Duttaphrynus brevirostris (Rao, 1937)

Bisht, Karan, Garg, Sonali, Sarmah, A. N. D. Akalabya, Sengupta, Saibal & Biju, S. D., 2021, Lost, forgotten, and overlooked: systematic reassessment of two lesser-known toad species (Anura, Bufonidae) from Peninsular India and another wide-ranging northern species, Zoosystematics and Evolution 97 (2), pp. 451-470 : 451

Duttaphrynus brevirostris (Rao, 1937)

Figs 1 , 2 , 3 , 4

Original name and description.

Bufo brevirostris Rao, 1937. Rao, C. R. N. 1937. On some new forms of Batrachia from S. India. Proceedings of the Indian Academy of Sciences. Section B 6: 387-427. Type locality. "Kempholey, Hassan District, Mysore State," Karnataka, India. Current status of specific name. Valid name, as Duttaphrynus brevirostris (Rao, 1937).

Material studied.

Topotype. An adult male, BNHS 6126 (SVL 45 mm), from Kempholey Ghat region in Sakleshpur taluk, Hassan district , Karnataka State, India , collected by S. D. Biju and Sonali Garg in June 2013. Other referred specimens. An adult male, SDBDU 2008.410 (SVL 48.6 mm), from Bhagamandala, Kodagu district , Karnataka State ; an adult male, SDBDU 2015.3075 (SVL 46 mm), from Manipal, Udupi district , Karnataka State ; and a subadult, SDBDU 4714 (SVL 25 mm), from Someshwara, Udupi district , Karnataka State .

Rediscovery and validation of taxonomic status.

This species was described based on a single specimen ("snout to vent, 27.00 mm") deposited in the Central College, Bangalore ( CCB). This original name-bearing type specimen is considered lost ( Dubois 1984; Biju 2001) and the species currently is known only from its original description. Rao (1937) enumerated several morphological character states to describe this taxon, but did not provide comparisons with other species. Our collection from a region of Kempholey Ghat in Sakleshpur taluk, that is part of the type locality ( Rao 1937), is comparable with the original description with respect to several mentioned characters such as "canthus rostralis angular," "nostril nearer to the end of the snout than to the eye," "first finger equal to the second," "parotoids elongate, moderately prominent," and "upper surface of the skin covered with small uniformly distributed tubercles; with a small row of larger warts on the median line of the back." The primary inconsistencies between Rao’s described specimen and our new collection involve snout-vent length, SVL 45 mm (vs. "27.00 mm") and weakly developed or inconspicuous cephalic ridges (vs. "crown without bony ridge"). The cephalic ridges in our new collection are relatively smooth, depressed, or less conspicuous (Figs 1A, C , 2A ) when compared to other species of the Duttaphrynus melanostictus group from Peninsular India. Hence, presence or absence of this character may be considered a matter of interpretation depending on degree of its prominence. Furthermore, the body size disparity between our collection and that of Rao (1937) also suggests that the type specimen he described could have been a subadult. We examined another subadult specimen from Someshwar ( SDBDU 4714; SVL 25 mm), previously reported along with DNA sequence data ( Van Bocxlaer et al. 2009), and found some comparable characters such as "a small row of larger warts on the median line of the back," "a network of dark lines," and "a dark temporal line extending to the sides," which can usually also be observed in subadults of Duttaphrynus melanostictus group species (S. D. B., personal observations). The Someshwar specimen is genetically identical to our Sakleshpur collection. Together, these two populations are also morphologically and genetically similar to our additional collections from other localities within the Malenadu (Malnad) and adjoining coastal regions of Karnataka (see 'Material studied’). Altogether, we consider the available morphological and molecular evidence reliable for assigning all the mentioned populations to D. brevirostris (Rao, 1937).

