Abstract
Background:
Koi fish (Cyprinus rubrofuscus), celebrated for their vibrant colors and cultural significance, are also valued in the ornamental fish industry. Despite extensive research on fish sensory biology, specific studies on taste buds in koi, especially among different ornamental varieties, are limited.

Aim:
This study aimed to analyze the anatomical structure and distribution of taste buds in the palatal organs of six popular koi varieties in Indonesia: Kohaku, Shiro, Showa, Sanke, Platinum, and Ogon.

Methods:
Eighteen koi fish, three from each variety and aged 4-6 months, were examined using histological techniques and scanning electron microscopy.

Results:
While no macroscopic or histological differences in the palatal organs were observed across varieties, significant variation in taste bud density was noted. The Ogon variety exhibited the highest average taste bud density (23.95 ± 7.03), whereas the Shiro variety showed the lowest (17.03 ± 5.26).

Conclusion:
Statistical analysis revealed that taste bud density significantly differed among varieties, with the Ogon variety having notably higher density compared to shiro and sanke. These findings suggest that selective breeding for ornamental traits may impact sensory functions.

Key words: Cyprinus rubrofuscus, Taste buds, Palatal organ, Koi fish, Aquaculture