Tuesday, September 7, 2010

Snakes as Healthy Snacks and Meds

A pile of homalopsid snakes, mostly Enhydris enhydris, in a Siem Reap (Cambodia) market. These snakes were being sold for crocodile food and some females have had their bodies opened to show consumers that they are high in fat (eggs and follicles). JCM
Recently it has become clear that people in many parts of the world are consuming an increasing number of snakes. CNN World (June 26,2010) ran a story about cobra meat being harvested for "hamburgers" or perhaps what would better be described as cobrabugers in Yogyakarta, Indonesia.

Since the late 1990's the aquatic snake community at Tonle Sap, Cambodia has been used extensively by local people as a source of protein their farm-raised crocodiles and on occasion human food. Sharon Brooks and colleagues have examined the snake harvest and economics in a series of reports. The most recent one (Brooks et. al. 2010) focuses on the economic aspects of collecting snakes and the associated commercial crocodile trade Tonle Sap. An estimated 2.7 to 12.2 million snakes are consumed by farmed crocodiles annually. However, the market price for crocodiles has declined while the cost of the snakes has risen. Smaller crocodile rearing operations have closed, but the larger crocodile breeding facilities continue to operate under the assumption that crocodile prices will again increase. However, a new market for snakes may be emerging, human snack food. Data on the number of snakes eaten by humans is not available, but Brooks et al. suggest that snake snacks may become more substantial in the future.

Most of the snakes involved in the harvest are homalopsids, and of interest are the reported human health benefits of homalopsid snake oil. Richard Kunin had three species of snakes tested for omega-3 and omega-6 fatty acids: two rattlesnakes Crotalus viridis, Crotalus tigris, and the Chinese Water Snake, Enhydris chinensis. The omega-6 fatty acids have one less double bond than the omega-3's and omega-3 fatty acids are found more frequently in species adapted to cold environments. He found Enhydris chinensis oil contained 20% eicosapentaenoic acid (EPA), about three times more than rattlesnakes. The original snake oil was brought to the USA by Chinese laborers used to build the railroads in the 1840's. Apparently the Chinese recipe contained oil from the Chinese Water Snake, E. chinensis, a member of the tropical snake family Homalopsidae. However, it does have one of the most northerly distributions of the clade and of course feeds almost exclusively on fish. Apparently EPA can be absorbed through the skin, and Kunin suggests that it is a credible anti-inflammatory when topically applied to joints or inflamed skin. Note that I was unaware of this paper, when working on Homalopsid Snakes, Evolution in the Mud. Many homalopsids eat fish and it is entirely possible that more of them contain high concentrations of EPA and related compounds. Thus Kunin's data also suggests that the snake oil products produced in the late 19th century USA that were made from Crotalus would not be particularly effective in treating inflammation. Clark Stanley an American Snake Oil entrepreneur sold snake oil at the 1893  World's Columbian Exposition in Chicago, Stanley entertained crowds chopping up hundreds of rattlesnakes and processing the body fluids into his snake oil, while dressed as a cowboy. The formula for the remedy supposedly came from a Moki Pueblo (AKA Hopi) Indian medicine man. But tests of a federally seized shipment of Stanley’s Snake Oil Liniment showed it to be mostly mineral oil, with one percent fatty oil (probably beef fat), red pepper, and traces amounts of turpentine and camphor (Fowler 1997).Thus, Chinese snake oil may be a useful medicinal compound, while USA snake oil- was just snake oil. And, those Tonle Sap homalopsids, should they prove to have high concentrations of EPA, they may become the healthy protein snack of the 21st century.

Brooks, S. et al. 2010. Snake prices and crocodile appetites: aquatic wildlife supply and demand on Tonle Sap Lake, Cambodia. Biological Conservation 143:2127-2135.

Fowler, Gene, ed. 1997. Mystic Healers and Medicine Shows. Santa Fe, New Mexico: Ancient City Press.

