Xenentodon canciloides (BLEEKER, 1854)

SynonymsTop ↑

Belone canciloides Bleeker, 1854

Etymology

Xenentodon: from the Greek ξένος (xénos), meaning ‘strange’, and ὀδών (odṓn), meaning ‘tooth’, in reference to the lower pharyngeal plate.

canciloides: ‘resembling cancila‘.

Classification

Order: Beloniformes Family: Belonidae

Distribution

Known with certainty from the Greater Sunda Islands of Borneo and Sumatra, Peninsular Malaysia and Thailand, and also considered to occur in the Mekong system in Laos, Cambodia and Vietnam.

Type locality is given as both ‘Kapuas River, Pontianak, Borneo’ and ‘Pangaboeang, Lampong, Sumatra, Indonesia’.

Habitat

Tends to inhabit slow-moving to still sections of streams and rivers and marshy lowland habitats such as swamps and oxbows although at certain times of year it may also be found in fast-flowing waters and has also been collected from man-made canals and irrigation channels.

Maximum Standard Length

250 – 300 mm.

Aquarium SizeTop ↑

An aquarium with surface dimensions of 180 ∗ 60 cm or more is recommended.

Water depth is less important but should not be less than 30 cm.

Maintenance

This species is a near-exclusive inhabitant of the upper water column and appreciates surface cover in the form of floating or overhanging vegetation.

Other décor is relatively unimportant, but could consist of a sandy substrate with leaf litter plus some large driftwood branches and twisted roots. Plants which can grow rooted in sand can also be added as can those which grow attached to solid surfaces such as Microsorum, Taxiphyllum or Anubias spp. Lighting can simply be tailored to the plants being used.

If using a deeper tank you could fill it to 50-70% of capacity and add emergent branches and plants which can look very effective. A tightly-fitting cover should be used as this species may jump when startled, however.

Efficient filtration is a must when keeping predatory species due to the amount of waste produced so install one or more external canister filters and/or a sump system, organising the return in such a way that turbulent flow is avoided.

Weekly water changes of 30-50% should be considered mandatory as this species can be sensitive to organic pollutants and swings in water chemistry, and for this reason it must never be introduced to biologically immature set-ups.

Although sometimes referred to as such it is not normally an inhabitant of brackish waters, though it may enter them from time-to-time at coastal localities. Marine salt is not necessary for its well-being.

Water Conditions

Temperature: 18 – 26 °C

pH: 6.0 – 8.0

Hardness: 36 – 268 ppm

Diet

An obligate predator feeding mostly on smaller fishes and insects in nature, and can be tricky to wean onto dead alternatives in captivity.

Smaller specimens can be offered bloodworm, small earthworms, chopped prawn and suchlike while adults should accept strips of fish flesh, whole prawns/shrimp, mussels, live river shrimp, larger earthworms, etc. Insects such as crickets or are also ideal when fed live, although it is best to fill the stomachs of these by feeding them flaked fish food or some kind of vegetable matter prior to use.

Take care not to overfeed as it will gorge itself given the opportunity.

Like the vast majority of predatory fishes this species should not be fed mammalian or avian meat such as beef heart or chicken. Some of the lipids contained in these cannot be properly metabolised by the fish and can cause excess fat deposits and even organ degeneration.

Similarly there is little benefit in the use of ‘feeder’ fish such as livebearers or small goldfish unless they are properly quarantined and conditioned beforehand, otherwise they bring with them the risk of parasite or disease introduction and tend not have a high nutritional value.

Behaviour and CompatibilityTop ↑

Surprisingly peaceful with anything too large to swallow, and can be maintained in a community provided tankmates are chosen with care since it is also a poor competitor.

This species is not aggressive towards conspecifics with juveniles in particular exhibiting a marked schooling instinct, and it is best maintained in numbers of four or more.

Sexual Dimorphism

Sexually mature male specimens apparently develop a pronounced dorsal ‘hump’ immediately posterior to the head.

Reproduction

Unrecorded.

NotesTop ↑

This species is rarely seen in the ornamental trade, with its congener X. cancila far more common.

Both are often seen referred to as ‘freshwater garfish’, and although they do superficially resemble the true gars of the family Lepisosteidae, they’re actually members of the Belonidae, or needlefishes, the majority of which are marine or estuarine in existence.

There are currently just two species in the genus although the probable existence of a third member has been noted by Roberts (1989) among other authors and the grouping may prove significantly more diverse than is understood at the moment.

