Oreichthys crenuchoides SCHÄFER, 2009

Drape Fin Barb

Classification

Order: Cypriniformes Family: Cyprinidae

Distribution

Possibly  endemic to tributaries of the Brahmaputra Rover in West Bengal state, eastern India. The type specimens came from the Jorai River, close to the border with Assam,  but it’s been collected elsewhere, including the Ghoti Ganga River, Cooch Behar district (A. Rao, pers. comm.).

It’s also known from the Buxa (often spelled ‘Buxar’) Tiger Reserve, a 760km² forested area in the sub-division of Alipurduar, Jalpaiguri district and home to some of India’s most recognised animals including tiger, elephant, leopard and regal python.

Habitat

At the type locality the Jorai River was around 5 m wide with a muddy substrate, contained quite clear water and was flowing slowly through ‘open land’, and this would seem typical since congeners also display a preference for slow-moving habitats.

Maximum Standard Length

35 – 45 mm.

Aquarium SizeTop ↑

An aquarium with base dimensions measuring at least 60 ∗ 30 cm is required.

Maintenance

Best kept in a well-decorated set-up with aquatic vegetation and woody structures. The addition of some floating plants to diffuse the light entering the aquarium also seems to be appreciated and the addition of dried leaf litter can add a natural feel. Filtration, or at least water flow, should be relatively gentle, and use a soft substrate if possible since Oreichthys species have miniscule sensory bristles on the lower jaw which are used when foraging.

Water Conditions

Temperature: 23 – 28 °C

pH: 6.0 – 7.5

Hardness: 36 – 179 ppm

Diet

Will accept dried foods of a suitable size but should not be fed these exclusively. Daily meals of small live and frozen fare such as Daphnia, Artemia and suchlike will result in the best colouration and encourage the fish to come into breeding condition. It’s noted as something of a shy, reluctant feeder (see below).

Behaviour and CompatibilityTop ↑

Unsuitable for most community aquaria as it may be intimidated or outcompeted for food by larger or more boisterous tankmates.

Small, peaceful cyprinids such as Trigonostigma or Boraras species make good choices and we suspect it will also do ok with many South American characins, Otocinclus or pygmy Corydoras catfishes.

Although gregarious by nature it’s a shoaling rather than schooling fish which develops a distinct pecking order and rival males will exhibit some interesting sparring behaviour in captivity. It’s best maintained in a group of 8 or more but the tank must be decorated in such a way that many broken lines of sight are provided. If kept singly, in a very small group or in cramped conditions it can become withdrawn and subdominant fish may be bullied incessantly.

Sexual Dimorphism

Males grow a little larger than females, exhibit stronger colouration on the body and fins, and develop an extended dorsal-fin, while sexually-mature females possess a noticeably-rounded abdomen during the spawning season.

Reproduction

Like many small cyprinids this species is an egg-scattering, continuous spawner that exhibits no parental care. When in spawning condition small numbers of eggs will be laid daily, and in a mature, well-decorated aquarium as described above it’s possible that small numbers of fry may start to appear without intervention.

However if you want to increase the yield a slightly more controlled approach is required, with perhaps the best method involving isolation of one or two pairs in a separate aquarium containing nylon spawning mops or bunches of broad-leaved vegetation such as Anubias spp.

Females deposits eggs onto the underside of broad plant leaves or other solid surfaces while swimming in an inverted position as in Pethia gelius, P. canius, and Trigonostigma species. An additional interesting behaviour noted by Schäfer (2009) is the tendency of some subordinate males to maintain a small body size and dorsal-fin, thus assuming the general appearance of females. Such individuals were observed to display ‘sneaking’ behaviour during the spawning period, but if isolated from other males began to develop the typical extended dorsal-fin after around 8 weeks.

The pair(s) can be left in situ for two or three days then removed as the first eggs should hatch by the third day after the initial spawning. The fry will survive on their yolk sacs for around 5 more days after which Paramecium or other microscopic food is required for the initial period. After 8 days they should be large enough to accept Artemia nauplii, microworm, etc.

NotesTop ↑

This fish is sometimes traded as Oreichthys cosuatis, Oreichthys sp. ‘high fin‘, O. ‘umangii’ (a nomen nudum that has only ever been applied to an image of a fish in the book ‘Ornamental Aquarium Fish of India’ by K. L.Tekriwal and A. A. Rao), Puntius ‘arunavii’, or ‘neon highfin barb‘.

It can be distinguished from congeners by the following combination of characters: absence of a dark marking in the anal-fin (vs. presence in other species); ½7½ scales scales between pelvic-fin origin and dorsal midline (vs. ½6½ in O. cosuatis and O. parvus); snout blunt (vs. pointed); black marking at caudal-fin base large and well-defined (vs. absent or small and poorly-defined); 11-13 rows of pores on ventral surface of head; males with significantly enlarged dorsal-fin; pharyngeal teeth arranged in three rows (1-3-4).

It seems certain that new species of Oreichthys will be described in the future as there exist at least three undescribed forms from Myanmar, four from India (including one said to originate in the Western Ghats mountain range, thus greatly extending the range of the genus), and possibly others from Thailand and the Mekong basin in laos.

Distinguishing some of these from one another and the described species can be tricky; one variant from the Dibru River in Tinsukia District, Assam state, India is very similar to O. cosuatis but has a less rounded dorsal-fin, for example, while other variants from Myanmar differ in fin colour or patterning such as the extent of the dark blotch at the caudal peduncle with the latter absent in some forms.

The genus is defined by the following characters: small size up to 43 mm SL; body deep, stout and strongly compressed; barbels absent; head with rows of fine pores, normally concentrated on the snout, interorbital area, cheeks, and opercle; simple dorsal and anal-fin rays soft and smooth; 17-21+2 scales in lateral series; lateral line visible; 3 simple and 8 branched dorsal-fin rays; 3 simple and 5 branched anal-fin rays; abdomen rounded anterior to pelvic-fin origgin, with a scaled keel between pelvic-fin base and anal-fin origin; pharyngeal teeth arranged in 3 rows of unequal length forming a pyramidal shape; prsenec of dark-grey, crescent-shaped marking on each scale; symphysal knob absent; gill rakers absent; no spine anterior to dorsal-fin origin.

The sensory pores on the snout, cheeks, throat, opercle and interorbital areas are lacking in most other cyprinids but present in a few genera including Eirmotus, Cyclocheilichthys, Neobarynotus, and a handful of other species.

Thanks to Andrew Rao.

References

1. Schäfer, F., 2009 - Ichthyological Exploration of Freshwaters 20(3): 201-211
   Oreichthys crenuchoides, a new cyprinid from west Bengal, India.
2. Tan, H.H. and M. Kottelat, 2008 - Raffles Bulletin of Zoology 56(2): 423-433
   Revision of the cyprinid fish genus Eirmotus, with description of three new species from Sumatra and Borneo.
3. Tekriwal, K. L. and A. A. Rao, 1999 - Kingdom Books: 1-144
   Ornamental Aquarium Fish of India
4. V. Vilasri, 2002 - The Natural History Journal of Chulalongkorn University 2(1): 64-65
   Oreichthys parvus Smith, 1933 (Teleostei: Cyprinidae), an Addition to the Fish Record from the Peat Swamp, Southern Thailand.