2. 수생양서류
1) 수생양서류는 유생 단계에 아가미로 호흡을 하며, 꼬리를 갖 는 유미류(Urodeles ; 도롱뇽, 영원, axolotol 등)와 꼬리가 없는 무미류(Anurans ; 개구리, 두꺼비 등), 그리고 다리가 없 는 무지류 (Apodans ; caecilian)가 있다.
2) 유생 단계에서는 내골격이 없는 지느러미를 가지 고 헤엄치지만, 변태하여 다리를 가지며, 늑골이 없으며 견갑골과 좌골(ischium)을 갖는다.
Amphibians (class Amphibia), such as frogs, toads, salamanders, newts, and gymnophiona, are cold-blooded animals that metamorphose from a juvenile, water-breathing form to an adult, air-breathing form. Typically, amphibians have four limbs. Unlike other land animals (amniotes), amphibians lay eggs in water, as their fish ancestors did. Amphibians are
superficially similar to reptiles.
In recent decades, there has been a dramatic decline in amphibian populations around the globe (e.g., chytridiomycosis) and many species are now threatened or extinct. Scientists do not agree on the cause.
Kingdom Animalia Phylum Chordata Subphylum Vertebrata Class Amphibia
Subclass Lepospondyli - extinct Subclass Lissamphibia
Order Anura (frogs, toads)
Order Caudata (Urodeles ; salamandas, newts) Order Gymnophiona (Apodans ; cecilians)
The caecilians are an order (Gymnophiona or Apoda) of amphibians that superficially resemble earthworms or snakes. They mostly live hidden in the ground, widely
unknown. Caecilians completely lack limbs, making the smaller species resemble worms, while the larger species with lengths up to 1.5 m (4.9 ft) resemble snakes. The tail is short or absent, and the cloaca is near the end of the body.
The amphibian metamorphosis
1. Formation of four legs in order to support the body on land.
2. The gills are replaced by other respiratory organs, i.e., lungs.
3. The skin changes and develops glands to avoid dehydration.
4. The eyes develop eyelids and adapt to vision outside the water.
5. An eardrum is developed to lock the middle ear.
6. In frogs and toads, the tail disappears.
3) 물속에서의 유영을 위하여 발가락 사이에 물갈퀴(webbing) 가 발달하였으며, 청개구리 등은 나무를 기어오르기 위하여 발 가락 끝에 둥근 모양의 돌기(toe pads=disc-like distal
protuberances)가 있다. 눈은 얇고 투명한 막(nictitating membrane)으로 보호된다.
4) 많은 점액선을 갖는 피부는 보호(두꺼비와 같이 독성물질 함 유)와 위장(색소체에 의해) 기능뿐만 아니라 중요한 호흡기관 이며, 양방향으로 물이 침투할 수 있는 삼투압 조절기관으로 주위의 환경 위험요소에 매우 민감하다.
따라서 피부의 투과성 때문에 건조한 곳 에서 살 수 없다.
사진. 좌 ; 낙엽에 위장한 개구리, 우 ; 피부에 독선이 발달한 두꺼비
먹이사슬 역전, 뱀 잡아먹는 독두꺼비 발견
언론 보도에 따르면, 케인 토드의 유일한 천적인 호주 '킬백 스네이크(Keelback snake)'를 산 채로 먹던 두꺼비는 최근 호 주 다윈 남쪽 100km에 위치한 링우드에서 발견되었다.
커다란 몸집의 암컷 두꺼비는 자신보다 몸 길이가 훨씬 긴 킬백 스네이크를 먹어치우 고 있었는데, 호주 민물 뱀의 한 종류인 킬 백 스네이크는 그 동안 독두꺼비를 잡아먹 을 수 있는 유일한 뱀으로 알려진 동물이었 다. 포식자와 피식자의 관계가 역전되었다 는 사실에 환경단체 관계자 등 전문가들이 큰 충격을 받았다는 것이 언론의 설명이다.
두꺼비가 천적인 뱀을 잡아먹는 광경을 발
견한 환경단체 관계자는 "이 같은 사실을
도저히 믿을 수 없다"면서 큰 우려를 표시
했다.
* 긴 털에 발톱 가진 '털이 난 괴물 개구리' 화제 **
긴 털이 있는 몸통에 고양이과 동물과 비슷한 갈고리 발톱을 가진 '괴물 개구리'가 해외 네티 즌들 사이에서 화제다.
28일 뉴사이언티스트에 소개되면서 네티즌들 의 두 눈을 의심하게 만들고 있는 동물은 아프 리카 콩고, 카메룬, 가봉 등 중부 아프리카에 서식하는 '트리초바트라추스 로부스투스'라는 학명의 개구리다.
'T-로부트투스' 혹은 '털난 개구리'로 불리는 이 동물의 생태는 미국 하버드 대학교의 생물 학자 데이비드 블랙번에 의해 밝혀졌는데, 이 개구리가 방어용 무기로 사용하는 발톱의 구 조가 고양이과 동물과 흡사한 동시에 전혀 다 르다는 것이 연구팀의 설명.
연구팀에 따르면, 털난 개구리의 발톱은 평상 시에는 고양이와 비슷하게 밖으로 돌출되어 있지 않다. 위급한 상황에 처하면 피부 속의 발톱이 튀어 나와 방어용 무기로 사용한다는
것. 또 이 개구리의 발톱은 자신의 '뼈'로 만들어진 종류로, 다른 척추동물들의 발톱과는 전혀 다른 특징을 가 지고 있다고 연구팀은 설명했다.
자신의 뼈를 이용해 날카로운 고양이 발톱을 만들어내는 이 개구리는 네티즌들 사이에서는 '울버린 개구리'로 도 불리는데, 손등에서 날카로운 발톱이 튀어나오는 영화 엑스맨의 주인공 '울버린'과 모습이 흡사하다는 것이 그 이유.(조선일보 ; 2008. 5. 31)
* 그림. 흰색 올챙이, 황금개구리, 투명개구리, 초소형개구리 (좌측 위로부터 시계 방향으로)
5) 대부분의 양서류에서 유생은 어릴 때는 아가미로 수중호흡을 하고, 성장하면 콧구멍을 통하여 폐로 공기호흡을 한다. 북미 산 도롱뇽의 일종인 mudpuppy[=waterdog ;
Necturus
spp.와 human fish(=olm ;
Proteus anguinus
)]와 axolotl (Ambystoma mexicanum
)은 일생 동안 변태를하지 못하고 4개 또는 6개의 외부로 돌출된 아가미(외새 ; external gill)를 가지며 물속에서 생활
한다(유형성숙 ; neoteny). 또한 양서 류는 피부(특히 복부)와 구인강(bucco- pharyngeal cavity)를 통하여 호흡한다.
