Examine individual changes

'{{speciesbox | name = Marine iguana | image = Iguana marina (Amblyrhynchus cristatus), Las Bachas, isla Baltra, islas Galápagos, Ecuador, 2015-07-23, DD 23.JPG | genus = Amblyrhynchus | parent_authority = [[Thomas Bell (zoologist)|Bell]], 1825 | species = cristatus | authority = ([[Thomas Bell (zoologist)|Bell]], 1825) | status = VU | status_system = IUCN3.1 | status_ref = <ref name="iucn">{{IUCN2012.1|assessor=Nelson, K.|assessor2=Snell, H.|assessor3=Wikelski, M.|last-assessor-amp=yes|year= 2004|id= 1086|title= Amblyrhynchus cristatus|downloaded=2012-09-26}}</ref> | subdivision_ranks = [[Subspecies]] | subdivision = 7 ssp.; see text | range_map = Amblyrhynchus cristatus distribution map.svg }} The '''marine iguana''' (''Amblyrhynchus cristatus'') is an [[iguana]] found only on the [[Galápagos Islands]] that has the ability, unique among modern [[lizard]]s, to forage in the [[sea]], making it a [[marine reptile]]. The iguana can dive over {{convert|9|m|abbr=on}} into the water. It has spread to all the islands in the [[archipelago]], and is sometimes called the '''Galápagos marine iguana'''. It mainly lives on the rocky Galápagos shore to warm from the comparatively cold water, but can also be spotted in marshes and [[mangrove]] [[beach]]es. [[File:Iguana marina (Amblyrhynchus cristatus), Las Bachas, isla Santa Cruz, islas Galápagos, Ecuador, 2015-07-23, DD 27.jpg|upright|thumb|Marine iguana in Las Bachas, Baltra Islands, Galápagos, Ecuador]] ==Subspecies== Listed alphabetically.<ref>[http://reptile-database.reptarium.cz/species?genus=Amblyrhynchus&species=cristatus&search_param=%28%28genus%3D%27Amblyrhynchus%27%2Cexact%29%29 ''Amblyrhynchus cristatus''], Reptile Database</ref> * ''A. c. albemarlensis'' <small>Eibl-Eibesfeldt, 1962</small> – [[Isabela Island (Galápagos)|Isabela Island]] * ''A. c. cristatus'' <small>Bell, 1825</small> – [[Fernandina Island]] * ''A. c. hassi'' <small>Eibl-Eibesfeldt, 1962</small> – [[Santa Cruz Island (Galápagos)|Santa Cruz Island]] * ''A. c. mertensi'' <small>Eibl-Eibesfeldt, 1962</small> – [[San Cristóbal Island|San Cristóbal]] and [[Santiago Island (Galápagos)|Santiago]] Islands * ''A. c. nanus'' <small>Garman, 1892</small> – [[Genovesa Island]] * ''A. c. sielmanni'' <small>Eibl-Eibesfeldt, 1962</small> – [[Pinta Island]] * ''A. c. venustissimus'' <small>Eibl-Eibesfeldt, 1956</small> – [[Española Island]] (and adjacent tiny Gardener Island) <gallery> File:Marine Iguana Isabela Elizabeth Bay.jpg|''A. c. albemarlensis'' File:Marine Iguana (A. c. cristatis), male, Fernandina Island.jpg|''A. c. cristatus'' File:Marine Iguana (A. c. hassi), male, Santa Cruz Island.jpg|''A. c. hassi'' File:Marine Iguana (A. c. mertensi), Santiago Island, Ecuador.jpg|''A. c. mertensi'' File:Marine Iguana (A. c. nanus), male, Genovesa Island.jpg|''A. c. nanus'' File:Marine-Iguana-Espanola.jpg| ''A. c. venustissimus'' </gallery> ==Characteristics== [[File:Marine Iguana swimming, Fernandina, Punta Espinosa.jpg|thumb|Marine iguana swimming]] [[File:Iguana marina (Amblyrhynchus cristatus), Las Bachas, isla Santa Cruz, islas Galápagos, Ecuador, 2015-07-23, DD 19.jpg|thumb|Galapagos marine iguana walking]] On his visit to the islands, despite making extensive observations on the creatures, [[Charles Darwin]] was revolted by the animals' appearance, writing: :''The black Lava rocks on the beach are frequented by large (2–3&nbsp;ft'' [{{Convert|2|-|3|ft|disp=out|sigfig=1}}]''), disgusting clumsy Lizards. 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.''<ref name="Darwin2">{{Cite book | last = Darwin | first = Charles | authorlink = Charles Darwin | title = Charles Darwin's Beagle Diary | publisher = Cambridge University Press | location= London | pages = 494 | year = 2001| isbn = 0-521-00317-2 | postscript = <!