amphipod
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What is an amphipod?
An amphipod is an invertebrate of the order Amphipoda in the class Crustacea. They live in seas, lakes, rivers, sand beaches, caves, and moist habitats, even at depths of more than 9,100 m (30,000 feet).
Often mistaken for tiny shrimp, they are an important food source for many animals, including fishes, penguins, and shore birds. They also act as scavengers of carrion.
Their body length ranges from 1 to 140 mm (0.04 to 5.5 inches), and they are often brightly colored. Most amphipods swim actively, using three pairs of abdominal appendages, and are also strong jumpers.
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Are amphipods a type of crustacean?
Yes, amphipods are a type of crustacean. They belong to the order Amphipoda within the class Crustacea, which is part of the phylum Arthropoda.
There are roughly 6,000 described amphipod species that inhabit various environments, including seas, lakes, rivers, sand beaches, and moist habitats. They are frequently mistaken for tiny shrimp because of their resemblance.
As members of the class Malacostraca, amphipods represent a significant portion of all known crustacean species. They play important roles in aquatic ecosystems as a food source for various animals and as scavengers.
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Where do amphipods live?
Amphipods live in diverse environments, including all parts of the sea, lakes, rivers, sand beaches, caves, and moist habitats on many tropical islands. Marine amphipods can be found as deep as 9,100 m (30,000 feet). Freshwater and marine beach species are commonly known as scuds, while those occupying sand beaches are called sand hoppers or sand fleas. They are extraordinarily abundant in rocky coastal regions, often exceeding concentrations of 10,000 per square meter, and are important food sources for many animals.
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What do amphipods look like?
Amphipods are invertebrates belonging to the order Amphipoda, class Crustacea. Often mistaken for tiny shrimp, they are found in seas, lakes, rivers, sand beaches, caves, and moist habitats.
Their body length ranges from 1 to 140 mm, but midlatitude species are about 4 to 10 mm long. Many amphipods are brightly colored, such as red, pink, yellow, green, or blue. The body is usually compressed from side to side, which helps them move quickly through algae. Most amphipods swim actively, using three pairs of abdominal appendages for propulsion, and they can also jump strongly.
They have long, hairy antennae, and their head and tail ends often curve downward. Their eyes lack stalks. Some species have piercing and sucking mouthparts and stay in place on nonmoving invertebrates like cnidarians and sponges.
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How do amphipods survive in their habitats?
Amphipods are small crustaceans that live in diverse habitats, including seas, lakes, rivers, sand beaches, caves, and moist tropical environments. They have even been found in the deepest parts of the ocean, at depths of over 9,100 meters (30,000 feet).
Their survival strategies include:
* Locomotion Most amphipods are active swimmers, using three pairs of abdominal appendages for propulsion, and they are also capable jumpers.
* Feeding Some species have specialized mouthparts for piercing and sucking, allowing them to feed on sedentary invertebrates. Others are scavengers and herbivores, burrowing into the sea bottom to find food.
* Habitat Their body shape, compressed from side to side, facilitates movement through algae.
* Reproduction Females carry fertilized eggs in a brood pouch near their gills, ensuring the eggs are oxygenated and protected.2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
Why are amphipods important to their ecosystems?
Amphipods play a crucial role in their ecosystems as a food source and scavengers. They are an important food source for many fishes, invertebrates, penguins, shore birds, small cetaceans, and pinnipeds. Additionally, amphipods act as scavengers, consuming carrion and a wide range of organic matter, both plant and animal, whether living or dead. Some species consume forest leaf litter and algae. They can be extraordinarily abundant, sometimes exceeding concentrations of 10,000 per square meter, and are often mistaken for tiny shrimp. Some amphipods have also formed symbiotic, commensal, and parasitic relationships with other marine animals.
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amphipod, any member of the invertebrate order Amphipoda (class Crustacea) inhabiting all parts of the sea, lakes, rivers, sand beaches, caves, and moist (warm) habitats on many tropical islands. Marine amphipods have been found at depths of more than 9,100 m (30,000 feet). Freshwater and marine beach species are commonly known as scuds; those that occupy sand beaches are called sand hoppers, or sand fleas (see sand flea). About 6,000 species have been described. Extraordinarily abundant in the rocky coastal regions of all seas and often exceeding concentrations of 10,000 per square m (1,000 per square foot), amphipods are often mistaken for tiny shrimp, which they resemble. They are important food for many fishes, invertebrates, penguins, shore birds, small cetaceans, and pinnipeds. Amphipods are also important as scavengers of carrion.
Body length varies from 1 to 140 mm (0.04 to 5.5 inches), but the amphipod of midlatitude regions is about 4 to 10 mm long (0.16 to 0.4 inch). Many amphipods are brightly coloured—red, pink, yellow, green, or blue. The body is usually compressed from side to side (i.e., height is greater than width), thus in part facilitating rapid sliding movement through algal fronds (leaflike structures). Most amphipods are active swimmers, being propelled by three pairs of abdominal appendages. That they are also strong jumpers is best seen in sand fleas.
The antennae are long and hairy. As in the shrimp, the head and tail ends are often curved downward. The eyes are sessile (without a stalk). Some species with piercing and sucking mouthparts are rather strictly confined to sedentary positions on large, mostly nonmoving invertebrates, such as cnidarians and sponges. Members of one marine family (Cheluridae) chew wood and are always found associated with the isopod Limnoria, another wood borer. In contrast, other amphipod species (such as those of the family Gammaridae) are mostly scavengers and herbivores that typically burrow into the soft mud of the sea bottom. Amphipod gills are partially protected by long coxae, which are ventral extensions of the basal leg segments. Amphipods have compound eyes, like crabs and insects; however, the eyes of amphipods never occur on stalks.
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The sexes are separate, males often being characterized by enlarged gnathopods (claws on the second thoracic segment) used to grasp females during copulation. The male presumably emits sperm, or spermatophores (balls of sperm), to fertilize the eggs of the female externally.
The number of eggs in a clutch varies from one to more than 250. The arrangement of gills provides a chamber for fertilized eggs, which are carried externally by the female and held in a cluster near the gills. The gammaridean egg cluster is probably oxygenated with water currents created by beating appendages called pleopods. Eggs hatch in 2 to 59 days, and the young may remain in the brood pouch for from 2 to 35 days. After six to nine molts over an interval of one to four months, sexual maturity is attained. A few cold-water species live at least a year, perhaps far longer.
The generic diversity of amphipods is apparently higher in cool waters than in warm ones. One enigma is the enormous diversity of species, more than 290 in the Siberian Lake Baikal. Fossilization of amphipods is poor; only six genera have been recorded, the earliest of which, Paleogammarus, is found in Baltic amber of the Early Eocene epoch (55.8 to 48.6 million years ago); it closely resembles a recent genus, Crangonyx.