Benthic
Guides
Ablabesmyia
Banded-leg Tanypods
Ablabesmyia is a genus of non-biting midges in the bloodworm family Chironomidae, comprising approximately 85 species distributed across multiple continents. Larvae are aquatic and frequently associated with aquatic vegetation, macrophytes, or detrital substrates in freshwater habitats. The genus is divided into four subgenera, with species documented from Europe, Asia, the Americas, and other regions. Adults are typically collected using light traps.
Acentrella
small minnow mayflies
Acentrella is a genus of small minnow mayflies in the family Baetidae. The genus contains at least 26 species distributed across Europe, North America, Asia, and Africa. Nymphs of at least some species inhabit cool, clean, swift rocky streams. Adult stages of several species remain undescribed due to the difficulty of rearing nymphs to maturity.
Achelous
Achelous is a genus of swimming crabs in the family Portunidae, established by De Haan in 1833. These marine brachyuran crabs are characterized by their flattened, streamlined bodies and modified fifth pereiopods adapted for swimming. The genus includes commercially significant species such as A. spinimanus, a fishery resource in southeastern Brazil, and A. hastatus, distributed across the Atlantic-Mediterranean region. Species within this genus exhibit habitat preferences related to sediment type and depth, with some showing age and sexual segregation patterns typical of portunid crabs.
Achelous spinimanus
Blotched Swimming Crab
Achelous spinimanus is a swimming crab native to the Western Atlantic, ranging from the USA to Brazil. It inhabits coastal marine environments from shallow waters to 90 m depth, with distinct depth preferences between life stages: juveniles occur at 5–35 m while adults are most abundant at 25 m and range to 40 m. The species exhibits continuous year-round reproduction with ovigerous females present in all seasons, and shows seasonal migration patterns in response to water temperature and salinity changes. It is an emerging fishery resource in Brazil, where it has become a target species following declines in more traditional catches.
Allocapnia
winter stoneflies
Allocapnia is a genus of small winter stoneflies in the family Capniidae, comprising at least 40 described species. Adults emerge during winter months, typically from December through March. Nymphs inhabit stream substrates and exhibit vertical movement within the hyporheic zone, often retreating to deeper substrate during summer diapause and returning to surface layers in autumn.
Ambrysus
creeping water bugs, saucer bugs
Ambrysus is a genus of creeping water bugs (family Naucoridae) containing more than 90 described species. These aquatic insects are found primarily in running streams across the New World, from northern North America to Argentina, with greatest diversity in Mexico. They possess flattened, rounded bodies and powerful claws for clinging to rocks in turbulent water. The genus includes two subgenera: Ambrysus (Syncollus) and Ambrysus (Ambrysus).
Amphiporeia
Amphiporeia is a genus of gammaridean amphipods in the family Bathyporeiidae, comprising at least three described species: A. gigantea, A. lawrenciana, and A. virginiana. These small crustaceans are characteristic inhabitants of sandy marine and estuarine substrates along the Atlantic coast of North America, where they exhibit specialized burrowing behavior and tidal swimming activity. The genus is notable for pronounced sexual segregation within the sediment, seasonal population fluctuations, and reproductive strategies involving multiple broods per year. Species within Amphiporeia function as important components of benthic food webs, serving as both detritivores and prey for demersal fish.
Anisogammaridae
Anisogammaridae is a family of small benthic amphipod crustaceans endemic to the northern Pacific Rim. The family includes freshwater, estuarine, and marine species distributed across the Japanese Archipelago, Korean Peninsula, Chinese mainland, and Pacific coast of North America. Members exhibit diverse life history strategies including annual winter-breeding cycles in temperate freshwater habitats and bivoltine patterns in estuarine environments. The family is notable for containing the most diverse group of Japanese freshwater amphipods (genus Jesogammarus) and species of conservation concern due to restricted ranges and habitat vulnerability.
Anomura
anomurans, hermit crabs, king crabs, porcelain crabs, squat lobsters, mole crabs, blanket-hermit crabs
Anomura is an infraorder of decapod crustaceans distinguished by their 'differently-tailed' body plan, including hermit crabs, king crabs, porcelain crabs, squat lobsters, and mole crabs. Multiple lineages within this group have independently evolved crab-like body forms through carcinisation. Anomura is the sister group to Brachyura (true crabs), together forming the clade Meiura. Members possess ten pereiopods, but the last pair is reduced and often concealed within the gill chamber, leaving only eight visible walking legs—a key diagnostic feature separating them from true crabs.
