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Isopoda

(Order)

Overview

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Isopods are an order of peracarid crustaceans, including familiar animals such as woodlice and pill bugs. The name Isopoda derives from the Greek roots (iso-, meaning "same") and p?d?? (podos, meaning "foot").[1] The fossil record of isopods dates back to the Carboniferous period (in the US Pennsylvanian epoch), at least 300 million years ago.[2][3]

Description

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The woodlouse Oniscus asellus from the side

Isopods are relatively small crustaceans with seven pairs of legs of similar size and form, ranging in size from 300 micrometres (0.012 in) to nearly 50 centimetres (20 in) in the case of Bathynomus giganteus.[1] They are typically flattened dorso-ventrally, although many species deviate from this plan, particularly those from the deep sea or from ground water.[1] Isopods lack an obvious carapace, which is reduced to a "cephalic shield" covering only the head.[4] Gas exchange is carried out by specialised gill-like pleopods towards the rear of the animal's body. In terrestrial isopods, these are often adapted into structures which resemble lungs, and these "lungs" are readily visible on the underside of a woodlouse.[1] Eyes, when present, are always sessile, never on stalks.[4] They share with the Tanaidacea the fusion of the last abdominal body segment with the telson, forming a "pleotelson",[4] and the first body segment of the thorax is fused to the head. The pereiopods are uniramous, but the pleopods are biramous.[4]

Ecology

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Anilocra (Cymothoidae) parasitising Spicara maena, Italy

Around 4,500 species of isopods are found in marine environments, mostly on the sea floor.[2] Some 500 species are found in fresh water; and another 5,000 species are the woodlice in the suborder Oniscidea, which are thus by far the most successful group of terrestrial crustaceans.[2] In the deep sea, me mbers of the suborder Asellota predominate, to the near exclusion of all other isopods, having undergone a large adaptive radiation in that environment.[2]

A number of isopod groups have evolved a parasitic lifestyle. The suborder Cymothoida is exclusively parasitic, while the polyphyletic suborder Flabellifera is partly parasitic. Cymothoa exigua, for example, is a parasite of the spotted rose snapper fish Lutjanus guttatus in the Gulf of California; it eats the tongue of the fish, and takes its place, in the only known instance of a parasite functionally replacing a host structure.[5]

In marine and reef aquariums, parasitic isopods can become a pest, endangering both the fish and the aquarium keepers.[6]

Diversity and classification

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Isopods belong to the larger group Peracarida, which are united by the presence of a special brood pouch for brooding eggs. There are around 10,215 described species of isopod,[1] classified into eleven suborders.[7]

Development

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Isopod larvae hatch as mancae, which resemble adults except for the lack of the last pair of pereiopods (thoracic legs). The lack of a swimming phase in the life cycle is a limiting factor in isopod dispersal, and may be responsible for the high levels of endemism in the order.[2] As adults, isopods differ from other crustaceans in that they replace their exoskeleton (in the process called ecdysis) in two phases; this is known as "biphasic moulting".[1]

sion of all other isopods, having undergone a large adaptive radiation in that environment.[2]

A number of isopod groups have evolved a parasitic lifestyle. The suborder Cymothoida is exclusively parasitic, while the polyphyletic suborder Flabellifera is partly parasitic. Cymothoa exigua, for example, is a parasite of the spotted rose snapper fish Lutjanus guttatus in the Gulf of California; it eats the tongue of the fish, and takes its place, in the only known instance of a parasite functionally replacing a host structure.[5]

In marine and reef aquariums, parasitic isopods can become a pest, endangering both the fish and the aquarium keepers.[6]

Diversity and classification

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Isopods belong to the larger group Peracarida, which are united by the presence of a special brood pouch for brooding eggs. There are around 10,215 described species of isopod,[1] classified into eleven suborders.[7]

Development

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Isopod larvae hatch as mancae, which resemble adults except for the lack of the last pair of pereiopods (thoracic legs). The lack of a swimming phase in the life cycle is a limiting factor in isopod dispersal, and may be responsible for the high levels of endemism in the order.[2] As adults, isopods differ from other crustaceans in that they replace their exoskel eton (in the process called ecdysis) in two phases; this is known as "biphasic moulting".[1]

