Posted by: Rob Viens | July 27, 2013

Mr. Wickham’s Lizards

For the next week  the Beagle was sailing south, on route to the mouth of the Rio Negro.  Darwin’s entries are rather sparse, but he does mention catching up with the schooners that have been surveying in the region:

“Our regular fortune followed us in the form of a sharp gale of wind. — It soon lulled but for two or three days a nasty head swell remained, which sadly hindered our progress. — The object of this cruize is to survey some of the outer banks near the R. Negro & Bahia Blanca & likewise to pick up Mr Stokes & his party, who have been so laboriously employed with the little Schooners.” (July 25-29)

Many of the officers on the Beagle had a basic interest in the natural world – in fact, it was common for the time for officers of the Royal Navy to collect scientific data while at sea (see Charles Darwin – Geology Teacher).  But it is clear that Darwin’s enthusiasm was infectious, because when the Beagle met up with Lieutenant Wickham last month, Wickham gave Darwin a bunch of samples that he had collected over the summer months along the coast of Argentina.  A lot of these specimens were lizards and frogs.

Here are a few of the samples Wickham brought back to Darwin (all quotes are Darwin’s short descriptions from his Zoology Notebook):

Graceful tree iguana (Proctotretus gracilis, now Liolaemus gracilis)

“Mud colour with lighter lateral line.”

Graceful Tree Iguana (from the Reptile Database)

graceful tree iguana

Bibron’s iguana (Diplolaemus Bibronii)

“General colour blueish grey with tinge of rust colour on back. broard transverse bands with white undulation behind them.”

Bibron’s iguana (from the Reptile Database)

Bibron's iguana

Darwin’s iguana (Diplolaemus Darwinii)

“General colour not so blue, with pointed, bright yellow undulations in hinder part of brown band”

Sketch of Darwin’s iguana from Zoology of the Voyage of the Beagle by Bell

Darwin's Iguana

Whorltail iguana species (Proctotretus pectinatus, now Stenocercus pectinatus)

“On back transverse rows: each with 3 semilunar rich brown marks, edged with cream colour. Lateral line of same colour; about head traces of bright green.”

(Described earlier in “Beautiful Lizards” of the Pampas)

Wickham also brought back a few amphibians, including:

Four-eyed frog (Pleurodema Darwinii, now Pleurodema bibroni (sorry Darwin))

“Elegantly marked with black & pale green; colours most vivid on the lumbar glands; hinder thighs with little tinge of orange on softer parts.”

This little guy gets his name from the two markings on his back that look like eyes.  This is one of those great evolutionary features that results from the fact that individuals that appear to have eyes facing backward are less likely to get eaten.  They survive, pass on the trait, and eventually the population (survivors) all have “eyes” on their backs. Oh, and it turns out those “eyes” are also poison glands – that helps, too!

Sketch of the Four-eyed frog from Zoology of the Voyage of the Beagle by Bell (left) and modern photo from conservacionpatagonica.org

Four-eyed frog

Giant toad (Bufo agua, now Bufo marinus)

“Head remarkably flat, dark grey, with much blacker & symetrical markings.”

This name seems to include several different species including the Cane Toad.  Here is a species from Florida (from the Florida Wildlife Extension):

"giant

On to the Rio Negro! (RJV)

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