Siboglinidae
Encyclopedia
Siboglinidae, also known as the beard worms, is a family
of polychaete
annelid worms whose members made up the former phyla
Pogonophora (the giant tube worms) and Vestimentifera. They are composed of about 100 species of vermiform creatures and live in thin tubes buried in sediments at ocean depths from 100 to 10,000 m. They can also be found in association with hydrothermal vents, methane seep
s, with sunken plant material or whale carcasses
.
The first specimen was dredged from the waters of what is now Indonesia
in 1900. These specimens were given to French zoologist Maurice Caullery
, who studied them for nearly 50 years.
and fixed to the bottom. The tubes are often clustered together in large colonies.
The body is divided into four regions. The anterior end is called the cephalic lobe, which bears from 1 to over 200 thin branchial ciliated tentacle
s, each bearing tiny side branches known as pinnules. Behind this is a glandular forepart, which helps to secrete the tube. The main part of the body is the trunk, which is greatly elongated and bears various annuli, papillae, and ciliary tracts. Posterior to the trunk is the short metamerically
segmented opisthosoma
, bearing external paired chaeta
e, which apparently help to anchor the animal to the base of its tube.
The body cavity has a separate compartment in each of the first three regions of the body, and extends into the tentacles. The opisthoma has a coelom
ic chamber in each of its 5 to 23 segments, separated by septa
. The worms have a complex closed circulatory system and a well-developed nervous system
, but as adults, siboglinids completely lack a mouth, gut and anus.
Siboglinids are dioecious
, with one gonad
on each side of the trunk, within the body cavity. The fertilised eggs develop within the tubes, and hatch to produce small ciliated worm-like larvae.
systems. The vestimentiferans possess an anterior first body part called the obturaculum. Their main trunk of the body bears winglike extensions, the vestimentum, from which their name is derived. Also, unlike other siboglinids that never have a digestive tract, they have one that they completely lose during metamorphosis
. Their primary nutrition is derived from the sulphide-rich fluids emanating from the hydrothermal vents they live by. The sulphides are metabolized by symbiotic hydrogen sulfide- or methane-oxidizing bacteria
living in an internal organ, the trophosome. One gram of trophosome tissue can contain one billion bacteria. It is not completely understood how the worms instigate their relationship with the bacteria. One theory is that the very young worm has a vent on its body permitting the entry of the bacteria from the water. A more recent study of three species of tubeworms including Riftia pachyptila demonstrated that the bacteria actually infect juvenile worms through their skin. Their body is divided into four regions; the obturaculum, vestimentum, trunk, and opisthosome.
Discovery of the hydrothermal vents in the eastern Pacific Ocean was quickly followed by the discovery and description of new vestimentiferan tubeworm species. These tubeworms are one of the most dominant organisms associated with the hydrothermal vents in the Pacific Ocean. Tubeworms anchor themselves to the substratum of the hydrothermal vents by roots located at the basal portion of their bodies . Intact tubeworm roots have proven very difficult to obtain for study because they are extremely delicate, and often break off when a tubeworm is removed from hypothermal vent regions. It is unsure how long the roots of the tube worms can grow to, but root have been recovered longer than 30 m in length. A single aggregation of tubeworms can contain thousands of individuals, and the roots produced by each tubeworm can become tangled with the roots of neighbouring tubeworms . These mats of roots are known as “ropes”, and travel down the tubes of dead tubeworms, and run through holes in rocks. The diameter and wall thickness of the tubeworm roots do not appear to change with distance from the trunk portion of the tubeworms body. Like the trunk portion of the body, the roots of the Vestimentiferans tubeworms are composed of chitin crystallites, which support and protect the tubeworm from predation and environmental stresses. The Vestimenifera tubeworms build the external chitin structure themselves by secreting chitin from specialized glands located in their body walls.
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...
of polychaete
Polychaete
The Polychaeta or polychaetes are a class of annelid worms, generally marine. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. Indeed, polychaetes are sometimes referred to as bristle worms. More than 10,000...
annelid worms whose members made up the former phyla
Phylum
In biology, a phylum The term was coined by Georges Cuvier from Greek φῦλον phylon, "race, stock," related to φυλή phyle, "tribe, clan." is a taxonomic rank below kingdom and above class. "Phylum" is equivalent to the botanical term division....
Pogonophora (the giant tube worms) and Vestimentifera. They are composed of about 100 species of vermiform creatures and live in thin tubes buried in sediments at ocean depths from 100 to 10,000 m. They can also be found in association with hydrothermal vents, methane seep
Cold seep
A cold seep is an area of the ocean floor where hydrogen sulfide, methane and other hydrocarbon-rich fluid seepage occurs, often in the form of a brine pool...
s, with sunken plant material or whale carcasses
Whale fall
Whale fall is the term used for a whale carcass that has fallen to the ocean floor. Whale falls were first observed in the 1980s, with the advent of deep-sea robotic exploration....
.
The first specimen was dredged from the waters of what is now Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
in 1900. These specimens were given to French zoologist Maurice Caullery
Maurice Caullery
Maurice Jules Gaston Corneille Caullery , Paris) was a French biologist.Caullery specialised in parasitic protozoans and marine invertebrates. He also worked on insects.-Awards:...
, who studied them for nearly 50 years.
