Lankanectes pera, Senevirathne & Samarawickrama & Wijayathilaka & Manamendra-Arachchi & Bowatte & Samarawickrama & Meegaskumbura, 2018

Senevirathne, Gayani, Samarawickrama, V. A. M. P. K., Wijayathilaka, Nayana, Manamendra-Arachchi, Kelum, Bowatte, Gayan, Samarawickrama, D. R. N. S. & Meegaskumbura, Madhava, 2018, A new frog species from rapidly dwindling cloud forest streams of Sri Lanka-Lankanectes pera (Anura, Nyctibatrachidae), Zootaxa 4461 (4), pp. 519-538 : 526-530

Lankanectes pera , sp. nov.

( Figs. 2 , 3 , 4 , Appendix 2)

Type Material. Holotype: mature male, 66.0 mm SVL, DZ1858 (KNU01), Knuckles Peak, alt. 1580 m, 7.4646 °N 80.7409 °E. Collected by MM, KM-A 10th August, 2012.

Paratypes: mature female, 51.0 mm SVL, DZ1859 (KNU02), Knuckles Peak, alt. 1580 m (7˚4646’ N 80˚7409’E) collected by MM, KM-A 10th August, 2012; mature female, 42.4 mm SVL DZ1860 (HUN01), Dothalugala (Hunnasgiriya Peak), alt. 1420 m (7˚3206’N 80˚8568’E), MM, KM-A, NW 12th December, 2012; mature male, 68.7 mm SVL, DZ1307, Riverston Knuckles, alt 1330 m (7˚5233’N, 80˚7333’E), collected by MM, NW, GS 15th August, 2013; mature female, 55.8 mm SVL, DZ1290, Riverston Knuckles, alt. 1260 m (7˚5180’N, 80˚7375’E), collected by MM, NW, GS 15th August, 2013; mature female, 47.3 mm SVL, DZ1302, Riverston Knuckles, 1260 m (7˚5180’N, 80˚7375’E), collected by MM, NW, GS 15th August, 2013.

Diagnosis. Lankanectes pera sp. nov. can be distinguished from L. corrugatus by the following characters: ventrally greyish (vs white with dark brown patches in L. corrugatus ); white tubercles on throat (vs smooth throat in L. corrugatus ); edge of the upper lip uniform grey (vs white border with dark brown patches in L. corrugatus ); inner edge of toes grey (vs inner edge of I, II, III and IV toes white in L. corrugatus ); inner edge of foot grey (vs white in L. corrugatus ); flank grey (vs. flank with dark brown and white patches in L. corrugatus ).

Description (based on the holotype, DZ 1858; Figs. 2,3,4). Body stout. Head flat dorsally. Snout rounded when viewed dorsally and laterally. Canthal edges indistinct. Loreal region convex. Edges of upper lip with distinct tubercles; interorbital and internasal spaces convex. Nostrils oval; close to each other (19.3% of the width of the skull); placed dorsally on snout; edges fleshy. Tympanum absent; pineal ocellus absent. Vomerine teeth present; the vomerine teeth are tusk-like (more prominent in males), with an angle of 60° relative to body axis; less close to choanae than to each other. Tongue large; emarginated; not bearing a lingual papilla; two tubercles on posterior base of tongue. Two fang-like processes on the mandible. Internal vocal slits present, close to gape. Supratympanic fold absent. Parotid glands absent. Head wide. Cephalic ridges absent. Cephalic knob on head. Skin on head not coossified. Dorsal surface of head and body covered in numerous prominent dermal folds (corrugations) and glandular, white-tipped warts. Corrugations present also on ventral surface of head and throat. Manus robust. Forearms short, strong; fingers thin. Tips of fingers rounded, enlarged; discs absent; finger-tips not wide compared to finger width; no dermal fringe on inner or outer sides of fingers; no webbing on fingers; subarticular tubercles on fingers prominent, oval, single; prepollex distinct. Two palmar tubercles, oval, distinct, convex. Supernumerary tubercles on palm very small. Nuptial pad absent. Pes robust. Thigh and shank stout. Toes thin. Tips of toes rounded, enlarged, discs absent; tips of toes not wide compared to toe width. Toes fully webbed (see Figs 2B & 3B ). Dermal folds present on inner edge of toe I and outer edge of toe V. Subarticular tubercles on toes prominent, rounded or oval, single. Inner metatarsal tubercle long, prominent, oval. Tarsal fold present. Outer metatarsal tubercle absent. Supernumerary tubercles on foot absent. Tarsal tubercle absent. Snout between eyes and side of head with folds and fine tubercles. Anterior and posterior part of back, and upper and lower flank with dermal folds. Dorsolateral fold absent on body. Corrugations and glandular warts present on dorsal surface of legs, but are less prominent; ventral surface of legs smooth. Lateral-line system present. Dorsal parts of forelimb and thigh with corrugations. Dorsal part of shank and tarsus with corrugations and tiny tubercles. Chest, belly and ventral part of thigh smooth. A cluster of macroglands (femoral glands) on inner surface of thigh. Possess vocal sacs and nuptial pads.