Kunin, R. A. 1989. Snake Oil. Western Journal of Medicine 151:208

Sunday, September 5, 2010

Changing From Egg laying to Live Birth

Squamates have evolved from egg layers (the ancestral condition) to live bearers (a derived condition) tens to hundreds of times, in response to environmental changes.It is not at all unusual to find live bearing species in a clade of otherwise egg-laying species. Now Stewart et al. have documented the Australian Yellow-bellied Three-toed Skink, Saiphos equalis, has egg shell thickness that is inversely proportional to the length of time the eggs are retained in the female lizard. In an interview James Stewart, senior author at East Tennessee State University said, "By studying differences among populations that are in different stages of this process, you can begin to put together what looks like the transition from one [birth style] to the other." One of the question related to this is how do evolving species switch from delivering eggs to live babies provide nourishment to the embryos before birth. Some squamates have evolved a placenta, similar to mammals. In egg-laying species, the embryo gets nourishment from the yolk, but calcium absorbed from the porous shell is also an important nutrient source. The shells of these eggs thin dramatically so that the embryos can breathe, until live babies are born covered with only thin membranes—all that remains of the shells. However, a thinner shell has less calcium, which could cause deficiencies for the young reptiles. Stewart and colleagues decided to look for clues to the nutrient problem in the structure and chemistry of the yellow-bellied three-toed skink's uterus. He reports that, "Now we can see that the uterus secretes calcium that becomes incorporated into the embryo—it's basically the early stages of the evolution of a placenta in reptiles." Both birthing styles come with evolutionary tradeoffs: Eggs are more vulnerable to external threats, such as extreme weather and predators, but internal fetuses can be more taxing for the mother. For the skinks, females in balmier climates may opt to conserve their own bodies' resources by depositing eggs on the ground for the final week or so of development. Females in harsh mountain climates, by contrast, might find that it's more efficient to protect their young by keeping them longer inside their bodies. Overall, the results suggest the move from egg-laying to live birth in reptiles is fairly common—at least in historic terms—because it's relatively easy to make the switch, Stewart said. "We tend to think of this as a very complex transition but it's looking like it might be much simpler in some cases than we thought." Stewart. J. R. et al. 2010. Uterine and eggshell structure and histochemistry in a lizard with prolonged uterine egg retention (Lacertilia, Scincidae, Saiphos). Journal of Morphology, DOI: 10.1002/jmor.10877.

Friday, September 3, 2010

Diet of an Ancient Snake

The Amazonian Pipe Snake, Anilus scytale. JCM

The Amazonian Pipe Snake, Anilius scytale, represents a poorly known, ancient lineage of snakes. They are a basal alethinophidian and lack the ability to open their mouth widely. Previous work suggested they feed on elongated amphibians and reptiles. Maschio et al. (2010) examined 162 specimens from the Brazilian Amazonia for food items, only 12% contained prey.  Three species of amphisbaenians (Aulura anomala, Leposternon polystegumn, and Amphisbaena sp.), accounted for 81% of the diet items recovered. The remainder were snakes (Anilius scytale and Tantilla melanocephala) making up 12.5% and caecilians (Caecilia cf. gracilis) composing another 6.25%. They found a positive (but not significant) relationship between the snout-vent length of the pipe snakes and the total length of their prey, with a tendency for smaller specimens to ingest proportionately larger prey. Based upon the prey found, Anilius forages mostly on the ground and in aquatic environments at night. Prey was ingested headfirst, and is likely to minimize the risk of injury. Full citation: Maschio, G. F.,  A. LĂșcia da C. Prudente, F. da S. Rodrigues and M. S. Hoogmoed 2010. Food habits of Anilius scytale (Serpentes: Aniliidae) in the Brazilian Amazonia. Zoologia .27(2). This paper can be found on-line at: http://www.scielo.br/scielo.php?pid=S1984-46702010000200005&script=sci_arttext&tlng=en.

