Homalopterula gymnogaster (BLEEKER, 1853)

SynonymsTop ↑

Homaloptera lepidogaster Weber & de Beaufort, 1916; Homaloptera gymnogaster (Bleeker, 1853)

Etymology

Homalopterula: from the generic name Homaloptera, a grouping within which this species was formerly placed, and the Latin suffix -ula, meaning ‘small’.

gymnogaster: from the Greek γυμνός ‎(gumnós), meaning ‘naked, bare’, and γαστήρ (gastḗr), meaning ‘stomach, belly’, in reference to the scaleless ventral surface between the ventral fins.

Classification

Order: Cypriniformes Family: Balitoridae

Distribution

Type locality is given as ‘Lake Meninju, Sumatra, Indonesia’, currently known as Danau (lake) Maninjau, but conceivably the fish may have been obtained from the outflowing Antokan river rather on its western side than the lake itself.

Additional occurrence records are not extensive, but it appears to occur throughout much of the island with a range extending northwards from Jambi province at least as far as the Sungai (river) Bohorok in Karo Regency, North Sumatra province.

Habitat

Tan and Kottelat (2009) describe it as a relatively common, highland species inhabiting riffles and ‘quiet waters’, which we assume to mean lakes.

For example, Maninjau is a caldera lake formed by a volcanic eruption estimated to have occurred around 52,000 years ago so is also young in geographic terms, and the Antokan is its only outflowing river. The latter is dammed in its upper reaches.

In the headwaters of the Batang Hari river this species has also been recorded at 1950 m AMSL, higher than any other balitorid in Sumatra, in Danau Gunung Tujuh, another caldera lake located at the border between Jambi and West Sumatra provinces in Kerinci Seblat National Park.

H. gymnogaster is therefore unusual in that Homaloptera spp. are not normally associated with standing water bodies, although it remains unclear if the fish are collected from outflowing rivers or the lakes themselves.

Maximum Standard Length

60 – 65 mm.

Aquarium SizeTop ↑

An aquarium with base dimensions of 80 ∗ 30 cm or more ought to prove sufficient.

Maintenance

Most importantly the water must be clean and well-oxygenated so we suggest the use of an over-sized filter as a minimum requirement.

Turnover should ideally be 10-15 times per hour so additional powerheads, airstones, etc., should be employed to achieve the desired flow and oxygenation if necessary.

Base substrate can either be of gravel, sand or a mixture of both to which should be added a layer of water-worn rocks and pebbles of varying sizes.

Driftwood roots and branches are also suitable and although rarely a feature of the natural habitat aquatic plants from genera such as Microsorum, Crinum and Anubias spp. can be grown attached to the décor. The latter are particularly useful as Homaloptera spp. appear to enjoy resting on their leaves.

Since it needs stable water conditions this species should never be added to a biologically immature set-up, although while regular partial water changes are essential aufwuchs can be allowed to grow on all surfaces except perhaps the viewing pane.

Water Conditions

Temperature: 20 – 27 °C

pH: 6.0 – 7.5

Hardness: 18 – 143 ppm

Diet

Homalopterula spp. are specialised grazers feeding on biofilm, small crustaceans, insect larvae and other invertebrates.

In captivity some sinking dried foods may be accepted but regular meals of live or frozen Daphnia, Artemia, bloodworm, etc., are essential for the maintenance of good health, and it’s highly preferable if the tank contains rock and other solid surfaces with growths of algae and other aufwuchs.

Balitorids are often seen on sale in an emaciated state which can be difficult to correct. A good dealer will have done something about this prior to sale but if you decide to take a chance with severely weakened specimens they’ll initially require a continual, easily-obtainable source of suitable foods in the absence of competitors if they’re to recover.

Behaviour and CompatibilityTop ↑

Unconfirmed, but experience with congeners suggests it will not prove aggressive in a community arrangement.

Species inhabiting similar environments include Barilius, Discherodontus, Garra, Devario, some Rasbora, gobies of the genera Rhinogobius, Sicyopterus and Stiphodon plus Glyptothorax, Akysis and Oreoglanis spp. catfishes.

Many loaches from the family Nemacheilidae and most from Balitoridae are also suitable although harmless squabbles may occur with the latter group in particular. Research your choices before purchase to be sure.

It’s found living in aggregations in nature so buy six or more to see it at its best as when kept singly, in pairs or trios trios it’s less bold.

The interaction between individuals is also interesting to watch and a group will typically arrange themselves close to one another facing directly into the water flow at certain times of day.

Sexual Dimorphism

Sexually mature females are probably a little larger and fuller-bodied than males.

Reproduction

Unrecorded.

NotesTop ↑

Fowler (1940) created the genus Homalopterula for the new species Homalopterula ripleyi Fowler 1940 and distinguished it from other balitorids by the “peculiar shape of its jaws, in combination with its truncated caudal and entirely naked medial under surface of the abdomen” (Fowler 1940, p. 379).

Silas (1953) treated Homalopterula as a junior synonym of Homaloptera based on the illustration provided in Fowler’s type description and the variation that “exists regarding the nature of the caudal and presence or absence of scales on the ventral surface of the abdomen in species of Homaloptera.”  Roberts (1989) followed this decision.  Kottelat (1998) recognized four species (H. ripleyi, H. gymnogaster, H. heterolepis and H. vanderbiltias) as possibly forming a clade (Homalopterula) based on “a more cylindrical body, a relatively wide mouth, short paired fins, and a truncated or slightly emarginated caudal fin,” and using this description, Tan & Ng (2005) and Ott (2009) treated Homalopterula as a subgenus of Homaloptera.

