Archived from the original on September 17, In some reptiles, a midventral wall in the cloaca may open into a urinary bladder, but not all. Archived from the original on 26 July History of "Reptile" Note: Even though the optimum temperature for rattlesnakes is around 77 o to 89 o F 25 o to 32 o C , the greatest period of activity is spring, when they come out of hibernation and are seeking food. Land-dwelling reptiles, such as snakes and lizards, excrete nitrogenous wastes in pasty or dry form as crystals of uric acid Towle
The use of the gizzard system has the potential advantages that intake rate is not limited by chewing, that no investment in dental tissue is necessary, and that dental wear is not a determinant of senescence as observed in mammals. The absence of age-dependent tooth wear might even be a contributing factor to the slower onset of senescence in birds as compared to mammals.
On the other hand, the use of a gizzard requires the intake of suitable grit or stones—an action that represents, in the few studies where this has actually been quantified in birds, a relevant proportion of feeding time Fritz et al. Gastrointestinal tracts of a carnivorous hawk, an omnivorous chicken, and 4 herbivorous birds. Note larger size of crop in omnivore and herbivores, and particularly in hoatzin. Ceca are small in hawks and relatively large in grouse. Although ceca are relatively small in Hoatzins , Emus, and Ostriches, an expanded foregut Hoatzins , a much longer midgut Emus , or a much longer colon Ostriches compensates for this From: Stevens and Hume Over-reliance on the passive pathway provides metabolic advantages and ecological constraints.
It does provide birds with an absorptive process that can deal with rapid and large changes in intestinal sugar concentrations. The passive pathway is also energetically inexpensive to maintain and modulate.
However, passive absorption through the paracellular pathway is dependent on concentration gradients. In the absence of a transport system that selects which materials to absorb, this non-discriminatory pathway may also increase vulnerability to toxins, and thus constrain foraging behavior and limit the breadth of the dietary niche of the birds.
Another problem is that when luminal sugar concentrations are lower than those in plasma, glucose may diffuse back into the lumen. Cross-section of the intestine ileum of a Spotted Tinamou Nothura maculosa.
Villi are lined with columnar epithelium EP , including goblet cells arrows that secrete mucus. The muscle layer includes longitudinal fibers MI on the perimeter, circular fibers Mc , and additional longitudinal fibers at the base of the villi muscularis muscosae; MM From: Chikilian and de Speroni Blue-headed Parrots at clay lick.
Meyer-Rochow and Gal determined that the pressures involved could be approximated if they knew the 1 distance the feces traveled, 2 density and viscosity of the material, and 3 shape, aperture, and height of the anus above ground. How penguins choose the direction of defecation, and how wind direction factors into that decision, remain unknown.
Avian Pancreas tissue Source: The Avian Digestive Tract. Avian geophagy and soil characteristics in southeastern Peru. Luminal morphology of the avian lower intestine: Histological aspects of the stomach proventriculus and gizzard of the Red-capped Cardinal Paroaria gularis gularis. Comparative study of the digestive system of three species of tinamou. Crypturellus tataupa, Nothoprocta cinerascens , and Nothura maculosa Aves: Journal of Morphology Journal of Experimental Zoology Rictal bristle function in Willow Flycatcher.
Dysplastic koilin causing proventricular obstruction in an Eclectus Parrot Eclectus roratus. Journal of Avian Medicine and Surgery Anatomy and physiology of the digestive system in fowl. Pages in Proc. An histological and histochemical analysis of the inner lining and glandular epithelium of the chicken gizzard. American Journal of Anatomy An ecomorphological study of the raptorial digital tendon locking mechanism. Dietary and developmental regulation of intestinal sugar transport.
Digesta retention patterns in geese Anser anser and turkeys Meleagris gallopavo and deduced function of avian caeca. Comparative Biochemistry and Physiology A Histological and global gene expression analysis of the 'lactating' pigeon crop.
Vultures of the seas: Evolution of the structure and function of the vertebrate tongue. Journal of Anatomy Light and scanning electron microscopic study of the tongue in the cormorant Phalacrocorax carbo Phalacrocoracidae, Aves. Functional morphology of the tongue in the nutcracker Nucifraga caryocatactes. A tropical horde of counterfeit predator eyes. Instructed learning in the auditory localization pathway of the Barn Owl. The morphology of the bill apparatus in the Steller's Sea Eagle.
