Reptiles 2014-2015

Class Reptilia

General Characteristics of Reptiles Reptiles are ectothermic, tetrapod vertebrates They all possess dry, scaly skin Respiration is by lungs only Reptiles have a complete or partial 3-4 chambered heart The skeleton is bony with limbs that lift the body off the ground (except snakes) – limbs are usually paired with 5 digits (pentadactyl)

General Characteristics of Reptiles (con’t) Reptiles are dioecious and fertilization is always internal No larval stage The great majority of reptiles are carnivorous although certain turtles & lizards are omnivores or herbivores Found in many kinds of habitats, from freshwater, salt water, to the driest of deserts. The chief factor that limits their distribution is temperature

Class Reptilia Approximately 7000 living species (300 in the US) There are 4 living orders of reptiles and 15 extinct orders (dinosaurs)

Characteristics that distinguish reptiles from amphibians Reptiles have tough, dry skin that offers protection against desiccation that is shed periodically

Characteristics that distinguish reptiles from amphibians The shelled (Amniotic) egg of reptiles contains food and protective membrane for embryonic development

Characteristics that distinguish reptiles from amphibians Reptilian jaws are designed for applying force to grip or crush prey. Jaw muscles are much larger & longer

Characteristics All reptiles have some form of copulatory organ for internal fertilization. This is a requirement of a shelled egg because the sperm must reach the egg before it is enclosed in a leathery covering

Characteristics that distinguish reptiles from amphibians Reptiles have a more efficient circulatory system and higher blood pressure than amphibians Reptile lungs are better developed than amphibians. Reptiles depend on lung respiration exclusively and skin breathing has been abandoned.

Characteristics that distinguish reptiles from amphibians Reptiles have evolved efficient strategies for water conservation. Nitrogenous wastes from the kidneys are excreted as uric acid crystals Instead of urea or ammonia, so the urine of most reptiles as a semi-solid paste Uric Acid Crystals

Characteristics that distinguish reptiles from amphibians Reptiles have better body support and more efficiently designed limbs for travel on land

Characteristics that distinguish reptiles from amphibians Reptilian nervous system is much more complex than amphibians. Increased size of the cerebral cortex allows for higher levels of thinking.

Order Testudine (meaning a tortoise) approximately 330 species little changed in 200 million years; dinosaur turtle called Archelon

General Characteristics Enclosed in a shell consisting of a dorsal carapace (ribs & vertebrae) and a ventral plastron (sternum) The shell is composed of an outer horned layer of keratin and an inner layer of bone Turtles have a poor hearing but a good sense of smell, acute vision and color perception as good as a human Turtles vary widely in size with the largest weighing 900 kg. and because of their low metabolism they can live more than 120 years Turtles lack teeth but have horned beak for gripping and tearing food

Reproduction Turtles are oviparous with internal fertilization Amniotic eggs are buried in the ground. In most turtle species, temperature determines the sex of the hatchlings – low temperature produces males and higher temperature produces females. All temperature-dependent reptiles lack sex chromosomes

Size & Age The giant marine turtles may reach 2 meters in length and 725 kg in weight Low metabolic activity may explain their longevity, believed to exceed 150-200 years. Even the common Box Turtles live over 30-40 years

Order Squamata Order Squamata (means Scaly) examples are snakes & lizards Largest group – 95% of known living species 2 main suborders: Lizards & Snakes

Order Squamata Suborder Lacertilia (lizards) – 3300 Species Examples are geckos, iguanas, skinks, chameleons & monitors General characteristics Have moveable eyelids Teeth present in some species Scales or epidermal plates Secrete a highly crystallized uric acid to conserve water Lizards may deliberately cast off their tails to avoid capture, this adaptation is called autotomy Lizards store fat in their tail to survive drought

Order Squamata Suborder Lacertilia (lizards) – 3300 Species Examples are geckos, iguanas, skinks, chameleons & monitors 2 Poisonous species in North America Gila Monster which is found in the SW area of USA Beaded Lizard which is found in Mexico Poison is secreted by the lower jaw; lizards do not have fangs These species are not lethal to humans Gila Monster Beaded Lizard

Order Squamata Suborder Lacertilia (lizards) – 3300 Species Examples are geckos, iguanas, skinks, chameleons & monitors Body Size Largest is the monitors with the Komodo dragon growing to 12 feet in length Smallest are the chameleons of Europe @ 4 cm in length

Order Squamata Suborder Lacertilia (lizards) – 3300 Species Examples are geckos, iguanas, skinks, chameleons & monitors Other species include – Iguanas – this group includes the common green iguana, the horned toad which used to be common in Oklahoma and now is considered endangered; Marine Iguanas of the Galapagos Islands which have developed oceanic feeding behaviors Chameleons – have distinctive adaptive behavior to color change due to chromatophore cells in the skin

Order Squamata Suborder Lacertilia (lizards) – 3300 Species Examples are geckos, iguanas, skinks, chameleons & monitors Other species include – Skinks – 14 species live in the USA. Have flat overlapping scales that give a shiny, smooth appearance Geckos – small agile and nocturnal with adhesive toe pads that allow them to walk on ceilings Blue Tailed Skink

