Together with the four species of
echidna, it is one of the five
extant species of
monotremes, the only mammals that lay
eggs instead of giving birth to live young; they are all native to Australia. Like other monotremes, it senses prey through
electrolocation. It is one of the few species of
venomous mammals, as the male platypus has a
spur on the hind foot that delivers a
venom, capable of causing severe pain to humans. The unusual appearance of this egg-laying,
otter-footed mammal baffled European naturalists when they first encountered it, and the first scientists to examine a preserved platypus body (in 1799) judged it a fake, made of several animals sewn together. (Full article...)
A soybean cyst nematode (Heterodera glycines), together with an egg, as viewed through a low-temperature
scanning electron microscope at 1000x magnification. This
nematode infects the roots of soybeans, and the female nematode eventually becomes a
cyst. Infection causes various symptoms that may include
chlorosis of the leaves and stems, root necrosis, loss in seed yield and suppression of root and shoot growth.
The rock hyrax (Procavia capensis), also known as the dassie, is one of four living species of the order
Hyracoidea, and the only living species in its genus. Like all
hyraxes, it is a medium-sized terrestrial mammal between 4 kilograms (9 lb) and 5 kilograms (11 lb) in mass, with short ears and tail. The rock hyrax is found across Africa and the Middle East, at elevations up to 4,200 metres (13,800 ft). It resides in habitats with rock crevices which it uses to escape from predators. Along with the other hyrax species and the
manatee, these are the animals most closely related to the elephant.
Brittle stars, serpent stars, or ophiuroids are
echinoderms in the class Ophiuroidea closely related to
starfish. They crawl across the sea floor using their flexible arms for locomotion. The ophiuroids generally have five long, slender, whip-like arms which may reach up to 60 cm (24 in) in length on the largest specimens. From
New Latinophiurus (“brittle star”), from
Ancient Greek ὄφις (óphis, “serpent”) + οὐρά (ourá, “tail”) (referring to the serpent-like arms of the brittle star). (Full article...)
The bird-cherry ermine (Yponomeuta evonymella) is a species of moth in the family
Yponomeutidae, native to Europe and parts of Asia. The caterpillars are gregarious and feed on the leaves of the
bird cherry tree, forming silken webbing for their own protection. They create further webbing on the trunk and near the base of the tree, which hides them as they
pupate. This photograph shows one of many bird-cherry ermine caterpillar nests on a tree in
Lahemaa National Park, Estonia. In some years, they are so numerous that they can completely strip a tree of its foliage.
The Atlantic spadefish is a species of marine fish
endemic to the shallow waters off the coast of the southeastern United States and in the
Caribbean Sea. They are similar in appearance to
fresh waterangelfish, but much larger, reaching up to three feet (0.9 m) in length. Due to their reputation as strong fighters, they are popular
game fish, especially during the summer months when they are most active.
Aplysina archeri is a species of
sponge that has long tube-like structures of cylindrical shape. Many tubes are attached to one particular part of the organism; a single tube can grow up to 5 feet (1.5 m) high and 3 inches (7.6 cm) thick. These sponges mostly live in the
Atlantic Ocean. These
filter feeders eat food such as
plankton or suspended
detritus as it passes them.
Glaucus atlanticus is a species of small, blue
sea slug. This
nudibranch floats upside down, using the surface tension of the water to stay up, and is carried along by the winds and ocean currents. The blue side of their body faces upwards, blending in with the blue of the water, while the grey side faces downwards, blending in with the silvery surface of the sea. G. atlanticus feeds on other pelagic creatures, including the
Portuguese man o' war.
The flatworms, flat worms, Platyhelminthes, or platyhelminths (from the
Greek πλατύ, platy, meaning "flat" and ἕλμινς (root: ἑλμινθ-), helminth-, meaning "worm") are a
phylum of relatively simple
invertebrates. Unlike other bilaterians, they are
acoelomates (having no
body cavity), and have no specialized
respiratoryorgans, which restricts them to having flattened shapes that allow
oxygen and nutrients to pass through their bodies by
diffusion. The digestive cavity has only one opening for both ingestion (intake of nutrients) and egestion (removal of undigested wastes); as a result, the food cannot be processed continuously. (Full article...)
