Osedax Temporal range: | |
---|---|
Osedax roseus | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Annelida |
Clade: | Pleistoannelida |
Clade: | Sedentaria |
Order: | Sabellida |
Family: | Siboglinidae |
Genus: | Osedax Rouse et al., 2004 [1] |
Species | |
See text. |
Osedax is a genus of deep-sea siboglinid polychaetes, commonly called boneworms, zombie worms, or bone-eating worms. Osedax is Latin for "bone-eater". The name alludes to how the worms bore into the bones of whale carcasses to reach enclosed lipids, on which they rely for sustenance. They utilize specialized root tissues for bone-boring. It is possible that multiple species of Osedax reside in the same bone. [2] Osedax worms are also known to feed on the collagen itself by making holes in the whale's skeletal structure. These holes can also serve as a form of protection from nearby predators.
Scientists from the Monterey Bay Aquarium Research Institute using the submarine ROV Tiburon first discovered the genus in Monterey Bay, California, in February 2002. The worms were found living on the bones of a decaying gray whale in the Monterey Canyon, at a depth of 2,893 m (9,491 ft).
Osedax are colorful tubeworms that have no mouth, anus, or gut. [3] The body is divided into different regions: trunk, ovisac, and root. They range in length between 2.5 to 7 cm (0.98 to 2.76 in), although this varies between species (cite). [4] Sexual dimorphism is observed in Osedax with females >20,000 times larger than males. [5]
Osedax rely on symbiotic species of bacteria that aid in the digestion of whale proteins and lipids and release nutrients that the worms can absorb. [6] Osedax have colorful feathery plumes that also act as gills and unusual root-like structures that absorb nutrients. The Osedax secrete acid (rather than rely on teeth) to bore into bone to access the nutrients. [7] High concentrations of carbonic anhydrase are found in the roots of Osedax. This serves as evidence of a common bioerosion mechanism in which secreted acid is produced by anaerobic respiration. This process works with a demineralization mechanism in which oxygen is carried from seawater to the roots and HCO−
3 is secreted into the seawater. [8]
The epidermis also plays key roles in bone deterioration and nutrient uptake. This process of bone deterioration occurs through a symbiotic relationship with an endosymbiotic bacteria. [9] The cells in the epidermis of the Osedax root region are responsible for the secretion of digestive enzymes. The epidermis also has an expanded microvillus border which increases the surface area. [9]
Through the use of X-ray CT technology, scans showed that borings made by Osedax mucofloris were hemi-ellipsoidal in shape. Boring depths varied depending on which bone was colonized by the O. mucofloris. Deeper borings were found in radius bone compared to the ulna and vertebrae. [10]
Osedax roots are covered by a mucus sheath that helps protect the worm's trunk. Some studies support the theory that this sheath plays a role in dissolving the bone. This sheath could also play an important role in reducing the damage to Osedax skin by absorbing harmful acid. Another potential function of the mucus sheath is that it could inhibit the breakdown of the worm's bone matrix. This is significant because the bone matrix is integral in maintaining the worm's position while in direct contact with a bone. [8]
Osedax males are notably smaller than their female counterparts. Between 50 and 100 microscopic dwarf males live inside the tube surrounding a single female and never develop past the larval stage and produce sperm. [5] Male dwarfism prevents competition with female Osedax worms for food and space. [5] Conditions that favour dwarfism in male Osedax are:
Interestingly, Osedax priapus lack the frequently observed sexual size dimorphism, and males have similar size to females. This results in competition for space and food. [5] These male worms are able to produce more sperm. However, sexual size dimorphism is still observed in O. priapus where most males are one-third the volume of females.
Female Osedax worms have been observed spawning both in the wild and in laboratory aquaria. [12] Osedax rubiplumus can spawn hundreds of oocytes at a time. They are already fertilized when they are released from the female worm. The worms' endosymbionts, species of bacteria in the order Oceanospirillales, were not observed in the spawned oocytes, which suggests that they are acquired after the worms settle on the bones. [12] In the adult, the bacteria are localised in the root-like structures that grow into the whale bone. [13] [14] This worm appears to be highly fecund and reproduces continuously. This may help explain why Osedax is such a diverse genus, despite the rarity of whale falls in the ocean.
Male Osedax are microscopic dwarfs that live as "harems" inside the lumen of the gelatinous tube that surrounds each female. An individual female can house hundreds of these males in her tube. [15] [16]
Following its discovery in 2002 by researchers at the Monterey Bay Aquarium Research Institute, the genus was announced in Science in 2004. [1]
In late 2005, an experiment by Swedish marine biologists resulted in the discovery of a species of the worm in the North Sea off the west coast of Sweden. In the experiment, a minke whale carcass that had been washed ashore had been sunk to a depth of 120 m (390 ft) and monitored for several months. Biologists were surprised to find that, unlike the previous discoveries, the new species, colloquially known as "bone-eating snot flower" after its scientific name (Osedax mucofloris), lived in relatively shallow waters.
