Schistura savona (HAMILTON, 1822)

Half-banded Loach

SynonymsTop ↑

Cobitis savona Hamilton, 1822; Nemacheilus savona (Hamilton, 1822); Noemacheilus savona (Hamilton, 1822); Cobites obscura Swainson, 1839;

? Shistura [sic] yenjitee Tekriwal & Rao, 1999 [Kotelat, 2012]

Etymology

Schistura: from the Greek schizein, meaning ‘to divide’, and oura, meaning ‘tail’, in reference to the caudal-fin shape of many species.

savona: appears to have been named in reference to a local vernacular name ‘Savon khorka‘.

Classification

Order: Cypriniformes Family: Nemacheilidae

Distribution

The type series was collected from the Kosi River at Nathpur, Uttar Pradesh state, northern India. The Kosi (aka ‘Koshi’) is a trans-boundary river flowing through Nepal and India, and one of the major tributaries of the Ganges system.

S. savona occurs throughout a number of Ganges affluents draining the eastern Himalayas, from the Karnali and Kali watersheds in Uttar Pradesh to the Teesta in West Bengal and Assam states. Outside India it’s been recorded in Nepal and Bangladesh.

Habitat

The majority of the area over which this species occurs mostly experiences a temperate climate with heavy rainfall, high humidity and a pronounced monsoon period between June and September.

Average air temperatures tend to fall within the range 59 – 90°F/15 – 32°C depending on locality and time of year, though in the northern extreme of its range it can be significantly cooler during winter. Many of its habitats are therefore subject to severe seasonal alteration in terms of water depth, volume and flow.

At the type locality of the catfish Pseudolaguvia muricata in northern Bangladesh the habitat comprised a slow-moving, shallow stream containing clear water with a substrate of sand and organic detritus.

S. savona was recorded alongside numerous other species including Barilius barna, B. bendelisis, B. tileo, Devario devario, Oreichthys cosuatis, Psilorhynchus sucatio, Lepidocephalichthys guntea, Acanthocobitis botia, ‘Nemacheilus‘ corica, Amblyceps mangois, Mystus bleekeri, Olyra longicaudata, Conta conta, Hara jerdoni, Pseudolaguvia ribeiroi, P. shawi, Aplocheilus panchax, Xenentodon cancila, Microphis deocata, Chanda nama, Pseudambassis baculis, P. ranga, Channa gachua, Badis badis, Nandus nandus, Ctenops nobilis, Glossogobius giuris, Mastacembelus pancalus and Tetraodon cutcutia.

Maximum Standard Length

40 – 50 mm.

Aquarium SizeTop ↑

Base dimensions of 60 ∗ 30 cm or equivalent should be the smallest considered.

Maintenance

Not difficult to maintain under the correct conditions. We strongly recommend keeping it in a tank designed to resemble a flowing stream or river with a substrate of variably-sized rocks, sand, fine gravel, and some water-worn boulders.

This can be further furnished with driftwood branches arranged to form a network of nooks, crannies, and shaded spots, thus providing broken lines of sight. While the majority of aquatic plants will fail to thrive in such surroundings hardy types such as Microsorum, Bolbitis, or Anubias spp. can be grown attached to the décor.

Though torrent-like conditions are unnecessary it does best if there is a high proportion of dissolved oxygen and some water movement in the tank meaning power filter(s), additional powerhead(s), or airstone(s) should be employed as necessary.

Like many fishes that naturally inhabit running water it’s intolerant to accumulation of organic pollutants and requires spotless water in order to thrive, meaning weekly water changes of 30-50% tank volume should be considered routine.

Water Conditions

Temperature: 15 – 24 °C

pH: 6.5 – 8.5

Hardness: 36 – 268 ppm

Diet

Schistura species are omnivorous although the bulk of their diet consists of small insects, worms, crustaceans, and other zooplankton with only relatively small amounts of plant matter and other organic detritus consumed.

In the aquarium they 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, bloodworm, etc., will result in the best colouration and condition.