References

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  1. ^ a b c d e f M. Schotte, C. B. Boyko, N. L. Bruce, J. Markham, G. C. B. Poore, S. Taiti & G. D. F. Wilson. "World List of Marine, Freshwater and Terrestrial Isopod Crustaceans". World Register of Marine Species. http://www.marinespecies.org/isopoda/index.php. Retrieved October 7, 2010. 
  2. ^ a b c d e Richard Brusca (August 6, 1997). "Isopoda". Tree of Life Web Project. http://tolweb.org/Isopoda/6320/1997.08.06. 
  3. ^ Frederick R. Schram (1970). "Isopod from the Pennsylvanian of Illinois". Science 169 (3948): 854?855. doi:10.1126/science.169.3948.854. PMID 5432581. 
  4. ^ a b c d S. J. Keable, G. C. B. Poore & G. D. F. Wilson (October 2, 2002). "Australian Isopoda: Families". Australian Museum. http://www.crustacea.net/crustace/isopoda/index.htm. 
  5. ^ R. C. Brusca & M. R. Gilligan (1983). "Tongue replacement in a marine fish (Lutjanus guttatus) by a parasitic isopod (Crustacea: Isopoda)". Copeia 3 (3): 813?816. doi:10.2307/1444352. JSTOR 1444352. 
  6. ^ Ronald L. Shimek (2002). "Pills, parasites, and predators; isopods in the reef aquarium". Reefkeeping 1 (4). http://reefkeeping.com/issues/2002-05/rs/index.php. 
  7. ^ Joel W. Martin & George E. Davis (2001) (PDF). An Updated Classification of the Recent Crustacea. Natural History Museum of Los Angeles County. pp. 132 pp. http://atiniui.nhm.org/pdfs/3839/3839.pdf. 

External links

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Taxonomy

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The Order Isopoda is further organized into finer groupings including:

Families

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Acanthaspidiidae

[more]

Actaeciidae

[more]

Aegidae

Aegidae is a family of isopod crustaceans, containing the following genera: [more]

Agnaridae

Agnaridae is a family of woodlice. They were formerly considered part of the , but were moved from that family to Porcellionidae in 1989, and then placed as a separate family in 2003. There are c.?80 species, distributed from the Mediterranean basin to East Asia. [more]

Alloniscidae

[more]

Amphisopodidae

[more]

Ancinidae

[more]

Antarcturidae

[more]

Antheluridae

[more]

Anthuridae

[more]

Anuropidae

[more]

Arcturidae

[more]

Arcturididae

[more]

Armadillidae

[more]

Armadillidiidae

Armadillidiidae is a family of woodlice, a terrestrial crustacean group in the order Isopoda. Unlike members of other woodlouse families, members of this family can roll into a ball, an ability they share with the outwardly similar but unrelated pill millipedes and other animals. It is this ability which gives woodlice in this family their common name of pill bugs, roly polies or potato bugs. The best known species in the family is Armadillidium vulgare, the common pill bug. [more]

Asellidae

Asellidae is a family of isopod crustaceans. It is one of the largest families of freshwater isopods, living in both epigean and hypogean habitats in North America and Europe. The family includes the following genera: [more]

Atlantasellidae

Atlantasellus is a genus of crustaceans, and the only member of the family Atlantasellidae. It contains the following species: [more]

Austrarcturellidae

[more]

Balloniscidae

[more]

Barybrotidae

[more]

Bathynataliidae

[more]

Bathytropidae

[more]

Berytoniscidae

[more]

Bopyridae

Bopyridae is a family of isopod crustaceans in the suborder Cymothoida. Members of the family are ectoparasites of crabs and shrimps. They live in the gill cavities or on the carapace where they cause a noticeable swelling. Fossil crustaceans have occasionally been observed to have a similar characteristic bulge. [more]

Buddelundiellidae

Trichoniscidae are a family of isopods (woodlice), including the most abundant British woodlouse, Trichoniscus pusillus. [more]

Cabiropidae

Cabiropidae is a family of isopod crustaceans in the suborder Cymothoida. The original description was made by Giard and Bonnier in 1887. Members of the family are hyperparasites of other parasitic isopods in the order and some are parasites on other free living isopods. [more]

Calabozoidae

Calabozoidae is a family of isopod crustaceans, placed in its own order, Calabozoida or Calabozoidea. It comprises two genera, and Pongycarcina. [more]

Chaetiliidae

Chaetiliidae is a family of isopod crustaceans in the suborder Valvifera, comprising the following genera: [more]

Cirolanidae

Cirolanidae is a family of isopod crustaceans, including the following genera: [more]

Corallanidae

[more]

Crinoniscidae

Crinoniscidae is a family of isopod crustaceans in the suborder Cymothoida. The original description was made by Bonnier in 1900. Members of this family are parasites, mostly on other crustaceans. is parasitic on the barnacle, Balanus perforatus. [more]

