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Friday 28 Feb, 4.30pm, Neil Chalmers Seminar Room

 

Livestreamed on http://www.youtube.com/user/SciFriSeminars

 

 

Chemosynthesis-based communities through time: a 3.2 billion year history

 

Cris Little, University of Leeds

 

At the beginning of this seminar I will briefly review the ecology of modern chemosynthetic communities at hydrothermal vents, hydrocarbon (‘cold’) seeps and sunken dead whales (whale-falls) touching on biogeography and discussing evolutionary issues, including molecular divergence estimates for several major taxonomic groups.

 

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Then I will turn to the fossil record of these communities, which for vents goes back 3.25 billion years. I will show that vent and seep fossil assemblages have changed in taxonomic structure during the Phanerozoic, from brachiopod dominated communities in the Palaeozoic and early Mesozoic to mollusc (bivalve and gastropod) dominated communities from the later Mesozoic onwards. Some of the ecologically dominant taxa that have chemosymbiotic bacteria (e.g. vesicomyid clams and bathymodiolin mussels) are relative newcomers to vent and seep environments and were preceded by other, now extinct, bivalves that may (or may not) also have had symbionts.

 

Whale-fall communities from the Miocene are similar in structure to modern examples in the so-called sulfophilic stage, but older Oligocene and latest Eocene whale-fall communities lack some of the typical molluscs. This may be related to the small size of whales in their early evolutionary history. Prior to the Eocene whale-fall-like communities may have existed on sunken marine reptiles (e.g. turtles, ichthyosaurs and plesiosaurs), or even large fish carcasses.

 

 

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SciFri is a cross-departmental science seminar series and social event run by the NHM Science Forum, held the last Friday of each month. The 45 minute talks are intended to be informal, contemporary, inter-disciplinary and cover a range of fields including the latest research, curation, science policy, publishing, media, fieldwork and science methods. If you have ideas for future speakers from any of these areas please contact the seminar organiser Adrian Glover, Life Sciences Department.

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Helena Wiklund and Adrian Glover, together with collaborators from the USA and Sweden, have described six new species in the polychaete worm genus Ophryotrocha. The six new species were discovered on five whale-falls and two wood-falls in deep-sea water off the Californian coast.

 

Worms in the genus Ophryotrocha were until recently only known from shallow seas rich in nutrients, but as deep sea exploration has progressed, they have been found to be common in organically-enriched habitats such as hydrothermal vents,  cold seeps, whale-falls and in  areas impacted by human pollution (such as underneath fish farms), and  may well play an important ecosystem function role in the biodegradation  and decomposition of organic-rich materials. The new data also  highlight the poorly known biodiversity of the deep sea, and how  deep-sea species evolved.

 

The scientists have examined both the morphology and DNA of the worms.  Identification of one of the species is only possible by looking at differences in their DNA - its physical form is otherwise identical to another species found in the Atlantic. This is of additional interest because some marine species are found in all oceans but others will be found in only one.  The difference in DNA suggests the evolution of different species as a result of geographical separation.  It is suggested that there will be significantly more diversity in this and other groups in deep sea habitats with implications for understanding of these mysterious ecosystems.


Wiklund H, Altamira I, Glover AG, Smith CR, Baco A, Dahlgren TG. (2012) Systematics and biodiversity of Ophryotrocha (Annelida, Dorvilleidae) with descriptions of six new species from deep-sea whale-fall and wood-fall habitats in the north-east Pacific. Systematics and Biodiversity 10(2): 243-259.