Mud Puppy

Mud puppy, common name for North American salamanders of the genus Necturus, found in rivers and streams throughout the E United States and SE Canada. The name derives from an erroneous belief that mud puppies bark. Like its relative, the European olm, the mud puppy exhibits neoteny, i.e., it reaches sexual maturity without losing its larval characteristics. Adults have lungs, characteristic of most adult salamanders, as well as gills, characteristic of larvae. Their short, sturdy limbs develop at an early stage. The mud puppy may reach a length of 12 in. (30 cm); it is reddish brown and black-spotted above and grayish below, with conspicuous bushy red gills at the sides of its head. It walks on river bottoms and feeds primarily on crayfish and aquatic plants. 

Mud puppies are classified in the phylum Chordata, subphylum Vertebrata, class Amphibia, order Urodela, family Proteidae.


Newt

Newt, name for members of a large salamander family, widely distributed in the Northern Hemisphere and including the common European salamanders. Newts are lizardlike in shape and are usually under 6 in. (15 cm) long including the slender tail. Some are brightly colored and secrete irritating substances. Like other salamanders, newts go through an aquatic, gilled larval stage. In some species the adults remain aquatic, although they lose their gills and breathe air; in others the adults are terrestrial, returning to water only to breed. Still other newts go through two adult stages: a terrestrial stage, during which they are called efts, is followed by a permanent aquatic stage. One such species is the common red-spotted newt (Diemictylus viridescens) of the E United States, known in its terrestrial stage as red eft. The 3-in. (7.5-cm) adult lays its eggs in spring on the stems and leaves of water plants. The greenish-brown larvae remain in the water for several months before emerging as efts, orange-red with a double row of black-ringed vermilion spots. The efts spend two or three years on land, hibernating in winter under leaves, and then return permanently to the water, becoming olive green and developing a broad swimming tail. 

Newts are classified in the phylum Chordata, subphylum Vertebrata, class Amphibia, order Urodela, family Salamandridae.


Salamanders

Salamander, an amphibian of the order Urodela, or Caudata. Salamanders have tails and small, weak limbs; superficially they resemble the unrelated lizards (which are reptiles), but they are easily distinguished by their lack of scales and claws, and by their moist, usually smooth skins. Salamanders are found in damp regions of the northern temperate zone and are most abundant in North America. Most are under 6 in. (15 cm) long, but the giant salamander of Japan (Megalobatrachus japonicus) may reach a length of over 5 ft (1.5 m). Most salamanders are terrestrial as adults, living near water or in wet vegetation, but some are aquatic and a few are arboreal, burrowing, or cave-dwelling. Most are nocturnal, and all avoid direct light. Salamanders are able to regenerate a lost limb or tail. They feed on small animals, such as insects, worms, and snails.
Most salamanders breed in water and are gregarious at breeding time, when there is usually a courtship display. In most species fertilization is internal. The male deposits sperm packets, which the female picks up with the cloaca; the sperm is then stored until fertilization takes place. The eggs, surrounded by gelatinous material, are usually laid in ponds or brooks, where they develop into aquatic larvae that can breathe by means of gills. A few salamanders breed on land, laying their eggs under rotting vegetation; the young pass through the gilled stage in the egg, emerging as miniature adults. Such strictly terrestrial forms are the red-backed salamander (Plethodon cinereus) and slimy salamander (P. glutinosus) of E United States and the slender salamander (Batrachoseps attenuatus) of the Pacific coast.

Most salamanders, including most that remain in an aquatic environment, go through a typical amphibian metamorphosis into air-breathing adults. Generally the adults have lungs, but in the large family of lungless salamanders (Plethodontidae) breathing occurs entirely through the skin and the lining of the throat. In a few salamanders growth occurs without metamorphosis, and the gilled, juvenile form is able to reproduce. This phenomenon (called neoteny) is found in the sirens (family Sirenidae) of S United States and N Mexico, in the mud puppies (family Protidae), and in the Mexican axolotl. 

Classification

There are over 200 salamander species, classified in approximately 60 genera and 8 families of the phylum Chordata, subphylum Vertebrata, class Amphibia, order Urodela.