In November 2009, researchers reported finding as many as 15 species of boneworms living in Monterey Bay on the California coast. [17]
Annelid sex is typically determined by genetic factors, [18] however models of environmental sex determination have been proposed for Osedax, in which larvae that settle on bones mature into females, while larvae that settle on female Osedax do not fully develop and mature into males. [19] O. japonicus in particular has showcased an environmental form of sex determination. [20]
Symbionts are the primary providers of nutrition for Osedax. [22] However, these symbionts also possess genes, secretion systems, and toxins that disrupt the Osedax membrane and facilitate recurrent infections of adult Osedax through the root tips. [22] [23] There is ongoing debate in the literature over whether the symbiosis in Osedax roots is commensal or mutualistic. [24] [23] The symbiotic relationship between Osedax and its accompanying bacteria may be transferred either via vertical or horizontal transmission. [23]
Osedax species use collagen, which is the primary organic component in bone. [25] Collagen is degraded using a family of endopeptidases called matrix metalloproteinases (MMPs), which facilitates nutrient absorption by the Osedax. [25] The roots of the Osedax express high amounts of V-ATPase and carbonic anhydrase enzymes, which allows the Osedax to dissolve and absorb collagen and lipids. [25] Once dissolved, the nutrients are either used by the Osedax, or transported to the symbionts for further catabolism. [23] [25]
As the endosymbionts lack secreted M9 peptidase, they rely on the Osedax worm to source extracellular collagen. [25] The symbionts in the Oceanospirillales order have then been observed to further process the collagen using collagenolytic enzymes. [23] [26]
Sequencing of the Osedax worm genome has suggested an evolved dependency on its endosymbionts. [25] This is revealed by genomic streamlining, where increased functional groups were observed despite the loss of some gene families. [25] Six incomplete pathways were discovered in the Osedax worm genome which were supplemented by the endosymbionts. [25] In particular, the Osedax worm lacks specific gene families involved in bone lipid and carbohydrate metabolism. [25] This function is complemented by the Oceanospirillales symbionts, which utilize the glyoxylate cycle to catabolize nutrients from whale bones and convert fatty acids into carbohydrates. [25] The Osedax are then able to take up and store the end products as glycogen. [25] Bacteriocytes are present in the Osedax lower trunk subepidermal connective tissue, [25] and there are additional genes in the bacteriocytes that encode amino acids and glucose and aid in digestion and absorption of proteins into the roots. [27]
The Oceanospirillales symbionts are found in the specialized roots [24] of all Osedax species, [28] [23] and play a major role in accelerating the degradation process of bones, as well as facilitating nutrient uptake for the Osedax. [24] [25] Oceanospirillales are known for their ability to degrade complex organic compounds. [22] [26]
Campylobacterales are abundant along the trunk of the Osedax according to a 2023 study. [24] Different genera in this order are found in Osedax at different points during the whale's degradation:
The Sulfurimonas genus in particular protects the Osedax worms from potentially harmful by-products produced at >140 months of the whale fall degradation. [24] The Sulfurimonas bacteria house the type II and IV sulfide:quinone oxidoreductase genes that encode enzymes to oxidize and assimilate sulfide. [24] These reactions prevent the host from absorbing toxic by-products across the epithelial barrier.
The role of Osedax in the degradation of marine vertebrate remains controversial. Some scientists [29] think that Osedax is a specialist on whalebones while others think that it is more of a generalist. [30] [31] This controversy is due to a biogeographic paradox: despite the rarity and ephemeral nature of whale falls, Osedax has a broad biogeographic range and is surprisingly diverse.
