Eutropis bibronii (Gray, 1838)

Ukuwela, Kanishka D. B., 2017, An authentic record of Eutropis bibronii (Gray, 1838) (Reptilia: Scincidae) from Sri Lanka, Zootaxa 4329 (2), pp. 175-182 : 177-179

Results

Diagnosis. The species was diagnosed from all other congeners in Sri Lanka by the presence of the characteristic transparent lower eyelid (all the other Sri Lankan Eutropis spp. bear scaly lower eyelids). It was distinguished from congeners in South Asia by the presence of the following combination of characteristics: a transparent lower eyelid, 28 midbody scale rows, 5 keels on dorsal scales and two dark paravertebral stripes separated by a pale median stripe on the back ( FIGURE 2 , A, B, C).

Description of the specimens. All three specimens examined had a single postnasal, two long pre-auricular lobules on each tympanum, slightly separated prefrontals, 2 preoculars, 1 supranasal, 2 loreals, 1 interparietal, 4 supraoculars, 5 supraciliaries, 2 post oculars, 3 anterior temporals, 3 posterior temporals, 6 supralabials, 6 infralabials, large mental, 3 pairs of chin shields and smooth ventral scales. The specimen from Chundikulam National Park had two pairs of large nuchals and 36 paravertebral scale rows while the museum specimens were damaged making it difficult to examine these two characters. Number of sub-digital lamellae under fourth toe ranged between 17-18, ( FIGURE 2 , D) and the number of ventral scales ranged between 32-36 in the three specimens. Frontal is elongated and broader at the anterior end and mental is large and broad. Dorsal scales are broad and bears five strong keels ( FIGURE 3 ), ventral scales are smooth, however towards the groin and cloaca, scales are lightly keeled bearing two keels in each. Scales on the hands and feet are broad, smooth and devoid of any keels. The snout-vent length ranged from 40.9 to 50.3 mm. Rest of the morphological and meristic characters were identical with the characteristics described for the species by Amarasinghe et al., (2016b).

The color of the specimen from Chundikulam National Park is dorsally light brownish with two dark paravertebral stripes separated by a pale median stripe on the back ( FIGURE 2 , A). The dorsal color was similar to the coastal sandy habitat it is found in and may help in camouflage ( FIGURE 1 ). The paravertebral stripes start from the middle of the supraocular scale row and run up to the neck area where they begin to fade and break into a dotted line ( FIGURE 1 & 2 , A). A dark dorso-lateral line starts behind the eye and extends up to the base of the tail after which it fades into brown towards the posterior ( FIGURE 1 ). The lateral sides and the venter are whitish. An orange colored line, approximately one scale thick runs from the lateral side of the neck to the base of the thigh separately from the dark dorso-lateral line ( FIGURE 1 ). Hands and feet are brown. Color was heavily faded to a brownish olive color with faint paravertebral stripes on the neck in the two museum specimens.

Locality and Habitat. The newly collected specimen was observed on May 21, 2017 around 1530 hours in the southern region of the Chundikulam National Park (N 9 ° 29’44.2, E 80 ° 34’11.2, Elevation: 5.5 m above mean sea level) in Jaffna district, Northern province of Sri Lanka ( FIGURE 4 ). It was observed in a sandy area near the sea approximately 100 m from the coast. The area has scattered palmyra palms ( Borassus flabellifer ) with dry palmyra leaves on the ground with a few grasses ( FIGURE 5 ). The specimen was agile, and burrowed into loose sea sand on approach. Three more skinks similar to the coloration of E. bibronii were also observed in this habitat. However, they were quick and escaped capture.

One of the two museum specimens had been collected from Thabbowa-Nikaweratiya and the other had been collected from ‘Challani’ on the 7th of August, 1940. However, it should be noted that Tabbowa and Nikaweratiya are two different locations that are situated 40 km apart in the North Western province of Sri Lanka. The exact position of ‘Challani’ in Sri Lanka is not known.

