57-634: An egg is an organic vessel in which an embryo begins to develop. Egg , EGG or eggs may also refer to: Egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote ) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the animal hatches. Most arthropods , vertebrates (excluding live-bearing mammals ), and mollusks lay eggs, although some, such as scorpions , do not. Reptile eggs, bird eggs , and monotreme eggs are laid out of water and are surrounded by
114-405: A dry period, these frogs tuck their ventral areas under them so that only their resistant skin is exposed. They also secrete a water-resistant mucus to seal any small gaps when they aestivate . If disturbed and forced to move, they lose a significant amount of water and may not be able to survive the rest of the dry season. They are also able to lose up to sixty percent of their body weight over
171-542: A green or blue ground colour, while protoporphyrin IX produces reds and browns as a ground colour or as spotting. Non-passerines typically have white eggs, except in some ground-nesting groups such as the Charadriiformes , sandgrouse and nightjars , where camouflage is necessary, and some parasitic cuckoos which have to match the passerine host's egg. Most passerines, in contrast, lay coloured eggs, even if there
228-436: A longer fetal development. Comparatively anatomically simple animals will be able to go through the full development and leave the egg in a form reminiscent of the adult animal. This is the situation found in hagfish and some snails . Animals with smaller size eggs or more advanced anatomy will still have a distinct larval stage, though the larva will be basically similar to the adult animal, as in lampreys , coelacanth and
285-403: A naked egg cell. Mesolecithal eggs have comparatively more yolk than the microlecithal eggs. The yolk is concentrated in one part of the egg (the vegetal pole ), with the cell nucleus and most of the cytoplasm in the other (the animal pole ). The cell cleavage is uneven, and mainly concentrated in the cytoplasma-rich animal pole. The larger yolk content of the mesolecithal eggs allows for
342-426: A nitrogenous end product. Anywhere between fifty and seventy-five percent of total waste nitrogen is converted into uric acid, while the remaining amount is expelled as urea in waste. This uric acid excreted can be released in a solid form and does not result in any net water loss for the frog. This is especially relevant for grey foam-nest tree frogs as they primarily inhabit dry environments, where minimizing water loss
399-414: A protective shell , either flexible or inflexible. Eggs laid on land or in nests are usually kept within a warm and favorable temperature range while the embryo grows. When the embryo is adequately developed it hatches, i.e., breaks out of the egg's shell. Some embryos have a temporary egg tooth they use to crack, pip, or break the eggshell or covering. The largest recorded egg is from a whale shark and
456-540: A result of polyandry are more likely to survive than offspring of monogamous matings. Egg deposition primarily occurs in still, fresh water in order to keep the eggs moist during development. A typical clutch size can be anywhere between 500 and 1250 eggs. Grey foam-nest tree frogs strategically hang their foam nests on branches of trees above water at differing heights. Polyandry can positively impact fertilization success and offspring production in grey-foam nest tree frogs. This might be because more male mates ensures that
513-569: A right angle to their inner two fingers on each hand. The grey foam-nest tree frog typically has a snout length of 50–80 mm. Males have a snout-vent length of 43–75 mm, while females have a 60–90 mm snout-vent length. They have relatively impermeable skin, which allows them to survive dry spells under tree detritus. Their skin is slightly bumpy and dry. Their coloration ranges between white and brown and changes in response to temperature (see adaptations below). They tend to turn white when they die. The grey foam-nest tree frog typically has
570-523: A shell and would dry out in the air. Even air-breathing amphibians lay their eggs in water, or in protective foam as with the Coast foam-nest treefrog, Chiromantis xerampelina . Bird eggs are laid by females and incubated for a time that varies according to the species; a single young hatches from each egg. Average clutch sizes range from one (as in condors ) to about 17 (the grey partridge ). Some birds lay eggs even when not fertilized (e.g. hens ); it
627-498: A snout length of 50–80 mm. Males have a snout-vent length of 43–75 mm, while females have a 60–90 mm snout-vent length. Grey foam-nest tree frogs usually reside in varying habitats, such as savannah, shrubland, forests, pastureland, and urban areas. There have been mentions of these frogs living in Australia in addition to their native range in southern Africa. They are considered habitat specialists, which refers to