Salamander (orig. from Persian: sām, "fire", and andarūn, "within") is the common name for a group of approximately 500 species of amphibians. They are typically characterized by slender bodies, short noses, and long tails. All known fossil and extant species fall under the order Caudata, while
sometimes the extant species are grouped together as the Urodela. Most salamanders have four front toes and their hind legs have five. Their moist skin usually makes them reliant on habitats in or near water, or under some protection (e.g., moist ground), often in a wetland. Some salamander species are fully aquatic throughout life (axolotls), some take to the water intermittently (newts), and some are entirely terrestrial as adults (salamandas). Uniquely among vertebrates, they are capable of
regenerating lost limbs, as well as other body parts.
Class : Amphibia → Order : Caudata → Suborder : Cryptobranchoidea (Giant salamanders),
Salamandroidea (Advanced salamanders),
Sirenoidea (Sirens)
A newt is any number of amphibians in the Pleurodelinae subfamily (family Salamandridae), found in North America, Europe and Asia. The larvae leave the water as a terrestrial form called an eft.
The adult form has a lizard-like body and is either aquatic or semi- aquatic. The main breeding season for newts is between the months of February and June. After courtship rituals of varying complexity, which take place in ponds or slow moving streams, the eggs are fertilized outside the female's body. Their eggs are laid singly, attached to aquatic plants. This distinguishes them from the free-floating eggs of frogs or toads, that are laid in clumps or in strings. Plant leaves are usually folded over and adhered to the eggs to protect them. The tadpoles, which resemble fish fry but are distinguished by their feathery external gills, hatch in about three weeks. After hatching they eat algae, small invertebrates or other tadpoles.
During the next few months the tadpoles undergo metamorphosis, during which they develop legs, and the gills change into air-breathing lungs. Some species, such as the North American newts, also become more brightly colored during this phase. Once fully metamorphosed they leave the water and live a terrestrial life, when they are known as
"efts". Only when the eft reaches adulthood will the North American species return to live in water, rarely venturing back onto the land.
Conversely, most European species live their adult lives on land and only visit water to breed. There is no report of finding species of newt in Korea.
A red-spotted newt (eft stage) showing bright aposematic colouration to warn predators of its highly toxic skin.
An alpine newt (larval stage) showing external gills.
Class : Amphibia → Order : Caudata → Family : Salamandriae
The axolotl (fig. 1 ; Ambystoma mexicanum) is the best-known of the Mexican neotenic mole salamanders belonging to the Tiger Salamander complex. Larvae of this species fail to undergo metamorphosis, so the adults remain aquatic and gilled. The species originates from the lake underlying Mexico City and are also called ajolote (which is also the common name for Mexican Mole Lizards). Axolotls are used extensively in scientific research due to their ability to regenerate most body parts, ease of breeding, and large embryos. They are commonly kept as pets in the United States, Great Britain (under the spelling axlotl), Australia, Japan (sold under the name wooper rooper (ウーパールーパー) and other countries.
Axolotls should not be confused with the larval stage(fig. 2-a) of the closely related Tiger Salamanders (fig. 2 ; Ambystoma tigrinum and Ambystoma mavortium), which is widespread in much of North America which also occasionally become neotenic, nor with mudpuppies (fig. 3 ; Necturus spp.), fully-aquatic salamanders which are unrelated to the axolotl but which bear a superficial resemblance.
As of 2008, wild axolotls are near extinction, due to urbanization in Mexico City, and polluted waters. Nonnative fish such as African tilapia and Asian carp have also recently been introduced to the waters. These new fish have been eating the axolotls' babies, as well as its primary source of food. The axolotl is currently on the International Union for Conservation of Nature's annual Red List of threatened species. The Axolotl is now on the CITES endangered species list. There have been efforts to breed and release the animal, in order to re-establish its numbers.
Class : Amphibia → Order : Caudata → Family : Ambystomatidae
Axolotls of various colours occur in captivity, including grey, shades of brown, leucistic (white with black eyes), golden albino, white albino, as well as other varieties, such as the melanoid (a near-black animal).
The normally coloured axolotl, the "wild type", can be near-black like the one in the group photo (fig. 1) to the below, chocolate brown like the one in the site's logo, or even creamy in colour.
Axolotl is a worthy study due to its amazing healing and regeneration abilities. Normal wound healing in animals occurs through the growth of scar tissue, which is not the same as the original tissue, nor is it as robust. However the axolotl is fully capable of complete limb re-growth (fig. 3). The animal has the added scientific attraction of having especially large embryos, making it easier to deal with under laboratory conditions. Its embryo is also very robust, and can be spliced and combined with different parts of other axolotl embryos with a high degree of success.
The axolotl is a fascinating creature for a number of reasons, including its grotesque appearance, its ability to regenerate, and primarily the fact that it exhibits the phenomenon known as neoteny. Ordinarily,
amphibians undergo metamorphosis from egg to larva (the tadpole of a frog is a larva), and finally to adult form. The axolotl remains in its larval form throughout its life. This means that it retains its gills and fins, and it doesn't develop the protruding eyes, eyelids and characteristics of other adult salamanders. It grows much larger than a normal larval salamander, and it reaches sexual maturity in this larval stage.
Neoteny is sometimes found in other amphibians, but tends to be caused by low levels of iodine (thyroxine hormones, necessary for growth and development), or possibly by random genetic mutation. Research has also shown that very low temperatures can suppress the production of these hormones, thus also inducing neoteny.
In the Axolotl, neoteny is now totally genetic. When treated with hormones, the axolotl will usually begin to metamorphose, but in very rare cases it will metamorphose spontaneously,
such as the metamorphosed wild type axolotl pictured here(fig. 2). The metamorphosed wild type axolotl bears a close resemblance to the Mexican subspecies of the
Tiger Salamander (Ambystoma velasci).
국제 야생동식물 멸종위기종 거래 에 관한 조약(Convention on International Trade in
Endangered Species of Wild Flora and Fauna, CITES)은 국
제자연보호연맹(IntenationalUnion for Conservation of Nature)회원 협의에서 1963년 결의안이 채택되어 입안되었다.
조약의 목적은 야생동식물종의 국 제적인 거래가 동식물의 생존을 위협하지 않게끔 하고 여러 보호 단계를 적용하여 33,000 생물 종 의 보호를 보장하는 데 있다.
1975년 조약이 강제된 결과
CITES에 의해 보호를 받는 단 한
종도 멸종되지 않았다고 하지만
이에 대한 논란의 여지 또한 있다.
5) 암수딴몸이며 체외수정을 하며 젤라틴의 막으로 둘러싸인 알 을 물속에 낳는다. 무미류의 경우 암수가 몸을 밀착시켜 산란 즉시 알에 정자를 사정하는 포접(amplexus)을 하며, 물에 알 을 낳기 때문에 산란기는 강수량과 밀접한 관계가 있다. 무
미류와 유미류의 일부는 체내수정을 하며, 나무나 땅위에 알을 낳는 경우도 있다. 대부분의 양서류는 난생이나, 일부 난관을 통해 영양분을 공급받아 완전 변태된 개체를 낳기도 하며(태 생), 난관이나 입, 위, 피부 주머니에서 알을 보호하다가 변태 후 방출하는 난태생도 있다.
