Allotoca is a genus of viviparous livebearers in the family Goodeidae, endemic to the volcanic highlands of central Mexico. Every species recorded in the atlas comes from Mexico, mostly the crater lakes and spring-fed streams of the Lerma-Santiago basin and nearby drainages, including Lake Patzcuaro and Lake Zirahuen. Like other goodeids, Allotoca females nourish developing embryos through a placenta-like structure rather than relying on a yolk sac alone, giving birth to a small number of well-developed young. The atlas covers 8 species, generally modest fish in the 2–4.5 in range.
This is one of the most conservation-critical genera in the atlas: every one of its eight species carries a CARES priority designation, and the IUCN tallies reflect why, with six species rated Critically Endangered, one Endangered, and one Extinct in the Wild. Habitat loss, water extraction, and introduced species such as tilapia and mosquitofish have devastated the shallow crater lakes and spring systems these fish depend on, a familiar story across Mexico's goodeid-rich highlands. Within the hobby, Allotoca is very much a specialist's genus, with species like the royal splitfin (Allotoca regalis) maintained partly because captive populations now matter to the genus's survival, not only for display.
Breeding these fish is relatively well documented among Goodeid Working Group hobbyists: broods tend to be small, single-digit numbers of large, free-swimming young that need no special fry food to start, an advantage over many other livebearers. Water for Allotoca is generally kept cool to moderate rather than tropical, echoing the mid-elevation Mexican plateau climate the genus comes from. With so many wild populations gone or vanishing, maintaining genetic diversity across hobbyist bloodlines has become as important as any display consideration for this genus.