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| Mysticellus franki
Garg & Biju, 2019
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Abstract
Anurans in Peninsular India exhibit close biogeographical links with Gondwana as well as Laurasia, often explainable by the geological history of the Indian subcontinent; its breakup from Gondwanan landmasses followed by long isolation that resulted in diversification of endemic lineages, and subsequent land connections with Asia that enabled dispersal of widespread groups. Although widely distributed, the frog subfamily Microhylinae mostly comprises of geographically restricted genera found either in Southeast and East Asia or Peninsular India and Sri Lanka. Here we report a previously unknown microhylid from the Western Ghats in Peninsular India with closest relatives found over 2,000 km away in Southeast Asia. Based on integrated evidence from mitochondrial and nuclear DNA, adult and tadpole morphology, hand musculature, male advertisement call, and geographical distance, we recognize this enigmatic frog as a distinct new species and genus endemic to the Western Ghats. The discovery of Mysticellus franki gen. et sp. nov. and its close evolutionary relationship with the Southeast Asian genus Micryletta also provide insights on the biogeography of Microhylinae. Genus-level divergences within the subfamily suggest multiple Cenozoic biotic exchange events between India and Eurasia, particularly through postulated Eocene land bridges via Southeast Asia prior to accretion of the two landmasses.
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| Fig 2: Distribution of Mysticellus franki gen. et sp. nov. and its closest generic relative Micryletta. Map prepared using QGIS 2.6.1 (http://www.qgis.org).
Image credits: Micryletta inornata (M.A.M.M. Akil), Micryletta erythropoda (J. Rowley) and Micryletta steinegeri (N.A. Poyarkov Jr.).
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| Fig 1: Diagnostic characteristics of Mysticellus franki gen. et sp. nov. (a–f) Adult in life. (a) Holotype (ZSI/WGRC/V/A/966, male) in dorsolateral view; (b) holotype (male) and paratype (ZSI/WGRC/V/A/971, female) in amplexus; (c) two ‘false-eye’ like spots on the back; (d) lateral markings; (e) dorsal view; (f) ventral view. (g–i) Tadpole in life. (g) Lateral view; (h) dorsal view; (i) ventral view. (j–k) Male advertisement call. (j) One second call segment showing pulsatile temporal structure; (k) spectrogram of one second call segment.
(l–n) Hand musculature. (l–m) Palmar view of Mysticellus franki gen. et sp. nov. (SDBDU 2015.2870, left hand). (l) Flexor teres digiti III (FT III) passing ventrally to both slips of m. transversus metacarpus 1 (TM 1); (m) two previously unreported accessory flexor muscles on digiti III and IV (labeled as “1” and “2” respectively);
(n) palmar view of Micryletta inornata (KU 328192, left hand) showing FT III dorsal to the proximal slip of TM 1 and ventral to the distal slip. Abbreviations: TM I: m. transversus metacarpus I, FT III: m. flexor teres digiti III, LBB III–IV: m. lumbricalis brevis digiti III–IV. Scale bars = 0.5 mm.
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Amphibia Linnaeus, 1758
Anura Fischer von Waldheim, 1813
Microhylidae Günther, 1858 (1843)
Microhylinae Günther, 1858 (1843)
Mysticellus gen. nov.
Type species: Mysticellus franki sp. nov.
Etymology: The genus name, Mysticellus, is a masculine noun derived from the Latin mysticus (meaning mysterious) + ellus (a diminuitive), highlighting the ability of this small frog to remain out of sight despite its occurrence in wayside areas surrounding human settlements.
Suggested common name: Mysterious Narrow-mouthed Frog.
Diagnosis: The new genus Mysticellus differs from other Microhylinae genera by the combination of following characters: small adult snout-vent size (male SVL 23.0–27.5 mm, N = 5; female SVL 27.0–28.9 mm, N = 2), slender body; snout longer than eye length, male SL 2.8–3.0 mm, 2.9 ± 0.1 mm, N = 5, female SL 3.0–3.2 mm, 3.1 ± 0.1 mm, N = 2 vs. male EL 2.4–2.6 mm, 2.5 ± 0.1 mm, N = 5; female EL 2.5–2.7 mm, 2.6 ± 0.1 mm, N = 2; absence of maxillary and vomerine teeth; finger and toe tips rounded, with small discs; presence of well-developed subarticular tubercles on all fingers and toes, rounded, alternating with additional smaller tubercles; prominent inner metatarsal tubercle and a small outer metatarsal tubercle on foot; webbing between fingers absent; rudimentary webbing between toes; lateral surfaces from tip of the snout up to the groin prominently dark blackish-brown; two prominent dark blackish-brown ‘false-eye’ like spots on either side of the groin extending just above the hind legs; a thin mid-dorsal line invariably extending from tip of the snout up to the vent; ventral surfaces of throat, belly, arms and legs dark brown with a violet tinge and various sized greyish-white blotches and speckles. This new genus can also be distinguished from other members of the subfamily by its hand musculature in having the m. flexor teres digiti III ventral to both slips of the m. transversus metacarpus 138; and the dorsal surface with two previously unreported flexor muscles on digits III and IV, one lateral to the m. lumbricalis brevis digiti III, and the other medial to the medial slip of the m. lumbricalis brevis digiti IV (Fig. 1).