File Snake Phylogeny

Acrochordus javanicus. JCM

Filesnakes (Acrochordus) are unusual. They are completely aquatic, living in both fresh and salt water; they have baggy skin with rough scales containing sensory organs; and they the ability to stay underwater for long periods of time. Additionally, they have an Indo-Australian distribution. Three living species are recognized and a fourth species (A. dehmi) is known only from its fossilized vertebrae from Pakistan. One of these, the Elephant Trunk Snake (A. javanicus), is heavily hunted for its skin and meat.  Now, Sanders et al. have estimated divergence times for these snakes and looked at their phylogeny using morphology, fossils, and DNA. Their results show that A. javanicus (a South and Southeastern Asian endemic) is the sister to the Arafura Filesnake (A. arafurae) an Australasian endemic and the widespread, marine Little File Snake (A. granulatus). The divergence of the three extant species was dated at 20.3 MYA (million years ago) and A. granulatus diverged from A. arafurae 15.6 MYA. Their molecular data support the Acrochordids and Colubroidae as sister groups that separated about 62 MYA. Full citation: Sanders, K. L., Mumpuni, A. Hamidy, J. J. Head, and D. J. Gower. 2010. Phylogeny and divergence times of filesnakes (Acrochordus): inferences from morphology, fossils, and three molecular loci. Molecular Phylogenetics and Evolution 56:837-867.

Thursday, September 2, 2010

Lizard SVLs & Weights

Hatchling Anolis sagrei.

Shai Meiri of Tel Aviv University's Department of Zoology has developed a method for translating lizard body lengths to weights. Meiri's new equations calculate this valuable morphological feature to estimate the weight of a lizard species in a variety of different ecosystems.Lizards are frequently important indicator species for understanding the condition of specific ecosystems. Their body weight is a crucial index for evaluating species health, but lizards are seldom weighed, perhaps due in part to the recurring problem of spontaneous tail loss when lizards are in stress. Meir has generate equations to estimate weights from the snout–vent length.And, he used a species-level phylogenetic hypothesis to examine the ecological factors that affect the variation in weight–length relationships. Limbless and reduced limbed lizards are characterized by shallower allometric slopes, and thus long-bodied, legless species are lighter than legged lizards of comparable length. In limbed species the foraging strategy strongly influences the weights, with ambush species being bulkier at comparable lengths than active foraging species. In this study 900 species in 28 different families were used to generated a dataset of lizard weights. Full Citation: Meiri, S. 2010. Length–weight allometries in lizards. Journal of Zoology 281(3):218–226.

Burmese Python Found in Indiana

WXIN, Fox Channel 59 is reporting that an 11 foot Burmese Python was found in Wildcat Creek,in Tippecanoe County, Indiana. The snake was caught by three fishermen. September 1, 2010.

Asian Snakes Playing Dead

A Western Hognose Snake (Heterodon nasicus) displaying 
death feigning behavior. This is a North American snake, I do
not have any photos of Asian snakes death feigning.

Death feigning behavior is known in a number of different snake lineages as well as other groups of vertebrates. It is generally believed to confuse predators so that they abandon the prey. However, another hypothesis suggests that in snakes it is a behavior triggered by the stress of the encounter with the predator. Death feigning may have many different behavioral elements, or just a few. Snake species that feed on toads often have enlarged adrenal glands, and may produce more epinephrine during an encounter with a predator - this in turn may lead to a physiological reaction that result in death feigning. Gernot Vogel and Hans Han-Yuen now report death-feigning behavior in three species of Asian colubrids: Coelognathus radiatus, Macrocalamus chanardi, and Xenochrophis piscator. The authors note that death feigning is known almost exclusively from snakes in the Nearctic, and that the behavior has been reported from only a relatively few snakes in other regions of the world. My view of this is that Nearctic snakes are better studied, there are more herpetologists active in the Nearctic and agree with the authors that many more species will be found to display this behavior.

Monday, August 30, 2010

Titanoboa Exhibit at IU

BLOOMINGTON, Ind. -- Titanoboa cerrejonensis is now a special exhibit at Indiana University Bloomington. A cast of the remains of the giant boid snake can be viewed Geology Building at 1001 E. 10th St., Bloomington, Indiana, and can be visited from 8AM to 6PM Monday through Friday. Titanoboa is estimated to have been 43 feet long and weigh 2500 pounds. Paleontologist David Polly was a coauthor of the 2009 paper in Nature that reported the discovery of the world's largest known snake. The exhibit was organized by Donald Hattin (Professor Emeritus of Geological Sciences ) and is sponsored by the IU Bloomington Geological Sciences Department and the Indiana Geological Survey. The Titanoboa exhibit will be viewable until Oct. 1, 2010. Polly will give a talk entitled Hip-deep in giant snakes: Titanoboa and temperature in the Paleocene, at 4:00 p.m. on Sept. 13 (Geology Bldg. 143). The lecture is free and open to the public.