Apsectrotanypus johnsoni
Apsectrotanypus johnsoni is a species of non-biting midge in the family Chironomidae, subfamily Tanypodinae. It was described by Coquillett in 1901. As a member of the tribe Macropelopini, it belongs to a group of predatory midges whose larvae inhabit aquatic environments. The species is documented in the Catalogue of Life and GBIF as an accepted taxon, with 25 observations recorded on iNaturalist.
Asellota
Asellotes
Asellota is a suborder of isopod crustaceans comprising approximately one-quarter of all marine isopods. The group exhibits remarkable ecological diversity, occurring in marine, freshwater, and subterranean habitats from shallow coastal waters to abyssal depths, including hydrothermal vents. Members possess distinctive morphological specializations including a complex copulatory apparatus that distinguishes them from other isopods. The suborder has undergone multiple independent colonizations of deep-sea environments, with some lineages showing extensive radiation in these habitats.
Bathyporeiidae
Bathyporeiidae is a family of amphipod crustaceans containing two genera: Amphiporeia and Bathyporeia. These small, laterally compressed marine invertebrates are primarily known from shallow coastal waters of northern Europe. The family was formally established by d'Udekem d'Acoz in 2011.
Benthalia
Benthalia is a genus of non-biting midges in the family Chironomidae, established by Lipina in 1939. The genus is currently treated as a synonym of Einfeldia in the Catalogue of Life, reflecting ongoing taxonomic revision in the Chironomini tribe. Species historically placed in Benthalia are primarily benthic, inhabiting the bottom sediments of aquatic environments.
Calappidae
Box Crabs
Calappidae is a family of marine crabs commonly known as box crabs, comprising approximately 16 genera including both extant and fossil taxa. Seven genera are known only from the fossil record, with calappid fossils documented from the Cretaceous to Recent (66.043 Ma to present) across Europe, the United States, Mexico, Central America, Australia, and Japan. The family is characterized by a distinctive box-like carapace morphology and is distributed in tropical and temperate marine waters worldwide.
Callipallenidae
sea spiders
Callipallenidae is a family of sea spiders (Pycnogonida) established by Hilton in 1942. The family includes multiple genera distributed across Antarctic, subantarctic, and temperate waters, with notable species richness in southern Australian and Tasmanian waters. Some genera, such as Pallenella, exhibit exceptional sympatric diversity with multiple species co-occurring in the same microhabitat. Members of this family are generally small to medium-sized pycnogonids found in marine benthic environments.
Cancer productus
Red Rock Crab, Pearl of the Pacific Northwest
A large, commercially harvested crab native to the eastern Pacific coast of North America. Adults display distinctive brick-red coloration with large pincers bearing black tips. The species inhabits intertidal to subtidal waters and is an opportunistic carnivore, feeding on barnacles, small crabs, and fish. It is subject to sport and commercial fisheries, particularly in California and Washington.
Caprella verrucosa
Caprella verrucosa is a marine amphipod species in the family Caprellidae, commonly known as skeleton shrimp. The species was described by Boeck in 1871. It is found in temperate Asian waters, with confirmed records from the South Korean part of the Yellow Sea. Like other caprellids, it exhibits a reduced body plan with elongated pereiopods adapted for clinging to substrates in marine environments.
Carpias
Carpias is a genus of small marine isopods in the family Janiridae, established by Richardson in 1902. Members of this genus belong to the suborder Asellota, a diverse group of mostly benthic crustaceans. The genus contains multiple described species found in marine environments. Records of this genus in biodiversity databases remain limited, with few documented observations.
Cassidinidea ovalis
Cassidinidea ovalis is a species of isopod crustacean in the family Sphaeromatidae. Originally described by Thomas Say in 1818 as Naesa ovalis, this species has been reclassified into the genus Cassidinidea. The genus Cassidinidea is part of the sphaeromatid isopods, a group commonly known as pill bugs or sow bugs, though this particular genus tends toward more elongated, less strongly convex body forms than the classic 'pill bug' shape.
Ceraclea
long-horned caddisfly
Ceraclea is a genus of long-horned caddisflies (family Leptoceridae) containing over 140 described species. Larvae are aquatic and construct portable cases using silk and various materials. Multiple species have been documented as freshwater sponge specialists, though feeding habits vary including detritivory. Life cycles range from univoltine to more complex multi-cohort patterns with variable overwintering strategies.