6) 변온동물로 2심방 1심실이며, 성체와 유생이 모두 육식성이 고, 온대에서는 겨울철에 동면을 한다.
7) 신장은 발생학적으로 중신을 가지며, 질소노폐물을 암모니아 상태로 배출한다.
* 대부분의 파충류는 심실이 불완전한 격막으로 나뉘어진 심장을 가지나, 악어류는 완전한 격막으로 심실이 완전히 분리된 심장을 갖는다(그림의 예가 잘못되었음).
3. 수생파충류
1) 외부형태 및 골격계
(1) 수생파충류는 거북류(chelonian), 악어류(crocodilian), 그리고 비늘을 갖는 유린류(squamate)가 있는데, 유린류에는 도마뱀
(lizard)와 뱀(snake)이 속하며, 몸이 짧은 것과 길은 것 등 다양한 체형이 있다.
(2) 뱀류와 일부 도마뱀을 제외하고는 보통 2쌍의 다리를 가지며, 발은 발톱을 갖는 5개의 발가락을 가지고 있다.
(3) 골격은 환경의 적응에 따라 다양한 진화 양 상을 보이며, 뱀의 경우 사지가 퇴화되어 있으 며, 바다거북의 경우 지느러
미 모양(flipper)으로 변형되 어 있다.
Evolution of Reptiles
While many kinds of reptiles once dominated the earth, only four orders have living
representatives. The largest of these groups comprises the Squamata, which include lizards
and snakes. Turtles and tortoises belong to the order Chelonia, and crocodiles, alligators,
caimans, and gavials to the order Crocodilia. The tuatara, often called a living fossil, is the
only extant member of the order Rhynchocephalia. Prominent among extinct reptiles were
the saurischians (Tyrannosaurus and other “reptile-hipped” bipedal carnivores), from
which birds arose, and the ornithischians (“bird-hipped” herbivores such as Stegosaurus
and Hypsilophodon). Mammals arose from the therapsid line.
The tuatara is a reptile endemic to New Zealand which, though it resembles most lizards, is actually part of a distinct lineage, order Sphenodontia. The two species of tuatara are the only surviving members of its order, which flourished around 200 million years ago. Their most recent common ancestor with any other extant group is with the squamates (lizards and snakes). For this reason, tuatara are of great interest in the study of the evolution of lizards and snakes, and for the reconstruction of the appearance and habits of the earliest diapsids (the group that also includes birds and
crocodiles).
Tuatara are greenish brown, and measure up to 80 cm (31 in) from head to tail-tip with a spiny crest along the back,
especially pronounced in males. Their dentition, in which two rows of teeth in the upper jaw overlap one row on the lower jaw, is unique among living species. They are further unusual in having a pronounced parietal eye, dubbed the
"third eye", whose current function is a subject of ongoing
research. They are able to hear although no external ear is
present, and have a number of unique features in their
skeleton, some of them apparently evolutionarily retained
from fish. Although tuatara are sometimes called "living
fossils", recent taxonomic and molecular work has shown
that they have changed significantly since the Mesozoic era.
Juvenile American alligator (Alligator mississippiensis)
Juvenile Cuvier's dwarf caiman (Paleosuchus palpebrosus)
Adult male saltwater crocodile (Crocodylus porosus)
Adult Indian gharial (Gavialis gangeticus)
From the left: Heads of the Indian gharial (Gavialis gangeticus), American Alligator (Alligator
mississippiensis), and an American Crocodile (Crocodylus acutus).
Taxonomy
Superorder Crocodylomorpha Order Crocodilia
Superfamily Gavialoidea
Family Gavialidae: gharials & false gharials Superfamily Alligatoroidea
Family Alligatoridae
Subfamily Alligatorinae: alligators Subfamily Caimaninae: caimans Family †Diplocynodontidae
Superfamily Crocodyloidea Family Crocodylidae
Subfamily Crocodylinae: crocodiles Subfamily †Mekosuchinae
보아, 파이돈, 아나콘다와 같은 큰 뱀의 꼬리 쪽 배에는 소위 발톱 혹은 가시가 관찰되는데, 이것 이 흔적기관으로 사용되는 예 중의 하나이다. 그것들이 해부학적으로 다른 파충류의 뒷다리들이 나타나는 부분에 위치해 있기 때문에 다리의 흔적이라고 주장된다. 아나콘다와 파이돈의 경우 그것들은 아주 조금만 노출된다.
Griehl (1982)은 이 뱀들의 뼈가 아직도 골반 뼈와 뒷다리의 흔적 을 나타내며, 물론 이 다리의 흔적들은 모든 이동 기능을 상실하였 다라고 하였다. 그러나 이러한 가시의 실제 기능에 대해 덧붙이기를 아마도 그 가시들은 수컷이 암컷을 자극하는데 사용되는 것 같다고 하였다. 이 뱀들이 과거에 다리를 가졌다가 진화적 선택에서 다리를 잃었다는 가정은 전혀 화석 증거가 없다. 다리의 손실과 같은 변화는 만약 실제 그런 일이 일어났다면 화석 기록에 잘 보존되었을 것이다.
Dewar (1957)는 이 발톱들이 실제 기능을 한다고 결론지었다. 이 부속물들은 이동할 때 특히 나무를 오르거나 가지에 걸려있기 위해 큰 뱀의 경우 도움을 주는 게 확실하다고 하였다. 이러한 유용성은 그 동물의 골반에 붙어 있는 방식에 의해 지지되는데, 그런 점이 그 것들을 넓적다리와 상동인 것처럼 보이게 한다.
* 뱀의 흔적기관(발톱 혹은 가시) *
9천만 년 전, 다리 가진 뱀 발견
8년 전 레바논에서 발견된 석회암 속 동물 화석이 대단히 중요한 표본이라는 사실을 프랑스 과학자들이 통해 밝 혀냈다. 그것은 다리를 가진 뱀이었다. 다리를 가진 뱀 표본은 극히 희소하다.
11일 BBC 등 해외 언론의 보도에 따르면, 프랑스 그래노블에 있는 ESRF의 과학자들은 거의 모든 것은 투시하 는 강력한 X레이를 이용해 화석의 2D 이미지들을 만들어내고 그것을 3D로 합성해냈다.
그 결과 9천 2백만 년 전의 뱀에 다리가 달려 있는 것이 확인되었다. 발견된 뒷다리는 2cm길이였고 85cm 크기 의 이 뱀(Eupodophis descouensi)은 이 다리를 이용하지는 않았을 것으로 추정된다.
이번에 발견된 뱀 화석은 최소 1억 5천년만 전에 나타난 뱀의 진화론적 경위를 설명하는 중요한 자료가 될 수 있다.
