Direct development is a concept in biology. It refers to forms of growth to adulthood that do not involve metamorphosis. An animal undergoes direct development if the immature organism resembles a small adult rather than having a distinct larval form. [1] A frog that hatches out of its egg as a small frog undergoes direct development. A frog that hatches out of its egg as a tadpole does not.
Direct development is the opposite of complete metamorphosis. An animal undergoes complete metamorphosis if it becomes a non-moving thing, for example a pupa in a cocoon, between its larval and adult stages. [2]
Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arboreal or freshwater aquatic ecosystems. Thus amphibians typically start out as larvae living in water, but some species have developed behavioural adaptations to bypass this.
Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some insects, fish, amphibians, mollusks, crustaceans, cnidarians, echinoderms, and tunicates undergo metamorphosis, which is often accompanied by a change of nutrition source or behavior. Animals can be divided into species that undergo complete metamorphosis ("holometaboly"), incomplete metamorphosis ("hemimetaboly"), or no metamorphosis ("ametaboly").
Neoteny, also called juvenilization, is the delaying or slowing of the physiological, or somatic, development of an organism, typically an animal. Neoteny is found in modern humans compared to other primates. In progenesis or paedogenesis, sexual development is accelerated.
Ontogeny is the origination and development of an organism, usually from the time of fertilization of the egg to adult. The term can also be used to refer to the study of the entirety of an organism's lifespan.
A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura. The oldest fossil "proto-frog" Triadobatrachus is known from the Early Triassic of Madagascar, but molecular clock dating suggests their split from other amphibians may extend further back to the Permian, 265 million years ago. Frogs are widely distributed, ranging from the tropics to subarctic regions, but the greatest concentration of species diversity is in tropical rainforest. Frogs account for around 88% of extant amphibian species. They are also one of the five most diverse vertebrate orders. Warty frog species tend to be called toads, but the distinction between frogs and toads is informal, not from taxonomy or evolutionary history.
A larva is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
The axolotl is a paedomorphic salamander closely related to the tiger salamander. It is unusual among amphibians in that it reaches adulthood without undergoing metamorphosis. Instead of taking to the land, adults remain aquatic and gilled. The species was originally found in several lakes underlying what is now Mexico City, such as Lake Xochimilco and Lake Chalco. These lakes were drained by Spanish settlers after the conquest of the Aztec Empire, leading to the destruction of much of the axolotl’s natural habitat.
Amniotes belong to the clade Amniota, a clade of tetrapod vertebrates that comprises sauropsids and synapsids. They are distinguished from the other living tetrapod clade—the lissamphibians—by the development of three extraembryonic membranes, thicker and more keratinized skin, and costal respiration.
A tadpole is the larval stage in the biological life cycle of an amphibian. Most tadpoles are fully aquatic, though some species of amphibians have tadpoles that are terrestrial. Tadpoles have some fish-like features that may not be found in adult amphibians such as a lateral line, gills and swimming tails. As they undergo metamorphosis, they start to develop functional lungs for breathing air, and the diet of tadpoles changes drastically.
Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop inside eggs that remain in the mother's body until they are ready to hatch.
An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell 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.
The common frog or grass frog, also known as the European common frog, European common brown frog, European grass frog, European Holarctic true frog, European pond frog or European brown frog, is a semi-aquatic amphibian of the family Ranidae, found throughout much of Europe as far north as Scandinavia and as far east as the Urals, except for most of the Iberian Peninsula, southern Italy, and the southern Balkans. The farthest west it can be found is Ireland. It is also found in Asia, and eastward to Japan. The nominative, and most common, subspecies Rana temporaria temporaria is a largely terrestrial frog native to Europe. It is distributed throughout northern Europe and can be found in Ireland, the Isle of Lewis and as far east as Japan.
A veliger is the planktonic larva of many kinds of sea snails and freshwater snails, as well as most bivalve molluscs (clams) and tusk shells.
Holometabolism, also called complete metamorphosis, is a form of insect development which includes four life stages: egg, larva, pupa, and imago. Holometabolism is a synapomorphic trait of all insects in the superorder Endopterygota. Immature stages of holometabolous insects are very different from the mature stage. In some species the holometabolous life cycle prevents larvae from competing with adults because they inhabit different ecological niches. The morphology and behavior of each stage are adapted for different activities. For example, larval traits maximize feeding, growth, and development, while adult traits enable dispersal, mating, and egg laying. Some species of holometabolous insects protect and feed their offspring. Other insect developmental strategies include ametabolism and hemimetabolism.
Agalychnis callidryas, commonly known as the red-eyed tree frog, is a species of frog in the subfamily Phyllomedusinae. It is native to forests from Central America to north-western South America. This species is known for its bright coloration, namely its vibrant green body with blue and yellow stripes on the side. It has a white underside, brightly red and orange colored feet, and is named after its distinctive bright red eyes.
The cat flea is an extremely common parasitic insect whose principal host is the domestic cat, although a high proportion of the fleas found on dogs also belong to this species. This is despite the widespread existence of a separate and well-established "dog" flea, Ctenocephalides canis. Cat fleas originated in Africa but can now be found globally. As humans began domesticating cats, the prevalence of the cat flea increased and it spread throughout the world.
Xeris spectrum is a kind of horntail or wood wasp, that lives in coniferous forests. It is large wasp with a powerful ovipositor in females. Unlike other Siricid Wood wasps, Xeris spectrum does not have symbiotic fungi to aid its larvae as they burrow in the wood of fir and other conifer trees making it unique in the Siricidae. It is widespread and is found in large parts of Europe, Asia, Africa and North America.
Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow. The larvae of crustaceans often bear little resemblance to the adult, and there are still cases where it is not known what larvae will grow into what adults. This is especially true of crustaceans which live as benthic adults, more-so than where the larvae are planktonic, and thereby easily caught.
Paragordius varius is a parasite species in the horsehair worm group (Nematomorpha). They cycle between terrestrial and aquatic habitats and are most commonly known for their ability to manipulate their definitive host to jump into a pool of water, which allows them to complete their life cycle. Adults are over 10 cm long and 400 μm in diameter. P. varius is usually found in water or wet areas. The definitive hosts are mainly terrestrial arthropods, most often carabid beetles, crickets and praying mantids.
Ontogenetic niche shift is an ecological phenomenon where an organism changes its diet or habitat during its ontogeny (development). During the ontogenetic niche shifting an ecological niche of an individual changes its breadth and position. The best known representatives of taxa that exhibit some kind of the ontogenetic niche shift are fish, insects and amphibians. A niche shift is thought to be determined genetically, while also being irreversible. Important aspect of the ONS is the fact, that individuals of different stages of a population utilize different kind of resources and habitats. The term was introduced in a 1984 paper by biologists Earl E. Werner and James F. Gilliam.