Cheumatopsyche
Little Sister Sedges
Cheumatopsyche is a large genus of net-spinning caddisflies comprising at least 240 described species. Larvae construct silk capture nets to filter food from flowing water and are important components of freshwater benthic communities. Species exhibit variable life histories including univoltine and multivoltine cycles, with some populations capable of producing additional generations when thermal conditions permit. The genus is widely distributed across multiple continents and serves as a significant bioindicator for water quality assessment.
Choroterpes
Choroterpes is a genus of mayflies in the family Leptophlebiidae, distributed across the Americas, Europe (excluding the British Isles), Africa, and Asia. The genus contains multiple subgenera, including the nominate subgenus Choroterpes and Neochoroterpes (North America). Nymphs are typically found in streams and rivers, often associated with leaf litter. The genus has been subject to taxonomic revision, with some species reassigned to new genera such as Tikuna.
Chydorus
Chydorus is a genus of small benthic-littoral cladocerans in the family Chydoridae, established by William Elford Leach in 1816. Species in this genus are characterized by rounded, often reticulated carapaces and are among the most common anomopods in freshwater systems worldwide. The genus exhibits cosmopolitan distribution with multiple centers of diversification in Europe and Asia, and includes ecologically significant species such as Chydorus sphaericus, which dominates eutrophic waters and plays important roles in food web dynamics involving cyanobacteria.
Cirolanidae
Cirolanidae is a family of aquatic isopod crustaceans established by Dana in 1852. The family encompasses approximately 70 genera and over 500 species, ranging from small interstitial forms to the supergiant deep-sea isopods of the genus Bathynomus that can exceed 30 cm in length. Members occupy diverse aquatic habitats including marine coastal waters, deep-sea environments, freshwater systems, and subterranean groundwater. The family is characterized by dorsoventrally flattened bodies and includes both free-living and troglobitic species.
Corynoneura lobata
Corynoneura lobata is a species of non-biting midge in the family Chironomidae, subfamily Orthocladiinae. First described by Edwards in 1924, this species belongs to a genus of small chironomids characterized by reduced wing venation and distinctive genitalic structures. The genus Corynoneura is taxonomically complex, with numerous species described from multiple biogeographic regions. C. lobata has documented distribution records in northern Europe.
Crangonidae
crangonid shrimps, sand shrimps, brown shrimps
Crangonidae is a family of marine shrimp in the superfamily Crangonoidea, containing 24 genera and including the commercially important species Crangon crangon, the common brown shrimp. Members are primarily benthic, inhabiting coastal to deep-water sediments. The family is distinguished by partially chelate first pereiopods used in prey capture. Two fossil species are known: Crangon miocenicus from the early Miocene of Russia and Morscrangon acutus from the early Eocene of Denmark.
Einfeldia
non-biting midges
Einfeldia is a genus of non-biting midges in the subfamily Chironominae, tribe Chironomini, within the bloodworm family Chironomidae. The genus was established by Kieffer in 1924 and contains approximately 11 described species distributed across Europe, North America, and other regions. At least one species, E. synchrona, has been studied in detail and exhibits univoltine life history with synchronized adult emergence.
Epeorus longimanus
flatheaded mayfly
Epeorus longimanus is a flatheaded mayfly species in the family Heptageniidae. Nymphs inhabit stream riffles and show specific microhabitat preferences, being more abundant in areas with smaller sediment sizes, higher live periphyton biomass, and lower densities of invertebrate predators. The species is distributed across western North America from Alaska through the western United States to southwestern and northern Canada.
Ephemera blanda
common burrower mayfly
Ephemera blanda is a species of burrower mayfly in the family Ephemeridae, characterized by its fossorial lifestyle in aquatic sediments. The species inhabits running waters in the southeastern Nearctic region. As with other members of the genus Ephemera, adults are short-lived and primarily focused on reproduction.
Ephemerella
Hendricksons, Sulphurs, Pale Duns
Ephemerella is a genus of spiny crawler mayflies comprising approximately 19 described species. Nymphs are characterized by their distinctive defensive posture, curling the abdomen upward in a scorpion-like manner when disturbed. The genus has a widespread distribution across North America and Europe, with species occupying diverse lotic freshwater habitats. Several species, including E. subvaria and E. ignita, have been subjects of detailed life history studies.