뱀의 진화에 대해서는 두 가지 이론이 경합한다. 도마뱀이 육지 생활에 적응하면서 다리를 잃어 뱀이 되었다는 설과 수중 파충류가 기원이라는 주장이 경쟁하고 있는 것이다.
(4) 두개골은 1개의 뼈로 되어 있는 포유류와 달리 아래턱에 많은 뼈가 있다.
(5) 파충류의 치골(teeth)에는 긴 원뿔형의 이가 있고, 독사
(venomous snake)는 한 쌍 또는 여러 쌍의 독이빨(fang)을 가지 고 있다.
(6) 악어류와 거북은 흉골(sternum)과 골반골(pelvis) 사이에 복 강을 둘러싸는 표피성 골격인 gastralia(abdominal rib)를 가지고 있다.
Gastralia (singular gastralium) are dermal bones found in the ventral body wall of crocodilian and Sphenodon species. They are found between the sternum and pelvis, and do not articulate with the vertebrae. In modern animals, they provide support for the abdomen and attachment sites for abdominal muscles.
These bones may have been derived from the ventral scales found in animals like rhipidistians, labyrinthodonts, and Acanthostega, and may be related to ventral elements of turtle plastrons.
Similar but not homologous cartilagenous elements are found in the ventral body walls of lizards and anurans. The terminology for these groups of structures is confused; both types, along with sternal ribs (ossified costal cartilages), have been called abdominal ribs, a term which should be avoided.
Tyrannosaurus gastralia
cartilagenous elements
The body of a turtle or tortoise is encased in a shell made up of a series of bony plates covered with a horny shield(scales). The vertebrae and ribs are fused to the inside of this shell, giving it additional support and strength. It is impossible for the creatures to crawl out of their shells.
Turtles have a relatively flattened shell and are aquatic, while tortoises have a dome-shaped shell and are terrestrial.
Tortoises and Turtles
Skeleton of a turtle: reptile with an oval shell and a horned beak. It has a very short tail and four short legs, and moves very slowly.
plastron
2) 피부
(1) 몸은 방수성의 각질 또는 골화된 여러 모양의 표피성 비늘 (epidermal scales 또는 scutes)로 된 외골격으로 덮혀 있다.
(2) 거북은 비늘로 덮힌 머리와 다리를 제외하고 골질의 진피성 갑 판(bony dermal plate=shell)으로 덮혀 있는데, 척추골과 늑골이 유착되어 있는 배갑(carapace)과 복갑(plastron)이 뼈(bridge of bone)로 연결되어 있다.
(3) 피부에는 샘(gland)이 없는 건조한 피부를 가지고 있어, 몸 안의 수분을 보존할 수 있어서 건조한 지역에서도 살 수 있다.
(4) 뱀은 자라면서 탈피(ecdysis=shedding)를 하여 성장한다.
(5) 피부색은 위장색이거나 독이 있음을 경고하는 화려한 색을 띤다.
Ecdysis of snake
The shedding of scales is called ecdysis (or in normal usage, moulting or sloughing). In the case of snakes, the complete outer layer of skin is shed in one layer. Snake scales are not discrete, but extensions of the epidermis—hence they are not shed separately but as a complete outer layer during each moult, akin to a sock being turned inside out.
The shape and number of scales on the head, back, and belly are often characteristic and used for taxonomic purposes.
Scales are named mainly according to their positions on the body. In "advanced" (Caenophidian) snakes, the broad belly scales and rows of dorsal scales correspond to the vertebrae, allowing scientists to count the vertebrae without dissection.
Snake's eyes are covered by their clear scales rather than movable eyelids; therefore, their eyes are always open.
Moulting serves a number of functions. Firstly, the old and worn skin is replaced; secondly, it helps get rid of parasites such as mites and ticks. Renewal of the skin by moulting is supposed to allow growth in some animals such as insects;
however, this has been disputed in the case of snakes.
Moulting occurs periodically throughout a snake's life. Before a moult, the snake stops eating and often hides or moves to a safe place. Just before shedding, the skin becomes dull and dry looking and the eyes become cloudy or blue-colored.
The inner surface of the old skin liquefies. This causes the old skin to separate from the new skin beneath it. After a few days, the eyes clear and the snake "crawls"
out of its old skin. The old skin breaks near the mouth and the snake wriggles out, aided by rubbing against rough surfaces. In many cases the cast skin peels backward over the body from head to tail in one piece, like pulling a sock off inside-out. A new, larger, brighter layer of skin has formed underneath.
Apolysis
the separation of the old cuticles from
the underlying epidermal cells
Secretion of ecdysone
secreted into the exuvial space from
exuvial gland (between the old
cuticle and the epidermis)
Digestion of old cuticle
digested by the enzymes and used
for producing the new cuticle
How to shed?
3) 소화계
(1) 입, 침샘, 식도, 위, 창자, 배설강(cloaca) 등으로 이루어져 있다.
(2) 악어류는 각각 한 줄의 윗니와 아랫니를 가지며, 거북류는 이가 없는 대신에 각질 의 부리(horny beak)가 있어 먹이를 물어 뜯는다.
(3) 뱀과 같이 두개골과 턱의 구조가 특수하게 발달되어 큰 음식물을 삼키는데 편리하다 (무정위운동).
(4) 뱀을 제외하고 파충류는 맹장(cecum)을 가 지며, 악어류는 2개의 위를 가지고 있다.
(5) 파충류는 담낭(gall bladder)을 가지며, 간 장에 멜라닌(melanin)을 함유하고 있어 검 은 점이나 줄무늬를 가지고 있다.
(6) 독사의 경우 한 쌍의 침샘이 독샘으로 진 화되었다.
Feeding and diet of snake
All snakes are strictly carnivorous, eating small animals including lizards, other snakes, small mammals, birds, eggs, fish, snails or insects. Because snakes cannot bite or tear their food to pieces, a snake must swallow its prey whole. The body size of a snake has a major influence on its eating habits. Smaller snakes eat smaller prey.
Juvenile pythons might start out feeding on lizards or mice and graduate to small deer or antelope as an adult, for example
The snake's jaw is a complex structure. Contrary to the popular belief that snakes can dislocate their jaws, snakes have a very flexible lower jaw, the two halves of which are not rigidly attached, and numerous other joints in their skull, allowing them to open their mouths wide enough to swallow their prey whole, even if it is larger in diameter than the snake itself, as snakes do not chew. For example, the African Egg-eating Snake has flexible jaws adapted for eating eggs much larger than the diameter of its head.
This snake has no teeth, but does have bony protrusions on the inside edge of its spine which are used to aid in breaking the shells of the eggs it eats.
Snake eating a rodent Carpet python constricting and
consuming a chicken. Common Egg-eating Snake
산호초에 사는 물고기 곰치(moray eel) 역시 자기 입보다 엄청나게 큰 먹이를 씹지도 않고 그냥 삼켜 버린다.
