Mexican beaded lizard

info:

The Beaded lizard (Heloderma horridum) is a species of venomous lizard found principally in Mexico and southern Guatemala. Along with its congener, the Gila monster (Heloderma suspectum), it is the only lizard to have evolved an overt venom delivery system, and has long been considered the only venomous lizard. The beaded lizard is larger than the Gila monster but has duller coloration, black with yellowish bands of differing width depending on the subspecies. A specialized predator that feeds primarily upon eggs, the primary use of its venom is still a source of debate among scientists. However, this venom has been found to contain several enzymes useful for manufacturing drugs in the treatment of diabetes, and research on the pharmacological use of its venom is ongoing.

Threatened throughout its range by overcollection and habitat loss, it is a CITES protected animal. The Motagua Valley subspecies (H. h. charlesborgeti) is one of the rarest lizards in the world, with a wild population of less than 200 animals.

habitat

The beaded lizard is found in the Pacific drainages from Southern Sonora to Southwestern Guatemala and two Atlantic drainages, from Central Chiapas to Southeastern Guatemala. Their habitat is primarily tropical deciduous forest and thorn scrub forest, but are found in pine-oak forest, with elevations from sea level to 1500 meters. In the wild, the animals are only active from April to mid-November, spending about an hour per day above the ground.

The nominate subspecies H. h. horridum is found in Mexico, from Sonora to Oaxaca. The Rio Fuerte beaded lizard (H. h. exasperatum) is found from southern Sonora to northern Sinaloa. The Black beaded lizard ( H. h. alvarezi) is found in the northern Chiapas and the depression of the Río Lagartero in Huehuetenango to northwestern Guatemala. The ranges of these three subspecies overlap, making them sympatric. The Motagua Valley subspecies (H. h. charlesbogerti) is the only allopatric one, separated from the nearest population (H. h. alvarezi) by 250 km of unsuitable habitat.[13] The Motagua Valley beaded lizard is the most endangered of the subspecies if not of all lizards; it is found only in the dry valley of the Río Motagua in the north-east of Guatemala; it is believed less than 200 of these animals exist in the wild.

venom:

The venom glands of the beaded lizard are modified salivary glands located in the animal's lower jaw. Each gland has a separate duct leading to the base of its grooved teeth. When biting, the beaded lizard hangs on its victim and chews in order to get its venomous saliva into the wound. Although its jaw grip is strong its unsocketed teeth are easily broken off at their bases. The beaded lizard's venom is a weak hemotoxin and although human deaths are rare, it can cause respiratory failure. It consists of a number of components, including L-amino acid oxidase, hyaluronidase, phospholipase A, serotonin, and highly active kallikreins that release vasoactive kinins. The venom contains no enzymes that significantly affect coagulation. Almost all documented bites (eight in the past 100 years) have resulted from prodding captive animals with a finger or bare foot.

While invertebrates are essentially immune to the effects of this venom, effects on vertebrates are more severe and varied. In mammals such as rats, major effects include a rapid reduction in carotid blood flow followed by a marked fall in blood pressure, respiratory irregularities, tachycardia and other cardiac anomalies, as well as hypothermia, edema, and internal hemorrhage in the gastrointestinal tract, lungs, eyes, liver, and kidneys. In humans, the effects of bites are associated with excruciating pain that may extend well beyond the area bitten and persist up to 24 hours. Other common effects of bites on humans include local edema (swelling), weakness, sweating, and a rapid fall in blood pressure. Beaded lizards are immune to the effects of their own venom.
The Mexican beaded lizard's base color is black, with yellow bands or patches.

The compounds which have been studied in its saliva have pharmacological properties relating to diabetes, Alzheimer’s disease and even HIV. This hormone was named exendin-3 and is marketed by Amylin Pharmaceuticals as the drug:Exenatide. One study done in 1996 revealed that it binds to cell receptors from breast cancer cells and may stop the growth of lung cancer cells.

Gila monster

info:

the Gila monster , Heloderma suspectum, is a species of venomous lizard native to the southwestern United States and northerwestern Mexican state of Sonora. A heavy, slow-moving lizard, up to 60 centimetres (2.0 ft) long, the Gila monster is the only venomous lizard native to the United States and one of only two known species of venomous lizards in North America, the other being its close relative, the Mexican beaded lizard (H. horridum). Though the Gila monster is venomous, its sluggish nature means that it represents little threat to humans. However, it has earned a fearsome reputation and is sometimes killed by hikers and homeowners despite being protected by state law in Arizona and Nevada.

habitat

The Gila monster is found in the Southwestern United States and Mexico, a range entailing Sonora, Arizona, parts of California, Nevada, Utah, and New Mexico (but not Baja California). They inhabit scrubland, succulent desert, and oak woodland, seeking shelter in burrows, thickets, and under rocks in locations with ready access to moisture. In fact, Gila monsters seem to like water and can be observed immersing themselves in puddles of water after a summer rain. They avoid living in open areas such as flats and farmland.

