Wednesday, December 11, 2013

[Ichthyology • 2013] A Review of the danionine Genera Rasboroides and Horadandia (Pisces: Cyprinidae), with Description of A New Species from Sri Lanka

The taxonomy of Rasboroides and Horadandia, two genera of small danionine cyprinids that occur in southern India and Sri Lanka, is reviewed. Rasboroides comprises four species, distinguished as follows: R. vaterifloris and R. nigromarginatus differ from their congeners by a lesser body depth (26.9-33.0 % SL); and from each other by a greater interorbital width in males (29-33 % HL vs. 17-22) and greater anal-fin depth in females (23.5-24.8 % SL vs. 17.4-22.7) of R. vaterifloris. Rasboroides pallidus differs from Rasboroides rohani, new species, by its smaller size (up to 24.6 mm vs. 35.5 mm SL), by possessing fewer scales in transverse line on body (1/2 6 1/2-1/2 7 1/2 vs. 1/2 8 1/2) and in lateral series (20-24 vs. 25-28). 
Rasboroides differs from Horadandia, its sister group, by the presence in males of a series of tubercles on the leading edge of the pectoral fin (absent in Horadandia) and by possessing 3 (vs. 2) rows of pharyngeal teeth, while the pharyngeal teeth of Horadandia are ornamented distally by a series of cusps, a character absent in Rasboroides. Horadandia brittani is recognized as a valid species, distinguished from H. atukorali by possessing a smaller eye (eye diameter 27-37 % HL, vs. 37-41) and having the dorsal-fin origin closer to the hypural notch (vs. midway between snout-tip and hypural notch). 
The genus Rasboroides is restricted to shaded rainforest streams in the south-western ‘wet zone’ (Kalu to Walawe Rivers) of Sri Lanka, whereas Horadandia occurs in the coastal floodplains of western Sri Lanka and southern India.

-:   Rasboroides Brittan, 1954   :-
Diagnosis. Rasboroides is distinguished from the two genera most closely related to it, viz. Trigonostigma and Horadandia (see Kottelat & Vidthayanon, 1993; Fang et al., 2009; Liao et al., 2010; Tang et al., 2010)

The gender of Rasboroides is masculine (see ICZN (1999), art. The genus is restricted to rainforest streams in south-western Sri Lanka, from the Kalu to the Walwe River basins.

• Rasboroides vaterifloris (Deraniyagala, 1930)
• Rasboroides nigromarginatus (Meinken, 1957)
• Rasboroides pallidus Deraniyagala, 1958
• Rasboroides rohani, new species, Batuwita, Silva & Edirisinghe, 2013
Etymology. The species is named in honour of Rohan Pethiyagoda, Founder of the Wildlife Heritage Trust of Sri Lanka (WHT), for his special commitment to the ichthyofauna of Sri Lanka and India; and for continuing support of biodiversity research and conservation in Sri Lanka.

-:   Horadandia Deraniyagala, 1943   :-

 Horadandia has a wide distribution in the coastal floodplains of southern India, and southern and western Sri Lanka.

• Horadandia atukorali Deraniyagala, 1943
• Horadandia brittani Rema Devi & Menon, 1992

Batuwita, S., Silva, M.d. & Edirisinghe, U. 2013. A Review of the danionine Genera Rasboroides and Horadandia (Pisces: Cyprinidae), with Description of A New Species from Sri Lanka. Ichthyological Exploration of Freshwaters. 24 (2): 121-140.