Gekko canaensis, Tri, Ngo Van & Gamble, Tony, 2011

Tri, Ngo Van & Gamble, Tony, 2011, Gekko canaensis sp. nov. (Squamata: Gekkonidae), a new gecko from Southern Vietnam, Zootaxa 2890, pp. 53-64 : 55-62

Gekko canaensis sp. nov.

Figures 2–3 .

Holotype. Zoological Collection of University of Natural Sciences in Hồ Chí Minh City UNS 0 538, adult male ( Figure 2 A); Cà Ná Cape, Vĩnh Tân commune, Tuy Phong district, Bình Thuận Province, Southern Vietnam, approximately 50 m elevation ( Figures 4–5; 11o 20.009”N/108o 52.224”E), collected by Ngô Vän Trí, 21 June 2010 .

Paratypes. UNS 0319 –24 were collected by N.V. T at the type locality on 26 May 2006. UNS 0539 –41 (Figures 2 B, 2C), adult males and UNS 0 542, adult female, were also collected by Ngô Vän Trí on 22 June 2010 about 2 km south of the type locality .

Etymology. The epithet is derived from the Cà Ná Cape where the type specimens were collected. We suggest the following common names: English — Cà Ná Marbled Gecko and Vietnamese — Thằn lằn đá Cà Ná.

Diagnosis. A medium sized Gekko species, maximum SVL 108.5 mm, that can be distinguished from its congeners by the following combination of characteristics: 1–4 internasals; dorsum with 10–14 longitudinal rows of enlarged, smooth dorsal tubercles; 86–93 dorsal scale rows at midbody; 30–32 ventral scale rows at midbody; 14– 18 precloacal pores in a angular continuous series in males; 14–16 lamellae on digit I of pes; 17–19 lamellae on digit IV of pes; Dorsal pattern of 5–7 whitish vertebral blotches between nape and sacrum; 6–7 pairs of short, sometimes irregular spots or white bars on flanks between limb insertions; single transverse row of enlarged smooth tubercles along the posterior portion of dorsum of each tail segment.

Description of Holotype. ( Figure 2 A), UNS 0 538, adult male. SVL 108.4 mm. Head relatively long (HeadL/ SVL= 0.27) and wide (HeadW/HeadL= 0.66), somewhat depressed (HeadD/HeadL= 0.41), distinct from neck. Loreal and interorbital regions weakly inflated, frontonasal region strongly concave. Snout elongate (SnEye/ HeadL= 0.39), blunt, longer than eye diameter (OrbD/SnEye= 0.60). Scales on snout and forehead small, granular, homogeneous; scales on snout larger than occipital scales except for scattered smooth tubercles (~ 2–3 times size of adjacent scales); 33 interorbital scale rows. Eye large (OrbD/HeadL= 0.23); pupil vertical with crenelated margins when closed and round when opened in maximum; superciliaries smooth, short, bearing several minute conical spines posteriorly. Ear opening obliquely oval, small (EarL/HeadL = 0.10); eye to ear distance longer than diameter of eye (EyeEar/OrbD = 1.20). Rostral quadrangular, wider (3.5 mm) than high (1.7 mm). Supranasals contacted by small internasal ( Figure 3 A); rostral in contact with supralabial I and supranasals; nostrils round, each surrounded by supranasal, rostral, first supralabial and two enlarged postnasals; 3–5 rows of small scales separate orbit from supralabials. Mental triangular (2.1 mm wide, deep 2.6 mm); anterior pair postmentals elongated (3.1 mm long, 1.2 mm wide), each bordered anteromedially by mental, medially in broad contact with other postmental, bordered anterolaterally by first infralabial, laterally by second postmental, posteriorly by three enlarged chin scales, but the middle largest one ( Figure 3 B); 16 supralabials on both sides, 13 sublabials on both sides; 23 scale rows on the frontal bone and 33 interorbital scales in the closest distance between two eye edges.

Body robust, relatively short (TrunkL/SVL = 0.46) with weak ventrolateral folds. Dorsal scales smooth, round, granular, juxtaposed; 93 scale rows around midbody, intermixed with enlarged, smooth tubercles (3–4 times size of adjacent scales, smaller on flanks, and smallest in occipital region) extending from occipital region to tail base; tubercles in 14 rows at midbody ( Figure 3 C). Ventral scales much larger than dorsal scales, smooth, relatively hexagonal, imbricate, gradually larger toward the posterior; 31 scale rows across venter between ventrolateral folds ( Figure 3 D); gular region with relatively homogeneous, smooth scales. Sixteen precloacal pores arranged in an angular series; scale rows extending posteriorly from pore–bearing scales to anterior of cloacal lip somewhat enlarged ( Figure 3 F); no enlarged femoral scales. Scales of palms and soles smooth, flattened, round, juxtapose without enlarged tubercles; scales on venter of fore and hind limbs with smooth, flattened, subimbricate scales, slightly enlarged at joints.