Following Roberts (1989) X. canciloides can be distinguished from its only congener X. cancila by the following combination of characters: jaws relatively slender and delicate (vs. relatively large and heavy-set in X. cancila); length of upper jaw fits 2.3-2.6 times in body length measured from anterior margin of orbit to end of hypural plate (vs. 2.6-3.2 times); 21-32 enlarged teeth in upper jaw (vs. 9-21); dorsal-fin origin usually above second or third anal-fin ray (vs. dorsal-fin origin usually anterior to a vertical through anal-fin origin); body relatively small, slender and not exceeding 30 cm TL (vs. heavy-bodied and reaching 40 cm TL).

Roberts (1989) als0 defined the genus Xenentodon as follows: body cylindrical; jaws with large canine teeth alternating with much smaller conical teeth; one pair of pharyngeal teeth; gill rakers absent; scales small to extremely small; lateral line placed very low on body but not forming keel on caudal peduncle; dorsal and anal fins about equal in size and almost opposite each other with 14-19 rays; caudal-fin rounded or truncate; vertebrae 55-62.

Members of the family Belonidae are separated form the remainder of the Order Beloniformes by the following characters: lower jaws extended into a long ‘beak’ filled with sharp teeth (except in the neotenic genus Belonion); third pair of upper pharyngeal bones separate; body scales relatively small; no finlets posterior to the dorsal and anal fins; nostrils located in a pit anterior to the eyes; no spinous fin rays; dorsal fin with 11–43 rays and anal fin with 12–39 rays, both fins posterior in position; pelvic fins with 6 soft rays and located in an abdominal position; pectoral fins short with 5–15 rays; lateral line orientated ventrally from pectoral-fin origin and running along ventral margin of body; scales small, cycloid, and easily detached; precaudal vertebrae 33–65; caudal vertebrae 19–41; total vertebrae 52–97.

Some freshwater needlefishes reach only 60-70 mm in total length while certain marine species can attain 2000 mm (2 metres). There are currently ten recognised genera of which the majority are  monotypic or contain only two or three species. Most are contained in the relatively diverse genera Tylosurus and Strongylura although the latter in particular is probably polyphyletic and may be split in the future.

References

1. Bleeker, P., 1854 - Natuurkundig Tijdschrift voor Nederlandsch Indië v. 5: 427-462
   Zevende bijdrage tot de kennis der ichthyologische fauna van Borneo. Zoetwatervisschen van Sambas, Pontianak en Pangaron [sic, Pengaron].
2. Collette, B. B., 2003 - California Academy of Sciences Annotated Checklists of Fishes No. 16: 1-22
   Family Belonidae Bonaparte 1832 - needlefishes.
3. Kottelat, M., 2001 - WHT Publications, Colombo: 1-198
   Fishes of Laos.
4. Kottelat, M., 2001 - Environment and Social Development Unit, East Asia and Pacific Region. The World Bank: i-iii + 1-123 + 1-18
   Freshwater fishes of northern Vietnam. A preliminary check-list of the fishes known or expected to occur in northern Vietnam with comments on systematics and nomenclature.
5. Kottelat, M. and E. Widjanarti, 2005 - The Raffles Bulletin of Zoology Supplement 13: 139-173
   The fishes of Danau Sentarum National Park and the Kapuas Lakes area, Kalimantan Barat, Indonesia.
6. Lim, K. K. P., P. K. L. Ng and M. Kottelat, 1990 - Bulletin of the Raffles Museum 38(1): 31-54
   On a collection of freshwater fishes from Endau-Rompin, Pahang-Johore, Peninsular Malaysia.
7. Lovejoy, N. M., M. Iranpour and B. B. Collette, 2004 - Integrative and Comparative Biology 44(5): 366-377
   Phylogeny and Jaw Ontogeny of Beloniform Fishes.
8. Lovejoy, N. R. and B. B. Collette, 2001 - Copeia 2001(2): 324-338
   Phylogenetic Relationships of New World Needlefishes (Teleostei: Belonidae) and the Biogeography of Transitions between Marine and Freshwater Habitats.
9. Ng, H. H. and H.-H. Tan, 1999 - Zoological Studies 38(3): 350-366
   The fishes of the Endau drainage, Peninsular Malaysia with descriptions of two new species of catfishes (Teleostei: Akysidae, Bagridae).
10. Rainboth, W. J., 1996 - FAO, Rome: 1-265
    Fishes of the Cambodian Mekong. FAO Species Identification Field Guide for Fishery Purposes.
11. 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).
12. Tan, H. H. and M. Kottelat, 2009 - Ichthyological Exploration of Freshwaters 20(1): 13-69
    The fishes of the Batang Hari drainage, Sumatra, with description of six new species.