Orestias (fish)

Orestias is a genus of pupfish. Older systematics classified them into the own family Orestiidae. They are found in lakes, rivers and springs in the Andean highlands of South America, and several species are considered threatened.[2] They are egg-laying fish that feed on small animals and plant matter.[3][4] The largest species can reach a total length of 27 cm (10.6 in), but most remain far smaller.[5][6] Their most characteristic feature is the absence of the ventral fin, although this is shared by a few other pupfish.[6] Despite their moderate to small size, they are important to local fisheries and a few species are farmed.[7]

Orestias
Orestias cuvieri
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cyprinodontiformes
Family: Cyprinodontidae
Genus: Orestias
Valenciennes, 1839
Type species
Orestias cuvieri
Valenciennes, 1846[1]

Several species are locally and colloquially known as carache. The name of the genus is a reference to Orestes, a Greek mythological character who Valenciennes described as the "nymph of the mountains".[8]

Range and habitat
Four Orestias (possibly O. luteus) and two Trichomycterus catfish caught in Lake Titicaca, the center of Orestias richness

Orestias is restricted to freshwater habitats at an altitude of 2,800–4,600 m (9,200–15,100 ft) in the Andes of central and southern Peru, western Bolivia, and northeastern Chile.[2] Although freshwater habitats at low and middle altitudes in the Andes are relatively rich in fish, few are found in the highest, with Orestias and the catfish Astroblepus and Trichomycterus being the primary—in many places only—native genera.[4][9] Of the 45 recognized species of Orestias, the majority are found in Lake Titicaca (including 23 endemics to its basin), with the remaining from other Altiplano lakes, rivers or springs.[2] In addition to differences in feeding, the many species in Lake Titicaca segregate by habitat preference, with some living among totora reeds, some among submerged macrophytes, some at the bottom in water too deep for macrophytes (deeper than 10 m or 33 ft), and some pelagically in the open water.[10] Orestias species found elsewhere than Lake Titicaca often have very small ranges.[2]

Behavior

Relatively little is known about the behavior of Orestias.[4]

They feed on small crustaceans (such as amphipods and cladocera), aquatic insects and larvae (such as chironomids), snails, small fish, fish eggs, algae, macrophyte seeds and plant detritus.[3][11][12] There are significant variations depending on exact species, especially in Lake Titicaca where there is a degree of niche differentiation, including some that mainly feed on zooplanktonic organisms, two (O. albus and O. cuvieri) that are particularly willing to take other fish, primarily smaller Orestias (fish eggs are regularly consumed by a wider range of species), several that mainly feed on small bottom- or plant-living organisms, and some that are generalists that will feed on a wide range of things,[3][4][10][12] sometimes varying depending on season.[11]

Females tend to grow larger than males. Although generally rather dull-coloured, breeding males may become partially yellow or orange. The eggs, up to a few hundred, are placed in shallow water among vegetation. Orestias appear to reach maturity when around one year old.[4]

Conservation and relationship to humans

Many species of the genus became rare in recent decades due to predation by, and competition with introduced fish species (especially rainbow trout and Argentinian silverside), pollution, overfishing and other human activities in their habitats.[13][14] In the 1960s, an expedition to Lake Titicaca led by Jacques Cousteau reported seeing many dead Orestias and when studied they were found to be infected by a disease introduced with the trout.[15]

The two largest species in the genus, the Titicaca orestias (O. cuvieri) at up to 22 cm (8.7 in) in standard length and 27 cm (10.6 in) in total length, and O. pentlandii up to 20 cm (7.9 in) and 23.5 cm (9.3 in) respectively,[5][6] have fared the worst. The Titicaca orestias was last seen in 1939 and is almost certainly extinct.[13] O. pentlandii is from the same lake and it may have disappeared in its native form.[14] It was still regarded as "only" vulnerable by the IUCN in 2009, but in 2014 the species was regarded as critically endangered in a review of Lake Titicaca fish.[13] In the 1990s, some were introduced to a small highland lake in Peru in an attempt of safeguarding the species, but over time they have changed (possibly due to genetic drift, inbreeding depression, or their new and different habitat) and now appear very different from the original O. pentlandii of Lake Titicaca.[16] The remaining Orestias of Lake Titicaca are also threatened to various degrees,[13][14] as are the three species in Lake Junin and its vicinity,[9] which in turn may threaten the Lake Junin giant frog that feeds on the fish and invertebrates.[17] Many Orestias found elsewhere are vulnerable because of their highly restricted ranges,[6] like O. ascotanensis where the entire habitat covers 18 km2 (7 sq mi) of Salar de Ascotán and O. chungarensis found only in Lake Chungará.[18][19]

