''Skiffia francesae'', the golden skiffia or tiro dorado, is a species of

splitfin Goodeidae is a family of teleost fish endemic to Mexico and some areas of the United States. Many species are known as splitfins. This family contains about 50 species within 18 genera. The family is named after ichthyologist George Brown Good ...

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to the Rio Teuchitlán, a tributary of Río Ameca in western

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

. It is extinct in the wild, but has been maintained in aquaria and the aquarium hobbyist trade.

Taxonomy and etymology

The scientific name of the golden skiffia is ''Skiffia francesae''. It is a member of the family

Goodeidae Goodeidae is a family of teleost fish endemic to Mexico and some areas of the United States. Many species are known as splitfins. This family contains about 50 species within 18 genera. The family is named after ichthyologist George Brown Goode ...

, a small but diverse group restricted to Mexico. This species was first described in the journal ''

Copeia ''Ichthyology & Herpetology'' (formerly ''Copeia'') is a quarterly peer-reviewed scientific journal covering research in ichthyology and herpetology that was originally named after Edward Drinker Cope, a prominent American researcher in these fiel ...

'' by Dolores Kingston, from preserved and live specimens in the

University of Michigan , mottoeng = "Arts, Knowledge, Truth" , former_names = Catholepistemiad, or University of Michigania (1817–1821) , budget = $10.3 billion (2021) , endowment = $17 billion (2021)As o ...

Museum of Zoology. This species was named in honor of Frances H. Miller who, along with her husband

Robert Rush Miller Robert Rush Miller (April 23, 1916 – February 10, 2003) "was an important figure in American ichthyology and conservation from 1940 to the 1990s." He was born in Colorado Springs, earned his bachelor's degree at University of California, Berke ...

, helped to collect and ship the live specimens.

Description

The golden skiffia is a small fish, reaching a maximum

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 ...

(SL) of around , with a wedge shaped head and upturned lips. It has of a row 30–35 deeply cleft outer teeth in both the upper and lower jaws. Inner teeth can be cleft or conical, and are scattered irregularly. The species shows

sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...

with males having larger fins, and a greater body and head depth. Males also have a notched dorsal fin, which females lack. Males are a bright gold color with a gray overcast. The gold coloration is most vibrant during courtship, largely fading to the dorsal, caudal, and anal fins in non-courting males. Females have a greater body width, and both females and juveniles are gray-green, with scattered black flecks on their backs and along the

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

. Females do not change color during courtship. Both sexes have a black crescent just before the tail fin.

Life cycle

Golden skiffia is

ovoviviparous Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop insi ...

, giving birth to live young rather than laying eggs. The right and left

ovaries The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. T ...

are merged into a single organ, in which the young are gestated. This organ is capable of enlarging as the young develop. While in the ovary, the young possess trophotaenia. Each trophotaenia has three lobes containing blood vessels, which are believed to function in nutrient and gas exchange. Newborn young lose their trophotaenia shortly after birth. The gestation period is 55–60 days, with a usual brood size of 10–15 young.

Ecology

Range and habitat

Golden skiffia has been declared extinct in the wild since 1996. Prior to

extirpation Local extinction, also known as extirpation, refers to a species (or other taxon) of plant or animal that ceases to exist in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinct ...

, it was found in the Rio Teuchitlán, a tributary of the Río Ameca in

Jalisco Jalisco (, , ; Nahuatl: Xalixco), officially the Free and Sovereign State of Jalisco ( es, Estado Libre y Soberano de Jalisco ; Nahuatl: Tlahtohcayotl Xalixco), is one of the 31 states which, along with Mexico City, comprise the 32 Federal En ...

state, Mexico. The area of the river inhabited by golden skiffia had a slight current, with murky water and mud, sand, and silt substrate. Golden skiffia occurred at a maximum depth of . At the time specimens were collected, shore vegetation was dominated by ''

Acacia ''Acacia'', commonly known as the wattles or acacias, is a large genus of shrubs and trees in the subfamily Mimosoideae of the pea family Fabaceae. Initially, it comprised a group of plant species native to Africa and Australasia. The genus na ...

'' and ''

Salix Willows, also called sallows and osiers, from the genus ''Salix'', comprise around 400 speciesMabberley, D.J. 1997. The Plant Book, Cambridge University Press #2: Cambridge. of typically deciduous trees and shrubs, found primarily on moist so ...

'', while aquatic vegetation included ''

Pistia ''Pistia'' is a genus of aquatic plants in the arum family, Araceae. It is the sole genus in the tribe ''Pistieae'' which reflects its systematic isolation within the family. The single species it comprises, ''Pistia stratiotes'', is often called ...

'', ''

Ceratophyllum ''Ceratophyllum'' is a cosmopolitan genus of flowering plants including four accepted living species in 2016, commonly found in ponds, marshes, and quiet streams in tropical and in temperate regions. It is the only extant genus in the family Cer ...

'', ''

Potamogeton ''Potamogeton'' is a genus of aquatic, mostly freshwater, plants of the family Potamogetonaceae. Most are known by the common name pondweed, although many unrelated plants may be called pondweed, such as Canadian pondweed (''Elodea canadensis'' ...

'', and

water hyacinth ''Pontederia crassipes'' (formerly ''Eichhornia crassipes''), commonly known as common water hyacinth is an aquatic plant native to South America, naturalized throughout the world, and often invasive outside its native range.Xiphophorus maculatus ''Xiphophorus'' is a genus of euryhaline and freshwater fishes in the family Poeciliidae of order (biology), order Cyprinodontiformes, native to Mexico and northern Central America. The many ''Xiphophorus'' species are all known as platyfish (o ...

'' was found. This introduced species was found to outnumber Golden skiffia by a factor of 50. Golden skiffia's numbers were dramatically reduced within a year, likely due to competition from ''X. maculatus''. Golden skiffia is likely a

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

feeder, as indicated by gut contents dominated by pennate diatoms.

Reintroduction

On 4 November 2022, a team of conservationists from

Universidad Michoacana de San Nicolás de Hidalgo Michoacan University of Saint Nicholas of Hidalgo (UMSNH) is a public university in Morelia, Michoacán, Mexico, and the oldest institution of higher education in the Americas. The University grants law, economics, computer science, medicine, ar ...

Chester Zoo Chester Zoo is a zoo at Upton-by-Chester, Cheshire, England. Chester Zoo was opened in 1931 by George Mottershead and his family. It is one of the UK's largest zoos at . The zoo has a total land holding of approximately . Chester Zoo is operate ...

, and other conservation groups released approximately 1,200 golden skiffia, raised in a conservation breeding program into their native range in the Teuchitlán River. The project involved restoring the degraded habitat by removing non-native species and other threats from the river's ecosystem. The release is part of the conservation project Fish Ark Mexico that successfully reintroduced the

tequila splitfin ''Zoogoneticus tequila'', Tequila splitfin or simply Tequila fish, is a species of goodeid fish (family Goodeidae) from Mexico. The specific epithet, ''tequila'', derives from the Tequila Volcano, which looms near the type locality. Distributio ...

into the Teuchitlán. To prepare the individual fish for their return, fish marked for release were first placed in ponds to adapt to semi-captive conditions. From there they were dewormed and marked, before being taken to mesocosms in the river itself to experience and adapt to natural conditions prior to release. The released fish will be monitored for five years to assess population change, reproduction, and successful growth in their natural habitat.

References

{{Taxonbar, from=Q5559787 Goodeinae Freshwater fish of Mexico Endemic fish of Mexico Viviparous fish Fish described in 1978