Amphipoda
Encyclopedia
Amphipoda is an order
of malacostraca
n crustacean
s with no carapace
and generally with laterally compressed bodies. The name amphipoda means "different-footed", and refers to the different forms of appendages, unlike isopods, where all the legs are alike. Of the 7,000 species, 5,500 are classified into one suborder, Gammaridea
. The remainder are divided into two or three further suborders. Amphipods range in size from 1 millimetre and are mostly detritivore
s or scavenger
s. They live in almost all aquatic environments; 750 species live in cave
s and the order also includes terrestrial animal
s and sandhoppers
such as Talitrus saltator
.
wrote in 1899:
The body of an amphipod is divided into 13 segments, which can be grouped into a head, a thorax and an abdomen.
The head is fused to the thorax, and bears two pairs of antennae
and one pair of sessile compound eyes. It also carries the mouthparts, but these are mostly concealed.
The thorax and abdomen are usually quite distinct and bear different kinds of legs; they are typically laterally compressed, and there is no carapace
. The thorax bears eight pairs of uniramous appendage
s, the first of which are used as accessory mouthparts; the next four pairs are directed forwards, and the last three pairs are directed backwards. Gills are present on the thoracic segments, and there is an open circulatory system with a heart
, using haemocyanin
to carry oxygen
in the haemolymph
to the tissues. The uptake and excretion
of salts is controlled by special gland
s on the antennae.
The abdomen is divided into two parts: the pleosome which bears swimming legs; and the urosome, which comprises a telson
and three pairs of uropods which do not form a tail fan as they do in animals such as true shrimp
.
. Samples from the Atlantic Ocean
with a reconstructed length of 34 centimetres (13.4 in) have been assigned to the same species, Alicella gigantea
. The smallest known amphipods are less than 1 millimetre (0.0393700787401575 in) long. The size of amphipods is limited by the availability of dissolved oxygen, such that the amphipods in Lake Titicaca
at an altitude of 3800 metres (12,467.2 ft) can only grow up to 22 millimetre (0.866141732283465 in), compared to lengths of 90 millimetres (3.5 in) in Lake Baikal
at 455 metre.
, which holds her eggs
while they are fertilised
, and until the young are ready to hatch. As a female ages, she produces more eggs in each brood. Mortality is around 25%–50% for the eggs. There are no larva
l stages; the eggs hatch directly into a juvenile
form, and sexual maturity
is generally reached after 6 moults
. Some species have been known to eat their own exuvia
e after moulting.
studies and environmental surveys often lump all amphipods together. Carolus Linnaeus described two species of amphipods in the tenth edition
of his Systema Naturae
, which is defined as the starting point for zoological nomenclature. His descriptions (such as that for Gammarus pulex
: "") were, however, "very poor", and could apply to "nearly every species of amphipod".
Around 7,000 species of amphipods have so far been described, and placed in three or four suborders. One suborder, Gammaridea
, contains more than 5,500 species, including all the freshwater
and terrestrial
species. Suborder Ingolfiellidea
contains around 40 species in 2 families, and the group is sometimes treated among the Gammaridea, rather than as a suborder in their own right.
The classification of the Amphipoda is not yet settled, with the relationships within the suborder Gammaridea suffering the most confusion. The classification given here, from the rank
of suborder down to superfamily, follows that of Martin & Davis, except that superfamilies are recognised here within the Gammaridea. An alternative classification proposed by Myers & Lowry in 2003 moved some families from Gammaridea and united them with the Caprellidea to form a larger Corophiidea
.
A number of families are placed in the order incertae sedis
:
.
Amphipods are found in almost all aquatic environments, from fresh water
to water with twice the salinity
of sea water
. They are almost always an important component of aquatic ecosystems. Most species in the suborder Gammaridea are epibenthic, although they are often collected in plankton
samples. Members of the Hyperiidea are all planktonic and marine. Many are symbionts
of gelatinous animals, including salp
s, medusae
, siphonophores, colonial radiolarians and ctenophores, and most hyperiids are associated with gelatinous animals during some part of their life cycle.
The landhoppers of the family Talitridae
(which also includes semi-terrestrial and marine animals) are terrestrial
, living in damp environments such as leaf litter. Landhoppers have a wide distribution in areas that were formerly part of Gondwana
land, but have colonised parts of Europe
and North America
in recent times.
