厚头鮰

Overview

Cyprinodon pachycephalus is confined to a thermal-spring system in northern Mexico. Strong temperature differences within that system are central to understanding its habitat: the temperature at the spring source is not an aquarium heating target. Natural hybridization downstream also makes provenance important.

Distribution & habitat

It is known from the San Diego de Alcalá spring and its distributaries in Chihuahua. The spring forms a shallow, narrow, unshaded channel. It may originally have drained toward the nearby Chuviscar River, but diversion into a canal eventually led to a terminal artificial impoundment.

Water is very hot at the source, cooling along the channel toward a substantially cooler terminal pool. Pool temperature may fluctuate with the weather. These contrasting conditions within one system should not be reduced to a single aquarium heating target.

The species occurs throughout the system and hybridizes with a relative in its lower reaches. Whether they originally coexisted or channel modification allowed the relative to enter remains unresolved.

Aquarium setup

A footprint around 60 × 30 cm is only marginally suitable for a pair. A group deserves a larger aquarium or container. Dense cover from plants or spawning mops should interrupt direct sightlines; elaborate decoration is unnecessary.

If filtration is used, an air-driven sponge unit reduces the risk of drawing in eggs or fry. Lighting is not critical, and filamentous algal growth can be encouraged. Providing egg-safe equipment should not be confused with having a confirmed species-specific breeding procedure.

Notes

The species name refers to its pronounced head shape. With such a restricted range and documented downstream hybridization, collection history is useful alongside appearance. Artificial alterations to the channel should not simply be interpreted as a natural expansion of range.