--None--> }}</ref> Marine iguanas are medium-sized lizards ({{Convert|200|-|340|mm|abbr=on}}, adult snout–vent length) and are unique as they are marine reptiles due to their foraging on inter- and subtidal algae only. These iguanas forage exclusively in the cold sea, which leads them to behavioral adaptations for thermoregulation.<ref name="ReferenceA">{{cite journal|last1=Jasmina|first1=Hugi|last2=Marcelo R.|first2=Sánchez-Villagra|title=Life History and Skeletal Adaptations in the Galapagos Marine Iguana (Amblyrhynchus cristatus) as Reconstructed with Bone Histological Data—A Comparative Study of Iguanines|journal=Journal of Herpetology|date=2012|volume=46|issue=3|pages=312–324|doi=10.1670/11-071 }}</ref> ''Amblyrhynchus cristatus'' is not always black; the young have a lighter coloured dorsal stripe, and some adult specimens are grey, and adult males vary in colour with the season. Dark tones allow the lizards to rapidly absorb heat to minimize the period of [[lethargy]] after emerging from the water. The marine iguana lacks agility on land but is a graceful swimmer. Its laterally flattened tail and spiky dorsal fin aid in propulsion, while its long, sharp claws allow it to hold onto rocks in strong currents.<ref name="Vitousek, M.N. 2007 pp. 491-507">Vitousek, M.N., Rubenstein, D.R., Wikelski, M. (2007). The evolution of foraging behavior in the Galápagos marine iguana: natural and sexual selection on body size drives ecological, morphological, and behavioral specialization. In Lizard Ecology: The Evolutionary Consequences of Foraging Mode, S.M. Reilly, McBrayer, L.D., Miles, D.B., ed. (New York: Cambridge University Press), pp. 491-507.</ref> ===Body size and longevity=== Marine iguanas vary in body 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. On the other end of the spectrum, the smallest iguanas are found on the island on Genovesa. Adult males weigh from a maximum of {{Convert|12|-|13|kg|abbr=on}} on southern Isabela to about {{Convert|1|-|2|kg|abbr=on}} on Genovesa. The reason for this difference in body size of marine iguanas between islands is due to "variability in algal productivity and sea surface temperature." <ref name="Lizard Ecology">{{cite book|editor1-last=Reilly|editor1-first=Stephen M.|editor2-last=McBrayer|editor2-first=Lance D.|editor3-last=Miles|editor3-first=Donald B.|title=Lizard Ecology|date=2007|publisher=Cambridge University Press|location=New York|pages=491–507|chapter=16: The Evolution of Foraging Behavior in the Galápagos Marine Iguana: Natural and Sexual Selection on Body Size Drives Ecological, Morphological, and Behavioral Specialization}}</ref> Marine iguanas are sexually dimorphic with adult males weighing about 70% more than adult females.<ref name="ReferenceB">{{cite journal|last1=W. A.|first1=Laurie|last2=D.|first2=Brown|title=Population Biology of Marine Iguanas (Amblyrhynchus cristatus). II. Changes in Annual Survival Rates and the Effects of Size, Sex, Age and Fecundity in a Population Crash|journal=Journal of Animal Ecology|date=June 1990|volume=59|issue=2|pages=529–544|doi=10.2307/4879}}</ref> There is a correlation between longevity and body size, particularly for adult males. Large body size in males is selected sexually, but can be detrimental during [[El Niño]] events when resources are scarce. This results in large males suffering higher mortality than females and smaller adult males. The mortality rates of marine iguanas are, in fact, explained through the size difference between the sexes.<ref name="ReferenceB"/> ===Reproduction=== [[File:Amblyrhynchus cristatus 1.jpg|thumb|Marine iguanas in the Galápagos Islands]] Reproduction in the marine iguana begins during the cold and dry season. Female marine iguanas reach sexual maturity at the age of 3–5 years, while males reach sexual maturity at the age of 6–8 years. Sexual maturity is marked by the first steep and abrupt decline in bone growth cycle thickness.