최근 곰치의 숨겨진 무기가 밝혀졌다. 곰치의 턱은 영화에 나오는 외계 생물체와 같은 구조였던 것.
몸길이가 2.7m에 이르는 곰치는 산호초에 난 구멍에 몸을 숨기고 있다가 지나가는 먹이를 잡아챈다. 먹이 대 부분은 덩치가 크고 몸부림이 심한 큰 물고기나 문어, 오징어. 미 데이비스 소재 캘리포니아대의 리타 메타 (Mehta) 박사는 곰치가 두 종류의 턱(jaw)을 활용해 한번 문 먹이를 목구멍으로 이동시킬 수 있다는 사실을 밝혀냈다.
지난 6일자 ‘네이처’지에 게재된 논문에 따르면 곰치가 먹이를 삼키는 과정은 두 단계다. 먼저 입 쪽에 있 는 턱으로 먹이를 강하게 문다. 턱뼈에는 날카로운 이빨이 나있어 먹이 깊숙이 박힌다. 특히 이빨은 목구멍 쪽 으로 휘어져 있어 한번 물린 먹이가 입 밖으로 빠져나가기 어렵게 한다.
이제 숨겨진 괴물이 등장할 차례. 목 안쪽에서 두 번째 턱이 튀어나와 먹이를 잡아채 목구멍으로 끌고 간다.
연구팀은 곰치가 먹이를 잡아채는 장면을 초 단위의 영상을 잡아내는 비디오카메라로 포착했다. 또 곰치의 두 개골을 X선으로 촬영해 두 가지 턱 구조를 알아냈다.
자연에는 곰치 외에도 약 3만 종의 어류가 목구멍 쪽에 제2의 턱을 가지고 있다. 그러나 대부분 먹이를 갈거나 부수는 역할 만 하지 곰치처럼 먹이를 끌고 가는 적극적인 기능은 하지 않 는다. 대부분의 물고기는 흡인력으로 먹이를 목구멍 안으로 빨아들인다.
비단뱀도 곰치처럼 입보다 훨씬 큰 먹이를 삼킨다. 일단 뱀은 큰 먹이를 삼킬 수 있도록 아래위 턱이 벌어진다. 뱀의 위턱은 두개골에 근육과 인대, 힘줄로 연결돼 있다. 상하좌우 어느 방 향으로든 움직일 수 있다.
또 위턱은 아래턱과 정방형 뼈(quadrate bone)로 연결돼 있 다. 이 뼈는일종의 이중관절 경첩 역할을 한다. 덕분에 아래턱 이 위턱과 따로 움직일수 있게 된다. 뱀은 아래위 턱을 최대한 분리시켜 입을 150도까지 벌릴 수 있다고 한다. 발버둥치는 대형 먹잇감도 입 안에 갇혀 버린다. 뱀의 두 번째 무기는 좌우 로 분리되는 아래턱에 있다. 앞에서 보면 턱의 왼쪽과 오른쪽 부분이 한 몸이 아니고 탄력 있는 인대로 연결돼 있다. 일단 먹 이를 물었지만 목구멍 안으로 삼키지 못하면 허사다. 왼쪽과 오른쪽 턱뼈가 분리돼 한쪽은 먹이를 잡고 한쪽은 먹이를 둘 러싸 안으로 민다.(조선일보 ; 2007.9.11)
[사이언스 in 뉴스] 입으로 먹나, 턱으로 먹지!
Python Eats Australian Family Dog
A 16-foot python stalked a family dog for days before swallowing the pet whole in front of horrified children in the Australian tropics, animal experts said Wednesday.
The boy and girl, ages 5 and 7, watched as the scrub python devoured their silky terrier-Chihuahua crossbreed Monday at their home near Kuranda in Queensland state.
Stuart Douglas, owner of the Australian Venom Zoo in Kuranda, said scrub pythons typically eat wild animals such as wallabies, a smaller relative of the kangaroo, but sometimes turn to pets in urban areas.
Copyright 2008 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.
This X-ray reveals the Australian kitten, known as Kohl, inside the gut of a 6-foot-long carpet python. Though the kitten's skull was larger than the snake's girth, the reptile dislocated its jaw to swallow the feline whole.
X-RAY REVEALS PYTHON'S KITTY MEAL
Snake venom is highly modified saliva that is produced by special
glands(venom glands) of certain species of snakes. The gland which secretes the zootoxin is a modification of the parotid salivary gland of other vertebrates, and is usually situated on each side of the head below and behind the eye, invested in a muscular sheath.
It is provided with large alveoli in which the venom is stored before being conveyed by a duct to the base of the channelled or tubular fang through which it is ejected. Snake venom is a combination of many different proteins and enzymes. Many of these proteins are harmless to humans, but some are toxins.
Note that snake venoms are generally
not dangerous when ingested, and are
therefore not technically poisons.
The teeth and bite of small, agile Pakasuchus kapilimai were similar to those of mammals.
Paleontologists scouring a river bank in Tanzania have unearthed a previously unknown crocodile from 105-million-year-old, mid-Cretaceous rock in the Great East African Rift System.
The ancient crocodile Pakasuchus kapilimai once roamed Tanzania in the Middle Cretaceous. No larger than a housecat, the animal had a number of features unusual for crocodylians, including mammal-like teeth(molar teeth).
The discovery of a relatively lanky, cat-sized animal with mammal-like teeth and a land-based lifestyle supports a growing consensus that crocodiles were once far more diverse than they are today, dominating ecological niches in the Southern Hemisphere during the Cretaceous Period that were filled in the Northern Hemisphere by early mammals.
An international team of researchers led by Patrick O'Connor of Ohio University describes the new animal in the Aug. 5 issue of Nature.
Pakasuchus Kapilimai: Prehistoric Crocodile with Mammal Teeth
일 미 플로리다주 마이애미-데이드에 있는 에버글레이즈 국립공원이 제공한 사진으로 악어의 몸통이 죽 은 버마 비단뱀의 구부러진 몸통 오른쪽으로 비어져 나온 모습. 플로리다의 과학자들은 이 버마 비단뱀 이 1m80cm나 되는 악어를 먹다가 위(胃)가 파열된 것이 아닌가 추측하고 있다. 이들 악어와 버마 비단 뱀의 몸통들은 지난달 27일 에버글레이즈 국립공원의 외진 곳에서 발견됐다. 이 사진에서 악어의 뒷다 리와 꼬리가 약 4m나 되는 비단뱀의 파열된 내장에서 비어져 나온 것을 볼 수 있다. 이 뱀의 머리부분도 실종된 상태다. 전문가들은 이 뱀과 악어의 충돌 자체도 흥미로운 것이지만 뱀이 먹이사슬에서 악어와 다툰 것도 흥미로운 것이라고 말했다. (AP=연합뉴스 ; 2005.10.6)
악어 삼킨 비단뱀 숨진 채 발견돼
Gastroliths
Herbivorous reptiles face the same problems of mastication as herbivorous mammals,
but, lacking the complex teeth of mammals, many species swallow rocks and pebbles
(so called gastroliths) to aid in digestion: The rocks are washed around in the stomach,
helping to grind up plant matter. Fossil gastroliths have been found associated with
sauropods. Sea turtles, crocodiles, and marine iguanas also use gastroliths as ballast,
helping them to dive.
