Onychopoda are a specialised order of

branchiopod Branchiopoda is a class of crustaceans. It comprises fairy shrimp, clam shrimp, Diplostraca (or Cladocera), Notostraca and the Devonian '' Lepidocaris''. They are mostly small, freshwater animals that feed on plankton and detritus. Descript ...

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapoda, decapods, ostracoda, seed shrimp, branchiopoda, branchiopods, argulidae, fish lice, krill, remipedes, isopoda, isopods, barnacles, copepods, ...

s, belonging to the superorder

Cladocera The Diplostraca or Cladocera, commonly known as water fleas, are a superorder of small crustaceans that feed on microscopic chunks of organic matter (excluding some predatory forms). Over 1000 species have been recognised so far, with many more ...

. The order Onychopoda is "one of the most morphologically distinctive groups of cladocerans". They have only four pairs of

legs A leg is a weight-bearing and locomotive anatomical structure, usually having a columnar shape. During locomotion, legs function as "extensible struts". The combination of movements at all joints can be modeled as a single, linear element c ...

, compared to five or six pairs in

Ctenopoda The Ctenopoda are an order of the superorder Diplostraca, comprising the three families Holopediidae, Pseudopenilidae, and Sididae. Its members mostly live in fresh water Fresh water or freshwater is any naturally occurring liquid or fro ...

and

Anomopoda Anomopoda is an order of the superorder Diplostraca. These crustaceans, a type of water flea, are members of the class Branchiopoda. The Anomopoda typically have five pairs of thoracic limbs, but sometimes have six pairs. The head of the Anomopo ...

. Unusually among branchiopod crustaceans, Onychopoda share with

Haplopoda ''Leptodora'' is a genus containing two species of large, nearly transparent predatory water fleas. They grow up to long, with two large antennae used for swimming and a single compound eye. The legs are used to catch copepods that it comes i ...

the presence of segmented appendages, which are used for grasping prey. Most species of Onychopoda live in the waters of the Ponto-Caspian basin (

Caspian Sea The Caspian Sea is the world's largest inland body of water, often described as the world's largest lake or a full-fledged sea. An endorheic basin, it lies between Europe and Asia; east of the Caucasus, west of the broad steppe of Central A ...

Aral Sea The Aral Sea ( ; kk, Арал теңізі, Aral teñızı; uz, Орол денгизи, Orol dengizi; kaa, Арал теңизи, Aral teńizi; russian: Аральское море, Aral'skoye more) was an endorheic lake lying between Kazak ...

Black Sea The Black Sea is a marginal mediterranean sea of the Atlantic Ocean lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bounded by Bulgaria, Georgia, Rom ...

including

Sea of Azov The Sea of Azov ( Crimean Tatar: ''Azaq deñizi''; russian: Азовское море, Azovskoye more; uk, Азовське море, Azovs'ke more) is a sea in Eastern Europe connected to the Black Sea by the narrow (about ) Strait of Ker ...

), in remnants of the ancient

Paratethys The Paratethys sea, Paratethys ocean, Paratethys realm or just Paratethys was a large shallow inland sea that stretched from the region north of the Alps over Central Europe to the Aral Sea in Central Asia. Paratethys was peculiar due to its p ...

ocean. Some other species live in

fresh water Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does incl ...

or in the

ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wor ...

s, where they can be widespread. There are three families, containing 10 genera and around 33 described species, most of which are

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

to the Ponto-Caspian basin: * Cercopagididae Mordukhai-Boltovskoi, 1968 – 2 genera ('' Cercopagis'' and '' Bythotrephes''), 14 species; Black Sea & Caspian Sea * Podonidae Mordukhai-Boltovskoi, 1968 – 7 genera, 17 species; Pont-Caspian ('' Caspievadne'', '' Cornigerius'' and '' Podonevadne'') and marine (''

Evadne In Greek mythology, Evadne (; Ancient Greek: Εὐάδνη) was a name attributed to the following individuals: *Evadne, a daughter of Strymon and Neaera, wife of Argus (king of Argos), mother of Ecbasus, Peiras, Epidaurus and Criasus. *Evadn ...

'', '' Pleopis'', '' Podon'' and '' Pseudevadne'') * Polyphemidae Baird, 1845 – 1 genus (''

Polyphemus Polyphemus (; grc-gre, Πολύφημος, Polyphēmos, ; la, Polyphēmus ) is the one-eyed giant son of Poseidon and Thoosa in Greek mythology, one of the Cyclopes described in Homer's ''Odyssey''. His name means "abounding in songs and ...

''), 2 species; fresh water The

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...

s are protected by a brood pouch, which also secretes

nutrient A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excre ...

s to aid their development. This may be related to the colonisation of the oceans, since the only other marine cladoceran, '' Penilia avirostris'', has a similar pouch as a result of

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...

References

External links

''Podon'' sp. fact sheet - Guide to the marine zooplankton of south eastern Australia

{{Taxonbar, from=Q2024726 Branchiopoda Arthropod orders

See also

References

External links