Toad

Toad, name applied to certain members of the amphibian order Anura, which also includes the frog. Although there is no clear-cut distinction between toads and frogs, the name toad commonly refers to those species that have relatively short legs, stout bodies, and thick skins, and are less aquatic as adults than the long-legged, slender-bodied frogs.

Sometimes the term toad is restricted to the so-called true toads, members of the family Bufonidae. These are characterized by warty skins and prominent parotid glands behind the eyes and as a group are the most terrestrial of the order. In most the feet are only slightly webbed. They range in length from about 1 to 7 in. (2.5–18 cm). Most species belong to the genus Bufo; members of these species spend much of the time on land, generally near water. They generally live in cool, moist places and absorb moisture through the skin. The white fluid that they exude through the skin, as well as from the parotid glands, is very poisonous and causes intense burning if it comes in contact with the eyes or mouth; however, contrary to an old belief, it does not cause warts. Toads, like frogs, move on land by jumping and feed on insects and grubs. Also like frogs, they usually lay their eggs in water in strands of jelly. Fertilization is external. The egg hatches into a tadpole, a gilled, aquatic, larval toad that undergoes metamorphosis into the adult.

There are about a dozen Bufo species in the United States, among them the common American toad (Bufo americanus), Fowlers toad (B. fowleri), of the E United States, and the red-spotted toad (B. punctatus), of the Southwest. The cane, marine, or giant toad (B. marinus), a large toad native to Central and N South America, was widely introduced in warm regions (Caribbean, Pacific, Australia, and Florida) to control agricultural pests but is now regarded as an invasive species; they compete with and prey on native species, and their toxic secretions can kill predators.

The spadefoot toads, burrowing toads of the family Pelobatidae, are represented in the United States by several species of the genus Scaphiopus. Toads are classified in the phylum Chordata, subphylum Vertebrata, class Amphibia, order Anura.

Caecilians

Caecilian (sēsĭl`ēən), any of the legless, tailless tropical amphibians belonging to the order Gymnophiona (or Apoda). Most adult caecilians resemble earthworms superficially but have vertebrate characteristics such as jaws and teeth.

Caecilians range in size from 7 in. to 4.5 ft (18 cm–140 cm); most are about 1 ft (30 cm) long. Their bodies are ringed with grooves, which in some species contain small scales imbedded in the skin; possession of scales is a primitive amphibian trait. There is a groove on either side of the head, each containing a retractable sensory tentacle. The eyes of caecilians are nearly functionless, and some species are eyeless.

Caecilians are found in swampy places in most tropical parts of the world, but are seldom seen because of their burrowing behavior. They eat small invertebrates such as termites and earthworms. A few species remain aquatic as adults and resemble eels.

There are more than 180 species of caecilians, divided into 10 families. They are classified in the phylum Chordata, subphylum Vertebrata, class Amphibia, order Gymnophiona (or Apoda).

Chimpanzee

Chimpanzee, an ape, genus Pan, of the equatorial forests of central and W Africa. The common chimpanzee, Pan troglodytes, lives N of the Congo River. Full-grown animals of this species are up to 5 ft (1.5 m) tall and weigh about 150 lb (68 kg); they have an arm spread of up to 9 ft (2.7 m) and are much stronger than humans. They are covered with long, black hair over most of the body and have naked faces ranging in color from nearly white to nearly black. The pygmy chimpanzee, P. paniscus, now usually called the bonobo, lives south of the Congo. It is a bit smaller and more slenderly built, with a black face.

Chimpanzees spend much time on the ground, where they walk on all fours, using the soles of the feet and the knuckles of the hands; they can also stand on two legs and sometimes walk this way for short distances. They climb trees in pursuit of food and for nesting and can swing by their hands from branch to branch. Their diet consists largely of fruit and other plant matter, but they also hunt and eat small animals, including monkeys. They use and even make primitive tools; for example, they collect termites using twigs and crack nuts using stones. Many primatologists now attribute culture to chimpanzees, noting learned variations in such skills and habits among different groups.