파충류(카멜레온)의 내부 장기
A parietal eye(두정안), also known as a parietal organ or third-eye or (often but less correctly) pineal eye, is a part of the
epithalamus present in some animal species.
The eye may be photoreceptive and is usually associated with the pineal gland, regulating circadian rhythmicity and hormone
production for thermoregulation. The lizard- like reptile tuatara has a "well-developed
parietal eye, with small lens and retina". Parietal eyes are also found in lizards, frogs and
lampreys, as well as some species of fish, such as tuna and pelagic sharks, where it is visible as a light-sensitive spot on top of their head. A poorly developed version, often called the parapineal gland, occurs in salamanders. In birds and mammals the parietal organ (but not the pineal gland) is absent.
Femoral pores are a part of a holocrine
secretory gland found on the inside of the thighs of certain lizards and amphisbaenians which releases pheromones to attract mates or mark territory. In certain species only the male has these pores and in other species, both sexes have them, with the males being larger.Femoral pores appear as a series of pits or holes within a row of scales on the ventral portion of the animal's thigh.
4) 순환 및 호흡계
(1) 허파호흡을 한다. 뱀류는 한 쌍의 자루 모양의 허파를 가지며, 왼쪽 허파는 퇴화되어 있으며, 오른쪽 허파가 제 역할 을 한다. 허파 벽에 폐포(alveoli)가 분포 되어 있다.
(2) 악어류를 제외하고 횡격막 (diaphragm)이 없어, 늑간근
(intercostal muscle)과 허파 벽의 평활 근(smooth muscle)의 수축 및 이완작 용으로 체내의 용적을 변화시켜 호흡을 한다.
(3) 심장은 심실이 불완전한 격막
(septum)으로 분리되어 있는 2심방 1심 실이나, 악어류의 경우 완전하게 격리되 어 있다.
Lung of reptiles
In general, reptilian lungs are very simple structures accommodating a larger tidal volume but a smaller surface for gas exchange.
The left lung is absent or vestigial in most snakes, with the exception of boids (boas and pythons).
The right lung extends caudally in snakes, becoming more of an air sac in the lower third of the body. Most reptiles do not have a functional muscular diaphragm and therefore have a combined pleuroperitoneum or coelomic cavity . The muscles of the abdomen and trunk complement the intercostal muscles to generate negative pressure, causing the lungs to expand. Activity of smooth muscles within the lung wall also helps to move air in and out of the lungs.
Turtles have a membranous separation between the lungs and remaining viscera, but do not have intercostal muscles. Turtles breathe by changing the positions of the coelomic viscera and limbs, thereby creating pressure differences within the lungs.
Crocodilians have a membranous pseudodiaphragm, which does not function as a mammalian
diaphragm does.
Lung of snake
The vestigial left lung is often small or sometimes even absent, as snakes' tubular bodies require all of their organs to be long and thin. In the majority of species, only one lung is functional. This lung contains a vascularized anterior portion and a posterior portion which does not function in gas exchange. This 'saccular lung' is used for hydrostatic purposes to adjust buoyancy in some aquatic snakes and its function remains unknown in terrestrial species.
Anatomy of a snake.
1 esophagus, 2 trachea, 3 tracheal lungs,
4 rudimentary left lung, 5 right lung, 6 heart,
7 liver, 8 stomach, 9 air sac, 10 gallbladder,
11 pancreas, 12 spleen, 13 intestine, 14 testicles,
15 kidneys.
Respiration of turtle
The rigid shell means that turtles cannot breathe as other reptiles do, by changing the volume of their chest cavity via expansion and contraction of the ribs. Instead, turtles breathe in two ways. First, they employ buccal
pumping, pulling air into their mouth then pushing it into the lungs via oscillations of the floor of the throat.
Secondly, by contracting the abdominal muscles that cover the posterior opening of the shell, the internal volume of the shell increases, drawing air into the lungs, allowing these muscles to function in much the same way as the mammalian diaphragm.
Although many turtles spend large amounts of their lives underwater, all turtles and tortoises breathe air, and must surface at regular intervals to refill their lungs. They can also spend much of their lives on dry land.
Aquatic respiration in Australian freshwater turtles is currently being studied. Some species have large cloacal cavities that are lined with many finger-like projections. These projections, called papillae, have a rich blood supply, and increase the surface area of the cloaca. The turtles can take up dissolved oxygen from the water using these papillae, in much the same way that fish use gills to respire.
(A) Illustration of the abdominal muscles and lungs of T. carolina. The paired transverse abdominis (TA) muscles wrap around the posterior portion of the lungs and produce exhalation by compressing the lungs as they contract. The cup-shaped oblique abdominis (OA) muscles actively produce inhalation as they flatten and expand the inguinal flank postero- ventero-laterally. (B) Photograph of the skeleton with limbs and neck fully extended. Because the shell contains a fixed volume, the lungs can be filled with air when the head and limbs are protracted. (C) Air can be forced out of the lungs when the limbs and head are retracted into the shell.
거북의 심장박동 (동영상 참조)
Since hearts found in lizards, snakes, and turtles have incomplete
septums, oxygenated (red) blood and deoxygenated (blue) blood may
mix to some degree. In crocodiles a complete septum and a valve
prevent this from happening.
* 악어는 어떻게 숨을 쉬지 않고 물속에서 수 시간 동안 있을 수 있나? *
Left, the crocodile heart showing where the cog teeth are located, and the direction of blood circulation.
Right, photograph taken inside the heart showing two cog teeth.
By examining the heart of a crocodile, Queensland researchers have discovered how it is that an air-breathing creature can manage to cruise through the murk, for several hours without surfacing.
The researchers report the crocodile has a unique type of valve in its heart which actively controls blood flow between the lungs and the rest of the body.
Unlike the passive flap-like valves of other vertebrates, the crocodile valve has cog teeth made up of nodules of connective tissue. The cog teeth mesh together, diverting blood away from lungs and into their bodies(먹이를 잡을 때-흥분 시). The researchers have found that these
"teeth" are controlled by the amount of adrenalin in the bloodstream.
When the crocodile is relaxed(물속에 가만히 있을 때-무호흡 시), the absence of adrenalin acts to close the cog-teeth valves," Dr Franklin said.
He said this mechanism may allow the crocodiles to dive for several hours without needing to resurface to breathe.
The valves are situated in the crocodile's right ventricle, which pumps blood to the pulmonary artery feeding the lungs as well as to the left aorta which supplies the body. The cog-teeth valve can divert blood going to the lungs back into the body, a phenomenon known as a shunt.
