Pseudohomaloptera sexmaculata (FOWLER, 1934)

SynonymsTop ↑

Homaloptera sexmaculata Fowler, 1934; Homaloptera septemmaculata Fowler, 1934; Balitoropsis sexmaculata (Fowler, 1934)

Etymology

Pseudohomaloptera:  From the Greek ψευδής, pseudes, meaning lying, false; and the generic name Homaloptera.

sexmaculata:  From the latin sex, meaning ‘six’ and macula, meaning ‘spot’, in reference to the six principal dark saddle-like markings on the dorsal surface of the body.

Classification

Order: Cypriniformes Family: Balitoridae

Distribution

Type locality is ‘Chieng Mai, North Siam’, which corresponds to Chaing Mai province, northern Thailand.

The Ping River, a major tributary of the Chao Phraya system, flows through Chiang Mai and H. sexmaculata is known only from the Chao Phraya and Mae Klong watersheds of which both are located entirely within central and western Thailand.

Habitat

An obligate dweller of swiftly-flowing streams and headwaters containing clear, oxygen-saturated water. Adults usually inhabit riffles and runs, and show a preference for shallower zones with substrates of gravel, rocks, boulders or bedrock, typically carpeted by a rich biofilm formed by algae and other micro-organisms.

Juveniles are often found in slower-moving stretches with gravel substrate and submerged woodt structures such as tree roots. In both cases patches of aquatic plants are only occasionally present but riparian vegetation is usually well-developed.

At the type locality of Schistura bella (Kottelat, 1990) in the Kok River, Chiang Mai Province, northern Thailand H. sexmaculata was collected alongside various other species including Schistura breviceps, Homalopteroides smithi, Acanthopsoides gracilentus, Pethia ticto, an unidentified Barilius sp., and Rhinogobius mekongianus.

Maximum Standard Length

60 – 70 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 and feeds on biofilm this species should never be added to a biologically immature set-up, and a tightly-fitting cover is necessary since it can literally climb glass.

While regular partial water changes are essential aufwuchs can be allowed to grow on all surfaces except perhaps the viewing pane.

Water Conditions

Temperature: 68 – 78 °C

pH: 6.0 – 7.5

Hardness: 18 – 215 ppm

Diet

Homaloptera 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 ↑

Not an aggressive fish although its environmental requirements limit the choice of suitable tankmates plus it is naturally reclusive.

Species inhabiting similar environments include Danio, Devario, some Rasbora, Rhinogobius, Sicyopterus and Stiphodon gobies plus catfishes like Glyptothorax, Akysis and Oreoglanis.

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

Homaloptera spp. aren’t particularly territorial towards conspecifics and seem to require their presence to thrive, meaning the purchase of four or more is recommended.

Sexual Dimorphism

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

Reproduction

Unrecorded.

NotesTop ↑

Fowler (1934) described the subject species in the genus Homaloptera where it remained until Kottelat (2012) placed it in Balitoropsis.  Randall & Page (2012) considered this species a member of the putative subgenus Balitoropsis which also contained H. maxinae, H. ophiolepis, H. sexmaculata, H. tateregani, H. vulgaris, H. yunnanensis and H. zollingeri.  These share a relatively elongate body, narrow caudal peduncle, carinate/keeled scales, relatively short paired fins (pectorals don’t usually reach pelvic-fin base, pelvics don’t usually reach anal-fin) and a dark body colouration with a series of saddle-shaped markings running along the dorsal surface.  None are particularly common in the trade and mostly turn up as contaminants among shipments of other species, though when available in numbers they’re usually sold as ‘gecko’ loaches.

Homaloptera has long been considered a polyphyletic assemblage (Kottelat, 1998), and some former members were moved into the revalidated genus Homalopteroides (Fowler, 1905) by Randall and Page (2012) on the basis of their oral morphology.  Following Randall and Page the species remaining in Homaloptera were distributed between Balitoropsis and two other subgenera of which the H. ocellata group retains the name Homaloptera since H. ocellata is the type species of the genus.  The Sumatran species constituted the subgenus Homalopterula Fowler, 1940, while those from southern India were considered to possibly represent a distinct genus as well.  Kottelat (2012) considered these subgenera as valid, distinct genera, whereas Randall and Page (2012) concluded that further study was necessary in order to be certain of their taxonomic status.

