In oviparous biology, a hatchling is a newly hatched fish, amphibian, reptile, or bird. [1] A group of mammals called monotremes lay eggs, and their young are hatchlings as well.
In oviparous biology, a hatchling is a newly hatched fish, amphibian, reptile, or bird. [1] A group of mammals called monotremes lay eggs, and their young are hatchlings as well.
Fish hatchlings generally do not receive parental care, similar to reptiles. Like reptiles, fish hatchlings can be affected by xenobiotic compounds. For example, exposure to xenoestrogens can feminize fish. [2] As well, hatchlings raised in water with high levels of carbon dioxide demonstrate unusual behaviour, such as being attracted to the scent of predators. This change could be reversed by immersion into gabazine water, leading to the hypothesis that acidic waters affect hatchling brain chemistry. [3]
The behavior of an amphibian hatchling, commonly referred to as a tadpole, is controlled by a few thousand neurons. [4] 99% of a Xenopus hatchling's first day after hatching is spent hanging from a thread of mucus secreted from near its mouth will eventually form; if it becomes detached from this thread, it will swim back and become reattached, usually within ten seconds. [4] While newt hatchlings are only able to swim for a few seconds, Xenopus tadpoles may be able to swim for minutes as long as they do not bump into anything. [4] The tadpole live from remaining yolk-mass in the gut for a period, before it swims off to find food. [5]
The reptile hatchling is quite the opposite of an altricial bird hatchling. Most hatchling reptiles are born with the same instincts as their parents and leave to live on their own immediately after leaving the egg. When first hatched, hatchlings can be several times smaller than their adult forms: Pine Snakes weigh 30 grams when they first hatch, but can grow up to 1,400 grams as adults. [6] This appears to have been the case even in dinosaurs. [7] In sea turtles, hatchling sex is determined by incubation temperature. [8] In species in which eggs are laid then buried in sand, indentations in the sand can be a clue to imminent hatching. [9] In sea turtles, this usually occurs about 60 days after the laying of eggs, and often at night. [10] However, exposure to xenobiotic compounds, especially endocrine-disrupting compounds, can affect hatchling sex ratios as well. [11] Persistent Organic Pollutants (POPs) and other pollutants like octylphenol are also known to increase rate of hatchling mortality and deformity. [12] [13] Upon hatching, animals such as turtles have innate navigational skills, including compass and beacon methods of navigation, to reach safety. For example, turtle hatchlings instinctively swim against waves to ensure they leave the beach and its predators. [14] They also head towards the brightest part of the horizon in order to reach the water: however, human activity has created sources of light which mislead the turtle hatchlings, causing them to not travel directly to the water, making them vulnerable to dehydration and predation. [15] Hatchlings of the species Iguana iguana also gain gut flora essential to digestion from adults as part of their development. [16] In the wild, hatchling survival rates are extremely low due to factors such as predation, for example, by crabs, [17] as well as due to human-made obstacles. [18] Human intervention has also benefitted hatchling reptiles at times. For example, late-hatched loggerhead turtles are taken in by such groups as the University of Georgia to be raised. [19] In species such as crocodiles, hydration levels also play an important role in embryo survival. [20]
Reptile hatchlings, especially those of turtles, are often sold as pets. This has been reported to occur even in places where such practices are illegal. [21]
Bird hatchlings may be altricial or precocial. Altricial means that the young hatch naked and with their eyes closed, and rely totally on their parents for feeding and warmth. Precocial hatching are feathered when hatched, and can leave the nest immediately. [22] In birds, such as the bobwhite quail, hatchlings' auditory systems are more developed than their visual system, as visual stimulation is not present in the egg, while auditory stimulation can reach the embryo even before birth. [23] It has also been shown that auditory development in hatchlings is disrupted by environments high in visual and social stimulation. [24] Many hatchlings are born with some forms of innate behaviours which allow them to improve their ability to survive: for example, hatchling gulls instinctively peck at long objects with marked colour contrast, which leads them to peck at their parents' bills, eliciting a feeding response. [25] Endocrine disruption of hatchling birds increases the rate of deformities and lowers the chances of survival. [26] In bearded vultures, two eggs are laid, but one hatchling will often kill the other. [27] Bird hatchlings raised by humans have sometimes been noted to act towards their human caregivers as their parents. [28]
Reptiles, as most commonly defined, are the animals in the class Reptilia, a paraphyletic grouping comprising all amniotes except synapsids and Aves (birds). The class comprises turtles, crocodilians, snakes, amphisbaenians, lizards, tuatara, and their extinct relatives. In the traditional Linnaean classification system, birds are considered a separate class to reptiles. However, crocodilians are more closely related to birds than they are to other living reptiles, and so modern cladistic classification systems include birds within Reptilia, redefining the term as a clade. Other cladistic definitions abandon the term reptile altogether in favor of the clade Sauropsida, which refers to all animals more closely related to modern reptiles than to mammals. The study of the traditional reptile orders, historically combined with that of modern amphibians, is called herpetology.