Around 750 species in 160 genera and 30 families are troglobitic
, and are found in almost all suitable habitats, but with their centres of diversity
in the Mediterranean Basin
, southeastern North America
and the Caribbean
.
Compared to other crustacean groups, such as the Isopoda
, Rhizocephala
or Copepod
a, relatively few amphipods are parasitic
on other animals. The most notable example of parasitic amphipods are the whale lice
(family Cyamidae); unlike other amphipods, these are dorso-ventrally flattened, and have large, strong claws, with which they attach themselves to baleen whale
s. They are the only parasitic crustaceans which cannot swim during any part of their life cycle
.
Most amphipods are detritivore
s or scavenger
s, with some being grazers
of algae
, omnivore
s or predators on small insect
s and crustacean
s. Food is grasped with the front two pairs of legs which are armed with large claws.
, from the Greek
roots
("different") and ("foot"), in reference to the two kinds of legs that amphipods possess. This contrasts with the related Isopoda
, which have a single kind of leg. Particularly among anglers
, amphipods are known as freshwater shrimp, scuds or sideswimmers.
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
of malacostraca
Malacostraca
Malacostraca is the largest of the six classes of crustaceans, containing over 25,000 extant species, divided among 16 orders. Its members display a greater diversity of body forms than any other class of animals, and include crabs, lobsters, shrimp, krill, woodlice, scuds , mantis shrimp and many...
n crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s with no carapace
Carapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
and generally with laterally compressed bodies. The name amphipoda means "different-footed", and refers to the different forms of appendages, unlike isopods, where all the legs are alike. Of the 7,000 species, 5,500 are classified into one suborder, Gammaridea
Gammaridea
Gammaridea is a suborder of small, shrimp-like crustaceans in the order Amphipoda. It contains about 7,275 of the 7,900 described species of amphipods, in approximately 1,000 genera, divided among around 125 families. Gammaridea includes almost all freshwater amphipods , as well as many marine...
. The remainder are divided into two or three further suborders. Amphipods range in size from 1 millimetre and are mostly detritivore
Detritivore
Detritivores, also known as detritophages or detritus feeders or detritus eaters or saprophages, are heterotrophs that obtain nutrients by consuming detritus . By doing so, they contribute to decomposition and the nutrient cycles...
s or scavenger
Scavenger
Scavenging is both a carnivorous and herbivorous feeding behavior in which individual scavengers search out dead animal and dead plant biomass on which to feed. The eating of carrion from the same species is referred to as cannibalism. Scavengers play an important role in the ecosystem by...
s. They live in almost all aquatic environments; 750 species live in cave
Cave
A cave or cavern is a natural underground space large enough for a human to enter. The term applies to natural cavities some part of which is in total darkness. The word cave also includes smaller spaces like rock shelters, sea caves, and grottos.Speleology is the science of exploration and study...
s and the order also includes terrestrial animal
Terrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...
s and sandhoppers
Talitridae
Talitridae is a family of amphipods. Commonly, many of the North American fresh water species of this family are called scuds. Terrestrial species are often referred to as landhoppers and beach dwellers are called sandhoppers or sand fleas.It contains the following genera:*Africorchestia Lowry &...
such as Talitrus saltator
Talitrus saltator
Talitrus saltator, a species of sand hopper, is a common amphipod crustacean of sandy coasts around Europe. The animal's typical "hopping" movement gives the animal its common name, and is produced by a flexion of the abdomen. In order to do this, it must stand on its legs and suddenly extend its...
.
Description
Although they are very abundant, widespread and diverse, amphipods do not feature strongly in the public imagination. Thomas Roscoe Rede StebbingThomas Roscoe Rede Stebbing
The Reverend Thomas Roscoe Rede Stebbing F.R.S., F.L.S. was a British zoologist, who described himself as "a serf to natural history, principally employed about Crustacea". Educated in London and Oxford, he only took to natural history in his thirties, having worked as a teacher until then...
wrote in 1899:
No panegyrist of the Amphipoda has yet been able to evoke anything like popular enthusiasm in their favour. To the generality of observers they are only not repelled because the glance which falls upon them is unarrested, ignores them, is unconscious of their presence.
Anatomy
The head is fused to the thorax, and bears two pairs of antennae
Antenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
and one pair of sessile compound eyes. It also carries the mouthparts, but these are mostly concealed.
