Sexual Dimorphism in Fin Size and Shape in Bluefin Killifish

Area of Science:

• Evolutionary biology
• Ichthyology
• Sexual selection

Background:

• Sexual dimorphism offers insights into differing trait optima between sexes.
• Quantifying sexual dimorphism across all fin types in fish is less explored.
• Fins are often overlooked in morphological studies due to preservation and size challenges.

Purpose of the Study:

• To quantify sexual dimorphism in fin size and shape across all fin types in the bluefin killifish (Lucania goodei).
• To identify which fin traits are most affected by sexual selection.

Main Methods:

• Morphometric analysis of pectoral, pelvic, dorsal, anal, and caudal fins.
• Measurement of fin size (area, ray length, base length) and shape.
• Comparative analysis between male and female bluefin killifish.

Main Results:

• Striking sexual dimorphism was observed in dorsal and anal fins (area, ray length, base length).
• Males showed posterior elongation in dorsal and anal fins compared to females.
• Pelvic, pectoral, and caudal fins displayed moderate sexual dimorphism.
• Dorsal and anal fin traits were strongly correlated within sexes, suggesting shared developmental pathways or selection.

Conclusions:

• Dorsal and anal fins are primary targets of sexual selection in male bluefin killifish.
• These dimorphic fin traits likely play roles in male courtship, competition, or fertilization.
• The findings contribute to understanding the evolution of sexual dimorphism in fish morphology.