Phototransduction Gene Expression and Evolution in Cave and Surface Crayfishes

Area of Science:

• Evolutionary biology
• Genomics
• Sensory biology

Background:

• Animals in caves often lose vision, but the genetic basis is unclear.
• Freshwater crayfish have repeatedly adapted to cave environments, offering a model for studying vision loss.
• Understanding genetic changes in vision-related genes is crucial for evolutionary studies.

Purpose of the Study:

• To investigate the genetic patterns and evolutionary processes underlying repeated vision loss in freshwater crayfish.
• To examine the expression and evolution of phototransduction genes in cave-dwelling versus surface-dwelling crayfish species.
• To determine if genetic components of vision remain intact despite eye reduction in cave crayfish.

Main Methods:

• Transcriptomic data analysis from the eyes of 14 crayfish species (cave and surface).
• Identification and quantification of expressed genes involved in visual phototransduction.
• Statistical analysis to detect positive selection and changes in selection strength on vision genes.
• Comparative analysis of gene expression evolution across different cave adaptation events.

Main Results:

• A complete set of phototransduction gene families is expressed in both cave and surface crayfish.
• Expression levels of these vision-related genes are consistently lower in cave-dwelling species.
• Evidence of episodic positive selection and varying selection strengths on gene families in cave species.
• Gene expression evolution suggests convergent, potentially adaptive, downregulation of vision genes.

Conclusions:

• Vision loss in caves involves both changes in gene sequence and expression levels.
• Convergent downregulation of phototransduction genes is a key evolutionary process in crayfish eye reduction.
• The genetic toolkit for vision is retained, but its usage is modified during adaptation to aphotic environments.