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| Amblyrhynchus cristatus (Bell, 1825) |
The Marine Iguana (Amblyrhynchus cristatus) is an iguana found only on the Galapagos Islands that has the ability, unique among modern lizards, to live and forage in the sea. Thomas Bell FRS ( 11 October 1792 - 13 March 1880) was an English Zoologist, surgeon and Writer Year 1825 ( MDCCCXXV) was a Common year starting on Saturday (link will display the full calendar of the Gregorian Calendar (or a Common Iguana is a Genus of Lizard native to tropical areas of Central and South America and the Caribbean first described by Austrian Lizards are a large and widespread group of Reptiles of the order Squamata, with nearly 5000 species and ranging across all continents except This article is about the body of water For other uses see SEA and Seas. It has spread to all the islands in the archipelago, and is sometimes called the Galapagos Marine Iguana. An archipelago (ɑrkəˈpɛləgoʊ is a chain or cluster of Islands The word archipelago literally means "chief Sea " from Italian It mainly lives on the rocky Galapagos shore, but can also be spotted in marshes and mangrove beaches.
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Description
On his visit to the islands, Charles Darwin was revolted by the animals' appearance, writing:
- The black Lava rocks on the beach are frequented by large (2-3 ft) most disgusting clumsy Lizards. Charles Robert Darwin (February 12 1809 &ndash April 19 1882 was an English naturalist, who realised and demonstrated that all Species of life They are as black as the porous rocks over which they crawl & seek their prey from the Sea. I call them 'imps of darkness'. They assuredly well become the land they inhabit.
In fact, Amblyrhynchus cristatus is not always black; the young have a lighter coloured dorsal stripe, and some adult specimens are grey. The reason for the sombre tones is that the species must rapidly absorb heat to minimize the period of lethargy after emerging from the water. They feed almost exclusively on marine algae, expelling the excess salt from nasal glands while basking in the sun, and the coating of salt can make their faces appear white. Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms In adult males, coloration varies with the season. Breeding-season adult males on the southern islands are the most colorful and will acquire reddish and teal-green colors, while on Santa Cruz they are brick red and black, and on Fernandina they are brick red and dull greenish.
Another difference between the iguanas is size, which is different depending on the island the individual iguana inhabits. The iguanas living on the islands of Fernandina and Isabela (named for the famous rulers of Spain) are the largest found anywhere in the Galápagos. Fernandina Island (formerly known in English as Narborough Island is the third largest and youngest island of the Galápagos Islands. Isabela Island is the largest island of the Galápagos with an area of 4640 km²and length of 80 miles (100km nearly 4 times larger than Santa Cruz the On the other end of the spectrum, the smallest iguanas are found on the island on Genovesa. Genovesa Island is a Shield volcano in the Galápagos Islands in the eastern Pacific Ocean
Adult males are approximately 1. 3 m long, females 0. The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International 6 m, males weigh up to 1. 5 kg.
Behavior
As a cold blooded animal, the marine iguana can spend only a limited time in the cold sea, where it dives for algae. Cold-blooded organisms (called poikilotherms - "of varying temperature" maintain their body temperatures in ways different from Mammals and Birds However, by swimming only in the shallow waters around the island they are able to survive single dives of up to half an hour at depths of more than 15 m. [2] After these dives, they return to their territory to bask in the sun and warm up again. In Ethology, Sociobiology and Behavioral ecology, the term territory refers to any sociographical area that an Animal of a particular Species When cold, the iguana is unable to move effectively, making them vulnerable to predation, so they become highly aggressive before heating up (since they are unable to run away they try to bite attackers in this state). During the breeding season, males become highly territorial. The males assemble large groups of females to mate with, and guard them against other male iguanas. However, at other times the species is only aggressive when cold.
Marine iguanas have also been found to change their size to adapt to varying food conditions. During El Niño conditions when the algae that the iguanas feed on was decreased for a period of two years, some were found to decrease their length by as much as 20%. El Niño-Southern Oscillation ( ENSO; commonly referred to as simply El Niño) is a global coupled ocean-atmosphere phenomenon When food conditions returned to normal, the iguanas returned to their pre-famine size. It is speculated that the bones of the iguanas actually shorten as a shrinkage of connective tissue could only account for a 10% length change. [3]
Conservation
This species is completely protected under the laws of Ecuador, and is listed under CITES Appendix II. For a topic outline on this subject see List of basic Ecuador topics. CITES (the United Nations Convention on International Trade in Endangered Species of Wild Fauna and Flora) is an international agreement between governments drafted El Niño effects cause periodic declines in population, with high mortality, and the marine iguana is threatened by predation by exotic species. El Niño-Southern Oscillation ( ENSO; commonly referred to as simply El Niño) is a global coupled ocean-atmosphere phenomenon The total population size is unknown, but is, according to IUCN, at least 50,000, and estimates from the Charles Darwin Research Station are in the hundreds of thousands. The Charles Darwin Research Station ( CDRS) is a biological research station operated by the Charles Darwin Foundation.
Threats
The marine iguanas have not evolved to combat newer predators. Therefore, cats and dogs eat both the young iguanas and dogs will kill adults due to the iguanas' slow reflex times and tameness. Dogs are especially common around human towns and can cause tremendous predation. Cats are also common in towns, but also occur in numbers in remote areas, where they take a toll on iguanas.
Evolution
Researchers theorize that land and marine iguanas evolved from a common ancestor since arriving on the islands from South America, presumably by driftwood[4][5]. An ancestor is a Parent or ( recursively) the parent of an ancestor (i South America is a Continent of the Americas, situated entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a It is thought that the ancestral species inhabited a part of the volcanic archipelago that is now submerged. Plate tectonics and hotspots Divergent plate boundaries At the
A second school of thought holds that the Marine iguana may have evolved from a now extinct family of sea-going reptiles.
 A colourful adult male iguana on Fernandina. |
 Marine Iguanas, Galapagos Islands |
 Marine Iguanas, Galapagos Islands |
See also
References
- Rothman, Robert, Marine Iguana Galapagos Pages. The Hybrid Iguana is a first generation hybrid, which is the result of interspecies breeding between a male Marine Iguana and a female Land Iguana on Rochester Institute of Technology. Retrieved 16 August 2006.
Footnotes
- ^ Nelson et al (2004). Amblyrhynchus cristatus. 2006 IUCN Red List of Threatened Species. The IUCN Red List of Threatened Species (also known as the IUCN Red List or Red Data List) created in 1963 is the world's most comprehensive inventory of the global IUCN 2006. Retrieved on 11 May 2006. Database entry includes justification for why this species is vulnerable
- ^ GalapagosPages says typical dives last only a few minutes at depths of less than five metres, but Darwin reported a member of the crew submerging an iguana for an hour, and pulling it out with a rope, still alive. IUCN says that adult males can be found in marine waters, down to depths of twenty metres.
- ^ M, Wikelski; Thom, C. (Jan 6 2000). "Marine iguanas shrink to survive El Niño". Nature 403 (6765): 37-8. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 10638740.
- ^ Rassman K, Tautz D, Trillmich F, Gliddon C (1997), The micro - evolution of the Galápagos marine iguana Amblyrhynchus cristatus assessed by nuclear and mitochondrial genetic analysis. : Molecular Ecology 6:437–452
- ^ Marine Iguana: marinebio.org. Retrieved 16 August 2006.
External links
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