Chaetopterus variopedatus
Encyclopedia
Chaetopterus variopedatus is a species
of parchment worm, a marine polychaete in the family
Chaetopteridae. It is found worldwide.
Polychaetes, or marine bristle worms, have elongated bodies divided into many segments. Each segment
may bear setae (bristles) and parapodia
(paddle-like appendages). Some species live freely, either swimming, crawling or burrowing, and these are known as "errant". Others live permanently in tubes, either calcareous or parchment-like, and these are known as "sedentary".
, pale coloured and up to twenty-five centimetres long. The anterior end is short and has bristle-bearing segments and a shovel-like mouth. The middle section bears parapodia
. On the 12th segment these are modified into long wing-like structures which secrete mucus and form a bag. The parapodia on segments 13, 14 and 15 are fused into three paddle-shaped, piston-like structures, the purpose of which is to pump water through the tube. The water is drawn in through the anterior end and expelled through the posterior end, passing through the fine mesh of the mucus bag where food particles get trapped. The mucus bag is later rolled up and passed by a conveyor belt of whipping hairs in the ciliated dorsal groove to the mouth where it is swallowed whole. The posterior half of the worm is segmented and tapers towards the rear, bearing appendage
s on each segment.
, occurring in shallow coastal habitats in both temperate and tropical locations throughout the world. It is plentiful around the coasts of Britain and Ireland but is absent from the east coast of England south of the Tees estuary. The tough permanent tubes are found buried in sand and gravel in the littoral
and sub-littoral
zones. At greater depths they are found adhering to bedrock, in crevices and under boulders.
In New Zealand there have been many recent reports of the parchment-like tubes of Chaetopterus littering beaches, especially after storms. Since about 1995, large areas of shallow sea have been invaded by the worm, believed to be C. variopedatus. By covering the sandy bottom with a dense mat of tubes, the parchment worm makes life very difficult for the native bottom-dwelling fauna
. Other marine worms, clam
s and starfish have been squeezed out, but the big-belly seahorse
(Hippocampus abdominalis) has thrived as it finds extra prey
in the tiny sea slaters and mysid shrimps it finds between the tubes and can anchor itself by its tail to prevent itself being swept away.
e become part of the plankton
, drifting and feeding for some weeks until they settle out.
The development of C. variopedatus follows an unusual pattern in that those segments destined to become part of the mid-body region have accelerated development as compared with the anterior segments. This heterochrony
is not seen in other polychaete worms.
, Polyonyx gibbesi and certain Pisidia
species living almost exclusively within the tubes although they do not share a tube with each other. It is likely that the crabs gain protection from predators
within the tubes and possibly food from the host worm.
Bottom-feeding fish
and crustacean
s probably prey on C. variopedatus but the worm is made less accessible by the fact that it never emerges from its tube which is safely buried beneath the surface of the substrate. If it becomes injured, this worm has the ability to regenerate its entire body from a single segment. Another anti-predator strategy involves emitting a luminescent
cloud of mucus from its tube.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of parchment worm, a marine polychaete in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Chaetopteridae. It is found worldwide.
Polychaetes, or marine bristle worms, have elongated bodies divided into many segments. Each segment
Segmentation (biology)
Segmentation in biology refers to either a type of gastrointestinal motility or the division of some animal and plant body plans into a series of repetitive segments. This article will focus on the segmentation of animal body plans, specifically using the examples of the phyla Arthropoda,...
may bear setae (bristles) and parapodia
Parapodium
Parapodia , singular parapodium, are paired, un-jointed lateral outgrowths from the bodies of two different invertebrate groups, which are primarily marine in habitat...
(paddle-like appendages). Some species live freely, either swimming, crawling or burrowing, and these are known as "errant". Others live permanently in tubes, either calcareous or parchment-like, and these are known as "sedentary".
Description
C. variopedatus builds and lives permanently in a tough, flexible, papery U-shaped tube buried in soft substrate with both ends protruding like little chimneys. The worm itself is segmentedSegmentation (biology)
Segmentation in biology refers to either a type of gastrointestinal motility or the division of some animal and plant body plans into a series of repetitive segments. This article will focus on the segmentation of animal body plans, specifically using the examples of the phyla Arthropoda,...
, pale coloured and up to twenty-five centimetres long. The anterior end is short and has bristle-bearing segments and a shovel-like mouth. The middle section bears parapodia
Parapodium
Parapodia , singular parapodium, are paired, un-jointed lateral outgrowths from the bodies of two different invertebrate groups, which are primarily marine in habitat...