One hypothesis advanced to explain this seeming paradox is that Osedax are able to colonize a variety of vertebrate remains besides whalebones. One study documented 14 new Osedax species successfully colonizing the bones of teleost fish, sea turtles, seals, cows, and turkeys, in addition to whales, [32] while a later study documented a new species feeding on the bones of alligators. [33] Osedax have also been observed colonizing terrestrial mammal bones mixed in with galley waste from a surface vessel. Other scientists[ who? ] have countered this hypothesis by pointing out how the cow bone experiment does not match any natural habitat and also the low probability of terrestrial mammal bones arriving at the ocean floor in significant quantities. They also point out other cases of food falls in which the remains disappeared too swiftly for Osedax colonization and the lack of any observed colonization in similar cases.[ citation needed ]
The true role of Osedax in the degradation of marine vertebrate remains is important to marine vertebrate taphonomy. Burrows closely similar to those made by Osedax species have been found in the bones of ancient marine birds and plesiosaurs, suggesting that the genus may once have had a wider range of foods. [34] [35] [36] [37] In a study of the boring morphological diversity of Osedax, it was shown that the species difference of bone-boring is highly variable; within the same species, the boring morphology is only consistent in a particular bone, but not consistent in different bones. It was also suggested that multiple species of Osedax can co-exist in the same bone and in an incomplete spatial niche differentiation. [2]
The function of Osedax and their borings welcome other species such as Stephonyx amphipods, Paralomis crabs, and Rubyspira gastropods. As Osedax worms break down bone and lipid layers, fauna take advantage and colonize these bone matrices. Overall, the borings made by Osedax have shown to enhance biodiversity and the worms should, therefore, be considered ecosystem engineers. The downside of the deterioration caused by Osedax is that it speeds up the process of erosion, therefore only allowing this new fauna their new habitats for a temporary period. [38]
The oldest trace fossils on bones characteristic of Osedax are from a plesiosaur humerus from the Cambridge Greensand, England, likely reworked from late Albian (c. 100 million years old) sediments and a rib and costal plate from a sea turtle found in Cenomanian (100–93 million years ago) aged sediments of the Chalk Group, England. Osedax likely persisted on the bones of sea turtles after the extinction of most large marine reptiles at the end of the Cretaceous. [39] Osedax have the generalist ability to feed on different vertebrates (fishes, marine birds, whale bones). [40]
In terms of evolutionary history research, the Osedax could have had negative impact in preserving fossil record because its appearance at the shelf-depth combined with its ability to efficiently break down marine vertebrates skeletons. [39]
Selected species: [41] [32] [42] [43]
Siboglinidae is a family of polychaete annelid worms whose members made up the former phyla Pogonophora and Vestimentifera. The family is composed of around 100 species of vermiform creatures which live in thin tubes buried in sediment (Pogonophora) or in tubes attached to hard substratum (Vestimentifera) at ocean depths ranging from 100 to 10,000 m. They can also be found in association with hydrothermal vents, methane seeps, sunken plant material, and whale carcasses.
Any worm that lives in a marine environment is considered a water worm. Marine worms are found in several different phyla, including the Platyhelminthes, Nematoda, Annelida, Chaetognatha, Hemichordata, and Phoronida. For a list of marine animals that have been called "sea worms", see sea worm.
Polychaeta is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. More than 10,000 species are described in this class. Common representatives include the lugworm and the sandworm or clam worm Alitta.
Riftia pachyptila, commonly known as the giant tube worm and less commonly known as the giant beardworm, is a marine invertebrate in the phylum Annelida related to tube worms commonly found in the intertidal and pelagic zones. R. pachyptila lives on the floor of the Pacific Ocean near hydrothermal vents. The vents provide a natural ambient temperature in their environment ranging from 2 to 30 °C, and this organism can tolerate extremely high hydrogen sulfide levels. These worms can reach a length of 3 m, and their tubular bodies have a diameter of 4 cm (1.6 in).
A whale fall occurs when the carcass of a whale has fallen onto the ocean floor, typically at a depth greater than 1,000 m (3,300 ft), putting them in the bathyal or abyssal zones. On the sea floor, these carcasses can create complex localized ecosystems that supply sustenance to deep-sea organisms for decades. In some circumstances, particularly in cases with lower water temperatures, they can be found at much shallower depths, with at least one natural instance recorded at 150 m and multiple experimental instances in the range of 30–382 m (100–1,300 ft). Whale falls were first observed in the late 1970s with the development of deep-sea robotic exploration. Since then, several natural and experimental whale falls have been monitored through the use of observations from submersibles and remotely operated underwater vehicles (ROVs) in order to understand patterns of ecological succession on the deep seafloor.
The Monterey Bay Aquarium Research Institute (MBARI) is a private, non-profit oceanographic research center in Moss Landing, California. MBARI was founded in 1987 by David Packard, and is primarily funded by the David and Lucile Packard Foundation. Christopher Scholin serves as the institute's president and chief executive officer, managing a work force of approximately 220 scientists, engineers, and operations and administrative staff.
Osedax mucofloris is a species of bathypelagic Polychaetes that is reported to sustain itself on the bones of dead whales. Translated from the mixed Greek and Latin used in scientific names, "Osedax mucofloris" literally means "snot-flower bone-eater", though the less-accurate "bone-eating snot-flower worm" seems to be the form actually used. The species is found in North East Atlantic where it is abundant. Osedax mucofloris have special root tissues that they use to pierce into the whale bones found on the seafloor. Although the patterns and mechanisms of this piercing, known as boring, is poorly understood, there is evidence that Osedax mucofloris have acidic mucopolysaccharides in the mucus of their root tissues that aids in the mechanism of boring through bones.