Amniotes are a clade of tetrapod vertebrates that comprise sauropsids and synapsids. They are distinguished by a membrane (amnion) protecting the embryo and a lack of a larval stage. Thanks to this, amniotes lay eggs on land or retain them within the mother, unlike anamniotes, which typically lay eggs in water. Older sources, particularly before the 20th century, may refer to amniotes as "higher vertebrates" and anamniotes as "lower vertebrates", based on the discredited idea of the evolutionary great chain of being. The term amniote comes from the Greek ἀμνίον amnion, "membrane surrounding the fetus", and earlier "bowl in which the blood of sacrificed animals was caught", from ἀμνός amnos, "lamb".
In biology, precocial species are those in which the young are relatively mature and mobile from the moment of birth or hatching. The opposite developmental strategy is called altricial, where the young are born or hatched helpless. These categories form a continuum, without distinct gaps between them. Precocial species are normally nidifugous, meaning that they leave the nest shortly after birth or hatching.
Incubation is the process by which certain oviparous (egg-laying) animals hatch their eggs; it also refers to the development of the embryo within the egg under favorable environmental condition. Multiple and various factors are vital to the incubation of various species of animal. In many species of reptile for example, no fixed temperature is necessary, but the actual temperature determines the sex ratio of the offspring. In birds in contrast, the sex of offspring is genetically determined, but in many species a constant and particular temperature is necessary for successful incubation. Especially in poultry, the act of sitting on eggs to incubate them is called brooding. The action or behavioral tendency to sit on a clutch of eggs is also called broodiness, and most egg-laying breeds of poultry have had this behavior selectively bred out of them to increase production.
The freshwater crocodile, also known as the Australian freshwater crocodile, Johnstone's crocodile or also known as freshie, is a species of crocodile endemic to the northern regions of Australia.
The loggerhead sea turtle, is a species of oceanic turtle distributed throughout the world. It is a marine reptile, belonging to the family Cheloniidae. The average loggerhead measures around 90 cm (35 in) in carapace length when fully grown. The adult loggerhead sea turtle weighs approximately 135 kg (298 lb), with the largest specimens weighing in at more than 450 kg (1,000 lb). The skin ranges from yellow to brown in color, and the shell is typically reddish brown. No external differences in sex are seen until the turtle becomes an adult, the most obvious difference being the adult males have thicker tails and shorter plastrons than the females.
Xenoestrogens are a type of xenohormone that imitates estrogen. They can be either synthetic or natural chemical compounds. Synthetic xenoestrogens include some widely used industrial compounds, such as PCBs, BPA, and phthalates, which have estrogenic effects on a living organism even though they differ chemically from the estrogenic substances produced internally by the endocrine system of any organism. Natural xenoestrogens include phytoestrogens which are plant-derived xenoestrogens. Because the primary route of exposure to these compounds is by consumption of phytoestrogenic plants, they are sometimes called "dietary estrogens". Mycoestrogens, estrogenic substances from fungi, are another type of xenoestrogen that are also considered mycotoxins.
