Terrestrial animal

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Okapis are terrestrial vertebrates. Un okapi a la reserve de faunes a okapis, a Epulu, 2005 (4389219071).jpg
Okapis are terrestrial vertebrates.

Terrestrial animals are animals that live predominantly or entirely on land (e.g. cats, dogs, ants, spiders), as compared with aquatic animals, which live predominantly or entirely in the water (e.g. fish, lobsters, octopuses), and amphibians, which rely on a combination of aquatic and terrestrial habitats (e.g. frogs and newts). Some groups of insects are terrestrial, such as ants, butterflies, earwigs, cockroaches, grasshoppers and many others, while other groups are partially aquatic, such as mosquitoes and dragonflies, which pass their larval stages in water. Terrestrial animals tend to be more developed and intelligent than aquatic animals.


Terrestrial classes

The term "terrestrial" is typically applied to species that live primarily on the ground, in contrast to arboreal species, which live primarily in trees.

There are other less common terms that apply to specific groups of terrestrial animals:


Terrestrial invasion is one of the most important events in the history of life. [1] [2] [3] Terrestrial lineages evolved in several animal phyla, among which arthropods, vertebrates and mollusks are representatives of more successful groups of terrestrial animals.

Terrestrial animals do not form a unified clade; rather, they share only the fact that they live on land. The transition from an aquatic to terrestrial life by various groups of animals has occurred independently and successfully many times. [3] Most terrestrial lineages originated under a mild or tropical climate during the Paleozoic and Mesozoic, whereas few animals became fully terrestrial during the Cenozoic.

If internal parasites are excluded, free living species in terrestrial environments are represented by the following eleven phyla:

Roundworms, gastrotrichs, tardigrades, rotifers and some smaller species of arthropods and annelids are microscopic animals that require a film of water to live in, and are therefore considered semi-terrestrial. [4] Flatworms, ribbon worms, velvet worms and annelids all depend on more or less moist habitats. The three remaining phyla, arthropods, mollusks, and chordates, all contain species that have adapted totally to dry terrestrial environments, and which have no aquatic phase in their life cycles.


Animals do not fall neatly into terrestrial or aquatic classification but lie along a continuum: e.g., penguins spend much of their time under water. Pygoscelis papua -Nagasaki Penguin Aquarium -swimming underwater-8a.jpg
Animals do not fall neatly into terrestrial or aquatic classification but lie along a continuum: e.g., penguins spend much of their time under water.

Labeling an animal species "terrestrial" or "aquatic" is often obscure and becomes a matter of judgment. Many animals considered terrestrial have a life-cycle that is partly dependent on being in water. Penguins, seals, and walruses sleep on land and feed in the ocean, yet they are all considered terrestrial. Many insects, e.g. mosquitos, and all terrestrial crabs, as well as other clades, have an aquatic life cycle stage: their eggs need to be laid in and to hatch in water; after hatching, there is an early aquatic form, either a nymph or larva.

There are crab species that are completely aquatic, crab species that are amphibious, and crab species that are terrestrial. Fiddler crabs are called "semi-terrestrial" since they make burrows in the muddy substrate, to which they retreat during high tides. When the tide is out, fiddler crabs search the beach for food. The same is true in the mollusca. Many hundreds of gastropod genera and species live in intermediate situations, such as for example, Truncatella. Some gastropods with gills live on land, and others with a lung live in the water.

As well as the purely terrestrial and the purely aquatic animals, there are many borderline species. There are no universally accepted criteria for deciding how to label these species, thus some assignments are disputed.

Terrestrial panarthropods

Fossil evidence has shown that sea creatures, likely arthropods, first began to make forays onto land around 530 million years ago, in the Early Cambrian. There is little reason to believe, however, that animals first began living reliably[ clarification needed ] on land around that time. A more likely hypothesis is that these early arthropods' motivation for venturing onto dry land was to mate (as modern horseshoe crabs do) or to lay eggs out of the reach of predators. [5] Three groups of arthropods had independently adapted to land by the end of the Cambrian: myriapods, hexapods and arachnids. [6] By the late Ordovician, they may have fully terrestrialized. There are other groups of arthropods, all from malacostracan crustaceans, which independently became terrestrial at a later date: woodlice, sandhoppers, and terrestrial crabs. Additionally, the sister panarthropodan groups Onychophora (velvet worms) are also terrestrial, while the Eutardigrada are also adapted for land to some degree; both groups probably becoming so during the Early Devonian. [7] Among arthropods, many microscopic crustacean groups like copepods and amphipods and Seed Shrimp are known to go dormant when dry and live in transient bodies of water. (Note sandhoppers are amphipods and hexapods emerged from crustaceans as well.)