Despite their moderate to small size, some species are important to local fisheries, but they are overfished, there are few regulations and limited enforcement of the rules that do exist.[14][16] In Lake Titicaca, the moderately sized O. agassizii and O. luteus (complexes) represent more than 90% of the total catches of native fish species,[7] but others like the small open-water ispi (O. forgeti and O. ispi) are also frequently caught.[20] The natives have now been greatly surpassed by fisheries for the non-native introduced trout and Argentinian silverside.[14] Because of pollution, studies have revealed levels of metals in Orestias of Lake Titicaca that exceed the internationally recommended safety thresholds for human consumption.[21] O. agassizii and O. luteus are also farmed and spawned in captivity; both to supply the food market and for release to support their vulnerable wild populations.[7][22]

Species and taxonomy
Three Orestias species showing some of the variations in shape in this genus

There are currently 45 recognized species in this genus,[5] divided depending on their relationships into four species complexes.[6] The genus is estimated to be 5 million years old, with a significant diversification occurring within the last one million years. Lüssen (2003) researched the phylogeny of several species including mtDNA sequence data; because hybridization is known to occur (Villwock 1964, Parenti 1984), mtDNA data cannot be relied upon on its own to resolve the evolution of this genus. For example, O. agassizii and O. luteus reach a similar maximum standard length of c. 17 cm (6.5 in),[21] but otherwise they are quite different. Despite this, hybrids between them are known.[7]

Agassizii species complex

Some species restricted to the Lake Titicaca basin (which includes the inflowing rivers and connected smaller lakes like Arapa, Lagunillas and Saracocha), and some restricted to other lakes, rivers and springs elsewhere in the Andean highlands. O. agassizii (often spelled agassii instead[23]) is the only member of the genus found both in the Lake Titicaca basin and elsewhere.[6]

Cuvieri species complex

All restricted to the Lake Titicaca basin.[6]

Gilsoni species complex

All restricted to the Lake Titicaca basin.[6]

Mulleri species complex

All restricted to the Lake Titicaca basin.[6]

