In invertebrates, the term parapodium (Gr.para, beyond or beside + podia, feet; pl.: parapodia) refers to lateral outgrowths or protrusions from the body. Parapodia are predominantly found in annelids, where they are paired, unjointed lateral outgrowths that bear the chaetae. In several groups of sea snails and sea slugs, 'parapodium' refers to lateral fleshy protrusions.
An image plate showing the different anatomical features (dashed outline) of a representative annelid parapodium. Parapodium is from Lepidonotus oculatus and is a Museums Victoria specimen.Microscope photograph of a parapodium from a specimen of Arctonoe sp. showing the internal acicula that support the two lobes of the parapodium. This parapodium is from a Museums Victoria specimen.
Most species of polychaete annelids have paired, fleshy parapodia which are segmentally arranged along the body axis. Parapodia vary greatly in size and form, reflecting a variety of functions, such as gas exchange, anchorage, protection and locomotion.[1]
General descriptionedit
Parapodia in polychaetes can be uniramous (consisting of one lobe or ramus) but are usually biramous (two lobes or rami). In the latter case, the dorsal lobes are called notopodia and the ventral lobes neuropodia. Both neuropodia and notopodia may possess a bundle of chaetae (neurochaetae and notochaetae respectively), which are highly specific and greatly diversified. A single stout internal chaeta, called an acicula, may be present in each lobe, which are used to support well-developed parapodia. Notopodia and neuropodia can also bear cirri which are tentacle-like projections of the parapodia. In some groups, such as the scale worms (e.g. Polynoidae), the dorsal cirrus is modified into a scale (or elytron). [2]
In most species, the anteriormost segments may be specialised into the head region and prostomium, which can result in the modification of those parapodia, loss of chaetae and elongation of the cirri into anterior-facing tentacular cirri.
Glossary of components of the parapodiumedit
Component
Description
Dorsal cirrus
Cirrus extending from the notopodium; can be modified into a scale (or elytron) in scale worms.
Neuroaciculum
Stout internal supporting chaeta (acicula) for the neuropodium
The fleshy protrusions on the sides of some marine gastropods are also called parapodia. They are particularly well-developed in sea butterflies. Some sea hares use their parapodia to swim. Parapodia can even be used for respiration (similar to gills) or for locomotion.
Parapodia are found in the following taxonomic groups of gastropods:
^Rouse, Greg; Pleijel, Frederick (2001). Polychaetes. Oxford: Oxford University Press. ISBN0198506082.
^Hutchings, P. A.; Fauchald, K. (2000). Polychaetes and Allies: the Southern Synthesis - Class Polychaeata: Definition and General Description. Melbourne: CSIRO Publishing. pp. 1–3.
January 01, 1970
parapodium, genus, plants, plant, invertebrates, term, parapodium, para, beyond, beside, podia, feet, parapodia, refers, lateral, outgrowths, protrusions, from, body, parapodia, predominantly, found, annelids, where, they, paired, unjointed, lateral, outgrowth. For the genus of plants see Parapodium plant In invertebrates the term parapodium Gr para beyond or beside podia feet pl parapodia refers to lateral outgrowths or protrusions from the body Parapodia are predominantly found in annelids where they are paired unjointed lateral outgrowths that bear the chaetae In several groups of sea snails and sea slugs parapodium refers to lateral fleshy protrusions Specimen of the annelid Lepidonotus oculatus with a microscope image of one of its parapodia inset Museums Victoria specimen Contents 1 Annelid parapodia 1 1 General description 1 2 Glossary of components of the parapodium 2 Gastropod parapodia 3 See also 4 ReferencesAnnelid parapodia edit nbsp An image plate showing the different anatomical features dashed outline of a representative annelid parapodium Parapodium is from Lepidonotus oculatus and is a Museums Victoria specimen nbsp Microscope photograph of a parapodium from a specimen of Arctonoe sp showing the internal acicula that support the two lobes of the parapodium This parapodium is from a Museums Victoria specimen Most species of polychaete annelids have paired fleshy parapodia which are segmentally arranged along the body axis Parapodia vary greatly in size and form reflecting a variety of functions such as gas exchange anchorage protection and locomotion 1 General description edit Parapodia in polychaetes can be uniramous consisting of one lobe or ramus but are usually biramous two lobes or rami In the latter case the dorsal lobes are called notopodia and the ventral lobes neuropodia Both neuropodia and notopodia may possess a bundle of chaetae neurochaetae and notochaetae respectively which are highly specific and greatly diversified A single stout internal chaeta called an acicula may be present in each lobe which are used to support well developed parapodia Notopodia and neuropodia can also bear cirri which are tentacle like projections of the parapodia In some groups such as the scale worms e g Polynoidae the dorsal cirrus is modified into a scale or elytron 2 In most species the anteriormost segments may be specialised into the head region and prostomium which can result in the modification of those parapodia loss of chaetae and elongation of the cirri into anterior facing tentacular cirri Glossary of components of the parapodium edit Component Description Dorsal cirrus Cirrus extending from the notopodium can be modified into a scale or elytron in scale worms Neuroaciculum Stout internal supporting chaeta acicula for the neuropodium Neurochaetae Chaetae of the neuropodium Neuropodium Ventral lobe Notoaciculum Stout internal supporting chaeta acicula for the notopodium Notochaetae Chaetae of the notopodium Notopodium Dorsal lobe Ventral cirrus Cirrus extending from the neuropodiumGastropod parapodia edit nbsp Dorsal view of a freshly collected intact sea slug Plakobranchus ocellatus showing its head rhinophores and parapodia The fleshy protrusions on the sides of some marine gastropods are also called parapodia They are particularly well developed in sea butterflies Some sea hares use their parapodia to swim Parapodia can even be used for respiration similar to gills or for locomotion Parapodia are found in the following taxonomic groups of gastropods Clade Cephalaspidea Clade Thecosomata Clade Gymnosomata Clade AplysiomorphaSee also editEpitoke parapodium AnnelidaReferences edit Rouse Greg Pleijel Frederick 2001 Polychaetes Oxford Oxford University Press ISBN 0198506082 Hutchings P A Fauchald K 2000 Polychaetes and Allies the Southern Synthesis Class Polychaeata Definition and General Description Melbourne CSIRO Publishing pp 1 3 Retrieved from https en wikipedia org w index php title Parapodium amp oldid 1184417350, wikipedia, wiki, book, books, library,
