The Sulphur molly locally known as molly del teapa, is a species of fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

 in the Poeciliidae

Poeciliidae

Poeciliidae is a family of fresh-water fish which are live-bearing aquarium fish . They belong to the order Cyprinodontiformes, tooth-carps, and include well-known aquarium fish such as the guppy, molly, platy, and swordtail...

 family. It is endemic to Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

, specifically to the Baños del Azufre near Teapa, Tabasco. The Baños del Azufre are sulfidic springs that contain high concentrations of toxic hydrogen sulfide (H₂S). Poecilia sulphuraria has apparently evolved the ability to tolerate the toxic conditions. It is critically endangered for now.

Source

• Contreras-Balderas, S. & Almada-Villela, P. 1996. Poecilia sulphuraria. 2006 IUCN Red List of Threatened Species. Downloaded on 4 August 2007.
• Tobler, M., R. Riesch, F. J. Garcia de Léon, I. Schlupp & M. Plath (2008): Two endemic and endangered fishes, Poecilia sulphuraria (Alvarez, 1948) and Gambusia eurystoma Miller, 1975 (Poeciliidae, Teleostei), as only survivors in a small sulphidic habitat. Journal of Fish Biology 72 (3): 523-533. http://www.blackwell-synergy.com/doi/abs/10.1111/j.1095-8649.2007.01716.x