References
  1. Eschmeyer, William N.; Fricke, Ron & van der Laan, Richard (eds.). "Orestias". Catalog of Fishes. California Academy of Sciences. Retrieved 20 October 2019.
  2. Vila, Morales, Scott, Poulin, Veliz, Harrod and Mendez (2013). Phylogenetic and phylogeographic analysis of the genus Orestias (Teleostei: Cyprinodontidae) in the southern Chilean Altiplano: the relevance of ancient and recent divergence processes in speciation. Journal of Fish Biology 82, 927–943.
  3. Maldonado, E.; N. Hubert; P. Sagnes; B. De MÉrona (2009). "Morphology–diet relationships in four killifishes (Teleostei, Cyprinodontidae, Orestias) from Lake Titicaca". Journal of Fish Biology. 74 (3): 502–520. doi:10.1111/j.1095-8649.2008.02140.x.
  4. Vila, I.; R. Pardo; S. Scott (2007). "Freshwater fishes of the Altiplano". Aquatic Ecosystem Health & Management. 10 (2): 201–211. doi:10.1080/14634980701351395.
  5. Froese, Rainer and Pauly, Daniel, eds. (2012). Species of Orestias in FishBase. August 2012 version.
  6. Parenti, Lynne R. (1984): A taxonomic revision of the Andean Killifish Genus Orestias (Cyprinodontiformes, Cyprinodontidae). Bulletin of the American Museum of Natural History 178: 107-214. PDF fulltext
  7. Esquer-Garrigos, Y.; B. Hugueny; C. Ibañez; C. Zepita; K. Koerner; J. Lambourdière; A. Couloux; P. Gaubert (2015). "Detecting natural hybridization between two vulnerable Andean pupfishes (Orestias agassizii and O. luteus) representative of the Altiplano endemic fisheries". Conservation Genetics. 16 (3): 717–727.
  8. Christopher Scharpf; Kenneth J. Lazara (26 April 2019). "Order CYPRINODONTIFORMES: Families PANTANODONTIDAE, CYPRINODONTIDAE, PROFUNDULIDAE, GOODEIDAE, FUNDULIDAE and FLUVIPHYLACIDAE". The ETYFish Project Fish Name Etymology Database. Christopher Scharpf and Kenneth J. Lazara. Retrieved 20 October 2019.
  9. Chocano Arévalo, L. (2005). "Las zonas altoandinas peruanas y su ictiofauna endémica". Revista Digital Universitaria. 6 (8): 1–13.
  10. Lauzanne, L. (1992). "Fish Fauna". In C. Dejoux; A. Iltis (eds.). Lake Titicaca: a synthesis of limnological knowledge. Kluwer Academic Publishers. pp. 405–448. ISBN 0-7923-1663-0.
  11. Loayza, E. (2019). "Seasonal and depth variations in diet composition and dietary overlap between three native killifish of an emblematic tropical-mountain lake: Lake Titicaca (Bolivia)". Retrieved 18 January 2020.
  12. Monroy, M.; A. Maceda-Veiga; N. Caiola; A. De Sostoa (2014). "Trophic interactions between native and introduced fish species in a littoral fish community". Journal of Fish Biology. 85: 1693–1706. doi:10.1111/jfb.12529.
  13. Luna, C.I.; B. Hugueny; Y.S. Esquer-Garrigos; C. Zepita; Y. Gutiérrez (2014). "Biodiversidad ictica en el Lago Titicaca". In M. Aguirre; X. Lazzaro; D. Point; M. Pouilly (eds.). Línea base de conocimientos sobre los recursos hidrológicos e hidrobiológicos en el sistema TDPS con enfoque en la cuenca del Lago Titicaca. IUCN. pp. 135–153. ISBN 978-99974-41-84-3.
  14. Bloudoff-Indelicato, M. (9 December 2015). "What Are North American Trout Doing in Lake Titicaca?". Smithsonian Magazine. Retrieved 18 January 2020.
  15. Cousteau, J.; A. Landsburg (24 April 1969). "The Legend of Lake Titicaca". The Undersea World of Jacques Cousteau. Episode 7.
  16. "Los peces nativos del Titicaca, en peligro". Fundación Nuestra Mar. 3 March 2010. Retrieved 18 January 2020.
  17. Watson, A.S.; A.L. Fitzgerald; O.J. Damián Baldeón (2017). "Diet composition and prey selection of Telmatobius macrostomus, the Junín giant frog". Endangered Species Research. 32: 117–121. doi:10.3354/esr00785.
  18. Cruz-Jofré, F.; P. Morales; I. Vila; Y. Esquer-Garrigos; B. Hugueny; P. Gaubert; E. Poulin; M.A. Méndez (2016). "Geographical isolation and genetic differentiation: the case of Orestias ascotanensis (Teleostei: Cyprinodontidae), an Andean killifish inhabiting a highland salt pan". Biological Journal of the Linnean Society. 17 (4): 747–759. doi:10.1111/bij.12704.
  19. Froese, Rainer and Pauly, Daniel, eds. (2020). "Orestias chungarensis" in FishBase. January 2020 version.
  20. McKittrick, E. (2018). "Saving the Scrotum Frog". Earth Island Journal. Retrieved 27 January 2020.
  21. Sostoa, A.; A. Maceda-Veiga; M. Monroy (2014). "Metal concentration in water, sediment and four fish species from Lake Titicaca reveals a large-scale environmental concern". Biological Science of the Total Environment. 487: 233–244. doi:10.1016/j.scitotenv.2014.03.134.
  22. UNDP (5 March 2019). "Prosper under the sun: Faced with the ever-increasing global demand for renewable energy, two Andean communities in Peru use solar energy to develop sustainable businesses". americalatinagenera.org. Retrieved 18 January 2020.
  23. Eschmeyer, William N.; Fricke, Ron & van der Laan, Richard (eds.). "Species related to Orestias agassii". Catalog of Fishes. California Academy of Sciences. Retrieved 18 January 2020.
  24. Vila, I., Scott, S., Mendez, M.A., Valenzuela, F., Iturra, P. & Poulin, E. (2012): Orestias gloriae, a new species of cyprinodontid fish from saltpan spring of the southern high Andes (Teleostei: Cyprinodontidae). Ichthyological Exploration of Freshwaters, 22 (4) [2011]: 345-353.
  • Lüssen, Arne (2003): Zur Systematik, Phylogenie und Biogeographie chilenischer Arten der Gattung Orestias VALENCIENNES, 1839. Doctoral thesis, University of Hamburg, Germany. [in German] PDF fulltext
  • Villwock, W. (1964): Vermeintliche Artbastarde in der Gattung Orestias (Pisces, Cyprinodontidae). Mitteilungen aus dem Hamburgischen Zoologischen Museum und Institut, Kosswig-Festschrift: 285-291. [Article in German]
  • Villwock, W. (1972): Gefahren für die endemische Fischfauna durch Einbürgerungsversuche und Akklimatisation von Fremdfischen am Beispiel des Titicacas-Sees (Peru/Bolivien) und des Lanao-Sees (Mindanao/Philippinen). Verhandlungen des Internationalen Vereins für Limnologie 18: 1227-1234. [Article in German]
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