Amphipoda is an
order
Order, ORDER or Orders may refer to:
* Categorization, the process in which ideas and objects are recognized, differentiated, and understood
* Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...
of
malacostraca
Malacostraca (from New Latin; ) is the largest of the six classes of crustaceans, containing about 40,000 living species, divided among 16 orders. Its members, the malacostracans, display a great diversity of body forms and include crabs, lobs ...
n
crustacean
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean gro ...
s with no
carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly
detritivores or
scavengers. There are more than 9,900 amphipod species so far described. They are mostly marine animals, but are found in almost all aquatic environments. Some 1,900 species live in fresh water, and the order also includes the terrestrial
sandhoppers such as ''
Talitrus saltator''.
Etymology and names
The name ''Amphipoda'' comes, via
New Latin
New Latin (also called Neo-Latin or Modern Latin) is the revival of Literary Latin used in original, scholarly, and scientific works since about 1500. Modern scholarly and technical nomenclature, such as in zoological and botanical taxonomy ...
', from the
Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group.
*Greek language, a branch of the Indo-European language family.
**Proto-Greek language, the assumed last common ancestor ...
roots 'on both/all sides' and 'foot'. This contrasts with the related
Isopoda
Isopoda is an order of crustaceans that includes woodlice and their relatives. Isopods live in the sea, in fresh water, or on land. All have rigid, segmented exoskeletons, two pairs of antennae, seven pairs of jointed limbs on the thorax, an ...
, which have a single kind of thoracic leg. Particularly among
anglers, amphipods are known as ''freshwater shrimp'', ''scuds'', or ''sideswimmers''.
Description
Anatomy
The body of an amphipod is divided into 13 segments, which can be
grouped into a head, a
thorax
The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the ...
and an abdomen.
The head is fused to the thorax, and bears two pairs of
antennae and one pair of sessile
compound eye
A compound eye is a visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidia, which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells which dis ...
s.
It also carries the
mouthparts
Mouthparts may refer to:
* The parts of a mouth
** Arthropod mouthparts
*** Insect mouthparts
{{disambig ...
, 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 appendages, the first of which are used as accessory
mouthparts
Mouthparts may refer to:
* The parts of a mouth
** Arthropod mouthparts
*** Insect mouthparts
{{disambig ...
; 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
The heart is a muscular organ found in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon diox ...
, using
haemocyanin to carry
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as we ...
in the
haemolymph to the tissues. The uptake and
excretion
Excretion is a process in which metabolic waste
is eliminated from an organism. In vertebrates this is primarily carried out by the lungs, kidneys, and skin. This is in contrast with secretion, where the substance may have specific tasks afte ...
of
salts
In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively ...
is controlled by special
gland
In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormones) for release into the bloodstream ( endocrine gland) or into cavities inside the body or its outer surface ( exocrine gland).
Structure
...
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.
Size
Amphipods are typically less than long, but the largest recorded living amphipods were long, and were photographed at a depth of in the
Pacific Ocean
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contine ...
.
Samples retrieved from the stomach of a
black-footed albatross had a reconstructed length of ; it was assigned to the same species, ''
Alicella gigantea
''Alicella gigantea'' is the largest species of amphipod ever observed, with some individuals reaching up to long. The average length of A. gigantea ranges from 72.5 to 141.0 millimeters, and its weight ranges from 4.2 to 45 grams Comparatively ...
''. A study of the
Kermadec Trench observed more specimens of ''A. gigantea'', the largest of which was estimated at 34.9 cm long, and collected some for examination, the largest of which was measured at 27.8 cm long. The smallest known amphipods are less than long. The size of amphipods is limited by the availability of
dissolved oxygen, such that the amphipods in
Lake Titicaca
Lake Titicaca (; es, Lago Titicaca ; qu, Titiqaqa Qucha) is a large freshwater lake in the Andes mountains on the border of Bolivia and Peru. It is often called the highest navigable lake in the world. By volume of water and by surface area ...
at an altitude of can only grow up to , compared to lengths of in
Lake Baikal
Lake Baikal (, russian: Oзеро Байкал, Ozero Baykal ); mn, Байгал нуур, Baigal nuur) is a rift lake in Russia. It is situated in southern Siberia, between the Federal subjects of Russia, federal subjects of Irkutsk Oblast, I ...
at .
Some amphipods exhibit
sexual dimorphism
Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most an ...