Since the absence of a name-bearing type has contributed towards poor knowledge and uncertainty regarding the taxonomic identity of this taxon, as evident from the absence of new records, below we provide a detailed description of a newly-collected voucher specimen from the original type locality (Kempholey Ghat region in Sakleshpur taluk, Hassan district, Karnataka State, India: BNHS 6126), which is largely consistent with what is known of the former name-bearing type ( Rao 1937). The topotype description provided below, augmented by a range of variation observed in vouchered specimens and genetic data from additional localities (Table 1; Suppl. materal 1: Tables S3, S4), validate the identity of D. brevirostris and also serve as a redescription of this poorly known species for the benefit of future taxonomic work.

Description of topotype, BNHS 6126

(measurements in mm). A medium-sized, robust adult male (SVL 45.0); head of moderate size, wider (HW 16.9) than long (HL 14.0); snout subovoid in dorsal and ventral view, not projecting, its length (SL 6.1) longer than horizontal diameter of eye (EL 5.9); loreal region obtuse with sharp canthus rostralis; distance between posterior borders of the eyes (IBE 13.9) 2.2 times the distance between the anterior borders (IFE 6.3); interorbital space 1.2 times wider (IUE 5.1) than upper eyelid width (UEW 4.1); nostril oval without lateral flap of skin, closer to tip of snout (NS 1.7) than to eye (EN 3.2); tympanum distinct (TYD 2.6), vertically oval, 44.1% of eye diameter (EL 5.9), tympanum to eye distance (TYE 0.7); pineal ocellus absent; vomerine ridge and teeth absent; tongue small, oval, entire, median lingual projection absent; parotoid glands present, oval, flat, without spines and warts, longer (PL 6.2) than wide (PW 3.4), shorter than distance between them (PD 8.7); supraorbital and postorbital ridges weakly developed.

Forelimbs short; forearm length (FAL 10.8) shorter than hand length (HAL 11.3); fingers rather thin, FLI nearly equal to FLII, FLIII longest (6.3); relative length of fingers: I=II<IV<III; tips of fingers rounded; subarticular tubercles prominent, single on fingers I, II, IV, double in finger III, oval, all present; prepollex oval, distinct; single rounded prominent palmar tubercle; numerous supernumerary tubercles irregularly set on palm.

Hind limbs relatively long and thin, thigh length (TL 17.8) shorter than shank length (SHL 18.8) and foot length (FOL 18.5); relative length of toes: I<II<V<III<IV; tips of all toes rounded, without discs; webbing between toes present, small: I1+-2II1+-3III2-3⅔IV3⅔-2V; well-developed dermal fringes present on all toes; subarticular tubercles rather distinct, oval, all present; inner metatarsal tubercle present, prominent, its length (IMT 1.6) nearly half the length of outer metatarsal tubercle (OMT 3.1); numerous supernumerary tubercles irregularly set on foot.

Skin. Dorsal and lateral surfaces of head and snout, and skin between eyes relatively smooth; anterior and posterior parts of back with flat and smooth glandular projections; flanks glandular without horny spinules or warts; dorsal surfaces of thigh, shank, and tarsus with smooth glandular warts. Ventral surfaces of throat, chest, belly, and thighs glandular.

Secondary sexual character. Male: light brown granular projections on lateral surfaces of fingers I, II, and III.

Colour in preservation. Dorsum and limbs slate grey to buff coloured; lateral surfaces of head, flank, and groin slightly lighter than dorsum; ventral surfaces (including limbs) off-white; throat with a faint light bluish-grey calling patch (Fig. 1 ). Colour in life: dorsum uniformly golden yellow with a brown tinge; limbs darker than dorsum; ventral surfaces white with a prominent bluish-yellow calling patch on throat.

Variation.

Adult size range: SVL 45-49 mm. Morphometric data from three adult males, including the described topotype, is given in Table 1. Dorsal colour varies from dark brown to golden yellow with a brown or reddish tinge; prominence of cephalic ridge varies from being inconspicuous to rather prominent; parotoid glands more prominent in life and relatively flattened in preservation; dorsal skin texture varies from having smooth glandular projections to glandular warts.

Comparisons.