. On the 12th segment these are modified into long wing-like structures which secrete mucus and form a bag. The parapodia on segments 13, 14 and 15 are fused into three paddle-shaped, piston-like structures, the purpose of which is to pump water through the tube. The water is drawn in through the anterior end and expelled through the posterior end, passing through the fine mesh of the mucus bag where food particles get trapped. The mucus bag is later rolled up and passed by a conveyor belt of whipping hairs in the ciliated dorsal groove to the mouth where it is swallowed whole. The posterior half of the worm is segmented and tapers towards the rear, bearing appendage
Appendage
In invertebrate biology, an appendage is an external body part, or natural prolongation, that protrudes from an organism's body . It is a general term that covers any of the homologous body parts that may extend from a body segment...
s on each segment.
Distribution and habitat
C. variopedatus has a cosmopolitan distributionCosmopolitan distribution
In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...
, occurring in shallow coastal habitats in both temperate and tropical locations throughout the world. It is plentiful around the coasts of Britain and Ireland but is absent from the east coast of England south of the Tees estuary. The tough permanent tubes are found buried in sand and gravel in the littoral
Littoral
The littoral zone is that part of a sea, lake or river that is close to the shore. In coastal environments the littoral zone extends from the high water mark, which is rarely inundated, to shoreline areas that are permanently submerged. It always includes this intertidal zone and is often used to...
and sub-littoral
Neritic zone
The neritic zone, also called coastal waters, the coastal ocean or the sublittoral zone, is the part of the ocean extending from the low tide mark to the edge of the continental shelf, with a relatively shallow depth extending to about 200 meters...
zones. At greater depths they are found adhering to bedrock, in crevices and under boulders.
In New Zealand there have been many recent reports of the parchment-like tubes of Chaetopterus littering beaches, especially after storms. Since about 1995, large areas of shallow sea have been invaded by the worm, believed to be C. variopedatus. By covering the sandy bottom with a dense mat of tubes, the parchment worm makes life very difficult for the native bottom-dwelling fauna
Fauna
Fauna or faunæ is all of the animal life of any particular region or time. The corresponding term for plants is flora.Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess shale fauna"...
. Other marine worms, clam
Clam
The word "clam" can be applied to freshwater mussels, and other freshwater bivalves, as well as marine bivalves.In the United States, "clam" can be used in several different ways: one, as a general term covering all bivalve molluscs...
s and starfish have been squeezed out, but the big-belly seahorse
Big-belly seahorse
The big-belly seahorse or pot bellied seahorse, Hippocampus abdominalis, is one of the largest seahorse species in the world with a length of up to 35 cm.-Habitat:The big-belly seahorse is found in large rock pools at low tide, amidst seaweed...
(Hippocampus abdominalis) has thrived as it finds extra prey
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
in the tiny sea slaters and mysid shrimps it finds between the tubes and can anchor itself by its tail to prevent itself being swept away.
Biology
A female C. variopedatus can produce and liberate a batch of 150,000 to 1 million eggs into the sea. After fertilisation, the developing larvaLarva
A larva 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...
e become part of the plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
, drifting and feeding for some weeks until they settle out.
The development of C. variopedatus follows an unusual pattern in that those segments destined to become part of the mid-body region have accelerated development as compared with the anterior segments. This heterochrony
Heterochrony
In biology, heterochrony is defined as a developmental change in the timing of events, leading to changes in size and shape. There are two main components, namely the onset and offset of a particular process, and the rate at which the process operates...
is not seen in other polychaete worms.
Ecology
Several species of crabs have adopted the tubes of C. variopedatus as their home with Pinnixa chaetopteranaPinnixa chaetopterana
Pinnixa chaetopterana, the tube pea crab, is a small decapod crustacean that lives harmlessly within the tube of the polychaete worm, Chaetopterus variopedatus.-Description:...
, Polyonyx gibbesi and certain Pisidia
Pisidia (genus)
Pisidia is a genus of marine porcelain crabs, formerly included in Porcellana, comprising the following species:*Pisidia bluteli *Pisidia brasiliensis Haig, 1968*Pisidia dehaanii...
species living almost exclusively within the tubes although they do not share a tube with each other. It is likely that the crabs gain protection from predators
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
within the tubes and possibly food from the host worm.
Bottom-feeding fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
and crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s probably prey on C. variopedatus but the worm is made less accessible by the fact that it never emerges from its tube which is safely buried beneath the surface of the substrate. If it becomes injured, this worm has the ability to regenerate its entire body from a single segment. Another anti-predator strategy involves emitting a luminescent
Luminescence
Luminescence is emission of light by a substance not resulting from heat; it is thus a form of cold body radiation. It can be caused by chemical reactions, electrical energy, subatomic motions, or stress on a crystal. This distinguishes luminescence from incandescence, which is light emitted by a...
cloud of mucus from its tube.