Redtail splitfin

Taxobox
name = "Xenotoca"
status =


image_width =
image_caption =
regnum = Animalia
phylum = Chordata
classis = Actinopterygii
ordo = Cyprinodontiformes
familia = Goodeidae
genus = "Xenotoca"
genus_authority = Hubbs and Turner, 1939
species = "X. eiseni"
binomial = "Xenotoca eiseni"
binomial_authority = Rutter, 1896

The Redtail Splitfin, or Redtail Goodeid, ("Xenotoca eiseni") is a species of goodeid fish from the family Goodeidae and subfamily Goodeinae. Like other members of Goodeinae, the Redtail Splitfin is a livebearer. However, the goodeid mating system differs in several ways from the more common livebearing fish from the family Poeciliidae that includes guppies and swordtails. While no goodeid species is a very popular aquarium fish, the Redtail Splitfin is one of most popular.

Range and habitat

The Redtail Splitfin comes from several rivers in the highlands of Mexico, including the Rio San Leonel and Rio Grande de Santiago in Nayarit and the Rio Tamazula in Jalisco.cite book|title=Baensch Aquarium Atlas Volume 2|author=Baensch, H.|page=pp. 712-713|year=1993|isbn=1-56465-114-2] cite book|title=Livebearing Fishes|author=Dawes, J.|page=pp. 219-221|year=1995|isbn=0-7137-2592-3] They live in clear mountain streams as well as roadside ditches.

Description

The Redtail Splitfin is a deep-bodied fish, and males have a hump behind the head.cite book|title=Complete Encyclopedia of the Freshwater Aquarium|author=Dawes, J.|page=p. 286|year=2001|isbn=1-55297-544-4] The hump gets larger as the males get older. Males' body color is blue, and the caudal fin (tail) and penduncular area are red or orange. There are a number of color variations, and fish from Nayarit have a bluer body, while fish from San Marco, Jalisco are blotched. Females are more plainly colored Females are generally slightly larger than males. Females grow to 7 centimeters (2.8 inches) while males grow to 6 centimeters (2.4 inches).cite web|title=Fish Base Xenotaca eiseni|url=http://www.fishbase.org/Summary/SpeciesSummary.php?id=11953|accessdate=2008-08-10]

Breeding

Male goodeids like the Redtail Splitfin have a notched anal fin that gives the fish the name "splitfin", instead of the gonopodium of poeciliids.cite book|title=Livebearing Fishes|author=Dawes, J.|page=pp. 42-44|year=1995|isbn=0-7137-2592-3] This notched anal fin, or andropodium, is used to transmit sperm to the female. The female nourishes the unborn young via trophotaeniae, which function like an umbilical cord in mammals. [cite web|title=Zipcode Zoo Xenotoca eiseni|url=http://zipcodezoo.com/Animals/X/Xenotoca_eiseni/|accessdate=2008-08-16]

Females give birth about every 2 months to 10 to 50 fry. The newborn Redtail Splitfin fry are relatively large compared to most newborn livebearer fry, at about 15 millimeters (2/3 of an inch) long.

In the wild, both male and female Redtail Splitfins prefer to mate with fish of similar size. This limits the sexual advantage to males that grow especially large. This minimizes the sexual dimorphism in the size of the fish between males and females.cite web|title=Sexual selection constrained by internal fertilization in the livebearing fish Xenotoca eiseni|url=http://cat.inist.fr/?aModele=afficheN&cpsidt=2083191|accessdate=2008-08-10]

Aquarium keeping

The Redtail Splitfin is not a very common aquarium fish, but it is one of the most common goodeids to be kept in the aquarium. They are not very demanding in the aquarium, although they prefer hard, alkaline water. They can tolerate a wide range of water temperatures, from 15 to 30 degrees Celsius (59 to 86 degrees Farenheit). They accept a wide range of foods, but do require some vegetable matter in their diets. Although they are generally peaceful, they are known to occasionally nip the fins of fellow acquarium residents. This behavior can be reduced by keeping the Redtail Splitfin in schools.

References