Ephemeridae
Burrowing Mayflies
Ephemeridae is a family of large mayflies comprising approximately 150 described species distributed worldwide except Australia and Oceania. Adults range up to 35 mm in length and possess either two or three elongated caudal filaments. Many species exhibit distinctively patterned wings. The family is commonly known as "burrowing mayflies" due to the fossorial adaptations of their nymphs, which inhabit silty or sandy substrates in freshwater systems. Nymphs possess specialized morphological features including spur-like projections on foretibiae, dorsally positioned plumose and lanceolate abdominal gills, and mandibular tusks that facilitate burrowing behavior.
Ericthonius
Ericthonius is a genus of marine amphipod crustaceans in the family Ischyroceridae, first described by H. Milne Edwards in 1830. The genus contains at least 20 described species, with records from marine coastal waters of northern Europe. These small crustaceans are part of the diverse benthic communities inhabiting shallow marine environments.
Gammarus mucronatus
scud
Gammarus mucronatus is a small amphipod crustacean first described in 1818. It is a dominant species in salt marsh and estuarine habitats along the North American Atlantic coast and Gulf of Mexico. The species is multivoltine, producing multiple broods per season with overlapping cohorts. It serves as an important food source for fish and other predators while contributing significantly to energy flow and nutrient cycling in coastal ecosystems.
Habrophlebia vibrans
pronggilled mayfly
A small stream-dwelling mayfly with a 2-year life cycle, notable for its extended development compared to most mayflies. Adults emerge synchronously in June. Nymphs inhabit gravel substrates and show distinct drift patterns across life stages. The species has been studied in Québec populations, where it reaches final sizes of approximately 5 mm before emergence.
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.
Hepatus epheliticus
Dolly Varden Crab, calico crab, calico box crab, Gulf calico crab
Hepatus epheliticus is a small crab species reaching 76 mm in carapace width, distinguished by its distinctive red-spotted coloration. It inhabits shallow coastal waters of the western Atlantic Ocean from Chesapeake Bay to the Dominican Republic, including the entire Gulf of Mexico. The species is notable for its association with the sea anemone Calliactis tricolor, which it frequently carries on its carapace.
Heterocloeon curiosum
curious small minnow mayfly
Heterocloeon curiosum is a small minnow mayfly in the family Baetidae, native to North America. It has been studied in Virginia river systems, where it demonstrates bivoltine life history with two summer generations. Reservoir construction with surface release can significantly alter its emergence timing, larval density, and fecundity through thermal regime changes.
Homarus americanus
American lobster, Atlantic lobster, Canadian lobster, true lobster, northern lobster, Canadian Reds, Maine lobster
Homarus americanus is a large marine crustacean found on the Atlantic coast of North America. It is the heaviest crustacean in the world, capable of exceeding 20 kg and 64 cm body length. The species is commercially important, supporting major fisheries from Labrador to New Jersey. It inhabits benthic environments from shallow coastal waters to depths exceeding 700 meters.
Hyalella
Hyalella is a genus of freshwater amphipods found in the Americas, with species distributed across North, Central, and South America. The genus contains numerous endemic species, particularly in South America, and includes the widely studied H. azteca, which serves as a standard test organism in aquatic toxicology. Members occupy benthic habitats in lakes, streams, and springs, where they function as important components of freshwater food webs.
Hyalella wellborni
Hyalella wellborni is a freshwater amphipod species in the family Hyalellidae, described in 2015 from the southeastern United States. The genus Hyalella comprises small benthic crustaceans commonly known as scuds or sideswimmers, widespread in lakes, ponds, and streams. H. wellborni represents part of a taxonomically complex group where species delineation has historically relied on morphological and molecular analyses. The species is known from a limited number of observations, reflecting both its relatively recent description and the ongoing challenges in amphipod taxonomy.
Hydrozetes
Beetle Mites
Hydrozetes is a genus of aquatic oribatid mites (family Hydrozetidae) distinguished by being obligately associated with freshwater habitats. All species in this genus are aquatic, occurring on water surfaces and in benthic zones of lakes, ponds, and other water bodies. The genus has been documented from the Paleocene fossil record through to extant populations across multiple continents. Some species achieve extremely high population densities, dominating benthic invertebrate communities in temporary and permanent water bodies.