Randall and Page (2012) considered Homalopterula a putative subgenus within Homaloptera and also containing the four afore-mentioned species.  All four are native to Sumatra and separated from congeners by their more cylindrical than compressed body shape, relatively wide mouth, short paired fins andtruncate caudal-fin shape.

Randall & Page (2015) raised Homalopterula to full generic status, and it currently contains H. gymnogaster(Bleeker 1853), H. modiglianii (Perugia 1893), H. amphisquamata (Weber & Beaufort 1916), H. heterolepis(Weber & de Beaufort 1916), H. ripleyi Fowler 1940 [the type species], and H. vanderbilti (Fowler 1940).  Homalopterula is only known to occur in Sumatra.

Homalopterula is distinguished by the following combination of characters: without reddish tints on fins in life; dorsal-fin origin posterior to pelvic-fin origin; 5½ and 7½, 7½ (M) branched dorsal-fin rays; 7 pelvic-fin rays; truncated or emarginated caudal fin; smooth scales, 57–75 total lateral-line scales, 28–56 predorsal scales; anus closer to anal-fin origin than to pelvic-fin base; adipose keel on caudal peduncle; small rostral cap; 2 thick and widely separated rostral barbels; thick crescentic upper lip; 2 fleshy lobes between lateral portions of lower lip; and presence of a central furrow at the isthmus.

H. gymnogaster has 60-73 lateral-line scales and its belly is naked anterior to the ventral fins.

The genus Homaloptera van Hasselt, 1823 has long been considered a polyphyletic assemblage (Kottelat, 1998), and following Randall & Page (2015) the majority of members have been moved into other genera as recognized therein:

Homalopteroides Fowler, 1905 with 11 species (Homalopteroides wassinkii, H. modestus, H. rupicola, H. smithi, H. stephensoni, H. weberi, H. tweediei , H. indochinensis, H. nebulosus, H. yuwonoi, and H. avii), is the most diverse and widely distributed genus of species formerly in Homaloptera. It is known from northeast India, Myanmar, Thailand, Laos, Cambodia, Vietnam (? see Kottelat 2012:51), Peninsular Malaysia, Sumatra, Java, and Borneo.

Homalopterula Fowler, 1940 is only known to occur in Sumatra and consists of six species, five described from Aceh Province (H. heterolepis, H. ripleyi, H. modiglianii, H. amphisquamata, and H. vanderbilti) and H. gymnogaster from Sumatera Barat province.

Balitoropsis Smith, 1945 contains two species, B. zollingeri and B. ophiolepis.  The original type species B. bartschi (Smith, 1945) is now considered synonymous with B. zollingeri.

Pseudohomaloptera Silas, 1953, which has not been valid since 1953, now contains six species (P. tatereganii, P. sexmaculata, P. leonardi, P. yunnanensis, P. vulgaris, and P. batek) and is known to occur in southern China, Thailand, Laos, Cambodia, Peninsular Malaysia, and Borneo.

Ghatsa Randall & Page, 2015, contains the type species G. montana Herre, 1945, and four tentatively assigned species (G. pillaii, G. menoni, G. santhamparaiensis, and G. silasi).

Homaloptera van Hasselt, 1823, consists of six species (H. ocellata, H. bilineata, H. orthogoniata, H. ogilviei, H. confuzona, and H. parclitella) found in Myanmar, Thailand, Cambodia, Peninsular Malaysia, Sumatra, Java, and Borneo.

These loaches make fascinating aquarium inhabitants and are often referred to as ‘lizard’ loaches due to their behaviour and appearance. Like all balitorids they have morphology specialised for life in fast-flowing water, i.e., the paired fins are orientated and extended horizontally, head and body flattened, belly depressed.  These features form a powerful sucking cup which allows the fish to cling tightly to solid surfaces. The ability to swim in open water is greatly reduced and they instead appear to crawl and hop their way over rocks and other surfaces.

The family Balitoridae as recognised by Kottelat (2012) is widely-distributed across much of the Indian subcontinent, Southeast Asia and China.

References

1. Bleeker, P., 1853 - Natuurkundig Tijdschrift voor Nederlandsch Indië v. 4: 155-164
   Over eenige nieuwe soorten van Homaloptera v. Hass. (Balitora Gray) van Java en Sumatra.
2. Kottelat, M., 2012 - Raffles Bulletin of Zoology Supplement 26: 1-199
   Conspectus cobitidum: an inventory of the loaches of the world (Teleostei: Cypriniformes: Cobitoidei).
3. Kottelat, M., 2013 - Raffles Bulletin of Zoology Supplement 27: 1-663
   The fishes of the inland waters of southeast Asia: a catalogue and core bibliography of the fishes known to occur in freshwaters, mangroves and estuaries.
4. Ott, G., 2009 - Bulletin of Fish Biology 11(1/2): 73-86
   Redescription of Homaloptera ripleyi (Fowler, 1940) from Sumatra, Indonesia (Teleostei: Balitoridae).
5. Randall, Z. S. and L. M. Page, 2012 - Zootaxa 3586: 329-346
   Resurrection of the genus Homalopteroides (Teleostei: Balitoridae) with a redescription of H. modestus (Vinciguerra 1890)
6. Randall, Z. S. and L. M. Page, 2015 - Zootaxa 3926(1): 57-86
   On the paraphyly of Homaloptera (Teleostei: Balitoridae) and description of a new genus of hillstream loaches from the Western Ghats of India.
7. 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.