Life History Traits and Longevity of the Invasive Asian Common Toad Duttaphrynus melanostictus (Schneider, 1799) in Madagascar.

We analyzed the body length, age structure, and age at sexual maturity of the invasive Asian common toad Duttaphrynus melanostictus from different sites in Toamasina, east Madagascar. We used skeletochronology as a proxy for age estimation, while gonads were histologically analyzed to determine the age of sexual maturity. The analysis of pooled age data from three sites investigated in 2016 showed that both sexes were larger, although not older, than those of native populations. For the individuals from Madagascar, the males were significantly smaller and younger (mean ± SD, SVL: 71.4 ± 1.6 mm; age: 1.8 ± 0.7 years) than the females (SVL: 78.42 ± 1.9 mm; age: 2.7 ± 1.3 years), when the data were pooled, but when the data were analyzed separately for each of the three sites, similar results were obtained only for one site. The oldest recorded male and female were 3 and 6 years old, respectively. Gonadal histology showed that the males and females reach sexual maturity after the first and second years of age, respectively. Further studies are needed to understand if the larger size and faster growth rates observed in the invasive population of D. melanostictus in Madagascar are a consequence of more favorable environmental conditions with respect to the native range (e.g., the availability of larger trophic niches, a lack of competitors, and lower predatory pressure), and we suggest to extend the monitoring of these life history traits to understand how they might influence the invasion.

Characterization of the microbiome of the invasive Asian toad in Madagascar across the expansion range and comparison with a native co-occurring species.

Biological invasions are on the rise, with each invader carrying a plethora of associated microbes. These microbes play important, yet poorly understood, ecological roles that can include assisting the hosts in colonization and adaptation processes or as possible pathogens. Understanding how these communities differ in an invasion scenario may help to understand the host's resilience and adaptability. The Asian common toad, Duttaphrynus melanostictus is an invasive amphibian, which has recently established in Madagascar and is expected to pose numerous threats to the native ecosystems. We characterized the skin and gut bacterial communities of D. melanostictus in Toamasina (Eastern Madagascar), and compared them to those of a co-occurring native frog species, Ptychadena mascareniensis, at three sites where the toad arrived in different years. Microbial composition did not vary among sites, showing that D. melanostictus keeps a stable community across its expansion but significant differences were observed between these two amphibians. Moreover, D. melanostictus had richer and more diverse communities and also harboured a high percentage of total unique taxa (skin: 80%; gut: 52%). These differences may reflect the combination of multiple host-associated factors including microhabitat selection, skin features and dietary preferences.

Development and worldwide use of non-lethal, and minimal population-level impact, protocols for the isolation of amphibian chytrid fungi.

Parasitic chytrid fungi have emerged as a significant threat to amphibian species worldwide, necessitating the development of techniques to isolate these pathogens into culture for research purposes. However, early methods of isolating chytrids from their hosts relied on killing amphibians. We modified a pre-existing protocol for isolating chytrids from infected animals to use toe clips and biopsies from toe webbing rather than euthanizing hosts, and distributed the protocol to researchers as part of the BiodivERsA project RACE; here called the RML protocol. In tandem, we developed a lethal procedure for isolating chytrids from tadpole mouthparts. Reviewing a database of use a decade after their inception, we find that these methods have been applied across 5 continents, 23 countries and in 62 amphibian species. Isolation of chytrids by the non-lethal RML protocol occured in 18% of attempts with 207 fungal isolates and three species of chytrid being recovered. Isolation of chytrids from tadpoles occured in 43% of attempts with 334 fungal isolates of one species (Batrachochytrium dendrobatidis) being recovered. Together, these methods have resulted in a significant reduction and refinement of our use of threatened amphibian species and have improved our ability to work with this group of emerging pathogens.

HEMATOLOGY AND PLASMA CHEMISTRY OF THE PLOUGHSHARE TORTOISE (ASTROCHELYS YNIPHORA) IN A CAPTIVE BREEDING PROGRAM.

Blood samples from 172 captive and 40 wild, healthy, juvenile and adult, ploughshare tortoises ( Astrochelys yniphora ) were analyzed to determine hematological and biochemical reference intervals. Hematological analytes included packed cell volume (PCV), white blood cell count (WBC), and WBC differential estimates. Biochemical analysis included total protein measured by photometry (TP) and by refractometry (TPr), albumin (ALB), creatine kinase (CK), aspartate aminotransferase (AST), glutamate dehydrogenase (GLDH), bile acids (BA), calcium (Ca), phosphorus (P), urea (UREA), and uric acid (UA). The jugular vein was identified as the preferred venipuncture site as subcarapacial vein venipuncture resulted in regular hemodilution. In due consideration of small sample sizes in some of the groups studied, adult tortoises had significantly higher plasma GLDH activity and TPr, TP, ALB, BA, and UREA concentrations and significantly lower AST activity and P concentration than juveniles. Captivity had a significant influence in some reference intervals, with captive adults presenting significantly higher WBC, and estimated counts of all white cell types as well as UREA and TPr than wild counterparts. Captive juveniles also showed significantly higher estimated monocyte and lower estimated eosinophil and basophil counts. Although these differences most likely reflect local environmental or dietary differences, without representing pathology or a deviation from the normal, they question the applicability of reference values from captive animals to wild animals and vice versa. Significant sex differences were only observed for PCV and UA. The reported reference intervals may serve as benchmarks for clinical assessment and conservation of this critically endangered species.