Trimeresurus albolabris fario Jan, 1859, 2025

Malhotra, Anita, Walter, Mrinalini, Russel, Guillem Limia & Thorpe, Roger S., 2025, Integrative analysis of geographic variation and species boundaries in the white-lipped pitviper complex (Squamata: Viperidae: Crotalinae: Trimeresurus albolabris), Vertebrate Zoology 75, pp. 191-225 : 191-225

Trimeresurus albolabris fario Jan, 1859 comb. nov.

Figures 9 , 10 , 11 ; Tables 5 , 6

Trigonocephalus fario Jan, 1859: 154 (nomen nudum, Jan 1859 a)

Bothrops viridis var. fario Jan, 1859: 30 ; plate E: unnumbered figure. Type locality. “ Java ” ( Jan 1859 b).

Bothrops (Trigonocephalus) viridis var. fario – Jan (1863): 127

Neotype.

NMW 23902 : 5 (male) collected by F. Kopstein in January 1928 at 350 m elevation in Tasikmalaya , Java, Indonesia.

Referred material.

FMNH 259115 (female) and FMNH 259116 (male), collected on 6 November 2000 by B. L. Stuart at An Minh B ắc, U Minh Thư ợng National Park , U Minh Thư ợng District, Kiên Giang, Vietnam (9°35’04.0”N, 105°05’27.0”E) ; FMNH 259117 (female) collected on 9 November 2000 by B. L. Stuart at An Minh B ắc, U Minh Thư ợng National Park , U Minh Thư ợng District, Kiên Giang, Vietnam (9°36’30”N, 105°05’58”E) ; FMNH 259189 (male), collected on 22 September 2004 by B. L. Stuart in Kirirom National Park , Phnom Sruoch District, Kampong Speu Province, Cambodia (11°19’53N; 104°04’53”E; elevation 700 m) ; FMNH 263377 (female) collected on 13 July 2003 by D. Emmett and H. Namyi at the Jar site in the Areng Valley , Thma Bang District, Koh Kong Province, Cambodia (11°28’48.1”N, 103°24’12.0”E, elevation 800 m) ; FMNH 179412 collected on 28 October 1957 by E. H. Taylor in Phra Nakhon , Bangkok, Thailand (13°45′52″N, 100°29′57″E) ; CAS 111407 (female), collected on 1 January 1961 by H. A. Fehlmann along the Siemreap-Arranya highway in the vicinity of Sisophon , Battambang Province, Cambodia (ca. 13°19’N; 103°04’E) ; NMHUK 1988 : 780, 787–789 (females) collected in May 1985 by D. A. Warrell at Trang, Thailand ; MHNG 11534 (female), collected in 1929 by R. L. Bourret in Kampot, Cambodia (10°36′N, 104°10′E; elevation 25 m) ; NMW 23902 : 1–2, 4, 10 (two males, two females) collected between November 1927 and April 1928 by F. Kopstein (in Tasikmalaya , Java, Indonesia (7°18′58″S, 108°11′51″E, elevation 350 m) ; NMBA 9477 –78 (females) collected in 1927 by F. Kopstein in Tasikmalaya , Java ; LKCNHM 2.2862 (female) collected in May 1930 in Indramajoe (Indramayu), Java ; NMBA 2588 (male) collected in 1886 in Cochin China ; NHMUK 1937.2.1.27 (male) donated by M. A. Smith from Saigon (Ho Chi Minh City), Vietnam (10°46′32″N, 106°42′07″E) .

Additional material.

Eight males collected in 1998 by P. P. van Dijk and A. Malhotra among pineapple plantations on the road to Pala-U Waterfall , Hua Hin District, Prachuap Khiri Khan, Thailand (ca. 12°31’49”N, 99°32’02”E) ; one female from Surat Thani, Thailand (ca. 8°52’N; 99°21’33”E) ; one male from Trang, Thailand (near 7°32’35”N; 99°44’54”E), both collected in 1992 by A. Malhotra and R. S. Thorpe (all released after recording data) ; two roadkilled females collected in 1991 by W. Wüster and J. C. Daltry near Bang Phra , Chonburi, Thailand (ca. 13°17’40”N, 100°59’13”E) ; five males and seven females from Bangkok, Ang Thong, and Nonthaburi Provinces , Thailand in the live collection of the QSMI ; one female from the vicinity of Thung Song , Thailand in the live collection of the QSMI ; nine females and two males from the vicinity of Ho Chi Minh City, Vietnam, purchased from snake wine dealers by T.-X. Ki ểm .

Diagnosis.

Trimeresurus albolabris fario can be distinguished from T. a. albolabris by the following combination of characters (see Table 5 for values): (a higher number of ventral and subcaudal scales; a tendency to have more scales between the 4 th and 5 th supralabial scales and the subocular scale; narrower internasal scales, less keeled body and head scales, and scale reductions around the tail occurring closer to the vent in both males and females. Additionally, females have relatively longer heads and tails.