Anatomy
Most siboglinids are less than 1 millimetre (0.0393700787401575 in) in diameter but 10–75 cm (3.9–29.5 in) in length. They inhabit tubular structures composed of chitinChitin
Chitin n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world...
and fixed to the bottom. The tubes are often clustered together in large colonies.
The body is divided into four regions. The anterior end is called the cephalic lobe, which bears from 1 to over 200 thin branchial ciliated tentacle
Tentacle
A tentacle or bothrium is one of usually two or more elongated flexible organs present in animals, especially invertebrates. The term may also refer to the hairs of the leaves of some insectivorous plants. Usually, tentacles are used for feeding, feeling and grasping. Anatomically, they work like...
s, each bearing tiny side branches known as pinnules. Behind this is a glandular forepart, which helps to secrete the tube. The main part of the body is the trunk, which is greatly elongated and bears various annuli, papillae, and ciliary tracts. Posterior to the trunk is the short metamerically
Metamerism
Metamerism has at least three meanings:*Metamerism is the property of having repeated segments, as in annelids; a concern of zoology and developmental biology...
segmented opisthosoma
Opisthosoma
The opisthosoma is the posterior part of the body in some arthropods, behind the prosoma . It is a distinctive feature of the subphylum Chelicerata...
, bearing external paired chaeta
Chaeta
A chaeta or cheta is a chitinous bristle or seta found on an insect, arthropod or annelid worms such as the earthworm, although the term is also frequently used to describe similar structures in other invertebrates. The plural form is chaetae or chetae.In the Polychaeta, they are located on the...
e, which apparently help to anchor the animal to the base of its tube.
The body cavity has a separate compartment in each of the first three regions of the body, and extends into the tentacles. The opisthoma has a coelom
Coelom
The coelom is a fluid-filled cavity formed within the mesoderm. Coeloms developed in triploblasts but were subsequently lost in several lineages. Loss of coelom is correlated with reduction in body size...
ic chamber in each of its 5 to 23 segments, separated by septa
Septum
In anatomy, a septum is a wall, dividing a cavity or structure into smaller ones.-In human anatomy:...
. The worms have a complex closed circulatory system and a well-developed nervous system
Nervous system
The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...
, but as adults, siboglinids completely lack a mouth, gut and anus.
Siboglinids are dioecious
Dioecious
Dioecy is the property of a group of biological organisms that have males and females, but not members that have organs of both sexes at the same time. I.e., those whose individual members can usually produce only one type of gamete; each individual organism is thus distinctly female or male...
, with one gonad
Gonad
The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells. For example, spermatozoon and egg cells are gametes...
on each side of the trunk, within the body cavity. The fertilised eggs develop within the tubes, and hatch to produce small ciliated worm-like larvae.
Vestimentiferans
Like other tube worms, vestimentiferans are marine and benthic. Riftia pachyptila, a vestimentiferan, is known only from the hydrothermal ventHydrothermal vent
A hydrothermal vent is a fissure in a planet's surface from which geothermally heated water issues. Hydrothermal vents are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots. Hydrothermal vents exist because the earth is both...
systems. The vestimentiferans possess an anterior first body part called the obturaculum. Their main trunk of the body bears winglike extensions, the vestimentum, from which their name is derived. Also, unlike other siboglinids that never have a digestive tract, they have one that they completely lose during metamorphosis
Metamorphosis
Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...
. Their primary nutrition is derived from the sulphide-rich fluids emanating from the hydrothermal vents they live by. The sulphides are metabolized by symbiotic hydrogen sulfide- or methane-oxidizing bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
living in an internal organ, the trophosome. One gram of trophosome tissue can contain one billion bacteria. It is not completely understood how the worms instigate their relationship with the bacteria. One theory is that the very young worm has a vent on its body permitting the entry of the bacteria from the water. A more recent study of three species of tubeworms including Riftia pachyptila demonstrated that the bacteria actually infect juvenile worms through their skin. Their body is divided into four regions; the obturaculum, vestimentum, trunk, and opisthosome.
Discovery of the hydrothermal vents in the eastern Pacific Ocean was quickly followed by the discovery and description of new vestimentiferan tubeworm species. These tubeworms are one of the most dominant organisms associated with the hydrothermal vents in the Pacific Ocean. Tubeworms anchor themselves to the substratum of the hydrothermal vents by roots located at the basal portion of their bodies . Intact tubeworm roots have proven very difficult to obtain for study because they are extremely delicate, and often break off when a tubeworm is removed from hypothermal vent regions. It is unsure how long the roots of the tube worms can grow to, but root have been recovered longer than 30 m in length. A single aggregation of tubeworms can contain thousands of individuals, and the roots produced by each tubeworm can become tangled with the roots of neighbouring tubeworms . These mats of roots are known as “ropes”, and travel down the tubes of dead tubeworms, and run through holes in rocks. The diameter and wall thickness of the tubeworm roots do not appear to change with distance from the trunk portion of the tubeworms body. Like the trunk portion of the body, the roots of the Vestimentiferans tubeworms are composed of chitin crystallites, which support and protect the tubeworm from predation and environmental stresses. The Vestimenifera tubeworms build the external chitin structure themselves by secreting chitin from specialized glands located in their body walls.