The genus Pseudohomaloptera was initially raised by Silas (1953) for the type species Homaloptera tatereganii Popta 1905.  Pseudohomaloptera was distinguished from Homaloptera by the “presence of a rostral groove and other structures associated with the mouth” (Silas 1953, p. 205).  Tan (2009) noted that all Homaloptera species have a rostral and postoral groove to some degree, and he recognized Pseudohomaloptera as a junior synonym of Homaloptera.  Kottelat (2012) also recognized this synonymy.

Randall and Page (2015) revalidated Pseudohomaloptera as a distinct genus, with the species Pseudohomaloptera tatereganii (Popta 1905), P. sexmaculata (Fowler 1934), P. leonardi
(Hora 1941), P. yunnanensis (Chen 1978), P. vulgaris (Kottelat & Chu 1988), and P. batek (Tan 2009).

Pseudohomaloptera is distinguished by the following combination of characters: without reddish tints on fins in life; dorsal-fin origin anterior to or above pelvic-fin origin; 8½ branched dorsal-fin rays; 8–9 branched pelvic-fin rays; forked caudal fin; keeled scales; 50–61 total lateral-line scales; 13–19 predorsal scales; anus closer to anal-fin origin than to pelvic-fin insertion; no adipose keel on caudal peduncle; large rostral cap; 2 thick rostral barbels in close proximity to one another; thick and triangular/crescentic upper lip; fleshy pad between lateral portions of lower lip.

P. sexmaculata is very similar to P. leonardi but can be told apart since it possesses 2 simple and 12-14 branched pectoral-fin rays (versus 6 simple and 11 branched rays). Both of these species are sometimes misidentified as P. yunnanensis which has 7 simple and 12 branched pectoral-fin rays.

All these species 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. Fowler, H. W., 1934 - Proceedings of the Academy of Natural Sciences of Philadelphia v. 86: 67-163
   Zoological results of the third De Schauensee Siamese Expedition, Part I.--Fishes.
2. Beamish, F. W. H., P. Sa-ardrit and V. Cheevaporn, 2008 - Journal of Fish Biology 72 (10): 2467–2484
   Habitat and abundance of Balitoridae in small rivers of central Thailand.
3. Hora, S. L., 1941 - Bulletin of the Raffles Museum 17: 44-64
   Notes on Malayan fishes in the collection of the Raffles Museum, Singapore. Parts 2 and 3.
4. Kottelat, M., 1990 - Verlag Dr. Friedrich Pfeil, München, Germany: 1-262
   Indochinese nemacheilines. A revision of nemacheiline loaches (Pisces: Cypriniformes) of Thailand, Burma, Laos, Cambodia and southern Viet Nam.
5. Kottelat, M., 1998 - Ichthyological Exploration of Freshwaters 9(3): 267-272
   Homaloptera yuwonoi, a new species of hillstream loach from Borneo, with a new generic name for H. thamicola (Teleostei: Balitoridae).
6. Kottelat, M., 2012 - Raffles Bulletin of Zoology Supplement 26: 1-199
   Conspectus cobitidum: an inventory of the loaches of the world (Teleostei: Cypriniformes: Cobitoidei).
7. Kottelat, M. and X.-L. Chu, 1988 - Cybium 12(2): 103-106
   The genus Homaloptera (Osteichthyes, Cypriniformes, Homalopteridae) in Yunnan, China.
8. 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).
9. 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.
10. Tan, H. H. and P. K. L. Ng, 2005 - Ichthyological Exploration of Freshwaters 16(1): 1-12
    Homaloptera parclitella, a new species of torrent loach from the Malay Peninsula, with redescription of H. orthogoniata (Teleostei: Balitoridae).
11. Tan, H.H., 2009 - Zootaxa No. 2171: 48-64
    A new species of hill stream loach (Teleostei: Balitoridae) from central Kalimantan, with redescriptions of Homaloptera tateregani Popta and Homaloptera stephensoni Hora.
12. Tang, Q., H. Liu, R. Mayden and B. Xiong, 2006 - Molecular Phylogenetics and Evolution 39(2): 347-357
    Comparison of evolutionary rates in the mitochondrial DNA cytochrome b gene and control region and their implications for phylogeny of the Cobitoidea (Teleostei: Cypriniformes).
13. Šlechtová, V., J. Bohlen and H. H. Tan, 2007 - Molecular Phylogenetics and Evolution 44(3): 1358-1365
    Families of Cobitoidea (Teleostei; Cypriniformes) as revealed from nuclear genetic data and the position of the mysterious genera Barbucca, Psilorhynchus, Serpenticobitis and Vaillantella.