Duttaphrynus brevirostris differs from other congeners that have relatively prominent cephalic ridges ( D. chandai , D. himalayanus , D. kiphirensis , D. mamitensis , D. manipurensis , D. melanostictus , D. microtympanum , D. mizoramensis , D. nagalandensis , D. parietalis , D. scaber , D. silentvalleyensis , D. stuarti , D. wokhaensis , D. crocus , D. kotagamai , D. noellerti , and D. totol ) by its relatively smooth and inconspicuous cephalic ridges (vs. prominent and often with carotenoid margins or spinules), and smooth glandular dorsal skin (vs. presence of prominent glandular warts with horny spinules). Specifically, it also differs from the Indian species by the following characters: from D. chandai , by its shorter male snout-vent length, SVL 45-49 mm (vs. longer, SVL 67-89 mm), absence of canthal, parietal, and cranial ridges (vs. present), and distinct tympanum (vs. inconspicuous externally); from D. himalayanus , D. kiphirensis , D. mamitensis , D. manipurensis , D. melanostictus , D. microtympanum , D. mizoramensis , D. nagalandensis , D. parietalis , D. scaber , D. silentvalleyensis , and D. wokhaensis , by absence of canthal, preorbital, and supratympanic ridges (vs. present), relatively flat parotoid glands (vs. prominently raised), and ventral surfaces of hand, fingers, foot, and toes with smooth tubercles (vs. raised and spinular tubercles); and from D. beddomii , D. hololius , D. peninsularis , and D. stomaticus by the presence of supraorbital and postorbital ridge (vs. absent). Duttaphrynus brevirostris specifically also differs from D. beddomii by its finger and toe tips lacking expanded discs (vs. with weakly-expanded discs), relatively reduced foot webbing, I1+-2II1+-3III2-3⅔IV3⅔-2V (vs. extensive, I1-1II1-1III1-2IV2-1V), and absence of prominently glandular warts or horny spinules on dorsum (vs. present); from D. hololius , by its robust body (vs. dorso-ventrally flattened body), absence of mid-dorsal line (vs. present), sharp canthus rostralis (vs. rounded), snout rounded in lateral view (vs. acute), and more extensive foot webbing, I1+-2II1+-3III2-3⅔IV3⅔-2V (vs. rudimentary); from D. stomaticus , by its shorter male snout-vent length, SVL 45-49 mm (vs. longer, SVL 54-69 mm), snout subovoid in dorsal view (vs. rounded), canthus rostralis sharp (vs. rounded), and relatively reduced foot webbing, I1+-2II1+-3III2-3⅔IV3⅔-2V (vs. more extensive: I1-1II1-2-III1-3IV3-1V); and from D. peninsularis , by its canthus rostralis sharp (vs. rounded), snout length longer than eye diameter, SL/EL ratio 1.2-1.3 mm (vs. nearly equal), and relatively reduced foot webbing, I1+-2II1+-3III2-3⅔IV3⅔-2V (vs. more extensive: I1+-2II1+-3-III 1½-3IV3-1½ V).

Phylogenetic relationships and genetic distances.

Duttaphrynus brevirostris is a member of the Duttaphrynus melanostictus group (Fig. 3 ), within which it is more closely related to D. melanostictus , D. cf. microtympanum ( D. “sp”, Van Bocxlaer et al. 2009), and D. parietalis (Fig. 3 ). All populations of D. brevirostris exhibit intraspecific distances of 0-0.2% in 16S. The sequence divergence for D. brevirostris from other members of the Duttaphrynus melanostictus group was as follows: 2.1-3.3% from D. melanostictus , 2.2-2.6% from D. cf. microtympanum , 2.8-3.2% from D. parietalis , 3.0-4.3% from Duttaphrynus sp. 1, and 2.4-5.6% from Duttaphrynus sp. 2 (Suppl. materal 1: Table S4).

Distribution and natural history.