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| Fig 1: Diagnostic characteristics of Mysticellus franki gen. et sp. nov. (a–f) Adult in life. (a) Holotype (ZSI/WGRC/V/A/966, male) in dorsolateral view; (b) holotype (male) and paratype (ZSI/WGRC/V/A/971, female) in amplexus; (c) two ‘false-eye’ like spots on the back; (d) lateral markings; (e) dorsal view; (f) ventral view. (g–i) Tadpole in life. (g) Lateral view; (h) dorsal view; (i) ventral view. |
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| Fig 1: Diagnostic characteristics of Mysticellus franki gen. et sp. nov. (j–k) Male advertisement call. (j) One second call segment showing pulsatile temporal structure; (k) spectrogram of one second call segment. (l–n) Hand musculature. (l–m) Palmar view of Mysticellus franki gen. et sp. nov. (SDBDU 2015.2870, left hand). (l) Flexor teres digiti III (FT III) passing ventrally to both slips of m. transversus metacarpus 1 (TM 1); (m) two previously unreported accessory flexor muscles on digiti III and IV (labeled as “1” and “2” respectively); (n) palmar view of Micryletta inornata (KU 328192, left hand) showing FT III dorsal to the proximal slip of TM 1 and ventral to the distal slip. Abbreviations: TM I: m. transversus metacarpus I, FT III: m. flexor teres digiti III, LBB III–IV: m. lumbricalis brevis digiti III–IV. Scale bars = 0.5 mm. |
Mysticellus franki sp. nov
Etymology: The species name, franki, is a Latin genitive honoring evolutionary biologist Prof Franky Bossuyt (Vrije Universiteit Brussel), recognizing his role in global amphibian research and education, and particularly for his contribution to the study of Indian amphibians.
Suggested common name: Franky’s Narrow-mouthed Frog.
Ecology and Behavior: A large number of animals usually aggregate around temporary water collection sites about two to three days after the first monsoon showers. Individuals were collected from grass adjacent to water puddles in a small wayside quarry (about 25 m2 area). The specific site was located close to a secondary forest. Breeding activities were observed only for four to five days, after which the animals disappeared and no individuals could be located despite repeated visits. Tadpoles (stage 34) were observed at the same site towards the end of July (Fig. 1g–i). Calling males exhibited a peculiar behavior of raising the hind part of their body displaying a pair of black ‘false-eye’ like spots. On some occasions, similar behavior was observed when individuals were disturbed, suggesting that the ‘false-eye’ spots may be serving a defensive role against predators (Fig. 1c).
Distribution: Mysticellus franki gen. et. sp. nov. is presently known only from the type locality in southern Western Ghats region of Kerala, Peninsular India (Fig. 2).
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| Fig 3: Maximum likelihood phylogram showing the phylogenetic position of Mysticellus franki gen. et sp. nov. in the subfamily Microhylinae. Bayesian Posterior Probabilities (BPP) and RAxML Bootstrap support values (BS) are shown above and below the branches, respectively.
Image credits: Glyphoglossus (B. Tapley), Metaphrynella (A. Figueroa), Micryletta (N.A. Poyarkov Jr.) and Phrynella (D. Bickford).
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Sonali Garg and S. D. Biju. 2019. New Microhylid Frog Genus from Peninsular India with Southeast Asian Affinity Suggests Multiple Cenozoic Biotic Exchanges Between India and Eurasia. Scientific Reports. volume 9, 1906. DOI: 10.1038/s41598-018-38133-x
Nuevo género y especie de rana endémica de los Ghats occidentales (India) nationalgeographic.com.es/naturaleza/actualidad/nuevo-genero-y-especie-rana-endemica-ghats-occidentales-india_13889 via @natgeoesp
