Subspecies
Rhodeus ocellatus kurumeus which is used to be called R. o. smithi (Nippon baratanago) is a Japanese native species but Rhodeus ocellatus ocellatus (Tairiku baratanago) is found in China, Taiwan, as well as in Japan. Nippon baratanago was widely spread in the west side of Japan (Kyushu and western part of Honshū) before World War II. In 1942 Tairiku baratanago was accidentally introduced with grass (Ctenopharyngodon idellus) and silver carp (Hypophthalmichthys molitrix) from mainland China to Japan.
These two subspecies are morphologically very similar but there are several distinguishing characters such as the number of longitudinal scales, principal rays in the dorsal and anal fins, and shape of eggs. Also, R. o. ocellatus (Tairiku baratanago) has a silvery-white area anteriorly (white lines) on the ventral fin but R. o. kurumeus (Nippon baratanago) does not. In comparison the ventral fin of R. o. kurumeus (Nippon baratanago) is a dark color. Another notable difference is body size. R. o. kurumeus (Nippon baratanago) do not commonly exceed 60mm in length, whereas males of R. O. ocellatus are larger than 80mm and females of this subspecies commonly exceed 60mm (Tairiku baratanago).
Read more about this topic: Rosy Bitterling