Waterslaters

Pronunciation

How to pronounce Aselloidea: /ˌæsɛˈlɔɪdiə/

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Summary

Aselloidea is a superfamily within the order Isopoda, comprising freshwater isopods primarily found in the northern hemisphere and characterized by distinctive morphological features that separate them from marine forms.

Physical Characteristics

Isopods possess a rigid, segmented chitinous exoskeleton. They are typically flattened dorsoventrally. Color can vary, including gray, white, red, green, or brown. Size ranges from 0.3 mm in some Microcerberidae to nearly 50 cm in deep sea giant isopods. They have two pairs of antennae and seven pairs of jointed legs, with five pairs of branching appendages used for respiration.

Identification Tips

Family identification in Asellota is based on pleonites: Asellidae has small, ring-like pleonites forming a narrow 'pedicel' to the telson, whereas Stenasellidae has larger, always-visible pleonites that reach the margins. Stenasellids are exclusively stygobionts, indicating that any heavily pigmented, eyed waterslaters found on surface are Asellidae.

Habitat

Aquatic environments, often living on the seabed or bottom of freshwater bodies. Terrestrial forms live in cool, moist places; some can swim short distances.

Distribution

Over 10,000 identified species globally, with approximately 4,500 marine species, 500 freshwater species, and 5,000 terrestrial species. Asellota is particularly prevalent in the deep sea and northern hemisphere freshwater environments.

Diet

Isopods have a varied diet: detritivores, grazers, filter feeders, predators, and some are parasites. Terrestrial species primarily consume decaying plant matter, while some aquatic species eat algae or detritus.

Life Cycle

Females brood young in a pouch under the thorax, known as a marsupium. Eggs hatch into mancae, a juvenile stage similar to adults but lacking the last pair of pereopods. Moulting occurs in two stages, known as biphasic moulting.

Reproduction

Typically, isopods have separate sexes, although some species are hermaphroditic. Males transfer sperm to females using modified appendages and fertilization occurs shortly after egg shedding.

Predators

Marine fish, larger aquatic invertebrates, and some terrestrial predatory arthropods.

Ecosystem Role

Isopods play a critical role in decomposition and nutrient cycling within their ecosystems, particularly in mangroves and damp terrestrial habitats.

Economic Impact

Certain isopods are fished commercially and can act as pests in aquaculture and aquariums by damaging fish populations and affecting biodiversity.

Health Concerns

Some isopods are parasites of fish, potentially affecting fisheries and aquaculture; certain species can pose risks to fish health.

Collecting Methods

• Hand collection
• Malaise traps
• Aquatic nets

Preservation Methods

• Alcohol preservation
• Freezing specimens
• Drying and mounting

Evolution

Isopods first appeared in the fossil record during the Carboniferous period (about 300 million years ago). They evolved from marine ancestors and have adapted to various habitats, including terrestrial environments.

Similar Taxa

• Amphipoda
• Tanaidacea

Misconceptions

Some people confuse isopods with insects or other arthropods, leading to misunderstandings about their ecological roles and habitats.

Tags

• Aselloidea
• Isopoda
• freshwater
• taxonomy
• ecology