Possible Annelid Worm tubes from the Early Devonian of Brazil.

Worm tubes first appear in the fossil record in the Ediacaran and become increasingly common through the Palaeozoic. Most Worm tubes today are made by Polychaete Annelids, a group which have existed since at least the Cambrian, however in the Palaeozoic a variety of other groups, such as Tentaculitoids (thought to have been related to Molluscs and Lophophorates) and Hyolithelminths (possibly Cnidarians) are known to have made tubular structures, making it difficult to assess when tube-building Polychaetes first appeared.

In a paper published in the journal Acta Palaeontologica Electronica on 21 December 2015, Olev Vinn of the Department of Geology at the University of Tartu, Carolina Zabini and Gustavo Sene-Silva of the Universidade Tecnológica Federal do Paraná, Kalle Kirsimäe also of the Department of Geology at the University of Tartu and Lara Susan-Marcos, also of the Universidade Tecnológica Federal do Paraná, describe a series of tubes from the Early Devonian Ponta Grossa Formation of Paraná State in Brazil.

The tubes are fragmentary and have been reworked prior to preservation in sediment, The sample examined contains about 50 such tubes with a maximum length of 2.5 cm. They are 2.9–5.8 mm in width and eliptical, though this is thought to be due to compression. They are banded, with seven-to-ten rings every 5 mm, and do not taper or branch. Vinn et al. describe these as Annulitubus mutveii, where 'Annulitubus' means 'ringed-tube' and 'mutveii' honours palaeontologist Harry Mutvei for his work on the skeletal structures of extinct invertebrates.

Sample (MN 9571-I) from Rio Caniú outcrop, Ponta Grossa Formation, Upper Emsian, Lower Devonian. (A) Fragment showing numerous tubes; holotype of Annulitubus mutveii  (MN 9571-Ia) and paratypes (MN 9571-Ib–e). Note that all tube fragments are straight and have similar orientation, some show smooth surfaces, with very subtle striae, in others it is possible to see shallow rings. (B) Enlarged holotype (MN 9571-Ia), note the smooth rings. (C) Fragment showing paratype (MN 9571-Ig). Vinn et al. (2015).

The Worms are interpreted as having grown close to the site of deposition, probably in dense clusters but not attached to one-another. The locality is not thought to have had any solid rock close by, but shells were available and could possibly have served as points of attachment, or the worms could have lived and formed tubes partially or wholey within the sediment. The tubes are preserved in silica, a mineral not known to have been used to make tubes by any Worm group, and therefore Vinn et al. interpret this as a secondary material which has replaced the original tube material. Silica requires very alkaline conditions to form, conditions under which calcite tubes would be expected to lose much of their original structure, leading Vinn et al. to suggest that the tubes were originally formed from organic material rather than mineral. Such a structure, with non-tapering, non-branching organic tubes with a banded structure is typical of several Polychaete groups, but not associated with any non-Polychaete group, leading Vinn et al. to conclude the tube-builder was almost certainly a Polychaete.

See also...

Neosabellides lizae: A new species of Ampharetid Worm from Lizard Island on Australia's Great Barrier Reef.               Ampharetid Worms are small, usually marine, Annelid Worms related to the tube-building Trumpet Worms...

Cretaceous Bone-eating Worms from England.                                                 Siboglinid Worms are a distinctive group of Annelids which lack mouths and digestive tracts in their...

A new species of Serpulid Worm from the Caribbean.                                                 Serpulids are distinctive Polychaete Worms found throughout the world’s oceans, from the intertidal zones to the deep seas. They live in calcareous tubes, which they cement to hard substrates, and are...

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The death of a hydrothermal vent community.

The East Pacific Rise runs from the Southern Ocean to the Gulf of California, where it passes into the subduction zone beneath the North American Plate, becoming the San Andreas Fault. A number of deepsea hydrothermal vent communities have been discovered along the East Pacific Rise, some of which have been studied extensively. One of these was the site known as Bio9, located at 9°50' North, which was discovered in 1991, and studied extensively over the next few years. The site thrived until 1995, but appeared to sicken and die over the next two years.

In a paper published in the journal Geochemical Transactions on 27 January 2012, Michael Hentscher and Wolfgang Bach of the Department of Geosciences at the University of Bremen discuss the history of the Bio9 hydrothermal vent community over the period 1991-1997, and theorize about how changes to the chemistry of the water emerging from the vent may have brought about the demise of the vent community.

Diagram showing the chemical cycle of a healthy hydrothermal vent community. From Hentscher & Bach (2012).

The Bio9 community was dominated by tubeworms of the genus Riftia when it was first discovered. These worms obtain nutrition from symbiotic bacteria that live within their bodies, bacteria that oxidize hydrogen sulphide from the mineral rich waters. These worms were thriving in 1991, but in 1994 the colonies appeared to have developed rusty red spots. In 1995 the colonies were largely covered by the rusty spots, and by 1997 the colonies had largely died off.

Healthy Riftia tubeworms. NOAA.

Hentscher & Bach theorize that the rusty material was colonies of red, iron-oxidizing bacteria, and that their growth reflected an increase in the amount of iron ions in the water emerging from the vents; they do not believe the bacteria directly harmed the tubeworms.

The death of the tubeworms between 1995 and 1997 would therefore not be directly related to the spread of the red rust in 1994-5. Hentscher & Bach suspect that this was due to a fall in the level of hydrogen sulphide within the vent water, resulting in the death of first the symbiotic bacteria within the worms, and then the worms themselves.

The chemicals emitted by terrestrial volcanic springs and fumaroles change over time, and there is no reason to suspect that deep-sea hydrothermal vents would behave any differently. If this is the case then the death of this vent community would be a part of the natural life-cycle of the tubeworms, and hydrothermal vent communities in other parts of the world, with different biological communities, probably suffer similar die-offs.

See also A deep-sea hydrothermal vent community discovered in the Mariana Trench, Deepest hydrothermal vent communities yet found discovered in the Caribbean and New deep-sea hydrothermal vent ecosystem discovered in the Southern Ocean.