Orestias Cuvieri
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The Titicaca orestias, Lake Titicaca orestias, or Lake Titicaca flat-headed fish (''Orestias cuvieri''), also known by its native name amanto, is a likely extinct freshwater killifish from Lake Titicaca in South America. It belongs in the pupfish genus ''
Orestias Orestias ( el, Ὀρεστιάς) was an ancient Greek settlement next to the Maritsa (or Evros) river, near or at the site of present-day Edirne, and close to the current border between Turkey and Greece. Legends claim that Orestias was founded ...
'', endemic to lakes, rivers and streams in the Andean highlands. With a total length of up to , it was the largest member in that genus. In the hope that an undiscovered population remains, it is listed as
Data Deficient A data deficient (DD) species is one which has been categorized by the International Union for Conservation of Nature (IUCN) as offering insufficient information for a proper assessment of conservation status to be made. This does not necessaril ...
by the
IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
. Despite its common name, it is not the only ''Orestias'' from Lake Titicaca. Its mouth was nearly turned upwards, thereby giving the flat head a concave shape. The head took up nearly a third of the whole body length. The upperside was greenish-yellow to umber. The lower jaw was black. Its scales were oddly light coloured at their centre. The scales of the young were blotched. The Titicaca orestias became extinct due to competition by introduced trout like the lake trout,
brown trout The brown trout (''Salmo trutta'') is a European species of salmonid fish that has been widely introduced into suitable environments globally. It includes purely freshwater populations, referred to as the riverine ecotype, ''Salmo trutta'' morph ...
, or the
rainbow trout The rainbow trout (''Oncorhynchus mykiss'') is a species of trout native to cold-water tributaries of the Pacific Ocean in Asia and North America. The steelhead (sometimes called "steelhead trout") is an anadromous (sea-run) form of the coasta ...
as well as Argentinian silverside from the 1930s to the 1950s. A survey in 1962 failed to find any Titicaca orestias.


History

''Orestias cuvieri'' is a species of killfish that belongs in the genus ''
Orestias Orestias ( el, Ὀρεστιάς) was an ancient Greek settlement next to the Maritsa (or Evros) river, near or at the site of present-day Edirne, and close to the current border between Turkey and Greece. Legends claim that Orestias was founded ...
''. Other related species of ''Orestias'' live in the region, forming a
species flock In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...
.


Anatomy

The Titicaca orestias was characterized by a unique pattern of pores on the head. Large thick scales lined the median dorsal ridge and thinner smaller scales surrounded the ridge. Between these two areas of skin were patches with no scales. Unlike most other species of ''Orestias'', the scales of the adult ''O. cuvieri'' were granulated. The concave dish shape of its body and jaw further helped distinguish ''O. cuvieri'' from other species of ''Orestias''. The anatomy of ''O. cuvieri'' closely resembled a species of trout which is now found in Lake Titicaca, a similarity which has led many researchers to hypothesize that competition between the two groups was the reason for the extinction of ''O. cuvieri''.


Size

Each species of ''Orestias'' has varying size. The Titicaca orestias was the largest species in the genus. The maximum recorded size is in
standard length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish m ...
and in total length, which is considerably larger than most other species; only '' O. pentlandii'' at up to and , respectively, comes close.


Coloration and markings

With regard to the coloration of the amanto during their lifetime, specimens present black melanophores laterally as a band on the lateral line and as small groups on the upper lateral sides. Small melanophores cover the fins giving them a grayish color. The grayish color fades to white on the dorsum and belly; juvenile pigmentation pattern persists with little modification in adult males and females. This information shows that the color of the Orestias in question depends on what part of the body is being considered.


Life history


Reproduction

Nothing has been published about the reproduction of the Titicaca orestias, but in other ''Orestias'' species of Lake Titicaca, the males become more orange or yellow in color when they are spawning. During their reproductive stage, the females lay somewhere between 50 and 400 eggs, each of which has a yellowish filament up to about 2.5 mm in diameter. As an adaptation to solar radiation, the eggs develop a black protective coat, derived from melanophores, around the embryo sac.


Ecology


Range and habitat

The freshwater fish belonging to the genus ''Orestias'' are found in high-altitude isolated lakes in the Altiplano region of South America, ranging from Peru to Chile. Lake Titicaca, which is on the border of Peru and Bolivia, contains a wide variety of ''Orestias'' fish. This large lake was once the home to ''Orestias cuvieri'' before their extinction.


