Over 1.5 million
living animal
species have been
described, of which around 1.05 million are
insects, over 85,000 are
molluscs, and around 65,000 are
vertebrates. It has been estimated there are as many as 7.77 million animal species on Earth. Animal body lengths range from 8.5 μm (0.00033 in) to 33.6 m (110 ft). They have complex
ecologies and
interactions with each other and their environments, forming intricate
food webs. The scientific study of animals is known as
zoology, and the study of animal behaviors is known as
ethology.
Cutthroat trout usually inhabit and
spawn in small to moderately large, clear, well-
oxygenated, shallow rivers with gravel bottoms. They reproduce in clear, cold, moderately deep lakes. They are native to the
alluvial or
freestone streams that are typical tributaries of the rivers of the Pacific Basin, Great Basin and Rocky Mountains. Cutthroat trout spawn in the spring and may inadvertently but naturally
hybridize with rainbow trout, producing fertile
cutbows. Some
populations of the coastal cutthroat trout (O. c. clarkii) are
semi-anadromous. (Full article...)
An illustration of various Pulmonata (and one predator
arthropod in the lower right), an informal group of
snails and
slugs characterized by the ability to breathe air, by virtue of having a
pallial lung instead of a
gill, or gills. Pulmonata was previously a formal
taxon but lost its status as one in 2010. The group includes many land and freshwater families, and several marine families. Most species have a shell, but no
operculum, although the group does also include several shell-less slugs. Pulmonates are
hermaphroditic, and some groups possess
love darts.
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
bilaterian,
unsegmented, soft-bodied
invertebrates. Being
acoelomates (having no
body cavity), and having no specialised
circulatory and
respiratoryorgans, they are restricted 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 can not be processed continuously. (Full article...)
A cross section of a post-
clitellum segment of an annelid (ringed worm); almost all segments of an annelid contain the same set of organs and parts, a pattern called
metamerism. Annelids have no lungs, but rather exchange
carbon dioxide and
oxygen directly through the moist skin when blood reaches the extremely fine capillaries of the body walls; a dry worm cannot breathe and will die of suffocation. The worm's red blood, which does not consist of
platelets or
red cells but mostly of a liquid containing suspended
hemoglobin, makes a circuit up and down the animal in its closed circulatory systems.
The common clam worm (Alitta succinea) is a widely distributed species of marine
polychaete worm. The photograph shows an
epitoke specimen, the worm having turned into a form capable of reproduction. After releasing its sperm or eggs, the animal will die.
The leopard shark (Triakis semifasciata) is a species of
hound shark found along the
Pacific coast of
North America from the U.S. state of
Oregon to
Mazatlán in Mexico. Typically measuring 1.2–1.5 m (3.9–4.9 ft) long, this slender-bodied shark is characterized by black saddle-like markings and large spots over its back.
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.
Bolinus cornutus is a predatory
species of
sea snail, a marine
gastropodmollusk in the
familyMuricidae. This species is common along the west coast of Africa, where it prefers moderately shallow waters. The shell of the snail is distinctively large, spiny, and club-shaped, usually pale brown or tan in colour, with an elongated and straight
siphonal canal.
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.
Thysanozoon nigropapillosum, the yellow-spotted flatworm, is a species of marine
flatworm in the family
Pseudocerotidae. The species is native to the tropical Indo-Pacific region, where it lives in shallow reef habitats. Flatworms are
hermaphrodites, each being able to act as either male or female. As a donor of sperm, it can grip the margin of the recipient's body, using its two penises in a chopstick-like manner, and deposit sperm on the surface of the skin of the recipient, even while it is actively swimming.
This picture shows a yellow-spotted flatworm photographed in Manta Ray Bay, on the island of
Yap in the Federated States of Micronesia. The flatworm is seen swimming to the right at a depth of 12 metres (40 ft) by undulating the margins of its body. The pseudotentacles at the front have simple eyes and sensory receptors to enable the flatworm to find
tunicates on which it feeds.
The paddyfield pipit (Anthus rufulus) is a
passerine bird in the family
Motacillidae, comprising
pipits,
longclaws and
wagtails. About 15 cm (6 in) in length and native to southern Asia, its plumage in both sexes is greyish-brown above and paler yellowish-brown below, with dark streaking on the breast. A bird of open country, pasture and cultivated fields, it sometimes makes short flights, but mostly runs on the ground, foraging for insects and other small invertebrates. The paddyfield pipit builds its cup-shaped nest in a concealed location on the ground, and may have two or more broods in a year. This A. r. rufulus individual was photographed in
Kanha Tiger Reserve, in the Indian state of
Madhya Pradesh.