Discussion

Our new specimen and the museum specimens reported here reconfirms the presence of E. bibronii in Sri Lanka. Comparison of meristic and mensural characteristics of the E. bibronii specimens from Sri Lanka with other specimens of E. bibronii from India and E. beddomei from India and Sri Lanka ( TABLE 1) further supports our observation. The new and previous record suggests that the species seems to be either rare or restricted to dry sandy coastal regions of the northern areas in Sri Lanka. These areas were inaccessible for researchers for nearly thirty years due to the civil war and hence it could be the reason that it was not observed in Sri Lanka for a long time. However, a recent study in the Jaffna Peninsula failed to locate this species from the region ( Abyerami & Sivashanthini, 2006). The previous record from Jaffna reported by Somaweera & Somaweera (2009) actually refers to Chundikulam, which was initially reported by Deraniyagala (1953) (R. Somaweera pers. comm.). The other records of this species from Polonnaruwa ( Deraniyagala, 1953) and Nilgala ( Karunarathna & Amarasinghe, 2011) are not supported by photographs or voucher specimens. However, this species has been recorded from inland regions in India ( Chandramouli et al., 2012; Karthik, 2017) and hence the inland records from Sri Lanka cannot be disregarded. Eutropis bibronii is categorized as a least concern species in the IUCN Red List of threatened species (de Silva et al., 2013). However, it is listed as ‘Endangered’ in the National Red List of Sri Lanka ( Wickramasinghe, 2012) and the IUCN Red list of Sri Lanka (IUCN Sri Lanka & MOE, 2007) due to its small extent of occurrence (<100 km 2) and area of occupancy (<10 km 2) in Sri Lanka.

* Source: Amarasinghe et al., 2016b

The morphological characters and general coloration of the specimens reported here are largely in agreement with that for the previously reported specimens from India ( Amarasinghe et al., 2016b). However, the Sri Lankan specimens had comparatively lower number of paravertebral scale rows (versus 37–41) and a lower number (32– 36) of ventral scales (versus 46–52) for the species ( TABLE 1) ( Amarasinghe et al., 2016b). A larger number of specimens from Sri Lanka need to be examined to see whether these morphological differences between the Sri Lankan and Indian populations of E. bibronii are consistent or simply an effect of sexual dimorphism. It would also be beneficial to examine for any genetic divergence between Sri Lankan and Indian populations of E. bibronii because the two populations have been isolated for at least 10, 0 0 0 years since the last glacial maximum which submerged the land-bridges that once connected the two landmasses ( Senanayake, 1994).

As recently highlighted for other species of reptiles (e.g. Amarasinghe et al., 2016a; Ukuwela et al., 2017), our discovery of this rare species of skink from Sri Lanka further emphasizes the importance of systematic surveys of vertebrate groups in Sri Lanka. Future studies aided with genetics could add a new dimension to skink studies in Sri Lanka.

Figures

FIGURE 1. Eutropis bibronii specimen (NMSL 2017.13.01 NH) recorded from Chundikulam National Park, Sri Lanka.

FIGURE 2. Diagnostic features of Eutropis bibronii specimen NMSL 2017.13.01 NH, A: dorsal aspect of the head, B: lateral aspect of the head showing the transparent lower eye-lid, C: ventral aspect of head, D: ventral aspect of the right foot showing sub-digital lamellae.

FIGURE 3. Close-up of the dorsal body scales of Eutropis bibronii specimen NMSL 2017.13.01 NH, showing five keels on each scale.

FIGURE 4. The present collection locality of Eutropis bibronii (denoted by a red filled triangle) and the approximate locations of all the previous records of E. bibronii in Sri Lanka (denoted by filled circles). Elevation is given in meters above mean sea level.

FIGURE 5. Sandy seashore habitat in Chundikulam National Park where Eutropis bibronii was observed in the present study.