Cryptoniscidae

Cryptoniscidae is a family of isopod crustaceans in the suborder Cymothoida. The original description was made by Kossmann in 1880. Liriopsidae is a junior synonym. Members of this family are hyperparasites of rhizocephalid barnacles which are themselves parasites of decapod crustaceans. The morphology of the adult females gives little clue as to their true identity but the free living larvae show their true taxonomic affiliations. [more]

Cylisticidae

[more]

Cymothoidae

Cymothoidae is a family of isopods. Several species are parasites, usually of fish. These include the bizarre "tongue-biter", Cymothoa exigua. Around forty genera are recognised  [more]

Cyproniscidae

Cyproniscidae is a family of marine isopod crustaceans in the suborder Cymothoida. The original description was made by Bonnier in 1900. Members of this family are parasitic on other isopods. [more]

Dajidae

Dajidae is a family of marine isopod crustaceans in the suborder Cymothoida. The original description was made by Giard and Bonnier in 1887. Members of this family are ectoparasites of krill. They resemble a fleshy growth on the krill's back, and make the host look as if it is wearing a rucksack. The following genera are included in the famiyl Dajidae: [more]

Delatorreidae

[more]

Dendrotiidae

[more]

Dendrotionidae

[more]

Desmosomatidae

[more]

Detonidae

[more]

Dubioniscidae

[more]

Echinothambematidae

[more]

Entoniscidae

Entoniscidae is a family of marine isopod crustaceans in the suborder Cymothoida. The original description was made by in 1881. [more]

Eubelidae

[more]

Eurycopidae

[more]

Expanathuridae

[more]

Gnathidae

[more]

Gnathiidae

Gnathiidae is a family of isopod crustaceans. They occur in a wide range of depths, from the littoral zone to the deep sea. The adults are associated with sponges and may not feed. The juvenile form is known as a praniza larva, and it is a temporary parasite of marine fish. [more]

Gnathostenetroididae

[more]

Hadromastacidae

[more]

Halophilosciidae

[more]

Haplomunnidae

[more]

Haploniscidae

[more]

Hekelidae

[more]

Hemioniscidae

Hemioniscidae is a family of marine isopod crustaceans in the suborder Cymothoida. The original description was made by Bonnier in 1900. Members of this family are parasitic on cirripede barnacles. [more]

Holidoteidae

[more]

Holognathidae

[more]

Hypsimetopodidae

[more]

Hyssuridae

[more]

Idoteidae

Idoteidae is a family of isopod crustaceans. It includes the following genera: [more]

Ilyarachnidae

[more]

Irmaosidae

[more]

Ischnomesidae

[more]

Janirellidae

[more]

Janiridae

[more]

Joeropsididae

[more]

Katianiridae

[more]

Keuphyliidae

[more]

Leptanthuridae

Leptanthuridae is a family of isopod crustaceans, containing the following genera: [more]

Ligiidae

Ligiidae is a family of woodlice, the only family in the infraorder Diplocheta. Its members are common on rocky shores, in similar habitats to those inhabited by species of the bristletail Petrobius and the crab Cyclograpsus. The family contains the following genera: [more]

Limnoriidae

A gribble (or gribble worm) is any of about 56 species of marine isopod from the family Limnoriidae. They are mostly pale white and small (1?4 millimetres or 0.04?0.16 inch long) crustaceans, although from subantarctic waters can reach 10 mm (0.4 in). [more]

Macrostylidae

[more]

Mesoniscidae

[more]

Mesosignidae

[more]

Microcerberidae

Microcerberidae is a family of isopod crustaceans. They are less than 2 millimetres (0.08 in) long, and live interstitially in shallow marine or freshwater sand habitats. [more]

Microparasellidae

[more]

Mictosomatidae

[more]

Munnidae

[more]

Munnopsidae

[more]

Munnopsididae

[more]

Nannoniscidae

[more]

Nichollsiidae

[more]

Olibrinidae

[more]

Oniscidae

Oniscidae is a family of woodlice, including the common woodlouse Oniscus asellus. Six genera are certainly placed in the family (Oniscus, , Phalloniscus, Rabdoniscus, Rodoniscus and Sardoniscus), with eight others included by some sources (Cerberoides, Diacara, Exalloniscus, Hanoniscus, Hiatoniscus, Hora, Krantzia and Tasmanoniscus). [more]

Paramunnidae

[more]

Paranthuridae

[more]

Philosciidae

Philosciidae are a family of woodlice (terrestrial isopod crustaceans). They occur almost everywhere on earth, with most species found in (sub)tropical America, Africa and Oceania, and only a few in the Holarctic. [more]

