Basic and Applied Herpetology

Assessing the response of amphibians to wildfire according to forest type and bioregion affinity of species

Brahim Chergui, César Ayres, Xavier Santos — Fri, 09 Dec 2022 00:00:00 +0000

Climate and socioeconomic factors are modifying fire regimes. In this scenario, some taxa such as amphibians may be increasingly vulnerable. However, knowledge concerning how amphibian species respond to wildfires is limited and information is puzzling, with studies reporting positive, negative or neutral responses. We examined amphibian species occurrence after a 1600-ha fire in a fire-active region located in the north-western Iberian Peninsula. This area is a biogeographical crossroad where Atlantic and Mediterranean amphibian species can coexist in the same ponds. We sampled 33 water points in native (mainly oak) and non-native (eucalyptus) forests. Water points were sampled in two different periods: just after the fire to report direct mortality (resistance to fire), and two years after the fire to evidence resilience. We examined the influence of forest type and fire occurrence on the number of amphibian species detected per point (species richness). Species richness per point varied both depending on forest type (i.e. higher richness in the native forest) and fire occurrence (i.e. more species at burnt points). The occurrence of Atlantic species did not change with fire at native forest points but declined in exotic forest points affected by fire. Mediterranean species richness was higher at native than exotic points, as the number of species increased in native burnt forests, benefiting from the open spaces cleared by the fire. This study identified the negative effect of eucalyptus plantations on amphibians and showed that the response of this taxon to fire is shaped by species-specific bioregion affinity.

The shell measurements that best describe sexual dimorphism in the spur-thighed tortoise Testudo graeca from Algeria

Benelkadi Hadj Aissa, Roberto C. Rodríguez-Caro, Mansour Amroun, Eva Graciá — Wed, 01 Jun 2022 00:00:00 +0000

Due to phenotypic plasticity and sex-biased selective pressures, intraspecific variation in tortoise morphology is usually assessed by studying sexual dimorphism. However, inferences may differ based on the choice of shell size measurements for analyses. In this work, we identified linear measurements that best describe sexual dimorphism for the spur-thighed tortoise Testudo graeca whitei. We assessed 34 carapace and plastron measurements in 67 individuals (24 males, 43 females) in a population at the natural Mergueb site located on the central limit of the Algerian steppe. Twenty-two out of 34 measurements significantly showed sexual size dimorphism in ANOVA tests. When analyzing sexual shape dimorphism with ANCOVAs, nine measurements showed no shared allometry with the measurements used as covariates to correct by size. Meanwhile, 17 out of the remaining 23 measurements showed significant differences in shape. PCA analyses similarly described T. graeca’s sexual dimorphism. In general, females tend to be bigger than males, especially in central scutes what is probably linked with clutch sizes commitments. On the other hand, males are larger-sized in anterior and posterior scutes, probably as a result of courtship, male fighting and copulation. Some of the analyzed measurements are revealed as being especially adequate for further studying the geographical variation of sexual dimorphism in Testudo graeca

Influence of size, sex and age on venom yield of Bothrops leucurus (Serpentes, Viperidae) in captivity conditions

Tue, 15 Feb 2022 00:00:00 +0000

Snake venom is an expensive metabolic weapon used for digestion and defense. Detailed studies on the production of venoms are important for the manufacture of antivenoms and for the therapeutic management of snakebites. Bothrops leucurus is one of the snakes of medical importance responsible for a large number of accidents in Northeast Brazil. To establish the correlation between Bothrops leucurus venom (Blv) yield, under captive conditions, and the morphological characteristics (body mass and length), sex and age, 31 specimens were milked during one year, grouped by sex and age (juvenile, adult and long-lived), totaling 106 extractions in that period. We evaluated the electrophoretic profile (SDS-PAGE) under reducing conditions, the 50% lethal dose (LD50) and the minimum coagulant dose (DMC) of the extracted venoms. The body size was positively correlated with venom production in B. leucurus snakes. Regardless of sex and age, the venom showed no differences between liquid and solid composition or between right and left fang, however, the production of venom in females was twice the one found in males and more lethal. The clotting ability was lost as the animals aged, indicating that older snakes are not the best choice for venom pools in the production of antivenoms. These results are important for the choice of animals to antivenom production, and to understand the biological effects of snake venoms under captive conditions.