Venom

Venom is produced in modified salivary glands in the Gila monster's lower jaw, unlike snakes, whose venom is produced in the upper jaw. The Gila monster lacks the musculature to forcibly inject the venom; instead, the venom is propelled from the gland to the tooth by chewing. Capillary action brings the venom out of the tooth and into the victim. The teeth are loosely anchored, which allows them to be broken off and replaced throughout life. Gila monsters have been observed to flip over while biting the victim, presumably to aid the flow of the venom into the wound. Because the Gila monster's prey consists mainly of eggs, small animals, and otherwise "helpless" prey, it is thought that the Gila monster's venom evolved for defensive rather than for hunting use. A defensive use would explain the Gila monster's bright warning coloration.
A reticulate Gila monster (Heloderma suspectum suspectum)

Although the venom is a neurotoxin as toxic as that of a Coral Snake, H. suspectum produces only small amounts. The Gila monster's bite is normally not fatal to adult humans. There are no confirmed reports of fatalities after 1939, and those prior to that year are suspect due to the primitive dangerous "treatments." The Gila monster can bite quickly (especially by swinging its head sideways) and hold on tenaciously and painfully. If bitten, the victim may need to fully submerge the attacking lizard in water to break free from its bite. Symptoms of the bite include excruciating pain, edema, and weakness associated with a rapid drop in blood pressure. More than a dozen peptides and proteins have been isolated from the Gila monster's venom, including hyaluronidase, serotonin, phospholipase A2, and several kallikrein-like glycoproteins responsible for the pain and edema caused by a bite. Four potentially lethal toxins have been isolated from the Gila monster's venom, including horridum venom, which causes hemorrhage in internal organs and exophthalmos (bulging of the eyes), and helothermine, which causes lethargy, partial paralysis of the limbs, and hypothermia in rats. However, the constituents most focused on are the bioactive peptides, including helodermin, helospectin, exendin-3, and exendin-4. Most are similar in form to vasoactive intestinal peptide (VIP), which relaxes smooth muscle and regulates water and electrolyte secretion between the small and large intestines. These bioactive peptides are able to bind to VIP receptors in many different human tissues. One of these, helodermin, has been shown to inhibit the growth of lung cancer.

KOMODO DRAGON

Komodo, atau yang biasanya disebut biawak komodo (Varanus komodoensis), adalah spesies kadal terbesar di dunia yang hidup di pulau Komodo, Rinca, Flores, Gili Motang, dan Gili Dasami di Nusa Tenggara.[2] Biawak ini oleh penduduk asli pulau Komodo juga disebut dengan nama setempat ora.

Termasuk anggota famili biawak Varanidae, dan klad Toxicofera, komodo merupakan kadal terbesar di dunia, dengan rata-rata panjang 2-3 m. Ukurannya yang besar ini berhubungan dengan gejala gigantisme pulau, yakni kecenderungan meraksasanya tubuh hewan-hewan tertentu yang hidup di pulau kecil terkait dengan tidak adanya mamalia karnivora di pulau tempat hidup komodo, dan laju metabolisme komodo yang kecil. Karena besar tubuhnya, kadal ini menduduki posisi predator puncak yang mendominasi ekosistem tempatnya hidup.

Komodo ditemukan oleh peneliti barat tahun 1910. Tubuhnya yang besar dan reputasinya yang mengerikan membuat mereka populer di kebun binatang. Habitat komodo di alam bebas telah menyusut akibat aktivitas manusia dan karenanya IUCN memasukkan komodo sebagai spesies yang rentan terhadap kepunahan. Biawak besar ini kini dilindungi di bawah peraturan pemerintah Indonesia dan sebuah taman nasional, yaitu Taman Nasional Komodo, didirikan untuk melindungi mereka.

venom:

Pada akhir 2005, peneliti dari Universitas Melbourne, Australia, menyimpulkan bahwa biawak Perentie (Varanus giganteus) dan biawak-biawak lainnya, serta kadal-kadal dari suku Agamidae, kemungkinan memiliki semacam bisa. Selama ini diketahui bahwa luka-luka akibat gigitan hewan-hewan ini sangat rawan infeksi karena adanya bakteria yang hidup di mulut kadal-kadal ini, akan tetapi para peneliti ini menunjukkan bahwa efek langsung yang muncul pada luka-luka gigitan itu disebabkan oleh masuknya bisa berkekuatan menengah. Para peneliti ini telah mengamati luka-luka di tangan manusia akibat gigitan biawak Varanus varius, V. scalaris dan komodo, dan semuanya memperlihatkan reaksi yang serupa: bengkak secara cepat dalam beberapa menit, gangguan lokal dalam pembekuan darah, rasa sakit yang mencekam hingga ke siku, dengan beberapa gejala yang bertahan hingga beberapa jam kemudian. Sebuah kelenjar yang berisi bisa yang amat beracun telah berhasil diambil dari mulut seekor komodo di Kebun Binatang Singapura, dan meyakinkan para peneliti akan kandungan bisa yang dipunyai komodo.

Di samping mengandung bisa, air liur komodo juga memiliki aneka bakteri mematikan di dalamnya; lebih dari 28 bakteri Gram-negatif dan 29 Gram-positif telah diisolasi dari air liur ini. Bakteri-bakteri tersebut menyebabkan septikemia pada korbannya; jika gigitan komodo tidak langsung membunuh mangsa dan mangsa itu dapat melarikan diri, umumnya mangsa yang sial ini akan mati dalam waktu satu minggu akibat infeksi. Bakteri yang paling mematikan di air liur komodo agaknya adalah bakteri Pasteurella multocida yang sangat mematikan; diketahui melalui percobaan dengan tikus laboratorium. Karena komodo nampaknya kebal terhadap mikrobanya sendiri, banyak penelitian dilakukan untuk mencari molekul antibakteri dengan harapan dapat digunakan untuk pengobatan manusia.

KOMODO