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#1732772358058684-945: A species known to only breed in unsettled environments and unperturbed areas. Grey foam-nest tree frogs dislike arid conditions and need humidity to survive; however, they can still be found in dry environments such as: dry forests, miombo, mopane, savannah, and cultivated areas in low altitudes. They are able to survive dry seasons under loose bark, hence why they are referred to as tree frogs. Large rainstorms stimulate an increase in breeding from these frogs, because high humidity decreases egg mortality and improves survival across multiple stages of life. Habitat destruction and disturbance impacts breeding abilities of these frogs. Mating activity of grey foam-nest tree frogs typically occurs at night from October to February in south-eastern Africa's wet summer months. These frogs choose to mate in arboreal settings, as they create their foam nests in tree branches overhanging bodies of water. Female mate choice
741-453: A time away from water. These include uricotelism , rectal water reabsorption, skin resistant to desiccation, and skin that changes color in response to temperature. They have relatively impermeable skin, which allows them to survive dry spells under tree detritus. They are also able to lose up to sixty percent of their body weight over the course of several months. The grey foam-nest tree frog forms uric acid and excretes it from their body as
798-504: A variety of unique habitats. They typically choose environments hanging over bodies of water, but if this is not possible, they lay eggs on any other suitable objects. Occasionally, they lay eggs directly in water or grassy vegetation above water. These tree frogs are more likely to choose lightly wooded savannas and forested areas because these environments have sufficient resources to support adult frogs. Foam-nest building behaviors and patterns have evolved several times. The foam nest made by
855-401: Is highly important. Individual frogs can change their color from chalky white to dark brown, with the brown coloration presenting in a geometric/bark pattern. These frogs change their skin colors in response to temperature differences in order to maintain body temperature and minimize evaporative water loss. When they adopt a darker coloration, their body temperature will warm more rapidly with
912-414: Is known as oviparity , in which the female lays undeveloped eggs that are externally fertilized by a male. Typically large numbers of eggs are laid at one time (an adult female cod can produce 4–6 million eggs in one spawning) and the eggs are then left to develop without parental care. When the larvae hatch from the egg, they often carry the remains of the yolk in a yolk sac which continues to nourish
969-425: Is likely to have arisen due to evolution via natural selection. In contrast, many hole-nesting birds have nearly spherical eggs. Many animals feed on eggs. For example, principal predators of the black oystercatcher 's eggs include raccoons , skunks , mink , river and sea otters , gulls , crows and foxes . The stoat ( Mustela erminea ) and long-tailed weasel ( M. frenata ) steal ducks' eggs. Snakes of
1026-416: Is no need of cryptic colors. However, some have suggested that the protoporphyrin markings on passerine eggs actually act to reduce brittleness by acting as a solid-state lubricant. If there is insufficient calcium available in the local soil, the egg shell may be thin, especially in a circle around the broad end. Protoporphyrin speckling compensates for this, and increases inversely to the amount of calcium in
1083-446: Is not uncommon for pet owners to find their lone bird nesting on a clutch of unfertilized eggs, which are sometimes called wind-eggs. The default colour of vertebrate eggs is the white of the calcium carbonate from which the shells are made, but some birds, mainly passerines , produce coloured eggs. The colour comes from pigments deposited on top of the calcium carbonate base; biliverdin and its zinc chelate , and bilirubin , give
1140-424: Is often limited due to males forcing copulations. Mating primarily occurs on the branches of trees, making females very visible to males. Unpaired males may also intercept females by waiting at the base of a tree. Matings from male interception are often from genetically undesirable males. Over 90% of females mate with ten or more males in the production of a single clutch. The female grey foam-nest tree frog begins
1197-408: Is thought to act as a shock absorber, protecting the calcite shell from fracture during incubation, such as colliding with other eggs in the nest. Most bird eggs have an oval shape , with one end rounded and the other more pointed. This shape results from the egg being forced through the oviduct . Muscles contract the oviduct behind the egg, pushing it forward. The egg's wall is still shapeable, and
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#17327723580581254-399: Is usually motile whereas the female gamete cell, the ovum , is generally larger and sessile . The male and female gametes combine to produce the zygote cell. In multicellular organisms, the zygote subsequently divides in an organised manner into smaller more specialised cells, so that this new individual develops into an embryo . In most animals, the embryo is the sessile initial stage of
1311-463: The benthic zone (associated with or occurring on the bottom of a body of water). Maturity is achieved within six to eight weeks. Male grey foam-nest tree frogs typically do not fight with other males of their species. Currently, there is nothing known about kin recognition and larval sibling competition in this species. Adaptations These frogs often live in arid and semi-arid climates and have developed several adaptations to live months at