"In contrast, mammalian hearts are very inflexible with the blood supply to the lungs a separate activity to that feeding the body."
"Crocodiles are an endless source of fascination for people because they are one of the few animals which can still get the better of us. We now know that far from being primitive or basic, their heart is a remarkable machine," Dr Franklin said.
Heart of crocodile
The Foramen of Panizza is a hole with that connects the left and right aorta as they leave the heart of all animals of the order Crocodilia.
Crocodilians have a completely separated ventricle with deoxygenated blood from the body, or
systemic circulation, in the right ventricle and oxygenated blood from the lungs, or pulmonary circulation, in the left ventricle, as in birds and mammals. Two vessels, the left aorta and the pulmonary artery, exit the right ventricle. Blood from the right ventricle goes to the lungs through the pulmonary artery, as in mammals and birds.
However, when a unique active valve(cog teeth) leading to the pulmonary artery contracts, pressure in the right ventricle can increase and blood can leave the right ventricle, enter the left aortic arch, and therefore bypass the pulmonary circulation. The foramen of panizza connects the left and right aorta.
Deoxygenated blood from the right ventricle, sitting in the left aorta, can flow into the right aorta
through the foramen of panizza. When the heart is relaxed, some oxygenated blood from the left ventricle, sitting in the right aorta, can flow into the left aorta across the foramen of panizza. However, some species of Crocodilians have regulatory sphincters that prevent unwanted flow of blood through the foramen of panizza during non-diving.
(4) 파충류는 림프절이 없는 림프계(lymphatic system)를 가지 며, 혈액에는 헤모글로빈이 적어서 포유류보다 산소가 적게 공급 된다.
(5) 파충류는 몸의 하반부(caudal part)를 순환한 정맥혈은 신장 의 문맥계(renal portal system)를 통해 심장으로 향한다. 따라 서 전신마취 시 주의해야 한다.
(6) 변온동물(ectotherm=cold-blooded animal)로 체온을 유 지하기 위하여 태양광선과 같은 열원을 이용하며, 체온을 일정하 게 유지할 필요가 없어 극소량의 먹이로도 생명을 유지할 수 있다.
온대에서는 겨울철에 동면을 한다.
(7) 악어의 경우, 눈과 비공(nostrils)이 머리 위 쪽으로 향해 있어 물
속에 있어도 호흡하 고 볼 수가 있다.
The internal anatomy of the crocodile is shown here. Unlike most other reptiles, the heart of the crocodile is divided into two chambers as opposed to three. Blood in the veins returns to the heart from the tail and hind limbs through the kidneys (renal portal system), while blood from the abdomen returns through the liver. The crocodile has no urinary bladder.
Renal portal system of Reptiles
Hibernation
1) Occurs with exposure to low temperatures and principally during winter seasons
2) Adaptive mechanisms ; reduced body temperature, Slower heartbeat, Slower breathing rate, Slower rate of metabolism
3) The period of hibernation ; proportional to the length of the winter period 4) Utilizaton of stored food products
(1) Principal types of reserve food : lipids and glycogen
(2) The animal starch ; Less stable and more rapidly used than fats (3) Glycogen ; Generally localized in tissues such as livers and muscle
(4) Reserve foods are selectively utilized ; In hibernation turtles the tissue glycogen is used during the initial days and weeks of hibernation; later, the lipids are utilized
5) The water content of the tissues becomes reduced and the blood more concentrated. It makes lower their freezing point
6) Burrowing in crevices under rocks, logs, and in the ground below the frost line
[서울신문 나우뉴스]꽁꽁 얼어붙은 호수 위를 건너려다 그만 안타깝게도 얼어붙어 버린 개구리의 모습이 포착됐 다. 영국 일간 데일리메일 온라인판은 8일(현지시간) 최근 미국 한파 등 지구촌 곳곳에서 벌어지고 있는 기상이변 현상을 보여주기라도 하듯 최근 노르웨이 수도 오슬로 근교의 한 호수에서 찍혔다는 얼어붙어 버린 개구리 사진을 공개했다.
공개된 사진을 보면 유리처럼 맑고 투명하게 얼어붙은 호수 위에 미라처럼 말라버린 개구리가 동면이라도 하듯 눈 을 감고 있으며 그 위에는 성애가 눈꽃처럼 맺혀있다.이를 촬영한 사진작가 스베인 노드럼(54)은 "스케이트를 타 러 호수에 나왔다가 동사한 개구리를 발견했다"고 밝혔다.
이에 대해 이 매체는 이 개구리는 갑작스러운 기온 상승에 동면에서 깨어났고 짝을 찾으러 호수를 건너던 중 갑작 스 러 운 한 파 에 그 만 얼 어 붙 은 듯 보 인 다 고 설 명 했 다 .(2014.01 : 사 진 = 메 다 비 아 / 데 일 리 메 일 )
호수 건너다..지구 덮친 한파에 얼어붙은 개구리
5) 배설 및 생식계
(1) 엽상의 후신(metanephros)의 신장을 가지며, 수중생활을 하 는 파충류는 암모니아 형태로 노폐물을 배설하고, 육상생활을 하는 파충류는 요산(uric acid)으로 배설한다. 거북류와 일부 도마뱀은 짧은 요도(urethra)로 배설강에 연결된 방광을 가지고 있다.
(2) 배설강은 3부분으로 되어 있는데, 배변과 배뇨, 그리고 산란을 하는 생식기의 역할을 한다.
(3) 자웅이체이며 수컷은 교미기관(intromittent organs)을 가지고 있어 암컷의 배설강으로 삽입 하여 체내수정(internal fertilization)을 한다.
(4) 대부분 난생으로 수정 직후 산란하며, 알은 주로 땅속에 낳 는다. 도마뱀의 일부와 살모사(mamushi) 등이 태생을 하는데, 원시적인 태반(primitive placenta)이 난관에 생겨 영양과 산소 를 공급한다.
(5) 배아(embryo)는 양막
(amnion)으로 쌓여 있고, 요막 (allantois)과 융모막(chorion)을 가지며, 새끼는 완전한 형태를 가 지고 부화한다.
A critical evolutionary development for terrestrial animals was the reptilian amniotic egg, now also characteristic of birds and some mammals. The developing embryo, protected from drying out, can survive out of water and in a variety of habitats. The yolk provides it with food, and the albumen supplies water and nutrients. Wastes are released to the allantois, an extension of the embryonic gut.
Oxygen diffuses easily through the thin outer shell of the egg; its passage to the embryo is regulated by
the chorion.
Reproduction of snake
Although a wide range of reproductive modes are used by snakes, all snakes employ internal fertilization. This is accomplished by means of paired, forked hemipenes, which are stored,
inverted, in the male's tail. The hemipenes are often grooved, hooked, or spined in order to grip the walls of the female's cloaca.