<ref name="ReferenceA"/> Males are selected by females on the basis of their body size. Females display a stronger preference for mating with bigger males.<ref>{{cite journal|first1=Martin|last1=Wikelski|first2=Fritz|last2=Trillmich|title=Body Size and Sexual Size Dimorphism in Marine Iguanas Fluctuate as a Result of Opposing Natural and Sexual Selection: An Island Comparison|journal=Evolution|date=June 1997|volume=51|issue=3|pages=922–936|doi=10.2307/2411166}}</ref> During the breeding season, males defend the leks, and roughly one month after copulation, females lay between one and six eggs. The eggs "take three months to incubate in nests dug {{Convert|30|-|80|cm|abbr=on}} deep in sand or volcanic ash." <ref name="ReferenceB"/> It is precisely because of body size that reproductive performance increases and "is mediated by higher survival of larger hatchlings from larger females and increased mating success of larger males."<ref>{{cite journal|first1=Martin|last1=Wikelski|first2=L. Michael|last2=Romero|title=Body Size, Performance and Fitness in Galapagos Marine Iguanas|journal=Integrative and Comparative Biology|date=2003|volume=43|pages=376–386|doi=10.1093/icb/43.3.376 }}</ref> ===Diet=== The marine iguana forages exclusively on inter- and subtidal algae, and 4–5 red algal species are their food of choice. During [[neap tide|neap low tides]], however, the usually avoided ''[[Ulva lobata]]'', also known as green algae, is eaten more often since the preferred red algae are not easily available.<ref name="ReferenceC">{{cite journal|last1=Scoresby A.|first1=Shepherd|last2=Michael W.|first2=Hawkes|title=Algal Food Preferences and Seasonal Foraging Strategy of the Marine Iguana, Amblyrhynchus Cristatus, on Santa Cruz, Galápagos|journal=Bulletin of Marine Science|date=2005|volume=77|issue=1|pages=51–72}}</ref> This algal diet varies in accordance to the algal abundance, preferences, and foraging behaviour. Only 5% of marine iguanas dive for algae offshore, and these individuals are the large males. This behaviour is advantageous because these males experience less competition for food from smaller males and females, who are restricted to foraging during low tide.<ref name="Vitousek, M. N. 2007 pp. 491-507"/> Foraging behavior changes in accordance to the seasons and foraging efficiency increases with temperature.<ref name="ReferenceC"/> These environmental changes and the ensuing occasional food unavailability have caused marine iguanas to evolve by acquiring efficient methods of foraging in order to maximize their energy intake and body size.<ref name="Lizard Ecology"/> In fact, during an [[El Niño]] cycle in which food diminished for two years, some were found to decrease their length by as much as 20%. When food supply returned to normal, iguana size followed suit. It is speculated that the bones of the iguana actually shorten as shrinkage of connective tissue could only account for a 10% change in length.<ref>{{cite journal | first = Wikelski| last = M |author2=Thom, C. | date = Jan 6, 2000 | title = Marine iguanas shrink to survive El Niño | journal = Nature | volume = 403 | issue = 6765 | pages = 37–8 | pmid = 10638740 | doi = 10.1038/47396}}</ref> The physical structure of the iguana also facilitates foraging as they have “long claws, tough skin, blunt heads, flattened tails, and well-developed salt glands.” A flat snout and sharp teeth enable it to browse on algae growing on rocks.