The thorax and abdomen are usually quite distinct and bear different kinds of legs; they are typically laterally compressed, and there is no carapace
Carapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
. The thorax bears eight pairs of uniramous appendage
Appendage
In invertebrate biology, an appendage is an external body part, or natural prolongation, that protrudes from an organism's body . It is a general term that covers any of the homologous body parts that may extend from a body segment...
s, the first of which are used as accessory mouthparts; the next four pairs are directed forwards, and the last three pairs are directed backwards. Gills are present on the thoracic segments, and there is an open circulatory system with a heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
, using haemocyanin
Hemocyanin
Hemocyanins are respiratory proteins in the form of metalloproteins containing two copper atoms that reversibly bind a single oxygen molecule . Oxygenation causes a color change between the colorless Cu deoxygenated form and the blue Cu oxygenated form...
to carry oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
in the haemolymph
Hemolymph
Hemolymph, or haemolymph, is a fluid in the circulatory system of some arthropods and is analogous to the fluids and cells making up both blood and interstitial fluid in vertebrates such as birds and mammals...
to the tissues. The uptake and excretion
Excretion
Excretion is the process by which waste products of metabolism and other non-useful materials are eliminated from an organism. This is primarily carried out by the lungs, kidneys and skin. This is in contrast with secretion, where the substance may have specific tasks after leaving the cell...
of salts is controlled by special gland
Gland
A gland is an organ in an animal's body that synthesizes a substance for release of substances such as hormones or breast milk, often into the bloodstream or into cavities inside the body or its outer surface .- Types :...
s on the antennae.
The abdomen is divided into two parts: the pleosome which bears swimming legs; and the urosome, which comprises a telson
Telson
The telson is the last division of the body of a crustacean. It is not considered a true segment because it does not arise in the embryo from teloblast areas as do real segments. It never carries any appendages, but a forked "tail" called the caudal furca is often present. Together with the...
and three pairs of uropods which do not form a tail fan as they do in animals such as true shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
.
Size
Amphipods are typically less than 10 millimetre (0.393700787401575 in) long, but the largest recorded living amphipods were 28 centimetres (11 in) long, and were photographed at a depth of 5300 metres (17,388.5 ft) in the Pacific OceanPacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
. Samples from the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
with a reconstructed length of 34 centimetres (13.4 in) have been assigned to the same species, Alicella gigantea
Alicella gigantea
Alicella gigantea is the largest species of amphipod ever observed, with some individuals reaching up to long. Formerly included in the family Lysianassidae, a new family, Alicellidae, was erected in 2008 for Alicella and five related genera...
. The smallest known amphipods are less than 1 millimetre (0.0393700787401575 in) long. The size of amphipods is limited by the availability of dissolved oxygen, such that the amphipods in Lake Titicaca
Lake Titicaca
Lake Titicaca is a lake located on the border of Peru and Bolivia. It sits 3,811 m above sea level, making it the highest commercially navigable lake in the world...
at an altitude of 3800 metres (12,467.2 ft) can only grow up to 22 millimetre (0.866141732283465 in), compared to lengths of 90 millimetres (3.5 in) in Lake Baikal
Lake Baikal
Lake Baikal is the world's oldest at 30 million years old and deepest lake with an average depth of 744.4 metres.Located in the south of the Russian region of Siberia, between Irkutsk Oblast to the northwest and the Buryat Republic to the southeast, it is the most voluminous freshwater lake in the...
at 455 metre.
Reproduction and life cycle
Mature females bear a marsupium, or brood pouchBrood pouch (Peracarida)
The marsupium or brood pouch, is a characteristic feature of Peracarida, including the orders Amphipoda, Isopoda and Cumacea. It is an egg chamber formed by oostegites, which are appendices which are attached to the coxae of the first pereiopods...
, which holds her eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
while they are fertilised
Fertilisation
Fertilisation is the fusion of gametes to produce a new organism. In animals, the process involves the fusion of an ovum with a sperm, which eventually leads to the development of an embryo...
