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The Oriental Rat snake Ptyas mucosa (Linnaeus) is one of the widely distributed colubrine snakes belonging to the family Colubridae, from Iran, Turkmenistan, Afghanistan, Pakistan, India (incl. Andaman Isl.), Sri Lanka, Nepal, Bangladesh, Myanmar, China (incl. Hainan and Hong Kong), Thailand, Lao PDR, Cambodia, Viet Nam, Malaysia, Singapore and Indonesia and the most common snake in its entire distribution range (Auliya 2010).

Generally, the body colour and pattern varies greatly in this species from pale yellow, olive, brown to gray or black with light to dark brown or black reticulation marks. Lips scales are separated by vertical black lines. Ventral side often has prominent dark cross-bars. In juveniles, the anterior body shows light pigmented bands or cross-bars on an overall faintly olive colored body. Juveniles in at least parts of the range show a distinct, bright green coloration (Smith 1943; Daniel 2002; Whitaker & Captain 2004; Auliya 2010).

Very noticeable two color morphs of the species; one gray-olive greenish with dark reticulation and second light gray with a yellowish tinge and dark reticulation, have been recorded in the entire distribution range (Auliya Auliya 2010) and the same was observed in Gujarat State. However, recently I came across a new color morph of the species which had orange coloration with brown reticulation. The colour morph and other details are as follows.

Coloration and Other Details:
On 7 November 2011, a snake was rescued from the newly developed urban areas surrounded with agricultural fields, in Padra Town (22°14’27”N & 73°05’06”E), Vadodara District by a local snake rescuer Mr. Pravin Maharaj. It was a meter long (73.0cm snout-vent length +27.0cm tail length) juvenile orange coloured female Indian Rat Snake Ptyas mucosa.

The body colour was orange with light yellowish and brown reticulation, the reticulation was lighter and obscured on anterior body parts than the posterior body parts, belly was light orange without prominent cross-bars, eyes were orange black (Image 1 & 2). Body scale count 19:17:14 rows; supra-labials 8, 4th and 5th touch to eye; 9 infra-labials; 3 loreal, 1 sub-ocular, 1 pre-, 1 supra and 2 post ocular; temporals 2+2; two pair of genials, posterior pair longer than the anterior pair; 2 anal; ventrals 201; 135 sub caudals divided.

Image 1. Dorsal view of orange color morph of the Oriental Rat Snake Ptyas mucosa from Padra village, Vadodara, Gujarat, India.

This is the first time I have ever come across such an orange colored morph in the species or read about in any available published literatures, except an image of yellow P. mucosa on web (www.inw.net). Such unusually orange colored snake is definitely a result of some anomaly in the pigmentation.

Generally, in reptiles the color and pattern is due to the presence of various types of pigments found in the skin and it’s pigment systems. The reptile skin is patterned by a combination of pigments and structural compounds. Three types of specialized skin cells or chromatophores, namely melanophores, xanthophores (including erythrophores) and iridophores contain pigments.

Melanophores produce melanin pigments. Melanin pigment is responsible for black and brown color and occasionally some yellow and red coloration. The second, xanthophores (and erythrophores) produce pteridine pigments. Pteridine pigments are predominantly red while carotenoids are predominantly yellow to orange. Xanthophores also store fat-soluble carotenoids which are obtained from the animal’s food. Xanthophores and erythrophores are distinguished primarily by color, yellow and red respectively, which is ultimately determined by the proportion of carotenoids to pteridines in each cell. The third variety of chromatophore, the iridophores, contains crystallized purines stacked on top of one another in organelles called reflecting platelets. Platelets are colorless but highly reflective and create different colors depending on how the purine crystals are stacked. Iridophores are found in the dermis and are responsible for iridescence and blue coloration in reptile skin (Bechtel 1995). The pigmentary color anomaly is rarely observed in reptiles and when it occurs it is because one or more of the pigments are absent or are present in imbalanced degree of synthesis. Thus, it expresses some novel pattern of colouration in reptiles; as complete leucistisc, or even as irido-, xanthic-, erythro- or pinto- albinism.

Image 2. The orange color morph of the Oriental Rat Snake Ptyas mucosa, belly scales without prominent cross-bars.


Here, orange colour morph in P. mucosa is probably responsible due to minimal synthesis of melanin and excessive synthesis of petridiens in pigmentery system, which reflects the orange color in the specimen. But further research is needed on histopathology and biopsies of skin tissue and ‘dopa test’, which will enlighten the current data collection on colour anomaly in the species and enrich the subject.

Image 3. The normal color morph and orange color morph of the Oriental Rat snake

ACKNOWLEDGEMENTS
I am very thankful to Pravin Maharaj (Padara) for sharing information and allowing me to examine specimen, to Kartik Upadhayay and Pritesh Patel (Vadodara) for providing photographs of the species

REFERENCES
Auliya, M. (2010). Conservation status and impact of trade on the Oriental Rat Snake Ptyas mucosa in Java, Indonesia. TRAFFIC Southeast Asia, Petaling Jaya, Selangor, Malaysia, 39pp.
Bechtel, H.B. (1995). Reptile and Amphibian Variants: Colour, Patterns and Scales. Malabar, Florida (Krieger Publ. Comp.), xvii + 206pp.
Daniel, J.C. (2002). The Book of Indian Reptiles and Amphibians, Bombay Natural History Society, Oxford Univ. Press, 238pp.
Smith, M.A. (1943). The Fauna of British India, Ceylon, and Burma, Including the whole of the Indo-Chinese Sub-region. Reptilia and Amphibia. Vol. III Serpentes. London, Taylor & Francis. xii + 583pp.
Whitaker, R. & A. Captain (2004). Snakes of India. The Field Guide. Draco Books, Chennai. xiv+479pp.

Originally produced in the Reptile Rap No. 15 | January 2013

This site has information on the following genera of Ratsnakes ... Spilotes, Spalerosophis, Ptyas, Zamenis, Elaphe, Rhinechis, Senticolis, Pseudelaphe, Pantherophis, Bogertophis, Orthriophis, Gonyosoma, Oreocryptophis, Oocatochus, Euprepiophis, Coelognathus, Archelaphe