Population, trends and predation

At one time, there were as many as 30 native fish species in Lake Titicaca, of which 28 species belonged to the genus ''Orestias''. In the middle of the 20th century, there were many attempts to introduce exotic species to the lake. Two of these introductions were successful: rainbow trout introduced in 1942 and silverside ('' Odontesthes bonariensis'') in the early 1950s. The success of the silverside meant the decline of the Titicaca orestias, since the larger silversides were observed to eat them. As long as the silverside continued to flourish, it meant difficult times for the amanto. Fifty years ago, there was no sign of ''Orestias cuvieri'' in Lake Titicaca and the species was presumed to be extinct.


Feeding

''O. cuvieri'' mainly ate smaller fish.


Human interaction

Since the
Miocene era The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
, species of ''Orestias'' have lived in relative isolation. Most of the aquatic regions in the Altiplano region are endorheic, meaning that they are closed off from drainage and do not let any water out. Thus, species of ''Orestias'' have been confined to their respective basins. Each group of fish is specifically adapted to the unique basin in which it lives and any alteration to the dynamics of the body of water would greatly impact the fish. Human introduction of foreign fishes to the Altiplano basins predictably had negative consequences. The alien species created competition and preyed upon ''Orestias cuvieri'', eventually leading to its extinction. Pollutants contaminate the water and traces of metals, such as zinc and copper, have been found in the tissues of fishes. In addition, runoff from fertilizers and pesticides used in agricultural lands has been extremely toxic to the fish. The water from the Altiplano region is also in high demand. People have constantly been taking water out of the basins and depleting the ''Orestias habitats. The compilation of the effects of human actions have harmfully affected the health and survival of different species of ''Orestias'', in particular the species ''O. cuvieri''. Thus, the extinction of the Titicaca orestias is largely
anthropogenic Anthropogenic ("human" + "generating") is an adjective that may refer to: * Anthropogeny, the study of the origins of humanity Counterintuitively, anthropogenic may also refer to things that have been generated by humans, as follows: * Human im ...
.


Conservation


Law enforcement

With regard to law enforcement, major efforts are still needed to prevent pollution and illegal fishing. These efforts need to be made specifically on the area, between Peru and Bolivia, of Lake Titicaca. ''O cuvieri'' has likely already become extinct. Other native species, including the suche (''
Trichomycterus rivulatus ''Trichomycterus rivulatus'' is a species of pencil catfish that is native to high-altitude Andean streams and lakes (including Junin, Poopó and Titicaca) in southern Peru, western Bolivia and northern Chile. It is the largest species in the g ...
''), boga ('' O. pentlandii''), yellow karachi ('' O. albus'') and ispi ('' O. ispi''), are threatened to various degrees, as a result of overfishing, predation by introduced species, and the impacts of intensive production in trout farms.Chavez, Franz. 2011. Major Efforts Still Needed to Clean Up Lake Titicaca. News International. Global Reach Press. This idea of law enforcement is particularly challenging because of the immense body of water that would need patrolling. Actions to be on the lookout for by law enforcement should include long casting; where a long line (over 100 kilometers in some instances) is cast and other unintended fish are caught. Perhaps more importantly though is to be on the lookout, as an entity of law enforcement for pollution.


Museum specimens

The National Museum of Natural History in the Netherlands,
Naturalis Naturalis Biodiversity Center ( nl, Nederlands Centrum voor Biodiversiteit Naturalis) is a national museum of natural history and a research center on biodiversity in Leiden, Netherlands. It was named the European Museum of the Year 2021. Alth ...
, has several specimens. Two of these specimens were donated by the Zoological Museum at Heidelberg University in 1877 and one in 1880 from the Smithsonian Institution. In addition, four specimens, labeled "''Orestias humboldi''" were donated by the Muséum national d'histoire naturelle in France.


Related species

Scientists have determined that there are 43 species of the genus ''Orestias''. These species were divided into four groups by the American ichthyologist Lynne R. Parenti in 1984. In 2003, Arne Lüssen researched the phylogeny, including the mtDNA sequence data of many species. The Lake Titicaca orestias, ''O. culvieri'', is a member of the ''cuvieri'' species complex, which also includes '' O. forgeti'', ''O. ispi'' and ''O. pentlandii''.


References

{{Taxonbar, from=Q454534
Titicaca orestias The Titicaca orestias, Lake Titicaca orestias, or Lake Titicaca flat-headed fish (''Orestias cuvieri''), also known by its native name amanto, is a likely extinct freshwater killifish from Lake Titicaca in South America. It belongs in the pupfish ...
Fish of Bolivia Freshwater fish of Peru Lake fish Fish described in 1846 Taxa named by Achille Valenciennes