Hickatee

Dermatemys mawii is the only living species in the family Dermatemydidae. Its closest relatives are only known from fossils with some 19 genera described from a worldwide distribution in the Jurassic and Cretaceous. Etymology The specific name, mawii, is in honour of the collector of the type specimen, Lieutenant Mawe of the British Navy. This species is usually vernacularly called tortuga blanca in Spanish, because it can be readily distinguished when prepared as food. When the meat of this turtle is cooked, it turns a white colour, unlike the more common turtle meat (Trachemys scripta), which colours dark. Genetics Many species sharing a similar distribution have phylogeographic structure revealed in their genomes, with the population often being split into at least three subgroups representing the three main Atlantic hydrological basins of this region, the Papaloapan, Coatzacoalcos and Grijalva-Usumacinta. A 2011 study of the mitochondrial DNA (mtDNA) of extant populations throughout the range of this species, however, revealed a less clear differentiation. Although some genetic structure was evident, most locations showed a high rate of mixing of different lineages, with two main closely related mitochondrial haplotypes dominating the population. Three divergent mitochondrial lineages were found: an extremely rare one dubbed '1D' only found in four samples from Sarstún and Salinas on the southeast edge of the Grijalva-Usumacinta basin, a second northernmost 'Papaloapan' lineage restricted to the Papaloapan basin in the state of Veracruz, to the west of the Sierra de Santa Marta and the Isthmus of Tehuantepec, and a third widespread 'central' lineage that was found in all studied localities. It appeared as if a formerly clear phylogeographical pattern had been obscured by transport and introductions of turtle populations from one waterway to another, i.e. secondary blurring by large-scale gene flow between populations. Low haplotype diversity at some localities indicated prehistoric population bottlenecks, possibly after a drastic cull from over-harvesting, followed by population expansions. As it is almost certain the Ancient Maya were engaged in long distance trade in this turtle species and consumed large amounts, it was deemed most probable that the Maya were responsible for this (see section on interaction with humans below). Even today, turtles have been found trapped in small isolated ponds (called aguadas in Guatemala) where they would be unlikely to naturally disperse to, or in areas they do not naturally occur, likely moved there by people in order to harvest them at a later date. This 2013 study found no sign of a recent bottleneck in the fifteen locations sampled, indicating that harvesting going for the past half century had not yet had an effect on genomic diversity, possibly a long generation time and delayed sexual maturity of D. mawii buffering against loss of genetic diversity despite population size reduction. The Sarstún and Salinas populations in general were not strongly differentiated from the neighbouring populations, but the four individuals from Sarstún and Salinas with divergent mitochondria did have divergent microsatellite loci sequences in varying amounts according to the individual, with three rare alleles only found in this subpopulation of four. The samples from Papaloapan locations were highly differentiated compared to almost all other populations, and also were rich in unique alleles. However, individuals carrying Papaloapan-type mtDNA haplotypes did not appear differentiated from the central type individuals, and these individuals occurred at relatively low frequencies amongst the central type haplotypes shared with adjacent populations to the east of the isthmus, indicating significant gene flow of mitochondrial lineages westwards across the isthmus. At the same time nuclear microsatellites appear to show gene flow in the other direction. Such conflicting signals could be caused by different episodes, or be due to a sex bias in dispersal. Also the populations from Sibun River, Lake Salpetén and Laguna Sacnab, all near the eastern edge of the distribution, were relatively well-differentiated from the remaining populations. This was thought to be due to losses of genetic variability from recent genetic drift and/or demographic isolation. All the other populations had high levels of gene flow, even between areas separated by geographic distances of more than 300 km. The study found that this suggests likely thousands of years of human-mediated trade, but that it might also just mean that this species is capable of moving great distances during its life. Besides microsatellite regions another part of the nuclear DNA was looked at, a 779 bp fragment of first intron of the RNA protein R35, with four haplotypes found. This revealed no phylogeographic structure: the main haplotype was common across the distribution, and the four individuals from Sarstún and Salinas all had this haplotype. The overall pattern is completely different in the alligator snapping turtle (Macrochelys temminckii), which is also often caught, but in which gene flow between populations is very low, but the mixed lineages are somewhat similar to the diamondback terrapin (Malaclemys terrapin), with translocations during the early twentieth century, or the radiated tortoise (Geochelone radiata) and gopher tortoises (Gopherus polyphemus), which show contemporary population structuring influenced by recent releases. The 2013 study concluded that as there was evidence of substantial genetic mingling the species was best regarded as a single cohesive 'management unit' for conservation purposes, as opposed to Vogt et al. in 2011. The sample size of the individuals with the 1D mitochondria was too small to calculate insofar they represent a taxonomically relevant cryptic species. ==Description==