The Australian flatback sea turtle is a species of sea turtle in the family Cheloniidae. The species is endemic to the sandy beaches and shallow coastal waters of the Australian continental shelf. This turtle gets its common name from the fact that its shell has a flattened or lower dome than the other sea turtles. It can be olive green to grey with a cream underside. It averages from 76 to 96 cm in carapace length and can weigh from 70 to 90 kg. The hatchlings, when emerging from nests, are larger than other sea turtle hatchlings when they hatch. The flatback turtle is listed by the IUCN Red List of Threatened Species as data deficient, meaning there is insufficient scientific information to determine its conservation status at this time. It was previously listed as vulnerable in 1994. It is not as threatened as other sea turtles due to its small dispersal range.
Agalychnis callidryas, known as the red eyed tree frog, is an arboreal hylid native to Neotropical rainforests where it ranges from Mexico, through Central America, to Colombia. It is sometimes kept in captivity. The scientific name of the red-eyed treefrog, A. callidryas, comes from Greek words kalos (beautiful) and dryas.
An egg tooth is a temporary, sharp projection present on the bill or snout of an oviparous animal at hatching. It allows the hatchling to penetrate the eggshell from inside and break free. Birds, reptiles, and monotremes possess egg teeth as hatchlings. Similar structures exist in Eleutherodactyl frogs, and spiders.
Acetochlor is an herbicide developed by Monsanto Company and Zeneca. It is a member of the class of herbicides known as chloroacetanilides. Its mode of action is elongase inhibition, and inhibition of geranylgeranyl pyrophosphate (GGPP) cyclization enzymes, part of the gibberellin pathway. It carries high risks of environmental contamination.
Sternotherus odoratus is a species of small turtle in the family Kinosternidae. The species is native to southeastern Canada and much of the Eastern United States. It is also known commonly as the common musk turtle, eastern musk turtle, or stinkpot due to its ability to release a foul musky odor from scent glands on the edge of its shell, possibly to deter predation. This turtle is grouped in the same family as mud turtles.
The river cooter is a species of freshwater turtle in the family Emydidae. The species is native to the central and eastern United States.
The yellow mud turtle, also commonly known as the yellow-necked mud turtle, is a species of mud turtle in the family Kinosternidae. The species is endemic to the Central United States and Mexico.
Mecistops is a genus of crocodiles, the slender-snouted crocodiles, native to sub-Saharan Africa.
Marine vertebrates are vertebrates that live in marine environments. These are the marine fish and the marine tetrapods. Vertebrates are a subphylum of chordates that have a vertebral column (backbone). The vertebral column provides the central support structure for an internal skeleton. The internal skeleton gives shape, support, and protection to the body and can provide a means of anchoring fins or limbs to the body. The vertebral column also serves to house and protect the spinal cord that lies within the column.
Alkylphenols are a family of organic compounds obtained by the alkylation of phenols. The term is usually reserved for commercially important propylphenol, butylphenol, amylphenol, heptylphenol, octylphenol, nonylphenol, dodecylphenol and related "long chain alkylphenols" (LCAPs). Methylphenols and ethylphenols are also alkylphenols, but they are more commonly referred to by their specific names, cresols and xylenols.
Spawn is the eggs and sperm released or deposited into water by aquatic animals. As a verb, to spawn refers to the process of releasing the eggs and sperm, and the act of both sexes is called spawning. Most aquatic animals, except for aquatic mammals and reptiles, reproduce through the process of spawning.
Sea turtle migration refers to the long-distance movements of sea turtles notably as adults but may also refer to the offshore migration of hatchings. Sea turtle hatchings emerge from underground nests and crawl across the beach towards the sea. They then maintain an offshore heading until they reach the open sea. The feeding and nesting sites of adult sea turtles are often distantly separated meaning some must migrate hundreds or even thousands of kilometres.
E-SCREEN is a cell proliferation assay based on the enhanced proliferation of human breast cancer cells (MCF-7) in the presence of estrogen active substances. The E-SCREEN test is a tool to easily and rapidly assess estrogenic activity of suspected xenoestrogens. This bioassay measures estrogen-induced increase of the number of human breast cancer cell, which is biologically equivalent to the increase of mitotic activity in tissues of the genital tract. It was originally developed by Soto et al and was included in the first version of the OECD Conceptual Framework for Testing and Assessment of Endocrine Disrupters published in 2012. However, due to failed validation, it was not included in the updated version of the framework published in 2018.
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