Behaviour and CompatibilityTop ↑

Not among the more aggressive members of the genus and can be maintained in a community aquarium provided tankmates are selected with care and proper research.

Fishes which inhabit similar biotopes in nature, especially those which swim in open water such as Danio, Devario, Pethia, Puntius, and Rasbora spp. perhaps constitute the best options, and one or two schools can make a visible difference to the confidence of benthic species.

Other possibilities include rheophilic loaches from genera such as Pseudogastromyzon, Beaufortia, or Sewellia plus benthic cyprinids such as Crossocheilus and Garra spp. Similarly-shaped relatives aren’t recommended under most circumstances although a combination may work in larger aquaria.

Though not gregarious in the sense of schooling or shoaling fishes it does seem to do best in the presence of conspecifics and provided plenty of cover is available any aggression should be minimal.

Sexual Dimorphism

Adult females are typically a little larger and heavier-bodied than males.

Reproduction

Unrecorded.

NotesTop ↑

This species is seen in the aquarium trade on a relatively frequent basis and is sometimes sold as ‘bicolor loach’ in the United States.

It can be distinguished from congeners by its unique colour pattern comprising 9-10 thin, yellowish bars on a dark background in the upper part of the body, and plain whitish colouration in the lower portion.

Schistura is the most species-rich genus among nemacheilid loaches with some 190 members and it continues to grow with over 100 having been described since 1990. It may represent a polyphyletic lineage and is often arranged into a number of loosely-defined species ‘groups’, some of which are quite dissimilar to one another.

Among these are an assemblage in which some or all of the body bars are vertically split and another which exhibit reductions in body size (adult size <50 mm SL), the number of pelvic and pectoral-fin rays and often the number of caudal-fin rays and lateral line length, for example.

Some species, such as S. geisleri, also appear to be unrelated to any of the others.

Most inhabit flowing streams or areas close to waterfalls where there naturally exist high concentrations of dissolved oxygen, and a handful are troglobytic, i.e., cave-dwelling, in existence. The latter have reduced pigmentation and are completely blind in many cases.

Schistura spp. are distinguished from other nemacheilids by a combination of morphological characters which include: a moderately arched mouth which is 2-3.5 times wider than it is long; a median ‘interruption’ in the lower lip which does not form two lateral triangular pads and can vary from smooth to furrowed in texture; diverse colour pattern but usually dark with relatively regular bars; usually a black bar at the caudal-fin base which can be broken into two spots or smaller bars; one or two black markings along the base of the dorsal-fin; lack of acuminate scales on the caudal peduncle; caudal-fin shape variable from truncate to forked but usually emarginate; presence or absence of a median notch in the lower jaw; clear sexual dimorphism in some species.

The family Nemacheilidae is widely-distributed across most of Eurasia with the Indian subcontinent, Southeast Asia and China representing particular centres of species diversity.

References

1. Hamilton, F., 1822 - Edinburgh & London: i-vii + 1-405
   An account of the fishes found in the river Ganges and its branches.
2. Bănărescu, P. M. and T. T. Nalbant, 1995 - Travaux du Muséum d'Histoire Naturelle 'Grigore Antipa' 35: 429-495
   A generical classification of Nemacheilinae with description of two new genera (Teleostei: Cypriniformes: Cobitidae).
3. Conway, K. W., D. R. Edds, J. Shrestha and R. L. Mayden, 2011 - Journal of Fish Biology 79(7): 1746-1759
   A new species of gravel-dwelling loach (Ostariophysi: Nemacheilidae) from the Nepalese Himalayan foothills
4. Kottelat, M., 1990 - Verlag Dr. Friedrich Pfeil, München: 1-262
   Indochinese nemacheilines. A revision of nemacheiline loaches (Pisces: Cypriniformes) of Thailand, Burma, Laos, Cambodia and southern Viet Nam.
5. Kottelat, M., 2012 - Raffles Bulletin of Zoology Supplement 26: 1-199
   Conspectus cobitidum: an inventory of the loaches of the world (Teleostei: Cypriniformes: Cobitoidei).
6. 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).
7. 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.