Xiphophorus pygmaeus

Source: Wikipedia, the free encyclopedia.

Pygmy swordtail
Yellow morph male pygmy swordtail

Data Deficient  (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cyprinodontiformes
Family: Poeciliidae
Genus: Xiphophorus
Species:
X. pygmaeus
Binomial name
Xiphophorus pygmaeus
(Hubbs & Gordon, 1943)

Xiphophorus pygmaeus, the pygmy swordtail, is a

swordtails
. The male's sword is barely visible and the species is often called the swordless swordtail. It is sometimes kept in home aquaria, but is a rather delicate species.

Taxonomy and evolution

Xiphophorus pygmaeus is the smallest member of the genus

courtship behavior, body depth, and well-developed swords. Large size eventually reappeared in X. pygmaeus but the normally accompanying traits did not.[4]

Description

Females grow to 4.5 cm (1.8 in), while males attain 3.5 cm (1.4 in). The male's sword is only 1-2 mm long.[5] The species was originally thought to consist only of small-sized males (all less than 29 mm long and most less than 24 mm), but in 1994 it was discovered that two populations contain large males.[4]

The base color of the fish is gray-brown.

sex-linked: male descendants of yellow males tend to be yellow too.[2] Males are generally more intensely colored than females.[6]

Distribution and habitat

Xiphophorus pygmaeus was discovered in

X. variatus are found in the same section of the river, but their preference for shallower and slower water isolated X. pygmaeus from them.[7]

Xiphophorus pygmaeus also inhabits Rio Axtla's tributaries Rio Tancuilin and Rio Huichihuayan.[3] Its preferred habitat is characterized by soft bottoms and large stands of submerged plants[3] such as Sagittaria.[8]

Reproduction

Male (up) and female (below)

Xiphophorus pygmaeus is unusual among swordtails in that females are not courted by males,

copulation.[9] In most Xiphophorus species, including the most closely related, X. nigrensis and X. multilineatus, large males court females, while small males rely on the "sneak-chase" strategy. X. pygmaeus females prefer to be courted, however, and thus choose males of X. nigrensis over males of their own species when they can.[9]

Xiphophorus pygmaeus breeds sparsely, with a female rarely

giving birth to more than 10 fry at once. The fry are 6–7 mm (0.24–0.28 in) long at birth and usually not preyed upon by the adults.[2][5]

In aquarium

Caring for X. pygmaeus in the home aquarium is challenging. The species requires excellent filtration and frequent water changes and does not do well in soft water or temperatures exceeding 24°C. The addition of fine-leaved aquatic plants such as Ceratophyllum demersum is recommended because the fish feed on such plants and algae as well as infusoria growing among them.[2]

References

  1. doi:10.2305/IUCN.UK.2019-2.RLTS.T191791A2003283.en
    . Retrieved 24 April 2023.
  2. ^ a b c d Lothar Wischnath (1989). "Livebearers". Tropical Fish Hobbyist. Vol. 38, no. 1–4. p. 17-18.
  3. ^ a b c "Livebearers". Tropical Fish Hobbyist. Vol. 54, no. 5–8. 2006. p. 108.
  4. ^
    doi:10.1111/j.1095-8312.1995.tb01044.x
    .
  5. ^
    ISBN 0866220909
    .
  6. ISBN 9780132227209
    .
  7. JSTOR 1439920
    . Retrieved 14 April 2023.
  8. ^ Donn Eric Rosen (1960). "Middle-American Poeciliid Fishes of the Genus Xiphophorus". Bulletin of the Florida State Museum: Biological Sciences. 5 (4). University of Florida: 159.
  9. ^
    S2CID 20181010
    .
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