1368-415: The coelacanths can reach a size of 9 cm (3.5 in) in diameter, and the young go through full development while in the uterus , living on the copious yolk. Animals are commonly classified by their manner of reproduction, at the most general level distinguishing egg-laying (Latin. oviparous ) from live-bearing (Latin. viviparous ). These classifications are divided into more detail according to
1425-594: The planula , and either develops directly into the adult animals or forms new adult individuals through a process of budding . Microlecithal eggs require minimal yolk mass. Such eggs are found in flatworms , roundworms , annelids , bivalves , echinoderms , the lancelet and in most marine arthropods . In anatomically simple animals, such as cnidarians and flatworms, the fetal development can be quite short, and even microlecithal eggs can undergo direct development. These small eggs can be produced in large numbers. In animals with high egg mortality, microlecithal eggs are
1482-411: The salamanders . Eggs with a large yolk are called macrolecithal. The eggs are usually few in number, and the embryos have enough food to go through full fetal development in most groups. Macrolecithal eggs are only found in selected representatives of two groups: Cephalopods and vertebrates . Macrolecithal eggs go through a different type of development than other eggs. Due to the large size of
1539-413: The adult body, and by the yolk which the egg provides to nourish the embryo. Vertebrate eggs can be classified by the relative amount of yolk . Simple eggs with little yolk are called microlecithal , medium-sized eggs with some yolk are called mesolecithal , and large eggs with a large concentrated yolk are called macrolecithal . This classification of eggs is based on the eggs of chordates , though
1596-540: The air. Often the sex of the developing embryo is determined by the temperature of the surroundings, with cooler temperatures favouring males. Not all reptiles lay eggs; some are viviparous ("live birth"). Dinosaurs laid eggs, some of which have been preserved as petrified fossils. Among mammals, early extinct species laid eggs, as do platypuses and echidnas (spiny anteaters). Platypuses and two genera of echidna are Australian monotremes . Marsupial and placental mammals do not lay eggs, but their unborn young do have
1653-407: The basic principle extends to the whole animal kingdom . Small eggs with little yolk are called microlecithal. The yolk is evenly distributed, so the cleavage of the egg cell cuts through and divides the egg into cells of fairly similar sizes. In sponges and cnidarians , the dividing eggs develop directly into a simple larva, rather like a morula with cilia . In cnidarians, this stage is called
1710-492: The biological sense. In placental mammals , the egg itself is void of yolk, but develops an umbilical cord from structures that in reptiles would form the yolk sac. Receiving nutrients from the mother, the fetus completes the development while inside the uterus. Eggs are common among invertebrates , including insects , spiders , mollusks , and crustaceans . All sexually reproducing life, including both plants and animals, produces gametes . The male gamete cell, sperm ,
1767-404: The cells of incipient multicellular organisms. The cycle of the egg's formation is started by the gamete ovum being released ( ovulated ) and egg formation being started. The finished egg is then ovipositioned and eventual egg incubation can start. Scientists often classify animal reproduction according to the degree of development that occurs before the new individuals are expelled from
Egg (disambiguation) - Misplaced Pages Continue
1824-401: The complex tissues that identify amniotes. The eggs of the egg-laying mammals (the platypus and the echidnas ) are macrolecithal eggs very much like those of reptiles . The eggs of marsupials are likewise macrolecithal, but rather small, and develop inside the body of the female, but do not form a placenta . The young are born at a very early stage, and can be classified as a " larva " in
1881-407: The course of several months. The grey foam-nest tree frog forms uric acid and excretes it from their body as a nitrogenous end product. Anywhere between fifty and seventy-five percent of total waste nitrogen is converted into uric acid, while the other twenty-five to fifty percent is expelled as urea in waste. This uric acid excreted can be released in a solid form and does not cause any water loss for
1938-476: The crowded cliff ledges on which they breed. Yolks of birds' eggs are yellow from carotenoids , it is affected by their living conditions and diet. Bird eggshells are diverse. For example: Tiny pores in bird eggshells allow the embryo to breathe. The domestic hen 's egg has around 7000 pores. Some bird eggshells have a coating of vaterite spherules , which is a rare polymorph of calcium carbonate. In Greater Ani Crotophaga major this vaterite coating
1995-1064: The development that occurs before the offspring are expelled from the adult's body. Traditionally: The term hemotrophic derives from the Latin for blood-feeding, contrasted with histotrophic for tissue-feeding. Chiromantis xerampelina The grey foam-nest tree frog ( Chiromantis xerampelina ), or southern foam-nest tree frog , is a species of frog in the family Rhacophoridae . They are found in southern Africa. Its natural habitats are subtropical or tropical dry forest, dry savanna, moist savanna, subtropical or tropical dry shrubland, subtropical or tropical moist shrubland, subtropical or tropical dry lowland grassland, subtropical or tropical seasonally wet or flooded lowland grassland, intermittent freshwater marshes, arable land, pastureland, rural gardens, urban areas, heavily degraded former forests, ponds, and canals and ditches. Grey foam-nest tree frogs are known for simultaneous polyandry, where female frogs have multiple mates on separate territories that guard