Sexual dimorphism. Head of females narrower than males (see Appendix 4 for measurements); cephalic knob and vocal slits absent.

Coloration (in alcohol; Fig. 4 )—Dorsally dark brown with unequal dark patches, edges of corrugations lighter in color, some pale spots on dorsum. A pale-yellow bar with dark edges on inter-orbital area. Flank, inguinal zone, loreal region and sides of back of head light brown, edges of corrugations pale. Throat, margin of throat and vocal sacs pale brown with lighter spots. Chest, belly, ventral sides of thighs and webbing light brown.

Color in life: Dorsally chocolate brown with unequal dark-brown patches. Ridges of the numerous prominent corrugations lighter in color, with interspersed light-brown spots. A light-brown bar edged with dark brown/black colors in the interorbital area. Flank, inguinal zone, loreal region and sides of back of head light brown. Throat, margin of throat and vocal sacs white with pale brown patches. Chest, belly ventral sides white. Ventral sides of thighs light brown, with white patches. Underside of webbing light brown. Disks and tubercles of pes and manus grey-brown.

Measurements of Holotype (DZ 1858 in mm). DBE, 17.2; DFE, 9.6; ED, 7.5; EN, 4.3; ES, 9.1; FEL, 29.7; FL I, 5.8; FL II, 6.0; FL III, 7.9; FL IV, 6.9; FOL, 42.0; HL, 27.3; HW, 25.7; IML, 3.3; IN, 3.6; IO, 5.6; LAL, 13.2; MBE, 12.6; MFE, 20.4; MN, 24.1; NS, 6.9; PAL, 15.8; SVL, 66.0; TBL, 28.4; TL I, 7.3; TL II, 9.0; TL III, 12.7; TL IV, 15.9; TL V, 12; UAW, 9.8; UEW, 3.0.

Etymology. The specific epithet pera is applied as a noun in apposition. It is a reference to the University of Peradeniya, Sri Lanka, affectionately referred to as “Pera” by its alumni.

Morphometrics. Unrotated principal components analysis separates the males of the two species on PC1, but slight overlap is seen for females ( Fig. 1D ). Of the total variance, 92 % is explained by PC1, which is a size axis (although the highest factor loading was for SVL, all other variables too, had high positive values); Lankanectes pera sp. nov. is larger in size than L. corrugatus (see Appendix 4 for all material studied and measurements). Only 2.6% of the total variance is explained by PC2, which reflects mostly in FLI (length of first finger) and NS (nostril to snout distance). This axis, however, is uninformative as the two species show nearly complete overlap ( Fig. 1D , Appendix 4).

Distribution: Lankanectes pera sp. nov. is restricted to streams flowing through the montane forests on highest peaks of the Knuckles Mountain range— 1100 m asl, in Dothalugala and Bamabarella and Riverston regions.

Ecological notes and natural history. This species has so far only been observed inhabiting pristine streams flowing through closed-canopy montane forests. These streams are characterized by clear, shallow and slowflowing water, and sand and rock-strewn substrates. Males are found under rocks or rock-crevices in flowing water. Occasionally males call haltingly during daytime, but several males frequently vocalize in chorus at night, especially after light rain. Tadpoles of these frogs are large (total length of Gosner stage 35 tadpoles range between 42.00– 45.14 mm, N = 4), and occur in deeper regions (0.5 m) where decaying vegetation gathers.

Figures

FIGURE 1. (A) 16S rRNA Maximum-likelihood phylogram for 41 taxa with node support (posterior probabilities above nodes, with values>95 indicated by a *; MP bootstrap values below nodes, with values>50) showing two clearly-defined clades including L. corrugatus and L. pera (B) The uncorrected pairwise genetic distances range for 16S rRNA 3.5–3.7%; Haplotype network analysis using the full dataset with 485 bp, shows all haplotypes shared across L. corrugatus; L. pera sp. nov. is different by more than 16 mutational steps from the L. corrugatus populations. (C) The predicted distributions for L. corrugatus is 360 km 2 and L. pera sp. nov. is 14120 km 2 on the northern hills of Sri Lanka. (D) Component loadings of the first two principal component axes (PC1 vs PC2) shows clear separation of the males, but with slight overlap of females; L. pera sp. nov. indicated in red, L. corrugatus in blue (filled circles denote females and open circles denote males).

FIGURE 2. Lankanectes pera sp. nov. in life, SVL 22.40 mm: (A) Dorsolateral view; (B) Dorsal view; (C) Habitat—clear water stream habitat under montane forest canopy cover.

FIGURE 3. Illustrations of (A) Lankanectes corrugatus, ZMB4897, mature male, SVL 43.70 mm and (B) L. pera sp. nov., DZ1858, mature male, SVL 66.0 mm, anal region (top); manus (middle) and maxilla (lower).

FIGURE 4. Lankanectes pera sp. nov., SVL 68.69 mm, DZ1307 (A–D), in preservation. (A) ventral view; (B) right ventral foot; (C) ventral view of the head; (D) lateral view. Lankanectes corrugatus, SVL 55.28 mm, DZ1396 (E–H), in preservation. (A) ventral view; (B) right ventral foot; (C) ventral view of the head; (D) lateral view.