<ref name="ReferenceC"/> A nasal gland filters its blood for excess salt ingested while eating, which is expelled through the nostrils, often leaving white patches of salt on its face. ===Behavior=== [[File:Marineiguanas.JPG|thumb|Marine iguanas basking on Fernandina, Galápagos Islands]] As an ectothermic animal, the marine iguana can spend only a limited time in cold water diving for algae. Afterwards it basks in the sun to warm up. Until it can do so it is unable to move effectively, making it vulnerable to predation. However, this is counteracted by their highly aggressive nature consisting of biting and expansive bluffs when in this disadvantageous state. Their dark shade aids in heat reabsorption.<ref>{{cite web|last1=Kristi|first1=Roy|title=Amblyrhynchus cristatus: Marine Iguana|url=http://animaldiversity.ummz.umich.edu/accounts/Amblyrhynchus_cristatus/|website=Animal Diversity Web}}</ref> Fights sometime occur during the breeding season but are generally harmless; males will bob their heads as a threat and if the other suitor responds, both will thrust their heads together until one backs away.<ref name = cornell /> ==Evolutionary history== Researchers theorize that [[Galapagos Land Iguana|land iguanas]] and marine iguanas evolved from a common [[ancestor]] since arriving on the islands from [[South America]], presumably by [[Oceanic dispersal|rafting]].<ref>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'''</ref><ref>[http://marinebio.org/species.asp?id=165 Marine Iguana]: '''[http://marinebio.org/ marinebio.org]'''. Retrieved 16 August 2006.</ref> The marine iguana diverged from the land iguana some 8 million years ago, which is older than any of the extant Galapagos islands.<ref name = amnh>{{cite web | title = Explaining the Divergence of the Marine Iguana Subspecies on Espa | url = http://www.amnh.org/learn-teach/young-naturalist-awards/winning-essays2/2004-winning-essays/explaining-the-divergence-of-the-marine-iguana-subspecies-on-espa | accessdate = 24 October 2014}}</ref> It is therefore thought that the ancestral species inhabited parts of the [[volcano|volcanic]] archipelago that are now submerged. The two species remain mutually fertile in spite of being assigned to distinct genera, and they occasionally [[Hybrid iguana|hybridize]] where their ranges overlap. The subspecies of the marine iguana are identifiable by their sizes as well as by distinct colorations. For example, the Espanola race is redder while the Santiago iguanas are greener.<ref name = cornell>{{cite web | title = Marine Iguanas | url = http://www.geo.cornell.edu/geology/GalapagosWWW/MarineIguanas.html | accessdate = 20 December 2013}}</ref> The marine iguanas may appear to have a light colored face, but in fact, this is due to salt from specialised cranial exocrine glands, expelled from the body in a process much like sneezing. This salt becomes encrusted on their faces. This adaptation allows them to excrete excess salt due to foraging on marine algae.<ref name = cornell/> Although the marine iguana resembles a lizard, it has developed several adaptations that set it apart. These include blunt noses for efficiently grazing seaweed, powerful limbs and claws for climbing and holding onto rocks, and laterally flattened tails for improved swimming.<ref name = arkive>{{cite web | title = Galapagos Marine Iguana | url = http://www.arkive.org/galapagos-marine-iguana/amblyrhynchus-cristatus/ | accessdate = 24 October 2014}}</ref> Compared to the [[Galapagos Land Iguana|land iguana]] its limb bones, especially those from the front limbs, have become more heavy and compact ([[osteosclerosis]]), providing ballast to help with diving.<ref>{{cite journal | last1 = Hugi | first1 = J. | last2 = Sanchez-Villagra | first2 = M. R. | year = 2012 | title = Life History. and Skeletal Adaptations in the Galapagos Marine Iguana (Amblyrhynchus cristatus) as Reconstructed with Bone Histological Data-A Comparative Study of Iguanines | url = | journal = Journal of Herpetology | volume = 46 | issue = 3| pages = 312–324 | doi=10.1670/11-071}}</ref> The marine iguana has no evolved defences against introduced predators. These include rats, which tend to feed on the eggs, cats, which can feed on juveniles, and dogs which may threaten adults.