Wild Bird Society of Japan, Tokyo. Use of dung as a tool by burrowing owls. The integration of energy and nitrogen balance in the hummingbird Sephanoides sephaniodes. Does gut function limit hummingbird food intake? Physiological and Biochemical Zoology Pressures produced when penguins pooh—calculations on avian defaecation.
Scare tactics in a neotropical warbler: Gliding flight and soaring. Theoretical Ecology Series, vol. Modelling the flying bird C. Structure, form, and function of flight in engineering and the living world. Phenotypic flexibility and the evolution of organismal design. Trends in Ecology and Evolution The hummingbird tongue is a fluid trap, not a capillary tube.
Between air and water: Use of prey hotspots by an avian predator: Structure and mechanical behavior of a toucan beak. Movement and direction of movement of a simulated prey affect the success rate in Barn Owl Tyto alba attack. Musculoskeletal underpinnings to differences in killing behavior between North American accipiters Falconiformes: Accipitridae and falcons Falconidae. Journal of Morphology, online early. Le Bohec, and Y. Adjustments of gastric pH, motility and temperature during long-term preservation of stomach contents in free-ranging incubating King Penguins.
Journal of Experimental Biology A tough nut to crack. Adaptations to seed cracking in finches. Cost-benefit analysis of mollusc-eating in a shorebird. Optimizing gizzard size in the face of seasonal demands. How do woodpeckers extract grubs with their tongues? Why do woodpeckers resist head impact injury: Functional morphology of raptor hindlimbs: The turning- and linear-maneuvering performance of birds: Canadian Journal of Zoology Hummingbird jaw bends to aid insect capture.
A mechanical analysis of woodpecker drumming and its application to shock-absorbing systems. I - Introduction to Birds. VII - Circulatory System. Back to Avian Biology. Drawings of the digestive tracts of A a Greylag Goose and B a Wild Turkey and retention times of a solute, 2-mm particles, and 8-mm particles in the goose and turkey digestive systems Figure from Frei et al.
The closed, air-filled spaces reduce overall weight without loss of rigidity. The capillary ratchet mechanism Surface tension transport of prey by feeding shorebirds: The serrated leading-edge feather of an owl Norberg Vortex generators on an airplane wing.
Fish-eating species like cormorants below - typically have small, undifferentiated tongue because fish are often swallowed whole. Representative caterpillar false eyes and faces. In some, like woodpeckers, the 'sticky' saliva aids in capturing prey. In others, like swifts, saliva is used in nest building see photo below. The muscular walls of the esophagus produce wave-like contractions peristalsis that help propel food from the oral cavity to the stomach.
Anhinga swallowing a large fish. HCL and pepsinogen are secreted by the deep glands see photomicrograph below. Pepsinogen is converted into pepsin a proteolytic, or protein-digesting, enzyme by the HCl. The cuticle is secreted by simple tubular glands see photomicrograph below.
Grinding action may, particularly in seed-eating birds, be assisted by grit and stones deliberately ingested. The avian gastrointestinal tract, unlike that of mammals, executes distinct reverse peristaltic movements that are critical to optimal digestive function Duke The gastric reflux allows material in the gizzard to reenter the proventriculus for additional treatment with acid and pepsin.
Villi are projections from the intestinal wall that increase the amount of surface area available for absorption. Further increasing the surface area are the numerous microvilli of the cells lining the surface of the villi. Inside each villus are blood vessels that absorb nutrients for transport throughout the body. Caeca are histologically similar to the small and large intestines and found in a wide variety of birds.
In these large ceca, food particles are acted upon by cecal secretions, bacteria, and fungi and nutrients can be absorbed. Lymphoid ceca are not important in digestion but contain lymphocytes white blood cells that produce antibodies Clench At various times and under various conditions, ceca are the site for 1 fermentation and further digestion of food especially for the breakdown of cellulose and absorption of nutrients, 2 production of antibodies, and 3 the use and absorption of water and nitrogenous components Clench The bursa is most prominent in young birds and serves as the area where B-lymphocytes the white blood cells that produce antibodies are generated T-lymphocytes are generated in the Thymus.
