| Batasio | |
|---|---|
 | |
| Batasio fasciolatus | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Siluriformes |
| Family: | Bagridae |
| Genus: | Batasio Blyth, 1860 |
| Type species | |
| Pimelodus batasio F. Hamilton, 1822 | |
Batasio is a genus of catfish of the family Bagridae. These small fish are found in fast-flowing hillstreams throughout South and mainland Southeast Asia.
Batasio was first described by Edward Blyth in 1860 with Batasio buchanani (a needless renaming of Batasio batasio) designated as type. [1] B. pakistanicus, described in 1989, is tentatively placed in Batasio, but its generic placement is questionable. [2] [3]
There are currently 18 recognized species in this genus:
Batasio species are generally found throughout South and mainland Southeast Asia. [2] B. affinis is found in Myanmar. [10] B. fluviatilis is found in Northern Malay Peninsula. [11] B. tigrinus is also recorded from Thailand. [12] B. dayi originates from the Salween and Irrawaddy River drainages in Myanmar. [13] B. elongatus is found in southwestern Myanmar. [2] B. macronotus originates from eastern Nepal. [3] B. pakistanicus is found in the Indus River. [14] B. batasio also originates from northern India where it shares its habitat with Mystus vittatus . [15] B. fasciolatus is known from the Tista River drainage, a tributary of the Brahmaputra River. [5] B. merianiensis is found in the Brahmaputra River drainage. [5] B. sharavatiensis originates from the Sharavati River in Uttara Kannada, Karnataka. [9] B. spilurus is known from the Brahmaputra River drainage in the vicinity of Dibrugarh. [5] B. tengana is known from the Ganges and the Brahmaputra River drainages; it is apparently restricted to upper reaches of larger rivers. [5] B. travancoria is distributed in the Chittar, Kallada and Pamba Rivers in southern Kerala and is considered a rare species. [9]
Batasio species typically have enlarged sensory pores on their head, laterally compressed heads and bodies, and at least 35 vertebrae. [5] B. tengana, B. pakistanicus and B. spilurus differ from other Batasio species in that their adipose fin is much shorter. [5] These fish are small catfish. [2] B. pakistanicus and B. spilurus are the smallest species, reaching only 35 millimetres (1.4 in) SL and 45 mm (1.8 in) SL respectively. [5] The other species range from 55–101 mm (2.2–4.0 in) SL. [5]
B. affinis, B. dayi, and B. fluviatilis have bars or bands, spots or stripes, and are not plain-bodied. [9] B. pakistanicus has a black humeral spot with a dark streak on the dorsum. [9] B. batasio has a dark stripe along the lateral line and another above. [9] B. batasio does not exceed 10 centimetres (4 in). [15] B. fasciolatus and B. tigrinus are the only Batasio species in which the adult colouration consists of five or six vertical dark brown bars on a light brown body. [5] B. tengana has bands descending from the dorsal surface to the lateral line. [9] B. travancoria has a lateral stripe along the lateral line and a faint shoulder spot. [9] B. sharavatiensis is the only Batasio that has a completely plain and colourless body; its adipose fin is almost confluent (continuous) with the caudal fin save for a small notch. [9]
Batasio, like most other bagrids, are easy to sex. The male has a visible genital papilla just fore of the anal fin. [15] Gravid female B. tengana (South East Asian form) are easy to identify because the pink eggs can be seen through their semi-transparent belly when they swim near light. [15]
Batasio species generally are found in fast-flowing hillstreams. [2] B. fluviatilis is found in rivers and streams with moderate to swift current and a predominantly rocky bottom, and is less often in slow-flowing streams with a muddy substrate. [11] B. tengana occurs in rivers and canals and is found in torrential streams. [16] B. travancoria occurs in hillstreams and rivers at the bases of hills. [17] B. fluviatilis hide among stones or submerged vegetation during the day and come out at night to feed. [11] B. batasio appears to mimic Mystus vittatus , with which it inhabits the same habitat. [15]
B. tengana, though uncommon, is the most commonly encountered species of Batasio in the aquarium hobby. [15] B. tengana does well in captivity, and has been bred in captivity. The fish spawned in soft neutral water, but raising the fry, of which there were over 200, proved difficult. [15] The temperature for the Indian species should remain between 20–22 °C (68–72 °F); the Southeast Asian Batasio will tolerate slightly warmer waters. It appears that all Batasio need a lot of current and a high oxygen content. [15]
B. batasio is another species in the hobby, but can be easily confused with Mystus vittatus. [15] B. travancoria has only once been imported to the U.S. [15] In captivity, the experience of one aquarist is that specimens of B. travancoria show little interest in all foods offered and slowly lose weight over a span of a few months and perish. [15]