<ref name = cornell/> ==Taxonomy and etymology== Its [[genus|generic]] name, ''Amblyrhynchus'', is a combination of two [[Ancient Greek|Greek]] words, Ambly- from ''Amblus'' (ἀμβλυ) meaning "blunt" and ''rhynchus'' (ρυγχος) meaning "snout". Its [[species|specific]] name is the [[Latin]] word ''cristatus'' meaning "crested," and refers to the low crest of spines along the animal's back. ''Amblyrhynchus'' is a [[monotypic]] [[genus]], having only one species, ''Amblyrhynchus cristatus''. ==Endangered Species List== [[File:Marine iguana red.JPG|thumb|A colourful adult male marine iguana (''Amblyrhynchus cristatus'')]] The marine iguana is currently labeled as vulnerable in its conservation status. The iguana is only known to be living in the Galapagos Islands and its population has been gradually decreasing throughout the years. Since the environment in which they live didn't have many natural predators they never developed the defenses needed to help protect them against new enemies. This lack of development makes them more vulnerable to attack and becoming ill due to new bacteria as these islands attract more and more people and animals from different parts of the world. Although unintentional, human beings pose one of the most serious threats to this species. The marine iguana has evolved over time in an isolated environment and lacks immunity to many pathogens. As a result, the iguanas are at higher risk of contracting infections, contributing to their endangerment.<ref>{{cite journal|last1=French|first1=Susannah|last2=DeNardo|first2=Dale|last3=Greives|first3=Timothy|last4=Strand|first4=Christine|last5=Demas|first5=Gregory|title=Human disturbance alters endocrine and immune responses in the Galapagos marine iguana (Amblyrhynchus cristatus)|journal=Hormones and Behavior|date=Nov 2010|volume=58|issue=5|pages=792–799|url=http://apps.webofknowledge.com/full_record.do?product=WOS&search_mode=GeneralSearch&qid=4&SID=4BgGUKx67aV9nKQYOk3&page=2&doc=13#|accessdate=October 23, 2014|doi=10.1016/j.yhbeh.2010.08.001}}</ref> Other predators include animals such as pigs, dogs, and cats. These animals, though they usually pose little threat to adult iguanas, do impact their reproduction by feeding off their eggs. This inhibits reproduction and the long-term survival of the species.<ref>{{cite journal|last1=Berger|first1=Silke|last2=Wikelski|first2=Martin|last3=Romero|first3=Michael|last4=Kalko|first4=Elisabeth|last5=Roedl|first5=Thomas|title=Behavioral and physiological adjustments to new predators in an endemic island species, the Galapagos marine iguana|journal=Hormones and Behavior|date=Dec 2007|volume=52|issue=5|pages=653–663|doi=10.1016/j.yhbeh.2007.08.004|url=http://apps.webofknowledge.com/full_record.do?product=WOS&search_mode=GeneralSearch&qid=1&SID=4BgGUKx67aV9nKQYOk3&page=1&doc=3|accessdate=23 October 2014}}</ref> ==Conservation== The marine iguana is completely protected under the laws of [[Ecuador]], and is listed under [[CITES]] Appendix II. The total population size is unknown, but the International Union of Conservation of Nature estimates that at least 50,000 exist, while estimates from the [[Charles Darwin Research Station]] are in the hundreds of thousands. [[File:The marine iguana (Amblyrhynchus cristatus) Galápagos Islands Santa Cruz.JPG|thumb|The marine iguana (''Amblyrhynchus cristatus'') Galápagos Islands Santa – swimming in Puerto Ayora]] Studies and research have been done on Galapagos marine iguanas that can help and promote conservation efforts to preserve the endemic species. Monitoring levels of marine algae, both dimensionally and hormonally, is an effective way to predict the fitness of the marine iguana species. Exposure to tourism affects marine iguanas, and corticosterone levels can predict their survival during El Niño events.