The first European cave fish.

Area of Science:

• Subterranean biology
• Ichthyology
• Evolutionary biology

Background:

• Europe boasts rich subterranean biodiversity, yet lacks documented cave fish species.
• Cave fish are common subterranean vertebrates, but their presence in Europe remained unconfirmed.
• This study addresses the gap by reporting the first European cave fish discovery.

Discussion:

• The discovered loach population in Germany exhibits typical cave adaptations: reduced eyes and pale coloration.
• This finding represents the northernmost cave fish population globally.
• Geological history suggests post-glacial colonization of the Danube-Aach karst system.

Key Insights:

• Genetic analyses (COI gene) indicate a recent origin, with shared haplotypes with surface stone loaches.
• Microsatellite data reveal genetic isolation from surface populations and reduced genetic variability in the cave fish.
• These European cave loaches are on a unique evolutionary path, distinct from surface populations.

Outlook:

• Further research can explore the specific evolutionary pressures driving adaptation in this unique environment.
• Investigating other European karst systems may reveal additional cryptic subterranean fish populations.
• This discovery opens new avenues for understanding vertebrate adaptation to aphotic environments.