorphosing in only 16 days after egg deposition. Individuals from the constant high water level treatment had a higher growth rate than those in the other two treatments, whereas decreasing and constant low water levels had similar effects on development, speeding up metamorphosis. In turn, this involved a cost as these tadpoles had a lower body size and mass at metamorphosis than the ones raised in constant high water levels. The final stages of metamorphosis, when tadpoles are the most vulnerable, were shorter in tadpoles exposed to a decreasing water level, allowing them to leave water quickly. Our experiment demonstrates that phenotypic plasticity is maintained even in environments devoid of permanent aquatic habitats. Ceratophryd tadpoles are able to shorten their developmental time when they perceive a risk of desiccation and react similarly to cues coming from the two unfavorable water conditions showing their adaptation to ephemeral and unpredictable breeding habitats

Dryness affects burrowing depth in a semi-fossorial amphibian

The fossorial life-history emerged as a response to hostile environmental conditions, such as extreme temperatures and dryness. It evolved independently in different lineages of amphibians, which are particularly vulnerable to dehydration and require a continuous level of humidity because of their permeable skin. For the first time, we test the hypothesis that amphibians are able to adapt their fossorial behaviour to substrate humidity, using the Pacific horned frogs (Ceratophrys stolzmanni) from the Ecuadorian dry forest as a model. When exposed to dry substrate, the animals burrowed much deeper than the ones in wet soil. The capacity to excavate was particularly high in this species: frogs from the dry treatment could be found at more than one-meter depth after just a few hours. Our results reveal a conditional strategy that contributes to explain the persistence of amphibians in dry environments