, and until the young are ready to hatch. As a female ages, she produces more eggs in each brood. Mortality is around 25%–50% for the eggs. There are no larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
l stages; the eggs hatch directly into a juvenile
Juvenile (organism)
A juvenile is an individual organism that has not yet reached its adult form, sexual maturity or size. Juveniles sometimes look very different from the adult form, particularly in terms of their colour...
form, and sexual maturity
Sexual maturity
Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...
is generally reached after 6 moults
Ecdysis
Ecdysis is the moulting of the cuticula in many invertebrates. This process of moulting is the defining feature of the clade Ecdysozoa, comprising the arthropods, nematodes, velvet worms, horsehair worms, rotifers, tardigrades and Cephalorhyncha...
. Some species have been known to eat their own exuvia
Exuvia
Exuviae is a term used in biology to describe the remains of an exoskeleton and related structures that are left after ecdysozoans have moulted...
e after moulting.
Diversity and classification
Amphipods are difficult to identify, due to their small size, and the fact that they must be dissected. As a result, ecologicalEcology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...
studies and environmental surveys often lump all amphipods together. Carolus Linnaeus described two species of amphipods in the tenth edition
10th edition of Systema Naturae
The 10th edition of Systema Naturae was a book written by Carl Linnaeus and published in two volumes in 1758 and 1759, which marks the starting point of zoological nomenclature...
of his Systema Naturae
Systema Naturae
The book was one of the major works of the Swedish botanist, zoologist and physician Carolus Linnaeus. The first edition was published in 1735...
, which is defined as the starting point for zoological nomenclature. His descriptions (such as that for Gammarus pulex
Gammarus pulex
Gammarus pulex is a species of amphipod crustacean found in fresh water across Eurasia. It is a greyish animal, growing to long.-Description:...
: "") were, however, "very poor", and could apply to "nearly every species of amphipod".
Around 7,000 species of amphipods have so far been described, and placed in three or four suborders. One suborder, Gammaridea
Gammaridea
Gammaridea is a suborder of small, shrimp-like crustaceans in the order Amphipoda. It contains about 7,275 of the 7,900 described species of amphipods, in approximately 1,000 genera, divided among around 125 families. Gammaridea includes almost all freshwater amphipods , as well as many marine...
, contains more than 5,500 species, including all the freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
and terrestrial
Terrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...
species. Suborder Ingolfiellidea
Ingolfiellidea
Ingolfiellidea is a small suborder of amphipods with only two families, Ingolfiellidae and Metaingolfiellidae....
contains around 40 species in 2 families, and the group is sometimes treated among the Gammaridea, rather than as a suborder in their own right.
The classification of the Amphipoda is not yet settled, with the relationships within the suborder Gammaridea suffering the most confusion. The classification given here, from the rank
Taxonomic rank
In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...
of suborder down to superfamily, follows that of Martin & Davis, except that superfamilies are recognised here within the Gammaridea. An alternative classification proposed by Myers & Lowry in 2003 moved some families from Gammaridea and united them with the Caprellidea to form a larger Corophiidea
Corophiidea
Corophiidea is a suborder of amphipods, containing the two suborders Caprellida and Corophiida. It was re-established in 2003 by Myers and Lowry, to contain the taxa previously treated as the suborder Caprellida, together with some families formerly placed in the suborder Gammaridea....
.
Gammaridea Gammaridea Gammaridea is a suborder of small, shrimp-like crustaceans in the order Amphipoda. It contains about 7,275 of the 7,900 described species of amphipods, in approximately 1,000 genera, divided among around 125 families. Gammaridea includes almost all freshwater amphipods , as well as many marine...
|
 |
Caprellidea
Hyperiidea Hyperiidea Hyperiidea is a suborder of amphipods, small aquatic crustaceans. Unlike the other suborders of Amphipoda, hyperiids are exclusively marine and do not occur in freshwater. Hyperiids are distinguished by their large eyes and planktonic habitat...
Ingolfiellidea Ingolfiellidea Ingolfiellidea is a small suborder of amphipods with only two families, Ingolfiellidae and Metaingolfiellidae....
|
  |
A number of families are placed in the order incertae sedis
Incertae sedis
, is a term used to define a taxonomic group where its broader relationships are unknown or undefined. Uncertainty at specific taxonomic levels is attributed by , , and similar terms.-Examples:*The fossil plant Paradinandra suecica could not be assigned to any...