Order Squamata Suborder – Serpentes ( to creep ) – snakes 2300 species, most widespread of all reptiles General characteristics of snakes – Snakes are entirely limbless Skull is highly kinetic which enables them to eat prey several times their own diameter. The lower jaw is loosely hinged and the 2 sides of the mandible are only connected by muscle and skin

Order Squamata Suborder – Serpentes ( to creep ) – snakes 2300 species, most widespread of all reptiles General characteristics of snakes – The opening (trachea) to the respiratory system is positioned far forward between the mandibles so that the snake can breath while swallowing large prey

Order Squamata Suborder – Serpentes ( to creep ) – snakes 2300 species, most widespread of all reptiles General characteristics of snakes – The cornea of a snake’s eye is covered by a transparent mambrane called the spectacle

Order Squamata Suborder – Serpentes ( to creep ) – snakes 2300 species, most widespread of all reptiles General characteristics of snakes – Snakes have a special sense organ called Jacobsen’s Organ which are pits in the roof of the mouth, the tips of the forked tongue fit into these pits and the scent information is transmitted to the brain

Snake Movements – 4 types Lateral undulation –s-shaped – pushes against rough ground or water Concertina – accordion pleats – folds body & thrusts head forward Rectilinear – Straight ahead – head lifted – muscle contracts thrusting the head forward (example – Boas) Sidewinding – sideways looping used by desert vipers – only 2 parts of the body in contact with hot sand at any time See Page 559 – Figure 26-21

Snake Movements http://animal.discovery.com/videos/whats-to-love-sidewinder-snake.html (Sidewinder) http://www.bing.com/videos/search?q=rectilinear+snake+motion&view=detail&mid=B 2A5685F9E484BC44F36B2A5685F9E484BC44F36&first=0&adlt=strict (Rectilinear)

Snakes kill their prey by a variety of methods Non venomous snakes use suffocation to subdue prey The Boas and Pythons use this method Other non venomous snakes that eat specific prey may just bite and swallow; snakes such as bull snakes use this method Venomous snakes use one of two types of toxins Neurotoxin acts mainly on the nervous system and paralysis results, shutting down the respiration or heart beat Hemotoxins break down red blood cells and vessels and result in extensive hemorrhaging of blood into the tissues

Poisonous snakes are divided into four families (based on fang type) Family Viperidae have highly developed retractable fangs at the front of their mouth. This group includes the pit vipers which have heat seeking pits on the front of the rostrum Examples – rattlesnakes, copperhead, and water moccasin

Poisonous snakes are divided into four families (based on fang type) Family Elapidae have short permanently erect fans and inject poison by repeated bites Examples are: coral snakes, cobras, black mamba

Poisonous snakes are divided into four families (based on fang type) Family Hydrophiladae are the most high poisonous of all snakes Example: sea krait

Poisonous snakes are divided into four families (based on fang type) Family Colubridae; this is a very large group and includes most of the non-poisonous snakes but there are 2 deadly snakes in this group and they are rear fanged snakes that use their poison to quiet struggling prey Examples: African boom-slang & twig snake

Antidote for snake bite is called antivenin Produced by antibodies in the blood from snake bitten or venom injected horses Antibodies must be specific for the snake bite The total human death toll from snakebite is about 25,000 each year The toxicity of a venom is measured by the median lethal dose on laboratory animals, according to this standard, the sea snakes and the venom of the Australian tiger snake appear to be the most deadly but there are more dangerous snakes because of their aggressiveness such as the king cobra (exceeds 5.5 m in lenth) these snakes cause more than 9,000 deaths each year

Collection of Snake Venon http://www.bing.com/videos/search?q=collecting+snake+venom &view=detail&mid=AB3A2A77F7362195ED9FAB3A2A77F736219 5ED9F&first=0&adlt=strict

Reproduction – Most snakes are oviparous The pit vipers are ovoviviparous ( this includes all poisonous American snakes) The sea snakes are viviparous – live / placental young

Order Rhynocephalia (2 living species) the common name is Tuatara Slow growing animals with a very long life (Over 80 years) Many features identical to Mesozoic fossils that are 200 million years old Has a 3rd eye (pineal eye) with cornea, lens and retina – the function of this 3rd eye is unknown

Order Rhynocephalia (2 living species) the common name is Tuatara Still called by its dinosaur name sphenodon; this animal shows the slowest rate of evolution known among the vertebrates Has no eyelids Has hooks on its ribs like birds Males have 2 penises

Order Crocodilia (crocodiles & alligators 25 species Have remained virtually unchanged for millions of years There are 3 distinct groups Crocodiles Alligators And the Gavials – found in India Have a complete secondary palate that allows them to breathe while swallowing food Alligators are much less aggressive than crocs. The Nile crocodile can grow to over 4000 lbs. and have been known to kill cattle. They are oviparous and the sex of the offspring is temperature- dependent. High nest temperatures produce males and low nest temperatures produce females and this can result in females outnumbering males 5 to 1

Comparison of Crocodiles & Alligators Narrow Head Broad Head Pointed Snout Rounded Snout Visible Teeth when mouth is closed Hidden Teeth when mouth is closed More Aggressive Less Aggressive