isopods

Isopods are a diverse order of crustaceans in the class Malacostraca, comprising more than 10,000 described species. They inhabit a wide range of environments, including marine, freshwater, and damp terrestrial habitats such as leaf litter and under logs. Notable groups include marine cymothoids, which are often parasitic on fish, and terrestrial woodlice, commonly called pill bugs or sowbugs.

Morphology: Most isopods have a dorsoventrally flattened body with a rigid exoskeleton and seven pairs of legs. They lack a carapace, and the abdomen is typically segmented with uropods at the rear. The body is dorsoventrally compressed, which aids in living under stones and within crevices. Gas exchange mechanisms vary: aquatic species rely on gills, while many land-dwellers have adapted lung-like structures or pseudotracheae to breathe in moist air; respiration is often supplemented by cutaneous exchange.

Ecology and diet: Isopods are mostly detritivores and scavengers, feeding on decaying plant and animal matter; some are herbivores or carnivores, and a few parasitize other animals. Many marine isopods are free-living, others are symbiotic. Reproduction: females brood eggs in a marsupium, a pouch formed by the swimmerets (pleopods) beneath the abdomen; juveniles hatch and grow through molts. Life cycles vary, with direct development in many terrestrial species and free-swimming larval stages in some aquatic lineages.

Importance: Isopods play roles in decomposition and nutrient cycling; they are used as model organisms in ecotoxicology. Some species, like Armadillidium vulgare, are common in human environments, while others can be pests in aquaculture or aquarium settings.