Osedax worms are marine annelids closely related to the deep sea vent/seep-associated vestimentiferan worms. The sessile (i.e., fixed in one place) females bore into the bones of whale carcasses--and possibly bones of other vertebrates (Rouse et al. 2004; Glover et al. 2005; Vrijenhoek et al. 2008).
Osedax mucofloris, only the third Osedax species described and the first Osedax known from the Atlantic Ocean, was described by Glover et. al (2005) from an experimentally deposited carcass of a Minke Whale (Balaenoptera acutorostrata) at a depth of 125 meters in the North Sea. This species has also been collected in the North Sea from submerged Pilot Whale (Globicephala melas) bones at a depth of 30 meters and Minke Whale (Balaenoptera acutorostrata) bones at a depth of 125 meters (Dahlgren et al. 2006). Osedax worms were previously known only from deep-sea (1500 to 3000 meter) whale-falls in the northeast Pacific. Glover et al. discuss the implications of such a global distribution of the genus Osedax for understanding the phylogeography, historical biogeography, and diversification of this group. (Glover et al. 2005)
Osedax mucofloris extends out of the whale bone into the seawater. The major features of this portion are:
- Feathered plumes, which are the gills, or branchiae, that bring oxygen down to the root structure embedded in the whale bone.
- A cylinder-shaped column that extends furthest into the water column. Scientists think this structure, an oviduct, shoots fertilised eggs into the water column, perhaps helping the animal to disperse tiny larvae to be carried off by ocean currents.
Live specimens are visible as four white to pink palps that emerge from the surface of the whale bone. The palps are 5-6 mm in length, and are surrounded at their base by a thin mucous tube. The oviduct is white, and extends to one-third of the length of the uncontracted palps. The palps are of equal length, measuring 0.8 mm when contracted, with numerous pinnules 0.1 mm in length. At the base of the pinnules there is a ciliary band that runs the entire length of each palp. The pinnules are 0.01 mm wide. They are densely packed and coloured white to pink in live specimens, with microvilli 0.05 mm in length. The trunk region is 6-8 mm in length and 0.5 mm wide, and is partially embedded within the bone matrix. The trunk is principally composed of bands of longitudinal muscles, galnds and major dorsal and ventral blood vessels. The mouth and gut are absent. There are ventral plaques on the collar (peristomial region) of the trunk.
On dissected specimens, an oviduct is visble running into an ovisac and the root structure, and contains numerous eggs in the trunk region. There is a vascularized root system of 2-10 mm in length, which burrows in a shallow depression to depths of 2-3 mm into the whale bone matrix in a bracnhed, mycelial form. Numerous eggs (greater than 100 in number) were relaesed from the ovisac on disturbance. The eggs ranged in diameter from 85-90 um. The chaetae and opisthosomal region were not observed. Epibiotic rod-shaped bacteria (length 1-1.5 um, width 300 nm) were present over the surface of the trunks, palps and pinnules, but absent from the roots.
(Glover et al. 2005)
- UNESCO-IOC Register of Marine Organisms http://www.marinespecies.org/aphia.php?p=sourcedetails&id=1318
To date, Osedax mucofloris has only been recorded from 2 whale carcasses in the Swedish fjord Kosterfjord (58° 53.1 N, 11° 06.4 E). It may be widespread in the Atlantic, however. The problem is finding whale remains on the sea floor - even if there are a lot of them, they are small relative to the vast expanses of the ocean.
O. mucofloris has so far only been found living on the bones of marine mammals, specifically the remains of:
O. mucofloris has only recently been discovered and it is not yet known if it is under threat. One possibility is that intensive whaling over the last 300 years has reduced the available habitat for this polychaete worm, a previously unknown consequence of the whaling industry.
Found on the bones of an experimentally implanted Minke whale carcass at 125 m depth, Kosterfjord, Sweden (58°53.1`N, 11°06.4` E) (Glover et al., 2005).
Many Osedax species have numerous pinnules on their palps that give the crown a feathery appearance. Of the known Osedax species, only O. mucofloris and O. frankpressi have pinnules oriented all inward (the pinnules in the other species being turned outward, both inward and outward, or absent). Most known Osedax species have red palps (the palps of O. frankpressi are red with two white lateral stripes in living worms), but the palps of Osedax mucofloris are white to pink. (Rouse et al. 2004; Vrijenhoek et al. 2009)
Depth range (m): 125 - 125
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.
Life History and Behavior
Glover et al. (2005) reported that disturbance caused the worms to retract completely into the bone. However, when placed in aquaria, with clean, chilled seawater, they would emerge from the bone and be clearly visible to the naked eye. Over a period of several minutes, the worms would first extend the palps, and then the oviduct (see video here). Any disturbance to the aquarium tank would result in the animals immediately withdrawing into the bone.
Osedax mucifloris appeared to be able to reproduce and grow to maturity within one month on defaunated bones placed in a aquaria (Glover et al., 2005).
Why has Osedax evolved dwarf males?
We do not yet know the full answer. One theory is that it overcomes the problem of males and females finding each other if they are unable to move (sessile), as Osedax females are. The males are able to move around the females, fertilising their eggs. It is easier to do this if you are small and motile, or dwarfed.
Detailed examination of at least 50 mature specimens indicated an absence of the dwarfed males reported for northeast Pacific Osedax species. However, O. mucofloris appeared able to reproduce and grow to maturity within one month on defaunated bones placed into aquaria. (Glover et al. 2005)
Evolution and Systematics
5 species have been described in the genus Osedax:O. mucofloris, scientists have been comparing the DNA sequences of Osedax species with those of other related annelid worms and invertebrates. The results suggest that O. mucofloris is indeed a type of highly unusual polychaete worm in the family Siboglinidae. This family includes the giant hydrothermal vent tubeworm, Riftia pachyptila.O. mucofloris shares a recent common ancestor with R. pachyptila, raising the interesting possibility that at some point the ancestors of these species were able to switch from hydrothermal vents to whale bones. However, we are a long way from understanding this process fully. The main problem is that we know there are probably hundreds, if not more, species of Siboglinidae that have yet to be discovered. Without these missing branches of the evolutionary tree, it is difficult to understand how exactly O. mucofloris evolved, or when.
Molecular Biology and Genetics
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.
- G. W. Rouse, S. K. Goffredi, and R. C. Vrijenhoek (2004). "Osedax: Bone-Eating Marine Worms with Dwarf Males". Science 305: 668–671. doi:10.1126/science.1098650. PMID 15286372.
- Read, G.; Fauchald, K. (2012). "Osedax mucofloris Glover, Kallstrom, Smith & Dahlgren, 2005". World Register of Marine Species. Retrieved March 20, 2013.
- "'Zombie worms' found off Sweden". BBC News. October 18, 2005. Retrieved 12 February 2010.
- "World-wide whale worms? A new species of Osedax from the shallow north Atlantic". Proc. Biol. Sci. (National Center for Biotechnology Information) 272 (1581): 2587–92. 22 December 2005. doi:10.1098/rspb.2005.3275. PMC 1559975. PMID 16321780.
- "North Sea marine worm discovered". Natural History Museum. 19 October 2005. Retrieved February 13, 2010.
- Glover, A. G; Kallstrom, B.; Smith, C. R; Dahlgren, T. G (2005). "World-wide whale worms? A new species of Osedax from the shallow north Atlantic". Proceedings of the Royal Society B: Biological Sciences 272 (1581): 2587–2592. doi:10.1098/rspb.2005.3275. ISSN 0962-8452.