Shedding Light on a Secretive Tertiary urodelean Relict: Hynobiid salamanders (Paradactylodon persicus s.l.) from Iran, Illuminated by Phylogeographic, Developmental and Transcriptomic Data.

The Hyrcanian Forests present a unique Tertiary relict ecosystem, covering the northern Elburz and Talysh Ranges (Iran, Azerbaijan), a poorly investigated, unique biodiversity hotspot with many cryptic species. Since the 1970s, two nominal species of Urodela, Hynobiidae, Batrachuperus (later: Paradactylodon) have been described: Paradactylodon persicus from northwestern and P. gorganensis from northeastern Iran. Although P. gorganensis has been involved in studies on phylogeny and development, there is little data on the phylogeography, systematics, and development of the genus throughout the Hyrcanian Forests; genome-wide resources have been entirely missing. Given the huge genome size of hynobiids, making whole genome sequencing hardly affordable, we aimed to publish the first transcriptomic resources for Paradactylodon from an embryo and a larva (9.17 Gb RNA sequences; assembled to 78,918 unigenes). We also listed 32 genes involved in vertebrate sexual development and sex determination. Photographic documentation of the development from egg sacs across several embryonal and larval stages until metamorphosis enabled, for the first time, comparison of the ontogeny with that of other hynobiids and new histological and transcriptomic insights into early gonads and timing of their differentiation. Transcriptomes from central Elburz, next-generation sequencing (NGS) libraries of archival DNA of topotypic P. persicus, and GenBank-sequences of eastern P. gorganensis allowed phylogenetic analysis with three mitochondrial genomes, supplemented by PCR-amplified mtDNA-fragments from 17 museum specimens, documenting <2% uncorrected intraspecific genetic distance. Our data suggest that these rare salamanders belong to a single species P. persicus s.l. Humankind has a great responsibility to protect this species and the unique biodiversity of the Hyrcanian Forest ecosystems.

Detection of Batrachochytrium dendrobatidis in Mexican bolitoglossine salamanders using an optimal sampling protocol.

The role of the chytrid fungus Batrachochytrium dendrobatidis (Bd), which is the causal agent of chytridiomycosis, in the declines of Central American bolitoglossine salamanders is unknown. Here we establish a swabbing protocol to maximize the detection probability of Bd in salamanders. We then used this protocol to examine captive and wild Mexican bolitoglossine salamanders of 14 different species for the presence of Bd. Of the seven body parts sampled, the pelvic region, hindlimbs, forelimbs, and the ventral side of the tail had the most Bd per surface area and thus might provide the best sampling regions of salamanders to detect Bd infections. Sixteen out of 33 (48%) of the dead captive salamanders had Bd infections and epidermal hyperkeratosis, whereas none of the 28 clinically healthy captive animals were infected. Nine out of 17 (53%) of the wild salamanders carried low zoospore loads of Bd but had no clinical signs of disease. The high prevalence of Bd in dead captive salamanders, its absence in clinically healthy living ones and its presence in wild salamanders is consistent with Bd being involved in recent bolitoglossine population declines, but further studies would be required to draw a causal link.