2052-514: The eggs and care for young. This behavior is owed to their external fertilization mechanism. During the mating process, the female frog produces a foam nest, typically on branches that hang above bodies of water, in order to keep her eggs moist as they develop. This practice is what gives the grey foam-nest tree frogs their name. Grey foam-nest tree frogs are arboreal. Like other species in the genus Chiromantis , they have discs on their toes, and their outer two fingers are widely spaced and nearly at
2109-709: The eggs to be suspended in oxygenated water. Grey foam-nest tree frogs that reproduce on land create these nests to minimize drying out, temperature changes, and predation. Polyandry , an important characteristic of the grey foam nest tree frog, has proven to substantially increase offspring survival. Polyandrous matings may provide eggs with additional nutrients via the seminal fluid from multiple males. These nutrients increase yolk availability for post-hatching development and increases survival of tadpoles. Sperm competition may also allow for increased egg interaction with steroids in seminal fluids, which may accelerate yolk metabolism and increase growth rate of tadpoles. Offspring as
2166-412: The female provides different functions for aquatic and terrestrial breeding alike. Some grey foam-nest tree frogs breed exclusively in water. In these water-breeders, foam nests allow the eggs to be suspended in oxygenated water. Grey foam-nest tree frogs that reproduce on land create these nests to minimize drying out, temperature changes, and predation. Development occurs over a period of six days, with
2223-495: The female's eggs will be fertilized. A larger number of males means more sperm production, which therefore increases the likelihood the sperm are genetically compatible with the eggs and allows for a variety of different sperm-based traits. Female grey foam-nest tree frogs lay eggs which are quickly fertilized by the male soon afterwards. Females also create foam for nests. Grey foam-nest tree frogs show remarkable adaptability in their oviposition sites, as they may lay their eggs in
2280-404: The frog. This is especially suitable for grey foam-nest tree frogs due to the fact that they primarily inhabit dry environments, where minimizing water loss is highly important. It is known that adults of both sexes of Afrixalus fornasinii prey on grey foam-nest tree frog eggs and tadpoles. This species is the first African anuran to demonstrate hetero-cannibalism by preying on eggs belonging to
2337-650: The genera Dasypeltis and Elachistodon specialize in eating eggs. Brood parasitism occurs in birds when one species lays its eggs in the nest of another. In some cases, the host's eggs are removed or eaten by the female, or expelled by her chick. Brood parasites include the cowbirds and many Old World cuckoos . Like amphibians, amniotes are air-breathing vertebrates , but they have complex eggs or embryos , including an amniotic membrane . Amniotes include reptiles (including dinosaurs and their descendants, birds) and mammals. Reptile eggs are often rubbery and are always initially white. They are able to survive in
Egg (disambiguation) - Misplaced Pages Continue
2394-494: The individual life cycle, and is followed by the emergence (that is, the hatching) of a motile stage. The zygote or the ovum itself or the sessile organic vessel containing the developing embryo may be called the egg. A recent proposal suggests that the phylotypic animal body plans originated in cell aggregates before the existence of an egg stage of development . Eggs, in this view, were later evolutionary innovations , selected for their role in ensuring genetic uniformity among
2451-411: The larvae for a few days as they learn how to swim. Once the yolk is consumed, there is a critical point after which they must learn how to hunt and feed or they will die. A few fish, notably the rays and most sharks use ovoviviparity in which the eggs are fertilized and develop internally. However, the larvae still grow inside the egg consuming the egg's yolk and without any direct nourishment from
2508-418: The mother also providing direct nourishment. The eggs of fish and amphibians are jellylike. Cartilaginous fish (sharks, skates, rays, chimaeras) eggs are fertilized internally and exhibit a wide variety of both internal and external embryonic development. Most fish species spawn eggs that are fertilized externally, typically with the male inseminating the eggs after the female lays them. These eggs do not have
2565-405: The mother ensuring the eggs stay moist the day after mating. Egg mortality in foam nesting tree frogs remains mostly unexplored, therefore information regarding the matter is limited. Grey foam-nest tree frogs' egg mortality is considered moderate compared to other anuran species. Following the embryonic development, a tadpole breaks free and drops into the water below the foam nest. Tadpoles live in