A trophosome is a highly vascularised organ found in some animals that houses symbiotic bacteria that provide food for their host. Trophosomes are contained by the coelom of tube worms and in the body of symbiotic flatworms of the genus Paracatenula.
Osedax roseus is a species of bathypelagic polychaete worm that lives at abyssal depths and is able to sustain itself on the bones of dead whales. The species is found in the North East Pacific.
Osedax rubiplumus is a species of bathypelagic Polychaetes that is reported to sustain itself on the bones of dead whales.
Osedax frankpressi is a species of bathypelagic polychaete worm that lives on the seabed and sustains itself on the bones of dead whales. It can be found in the East North Pacific Ocean. The specific epithet is named in honor of Frank Press "for his distinguished service to science".
Osedax japonicus is a species of bathypelagic polychaete tube worm that lives at great depths on the seabed and is able to sustain itself on the bones of a dead whale. It was first described in 2006 from a sunken sperm whale carcase near Kyushu, Japan.
The annelids, also known as the segmented worms, comprise a large phylum called Annelida. It contains over 22,000 extant species, including ragworms, earthworms, and leeches. The species exist in and have adapted to various ecologies – some in marine environments as distinct as tidal zones and hydrothermal vents, others in fresh water, and yet others in moist terrestrial environments.
Osedax priapus is a species of bathypelagic annelid polychaete worms that consume the nutrients inside the bones of dead whales or other vertebrates.
Microbial symbiosis in marine animals was not discovered until 1981. In the time following, symbiotic relationships between marine invertebrates and chemoautotrophic bacteria have been found in a variety of ecosystems, ranging from shallow coastal waters to deep-sea hydrothermal vents. Symbiosis is a way for marine organisms to find creative ways to survive in a very dynamic environment. They are different in relation to how dependent the organisms are on each other or how they are associated. It is also considered a selective force behind evolution in some scientific aspects. The symbiotic relationships of organisms has the ability to change behavior, morphology and metabolic pathways. With increased recognition and research, new terminology also arises, such as holobiont, which the relationship between a host and its symbionts as one grouping. Many scientists will look at the hologenome, which is the combined genetic information of the host and its symbionts. These terms are more commonly used to describe microbial symbionts.
Xenoturbella profunda, the purple sock or sock worm, is a marine, benthic, deep-water worm-like species that belongs to the genus Xenoturbella. It was discovered in eastern Pacific Ocean by a group of Californian and Australian scientists. The species was described in 2016 from seven specimens.
Kemp Caldera and Kemp Seamount form a submarine volcano south of the South Sandwich Islands, in a region where several seamounts are located. The seamount rises to a depth of 80 metres (260 ft) below sea level; the caldera has a diameter of 8.3 by 6.5 kilometres and reaches a depth of 1,600 metres (5,200 ft). The caldera contains several Hydrothermal vents, including white smokers and diffuse venting areas, which are host to chemolithotrophic ecological communities. The seamount and caldera, which were discovered by seafloor mapping in 2009, are part of the South Georgia and the South Sandwich Islands Marine Protected Area.
Lamellibrachia satsuma is a vestimentiferan tube worm that was discovered near a hydrothermal vent in Kagoshima Bay, Kagoshima at the depth of only 82 m (269 ft) the shallowest depth record for a vestimentiferan. Its symbiotic sulfur oxidizer bacteria have been characterised as ε-Proteobacteria and γ-Proteobacteria. Subspecies have been later found associated with cold seeps at Hatsushima in Sagami Bay and at the Daini Tenryu Knoll in the Nankai Trough with specimens obtained at up to 1,170 m (3,840 ft) depth.
Oligobrachia is a genus in the family Siboglinidae, commonly known as beard worms. These beard worms are typically found at spreading centers, hydrothermal vents, and undersea volcanoes. The siboglinidae are annelids which can be found buried in sediments. Beard worms do not necessarily exist at one specific part of the world's oceans, however, they are spread out all over the ocean floors as long as the surrounding environment is similar; these are known as metapopulations. Most commonly, these organisms are found at the bottom of the ocean floor, whether it be at a depth of roughly 25 meters or hundreds of meters. Oligobrachia can typically be found near hydrothermal vents and methane seeps. An important characteristic of this genus is that it lacks a mouth and gut. Therefore, it relies on symbiotic bacteria to provide the host organism with energy to survive. The majority of oligobrachia that have been observed have been found in the Arctic and other high-latitude areas of the world's oceans.
Frenulata, "beard worms", is a clade of Siboglinidae, "tube worms". They are one of four lineages with numerous species. They may be the most basal clade in the family. Despite being the first tube worms to be encountered and described, they remain the least studied group. This is because of their slender shape, they often get destroyed as a result of being caught as bycatch or poor preservation. They are found primarily in deep, muddy sediments, cold seeps, and anoxic firth sediments.