Matt Clarke on a newly imported form of Mastacembelus armatus on sale as Mastacembelus dayi.
Scientific name: Mastacembelus cf. armatus (Lacepede, 1800)
Origin: M. armatus is currently believed to be a single widespread species which differs markedly in pattern across the range. It has been recorded from across Asia, including: Vietnam, Laos, Thailand, Thailand, Sri Lanka, Singapore, Pakistan, Nepal, Myanmar, Malaysia, Indonesia, India, China, Cambodia, Bangladesh and Afghanistan. The variety pictured is said to have been imported from the Kapur River in Malaysia. Collectors state that the form appears to be the same one that occurs in southern Thailand.
Size: Museum records state an adult size of up to 1m/39" for adult armatus, but fish over 60cm/24" are uncommon in captivity.
Diet: Small specimens accept frozen bloodworms and other meaty foods, while larger fish appreciate earthworms and, sometimes, sinking tablet foods.
Water: Freshwater. pH 6-7.5, 25°C. Adaptable to harder water.
Aquarium: These eels can be kept with most larger fishes, and there own kind in a large aquarium. Spiny eels frequently try to escape from the aquarium so be very careful to ensure that there are no gaps at the top that an eel could slither through. A smooth gravel substrate or soft, sandy substrate is preferred as Mastacembelus like to burrow. PVC or ABS pipes can be added to provide additional shelter.
Notes: This species was imported as Mastacembelus dayi, however, I am reliably informed by Thailand-based exporter Kamphol Udomritthiruj that this is, in fact, one of many forms of the Tyretrack eel, M. armatus. M. dayi is similar in appearance to M. alboguttatus (which has recently been imported by BAS in Bolton) and both have pale spots, rather than the dark ones seen in these fish. Numerous forms of "armatus" exist and many are intermediate types that are harder to place as a specific variety. Clearly, given the massive variation in patterns seen in M. armatus, this genus is crying out for closer taxonomic investigation. It seems likely that many of these will be split into new species at a later date.
Identification: Meristics are largely useful on aquarium eels as you'd never be able to count fin rays on a live fish. However, the true M. armatus should have 33-40 dorsal spines and 67-82 soft rays, 67-83 soft anal fin rays and 87-98 vertebrae.
Availability: It's the first time I've seen this form on sale. These were imported from Thailand by Tom Halvorsen Ltd (0797 709 8127) and were on sale at Wharf Aquatics in Nottinghamshire (01773 861255). The fish listed as M. sp. "Leo", or by the common name of Leopard spiny eel, by some other exporters could be the same species.
Price: Expect to pay around **.** for one of these.