. In dimorphic species, males are usually larger than females, although this is reversed in the genus
Crangonyx.
[
]
Reproduction and life cycle
Amphipods engage in amplexus, a precopulatory guarding behavior in which males will grasp a female with their gnathopods (enlarged appendages used for feeding) and carry the female held against their ventral surface. Amplexus can last from two to over fifteen days, depending on water temperature, and ends when the female molts, at which point her eggs are ready for fertilisation.
Mature females bear a ''marsupium'', or brood pouch, which holds her eggs while they are fertilised
Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Proce ...
, 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
A larva (; plural larvae ) 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.
Th ...
l stages; the eggs hatch directly into a juvenile
Juvenile may refer to:
*Juvenile status, or minor (law), prior to adulthood
*Juvenile (organism)
*Juvenile (rapper) (born 1975), American rapper
* ''Juvenile'' (2000 film), Japanese film
* ''Juvenile'' (2017 film)
*Juvenile (greyhounds), a greyho ...
form, and sexual maturity is generally reached after 6 moults. Some species have been known to eat their own exuviae after moulting
Diversity and classification
Over 9,950 species of amphipods are currently recognised.[Introduction]
World Amphipoda Database (read November 2016) Traditionally they were placed in the four suborders Gammaridea (which contained the majority of taxa, including all the freshwater and terrestrial
Terrestrial refers to things related to land or the planet Earth.
Terrestrial may also refer to:
* Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on or near the ground, as opposed to ...
species), Caprellidea, Hyperiidea
The Hyperiidea are a suborder of amphipods, small aquatic crustaceans. Unlike the other suborders of Amphipoda, hyperiids are exclusively marine and do not occur in fresh water. Hyperiids are distinguished by their large eyes and planktonic habi ...
, and Ingolfiellidea (the last with only 40 species).
The classification of the Amphipoda is however being rearranged to better reflect their phylogeny, the relationships within the suborder Gammaridea having suffered from the most confusion. A new classification has been developed in the works of Lowry & Myers, where a new large suborder Senticaudata was split off from the Gammaridea in 2013. That taxon, which also encompasses the previous Caprellidea, now comprises over half of the known amphipod species.[ The more recent work of Copilaş-Ciocianu et al. in 2019 (based on COI, H3, 18S and 28S molecular data) still supports the main suborders Amphilochidea, Hyperiidea and Senticaudata, but suggests some reshuffling. The classification given below, from the rank of suborder down to superfamily, however still represents the traditional division as given in Martin & Davis (2001),] except that superfamilies are recognised here within the Gammaridea.
Gammaridea
* Ampeliscoidea
* Alicellidae
* Crangonyctoidea
* Dexaminoidea
* Eusiroidea
* Gammaroidea
Gammaroidea is a superfamily of amphipods in the order Amphipoda.
Families
These families belong to the superfamily Gammaroidea:
* Acanthogammaridae Garjajeff, 1901
* Anisogammaridae Bousfield, 1977
* Baikalogammaridae Kamaltynov, 2002
* Ba ...
* Hadzioidea
* Iphimedioidea
* Kurioidea
* Leucothoidea
* Liljborgioidea
* Lysianassoidea
* Melphidippoidea
* Oedicerotoidea
* Pardaliscoidea
* Phoxocephaloidea
* Stegocephaloidea
* Stenothoidea
* Synopioidea
* Talitroidea
* Thurstonelloidea
Caprellidea
* Caprellida
** Caprelloidea
** Phtisicoidea
Caprellidae is a family of amphipods commonly known as skeleton shrimps. Their common name denotes the threadlike slender body which allows them to virtually disappear among the fine filaments of seaweed, hydroids and bryozoans. They are sometime ...
* Cyamida
** Cyamidae
Hyperiidea
The Hyperiidea are a suborder of amphipods, small aquatic crustaceans. Unlike the other suborders of Amphipoda, hyperiids are exclusively marine and do not occur in fresh water. Hyperiids are distinguished by their large eyes and planktonic habi ...
* Physosomata
** Scinoidea
** Lanceoloidea
* Physocephalata
Physocephalatidira is a parvorder of plankton in the sub-order Hyperiidea. It is the only taxon within the infraorder Physocephalata, making its parent a monotypic taxon
In biology, a monotypic taxon is a taxonomic group ( taxon) that conta ...