<ref>{{cite journal | last1 = Stevenson | first1 = R. D. | last2 = Jr Woods | first2 = William A. | year = 2006 | title = Condition Indices For Conservation: New Uses For Evolving Tools | url = | journal = Integrative & Comparative Biology | volume = 46 | issue = 6| pages = 1169–1190 | doi=10.1093/icb/icl052}}</ref> Corticosterone levels in species measure the stress that they face in their populations. Marine iguanas show higher stress-induced corticosterone concentrations during famine (El Niño) than feast conditions (La Niña). The levels differ between the islands, and show that survival varies throughout them during an El Niño event. The variable response of corticosterone is one indicator of the general public health of the populations of marine iguanas across the Galapagos Islands, which is a useful factor in the conservation of the species.<ref>{{cite journal | last1 = Romero | first1 = Michael L. Wikelski Martin | year = 2001 | title = Corticosterone Levels Predict Survival Probabilities of Galapagos Marine Iguanas during El Nino events | url = | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 98 | issue = 13| pages = 7366–70 | doi=10.1073/pnas.131091498}}</ref> Another indicator of fitness is the levels of glucocorticoid. Glucocorticoid release is considered beneficial in helping animals survive stressful conditions, while low glucocorticoid levels are an indicator of poor body condition. Species undergoing a large measure of stress, resulting in elevated glucocorticoid levels can cause complications such as reproduction failure. Human activity has been considered a cause of elevated levels of glucocorticoid in species. Results of a study show that marine iguanas in areas central to tourism are not chronically stressed, but do show lower stress response compared to groups undisturbed by tourism. Tourism, thus, does affect the physiology of marine iguanas. Information of glucocorticoid levels are good monitors in predicting long term consequences of human impact.<ref>{{cite journal | last1 = Romero | first1 = Michael L. Wikelski | last2 = Martin | first2 = | year = 2002 | title = Exposure to Tourism Reduces Stress-induced Corticosterone Levels in Galapagos Marine Iguanas | url = | journal = Biological Conservation | volume = 108 | issue = 3| pages = 371–374 | doi=10.1016/s0006-3207(02)00128-3}}</ref> ==See also== {{Portal|Biology|Amphibians and Reptiles|Ecuador}} *[[Hybrid Iguana]] ==Bibliography== * Rothman, Robert, ''[http://people.rit.edu/rhrsbi/GalapagosPages/MarineIguana.html Marine Iguana]'' Galapagos Pages. Rochester Institute of Technology. Retrieved 19 April 2009. ==References== {{reflist|30em}} ==External links== {{Commons+cat|Amblyrhynchus cristatus|Amblyrhynchus cristatus}} {{Wikispecies|Amblyrhynchus cristatus}} *[http://ocean.si.edu/ocean-sounds/podcast-life-marine-iguanas Marine Iguana Podcast - Smithsonian Ocean Portal] *[http://www.pgoimages.com/gallery.php?gall=w_iguana Images of Marine and Land Iguanas] *[http://www.galapagosonline.com/nathistory/wildlife/animals/iguana.htm Iguanas of the Galapagos www.galapagosonline.com] *[http://www.arkive.org/galapagos-marine-iguana/amblyrhynchus-cristatus/ ARKive videos and slide show] {{Iguanidae}} {{taxonbar}} [[Category:Iguanidae]] [[Category:Marine reptiles]] [[Category:Endemic fauna of the Galápagos Islands|Iguana, Marine]] [[Category:Galápagos Islands coastal fauna]] [[Category:Reptiles of South America|Iguana, Marine]] [[Category:Monotypic reptile genera]] [[Category:Animals described in 1825]]'