Dermatemys mawii It is a relatively large-bodied species, with historical records of straight carapace length and weights of ; however, more recent records have found few individuals over in Mexico or in Guatemala. It has a low, flattened, smooth carapace with a median keel present in juveniles, it is usually a uniform brown, almost black, grey or olive in colour. and longer, thicker tails. ==Distribution==

Dermatemys mawii lives in Atlantic-draining larger rivers and lakes in Central America, from southern Mexico through Belize to the Guatemalan-Honduran border. In Guatemala the species occurs from southern and central Petén Department, south to Lago de Izabal and the rivers which drain into it. Very high turtle densities were captured in Laguna Peru in 2007 and 2009. ==Ecology==

Dermatemys mawii is a nocturnal, completely aquatic turtle Campbell in 1998 notes that the otter is itself not common enough for this to be an issue. Crocodiles crush the shell and swallow the turtle whole. A study on the blood of turtles collected in the wild in Pantanos de Centla Biosphere Reserve and a turtle breeding farm, both located in Tabasco, found 100% of the wild turtles were infected with a species of Haemogregarina, a protozoan parasite inhabiting the red blood cells of turtles and spread by leeches. The protozoan was more prevalent during the rainy season. 27% of the wild turtles had leeches feeding off them, with no apparent detrimental effect on the hosts. The captive turtles were uninfected by both, but more unhealthy in other ways, wild turtles were better fed, bigger, and exhibited no real damage to the shell or major wounds. On a turtle farm in Veracruz it was noticed that turtles kept out of water for any period were highly susceptible to a bacterial lung infection. It will also eat fruit and flowers opportunistically. During the rainy season the waters rise a few metres, sometimes many, in some places this brings the leaves and branches of terrestrial trees within the jaws of this turtle and it will largely browse on this during this season, in other places the water floods pastures, and the turtle will primarily graze upon the submerged grass. The habitat appears to be the main factor impacting diet -in many rivers the water is too strong or the waters to muddy to sustain aquatic plant-life, and in these waters the turtles feed on plants growing on the banks. Where the banks are too steep for such plants, here the turtles feed on leaves of overhanging branches. However, it is possible that a combination of a diapause and variable local reproductive cues is responsible for this. There appears to be a primary breeding season timed with the later part of the rainy season (September to December) and a secondary one at the beginning of the dry season (January to February). The species can lay up to 4 clutches per year with an average of 2–20 eggs per clutch; clutch sizes over 15, however, were not common. As this species often buries its eggs in more than one nests with a rather random spatial distribution within one to three metres along a constantly shifting shoreline, the nests are extremely difficult to locate for humans, and finding eggs is very uncommon. In 1989 and 1990, despite nightly searches by a team during two seasons, only two nests were located. Polisar was never able to witness nesting himself, but three accounts from local hunters had the animals nesting within 1.5 metres from the shoreline. In 1996 Polisar published that it was quite possible that the turtles nest underwater like the Australian Chelodina rugosa, a claim repeated as a certainty in later works, but in 2011 Vogt et al. dismiss the claim as invented by 'locals' confused by the constantly rising and falling waters of their homeland. ==Interaction with humans==