** Vibilioidea
** Phronimoidea
** Lycaeopsoidea
** Platysceloidea
Ingolfiellidea
* Ingolfiellidae
Ingolfiellidae is a family (biology), family of Amphipoda, amphipod crustaceans, comprising the following genera:
*''Ingolfiella'' Hansen, 1903
*''Proleleupia'' Vonk & Schram, 2003
*''Rapaleleupia'' Vonk & Schram, 2007
*''Stygobarnardia'' Ruffo, ...
* Metaingolfiellidae
File:Ampelisca brevicornis.jpg, '' Ampelisca brevicornis'' ( Gammaridea: Ampeliscidae)
File:Lepidepecreum longicornis.jpg, '' Lepidepecreum longicorne'' ( Gammaridea: Lysianassidae)
File:Pariambus typicus.jpg, '' Pariambus typicus'' ( Caprellidea: Caprellidae)
File:Hyperia galba.jpg, ''Hyperia galba
''Hyperia galba'' is a species of zooplankton, an amphipod in the family Hyperiidae.
Description
This species grows to 1.2 cm and has a rotund body shape which is translucent and has a light brown colour.
One of the most prominent features ...
'' (Hyperiidea
The Hyperiidea are a suborder of amphipods, small aquatic crustaceans. Unlike the other suborders of Amphipoda, hyperiids are exclusively marine and do not occur in fresh water. Hyperiids are distinguished by their large eyes and planktonic habi ...
: Hyperiidae)
Fossil record
Amphipods are thought to have originated in the Lower Carboniferous. Despite the group's age, however, the fossil record
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
of the order Amphipoda is meagre, comprising specimens of one species from the Lower Cretaceous ( Hauterivian) Weald Clay (United Kingdom
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...
) and 12 species dating back only as far as the Upper Eocene, where they have been found in Baltic amber.
Ecology
Amphipods are found in almost all aquatic environments, from fresh water to water with twice the salinity
Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...
of sea water and even in the Challenger Deep, the deepest known point in the ocean. They are almost always an important component of aquatic ecosystems, often acting as mesograzers. Most species in the suborder Gammaridea are epibenthic, although they are often collected in plankton
Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a cr ...
samples. Members of the Hyperiidea are all planktonic and marine. Many are symbionts
Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...
of gelatinous animals, including salps, medusae, siphonophores, colonial radiolarians and ctenophores, and most hyperiids are associated with gelatinous animals during some part of their life cycle. Some 1,900 species, or 20% of the total amphipod diversity, live in fresh water or other non-marine waters. Notably rich endemic amphipod faunas are found in the ancient Lake Baikal
Lake Baikal (, russian: Oзеро Байкал, Ozero Baykal ); mn, Байгал нуур, Baigal nuur) is a rift lake in Russia. It is situated in southern Siberia, between the Federal subjects of Russia, federal subjects of Irkutsk Oblast, I ...
and waters of the Caspian Sea
The Caspian Sea is the world's largest inland body of water, often described as the List of lakes by area, world's largest lake or a full-fledged sea. An endorheic basin, it lies between Europe and Asia; east of the Caucasus, west of the broad s ...
basin.
The landhoppers of the family Talitridae (which also includes semi-terrestrial and marine animals) are terrestrial
Terrestrial refers to things related to land or the planet Earth.
Terrestrial may also refer to:
* Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on or near the ground, as opposed to ...
, living in damp environments such as leaf litter. Landhoppers have a wide distribution in areas that were formerly part of Gondwana
Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final st ...
, but have colonised parts of Europe
Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located enti ...
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
A center of origin is a geographical area where a group of organisms, either domesticated or wild, first developed its distinctive properties. They are also considered centers of diversity. Centers of origin were first identified in 1924 by Ni ...
in the Mediterranean Basin
In biogeography, the Mediterranean Basin (; also known as the Mediterranean Region or sometimes Mediterranea) is the region of lands around the Mediterranean Sea that have mostly a Mediterranean climate, with mild to cool, rainy winters and w ...
, southeastern North America and the Caribbean.
In populations found in Benthic ecosystems, amphipods play an essential role in controlling brown algae growth. The mesograzer behaviour of amphipods greatly contributes to the suppression of brown algal dominance in the absence of amphipod predators. Amphipods display a strong preference for brown algae in Benthic ecosystems, but due to removal of mesograzers by predators such as fish, brown algae is able to dominate these communities over green and red algae species.