Vertebrate terrestrialization

By approximately 375 million years ago [3] the bony fish best adapted to life in shallow coastal/swampy waters (such as Tiktaalik roseae). Thanks to relatively strong, muscular limbs (which were likely weight-bearing, thus making them a preferable alternative to traditional fins in extremely shallow water), [8] and lungs which existed in conjunction with gills, Tiktaalik and animals like it were able to establish a strong foothold on land by the end of the Devonian period. In the Carboniferous, tetrapods (losing their gills) became fully terrestrialized, allowing their expansion into most terrestrial niches, though later on some will return back to being aquatic and conquer the air also.

Terrestrial gastropods

Gastropod mollusks are one of the most successful animals that have diversified in the fully terrestrial habitat. [9] They have evolved terrestrial taxa in more than nine lineages. [9] They are commonly referred to as land snails and slugs.

Terrestrial invasion of gastropod mollusks has occurred in Neritopsina, Cyclophoroidea, Littorinoidea, Rissooidea, Ellobioidea, Onchidioidea, Veronicelloidea, Succineoidea, and Stylommatophora, and in particular, each of Neritopsina, Rissooidea and Ellobioidea has likely achieved land invasion more than once. [9]

Most terrestrialization events have occurred during the Paleozoic or Mesozoic. [9] Gastropods are especially unique due to several fully terrestrial and epifaunal lineages that evolved during the Cenozoic. [9] Some members of rissooidean families Truncatellidae, Assimineidae, and Pomatiopsidae are considered to have colonized to land during the Cenozoic. [9] Most truncatellid and assimineid snails amphibiously live in intertidal and supratidal zones from brackish water to pelagic areas. [9] Terrestrial lineages likely evolved from such ancestors. [9] The rissooidean gastropod family Pomatiopsidae is one of the few groups that have evolved fully terrestrial taxa during the late Cenozoic in the Japanese Archipelago only. [9] Shifts from aquatic to terrestrial life occurred at least twice within two Japanese endemic lineages in Japanese Pomatiopsidae and it started in the Late Miocene. [9]

About one-third of gastropod species are terrestrial. [10] In terrestrial habitats they are subjected to daily and seasonal variation in temperature and water availability. [10] Their success in colonizing different habitats is due to physiological, behavioral, and morphological adaptations to water availability, as well as ionic and thermal balance. [10] They are adapted to most of the habitats on Earth. [10] The shell of a snail is constructed of calcium carbonate, but even in acidic soils one can find various species of shell-less slugs. [10] Land-snails, such as Xerocrassa seetzeni and Sphincterochila boissieri, also live in deserts, where they must contend with heat and aridity. [10] Terrestrial gastropods are primarily herbivores and only a few groups are carnivorous. [11] Carnivorous gastropods usually feed on other gastropod species or on weak individuals of the same species; some feed on insect larvae or earthworms. [11]

Semi-terrestrial animals

Semi-terrestrial animals are macroscopic animals that rely on very moist environments to thrive, they may be considered a transitional point between true terrestrial animals and aquatic animals. Among vertebrates, amphibians have this characteristic relying on a moist environment and breathing through their moist skin while reproducing in water.

Many other animal groups solely have terrestrial animals that live like this: land planarians, land ribbon worms, roundworms (nematodes), and land annelids (clitellates) who are very primitive and breathe through skin.

Clitellates or terrestrial annelids demonstrate many unique terrestrial adaptations especially in their methods of reproduction, they tend towards being simpler than their marine relatives, the bristleworms, lacking many of the complex appendages the latter have.

Velvet worms are prone to desiccation not due to breathing through their skin but due to their spiracles being inefficient at protecting from desiccation, like clitellates they demonstrate extensive terrestrial adaptations and differences from their marine relatives including live birth.