:
- Artesiidae
- Baikalogammaridae
- Behningiellidae
- Eulimnogammaridae
- Gammaroporeiidae
- Iciliidae
- Ipanemidae
- Iphigenellidae
- Iulopididae
- Izinkalidae
- Kamakidae
- Kotumsaridae
- Kuriidae
- Luciobliviidae
- Macrohectopodidae
- Maxillipiidae
- Mesogammaridae
- Metacrangonyctidae
- Metaingolfiellidae
- Microprotopidae
- Micruropodidae
- NeomegamphopidaeNeomegamphopidaeNeomegamphopidae is a family of amphipods, comprising the two genera Maragopsis and Neomegamphopus. A third genus, Komatopus, may be a synonym of Magaropsis.-References:...
- Neoniphargidae
- Nihotungidae
- NiphargidaeNiphargidaeNiphargidae is a family of amphipods. It contains the following genera:*Carinurella Sket, 1971*Foroniphargus G. Karaman, 1985*Haploginglymus Mateus & Mateus, 1958*Microniphargus Schellenberg, 1934*Niphargellus Schellenberg, 1938...
- Pachyschesidae
- PallaseidaePallaseidaePallaseidae is a family of amphipod crustaceans endemic to Lake Baikal. Some species are also found in the Angara River which flows out of Lake Baikal, and one species is distributed throughout Northern Palearctic...
- ParacalliopiidaeParacalliopiidaeParacalliopiidae is a family of amphipods....
- Paracrangonyctidae
- ParaleptamphopidaeParaleptamphopidaeParaleptamphopidae is a family of amphipod crustaceans, containing three genera. Paraleptamphopus and Ringanui are both endemic to New Zealand, but Rudolphia lives in Chile.-References:...
- ParamelitidaeParamelitidaeParamelitidae is a family of amphipods, containing the following genera:*Antipodeus Williams & Barnard, 1988*Aquadulcaris Stewart & Griffiths, 1995*Austrocrangonyx Barnard & Barnard, 1983*Austrogammarus Barnard & Karaman, 1983...
- Perthiidae
- Phreatogammaridae
- Pleioplateidae
- Podoprionidae
- Priscillinidae
- Priscomilitaridae
- Prolanceolidae
- Pseudocrangonyctidae
- Regaliidae
- Salentinellidae
- Sanchoidae
- Seborgiidae
- Sinurothoidae
- Sternophysingidae
- Tulearidae
- Typhlogammaridae
- Vitjazianidae
- Wandinidae
Fossil record
Amphipods are thought to have originated in the Lower Carboniferous. Despite the group's age, however, the fossil record of the order Amphipoda is meagre, comprising specimens of 11 species dating back only as far as the Upper Eocene, where they have been found in Baltic amberBaltic amber
The Baltic region is home to the largest known deposit of amber, called Baltic amber or succinite, with about 80% of the world's known amber found there. It dates from 44 million years ago...
.
Ecology
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
to water with twice the salinity
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
of sea water
Seawater
Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...
. They are almost always an important component of aquatic ecosystems. Most species in the suborder Gammaridea are epibenthic, although they are often collected in plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
samples. Members of the Hyperiidea are all planktonic and marine. Many are symbionts
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...
of gelatinous animals, including salp
Salp
A salp or salpa is a barrel-shaped, planktonic tunicate. It moves by contracting, thus pumping water through its gelatinous body...
s, medusae
Medusa (biology)
In biology, a medusa is a form of cnidarian in which the body is shaped like an umbrella, in contrast with polyps. Medusae vary from bell-shaped to the shape of a thin disk, scarcely convex above and only slightly concave below...
, siphonophores, colonial radiolarians and ctenophores, and most hyperiids are associated with gelatinous animals during some part of their life cycle.
The landhoppers of the family Talitridae
Talitridae
Talitridae is a family of amphipods. Commonly, many of the North American fresh water species of this family are called scuds. Terrestrial species are often referred to as landhoppers and beach dwellers are called sandhoppers or sand fleas.It contains the following genera:*Africorchestia Lowry &...
(which also includes semi-terrestrial and marine animals) are terrestrial
Terrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...
, living in damp environments such as leaf litter. Landhoppers have a wide distribution in areas that were formerly part of Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
land, but have colonised parts of Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
and North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
in recent times.