Morphology
Compared to other crustacean groups, such as the Isopoda
Isopoda is an order of crustaceans that includes woodlice and their relatives. Isopods live in the sea, in fresh water, or on land. All have rigid, segmented exoskeletons, two pairs of antennae, seven pairs of jointed limbs on the thorax, an ...
, Rhizocephala or Copepod
Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat. Some species are planktonic (inhabiting sea waters), some are benthic (living on the ocean floor), a number of species have p ...
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
Baleen whales ( systematic name Mysticeti), also known as whalebone whales, are a parvorder of carnivorous marine mammals of the infraorder Cetacea ( whales, dolphins and porpoises) which use keratinaceous baleen plates (or "whalebone") in th ...
s. They are the only parasitic crustaceans which cannot swim during any part of their life cycle
Life cycle, life-cycle, or lifecycle may refer to:
Science and academia
* Biological life cycle, the sequence of life stages that an organism undergoes from birth to reproduction ending with the production of the offspring
* Life-cycle hypothesi ...
.
Foraging behaviour
Most amphipods are detritivores or scavengers, with some being grazers of algae
Algae ( , ; : alga ) are any of a large and diverse group of photosynthetic, eukaryotic organisms. The name is an informal term for a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from ...
, omnivore
An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nut ...
s or predator
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...
s of small insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs ...
s and crustacean
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean gro ...
s. Food is grasped with the front two pairs of legs, which are armed with large claws. More immobile species of amphipods eat higher quantities of less nutritious food rather than actively seeking more nutritious food. This is a type of compensatory feeding. This behaviour may have evolved to minimise predation risk when searching for other foods. ''Ampithoe longimana'', for example, is more sedentary than other species and have been observed to remain on host plants longer. In fact, when presented with both high- and low-nutrition food options, the sedentary species ''Ampithoe longimana'' does not distinguish between the two options. Other amphipod species, such as ''Gammarus mucronatus
''Gammarus mucronatus'' is a species of scud in the family Gammaridae. It is found in the coasts of the North American Atlantic seaboard and the Gulf of Mexico.
Phylogenetics
''Gammarus mucronatus'' is part of the Arthropod phylum: it has an e ...
'' and ''Elasmopus levis'', which have superior predator avoidance and are more mobile, are better able to pursue different food sources. In species without the compensatory feeding ability, survivorship, fertility, and growth can be strongly negatively affected in the absence of high-quality food. Compensatory feeding may also explain the year-round presence of ''A. longimana'' in certain waters. Because algal presence changes throughout the year in certain communities, the evolution of flexible feeding techniques such as compensatory feeding may have been beneficial to survival.
''Ampithoe longimana'' has been observed to avoid certain compounds when foraging for food. In response to this avoidance, species of seaweed such as ''Dictyopteris membranacea'' or ''Dictyopteris hoytii'' have evolved to produce C11 sulfur compounds and C-9 oxo-acids in their bodies as defense mechanisms that specifically deter amphipods instead of deterrence to consumption by other predators.
The incidence of cannibalism and intraguild predation is relatively high in some species, although adults may decrease cannibalistic behaviour directed at juveniles when they are likely to encounter their own offspring. In addition to age, the sex seems to affect cannibalistic behaviour as males cannibalised newly moulted females less than males.
They have, rarely, been identified as feeding on humans; in Melbourne
Melbourne ( ; Boonwurrung/ Woiwurrung: ''Narrm'' or ''Naarm'') is the capital and most populous city of the Australian state of Victoria, and the second-most populous city in both Australia and Oceania. Its name generally refers to a me ...
in 2017 a boy who stood in the sea for about half an hour had severe bleeding from wounds on his legs that did not coagulate easily. This was found to have been caused by "sea fleas" identified as ''lysianassid amphipods'', possibly in a feeding group. Their bites are not venomous and do not cause lasting damage.
See also
*''Pseudamphithoides incurvaria
''Pseudamphithoides incurvaria'' is a species of amphipod crustacean in the family Ampithoidae. It is native to shallow water in the tropical western Atlantic Ocean where it creates a home for itself from fragments of the algae on which it feeds. ...
''
*''Orchestia grillus
''Orchestia grillus'' is a species of beach hopper in the family Talitridae
Talitridae is a family of amphipods. Terrestrial species are often referred to as landhoppers and beach dwellers are called sandhoppers or sand fleas. The name sand f ...
''
References
External links
*
*
{{Taxonbar, from=Q193418
Malacostraca
Taxa named by Pierre André Latreille
Crustacean orders
Extant Hauterivian first appearances