Deep-sea
Guides
Aegidae
aegid isopods
Aegidae is a family of marine and freshwater isopod crustaceans characterized by temporary parasitic relationships with fish hosts. Adults attach to hosts to feed on blood or tissue, then detach to digest meals. The family is distinguished from related Cirolanidae by having only three pairs of hook-like pereiopods rather than seven. Members occur in diverse aquatic habitats from shallow coastal waters to deep ocean environments, with some species documented at depths exceeding 2000 meters.
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.
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.
Bathynomus
Giant Isopods, Supergiant Isopods, Sea Bugs (Vietnamese: bọ biển)
Bathynomus is a genus of supergiant deep-sea isopods in the family Cirolanidae, containing nearly 20 described species. These crustaceans are among the largest isopods in the world, with some species exceeding 30 cm in length and 1 kg in weight. They inhabit cold, deep waters of the Atlantic, Pacific, and Indian Oceans, typically at depths of 400–2,300 m. Several species have become commercially fished as seafood, particularly in Vietnam, where they are known as "bọ biển" or "sea bugs."
Calliopiidae
Calliopiidae is a family of hyperbenthic amphipods distributed across the North Atlantic and North Pacific oceans. Members inhabit diverse marine environments including subtidal waters, hydrothermal vents, and the hyperbenthic zone immediately above the seafloor. The family includes the newly described genus Bathya from deep-sea hydrothermal vents and Calliopius species associated with macroalgae.
Caridea
caridean shrimp, true shrimp
Caridea is a species-rich infraorder of decapod crustaceans comprising over 3,000 described species of true shrimp. Members are distinguished from other shrimp groups by their brooding reproductive strategy, lamellar gill structure, and characteristic abdominal segmentation where the second segment overlaps both the first and third. They occupy diverse aquatic habitats from freshwater streams to abyssal depths exceeding 5,000 meters, with roughly one-quarter of species inhabiting freshwater environments. The group includes commercially significant species such as Pandalus borealis and ecologically important cleaner shrimp that maintain reef fish health.
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.
Decapoda
decapods, ten-footed crustaceans
Decapoda is the most species-rich order of Crustacea, with over 14,500 described extant species worldwide. Members include crayfish, crabs, lobsters, prawns, and shrimp—collectively known as decapods or "ten-footed" crustaceans. The order exhibits extraordinary morphological diversity, ranging from tiny symbiotic shrimps under one centimetre to large crabs and lobsters. Decapods occupy virtually every aquatic habitat on Earth, from deep-sea trenches exceeding 5,000 metres depth to terrestrial environments, with nearly half of all species being crabs. The order includes several infraorders with distinct body plans: Brachyura (true crabs), Caridea (shrimps), Anomura (hermit crabs and allies), and others.
Epicaridea
crustacean isopods
Epicaridea is a suborder of parasitic marine isopods now classified within Cymothoida. Members are obligate ectoparasites of other crustaceans, including ostracods, copepods, barnacles, and malacostracans. The group exhibits extreme sexual dimorphism, with females typically becoming asymmetrical and losing segmentation while males remain small and morphologically distinct. Development proceeds through regressive metamorphosis involving two or three larval stages, including the distinctive cryptoniscus stage. Approximately 704 species have been described globally, though the group remains less studied than other isopod lineages.
Flexamia huroni
Huron River Leafhopper
Flexamia huroni is a leafhopper species in the family Cicadellidae, described by Bess & Hamilton in 1999. It belongs to the genus Flexamia, a group of leafhoppers known for their specialized host plant associations with grasses. The species is named after the Huron River in Michigan, where it was first collected. Like other members of the genus, it likely exhibits strong ecological dependence on specific grass host plants.
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n-species
Gabara n-species is a newly described marine gastropod mollusk documented in the Ocean Species Discoveries publication series coordinated by the Senckenberg Ocean Species Alliance. The species was among 14 new marine invertebrate species described in a 2025 collaborative effort involving over 20 researchers. The publication aimed to accelerate formal taxonomic description to prevent species from going extinct before being scientifically recognized.
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.
Isopoda
isopods, woodlice, pillbugs, sowbugs, sea slaters, gribbles
Isopoda is an ancient order of crustaceans encompassing over 10,000 described species across marine, freshwater, and terrestrial habitats. Members are characterized by dorsoventrally flattened bodies, seven pairs of similar walking legs (giving the group its name from Greek iso- "equal" and pod- "foot"), and two pairs of antennae. The order exhibits exceptional morphological diversity, ranging from minute interstitial forms to giant deep-sea species exceeding 30 cm in length. Isopods lack a carapace, instead possessing overlapping dorsal plates that provide flexibility and protection. Females brood eggs in a specialized marsupium formed by oostegites under the thorax.
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.
Lithodidae
King Crabs, Stone Crabs
Lithodidae is a family of large, cold-water decapod crustaceans commonly known as king crabs or stone crabs. Members possess a crab-like body form within the otherwise hermit crab-associated infraorder Anomura, representing an independent evolutionary transition to the crab morphology. The family includes commercially important species such as the red king crab (Paralithodes camtschaticus) and encompasses both deep-water and intertidal habitats across cold seas of the Northern and Southern Hemispheres.
Munididae
Munidid Squat Lobsters
Munididae is a family of squat lobsters (Decapoda: Anomura) taxonomically separated from Galatheidae in 2010. Members are predominantly deep-water taxa distinguished by a trispinose frontal edge to the carapace, a central rostrum, and two spines extending forward from above the eyes. The family exhibits substantial cryptic diversity, with species often distinguishable only by subtle morphological differences in telson shape and pereopod dactyli. Reproductive strategies vary, with Munididae typically producing numerous small eggs compared to related families.
