Calloselasma rhodostoma; the Malayan Pitviper

By Michael Brodt and Thomas Eimermacher

Photo by Mardi Snipes

The Agkistrodon complex is by far my favorite group of snakes to work with. There are 5 genera of snakes currently recognized within this group: Agkistrodon, Calloselasma, Deinagkistrodon, Gloydius, and Hypnale.

Calloselasma rhodostoma is found in Southeast Asia, and is a distant cousin of the North American Copperheads. Calloselasma is a monotypic genus with only one species, C. rhodostoma. These snakes have some rather unusual characteristics that visually distinguish them from their North American relatives. First, they have smooth scales. This is a feature unique to the genera Calloselasma and Azemiops; every other viper and pitviper in the world has keeled scales. Second, they are one of the few pitvipers that lay eggs rather than give live birth. Deinagkistrodon acutus, another Agkistrodon relative, is also an egg-layer.

Calloselasma is found throughout Thailand to southern Vietnam, and north to the very edge of West Malaysia. Thus, the common name “Malayan pitviper” is a bit of a misnomer, as the snake actually inhabits only a small part of Malaysia. Other suggested English names have been the “Moonlight pitviper”, and the “Marbled pitviper”. These snakes are usually found in drier types of habitat throughout the region. Females are stocky and attain a length of 1.00m, with males being smaller and skinnier. They have a variable background coloration from brown to grey with the typical Copperhead style triangular bands on the sides of the body. They also have a stripe extending from their eye to their chin, which is scalloped on the bottom.

I house all of my animals in locked cages on cypress mulch with a water dish available at all times. The snakes sit coiled and/or buried in the mulch during the day, and become active at night. At the present time, my specimens have decided to eat only live prey, although at one time they did accept frozen/thawed mice dipped in warm water. Most of the specimens in my collection exhibit a bite and hold behavior with both live and frozen/thawed prey items.

All of the adult animals I have dealt with have been relatively easy to handle with hooks, however, I do not routinely remove them from their cage. Nevertheless, I have experienced instances, in which adult specimens became agitated outside of their enclosure, and these animals can be surprisingly fast. They are also known to leap forward when striking both defensively or during a feeding response, which I can confirm from my experience with them as well. Based on this, I use very long tools to work with them inside or outside of their cage.

In my experience, breeding this species is not complicated (albeit, I have only done it once). The animals shut down for the winter, feeding sparingly from November through April. I maintained them at a temperature in the mid to upper 70s F during this time. In April, I increased the temperature to the mid to upper 80s F, started feeding them again, and began misting their cages daily with warm water. In March, I placed the female into the male's cage where she remained for a week. I then removed her for feeding and returned her to the male's enclosure after a few days. I continued this cycle for one month. While I never witnessed copulation during this period, I did observe courting behavior.

The female continued her normal eating regimen until one month before laying 16 eggs. The eggs were laid in mid-July and were removed a day later for artificial incubation. They were placed on damp vermiculite inside a deli container that was equipped with air holes. The eggs were incubated in my snake room, and I maintained the temperature of the eggs around 85F with a slight night time drop. Calloselasma eggs have a short incubation period, and the eggs started hatching after 32 days. All hatchlings had emerged within 36 hours.

I housed the babies individually in deli containers with damp cypress mulch as a substrate. (For security purposes, all deli containers were housed in a large lockable cage.) Water was available at all times. After 10 days, the babies had all shed, and I tried feeding them. I was able to get the babies to feed on live cricket frogs (Acris creitans blanchardii), baby fence lizards (Sceloporus undulatus hyacinthimus), ground skinks (Scincella lateralis), and 5-lined skinks (Eumeces fasciatus). After several feedings, the babies were slowly switched over to scented mouse pinks, and from there to un-scented mouse-pinks. None of my babies started out eating pinkies right away, regardless whether they were fresh-killed or scented. One baby was a complete non-feeder, and was subsequently assist-fed about 1.5 inches of mouse tail every seven days until live pinks were killed and consumed.

The venom of Calloselasma rhodostoma is of great medical significance, in that it is responsible for a great amount of bites throughout its distribution range, and in it being the subject of much research for use in pharmaceutical products. The venom has been studied extensively, and is mainly of hemorrhagic nature. Among other components, it contains phosphodiesterase, alkalinephosphoesterase, alkaline phosphatase, L-amino acid oxidase, arginine ester hydrolase, 5'-nucleotidase, and thrombin-like enzymes. Studies in captive specimens have determined that the intraspecific variation in the venom is inherited rather than produced by external environmental factors. Purified fractions in the venom of this species are also used to derive ancrod, which is being researched for its use in the treatment of acute ischemic stroke, and has been used in the treatment of deep vein thrombosis since 1968.

In humans, the venom of Calloselasma rhodostoma has been shown to have primarily procoagulant effects at low concentrations, in that it converts fibrinogen to fibrin, and then precipitates the fibrin out of the blood, leaving the rest of the blood incoagulable. However, at higher concentrations, the venom has shown to have anticoagulant effects with a progressively shortened coagulation process.

It is also notable that according to a study by Wuster et al (1996), venom composition seems to be determined by natural selection for different prey in different areas. This is due to inherited variation, which in turn is due to natural selection, as opposed to direct induction due to different animals being eaten by an individual.

In summary, Calloselasma make rather good captive animals that do not attain an excessive size, and have husbandry requirements that are not unlike those of their North American relatives. However, based on human bite accounts and their ability to leap while striking, I would not recommend this species for beginners. Captive propagation of this animal is uncomplicated, although getting the babies to eat can be somewhat time consuming. Even still, based on the number of captive animals I have recently seen available, I believe more and more people are working with and having success with this interesting species.

References:

Gloyd HK, Conant R: Snakes of the Agkistrodon Complex: a Monographic Review, SSAR Publications, 1990
Jonhson TR: The Amphibians and Reptiles of Missouri, Missouri Department of Conservation, 1997

Daltry JC, Ponnudurai G, Shin CK, Tan NH, Thorpe RS, Wuster W. 1996. Electrophoretic profiles and biological activities: intraspecific variation in the venom of the Malayan pit viper (Calloselasma rhodostoma). Toxicon 1996 Jan;34(1):67-79

Dempfle CE, Argiriou S, Kucher K, Muller-Peltzer H, Rubsamen K, Heene DL. 2000. Analysis of fibrin formation and proteolysis during intravenous administration of ancrod. Blood 2000 Oct 15;96(8):2793-802

Hawgood BJ. 1998. Hugh Alistair Reid OBE MD: investigation and treatment of snake bite. Toxicon 1998 Mar;36(3):431-46

Dambisya YM, Lee TL, Gopalakrishnakone P. 1994. Action of Calloselasma rhodostoma (Malayan pit viper) venom on human blood coagulation and fibrinolysis using computerized thromboelastography (CTEG). Toxicon 1994 Dec;32(12):1619-26

Daltry, J.C., W. Wuster & R.S. Thorpe (1996) Diet and snake venom evolution. Nature, 379: 537-540.