An updated dichotomous key to the snakes of Europe

Matteo Riccardo Di Nicola, Francesco Paolo Faraone, Thomas Zabbia — Mon, 06 Jun 2022 00:00:00 +0000

This work presents an updated dichotomous key to all snake species of Europe, based on morphological, morphometric and distributional characters. It gathers data from both the last dichotomous keys concerning European snake species and every following paper giving updates on taxonomic classification or the occurrence of new allochthonous species. The key includes 58 snake taxa, including 57species and one still unnamed taxon, distributed on the European territory, and photographic material for each species. The aim of this paper is to make the identification of all European snake species through a single manuscript more accessible, not only for researchers, but also for citizen science, thus enhancing data collection and assist species conservation.

Effects of depth in semi-controlled artificial incubation on egg hatching success of Crocodylus acutus (Cuvier, 1807) and hatchlings biometry

Junior T. Larreal, Enrique Quintero-Torres, Tito R. Barros — Tue, 19 Apr 2022 00:00:00 +0000

Semi-controlled artificial incubation methods of crocodile eggs use low technology devices where one or more parameters cannot be controlled, but with the advantage that they are less expensive and logistically more feasible. This study evaluated the effect of different artificial incubation depths on the hatching success of eggs of Crocodylus acutus, under semi-controlled conditions, and analyzed biometric data of the hatchlings. The crocodile nests were collected from sandbanks of the two rivers (Río Negro and Río Santa Rosa), both located at Machiques de Perijá, Zulia state, Venezuela. The results showed a significant and positive effect on hatching success when the eggs were buried at 2 cm depth, compared to those at 10 cm and 20 cm. The hatching success at 2 cm depth was 82.43%. Also, we found that the size and weight of the hatchlings, as well as the relationships between these biometric variables, depend on the place of origin of the nests. The highest hatching percentage obtained at 2 cm was probably due to the effect of optimal incubation temperatures at this depth. The isolation and controlled heating system of the incubation room would prevent extreme fluctuations in temperature, favoring greater hatching at 2 cm depth. Differences in the biometric aspects of the hatchlings could be associated with differences in the size and the physiological status of the females from both sites.

Herpetology in Spain: a current overview through doctoral theses

Gisela Marín-Capuz, Javier Menéndez-Blázquez — Tue, 28 Jun 2022 00:00:00 +0000

This study summarizes the temporal variation, the relative contribution of each university, the research topics addressed, the taxonomic groups studied and the differences in author and its advisors’ gender in the 303 PhD theses on herpetology defended in Spain and gathered in Teseo^© and Dialnet^©between 1977 and 2020. The number of theses defended per year is around 7 with an upward trend. Complutense and Autonomous University of Madrid universities hosted the highest number of theses, followed by Barcelona and Valencia universities. The most addressed topic was morphology, biometry and anatomy, followed by physiology and histology, genetics and habitat selection. The most studied herpetofauna orders were Squamata and Anura and the families most tackled were Lacertidae, followed by Ranidae and Salamandridae. The most addressed species were native to Spain and without protection status, as opposed to those that were non-native or with protection status. The study of invasive species is very poorly represented. The number of PhD theses defended by men is higher compared to those by women (1.43:1), however, both genders show an upward trend in the number of theses. The results represent an approximation of the development, trends and interests pursued by herpetological research in Spain.

The common midwife toad, Alytes obstetricans, is able to learn a simple task under an appetitive stimulus

Míriam Moreno-Orosa, Jaime Bosch — Wed, 07 Dec 2022 00:00:00 +0000

Studies of response learning of amphibians are scarce compared to other vertebrates. We conducted a simple experiment to evaluate response learning in a primitive anuran species, the common midwife toad (Alytes obstetricans) under an appetitive stimulus. We hypothesized that, despite the primitive character of the studied species, the animals would be able to rapidly associate a particular arm of a basic T-shaped experimental arena with the reward, and that the existing male parental care of the species would provide males greater cognitive abilities than females. The response obtained by 12 males and 13 females was statistically different than such expected by chance, suggesting a learning process. The sex of the animal, as well as the average time spent to select the correct choice, were key during the learning process. Contrary to expectations, females showed higher learning capacities than males, perhaps as a consequence of the elaborate mate selection process and the competition between females to access males in this group of amphibians. The obtained results indicate that a rapid learning capacity is highly conservative in the phylogeny, having evolved from early tetrapods to those existing today in reptiles, birds, and mammals.