Poecilia gillii

Gill's molly
	A male
	A female
Conservation status
	; Data Deficient (IUCN 3.1)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Cyprinodontiformes
Family:	Poeciliidae
Genus:	Poecilia
Species:	P. gillii
Binomial name
	Poecilia gillii; Kner, 1863

Last updated September 12, 2023

Poecilia gillii, Gill's molly, is a herbivorous livebearer fish distributed throughout Central America. It is found in both moving and still water as well as in both freshwater and brackish habitats. Populations of this species differ in color, size, and morphology.

Description

Poecilia gillii is primarily greyish with blue highlights and rows of yellow spots on the sides. Females from some estuarine habitats are dotted black instead. Most of the fins are yellowish.^[2] Adult males differ widely in body size, color, and morphology.^[3] Some males develop a long dorsal fin, which, along with the caudal fin, usually has spots or black blotches close to the fish's body. The caudal fin of the males from some tideland populations is edged orange. Some other populations contain males with the dorsal and caudal fins colored red.^[2]

The dorsal fin of P. gillii males is among the largest of the non-courting males in the Poecilia sphenops (shortfin molly) species complex.^[3] The species is most similar to P. mexicana .^[2]

A red fin form male
A yellow fin form male
A female

Distribution and habitat

Poecilia gillii is widespread in Central America, occurring from Guatemala to Colombia on its Atlantic slope and up to Costa Rica's Térraba River on the Pacific slope. In Costa Rica, it is the most common freshwater fish species.^[3]^[2] The molly's range continues in Panama from the Grande River to the Bayano River.^[2]

The species is found in greatest numbers in estuaries, swamps, brooks, and shallow waters of large rivers, but also inhabits faster flowing waters. The individuals living in brackish water tend to be larger than those observed in brooks, reaching up to 105 mm. The temperatures of these habitats range from 19 to 37 °C.^[2]

In the Pacuare River, a large population was found living over a substrate of algae-covered boulders, pebbles, and sand. Species sharing this habitat include Amatitlania nigrofasciata , Astyanax aeneus , Parachromis dovii , Poeciliopsis retropinna , Sicydium salvini , and Tomocichla sieboldii .^[3]

Diet

Poecilia gillii is a detrivorous and herbivorous species. The fish are generally found near the substrate, browsing on detritus, ooze, and filamentous algae.^[2]

Reproduction

Poecilia gillii is a livebearer, meaning that females give birth to live fry.^[3] It reproduces continuously year-round, with most juveniles appearing in August.^[2]

In some poeciliid species, e.g. P. latipinna and Xiphophorus multilineatus , large males court females while small males instead rely on chasing and sneaking up on the females to copulate. While P. gillii males also come in different sizes, neither large nor small males demonstrate courtship. It is hypothesized, therefore, that the purpose of the exaggerated color and fin size of the large males is to intimidate rival males and avoid fighting. The small males are of less conspicuous size and color in order to facilitate sneaking up on females and to avoid aggressive large males. Males, large ones more often than small ones, nibble on the females's sex opening to ascertain the female's receptiveness. Females might prefer large, colorful males. The copulatory organ, called gonopodium, is longer in the small males in order to facilitate the sneaking up and chasing type of copulation.^[3]

Related Research Articles

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Poecilia sphenops is a species of fish, of the genus Poecilia, known under the common name molly; to distinguish it from its congeners, it is sometimes called short-finned molly or common molly. They inhabit fresh water streams and coastal brackish and marine waters from Mexico to Colombia. The wild-type fishes are dull, silvery in color. The molly can produce fertile hybrids with many Poecilia species, most importantly the sailfin molly. The male mollies generally tend to be mildly aggressive.

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The eastern mosquitofish is a species of freshwater fish, closely related to the western mosquitofish, Gambusia affinis. It is a member of the family Poeciliidae of order Cyprinodontiformes. The eastern mosquitofish is native to the eastern and southern United States from Florida to Pennsylvania and inland to Alabama and Tennessee, while the western mosquitofish has a larger distribution throughout the United States.

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The Cauca molly is a freshwater fish in the family Poeciliidae. This fish is found in Panama, Venezuela, and Colombia, where it lives in shallow waters in the basins of the Lebrija, Magdalena, Cauca and other rivers. P. caucana eats mosquito larvae and algae.

Poecilia velifera, known as the Yucatan molly and also as the giant sailfin molly amongst aquarists, is a very large Livebearer that lives in coastal waters of the Yucatan peninsula. These live-bearer (Poeciliidae) fish are particularly well known for both the extreme size variation among males, and the sexual dimorphism between males and females in both body shape and behavior.

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Alfaro cultratus, the knife livebearer, is a species of tropical freshwater fish from the family Poeciliidae. It hails from Central America and is often kept in home aquaria.

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Poecilia chica, the dwarf molly, is a livebearer fish from the Mexican state of Jalisco. The fish are small and exceptionally colorful. The dominant male may become completely black, which is a unique ability in the Mollienesia subgenus.

Poecilia catemaconis, the bicolor molly, is a livebearer fish from Mexico.

References

↑ Lyons, T.J.; González, R.; Matamoros, W.A. (2020). "Poecilia gillii". The IUCN Red List of Threatened Species. 2020: e.T164691452A164691581. doi: 10.2305/IUCN.UK.2020-2.RLTS.T164691452A164691581.en . Retrieved 23 August 2023.
1 2 3 4 5 6 7 8 Bussing, William A. (1998). Freshwater fishes of Costa Rica. Editorial Universidad de Costa Rica. pp. 220–222. ISBN 9977674892.
1 2 3 4 5 6 Furness, Andrew I.; Hagmayer, Andres; Pollux, Bart J. A. (December 2020). "Size-dependent male mating tactics and their morphological correlates in Poecilia gillii". Biological Journal of the Linnean Society. 131 (4): 880–897. doi: 10.1093/biolinnean/blaa151 .

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[iucn_status-1] Lyons, T.J.; González, R.; Matamoros, W.A. (2020). "Poecilia gillii". The IUCN Red List of Threatened Species. 2020: e.T164691452A164691581. doi: 10.2305/IUCN.UK.2020-2.RLTS.T164691452A164691581.en . Retrieved 23 August 2023.

[Bussing-2] 1 2 3 4 5 6 7 8 Bussing, William A. (1998). Freshwater fishes of Costa Rica. Editorial Universidad de Costa Rica. pp. 220–222. ISBN 9977674892.

[Furness-3] 1 2 3 4 5 6 Furness, Andrew I.; Hagmayer, Andres; Pollux, Bart J. A. (December 2020). "Size-dependent male mating tactics and their morphological correlates in Poecilia gillii". Biological Journal of the Linnean Society. 131 (4): 880–897. doi: 10.1093/biolinnean/blaa151 .

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