Meiofauna
Guides
Copepoda
copepods
Copepods are small aquatic crustaceans and one of the most abundant and diverse multicellular organisms on Earth. They occupy nearly every aquatic habitat, from marine plankton to deep ocean floors, freshwater lakes, groundwater systems, and even moist terrestrial environments such as leaf litter and bromeliad phytotelmata. The group includes free-living forms as well as highly modified parasites. Copepods are fundamental components of aquatic food webs, serving as critical prey for fish, whales, and other marine life, while also contributing to nutrient cycling and carbon sequestration through the biological pump.
Halacaridae
halacarid mites, marine mites
Halacaridae is a family of meiobenthic mites comprising over 1,100 described species in 64 genera, representing the largest marine radiation of arachnids. Members occupy marine, brackish, and freshwater habitats worldwide, from intertidal zones to deep-sea hydrothermal vents. The family exhibits diverse feeding strategies including predation, algivory, scavenging, and parasitism.
Halacaroidea
halacarid mites, marine mites
Halacaroidea is a superfamily of mites within the order Trombidiformes, commonly known as halacarid or marine mites. This group comprises the only truly marine arachnids, having successfully colonized intertidal and subtidal habitats worldwide. Halacarids are microscopic predators and scavengers that inhabit marine environments ranging from coastal waters to abyssal depths, with some species also occurring in brackish and freshwater habitats.
Harpacticoida
Harpacticoid Copepods
Harpacticoida is an order of benthic copepods comprising approximately 463 genera and 3,000 species. Members are predominantly marine but include freshwater families (Ameiridae, Parastenocarididae, Canthocamptidae). They represent the second-largest meiofaunal group in marine sediments after nematodes and are also common in Arctic and Antarctic sea ice. A few species are planktonic or live in association with other organisms.
Microcerberidea
Cerberuses and Pillslaters
Microcerberidea is a suborder of minute isopod crustaceans established by Lang in 1961. Members are among the smallest isopods, measuring less than 2 mm in length. They inhabit interstitial spaces in marine sediments across tropical and subtropical coastal regions.
Ostracoda
Ostracods, Seed Shrimp
Ostracoda are small bivalved crustaceans, typically 0.5-2 mm in length, characterized by a hinged carapace that completely encloses the body. They exhibit remarkable diversity with over 33,000 described species and an estimated 70,000 total species when fossil forms are included. The group occupies virtually all aquatic environments from deep ocean trenches to temporary freshwater pools, with some species adapted to moist terrestrial microhabitats. Their calcified carapaces provide excellent fossil preservation, making them valuable for paleoecological and biostratigraphic studies.
Stygothrombidiidae
Stygothrombidiidae is a family of mites in the order Trombidiformes. Members are associated with subterranean freshwater habitats, particularly hyporheic zones and groundwater systems. The family is relatively small and poorly documented, with most known species placed in the genus Stygothrombium. These mites represent an example of adaptation to permanent darkness and interstitial aquatic environments.