Hynobius tosashimizuensis Sugawara, Watabe, Yoshikawa & Nagano, 2018
|Species Description: Sugawara H, Watabe T, Yoshikawa T, Nagano M 2018 Morphological and molecular analyses of Hynobius dunni reveal a new species from Shikoku, Japan. Herpetologica 74: 159-168.|
Taxonomic Notes: This species, described in 2018, was long included in Hynobius dunni, but new data show it is not even a close relative. It occurs in the extreme SW corner of Shikoku Island, Japan, whereas H. dunni is known only from two isolated areas of eastern Kyushu Island. This species has a minute geographic range, estimated at 0.35 square km, in unprotected but privately held habitat, and must be considered Critically Endangered.
The fingers and toes of larval H. tosashimizuensis lack claws. One pair of balancers – ectodermal projections from the head – are visible during early developmental stages (Sugawara et al. 2018).
The most significant diagnostic characteristic used to distinguish H. tosashimizuensis from H. dunni is the presence or absence of black spots on their dorsum; Hynobius dunni has these spots while H. tosashimizuensis does not. Hynobius tosashimizuensis also has a shorter mean snout-vent length. Subsequently, H. tosashimizuensis also have significantly shorter measurements than H. dunni in the following average lengths: head length, tail length, trunk length, axilla-groin distance, forelimb length, hindlimb length, median tail width, and upper eyelid length. Lastly, the egg sacs of H. tosashimizuensis are coil-shaped and the egg sacs of H. dunni are crescent-shaped (Sugawara et al. 2018).
Hynobius tosashimizuensis can be distinguished from H. nebulosus as their distributions do not overlap and H. nebulosus specimens have a bright yellow stripe on the ventral edges of their tails. Hynobius nebulosus also has V-shaped vomerine teeth, whereas H. tosashimizuensis has U-shaped vomerine teeth (Sugawara et al. 2018).
In life, H. tosashimizuensis has a uniformly dark green or dark brown dorsum with no distinct black spots. The venter is slightly lighter and covered in white spots. White spots can also be found extending from the lateral side of the head all the way to the tail. They have dark brown irises. Preserved specimens will typically turn dark gray (Sugawara et al. 2018).
Larval H. tosashimizuensis have black dots on the lateral surface of their tail (Sugawara et al. 2018).
Variation among H. tosashimizuensis specimens is minimal. While most individuals do not have black spots on their dorsum, some H. tosashimizuensis specimens have indistinct black dots on their dorsal surface. Males are generally larger than females (Sugawara et al. 2018).
Distribution and Habitat
Life History, Abundance, Activity, and Special Behaviors
Their breeding season runs from January to April. Their egg sacs are coil shaped. Hynobius tosashimizuensis attaches its egg sacs to fallen branches in still ponds found at the edge of forests (Sugawara et al. 2018).
Larvae have a pair of balancers during their early development stages that they subsequently lose (Sugawara et al. 2018).
Calls and reproductive behavior have not yet been witnessed or recorded (Sugawara et al. 2018).
Trends and Threats
The species H. dunni and H. tosashimizuensis were both declared a Natural Monument of Tosashimizu City in April of 2017 under the assumption that they were both H. dunni. Local landowners have reportedly been protecting the species within the Tosashimizu city region for some time, despite the lack of habitat protection from any official local or national governments. Hynobius tosashimizuensis is not regularly consumed as food or collected for the pet trade. However, the ease of collecting specimens could potentially make them vulnerable in the future (Sugawara et al. 2018).
Relation to Humans
Possible reasons for amphibian decline
General habitat alteration and loss
It was previously thought that there were three geographically distinct populations of the same species, H. dunni, found in three different locations. These populations were given the following names based on their geographical distributions: Oita, Miyazaki, and Tosashimizu. Maximum Likelihood and Bayesian Inference methods to reconstruct the phylogenetic tree from 16S and cytochrome b genes showed that all H. dunni specimens formed a monophyletic group that was separated from all H. tosashimizuensis specimens. Furthermore, morphological analysis supported the elevation of H. tosashimizuensis as a species from H. dunni as they differ in 13 morphological characters. Hynobius tosashimizuensis also differs from the Miyazaki population in seven morphological characters. These analyses confirmed that the population found at Tosashimizu is a new species. The closest relative of H. tosashimizuensis is H. nebulosus (Sugawara et al. 2018).
The scientific name for H. tosashimizuensis is derived from the city where the species occurs: “Tosashimizu City” located within the Kochi Prefecture (Sugawara et al. 2018).
Sugawara, H., Watabe, T., Yoshikawa, T., Nagano, M. (2018). "Morphological and molecular analyses of Hynobius dunni reveal a new species from Shikoku, Japan." Herpetologica, 74(2), 159-168.
Originally submitted by: Cassandra Cardoza (2021-10-19)
Description by: Cassandra Cardoza (updated 2021-10-19)
Distribution by: Cassandra Cardoza (updated 2021-10-19)
Life history by: Cassandra Cardoza (updated 2021-10-19)
Trends and threats by: Cassandra Cardoza (updated 2021-10-19)
Relation to humans by: Cassandra Cardoza (updated 2021-10-19)
Comments by: Cassandra Cardoza (updated 2021-10-19)
Edited by: Ash Reining (2021-12-08)
Species Account Citation: AmphibiaWeb 2021 Hynobius tosashimizuensis: Tosashimizu-sanshouo <https://amphibiaweb.org/species/8847> University of California, Berkeley, CA, USA. Accessed Sep 29, 2023.
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Citation: AmphibiaWeb. 2023. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 29 Sep 2023.
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