Bile emulsifies fats or, in other words, breaks fats down into tiny particles. Emulsification is important because it physically breaks down fats into particles than can then be more easily digested by enzymes lipase produced by intestinal cells and the pancreas.
This 'juice' contains a bicarbonate solution that helps neutralize the acids coming into the intestine from the stomach plus a variety of digestive enzymes. The enzymes help break down fats, proteins, and carbohydrates. The pancreas also produces the hormones insulin and glucagon which regulate blood sugar levels cells that produce these two hormones make up the 'islets of Langerhans', one of which is represented by the light-colored, circular structure in the photomicrograph below.
Hit 'Reload' or 'Refresh' to View Again! Particle retention time hr. Flamingos use a series of projections, or lamellae, to filter tiny food items from debris in the water.
Wrens use their thin, probing bill to capture small insects. Curlews use their long bill to probe mudflats for small invertebrates. Finches do not simply bite the seeds; instead; the lower mandible is moved toward the tip of the bill in a slicing motion.
When most of the coat has been cracked or removed, the lower mandible is moved from side to side to remove the rest of the shell, thus releasing the kernel. Some large finches also have raised hard surfaces in the upper palate that function as anvils so large seeds can be held firmly while the lower mandible slices and cracks the sides of the seed. As tricky as nutcracking sounds, most birds accomplish it rapidly, shelling small seeds in a few seconds and large finches can crack open and devour a large seed or nut in less than twenty seconds.
Big mouths get hummingbirds an in-flight meal - Hummingbirds have bendy lower beaks to help them catch insects Yanega and Rubega The flexibility allows long-beaked birds to open their mouths wide enough to hunt on the wing. Hummingbirds use their long, narrow beaks to probe flowers for nectar, but they also need insects for essential nutrients. It wasn't clear how they could catch them; birds that hunt flying insects usually have short beaks to help them open their mouths wide. Pilcher, Nature Science Update.
The force produced by talons may be related to time of activity. Owls hunt when light levels are low so if an attacking owl misses its prey, relocating it may be difficult. Hawks are diurnal hunters and can use visual cues during and after an attack. If unable to subdue prey initially, they can relocate prey visually and catch it. La mayoría de las serpientes se reproducen poniendo huevos , pero algunas especies han desarrollado un método diferente.
En algunos casos el grupo entero alumbra crías totalmente formadas, mientras que otros grupos pueden estar formados tanto por miembros que alumbran crías formadas, como por miembros que ponen huevos. Por ejemplo, dentro de la familia Boidae todas las boas paren animales ya formados, mientras que las pitones ponen huevos.
Sin embargo, si la presa opone resistencia, pueden recurrir a técnicas como son el uso del veneno o la constricción para abatir la presa antes de comérsela. Las serpientes no pueden masticar el alimento, y en su lugar se las tragan enteras. Los dientes de una serpiente, que son afilados como agujas y dirigidos hacia el interior de la boca, sirven para retener la presa a que se le salga de su boca.
Otra razón de su capacidad para tragar es la carencia de huesos como el esternón para que la comida pueda pasar sin problemas por el esófago y por todo el cuerpo del reptil. Después de la ingestión , una serpiente debe aletargar para cumplir el proceso de la digestión.
En ese estado, algunos órganos como el corazón y el estómago entran en mayor actividad para que toda la comida sea casi totalmente digerida. Las partes indigeribles pueden ser excretadas o regurgitadas. Las serpientes presentan una radiación adaptativa casi tan amplia como los lagartos , aunque la variación estructural no es tan grande. Todas las serpientes venenosas australianas pertenecen a este grupo.
Las serpientes de coral poseen sus vivos colores de advertencia ya que son muy venenosas aposematismo , entre los que predominan amarillo, rojo y negro; no son muy peligrosas para el hombre ya que son de pequeño tamaño y abren poco la boca, lo que hace difícil que puedan morder.
El veneno tiene una acción principalmente hemolítica. La cabeza es triangular y ancha, y los ojos tienen la pupila vertical. La mayoría retienen los huevos que contienen a las crías en el interior del cuerpo alumbrando a las crías tras la eclosión de los huevos desde el interior del cuerpo, es decir, son ovovivíparas. Todas las serpientes pertenecen al clado Serpentes, que a su vez es miembro del orden Squamata.