Limbs long and relatively robust (ForeaL/SVL = 0.14; CrusL/SVL = 0.16). Digits moderately dilated, all bearing curved claws except the first finger and first toe; number of broad lamellae beneath each digit (15–16–17–18– 15 manus; 15–15–19–18–17 pes); two to five narrow lamellar rows between base and digits; interdigital webbing weakly developed. Length of digits (manus; measurement in mm in parentheses): manus: IV(9.2)> III(8.0)> V(7.4)> II(6.8)> I(6.1); (pes): V(10.5)> IV(10.3)> III(10.1)> II(9.5)> I(6.3).

Original tail relatively robust and segmented ( Figure 3 G), tapering to tip; longer than snout vent length (TailL/ SVL= 1.19), two smooth postcloacal tubercles on each side; the first (anterior) being larger than the second (posterior) tubercle. Each tail segment has 3–4 transversely enlarged subcaudal scales and 10 dorsal scales rows. Tail with single transverse row of enlarged smooth tubercles along the posterior portion of dorsum of the first seven tail segments ( Figure 3 G). Scales of tail dorsum heterogeneous, rectangular to hexagonal, juxtaposed. Subcaudal region with 101 median enlarged transverse plates ( Figure 3 H).

Coloration. (In preservative) Dorsal color is gray with a series of 5–7 whitish irregular vertebral blotches between the nape and sacrum. The anterior most dorsal blotch is occasionally in contact with a light–colored ring of nuchal spots. Dorsal blotches extend along the tail, becoming ring–like although not fully encircling the tail. Regenerated tail, if present, consists of longitudinal dark stripes on a light background ( Figure 2 C). Six to seven pairs of light–colored, small, irregular bars or spots along the flanks between limb insertions. The dorsum has scattered dark brown or black and whitish flecking. Limbs are colored as dorsum with irregular white or light gray blotches and dark brown to black flecking. Multiple white or light gray, irregular blotches on the head are interspersed with dark brown or black flecks and vermiculations. Two whitish, parallel stripes extend from the rostrum to the eye on each side of the head. One stripe is often incomplete from nare to eye while the other stripe is broken and spotty and runs from the nasals to above the orbit. Light–colored nuchal loop is always broken and irregular. Venter is immaculate and white.

(In life) Dorsal color light to medium gray, with a tan or brown overtone. Limbs colored as dorsum with irregular light blotches and dark speckling. Ventral coloration is yellowish. Iris color is chestnut brown.

Variation. Variation in meristic and mensural characters among the type series are shown in Table 2. There is considerable variation among specimens in the shape and size of dorsal blotches ( Figure 2 ) with some individuals having round or oval shaped blotches ( Figure 2 A and C) while others have irregular shaped blotches with jagged edges ( Figure 2 B). Some individuals become lighter at night, a common phenomenon among some gecko species, e.g. Thecadactylus , Hemidactylus and Gekko ( Beebe 1944; Chan et al. 2006; Vitt et al. 2008; Ngo & Gamble, 2010).

Natural history. All specimens were collected at night, between 17:30 and 22:00 on the rocky outcropping after a heavy rain. Eggs, two per clutch, were found affixed to the undersides of rocks.

Comparisons. Among its Vietnamese congeners Gekko canaensis sp. nov. can be distinguished from G. s c i e n - tiadventura by the presence of dorsal tubercles and higher number of precloacal pores (14–18 vs. 5–8); from G. palmatus by the lack of broad webbing between the toes; from G. gecko by smaller adult SVL (108.5 mm maximum SVL vs. 173 mm maximum SVL – from Rösler et al. [2005]) and the rostral borders the nares in Gekko canaensis sp. nov. but not in G. gecko ; from G. badenii by lack of narrow bands on the dorsum and fewer dorsal scales at midbody (86–93 vs. 114–136); from G. grossmanni by larger adult size (89.7–108.5 mm SVL vs. 71.4– 89.4 mm SVL), higher number of internasals (1–4 vs. 0–1); higher number of precloacal pores (14–18 vs. 12–14), lower number of dorsal scales at midbody (86–93 vs. 94–115), and higher number of ventral scales at midbody (30–32 vs. 28–30); from G. russelltraini by larger adult size (89.7–108.5 mm SVL vs. 70.3–82.9 mm SVL), higher number of precloacal pores (14–18 vs. 8–11), and segmented tail; from G. canhi by larger adult size (89.7–108.5 mm SVL vs. 85.8–99.2 mm SVL), higher number of precloacal pores (14–18 vs. 5), smaller of number of ventral scale rows between lateral folds (30–32 vs. 46–50) and fewer interorbital scale rows (32–34 vs. 47–50); from G. takouensis by fewer dorsal tubercles at midbody (10–14 vs. 14–17); higher number of precloacal pores (14–18 vs. 11–14), and segmented tail.