Etymology.

The subspecific epithet fario is a Latinised masculine singular noun in apposition. In the species account for Salmo Fario, Linnaeus (1758: 309) referenced entry No. 309 in the first edition of his earlier volume Fauna Suecica ( Linnaeus 1746). This is the fourth of five entries for fishes of the type “ Salmo ”, where he listed the Ichthyologia by Stephan von Schönefeld (1624) as a source for the word Forio. Schönefeld (1624: 77) provided as a source for this term the German word Fohre, a descriptive term for the common stream salmonid derived from the proto-Germanic language, meaning “ speckled ”. Thus, Linnaeus’s name forio comes from a misspelled, Latinised, proto-Germanic term. The meaning “ salmon trout ” (Lewis and Short 1879) is a much later attribution. Without any speckling on the body of T. albolabris, Jan perhaps referenced the brownish colour that specimens of this species can attain on preservation. Alternatively, the mottled red colouration frequently found on the tail of specimens of T. albolabris may have resembled the red spots on the flanks of some trout.

Suggested common name.

Southern white-lipped pitviper.

Description of neotype.

163 ventrals, 73 paired subcaudals, 11 / 10 supralabials (right / left), 13 infralabials, two postoculars, internasals in contact, no scales between the nasal scale and the fused loreal and second supralabial scale that form the anterior edge of the pit, a minimum of ten scales between the supraoculars, and 12 between their inner rear edges, 6 / 7 scales touch the subocular (not counting pre- or postoculars), including the third infralabial scale, which is the largest. There is one scale between the fourth and two scales between the fifth infralabial and the subocular scale on the right side and one scale between both the fourth and fifth infralabial scale and the subocular on the left side. The first supralabial is partially fused with the scale surrounding the nostril. Upper body scale rows, temporal scales and scales on rear upper surface of head moderately keeled. There are 21 scale rows at midbody; the scale reduction formula is shown in Table 6 :

Five palatine, 13 pterygoid, and 12 dentary teeth. SVL 49.8 cm + tail length 14.1 cm = total length 63.9 cm. Hemipenis retractor muscle inserts at subcaudal 58; hemipenis forked at about 15 % of total length (measured in situ), the majority of the forked part with calyces extending from a short distance above the fork to the tips. The basal region below the fork bare, with soft papillate processes present. Colouration in preservative (Fig. 9 ): lateral surface of head below the eye, supralabial scales, 1–2 scales above supralabials and ventral surface considerably lighter than the upper part of the head; dorsal surface of head and body similarly uniformly coloured, a light ventrolateral stripe covering c. 40 % of the first scale row of the body fades anteriorly and does not reach the head, no postocular streak present.

Variation.

See Table 5 for variation in key characters.

Colouration in life.

Based on photographs of live individuals examined, as listed above. In males from Thailand, lower part of the head below the eye and the anterior ventral surface is almost pearlescent white, becoming yellow-green towards the vent (barely so in some specimens) and on the ventral surface of the tail, except for the last third of the tail, which is mottled with dark red. Postocular stripe may or may not be present; where present often extending below the eye socket onto the scales anterior to the eye. Upper part of head and body yellow-green, with a prominent white or yellow ventrolateral stripe, often edged below with a faint or more prominent dark or reddish pigment. Dorsal surface of head a darker shade of yellow-green or olive-drab. Iris goldenrod yellow to chocolate orange. Females are similar but are yellower than males, particularly on the ventral surface (although still retaining some pearlescent white mottling among the golden yellow pigment on the ventral surface of the head), while dorsally they range from olive green to dark green. A narrow white, indistinct yellow stripe or no stripe may be present on the first dorsal scale row. Males from the Mekong Delta area tend to be darker green in colour with no postocular stripe and yellow-green to olive-drab ventral surfaces, with light blue and golden yellow patches, particularly on the underside of the head, and a yellow ventrolateral stripe.

Comparison.

Trimeresurus can be distinguished from all other Asian pitvipers by having at least partially fused first supralabial and nasal scales. Trimeresurus albolabris can be distinguished from T. purpureomaculatus and its relatives ( T. erythrurus , T. ayeyarwadyensis , T. andersoni , and T. cantori ) by having 21 scale rows at midbody and 15 scale rows just anterior to the vent compared to more than 23 and 17, respectively, and from T. insularis most obviously by the absence of a ventrolateral stripe in females, a less pronounced ventrolateral and postocular stripe in males, and more highly keeled scales in T. insularis . Both subspecies of Trimeresurus albolabris can be distinguished from T. septentrionalis and its subspecies (see Conclusion) by a lower number of ventral scales, the reduction from 21 to 19 body scale rows and from 6 to 4 caudal scale rows occurring closer to the vent, less keeled scales on body and head, and a relatively longer head in both males and females (see Table 7 for values).

Distribution and natural history.