Oncaeidae
Oncaeidae is a family of microcopepods characterized by small body size, high abundance, and high species diversity across all ocean basins. The family was established by Giesbrecht in 1893 and comprises approximately 115 described species across seven genera. Members occur from surface waters to bathypelagic depths, exhibiting a life strategy fundamentally different from most other pelagic microcopepod families. Their ecological role in marine ecosystems remains incompletely understood despite their numerical importance.
Paguroidea
hermit crabs
Paguroidea is a superfamily of decapod crustaceans comprising approximately 1100 species commonly known as hermit crabs. Members are characterized by a soft, asymmetrical abdomen adapted to occupy empty gastropod shells or, in specialized lineages, symbiotic relationships with sea anemones that form protective 'blankets' or 'carcinoecia'. The superfamily exhibits remarkable diversity in shell-use strategies, from traditional gastropod shells to bivalve shells and anemone-derived structures. Distributed across marine environments from intertidal zones to deep-sea habitats, with some lineages having colonized terrestrial ecosystems.
Pandalidae
pandalid shrimp
Pandalidae is a family of caridean shrimp commonly known as pandalid shrimp, characterized by two distinctive morphological features: a subdivided carpus on the second pereiopod and the absence of chelae (claws) on the first pereiopod. Members of this family are predominantly cold-water species, with tropical representation occurring primarily through deep-sea forms. The family holds significant commercial value, as many species are edible and support important fisheries. The genus Physetocaris, formerly included in Pandalidae, has been reclassified into its own family Physetocarididae.
Paralithodes rathbuni
spiny king crab, California king crab
Paralithodes rathbuni is a deep-sea king crab in the family Lithodidae, commonly known as the spiny king crab or California king crab. It inhabits the continental shelf and slope off the coast of California and Baja California at depths of 86–380 meters. The species is closely related to P. californiensis, with which it shares the common name "California king crab," and some authorities have suggested the two may be conspecific.
Phronima
Phronima is a genus of small, deep-sea hyperiid amphipods found throughout the world's oceans except polar regions. These semitransparent pelagic crustaceans are technically parasitoids rather than parasites: females attack salps, hollow out their gelatinous tunicates to create protective 'barrels,' and rear their young inside these structures. The genus possesses extraordinary compound eyes adapted to detect blue-green wavelengths, enabling navigation in dim mid-ocean environments where bioluminescence serves as critical ecological signals. Phronima has gained cultural recognition as a possible inspiration for the Alien Queen design in the 1986 film 'Aliens.'
Pleuroncodes planipes
pelagic red crab, tuna crab, squat lobster, langostilla, benthic anomuran red crab
Pleuroncodes planipes is a pelagic and benthic anomuran red crab distributed across the eastern Pacific Ocean, from California to Panama. The species exhibits a complex life cycle with both pelagic and benthic phases: larvae and small individuals occupy open waters, while larger adults become exclusively benthic. It forms exceptionally dense aggregations on seamounts, with recorded densities up to 78 crabs/m² at depths of 355–385 m. The species tolerates hypoxic conditions (0.04 ml/l oxygen) and serves as a major prey item for large pelagic predators including yellowfin and skipjack tuna.
Seroloidea
Seroloidea is a superfamily of marine isopod crustaceans within the suborder Sphaeromatidea. It comprises six families, four of which are extant and two extinct. The superfamily was established by Dana in 1852. Seroloidea is distinguished from other sphaeromatidean superfamilies by unique morphological characteristics of its constituent families, particularly the Serolidae.
Stenopodidae
Coral Shrimps, Boxer Shrimp
Stenopodidae is a family of marine decapod crustaceans comprising approximately 6 genera and more than 30 described extant species. The family has a fossil record extending to the Devonian period. Members are commonly known as coral shrimps or boxer shrimp and are distinguished from true shrimp and prawns by morphological and phylogenetic affinities closer to reptant decapods such as lobsters and crabs. The family exhibits diverse ecological associations including fish cleaning symbioses, commensalism with deep-water corals, and obligate associations with hexactinellid sponges.
Stenopodidea
Coral and Glass Sponge Shrimps, Boxer Shrimps
Stenopodidea is a small infraorder of decapod crustaceans comprising 71 extant species in 12 genera, commonly known as coral and glass sponge shrimps or boxer shrimps. Despite their common names, they are distinct from both Caridea (true shrimp) and Dendrobranchiata (prawns), representing a separate lineage within Pleocyemata more closely related to reptant decapods such as lobsters and crabs. Members are characterized by a greatly enlarged third pair of pereiopods, non-branching gills, and egg-brooding reproduction. The group includes three fossil species, with the earliest known from the Devonian period.
Synaptotanais
Synaptotanais is a genus of tanaidacean crustaceans in the family Tanaididae, established by Sieg in 1980. The genus contains at least two described species: Synaptotanais abyssorum, described from deep-sea habitats in 1913, and Synaptotanais notabilis, described in 1981. As members of Tanaididae, these are small, benthic peracarid crustaceans.
Unciolidae
Unciolidae is a family of marine amphipod crustaceans comprising approximately 9 genera and over 20 described species. The family has a worldwide distribution with records from deep-sea environments in the North Atlantic and shallow tropical waters such as the Great Barrier Reef. Members of this family exhibit diverse habitat preferences, from abyssal depths exceeding 2000 meters to coastal reef systems.