Sunday, August 29, 2010

Is the Liana Snake a Specialized Bird Nest Predator?

The Liana Snake, Pseustes poecilonotus, is a widespread neotropical snake and probably an important predator on nestling birds. Recently I observed this species emerge from its hiding place under a corrugated tin roof at the Asa Wright Nature Center (AWNC) in Trinidad in the late afternoon. The snake was very cautious and protruded its head from under the roof for about 10 minutes before slowly crawling onto the roof's surface. The AWNC is a popular destination for bird watchers and the roof was adjacent to a large veranda surrounded by bird feeders. There were several Palm Tanager nests within three meters of the snake's hiding place. The Psuestes crawled along the roof and into a small tree where I lost track of it.  Robinson et al. [2005 Ornitologia Neotropical 16:187-195] videotaped 10 instances of nest predation on Panama's Barro Colorado Island, and P. poecilonotus was responsible for eight of the predation events. In one instance the snake ate one nestling and returned to the nest the next day and ate the second bird. Tarwater [2008, The Wilson Bulletin of Ornithology 120(3):620-624] videotaped a P. poecilonotus feeding on a nestling Western Slaty Antshrike, Thamnophilus atrinucha, on Barro Colorado Island. The snake took two minutes to consume the bird. P. poecilonotus is also known to feed on lizards and mammals, but it may specialize in nestling birds when they are available.

Tiny Frogs, and a New One from Borneo

Indraneil Das and Alexander Haas have described what has been reported as the world's smallest known frog, Microhyla nepenthicola (Family Microhylidae), in a recent issue of Zootaxa. The frog inhabits Gunung Serapi mountain, located in Kubah National Park, on the island of Borneo. Adult male M. nepenthicola are 10.6 to 12.8 mm and live in the pitcher plant Nepenthes ampullaria,  which has a globe-like pitcher and grows in damp, shady forests.  Females deposit their eggs on the sides of the pitcher, and tadpoles  grow in the water that has collected inside the plant. [Full citation: Das, I. and A. Haas. 2010. New species of Microhyla  from Sarawak: Old World’s smallest frogs crawl out of miniature pitcher  plants on Borneo (Amphibia: Anura: Microhylidae). Zootaxa, 2571 37-52.]

Tiny frog species have been discovered in abundance in recent decades and media reports claiming title to the world's smallest frog have been almost as numerous. The Brazilian Gold Frog, Brachycephalus didactylus (Izecksohn, 1971)(Family Brachycephalidae) grows to a tiny 9.8 mm and appears to still hold the title to the World's smallest frog. But there are many runners-up. Hoogmoed and Lescure described Adelophryne adiastola (Family Eleutherodactylidae) from Letica, Colombia in 1984, it has a body length of 12.9 mm. In 1986, Lynch descibed Nobella (Phyllonastes) heyeri (Family Strabomantidae) from Loja province Ecuador, males were 12.9 to 14.1 mm and females were 13.1 to 15.9 in body length. In the same paper Lynch described Phrynopus bagrecito (Family Strabomantidae)  from Cuzco, Peru; this species has males that are 13.8 to 16.3 mm and  females that are 14.4 to 18.6 mm long. The small  Monte Iberia Eleuth, Eleutherodactylus iberia, Family Eleutherodactylidae), was described from Cuba in 1996 by Estrada and  Hedges; fully grown adult males are 10.5 mm and females are 9.8 mm; it seems to most closely rival Brachycephalus didactylus for the smallest body size in frogs. Nyctibatrachus minimus (Family Nyctibatrachidae) was described by  Biju et al. in 2007 from southern India; its males average 12.3  mm in body length. Lehr and Coloma (2008) described Pristimantis andinognomus (Family Strabomantidae) . They found a maximum snout–vent length of 17.9 mm  with males averaging 12.3 mm and females averaging 15.9 mm. Lehr and Catenazzi (2009) described Noblella pygmaea (Family Strabomantidae), commonly called Noble's Pygmy Frog; females measured less than half an inch (12.5 mm) in body length, whereas males are just a bit longer than 1 cm. More recently,Teran-Valdez and Guayasamin (2010) described Pristimantis minimus from Ecuador with a maximum body length of 13.7 mm.  Below is a group of photos of some of these tiny frogs taken from a variety of sources on the web. Being small allows these species to exploit resources unavailable to larger frogs. JCM