El suborden Serpientes se subdivide en dos infraórdenes y 25 familias: Recientes estudios moleculares corroboran la monofilia del clado Serpentes y de los infraórdenes Scolecophidia y Alethinophidia.
Este relato bíblico ha inspirado a la Iglesia católica a representar la Virgen María como la Inmaculada Concepción pisando a una serpiente tal como relata el génesis, pero el reptil en vez de morderle el talón solo lleva una manzana en su boca.
En algunos casos también se han representado a Jesucristo pisando una serpiente, pero no inspirado en el génesis de la Biblia sino como una representación de lucha entre el bien y del mal , lo cual esta simbología también puede aplicarse al caso de la Virgen María.
De acuerdo a esta historia, se interpreta que Dios a través de Moisés demostraba su furia contra el pueblo egipcio frente al Faraón. En esto algunos teólogos consideran que el bastón de Moisés, conocido como la vara de Moisés , es una serpiente de aspecto positivo o a la vez milagroso. Representaba la fuerza del crecimiento, la fertilidad del suelo y de las aguas en la mitología egipcia.
Era la diosa protectora del Bajo Egipto y del faraón. Sin embargo, la serpiente Apofis eran el símbolo de las fuerzas maléficas que habitan el Duat , e intentaba retener la barca solar de Ra.
En el Próximo Oriente Antiguo se consideraba a la serpiente un animal de vida larga, benefactor y sanador, de ahí el emblema del caduceo. The other stomach has the most acidic digestive system of any animal, and it can digest mostly everything from their prey; bones, feathers, and horns. Reptiles have an advanced nervous system compared to amphibians. They have twelve pairs of cranial nerves. The brain is relatively small. The tongue of a snake includes highly sensitive smell sensors. Some researchers speculate that the forked nature of the tongue may offer a stereo sense of smell.
Crocodilians see well in daylight and may even have color vision; additionally, their vertical, cat-like pupil gives them excellent night vision. In crocodilians, the upper and lower jaws also are covered with sensory pits, the crocodile version of the lateral line sensory organ found in fish and many amphibians. These pigmented nodules encase bundles of nerve fibers that respond to the slightest disturbance in surface water, detecting vibrations and small pressure changes in water, making it possible for them to detect prey, danger, and intruders even in total darkness.
While alligators and caimans have the sensory nodules only on their jaws, crocodiles have similar organs on almost every scale on their body. Most reptiles reproduce sexually. This includes many male snakes that rely on scent to find females and that complete fertilization internally. Most reptile species are oviparous egg-laying.
Many species of squamates, however, are capable of giving live birth. This is achieved either through ovoviviparity egg retention or viviparity babies born without use of calcified eggs. Many of the viviparous species feed their fetuses through various forms of placenta, just like mammals Pianka and Vitt They often provide considerable initial care for their hatchlings.
Amniotic eggs are covered with leathery or calcareous shells and are compartmentalized by four membranes: Eggs are waterproof, but permeable to gases. Sperm are placed inside the female by internal fertilization prior to the formation of the shell. In addition to the common pattern of sexual reproduction among reptiles, a pattern of asexual reproduction has been identified in six families of lizards and one snake family.
In some species of squamates lizards and snakes , a population of females is able to produce a unisexual diploid clone of the mother. This asexual reproduction, called parthenogenesis , occurs in several species of gecko and is particularly widespread in the teiids especially Aspidocelis and lacertids Lacerta.
Parthenogenetic species are also suspected to occur among chameleons , agamids, xantusiids, and typhlopids. Reptiles offer economic, ecological, aesthetic, and symbolic value to humans. Some species, such as the green turtle, the iguana, and some snakes, are part of the diet, and the giant Galapagos tortoise was so popular as a food among sailors in the nineteenth century that it was nearly exterminated.
The skins of crocodilians, snakes , and lizards have been used in leather goods, such as shoes, handbags, gloves, and belts, but international agreements protecting endangered species have prompted a shift of reptile skin sources from hunters of wild species to farmers growing reptiles in captivity. Reptiles also are very popular pets. In the United States , about 3 percent of households have reptiles as pets with many of the reptiles having been imported into the country either legally or illegally as part of the international trade in live exotic animals.