Around 750 species in 160 genera and 30 families are troglobitic
Troglobite
Troglobites are small cave-dwelling animals that have adapted to their dark surroundings. Troglobite species include spiders, insects, fish and others. They live permanently underground and cannot survive outside the cave environment. Troglobite adaptations and characteristics include a heightened...
, and are found in almost all suitable habitats, but with their centres of diversity
Center of diversity
A center of diversity is an area that has a high degree of genetic variation for a particular species or genus of plants that can also be the center of origin for that species. The two areas often, but not always, coincide; the degree of coincidence remains the subject of debate...
in the Mediterranean Basin
Mediterranean Basin
In biogeography, the Mediterranean Basin refers to the lands around the Mediterranean Sea that have a Mediterranean climate, with mild, rainy winters and hot, dry summers, which supports characteristic Mediterranean forests, woodlands, and scrub vegetation...
, southeastern North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
and the Caribbean
Caribbean
The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...
.
Compared to other crustacean groups, such as the Isopoda
Isopoda
Isopods are an order of peracarid crustaceans, including familiar animals such as woodlice and pill bugs. The name Isopoda derives from the Greek roots and...
, Rhizocephala
Rhizocephala
Rhizocephala are derived barnacles that parasitise decapod crustaceans. Their bauplan is uniquely reduced in an extreme adaptation to their parasitic lifestyle, and makes their relationship to other barnacles unrecognisable in the adult form...
or Copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
a, relatively few amphipods are parasitic
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
on other animals. The most notable example of parasitic amphipods are the whale lice
Whale louse
A whale louse is a parasitic crustacean of the family Cyamidae. They are related to the better-known skeleton shrimp, most species of which are found in shallower waters. Whale lice are external parasites, found in skin lesions, genital folds, nostrils and eyes of marine mammals of the order Cetacea...
(family Cyamidae); unlike other amphipods, these are dorso-ventrally flattened, and have large, strong claws, with which they attach themselves to baleen whale
Baleen whale
The Baleen whales, also called whalebone whales or great whales, form the Mysticeti, one of two suborders of the Cetacea . Baleen whales are characterized by having baleen plates for filtering food from water, rather than having teeth. This distinguishes them from the other suborder of cetaceans,...
s. They are the only parasitic crustaceans which cannot swim during any part of their life cycle
Biological life cycle
A life cycle is a period involving all different generations of a species succeeding each other through means of reproduction, whether through asexual reproduction or sexual reproduction...
.
Most amphipods are detritivore
Detritivore
Detritivores, also known as detritophages or detritus feeders or detritus eaters or saprophages, are heterotrophs that obtain nutrients by consuming detritus . By doing so, they contribute to decomposition and the nutrient cycles...
s or scavenger
Scavenger
Scavenging is both a carnivorous and herbivorous feeding behavior in which individual scavengers search out dead animal and dead plant biomass on which to feed. The eating of carrion from the same species is referred to as cannibalism. Scavengers play an important role in the ecosystem by...
s, with some being grazers
Grazing
Grazing generally describes a type of feeding, in which a herbivore feeds on plants , and also on other multicellular autotrophs...
of algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
, omnivore
Omnivore
Omnivores are species that eat both plants and animals as their primary food source...
s or predators on small insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s and crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s. Food is grasped with the front two pairs of legs which are armed with large claws.
Names and etymology
The name Amphipoda comes, via the New LatinNew Latin
The term New Latin, or Neo-Latin, is used to describe the Latin language used in original works created between c. 1500 and c. 1900. Among other uses, Latin during this period was employed in scholarly and scientific publications...
, from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
roots
Root (linguistics)
The root word is the primary lexical unit of a word, and of a word family , which carries the most significant aspects of semantic content and cannot be reduced into smaller constituents....
("different") and ("foot"), in reference to the two kinds of legs that amphipods possess. This contrasts with the related Isopoda
Isopoda
Isopods are an order of peracarid crustaceans, including familiar animals such as woodlice and pill bugs. The name Isopoda derives from the Greek roots and...
, which have a single kind of leg. Particularly among anglers
Angling
Angling is a method of fishing by means of an "angle" . The hook is usually attached to a fishing line and the line is often attached to a fishing rod. Fishing rods are usually fitted with a fishing reel that functions as a mechanism for storing, retrieving and paying out the line. The hook itself...
, amphipods are known as freshwater shrimp, scuds or sideswimmers.