Black-spotted Paddy Frog – Micryletta nigromaculata – Poyarkov, Nguyen, Duong, Gorin & Yang, 2018

Science name: Micryletta nigromaculata – Poyarkov, Nguyen, Duong, Gorin & Yang, 2018

Taxonomic:  Animalia>> Chordata>> Amphibia>> Anura >> Microhylidae >> nigromaculata

Species status: Endemic ; IUCN status: EN (Endangered Species)

Description: Physical Characteristics:
Micryletta nigromaculata is a small-sized frog species. Males range from 18.5 to 23.0 mm in snout-vent length (SVL), while females are slightly larger, ranging from 24.2 to 25.9 mm in SVL. The body is moderately slender, with a head that is wider than long, and the snout is obtusely rounded. The dorsum is slightly granular, with small, flattened tubercles, and the dorsal coloration varies from reddish-brown to brown with a distinctive hourglass-shaped dark-brown pattern edged in orange. Black spots are present on the flanks, and the venter is whitish with light-gray marbling on the throat in males.

Coloration:
In life, M. nigromaculata exhibits a reddish-brown dorsum with dark-brown irregular hourglass-shaped markings. The flanks are brown with dark patches or black spots edged with white, and a large black blotch is present in the inguinal area. The ventral surface is whitish, with light-gray marbling on the throat in males.

Distribution and habitat: Altitude:
Micryletta nigromaculata is found at elevations ranging from 90 to 150 meters above sea level (asl). This species occupies limestone karst forests in northern Vietnam, where it is closely associated with primary and secondary forests near temporary water bodies.

Range:
The known range of M. nigromaculata is restricted to two provinces in northern Vietnam: Hai Phong Province (Cat Ba National Park) and Ninh Binh Province (Cuc Phuong National Park). However, it is expected that the species may inhabit adjacent limestone karst areas with similar habitats and elevations. The estimated extent of occurrence (EOO) is approximately 3,206 km², comprised of two threat-defined locations.

Habitat:
Micryletta nigromaculata primarily inhabits limestone karst forests, where it is often found between rocks and near cave entrances close to small temporary water bodies. These water sources are likely crucial for breeding. The species has not been recorded in disturbed areas, indicating its dependence on intact forest habitats.

Behaviour and ecology: Lifestyle:
Micryletta nigromaculata is a terrestrial species that is most active during the rainy season. It is found in limestone karst environments, hiding between rocks or near cave entrances, particularly close to temporary water bodies, which are crucial for breeding.

Reproduction:
Although little is known about its breeding biology, M. nigromaculata is presumed to breed in still water, following the reproductive patterns of related species. It likely develops in temporary pools rather than streams, though detailed studies are lacking.

Feeding:
The diet of M. nigromaculata is unknown, but like most small frog species, it is likely insectivorous, feeding on small invertebrates found in its habitat.

Conservation and status: IUCN Red List Category and Criteria:
Micryletta nigromaculata is listed as “Endangered” under the IUCN Red List (category B1ab(iii)) due to its restricted range, habitat fragmentation, and ongoing threats to its limestone karst habitat. The population trend is currently decreasing, and the species was last assessed in 2020.

Threats:
The primary threat to M. nigromaculata is habitat loss due to limestone quarrying and deforestation. These activities are rapidly degrading its specific karst habitat, which is crucial for its survival. Further habitat destruction could severely impact the remaining populations.

Conservation Actions:
There are no specific conservation measures in place for Micryletta nigromaculata, but the species is found in two protected areas: Cat Ba National Park and Cuc Phuong National Park. These protected areas may offer some degree of habitat protection, but further research is needed to understand the species’ population trends and ecological needs. Conservation efforts should prioritize the protection of limestone karst habitats to prevent further population declines.