Many animals live in terrestrial environments by thriving in transient often microscopic bodies of water and moisture, these include rotifers and gastrotrichs which lay resilient eggs capable of surviving years in dry environments, and some of which can go dormant themselves. Nematodes are usually microscopic with this lifestyle. Although eutardigrades only have lifespans of a few months, they famously can enter suspended animation during dry or hostile conditions and survive for decades, which allows them to be ubiquitous in terrestrial environments despite needing water to grow and reproduce. Many microscopic crustacean groups like copepods and amphipods and seed shrimps are known to go dormant when dry and live in transient bodies of water too. [4]

See also

Further reading

Related Research Articles

Invertebrate Animals without a vertebrate column

Invertebrates are species of animal that neither possess nor develop a vertebral column, derived from the notochord. This includes all animals apart from the chordate subphylum Vertebrata. Familiar examples of invertebrates include arthropods, mollusks, annelid, and cnidarians.

Gill Respiratory organ used by aquatic organisms

A gill is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are kept moist. The microscopic structure of a gill presents a large surface area to the external environment. Branchia is the zoologists' name for gills.

Snail Shelled gastropod

A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name snail is also used for most of the members of the molluscan class Gastropoda that have a coiled shell that is large enough for the animal to retract completely into. When the word "snail" is used in this most general sense, it includes not just land snails but also numerous species of sea snails and freshwater snails. Gastropods that naturally lack a shell, or have only an internal shell, are mostly called slugs, and land snails that have only a very small shell are often called semi-slugs.

Seashell Hard, protective outer layers created by an animal that lives in the sea

A seashell or sea shell, also known simply as a shell, is a hard, protective outer layer usually created by an animal that lives in the sea. The shell is part of the body of the animal. Empty seashells are often found washed up on beaches by beachcombers. The shells are empty because the animal has died and the soft parts have decomposed or been eaten by another animal.

Hermit crab Super family of crustaceans (Paguroidea)

Hermit crabs are anomuran decapod crustaceans of the superfamily Paguroidea that have adapted to occupy empty scavenged mollusc shells to protect their fragile exoskeletons. There are over 800 species of hermit crab, most of which possess an asymmetric abdomen concealed by a snug-fitting shell. Hermit crabs' non-calcified abdominal exoskeleton makes their exogenous shelter system obligatory. Hermit crabs must occupy shelter produced by other organisms, or risk being defenseless.

Aquatic animal Animal that lives in water for most or all of its lifetime

An aquatic animal is any animal, whether invertebrate or vertebrate, that lives in water for most or all of its lifetime. Many insects such as mosquitoes, mayflies, dragonflies and caddisflies have aquatic larvae, with winged adults. Aquatic animals may breathe air or extract oxygen from water through specialised organs called gills, or directly through the skin. Natural environments and the animals that live in them can be categorized as aquatic (water) or terrestrial (land). This designation is polyphyletic.

<i>Acanthostega</i> Extinct genus of tetrapodomorphs

Acanthostega is an extinct genus of stem-tetrapod, among the first vertebrate animals to have recognizable limbs. It appeared in the late Devonian period about 365 million years ago, and was anatomically intermediate between lobe-finned fishes and those that were fully capable of coming onto land.

Marine life Organisms living in salt or brackish water

Marine life, sea life, or ocean life is the plants, animals and other organisms that live in the salt water of the sea or ocean, or the brackish water of coastal estuaries. At a fundamental level, marine life affects the nature of the planet. Marine organisms, mostly microorganisms, produce oxygen and sequester carbon. Marine life in part shape and protect shorelines, and some marine organisms even help create new land. Most life forms evolved initially in marine habitats. By volume, oceans provide about 90% of the living space on the planet. The earliest vertebrates appeared in the form of fish, which live exclusively in water. Some of these evolved into amphibians, which spend portions of their lives in water and portions on land. One group of amphibians evolved into reptiles and mammals and a few subsets of each returned to the ocean as sea snakes, sea turtles, seals, manatees, and whales. Plant forms such as kelp and other algae grow in the water and are the basis for some underwater ecosystems. Plankton forms the general foundation of the ocean food chain, particularly phytoplankton which are key primary producers.