Trimeresurus a. fario generally occupies lowland areas in the more southerly part of the distribution of T. albolabris , including the Malay Peninsula in Thailand (and possibly Myanmar, although this remains to be confirmed), the area in the vicinity of Bangkok in central Thailand, southeast Thailand, south of the Sankamphaeng Range, the area of Cambodia around the Tonle Sap and Mekong lowlands, the Mekong Delta in Vietnam, and western Java. The nominate subspecies is restricted to China (including Hainan) and the extreme northeastern part of Vietnam. Populations in Laos and central Vietnam may represent intergrades between these two subspecies of T. albolabris , while those further north and west in Thailand may intergrade with other forms. These snakes have been recorded in a range of habitats, including Melaleuca swamp forest and grassland in open pine forest ( Cambodia); secondary forest, production forest, plantations, and agricultural areas in Java ( Kurniawan et al. 2021); as well as agricultural areas that border lowland moist forest and semi-evergreen forest in southern Thailand (personal observation). Like other related species and subspecies of T. albolabris , it is largely arboreal but may frequently be found on low vegetation or on the ground. The IUCN lists Trimeresurus albolabris as a species of Least Concern ( Stuart et al. 2012).

Snakebite risk.

Trimeresurus albolabris fario is relatively common and seems to adapt well to living in anthropogenic habitats. This species caused 92 % of 267 snakebite cases in Can Tho Municipality (Mekong Delta, Vietnam) treated in hospitals in 2017 ( Thang et al. 2020). Monovalent antivenom against T. albolabris (SAV-Tri) produced by the Institute of Vaccines and Medical Biologicals ( IVAC, Pasteur Institute, Nha Trang, Khánh Hòa Province, Vietnam) was administered in 90 % of these cases with full recovery, and no deaths were recorded. Similarly, a survey of snakebite in Tien Giang Province (Mekong Delta, Vietnam) showed green pitvipers to dominate, causing 92.9 % of 708 recorded bites in 2012, while in Ho Chi Minh City they caused 50.9 % of 1808 identifiable bites in 2011–12 ( Eriksson and Nguyen 2017). In contrast, Kurniawan et al. (2021) found T. albolabris to be less frequently encountered in their 2013–19 surveys of snakes of Java than its close relative T. insularis (encounter rate 1.8 % compared to 5.5 %), even though its range extends through two of the three provinces of Java (West and Central) compared to one in T. insularis (East). Nevertheless, the remaining available habitat in this densely populated region is nested within urbanised areas and likely increases the risk of negative outcomes of encounters between people and vipers. The commonly available antivenom in Indonesia is Biosave, produced by Biofarma Pharmaceuticals (Bandung, Indonesia), a polyvalent antivenom and indicated for bites by Naja sputatrix , Bungarus fasciatus , and Calloselasma rhodostoma ( Adiwinata and Nelwan 2015) . However, Thai Green Pitviper Antivenom (GPAV) more effectively cross-neutralizes the procoagulant effect of the venom of T. insularis and T. purpureomaculatus ( Tan et al. 2017) than Biosave (between 36 and 54 times more effective). Yong et al. (2021) also demonstrated cross-reactivity across a diverse range of pitvipers belonging to the Trimeresurus complex, hence it is very likely to also be effective against bites by T. albolabris fario . Both GPAV and SAV-Tri are also unofficially available in Laos according to Patikorn et al. (2022). Very limited information on snakebite is available for Cambodia ( Williams et al. 2009), but none of the antivenoms available in 2009 were suitable for treatment of green pitviper bite.

Figures

Figure 9. Head of the male neotype of Trimeresurus albolabris fario (Jan, 1859), NMW 23903: 5. A right lateral view, B dorsal view, C ventral view. Photos by A. Malhotra.

Figure 10. Colouration of Trimeresurus albolabris fario (males), taken under anaesthesia or immediately after euthanasia. A – C Lateral, dorsal, and ventral views of the head D lateral view of midbody E ventral view of an individual from Bangkok, Thailand (field number 98.04; not euthanized) F – H lateral, dorsal, and ventral views of the head I lateral view of midbody and J general ventral view of midbody of a specimen from Prachuap Khiri Khan Province, Thailand (field number 98.14; not euthanized) K Lateral view of FMNH 259116 from U Minh Thư ợng National Park, Kiên Giang, Vietnam. Photos by A. Malhotra (A – J) and B. L. Stuart (K).

Figure 11. Colouration of Trimerusurus albolabris fario (females), taken under anaesthesia. A – C Lateral, ventral, and dorsal views of the head D lateral view of midbody E ventral view of an individual from Nonthaburi Province, Thailand (field number 98.19; not euthanized) F – H lateral, dorsal, and ventral views of the head I lateral view of midbody J general ventral view of midbody of an individual from Thung Song Province, Thailand (field number 98.02; not euthanized). Photos by A. Malhotra.