Poecilostomatoida are an suborder of

copepods Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat. Some species are planktonic (inhabiting sea waters), some are benthic (living on the ocean floor), a number of species have p ...

. Although it was previously considered a separate order, recent research showed it to be nested within the Cyclopoida

Description

The classification of these copepods has been established on the basis of the structure of the mouth. In poecilostomatoids the mouth is represented by a transverse slit, partially covered by the overhanging labrum which resembles an upper lip. Although there is variability in the form of the

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

among poecilostomatoids, it can be generalized as being falcate (

sickle A sickle, bagging hook, reaping-hook or grasshook is a single-handed agricultural tool designed with variously curved blades and typically used for harvesting, or reaping, grain crops or cutting Succulent plant, succulent forage chiefly for feed ...

-shaped). The

antennule Antennae ( antenna), sometimes referred to as "feelers", are paired appendages used for sensing in arthropods. Antennae are connected to the first one or two segments of the arthropod head. They vary widely in form but are always made of one ...

s are frequently reduced in size and the

antenna Antenna ( antennas or antennae) may refer to: Science and engineering * Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves * Antennae Galaxies, the name of two collid ...

e modified to terminate in small hooks or claws that are used in attachment to host organisms.

Life cycle

As with many crustaceans,

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. ...

l development is

metamorphic Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causi ...

with immature forms differing greatly from those of adults. Embryos are carried in paired or single sacs attached to first abdominal somite (as seen in the illustration of the female '' Sapphirina darwinii'' above right).

Ecology

Most poecilostomatoid copepods are

ectoparasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

s of saltwater

fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. Included in this definition are the living hagfish, lampreys, and Chondrichthyes, cartilaginous and bony fish as we ...

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chorda ...

s (including among the latter

mollusks Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

and

echinoderm An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the ...

s). They usually attach to the external surface of the host, in the throat-mouth cavity, or the

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they ar ...

s. One family of poecilostomatoid copepods, however, have evolved an endoparasitic mode of life and live deep within their hosts' bodies rather than merely attaching themselves to exterior and semi-exterior surface tissue. In addition to typical marine environments, poecilostomatoid copepods may be found in such very particular

habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...

s as anchialine caves and deep sea vents (both

hydrothermal vents A hydrothermal vent is a fissure on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hotspo ...

and cold seeps). Here, many primitive associated copepods belonging to the Poecilostomatoida and Siphonostomatoida and have been found. Representatives of one Poecilostomatoida family have successfully made the transition to

freshwater 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 ...

habitats and host animals therein. Oncaea venusta

List of families

There are over sixty families currently recognized within the group: * Abrsiidae * Anchimolgidae * Anomoclausiidae * Antheacheridae * Anthessiidae * Bomolochidae * Bradophilidae * Catiniidae *

Chondracanthidae Chondracanthidae is a family of parasitic copepods, usually found infecting the branchial chamber of demersal fishes. It comprises the following genera: *'' Acanthocanthopsis'' Heegaard, 1945 *'' Acanthochondria'' Oakley, 1930 *'' Acanthochondri ...

* Clausidiidae * Clausiidae * Corallovexiidae * Corycaeidae * Echiurophilidae * Entobiidae * Erebonasteridae * Ergasilidae * Eunicicolidae * Gadilicolidae * Gastrodelphyidae * Herpyllobiidae * Intramolgidae * Iveidae * Jasmineiricolidae * Kelleriidae * Lamippidae * Leaniricolidae * Lichomolgidae * Lubbockiidae * Macrochironidae * Makrostrotidae * Mesoglicolidae * Myicolidae * Mytilicolidae * Nereicolidae * Octopicolidae * Oncaeidae * Paralubbockiidae * Philichthyidae * Philoblennidae * Phyllodicolidae * Pionodesmotidae * Polyankyliidae * Pseudanthessiidae * Rhynchomolgidae * Sabelliphilidae * Saccopsidae * Sapphirinidae * Serpulidicolidae * Shiinoidae * Spiophanicolidae * Splanchnotrophidae * Strepidae * Synapticolidae * Synaptiphilidae * Taeniacanthidae * Telsidae * Thamnomolgidae * Tuccidae * Umazurcolidae * Urocopiidae * Vahiniidae * Ventriculinidae * Xarifiidae * Xenocoelomatidae

References

External links

* * {{Taxonbar, from=Q2344407 Copepods Arthropod suborders