2622-432: The mother. The mother then gives birth to relatively mature young. In certain instances, the physically most developed offspring will devour its smaller siblings for further nutrition while still within the mother's body. This is known as intrauterine cannibalism . In certain scenarios, some fish such as the hammerhead shark and reef shark are viviparous , with the egg being fertilized and developed internally, but with
2679-421: The norm, as in bivalves and marine arthropods. However, the latter are more complex anatomically than e.g. flatworms, and the small microlecithal eggs do not allow full development. Instead, the eggs hatch into larvae , which may be markedly different from the adult animal. In placental mammals, where the embryo is nourished by the mother throughout the whole fetal period, the egg is reduced in size to essentially
2736-413: The pointed end develops at the back. . One hypothesis is that long, pointy eggs are an incidental consequence of having a streamlined body typical of birds with strong flying abilities; flight narrows the oviduct, which changes the type of egg a bird can lay. Cliff-nesting birds often have highly conical eggs. They are less likely to roll off, tending instead to roll around in a tight circle; this trait
2793-475: The process of reproduction by producing a thick mucus-like fluid from its cloaca (a cavity at the end of the digestive tract in amphibians). During this process, the frog uses its hind legs to whip the mucus into elastic froth that will eventually serve as physical protection for the developing eggs. The female will leave temporarily to rehydrate before returning to the nest. Nest construction can take around five to six hours. Males then incorporate their sperm into
2850-442: The recently laid foam, fertilizing them. The next day, the female will return to its egg-laying site and add a layer of foam to protect the eggs from drying out. Foam-nest building behaviors and patterns have evolved several times. The foam nest made by the female provides different functions for aquatic and terrestrial breeding alike. Some grey foam-nest tree frogs breed exclusively in water. In these water-breeders, foam nests allow
2907-568: The small size of the eggs does not allow for direct development, and the eggs hatch to a larval stage ("fry"). In terrestrial animals with macrolecithal eggs, the large volume to surface ratio necessitates structures to aid in transport of oxygen and carbon dioxide, and for storage of waste products so that the embryo does not suffocate or get poisoned from its own waste while inside the egg, see amniote . In addition to bony fish and cephalopods, macrolecithal eggs are found in cartilaginous fish , reptiles , birds and monotreme mammals. The eggs of
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#17327723580582964-549: The smallest known bird egg, which measures between 6.35–11.4 millimetres (0.250–0.449 in) long and weighs half of a gram (around 0.02 oz). Some eggs laid by reptiles and most fish, amphibians, insects, and other invertebrates can be even smaller. Reproductive structures similar to the egg in other kingdoms are termed " spores ", or in spermatophytes " seeds ", or in gametophytes "egg cells". Several major groups of animals typically have readily distinguishable eggs. The most common reproductive strategy for fish
3021-416: The soil. For the same reason, later eggs in a clutch are more spotted than early ones as the female's store of calcium is depleted. The color of individual eggs is also genetically influenced, and appears to be inherited through the mother only, suggesting that the gene responsible for pigmentation is on the sex-determining W chromosome (female birds are WZ, males ZZ). It used to be thought that color
3078-403: The sun's radiation. It is common for frogs to do this when the air temperature is below 36 °C. White coloration helps them maintain a temperature below the ambient temperature by reflecting heat away. Their skin is resistant to evaporation that rivals terrestrial reptiles, earning them the nickname of "waterproof frogs", but this resistance is not present in their ventral skin. When met with
3135-432: The yolk, the cell division can not split up the yolk mass. The fetus instead develops as a plate-like structure on top of the yolk mass, and only envelopes it at a later stage. A portion of the yolk mass is still present as an external or semi-external yolk sac at hatching in many groups. This form of fetal development is common in bony fish , even though their eggs can be quite small. Despite their macrolecithal structure,
3192-442: Was 30 cm × 14 cm × 9 cm (11.8 in × 5.5 in × 3.5 in) in size. Whale shark eggs typically hatch within the mother. At 1.5 kg (3.3 lb) and up to 17.8 cm × 14 cm (7.0 in × 5.5 in), the ostrich egg is the largest egg of any living bird, though the extinct elephant bird and some non-avian dinosaurs laid larger eggs. The bee hummingbird produces
3249-456: Was applied to the shell immediately before laying, but subsequent research shows that coloration is an integral part of the development of the shell, with the same protein responsible for depositing calcium carbonate, or protoporphyrins when there is a lack of that mineral. In species such as the common guillemot , which nest in large groups, each female's eggs have very different markings, making it easier for females to identify their own eggs on
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