Boxer pupfish
The boxer pupfish is a small species of pupfish in the family Cyprinodontidae. It is endemic to Lake Chichancanab in Quintana Roo, Mexico.
In almost all places, different Cyprinodon species do not overlap in their range, but there are two notable exceptions. One of these is Lake Chichancanab, which is inhabited by C. simus, C. beltrani, C. esconditus, C. labiosus, C. maya, C. suavium and C. verecundus. Living together, the Cyprinodon species in Lake Chichancanab have diverged into different niches. Pupfish typically feed on algae and detritus. In Lake Chichancanab, however, C. simus has become a zooplankton-feeder. It once occurred in large schools, but has declined drastically due primarily to introduced species. Among the endemic Cyprinodon species in Lake Chichancanab, only C. beltrani and C. labiosus still occur in some numbers in their habitat, while the remaining are virtually—if not fully—extinct in the wild. However, a specimen of C. simus was recorded in the wild in 2009.