Duttaphrynus brevirostris is endemic to the Western Ghats, where it currently is known only from the State of Karnataka. Here, we report this species from Hassan district (Sakleshpur taluk, encompassing the type locality Kempholey Ghat), Kodagu district (Bhagamandala), and Udupi district (Someshwara and Manipal). Furthermore, we confirm the following available DNA sequences for this species: Someshwara (FJ882786, Van Bocxlaer et al. 2009), specimen examined herein; Bajipe (AB530640) and Shirva (AB530642), specimen vouchers unavailable and reportedly released ( Hasan et al. 2014); and another sample EU071759 from an unknown locality in India (Shouche and Ghate, unpublished GenBank data). Based on available evidence, D. brevirostris is confirmed to occur in Malnad or Malenadu regions as well as coastal regions (districts of Mangalore and Udupi) of Karnataka State and, therefore, has a wider distribution than previously surmised (Fig. 4 ).

Most individuals were located during night searches (between 17:00-21:00 hours) in secondary forests or open urban areas. Calling males, usually with yellow dorsal colouration, were observed in June, away from the bodies of water. Specimens found closer to water were generally greyish-brown. A cursory tadpole description was provided along with the original description ( Rao 1937).

Figures

Figure 1. Morphological characters for topotype of Duttaphrynus brevirostris (Rao, 1937), topotype of D. peninsularis (Rao, 1920), and syntype of D. stomaticus (Luetken, 1864) in preservation. A-G. Duttaphrynus brevirostris, BNHS 6126: A. Dorsal view; B. Ventral view; C. Lateral view of head; D. Dorsal view of hand showing brown nuptial pad on fingers I, II, and III; E. Ventral view of hand; F. Ventral view of foot; G. Schematic illustration of webbing on foot. H-N. Duttaphrynus peninsularis: H. Holotype, ZSIC 19176; I-N. Topotype, SDBDU 6370: I. Dorsal view; J. Ventral view; K. Lateral view of head; L. Ventral view of hand; M. Ventral view of foot; N. Schematic illustration of webbing on foot. O-T. Duttaphrynus stomaticus, ZMUC 131137 (ex 196): O. Dorsal view; P. Ventral view; Q. Lateral view of head; R. Ventral view of hand; S. Ventral view of foot; T. Schematic illustration of webbing on foot.

Figure 2. Topotype of Duttaphrynus brevirostris (Rao, 1937), topotype of D. peninsularis (Rao, 1920), and referred specimens of D. stomaticus (Luetken, 1864) in life. A. Duttaphrynus brevirostris (BNHS 6126) from Kempholey Ghat region in Sakleshpur taluk. B. Duttaphrynus peninsularis (SDBDU 6370) from Wattakolli. C-F. Duttaphrynus stomaticus: C. SDBDU 2015.2909 from Assam; D. SDBDU 2012.2170 from Rajasthan; E. SDBDU 2012.2172 from Delhi; and F. SDBDU 2012.2268 from Bihar.

Figure 3. Phylogenetic relationships and genetic differentiation in the genus Duttaphrynus. A. Maximum Likelihood phylogenetic tree based on 5,737 bp DNA comprising nine mitochondrial gene regions and two nuclear genes, showing phylogenetic relationships between the major species-level lineages. Values above and below the branches indicate Bayesian Posterior Probabilities (BPP) and RAxML Bootstrap Support (BS), respectively; B. Maximum Likelihood barcoding tree based on 524 bp of the mitochondrial 16 S rRNA sequences. BPP and BS support values are indicated above and below the branches, respectively. Coloured vertical bars outside the terminal node labels indicate putative species delimited in the bPTP analysis; C. Median-Joining haplotype network based on 42 haplotypes recovered from 133 sequences of the 16 S gene (420 bp). Size of the coloured circles is proportional to the number of haplotypes; black circles indicate median vectors; each branch represents a single mutation step; additional mutational steps are indicated by values in parentheses; photo credits: D. crocus (Guinevere O. U. Wogan), D. olivaceus (Parham Beyhaghi), and D. dhufarensis (Todd W. Pierson).

Figure 4. Geographical distribution of Duttaphrynus brevirostris (dark grey), D. peninsularis (blue), and D. stomaticus (orange).