Do Chinese cavefish show intraspecific variability in morphological traits?

Area of Science:

• Evolutionary Biology
• Ichthyology
• Speleobiology

Background:

• Cavefishes are unique vertebrates adapted to subterranean environments.
• The genus *Sinocyclocheilus* (Cyprinidae) is highly endemic to China, representing a significant portion of global cavefish diversity.
• Understanding intraspecific variation in cavefish is crucial for evolutionary studies.

Purpose of the Study:

• To investigate morphological variability within and among populations of three *Sinocyclocheilus* cavefish species.
• To determine if distinct subterranean habitats (shallow vs. deep) correlate with specific morphological traits in *Sinocyclocheilus*.
• To explore adaptive divergence in Chinese cavefish populations.

Main Methods:

• Morphometric analysis of three *Sinocyclocheilus* species from different cave habitats.
• Comparison of traits such as eye size and body shape (humpback) between populations.
• Statistical assessment of morphological differences related to habitat conditions.

Main Results:

• Populations near cave entrances (light, high food availability) displayed larger eyes and reduced humpback.
• Specimens from deeper, darker cave areas (food scarcity) exhibited smaller eyes and increased humpback.
• Significant morphological divergence was observed between conspecific populations based on habitat.

Conclusions:

• Habitat-specific ecological pressures drive distinct morphological adaptations in *Sinocyclocheilus* cavefish.
• Eye size and body shape are key traits reflecting adaptation to light and food availability in subterranean environments.
• Chinese cavefish offer valuable insights into evolutionary processes and adaptation in extreme environments.