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2 Posts tagged with the darwin tag
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Darwin's Corals

Posted by John Jackson Jun 27, 2011

Brian Rosen (Zoology) and Jill Darrell (Palaeontology) have just published a paper on Darwin’s coral specimen collections and specimen lists. Darwin examined coral reefs in detail during the voyage of HMS Beagle, describing the different types of reef and using this information to write one of his early scientific works The Structure and Distribution of Coral Reefs

 

They were invited to present a talk on this subject at a conference on Darwin’s work at the Universita G. d’Annunzio, Chieti-Pescara, in November 2009. The paper deals with the only known Darwin geological collection in the Museum that comprises 29 coral reef specimens (held in Zoology), almost all from Cocos (Keeling) atoll in the Indian Ocean and accompanied by a little known and hitherto enigmatic Coral Reef Specimen List (holograph held in the NHM Library). Darwin mentions his visit to Keeling and interest in corals in a letter to his sister, sent from Mauritius.

 

NaturalHistoryMuseum_001323_IA.jpg

 

Darwin distinguished three primary types of reef: atolls, barrier reefs and fringing reefs, and used his own observations and those from FitzRoy's surveys to explain what he thought were the reasons for the existence of atolls - including Keeling, which he examined in detail.  Darwin noticed that reef-building corals did not grow below a certain depth of water, but that atolls isolated from other rocky islands were reasonably common.  He rejected the idea that gradual sediment buildup had provided foundations, and said that the idea of so many isolated sea-mounts of the right depth in the middle ocean for coral growth could be rejected.  He argued that rocky islands had sunk gradually below the surface, leaving their original coral reefs to keep the same level as the surface of the sea.  Darwin thought that earthquakes might be connected with the sinking islands - he did not know then what we know about plate tectonics, but had developed a keen interest in geological uplift and subsidence in South America on an earlier part of the voyage.

 

Brian and Jill offer for the first time a plausible explanation of the true origin and purpose of this list and set of specimens.  The specimens are unusual, if not unique, in being a small exhibit prepared by Darwin himself, at or before the time he donated them. The most likely occasion for which Darwin prepared his exhibit was that of his first presentation of his famous subsidence theory of coral reefs to the Geological Society of London on May 31st 1837.

 

Rosen B. R & Darrell, J. 2011. A generalized historical trajectory for Charles Darwin’s specimen collections, with a case study of his coral reef specimen list in the Natural History Museum, London. In:  Stoppa, Francesco & Veraldi, Roberto, Eds., Darwin tra scienza, storia e società. 150° anniversario della publicazione di Origine delle Specie [= Darwin in science, history and society. 150th anniversary of the Origin of Species.]  Edizioni Universitairie Romane, Roma, pp.133-198.

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Charles Darwin, during his voyage on HMS Beagle, collected a single juvenile tortoise from James (San  Salvador or Santiago) Island in the Galápagos Archipelago.

 

This animal was returned to England with three other small tortoises and examined by J.E. Gray, who became Keeper of Zoology at the British Museum (the natural history departments at the BM eventually became what is now the Natural History Museum).

 

The subsequent fate of Darwin’s pet tortoise has been the source of much speculation. Some have claimed that it was transported to Australia (where it lived to an age of more than 175 years); others that it remained in England but disappeared without trace.

 

However, a new paper by Colin McCarthy (Zoology) and Aaron Bauer describes how Darwin’s pet was in fact registered in the British  Museum collection in 1837 and that the specimen still exists:albeit with its registration details hidden on the inner face of the lower shell (plastron).

 

The obscurity of the labelling probably caused these data to be overlooked for more than 170 years. The chelonian (tortoises and turtle) catalogues of Gray, Günther and Boulenger, published between 1844 and 1889, all failed to recognise this specimen as Darwin’s tortoise, mentioning it only as a stuffed juvenile of unknown provenance.

 

Despite this, Günther placed the specimen in his newly defined species Testudo ephippium, which was subsequently regarded as endemic to Abingdon (Pinta) Island in the Galapagos. The confirmation of the specimen’s James Island origin means, however, that Darwin’s pet tortoise is, most appropriately,  a member of the species Chelonoidis darwini.

Bauer, A.M. & McCarthy, C.J. 2010. Darwin’s pet Galápagos tortoise, Chelonoidis darwini, rediscovered.  Chelonian Conservation and Biology 9: 270-276.