Sexual dimorphism is the condition where the two
sexes of the same
species exhibit different characteristics. Differences may include
secondary sex characteristics, size, weight, color, or markings, as well as behavioral and cognitive differences. In the butterfly species Colias dimera (also known as the Dimera sulphur), seen here mating in Venezuela, the male on the right is a brighter shade of yellow than the female.
Glaucus atlanticus is a species of small, blue
sea slug. This
pelagic aeolid
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.
Brittle stars, serpent stars, or ophiuroids (from
Latin ophiurus 'brittle star'; from
Ancient Greekὄφις (óphis) 'serpent', and οὐρά (ourá) 'tail'; referring to the serpent-like arms of the brittle star) 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. (Full article...)
Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a
phylum of simple,
aquaticinvertebrate animals, nearly all living in sedentary
colonies. Typically about 0.5 millimetres (1⁄64 in) long, they have a special feeding structure called a
lophophore, a "crown" of tentacles used for
filter feeding. Most
marine bryozoans live in tropical waters, but a few are found in
oceanic trenches and polar waters. The bryozoans are classified as the
marine bryozoans (Stenolaemata),
freshwater bryozoans (Phylactolaemata), and
mostly-marine bryozoans (Gymnolaemata), a few members of which prefer
brackish water. 5,869living species are known. Originally all of the crown group Bryozoa were colonial, but as an adaptation to a mesopsammal (interstitial spaces in marine sand) life or to deep‐sea habitats, secondarily solitary forms have since evolved. Solitary species has been described in four
genera; Aethozooides, Aethozoon, Franzenella and Monobryozoon). The latter having a statocyst‐like organ with a supposed excretory function. (Full article...)
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Gigantorhynchus ortizi
Gigantorhynchus is a
genus of
Acanthocephala (thorny-headed worms, also known as spiny-headed worms) that
parasitizemarsupials,
anteaters, and possibly baboons by attaching themselves to the intestines using their hook-covered
proboscis. Their life cycle includes an egg stage found in host feces, a cystacanth (larval) stage in an
intermediate host such as
termites, and an adult stage where cystacanths mature in the intestines of the host. This genus is characterized by a cylindrical proboscis with a crown of robust hooks at the apex followed by numerous small hooks on the rest of the proboscis, a long body with
pseudosegmentation,
filiformlemnisci, and ellipsoid
testes. The largest known specimen is the female G. ortizi with a length of around 240 millimetres (9.4 in) and a width of 2 millimetres (0.08 in). Genetic analysis on one species of Gigantorhynchus places it with the related genus Mediorhynchus in the family
Gigantorhynchidae. Six species in this genus are distributed across Central and South America and possibly Zimbabwe. Infestation by a Gigantorhynchus species may cause partial obstructions of the intestines, severe lesions of the intestinal wall, and may lead to death. (Full article...)
...that the Southern Giant Petrel is the leading predator to the
Emperor Penguin, and may be responsible for up to 34% of chick deaths in some colonies?
...that some goats freeze for ten seconds whenever startled due to the genetic condition known as
myotonia congenita, and have thus been dubbed "fainting goats"?
Image 17Idealised
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)
Image 22Bright coloration of orange elephant ear sponge, Agelas clathrodes signals its bitter taste to predators (from Animal coloration)
Image 23A
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 24Animals are unique in having the ball of cells of the early
embryo (1) develop into a hollow ball or
blastula (2). (from Animal)
Image 40The red
pigment in a flamingo's plumage comes from its diet of shrimps, which get it from microscopic algae. (from Animal coloration)
Image 41The microscopic cave snail Zospeum tholussum, found at depths of 743 to 1,392 m (2,438 to 4,567 ft) in the
Lukina Jama–Trojama cave system of
Croatia, is completely blind with a translucent shell (from Fauna)
Image 42The bilaterian gut develops in two ways. In many
protostomes, the blastopore develops into the mouth, while in
deuterostomes it becomes the anus. (from Animal)
Image 43A 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,[1] along with their principal habitats (terrestrial, fresh water,[2] and marine),[3] and free-living or parasitic ways of life.[4] 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.[5] 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.[6][7][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 (
Cecidomyiidae).[8]
^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.
doi:
10.1146/annurev-ento-020117-043348.
PMID28938083.
S2CID23755007. Stork notes that 1m insects have been named, making much larger predicted estimates.
^
abcdNicol, David (June 1969). "The Number of Living Species of Molluscs". Systematic Zoology. 18 (2): 251–254.
doi:
10.2307/2412618.
JSTOR2412618.
^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.
doi:
10.1023/A:1008994925673.
S2CID38784755.