A new species of Betta from Aceh, northern Sumatra, Indonesia is decribed by Dr. Heok Hui Tan in the latest volume of ‘The Raffles Bulletin of Zoology’.
B. dennisyongi is included in the previously monotypic B. rubra species group and superficially appears very similar to B. rubra.
It can be told apart by a combination of characters including: presence of a black, continuous postorbital stripe extending to the edge of the opercle (vs. an interrupted postorbital stripe in B. rubra); a relatievly broad, black, triangular-shaped suborbital marking measuring 4-5 scales in width (vs. 2-3 scales in width); less intense body colouration with relatively wide interspaces between the black body bars (vs. more intense body colouration with relatively small interspaces between the black body bars); fewer anal-ﬁn rays (mode 25, vs. 27); a greater number of subdorsal scales (6–7, vs. 5–5 ½); a greater number of lateral scales (mode 31, vs. 30); a greater number of vertebrae (mode 30, vs. 29); longer dorsal-ﬁn base (13.0–18.4, vs. 11.0–13.4% SL); smaller maximum size (largest-known specimen 35.4 vs. 42.1 mm SL).
The new species is named for naturalist Dennis Yong Ghong Chong.
B. rubra and B. dennisyongi are native to coastal basins of northwestern Sumatra and a 2008 batch of specimens from the trade examined by Dr. Tan contained both species.
The author says that it’s unclear if this means the two occur together naturally in some locations, which might have been altered by humans, or that they’re routinely mixed by either collectors or middlemen.
What is clear is that both have been traded, and based on images both in our own species profile and elsewhere, mixed in the hobby.
For further information please refer to the full, open access paper: Tan, H. H. 2012. The identity of Betta rubra (Teleostei: Osphronemidae) revisited, with description of a new species from Sumatra, Indonesia. The Raffles Bulletin of Zoology 2013 61(1): 323-330