Among non-Vietnamese members of the Gekko petricolus species group Gekko canaensis sp. nov. can be distinguished from G. petricolus by higher number of precloacal pores (14–18 vs. 9–11) and fewer interorbital scales rows (32–34 vs. 34–41); from G. lauhachindai by fewer dorsal scales at midbody (86–93 vs. 112–121), higher number of subdigital scansors under digit IV of pes (17–19 vs. 13–15), and higher number of supralabials (14–17 vs. 11–12).

Discussion. Numerous gecko species have been described from remote mountains and karst outcrops in Southeast Asia in recent years (e.g. Nguyen et al. 2006; Ngo & Bauer, 2008; Grismer et al. 2008; Grismer 2010; Ziegler & Nguyen 2010). The discovery of another new Gekko species on an isolated mountain in southern Vietnam highlights the importance of mountainous regions as centers of biodiversity in the tropics as well as the importance of continuing biological surveys in the region. The known distribution of Gekko canaensis sp. nov. is disjunct from other described members of the Gekko petricolus species group (sensu Panitvong et al. 2010, Figure 5 ). Cà Ná Cape is about 110km northeast of Tà Kóu Mountain in Binh Thuan Province, where G. takouensis occurs and approximately 60 km south of Nui Chua National Park, Ninh Thuan province, the southernmost known population of G. grossmanni ( Ngo & Ziegler, 2009) . The abundance of isolated mountains and karst throughout the region, coupled with large areas that have yet to be surveyed by herpetologists, suggests there are many gecko species waiting to be described.

Gekko canaensis sp. nov. is quite likely the “large-bodied Gekko grossmanni depicted by Kober (2004). Gekko canaensis sp. nov. is the only member of the G. petricolus group that has all of the characteristics described or illustrated by Kober (2004): large body size (260 mm total length); 16–18 precloacal pores; two cloacal spurs on either side of the base of the tail; round or oval shaped blotches on the sides of the body; 15–16 supralabaials; and lightcolored, patternless ventral scales. Kober’s (2004) paper provides a good overview of the captive husbandry and reproduction of Gekko canaensis sp. nov.

Conservation status. The presumably limited distribution of Gekko canaensis sp. nov. makes it particularly vulnerable to overharvest and habitat destruction. Cà Ná Cape is an unprotected area in Binh Thuan province and very little original forest remains in the region. Large numbers of trees have been removed to make charcoal and smaller trees have been sold to nurseries for ornamental use. Vegetation has also been reduced and damaged by cattle grazing. Granite quarrying has caused substantial damage to rock outcrops. Gekko canaensis sp. nov. has also been heavily exploited for the international pet trade. Kober’s (2004) paper confirms that commercial harvest and export for the pet trade have been occurring for most of the last decade. Talking with gecko trappers, the price of each gecko is about 5,000–7,000 VND ($0.25–0.35 USD). Gekko canaensis sp. nov. was very abundant during the first survey in 2006, but far fewer individuals were observed in the 2010 survey. It is likely that harvest for meat and the pet trade along with habitat destruction have been responsible for these declines. Gekko canaensis sp. nov. should be considered for listing in the Red Databook of Vietnam and IUCN Redlist of Threatened Species given observed declines in abundance, the long history of commercial exploitation and ongoing habitat destruction. Additional surveys and monitoring should be conducted to determine the total distribution of Gekko canaensis sp. nov. and help detect any further declines at the type locality.

Figures

FIGURE 2. Gekko canaensis sp. nov. A: Holotype UNS 0 538 in situ; B: paratype UNS 0 539 showing a light color; C: paratype UNS 0 541 shows a regenerated tail with dark stripes on its tail.

FIGURE 3. Gekko canaensis sp. nov., Holotype UNS 0 538 A: Rostral with small internasal; B: Mental with three enlarged postmental scales; C: Dorsum with 7 smooth enlarged tubercle rows on middorsum at midbody; D: Subimbricate ventral scales; E: 16 precloacal pores; F: lamellar scales beneath the toes of the right foot; G: tail dorsum segmented smooth tubercles on the first three segments; H: median enlarged subcaudal scales.

FIGURE 5. Map of Southeast Asia indicating the type localities of all described members of the Gekko petricolus species group. The type locality of Gekko canaensis sp. nov., in Ninh Thuan province is indicated by a filled circle.