Clitellata Class of annelid worms

The Clitellata are a class of annelid worms, characterized by having a clitellum - the 'collar' that forms a reproductive cocoon during part of their life cycles. The clitellates comprise around 8,000 species. Unlike the class of Polychaeta, they do not have parapodia and their heads are less developed.

Terrestrial locomotion Ability of animals to travel on land

Terrestrial locomotion has evolved as animals adapted from aquatic to terrestrial environments. Locomotion on land raises different problems than that in water, with reduced friction being replaced by the increased effects of gravity.

Intertidal ecology

Intertidal ecology is the study of intertidal ecosystems, where organisms live between the low and high tide lines. At low tide, the intertidal is exposed whereas at high tide, the intertidal is underwater. Intertidal ecologists therefore study the interactions between intertidal organisms and their environment, as well as between different species of intertidal organisms within a particular intertidal community. The most important environmental and species interactions may vary based on the type of intertidal community being studied, the broadest of classifications being based on substrates—rocky shore and soft bottom communities.

Marine invertebrates Marine animals without a vertebrate column

Marine invertebrates are the invertebrates that live in marine habitats. Invertebrate is a blanket term that includes all animals apart from the vertebrate members of the chordate phylum. Invertebrates lack a vertebral column, and some have evolved a shell or a hard exoskeleton. As on land and in the air, marine invertebrates have a large variety of body plans, and have been categorised into over 30 phyla. They make up most of the macroscopic life in the oceans.

Worm Animal that typically has a long tube-like body, no limbs, and no eyes

Worms are many different distantly related bilateral animals that typically have a long cylindrical tube-like body, no limbs, and no eyes.

Arthropod Phylum of invertebrates with jointed exoskeletons

Arthropods are invertebrate animals having an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chitin, often mineralised with calcium carbonate. The arthropod body plan consists of segments, each with a pair of appendages. Arthropods are bilaterally symmetrical and their body possesses an external skeleton. In order to keep growing, they must go through stages of moulting, a process by which they shed their exoskeleton to reveal a new one. Some species have wings. They are an extremely diverse group, with up to 10 million species.

Coconut crab Species of crustacean

The coconut crab is a species of terrestrial hermit crab, also known as the robber crab or palm thief. It is the largest terrestrial arthropod in the world, with a weight of up to 4.1 kg (9 lb). It can grow to up to 1 m in width from the tip of one leg to the tip of another. It is found on islands across the Indian Ocean, and parts of the Pacific Ocean as far east as the Gambier Islands and Pitcairn Islands, similar to the distribution of the coconut palm; it has been extirpated from most areas with a significant human population, including mainland Australia and Madagascar. Coconut crabs also live off the coast of Africa near Zanzibar.

Evolution of tetrapods Evolution of four legged vertebrates and their derivatives

The evolution of tetrapods began about 400 million years ago in the Devonian Period with the earliest tetrapods evolved from lobe-finned fishes. Tetrapods are categorized as animals in the biological superclass Tetrapoda, which includes all living and extinct amphibians, reptiles, birds, and mammals. While most species today are terrestrial, little evidence supports the idea that any of the earliest tetrapods could move about on land, as their limbs could not have held their midsections off the ground and the known trackways do not indicate they dragged their bellies around. Presumably, the tracks were made by animals walking along the bottoms of shallow bodies of water. The specific aquatic ancestors of the tetrapods, and the process by which land colonization occurred, remain unclear. They are areas of active research and debate among palaeontologists at present.

Annelid Phylum of segmented worms

The annelids, also known as the ringed worms or segmented worms, are a large phylum, with over 22,000 extant species including ragworms, earthworms, and leeches. The species exist in and have adapted to various ecologies – some in marine environments as distinct as tidal zones and hydrothermal vents, others in fresh water, and yet others in moist terrestrial environments.

The vertebrate land invasion refers to the aquatic-to-terrestrial transition of vertebrate organisms in the Late Devonian epoch.


In biology, semiaquatic can refer to various types of animals that spend part of their time in water, or plants that naturally grow partially submerged in water. Examples are given below.


This article incorporates CC-BY-2.0 text from the reference [9] and CC-BY-2.5 text from the reference [10] and CC-BY-3.0 text from the reference [11]

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