Archive | August 22, 2012

The holotype that walked away

A male of the Galapagos land iguana (Conolophus subcristatus) from North Seymour [Canon 7D, Canon 100-400mm]

In the final post on the amazing fauna of the Galapagos Islands, I thought I would present another animal that somehow failed to impressed Charles Darwin when he visited the archipelago in 1835. Upon seeing the majestic, peaceful land iguanas (Conolophus), he remarked that they were “ugly animals, of a yellowish orange beneath, and of a brownish-red colour above: from their low facial angle they have a singularly stupid appearance.” He then proceeded to molest them by pulling them out of their burrows by their tails, and complain that “we could not for some time find a spot free from their burrows on which to pitch our single tent.”

But I find land iguanas absolutely beautiful, and their facial expression is to me one of serenity and ageless wisdom. They are, however, rather cantankerous creatures, and despite their peaceful appearances males often engage in fierce territorial fights. Land iguanas are exclusively herbivorous, feeding primarily on prickly pear (Opuntia spp.), apparently completely unperturbed by the sharp spines these plants are covered with.

Females of the Galapagos land iguana are smaller and have a lower dorsal crest [Canon 7D, Canon 14mm]

Originally only one species of land iguanas, Conolophus subcristatus, was recognized in the Galapagos. But since 1831, when the animal was formally described, two additional species have been recognized. Barrington iguana (C. pallidus) is known only from the tiny Santa Fé island, and differs from the original species in paler coloration and a lower dorsal crest. In 2009 another species, the pink iguana (C. marthae) was described from the northern part of Isabela. Its distribution is limited to Volcano Wolf, and the lizard is strikingly pink, with black stripes on its body.

Because the population of pink iguanas is incredibly small and very limited in its distribution, its discoverers, Gabriell Gentile and Howard Snell, decided not to collect any specimens of what they considered an already critically endangered species. Rather than depositing the holotype specimen in a museum, which is the standard and required procedure for a formal description of a new species, they decided to tag one of the animals, which they designated the holotype of the new species, with a small electronic chip that would allow to locate the animal later, and let him go after taking the animal’s photos and drawing a blood sample for sequencing its DNA.

Land iguanas, like most Galapagos wildlife, are completely unperturbed by people, and one needs to be careful not to trip over one while walking on a path! [Canon 7D, Canon 14mm]

This was three years ago, and the holotype has not been seen since. Attempts to locate it have failed so far, and another scientist, Michael Frick, has pointed out that the radio transponder used to tag the animal was of a passive type, and it can only be detected from a distance of about 20 cm. In other words, first you need to catch the animal, and only than you can detect its presence by scanning the radio tag!

It is possible that the holotype animal will never be seen again, and in order to comply with the requirements of the International Code of Zoological Nomenclature another specimen may need to be designated as the name-bearing (onomatophore) neotype. Hopefully this time the specimen, or at least a good sample of its tissue, will actually be preserved.