The Osprey (Pandion haliaetus) is a medium large
raptor which is a specialist fish-eater with a worldwide distribution. It is often known by other
colloquial names such as Fish Hawk, Sea Hawk or Fish Eagle.
The Osprey is particularly well adapted to its diet, with reversible outer toes, closable nostrils to keep out water during dives, and backwards facing scales on the talons which act as barbs to help catch
The Peacock flounder (Bothus mancus) is a species of
lefteye flounder found widely in relatively shallow waters in the
photomontage shows four separate views of the same fish, each several minutes apart, starting from the top left. Over the course of the photos, the fish
changes its colors to match its new surroundings, and then finally (bottom right) buries itself in the sand, leaving only the eyes protruding.
macro view of a Gonia capitatafly feeding on
honey, showing its
pedipalps (the two appendages protruding from the proboscis), two types of insect mouthparts. The proboscis actually comprises the labium, a quadrupedal structure, and a sponge-like labellum at the end. Flies eat solid food by secreting
saliva and dabbing it over the food item. As the saliva dissolves the food, the solution is then drawn up into the mouth as a liquid. The labellum's surface is covered by minute food channels which form a tube leading to the
esophagus, and food is drawn up the channels by
Velodona togata is the only species in the
octopus genus Velodona; the genus and species names come from the large membranes that connect its arms. It was first described by
Carl Chun in his book Die Cephalopoden (from which this illustration is taken) in 1915. A second subspecies was described by
Guy Coburn Robson in 1924.
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Featured articles, which meet a core set of high editorial standards.
Anti-predator adaptation in action: the seal shark Dalatias licha (a–c) and the wreckfish Polyprion americanus (d–f) attempt to prey on
hagfishes. First, the predators approach their potential prey. Predators bite or try to swallow the hagfishes, but the hagfishes have already projected jets of slime (arrows) into the predators' mouths. Choking, the predators release the hagfishes and gag in an attempt to remove slime from their mouths and gill chambers.
Anti-predator adaptations are mechanisms developed through
evolution that assist
prey organisms in their constant struggle against
predators. Throughout the animal kingdom, adaptations have evolved for every stage of this struggle, namely by avoiding detection, warding off attack, fighting back, or escaping when caught.
bilaterian body plan. With an elongated body and a direction of movement the animal has head and tail ends. Sense organs and mouth form the
basis of the head. Opposed circular and longitudinal muscles enable
peristaltic motion. (from Animal)
praying mantis in
deimatic or threat pose displays conspicuous patches of colour to startle potential predators. This is not warning coloration as the insect is palatable. (from Animal coloration)
Image 39A brilliantly-coloured
oriental sweetlips fish (Plectorhinchus vittatus) waits while two boldly-patterned
cleaner wrasse (Labroides dimidiatus) pick parasites from its skin. The spotted tail and fin pattern of the sweetlips signals sexual maturity; the behaviour and pattern of the
cleaner fish signal their availability for
cleaning service, rather than as prey (from Animal coloration)
The following table lists estimated numbers of described extant species for the animal groups with the largest numbers of species, along with their principal habitats (terrestrial, fresh water, and marine), and free-living or parasitic ways of life. Species estimates shown here are based on numbers described scientifically; much larger estimates have been calculated based on various means of prediction, and these can vary wildly. For instance, around 25,000–27,000 species of nematodes have been described, while published estimates of the total number of nematode species include 10,000–20,000; 500,000; 10 million; and 100 million. Using patterns within the
taxonomic hierarchy, the total number of animal species—including those not yet described—was calculated to be about 7.77 million in 2011.[a]
^The application of
DNA barcoding to taxonomy further complicates this; a 2016 barcoding analysis estimated a total count of nearly 100,000
insect species for
Canada alone, and extrapolated that the global insect fauna must be in excess of 10 million species, of which nearly 2 million are in a single fly family known as gall midges (
^Stork, Nigel E. (January 2018). "How Many Species of Insects and Other Terrestrial Arthropods Are There on Earth?". Annual Review of Entomology. 63 (1): 31–45.
S2CID23755007. Stork notes that 1m insects have been named, making much larger predicted estimates.
^Sluys, R. (1999). "Global diversity of land planarians (Platyhelminthes, Tricladida, Terricola): a new indicator-taxon in biodiversity and conservation studies". Biodiversity and Conservation. 8 (12): 1663–1681.