Ellsemere Island Eocene Climate & Giant Reptiles

Ellesmere Island is adjacent to Greenalnd and covered with ice and permafrost today, but in the past it contained lush vegetation and some large reptiles. Jaelyn Eberle from the University of Colorado and colleagues have examined oxygen isotope ratios from Ellesmere fossil vertebrates that were 52 to 53 MY old and concluded that the warmest months on Ellesmere during the early Eocene averaged 66 to 68 degrees F (19-20 degrees C) and the coldest months averaged 32 to 38 degrees F (0-3.5 degrees F). Therefore it probably did not freeze, or freezing was not frequent.The island is known to have supported populations of giant tortoises and crocodilians as well as a variety of large mammals. Today there is concern that the Ellesmere fossil beds are threatened by coal mining. [Full Citation: Eberle et al. Seasonal variability in Arctic temperatures during early Eocene time. Earth and Planetary Science Letters, 2010; 296 (3-4): 481 DOI: 10.1016/j.epsl.2010.06.005]

Saturday, August 28, 2010

UK Medics Mis-Diagnosis Snake Bite Twice

A 54 year old woman was bitten by  the Adder, Vipera berus, in her garden in Eastleigh. Her ankle swelled, her leg was painful, and she suffered severe headaches. She went to Eastleigh Health Center where the doctor gave her antibiotics and assured her it was not a snakebite.The following day she was still in pain and went to Royal Hampshire County Hospital where the doctors dismissed the claim that she was bitten by a snake.The woman contacted Grange Reptiles and was told by an employee who had been a former paramedic that it was indeed a snakebite. She was admitted to Southampton General Hospital. Hampshire Chronicle, 28 August 2010. Apparently snakebite is rare enough in the UK that medical personnel have not been trained to deal with it. The same is probably true in much of the US.

Indigo Snake Conservation Effort

Project Orianne is an Indigo Snake conservation initiative that works to conserve and restore eastern indigo snake populations as well as other species of rare reptiles including Chinese Alligators, Montane Vipers, and Tortoises. The Orlando Sentinel (August 26, 2010) reports that the Lake County commissioners approved a change in zoning that will allow Project Orianne to use a 25 acre plot to culture snakes, despite a complaint form a neighbor. Fred Antonio, former curator of the Central Florida Zoo will be director of the project. JCM

Friday, July 23, 2010

Two Notes on the Reproduction of P. molurus

Two articles published in Reptile Rap, The Newsletter of the South Asian Reptile Network,  No. 10, June 2010 describe aspects of Python molurus reproduction.

Ramesh, C. and S. Bhupathy. 2010. A report on the unusual body weight of a hatchling Python molurus molurus. Reptile Rap (10):22-23.

This article describes a mean body weight of 111.2 g for a clutch of eggs laid in Keoladeo National National Park. However, one hatchling found dead near the nest weighed 200 g and showed no signs of deformity. Upon dissection the hatchling was found to have a mass of fat along the gut that may have disrupted normal body functions.

Balakrishnam, P. et al. 2010. Artificial incubation, hatching and release of the Indian Rock Python Python molurus (Linneaus, 1758), in Nilambur, Kerala. Reptile Rap (10):24-27.

Balakrishnam et al. used an environment chamber to incubate a batch of P. molurus eggs that were abandoned by the female due to human disturbance. The clutch of 17 eggs were kept between 28-32C and a relative humidity of 70-90%. Only one of the eggs hatched, the other eggs were opened and found to contain well developed embryos. The authors report that a large number of pythons are caught in lowland Nilambur and are translocated by the Forestry Department, a significant number of females snakes are killed and their eggs are left. A regional education program is in place to help protect snakes.

Wednesday, July 21, 2010

Florida Burmese Pythons are Regulating Egg Temperatures

The first report of a female Burmese Python using shivering thermogenesis in the wild has been described by Snow et al. (2010). The researchers placed data loggers in and around the brooding female python and found the female snake both warmed and cooled her eggs by generating body heat and cooling them through insulation.

Snow, R. W. et al. 2010. Thermoregulation by a brooding Burmese Python (Python molurus bivittaus) in Florida. Southeastern Naturalist 9(2):403-405.