Most species of snakes lay eggs, but most snakes abandon the eggs shortly after laying. However, a few species (such as the King cobra) actually construct nests and stay in the vicinity of the
hatchlings after incubation. Most pythons coil around their egg-clutches and remain with them until they hatch. A female python will not leave the eggs, except to occasionally bask in the sun or drink water. She will even “shiver” to generate heat to incubate the eggs.
Some species of snake are ovoviviparous and retain the eggs within their bodies until they are almost ready to hatch. Recently, it has been confirmed that several species of snake are fully viviparous, such as the boa constrictor and green anaconda, nourishing their young through a placenta as well as a yolk sac, which is highly unusual among reptiles, or anything else outside of placental mammals. Retention of eggs and live birth are most often associated with colder
environments, as the retention of the young within the female.
Temperature-dependent sex determination (TDSD) in reptiles
Some reptiles exhibit temperature-dependent sex determination (TDSD), in which the incubation temperature determines whether a particular egg hatches as male or female. TDSD is most common in turtles and crocodiles, but also occurs in lizards and tuataras. To date, there has been no confirmation of whether TDSD occurs in snakes.
In turtles with TSD, males are generally produced at lower incubation temperatures than females (TSD IA), with this change occurring over a range of temperatures as little as 1-2 °C. At cooler temperatures ranging between 22.5 and 27 degrees Celsius mostly male turtles arise, and at warmer temperatures around 30 degrees Celsius only female turtles arise. In lizards and crocodilians, this pattern is reversed (TSD IB).
Synergism between temperature and hormones has also been identified in these systems.
Administering estradiol at male-producing temperatures generates females that are physiologically identical to temperature-produced females. The reverse experiment, males produced at female temperatures, only occurs when a nonaromatizable testosterone or an aromatase inhibitor is administered, indicating that the enzyme responsible for
conversion of testosterone to estradiol, aromatase, plays a role in female development.
Interestingly, hormones and temperature show signs of
acting in the same pathway, in that less hormone is
required to produce a sexual shift as the incubation
conditions near the pivotal temperature.
6) 신경계 및 감각기관
(1) 파충류의 뇌는 포유류에 비해 훨씬 작다.
(2) 대개 둥근 동공(pupil)을 갖지만, 일부는 수직 또 는 수평으로 갈라진 동공을 가지고 있다.
(3) 도마뱀과 거북, 그리고 악어는 움직이는 눈꺼풀 (functional eyelids) 가지나, 뱀류는 눈꺼풀 대신에 투명한 비늘(spectacle)로 덮여 있다.
(4) 뱀은 외이(external ear), 중이(middle ear cavity), 고막(tympanic membrane), 그리고 이관 (Eustachian tube)이 없어, 땅의 진동을 몸을 통해 내 이로 감지해 소리를 듣는다.
(5) 도마뱀과 뱀류에서는 코 안쪽과 입천장에 야콥손기관
(Jacobson's organ= vomeronasal organ)이 있어, 먹이를 찾는 데 혀를 통해 화학물질을 전달해 후각을 감지한다.
(6) 반면에 밤에 활동하는 독사나 비단구렁 이의 경우, 머리 부분에 특별한 열감지기관 (pit organ)을 가지고 있어 먹이를 찾는다.
The Jacobson's organ in snakes is used with the tongue to detect odors.
The snake flicks out its tongue and picks up scent particles. When the snake pulls in its tongue, the particles are transferred to the odor- sensitive Jacobson's organ.
Pit organ(heat-sensitive organ)
Two families of snakes, pit vipers and boids, possess an infrared (IR) sensitive sensory system that is used to construct a two-dimensional representation of the heat distribution in their environment. In the case of the pit viper, the sensory organ consists of two cavities (pit holes) lying closely to the eyes at the sides of the head. Inside this cavity a freely suspended membrane is contained.
The membrane is very thin (15 micrometer) and contains heat-sensitive cells that can detect temperature differences down to a few mK. Still, the opening of the pit hole must be large, to be able to quickly detect moving prey. Therefore, the optical quality of the organ as "measurement device" is very poor. Nontheless, the snake is able to precisely strike prey using the heavily blurred heat image on the
pit membrane. This paradox has been resolved. The ability to sense infrared thermal radiation evolved independently in several different families of snakes. Essentially, it allows these animals to “see” radiant heat at wavelengths between 5 and 30 μm to a degree of accuracy such that a blind rattlesnake can target vulnerable body parts of the prey at which it strikes. It was previously thought that the organs evolved primarily as prey detectors, but recent evidence suggests that it may also be used in thermoregulation and predator detection, making it a more general-purpose sensory organ than was supposed.
* Caudal autotomy in lizard
Geckos, skinks, and other lizards, and some salamanders that are captured by the tail will shed part of the tail structure and thus be able to flee. The detached tail will continue to wiggle, creating a deceptive sense of continued struggle and distracting the predator's attention from the fleeing prey animal.
The animal can partially regenerate its tail over a period of weeks. The new section will contain cartilage rather than bone, and the skin may be distinctly discolored compared to the rest of the body. The technical term for this ability to drop the tail is caudal autotomy.
Autotomy in lizards is enabled by special zones of weakness at regular intervals in the vertebrae posterior to the vent.
Essentially, the lizard contracts a muscle to fracture a vertebra rather than break t h e t a i l b e t w e e n t w o v e r t e b r a e . Sphincter muscles in the tail then contract around the caudal artery to minimize bleeding.
스파게티와 같은 굵기, 최고 작은 뱀 발견
해외 언론들은 평균 10센티미터이고 스파게티 국수만큼 가는 세상에서 가장 작은 뱀이 바베이도 스 카리브해의 작은 섬에서 발견되었다고 전했다.
거의 사라져가는 숲의 일부 지역의 돌 밑에서 발견된 이 뱀은 뱀이 얼마나 작게 진화할 수 있는지 의 한계를 보여주는 것이라고 생각된다. 암컷은 오직 하나의 알을 낳지만 부화된 것은 어른의 몸 무게의 절반을 이를 정도로 알이
크다.
레프토타이프로프스 카레라는 학
명을 가진 이 뱀은 3100종의 뱀
중에서 가장 작은 것이고 미국의
펜실베니아 주립대학의 생물학자
인 헤지박사와 그의 아내에 의해
서 발견되었다. (사진 오른쪽은
헤지 박사가 제공한 것으로, 가장
작은 파충류의 모습이다)
MBD (metabolic bone disease) of green iguana
세인트 루이스월드 아쿼리엄이 1만5천달러에 사들여 인터넷 경매 이베이로 15만
달러부터 호가하게 될 머리 2개의 알비노래트 뱀(siamese twins)을 이 아쿼리
엄의 레오나드 조넨샤인회장이 손에 쥐고있다. /AP 연합
희귀종 알비노 악어인 화이트다이아몬드(white diamond)
왕도마뱀의 부검
Pterosaur(익룡)