Ilyocryptus
water fleas
Ilyocryptus is a genus of freshwater cladocerans (water fleas) in the family Ilyocryptidae. Species in this genus are characterized by a benthic lifestyle, inhabiting lake sediments and muddy substrates. The genus has a global distribution with notable diversity in the Neotropics and Far East. Several species groups have been identified, including the widespread I. spinifer group and the sarsi-group, with some taxa showing complex biogeographic patterns across transitional zones between boreal and tropical regions.
Janiridae
Janiridae is a globally distributed family of marine isopods in the suborder Asellota, comprising over 170 species across approximately 23 genera. The family exhibits remarkable bathymetric range, from intertidal zones to hadal depths exceeding 6,000 meters. Most species inhabit shallow shelf waters within 100 meters depth, though several genera have colonized deep-sea environments including whale falls, hydrothermal vents, and abyssal plains. The genus *Jaera*, predominantly northern hemisphere in distribution, includes the notable deep-sea specialist *Jaera tyleri*, discovered on whale bones in the Southern Ocean at 1,445 meters depth—the first *Jaera* species documented in the southern hemisphere. Janiridae demonstrates broad environmental tolerance to salinity, temperature, and oxygen stress.
Janiroidea
Witchers
Janiroidea is a superfamily of marine isopods in the suborder Asellota, established by G. O. Sars in 1897. It comprises 25 families, with Paramunnidae and Munnidae as the two largest and most diverse. Members occupy a remarkable depth range from shallow littoral zones to hadal trenches exceeding 8,000 meters. The superfamily exhibits substantial morphological diversity, including adaptations for interstitial, benthic, and deep-sea habitats.
Labiobaetis
Labiobaetis is a genus of small mayflies in the family Baetidae, comprising over 150 described species distributed across tropical and temperate regions worldwide. The genus exhibits exceptional diversity in Southeast Asia, New Guinea, and Indonesia, with significant representation also in Africa, India, and western North America. Species identification relies primarily on larval morphology, particularly characters of the mouthparts, antennae, and gills. Adults are generally difficult to distinguish at the generic level.
Leptohyphes
little stout crawler mayflies
Leptohyphes is a genus of small, robust mayflies in the family Leptohyphidae, commonly referred to as "little stout crawler mayflies." The genus contains approximately 18 described species distributed primarily in the Neotropics, with a concentration in South America. Species in this genus are characterized by their crawling behavior and compact body form. The genus was established by Eaton in 1882.
Libinia emarginata
portly spider crab, common spider crab, nine-spined spider crab
Libinia emarginata is a heavily calcified spider crab native to the western Atlantic coast of North America. It is characterized by its triangular carapace, khaki coloration, and distinctive spiny appearance. The species exhibits unusual forward-walking locomotion rather than the typical sideways movement of most crabs. As a decorator crab, it frequently covers itself with debris and small invertebrates for camouflage.
Metretopodidae
cleftfooted minnow mayflies
Metretopodidae is a family of mayflies in the order Ephemeroptera, commonly known as cleftfooted minnow mayflies. The family contains at least 3 genera (Metreplecton, Metretopus, Siphloplecton) and more than 20 described species. These mayflies are part of the diverse aquatic insect fauna associated with freshwater habitats.
Neoephemeridae
large squaregill mayflies
Neoephemeridae is a small family of mayflies in the suborder Furcatergalia, containing approximately 13-17 described species across four genera: Neoephemera (Nearctic), Ochernova (Central Asia), Leucorhoenanthus (West Palearctic), and Potamanthellus (East Palearctic and Oriental). Nymphs are characterized by distinctive fimbriate (fringed) dorsal-oriented gills on abdominal segments, giving rise to the common name "large squaregill mayflies." The family has a disjunct Holarctic-Oriental distribution with recent findings in southwestern and northwestern China linking previously isolated genera biogeographically.
Odontoceridae
Mortarjoint Casemaker Caddisflies
Odontoceridae is a family of caddisflies (order Trichoptera) commonly known as mortarjoint casemakers. The family contains approximately 12 genera and at least 100 described species. Larvae are aquatic case-builders that typically construct cases from mineral particles such as sand and small stones. The family has a cosmopolitan distribution with representatives in North America, Europe, South America, and other regions. Adults are generally active during spring and summer months.