Dermatemys mawii has been hunted for food for millennia. Archaeologists have recovered the remains of what appear to be Ancient Mayan feasts, wherein large numbers of turtles were roasted. Such remains are also found in areas, such as the eastern and northern Yucatán, where the species is not believed to occur today. This could be due to import during Mayan times, or represent a distribution it is now extirpated from, or modern scientists simply have not looked properly here. A 2011 study of the mtDNA of extant populations throughout the range of this species indicated that the population was likely highly impacted during Mayan times, and may have even been extirpated from certain areas, only to be restocked from other waterways. The mitochondrial divergences likely represent hydrological reproductive barriers between populations that may have existed for up to three million years, but there is an absence of a clear phylogeographical pattern between the lineages and the collection localities, with different mitochondrial lineages interspersed amongst each other, which shows probable large-scale gene flow between populations. This can be explained by colonisation of the area by imported animals. Haplotype diversity was furthermore found to be quite low in some populations, which was explained as likely the result of bottlenecks resulting from over-harvesting during Mayan followed by population expansions. A recipe from the 1950s or 1960s advises pouring boiling water over the chopped pieces of hickatee to remove the thin skin, seasoning the meat with thyme, black pepper, onion, garlic and vinegar and letting it marinate overnight, cooking in hot oil, mixing with coconut cream and serving with rice. In the Petén highlands of Guatemala it is the most esteemed turtle because of its delicious flesh. ==Conservation==

Dermatemys mawii is a heavily exploited turtle; it is primarily harvested for its meat, exploitation of nesting females and their eggs is inconsequential because the nests are extremely hard to find. The species has been overhunted because it is valued by local people as a food, thus the meat fetches good prices. A countrywide survey of the population in Belize in 1983 and 1984 found that the species was common and abundant in some areas, but declining in population in more human-populated areas. Research in north-central Belize from 1989 through 1991 determined that harvesting rates in human-populated areas were unsustainable. As such, in 1993 the government of Belize instituted a number of new laws meant to control hunting and forbid trade. Hunting was forbidden in a certain closed season, hunters were allowed to bag no more than three turtles, and females above a certain size have to be released. A series of protected zones were established in a number of the major waterways in northern Belize. A 1998 and 1999 survey in north-central Belize found that the species was still common in remote areas, but was also still declining in more populated areas. A 2010 countrywide survey indicated that the population was much the same as in the previous surveys, depressed in human-populated areas, but healthy populations continue to exist in more remote areas. Although there was not much difference between the situation of the population in 2010 compared to the 1980s, there was a general decrease in overall numbers and sighting localities. Interviews with locals indicate the 1993 laws are largely ineffective, hunting continues to be performed with in some areas with hundreds of turtles being caught in small parts of the Belize River, and the traditional Easter dish of the country continues to be served in rural restaurants. As a generalist herbivore fodder costs are low. However, growth rates are low. In 2011 some US scientists mused that commercial breeding might be cost effective using experimental aquatic polyculture systems with the turtles as a secondary income source, and shrimp as the main crop. The turtles could graze on weeds and grasses, and do not harm the shrimp. A three year pilot study was done in Veracruz, after the pond weeds were consumed the turtles were fed grass clippings, and the turtles reproduced each year. A project conducted by TSA on Belize Foundation for Research and Environmental Education property began in early 2011 focused on generating food plants and exploring husbandry details, such as egg laying and incubation. Located in southern Belize along the Bladen River, the property is situated among four protected areas (Bladen Nature Reserve, Cockscomb Basin Jaguar Reserve, Deep River Forest Reserve and Maya Mountain Forest Reserve). The goal of the program was to generate hatchlings and release them for stocking purposes. As of 2006 it was kept at the following zoos: Veracruz Aquarium, Chicago Zoo, Detroit Zoo, Philadelphia Zoo (with the most specimens), and the Guatemala City Zoo (with only one). ==Notes==