Chimpanzees move about the forest in bands of varying composition, usually numbering six to ten individuals. The males of a group engage in dominance contests involving much screaming and stamping. Family groups consist of mothers and offspring; females mate with many males during their fertile periods. A single infant is born every three to eight years; young chimpanzees ride about on their mothers' backs. Under ideal circumstances chimpanzees may live 50 years.

Although incapable of speech beyond their own simple vocalizations, captive chimpanzees have been taught to communicate in a language using visual rather than verbal symbols. Because of their close evolutionary relationship to humans they are often used for medical and behavioral experimentation, but the degree to which chimpanzees and humans are genetically close is a subject of dispute, with estimates of the amount of DNA the species share ranging from 94.6% to 99.4%. Chimpanzees, especially bonobos, are considered endangered species because of hunting and loss of habitat.

Chimpanzees are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Primates, family Pongidae.

Insect

Insect, invertebrate animal of the class Insecta of the phylum Arthropoda. Like other arthropods, an insect has a hard outer covering, or exoskeleton, a segmented body, and jointed legs. Adult insects typically have wings and are the only flying invertebrates.

The body of the typical adult insect is divided into three distinct parts, the head, thorax, and abdomen. The head bears three pairs of mouthparts, one pair of compound eyes, three simple eyes (ocelli), and one pair of jointed sensory antennae. The thorax is divided into three segments, each with a pair of jointed legs, and bears two pairs of wings. The abdomen has posterior appendages associated with reproduction. The exoskeleton is composed of a horny substance called chitin.

Insects breathe through a complex network of air tubes (tracheae) that open to the outside through a series of small valved apertures (spiracles) along the sides of the body. In chewing insects the digestive system includes a muscular gizzard that is lacking in sucking insects. The simple circulatory system is composed of a tubular heart that pumps blood forward into the head, from which it diffuses through the tissues and back into the heart. The aquatic larvae of many insects breathe by means of external gills; some very primitive species breathe directly through the body wall.

Insect Species

There are about 900,000 known insect species, three times as many as all other animal species together, and thousands of new ones are described each year. They are commonly grouped in 27 to 32 orders, depending upon the classification used. The largest order is that of the beetles (Coleoptera). Next, in order of size, are the moths and butterflies (Lepidoptera); the wasps, ants, and bees (Hymenoptera); and the flies and mosquitoes (Diptera). Other major orders are the true bugs (Hemiptera); the cicadas, aphids, and scale insects (Homoptera); the grasshoppers and crickets (Orthoptera); the cockroaches (Blattodea); and the mantids (Mantodea).

Insects are found throughout the world except near the poles and pervade every habitat except the sea (although there is one marine species of water strider). Fossil records indicate that many species exist today in much the same form as they did 200 million years ago. Their enormous biological success is attributed to their small size, their high reproductive rate, and the remarkable adaptive abilities of the group as a whole, shown by the enormous variety in body structure and way of life. The mouthparts may be adapted to chewing, sucking, piercing, or lapping and the legs for walking, running, jumping, burrowing, or swimming. Insects may feed on plants or decaying matter or prey upon other small animals (especially other insects) or parasitize larger ones; they may be omnivorous or highly specialized in their diets. They display a remarkable variety of adaptive shapes and colors that may serve either as camouflage or as warning (see mimicry). Some have stinging spines or hairs and blistering or noxious secretions, used for defense.

Reproduction

A few species, notably the fireflies, produce light, used as a signal in courtship, by a chemical reaction. The sexes are separate in insects, and reproduction is usually sexual, although in many insect groups eggs sometimes develop without fertilization by sperm (see parthenogenesis). In some insects, such as bees, unfertilized eggs become males and fertilized eggs females. In others, such as aphids, all-female generations are produced by parthenogenesis. Eggs are usually laid in a sheltered place; in a few insects they are retained and hatched internally. After hatching, the insect must molt periodically as it grows, since the rigid exoskeleton does not allow much expansion. A new, soft exoskeleton forms beneath the old one, and after each molt the insect undergoes a rapid expansion before its new covering hardens. The stages between molts are called instars; the final instar is the adult.

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