Amphipods: Distribution, Life Cycle, Habits, Status & More

Amphipods are a group of crustaceans that resemble shrimp and are primarily found in freshwater and the ocean. Even though some species are terrestrial, they still need habitats that are damp. Due to their resemblance to actual shrimp, these terrestrial species are occasionally referred to as “lawn shrimp”.

Amphipods Distribution

The earliest amphipods were discovered in New South Wales, Australia, and thereafter on many islands in the Pacific. When at least one species was discovered in California in 1918, they were first noted in the Western Hemisphere (Mallis 1990).

In the US and Canada, about 90 species are found. Arcitalitrus sylvaticus (Haswell) is the most well-known terrestrial species in the country that sporadically invades buildings (McLaughlin et al. 2005; Smith and Whitman 1992). Talitroides topitotum (Burt) and Talitroides allaudi (Chevreux) are two common species in Florida, according to W. Cranshaw in personal communication from June 30, 2011.

Description And Life Cycle

Amphipods have a lengthy body and a compressed lateral shape. They lack a carapace, the hard covering of the thorax that is present in most crustaceans, and seven of their thoracic segments—rarely six—are unique and end in appendages that resemble legs. The thoracic segments make up the majority of the body since the abdominal segments are frequently united (Borror et al. They have two sets of antennas, one of which is often quite small.

Even while the eyes are typically well-developed, they can occasionally be small or absent. The length of an adult amphipod varies from 5 mm to 20 mm (3/16 to 3/4 inch). Aquatic species are frequently white but can also be found in other colors. Amphipods can occasionally be mistaken for springtails (Collembola, an order of insects). In damp environments, springtails are frequently found, perhaps in great numbers.

With only three pairs of legs, one pair of antennae, and typically a furcula (a forked structure) on the fourth abdominal segment, springtails resemble insect-like arthropods rather than crustaceans. The last abdominal segment of the group of springtails that could be mistaken for an amphipod has a tubular shape.

The mature female amphipod lays her eggs in a brood pouch on the underside of her body. When the female undergoes her first molt during mating, which takes place one to eight days later, the young amphipods, which resemble the adults, emerge from the pouch.

In addition, most species go from egg to adult in a year or less (Smith and Whitman 1992). In contrast to the majority of species, Hyalella Azteca, an aquatic species, has females who lay an average of 15 broods over a five-month period. Scientists utilize the widespread aquatic system indicator Hyalella Azteca to determine the health of the environment and the water quality in streams, lakes, and other bodies of water.

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Ten amphipod species are classified as Missouri species of conservation concern, putting them at risk of extinction in our state. Several of these are species that live in caves and need healthy cave systems and pure groundwater to exist. A relatively tiny, localized disaster that pollutes their specific cave system might potentially wipe them out altogether because their cave habitats isolate them from other locations where they might live.


Numerous amphipods, including those known as beach fleas, can be found living under rocks or decomposing plants on the shore. Amphipods are mostly scavengers. Amphipods were discovered by Mallis in 1900 living beneath ground-covering ivy. In this location, they jumped around like fleas and were challenging to catch. Soft ground contains amphipods up to a depth of 13 mm.

Terrestrial amphipods can also find a suitable environment in the leaf mold beneath bushes (Mallis, 1990). Amphipods that dwell on land require damp ground and the top half-inch of mulch to survive. Following rain, a lot of amphipods can move inside garages or under home doors. They soon pass away there. In contrast to insects, amphipods do not have a waxy layer covering their exoskeleton.

Human Connections

Although most people aren’t even aware that amphipods exist, fish and other aquatic predators look for scuds to eat just as humans are drawn to seafood restaurants for lobster and shrimp. Additionally, a lot of those scud-eating fish are served to people as food.

Ecosystem Connections

Missouri is frequently referred to as the “cave state,” and it’s crucial to keep in mind that a cave is a living community of species with distinct food chains rather than just a hole in the ground. Similar to scuds, which are found aboveground, cave amphipods are significant scavengers and prey species in their environments.

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