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'Puntius' rhomboocellatus KOUMANS, 1940

Snakeskin Barb

SynonymsTop ↑

Systomus rhomboocellatus (Koumans, 1940); Barbus tetrazona Bleeker, 1856; Barbus kahajani Hoedeman, 1956

Etymology

rhomboocellatus: from the Latin rhombus, meaning ‘rhombus’, and ocellatus, meaning ‘having small eyes, ocellated’, in reference to this species’ colour pattern.

Classification

Order: Cypriniformes Family: Cyprinidae

Distribution

Endemic to southern Kalimantan, the Indonesian portion of Borneo where it’s been recorded from several river systems including the Kapuas, Kepayang, Barito and Kahajan. Type locality is given as ‘Canal along the highway from Oelin to Bandjermasin, about 15 kilometers from Bandjermasin, Borneo.’

Habitat

Most often inhabits peat swamps and associated black water streams as well as other still waters, often in areas with submerged grasses or aquatic plants and dense riparian vegetation. The water itself is typically stained brown with humic acids and other chemicals released by decaying organic material, dissolved mineral content is generally negligible and pH as low as 3.0 or 4.0. Substrates are usually littered with fallen leaves, branches and submerged tree roots though in some places aquatic plants from genera such as Cryptocoryne or Barcalaya can be found.

Maximum Standard Length

50 – 55 mm.

Aquarium SizeTop ↑

Base dimensions of at least 80 ∗ 30 cm or equivalent are required.

Maintenance

Will thrive in a heavily-planted or forest stream-type set-up, the latter comprising a soft substrate, dim lighting, roots, branches and leaf litter. You could also add aquatic plants that can survive under such conditions such as Microsorum, Taxiphyllum, or Cryptocoryne spp. Filtration does not need to be particularly strong as it mostly hails from sluggish waters.

Water Conditions

Temperature: 20 – 28 °C pH: 4.0 – 7.0 Hardness: 18 – 90 ppm

Diet

Primarily a micropredator feeding on small insects, worms, crustaceans and other zooplankton in nature. In the aquarium it 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.

Behaviour and CompatibilityTop ↑

An ideal addition to a peaceful community of Southeast Asian fishes with comparably-sized cyprinids, cobitids, and certain anabantoids perhaps constituting the best choices. Some of the more commonly-exported species from Borneo include ‘Puntius‘ johorensis, ‘P.‘ hexazona, Brevibora dorsiocellata, Trigonopoma pauciperforatum, Rasbora einthovenii, and various Pangio spp. Avoid boisterous or very vigorous tankmates as they may outcompete it for food. It’s a schooling species by nature, and ideally should be kept in a group of at least 8-10 specimens. Maintaining it in decent numbers will not only make the fish less skittish but result in a more effective, natural-looking display, plus males will also display their best colours as they compete with one other for female attention.

Sexual Dimorphism

Adult males tend to be slightly smaller, are noticeably slimmer and exhibit more intense colouration than females.

Reproduction

Possibly unrecorded but recommendations for related species are as follows:

NotesTop ↑

‘P.‘ rhomboocellatus is often referred to as the ‘rhomb’ or ‘rhombo’ barb and is one of a group of closely-related, similar-looking congeners which also includes  ’P.‘ endecanalis, ‘P.‘ foerschi, ‘P.‘ hexazona, and ‘P.‘ pentazona, , these forming part of the larger ‘P.‘ tetrazona assemblage (see below). They’re all distinguishable by colour pattern; in P. endecanalis base body colouration is whitish vs. reddish to orange in the other species; in  ’P.‘ foerschi there are additional dark blotches between the second, third and fourth vertical bars and a further marking at the posterior base of the dorsal-fin; in  ’P.‘ hexazona base body colour is orange-red and the vertical body bars relatively uniform; in  ’P.‘ rhombooccelatus the dark, vertical body bars are expanded laterally and split in the middle, forming roughly diamond-shaped ‘ocellate rhombi’; in  ’P.‘ pentazona colour pattern is almost identical to that of ’P.‘ hexazona but there is an additional, small, dark marking at the posterior base of the dorsal-fin. The genus Puntius was viewed as a polyphyletic catch-all containing over 100 species of small to mid-sized cyprinid for a number of years until Pethiyagoda et al. (2012) published a partial review covering South Asian members. The majority of sub-Himalayan Puntius species were reclassified and new genera Dawkinsia, Dravidia, and Pethia erected to accomodate some of them, with the remainder either retained in Puntius or moved to the existing Systomus assemblage, though the definition of the latter was altered meaning some Southeast Asian species formerly placed there are no longer members. It subsequently became clear that the name Dravidia was preoccupied by a genus of flesh fly, therefore the replacement name Haludaria was made available by Pethiyagoda (2013). No species from Indochina, China, or Indonesia were included in the study meaning a significant number of former Puntius are currently classed as incertae sedis, i.e., of uncertain taxonomic placement, and this also applies to a number of South Asian species of unresolved status. They’re perhaps best referred to as ‘Puntius‘ for the time being whereby the genus name is surrounded by quotation marks to denote its questionable usage, and that is the convention used here on SF at the moment. Within the Southeast Asian species several species ‘groups’ were defined by Pethiyagoda et al., and ‘P.‘ hexazona is included in the ‘Puntius tetrazona group’, members of which are characterised by possession of serrations on the posterior edge of the last unbranched dorsal-fin ray, maxillary barbels, and a colour pattern comprising 3-6 black vertical bars and/or blotches on the body. The lateral line may be complete or incomplete and rostral barbels present or absent. Other ‘P.‘ tetrazona group members include ’P.‘ anchisporus, ‘P.‘ endecanalis, ‘P.‘ foerschi, ‘P.‘ navjotsodhii, ’P.‘ partipentazona, ‘P.‘ pentazona, ‘P.‘ pulcher, ‘P.‘ rhomboocellatus, and ‘P.‘ tetrazona.

References

1. Kottelat, M., 1992 - Raffles Bulletin of Zoology 40(2): 187-192
   The identity of Barbus johorensis Duncker, 1904 (Teleostei: Cyprinidae).
2. Kottelat, M. and E. Widjanarti, 2005 - Raffles Bulletin of Zoology Supplement 13: 139-173
   The fishes of Danau Sentarum National Park and the Kapuas Lakes area, Kalimantan Barat, Indonesia.
3. Kottelat, M. and H-H Tan, 2011 - Ichthyological Exploration of Freshwaters 22(3): 209-214
   Systomus xouthos, a new cyprinid fish from Borneo, and revalidation of Puntius pulcher (Teleostei: Cyprinidae).
4. Pethiyagoda, R., 2013 - Zootaxa 3646(2): 199
   Haludaria, a replacement generic name for Dravidia (Teleostei: Cyprinidae).
5. Pethiyagoda, R., M. Meegaskumbura, and K. Maduwage, 2012 - Ichthyological Exploration of Freshwaters 23(1): 69-95
   A synopsis of the South Asian fishes referred to Puntius (Pisces: Cyprinidae).
6. Roberts, T. R., 1989 - Memoirs of the California Academy of Sciences 14: i-xii + 1-210
   The freshwater fishes of western Borneo (Kalimantan Barat, Indonesia).