Gymnochanda filamentosa

Gymnochanda: from the Greek γυμνός, meaning 'naked', in reference to its scale-less body, and the generic name Chanda.

filamentosa: from the Latin filamentoso, meaning 'filamentous', in reference to the highly-extended dorsal and anal fin rays in males.

Appears restricted in range with confirmed records existing only from Johor state, southern Peninsular Malaysia, and the Kapuas river system in West Kalimantan (Kalimantan Barat) province, Indonesia (Borneo).

Type locality is unclear, with first 'southern Malaya', then 'Singapore' mentioned in the original description with Fraser-Brunner stating that 'even the precise location from which they were obtained is not known'.

Tends to occur in low altitude, swampy freshwater habitats containing still or slowly-moving, acidic water with substrates of silt and peat.

Does not require a large aquarium but given its delicate nature and rarity minimum base dimensions of 60 ∗ 30 cm24 ∗ 12 in are suggested since smaller tanks are more susceptible to swings in water chemistry.

A densely-planted tank with floating vegetation and roots, twigs or branches and natural leaf litter would seem appropriate.

There's no need to use natural peat, the collection of which is both unsustainable and environmentally-destructive.

Filtration should not be strong with an air-powered sponge-type unit ideal, and given it naturally inhabits pristine environments it should never be introduced to a new aquarium.

Small live foods such as Artemia, Daphnia, etc., should be considered essential, especially during the acclimatisation period, although frozen and dried alternatives may be accepted over time.

Unlikely to make an ideal community fish and best kept in a species-specific set-up, or perhaps alongside comparably-sized, equally peaceful species such as Boraras, Sundadanio or Indostomus spp.

Gymnochanda species are gregarious by nature and ideally a group of 8-10 specimens should be the smallest purchased.

The dorsal and anal fin spines in adult males are extended into filaments which females lack.

Unrecorded.

G. filamentosa has appeared in the ornamental trade but is evidently delicate and therefore recommended only to experienced aquarists.

It can be told apart from congeners by the following combination of characters: possession of filamentous dorsal and anal-fin rays in males; body transparent to translucent yellowish-brown colour in life; absence of a highly-extended second anal-fin spine; absence of carmine-red pigmentation in the dorsal, anal and caudal fins.

The full diagnosis of the genus was modified slightly by Tan and Lim (2011)[2] in order to accommodate G. verae, as follows: small ambassids with adult size not exceeding 32 mm SL. Body scale-less, translucent in life with complete but indistinct lateral groove. Mature individuals sexually dimorphic (note that this is not known in the case of Gymnochanda limi), mature males with one of the following modified fin characters: 1) anterior 1st to 4th soft rays of the anal and second dorsal fins produced into long filaments; 2) fin rays elongated but joined by interradial membranes; or 3) elongated second anal-fin spine. Females colourless with or without slight fin extensions. Preorbital with 2 to 4 large projecting serrae. Preoperculum strongly denticulate on the lower margin. Gill rakers long and slender, 12 to 16 on the lower branch of the first branchial arch

There are currently four described species but they are under-represented in museum collections and may have been overlooked in the past.