Phoratopodidae

Phoratopus remex is a species of isopod crustacean known from only two specimens, and first described in 1925 by (1895?1963). It lives on the continental shelf at Encounter Bay and Fowlers Bay, South Australia. It is so unlike all other isopods that it is placed in its own family, Phoratopodidae and suborder, Phoratopidea. [more]

Phreatoicidae

Phreatoicidae is a family of blind, freshwater isopods. They have survived apparently unchanged for 350 million years, and are only found in South Africa, India, Australia and New Zealand. They were first found near Christchurch in 1882 by Charles Chilton. The family Phreatoicidae now contains 13 genera: [more]

Phreatoicopsidae

[more]

Plakarthriidae

[more]

Platyarthridae

Platyarthridae is a family of woodlice, containing the following genera: [more]

Pleurocopidae

[more]

Ponderellidae

[more]

Porcellionidae

Porcellionidae is a terrestrial family of the order Isopoda. The species classified here cannot roll into a ball, as opposed to the species of family Armadillidiidae, which can. [more]

Protognathiidae

[more]

Protojaniridae

[more]

Pseudarmadillidae

Pseudarmadillo is a genus of woodlice from the Greater Antilles. All extant species live in Cuba, with one species also extending to the Bahamas: [more]

Pseudidotheidae

[more]

Pseudojaniridae

[more]

Pseudomesidae

[more]

Pudeoniscidae

[more]

Rectarcturidae

[more]

Rhyscotidae

[more]

Santiidae

[more]

Schoebliidae

[more]

Scleropactidae

[more]

Scyphacidae

[more]

Serolidae

Serolidae is a family of isopod crustaceans, containing the following genera: [more]

Spelaeoniscidae

[more]

Sphaeromatidae

Sphaeromatidae is a family of isopods, containing the following genera: [more]

Sphaeroniscidae

[more]

Stenasellidae

[more]

Stenetriidae

[more]

Stenoniscidae

[more]

Styloniscidae

Styloniscidae is a family of woodlice, including the following genera: [more]

Tainisopidae

[more]

Tecticipitidae

[more]

Tendosphaeridae

[more]

Thambematidae

[more]

Titaniidae

[more]

Trachelipodidae

[more]

Trichoniscidae

Trichoniscidae are a family of isopods (woodlice), including the most abundant British woodlouse, Trichoniscus pusillus. [more]

Tridentellidae

[more]

Turanoniscidae

[more]

Tylidae

Tylidae is a family of woodlice. It contains approximately 27 species, all but one in the genus , the other being Helleria brevicornis. Together with the family Ligiidae, Tylidae appears to have diverged early from the remaining woodlouse families. [more]

Vermectiadidae

[more]

Xenarcturidae

[more]

Xenosellidae

[more]

More info about the Family Xenosellidae may be found here.

References

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  1. ^ a b c d e f M. Schotte, C. B. Boyko, N. L. Bruce, J. Markham, G. C. B. Poore, S. Taiti & G. D. F. Wilson. "World List of Marine, Freshwater and Terrestrial Isopod Crustaceans". World Register of Marine Species. http://www.marinespecies.org/isopoda/index.php. Retrieved October 7, 2010. 
  2. ^ a b c d e Richard Brusca (August 6, 1997). "Isopoda". Tree of Life Web Project. http://tolweb.org/Isopoda/6320/1997.08.06. 
  3. ^ Frederick R. Schram (1970). "Isopod from the Pennsylvanian of Illinois". Science 169 (3948): 854?855. doi:10.1126/science.169.3948.854. PMID 5432581. 
  4. ^ a b c d S. J. Keable, G. C. B. Poore & G. D. F. Wilson (October 2, 2002). "Australian Isopoda: Families". Australian Museum. http://www.crustacea.net/crustace/isopoda/index.htm. 
  5. ^ R. C. Brusca & M. R. Gilligan (1983). "Tongue replacement in a marine fish (Lutjanus guttatus) by a parasitic isopod (Crustacea: Isopoda)". Copeia 3 (3): 813?816. doi:10.2307/1444352. JSTOR 1444352. 
  6. ^ Ronald L. Shimek (2002). "Pills, parasites, and predators; isopods in the reef aquarium". Reefkeeping 1 (4). http://reefkeeping.com/issues/2002-05/rs/index.php. 
  7. ^ Joel W. Martin & George E. Davis (2001) (PDF). An Updated Classification of the Recent Crustacea. Natural History Museum of Los Angeles County. pp. 132 pp. http://atiniui.nhm.org/pdfs/3839/3839.pdf. 

Sources

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Last Revised: August 24, 2012
2012/08/24 13:11:59