Ecologically , reptiles are a critical element in the food chains of most ecosystems, and sometimes a keystone species whose removal can drastically alter the populations of other organisms. The consumption by reptiles of rodents and insect pests aids in control of these animals, which can be serious agricultural pests. Aesthetically, many reptiles can be considered beautiful or awe-inspiring, such as the San Francisco garter snake Thamnophis sirtalis tetrataenia , with its bright orange head, black and red stripes, and turquoise belly, and the chameleons with their color changes.
Reptiles appear in designs on apparel and other consumer goods because of their appeal. Symbolically, reptiles appear in literature and religion in a variety of ways.
Perhaps the most famous reference is the Bible reference to the serpent in the Garden of Eden, or Jesus advising his disciples to be "wise as serpents. Some reptiles also present threats to people, whether because they are venomous, like some snakes, or can attack humans, such as some crocodilians. In addition, salmonella, a bacterial disease, is sometimes picked up from a reptile's skin when touching a reptile kept as a pet. Hylonomus, the oldest-known reptile, was about 8 to 12 inches 20 to 30 cm long.
Westlothiana, also suggested as the oldest reptile, is for the moment considered to be related more to amphibians than to amniotes. Other examples of fossil animals considered to be ancient reptiles are those of the genera Petrolacosaurus, Araeoscelis, Paleothyris, Ophiacodontidae, Archaeothyris, and Ophiacodon, and also the family of mesosaurs.
The first true "reptiles" or amniotes are categorized as Anapsids Anapsida , which are vertebrates characterized by solid skulls with the conventional openings for nose, eyes, spinal cord, and so forth, but lacking temporal fenestrae jaw muscle attachment sites at holes in the sides of the skull behind the eyes near the temples.
Turtles are believed by some to be surviving anapsids, indeed the only surviving anapsids, as they also share this skull structure. However, this point has become contentious, with some arguing that turtles reverted to this primitive state in the process of improving their armor.
Both sides have marshaled evidence, and the conflict has yet to be resolved. Shortly after the appearance in the fossil record of the first reptiles, a second branch appeared.
The original branch led to the Anapsida, which did not develop the jaw muscle attachment holes in their skulls, and the second led to the Diapsida diapsids , which developed two pairs of jaw muscle attachment holes in their skulls behind the eye holes. Diapsids "two arches" are a group of tetrapod animals that appeared in the fossil record about million years ago during the late Carboniferous period. Living diapsids are extremely diverse, and are considered to include all birds , crocodiles, lizards, snakes, and tuataras and possibly even turtles.
While some lost either one hole lizards , or both holes snakes , they are still classified as diapsids based on their assumed ancestry. During the Permian period million years ago , the Diapsida line of descent split into two lineages: The lepidosaurs modern snakes, lizards, and tuataras, as well as, debatably, the extinct sea reptiles of the Mesozoic era and the archosaurs living crocodilians and birds as well as the extinct pterosaurs and dinosaurs.
The earliest solid-skulled amniotes in addition to giving rise to the anapsids, are also considered to have given rise about million years ago to a separate line, the Synapsida synapsids , which have a pair of holes in their skulls behind and above the eyes; this feature has the advantage of lightening the skull and increasing the space for jaw muscles. The synapsids eventually evolved into mammals and the early synapsids have been referred to as mammal-like reptiles by some specialists, while others argue that even the early synapsids were no longer reptiles.
As noted above, from the classical standpoint, reptiles included all the amniotes except birds and mammals. Thus, reptiles were defined as the set of animals that includes crocodiles , alligators , tuatara, lizards , snakes , amphisbaenians , and turtles , grouped together as the class Reptilia Latin repere, "to creep". This is still the usual definition of the term. However, in recent years, many taxonomists have begun to insist that for clear identification of the ancestor-descendant relations of all organisms each defined taxon should be monophyletic, that is, each taxon should include all the descendants from the originating stock.
The reptiles as defined are clearly not monophyletic but rather are paraphyletic , since they exclude both birds and mammals, although these also are considered to be descendant from the original reptile.