Within the nominal species grouping suggested by Grant (2007) almost all B. rostrata sold in the hobby are B. sp. 'upper Brahmaputra' with B. rostrata sensu stricto rarely, if ever, available. Trade names include 'Gangetic loach', 'twin-banded loach' and 'ladder loach'.
The defining characters of the group are 'Pattern consisiting of 8-10 black to dark brown body bars that exhibit pale and numerous spots in juveniles, and in adults the bars can anastomose, sometimes completely obscuring the vertical bars on the anterior of the fish. Base colour whitish, or yellowish to gold, sometimes with greenish or bluish tinges.'
Anastomosis of the body pattern is typical in most Botia spp. and can cause problems with identification although members of the B. rostrata group are more likely to be confused with each other than congeners.
B. rostrata - Young specimens usually possess a dark bar under the eye, one on the opercle, another across the snout and 9-10, usually paired vertical bars on the body. These tend to anastomose more in the front portion of the body and in older examples the patterning is reminiscent of B. kubotai.
However that species usually only has 5 body bars and a less-vivid base body colour. The snout and lower fins of adults also tend to develop bright orange/golden colouration. There seem to be less brightly-coloured forms too which may be geographical variants, though none are common in the trade.
B. sp. 'upper Brahmaputra' - This form's appearance is highly variable but juvenile patterning usually consists of 3 dark bars on the head and 9-10 on the body, the latter usually placed in pairs.
The timing and extent of anastomosis of these differs wildly even between individuals of comparable age and size. For example some juvenile specimens can exhibit a total disintegration of the patterning at a young age (~5 cm2.0 in SL) while others retain the barring to a degree throughout life.
It can be told apart from B. rostrata sensu stricto by its less intense base body colour of beige, yellow or sand, often with a metallic gold/copper sheen, vs. usually yellow to golden with a greenish or blueish sheen. It's common in the trade and usually available as B. rostrata but sometimes B. geto, a name long-known to represent a junior synonym of B. dario, is used.
B. sp. 'ladder' - Very little is known about this fish but in images it appears to possess a distinctive adult body patterning of quite regularly-spaced dark body bars, each containing a vertical row of lighter spots.
The currently-recognised distribution of the genus Botia extends eastwards from the Indus River basin in Pakistan across northern India, then southwards through Myanmar as far as the Salween drainage (Ataran River). This range was previously much larger but modern studies have resulted in various changes to the taxonomy of both family and genus.
The latter is currently defined by the following combination of characters, as given by Kottelat (2004): mental lobe developed in a barbel; fronto-parietal fontanelle narrow; anterior chamber of gas bladder almost entirely covered by bony capsule, posterior chamber large or rather reduced; anterior process of premaxilla entire, not surrounding a cavity; rostral process rather long, with a more or less distinct ridge along inner edge; top of supraethmoid narrow or broad; optic foramen very small; suborbital spine not strongly curved backwards and bifid; head naked.
The family Botiidae has been widely considered a genetically distinct grouping since Nalbant (2002), having previously been considered a subfamily (Botiinae) of the family Cobitidae. Nalbant also moved some previous members of Botia into the new genus Yasuhikotakia based on a number of morphological characters.
Later Kottelat (2004) made further modifications to the taxonomy, raising Chromobotia for B. macracanthus and confirming that species previously included in the genus Hymenophysa should instead be referred to Syncrossus.
The former alteration was based on colour pattern plus some morphological characters and the latter because Hymenophysa not only represents a spelling mistake (McClelland's original spelling was Hymenphysa) but is a junior synonym of Botia.
More recently Kottelat (2012) erected the genus Ambastaia to accommodate A.nigrolineata and A. sidthimunki, two former members of both Botia and Yasuhikotakia.
As a result of these works the family Botiidae is thus divided into two tribes within which Botia appears to be the most basal lineage:
Tribe Leptobotiini - Leptobotia, Parabotia, Sinibotia.
Tribe Botiini - Ambastaia, Botia, Chromobotia, Syncrossus, Yasuhikotakia.
Phylogenetic studies by Tang et al. (2005) and Šlechtová et al. (2006) have largely confirmed this system to be correct although the latter disagreed with the placement of Sinibotia, finding it to be more closely related to the tribe Botiini.
Ambastaia nigrolineata and A. sidthimunki were found to be more closely-related to both Sinibotia and Syncrossus than Yasuhikotakia, despite being considered members of the latter at the time. Šlechtová et al. also proposed the use of subfamily names under the following system:
Subfamily Leptobotiinae - Leptobotia, Parabotia.
Subfamily Botiinae - Botia, Chromobotia, Sinibotia, Syncrossus, Yasuhikotakia.
Within these Botia appears to be the basal, i.e., most ancient, lineage and in a more-detailed phylogenetic analysis Šlechtová et al. (2007) confirmed the validity of the family Botiidae with the genera listed above as members rather then being grouped into subfamilies. This more recent, simpler system is the one we currently follow here on SF.
Some behavioural routines exhibited by Botia spp. have been recorded often enough that they've been assigned non-scientific terms for ease of reference.
For example during dominance battles (these occur most frequently when the fish have been introduced to a new tank, or new individuals added to an existing group) the protagonists normally lose much of their body patterning and colouration, a phenomenon that's come to be known as 'greying out'.
Such displays will sometimes also happen within an established group as individuals seek to improve social ranking but are usually nothing to worry about.
Interestingly some observations suggest that the character of the highest-ranked, or alpha, fish appears to affect that of the whole group though it must be said that scientific studies of botiid loach behaviour are virtually non-existent.
It certainly seems that they display a degree of 'personality' with some specimens being naturally bolder or more aggressive than others, for example. The alpha is normally the largest specimen within the group and often female.
'Shadowing' is an interesting behaviour in which younger individuals swim flank-to-flank with older, mimicking their every movement. Some keepers report that more than one smaller fish may shadow a larger simultaneously, with even three or four on each side!
The reason for it is unknown; it may relate to a group staying in touch with one another when rivers swell during times of flooding, perhaps reducing drag by swimming 'in formation' or having some other communicative function.
It's been observed in aquaria with both high and low water flow and seems to be habitual to the extent whereby some individuals will shadow other fishes if no conspecifics are present.
Sound also appears to be an important factor in communication since these loaches are able to produce audible clicking sounds, these increasing in volume when the fish are excited. The behavioural aspects of this phenomenon remain largely unstudied but the sounds are thought to be produced by grinding of the pharyngeal (throat) teeth or subocular spines.
A further curiosity is the so-called 'loachy dance' which involves an entire group swimming in a constant, restless fashion around the sides of the tank, usually utilising the full length and height.
The reasons for this are unknown and reports as to when it occurs vary but the most common triggers appear to be the addition of food, fresh water or new conspecifics, and it can last anything from a few minutes to a day or more.
Botiids also often settle at peculiar angles, wedged vertically or sideways between items of décor, or even lying flat on the substrate. This is no cause for alarm and appears to be a natural resting behaviour.
Botia spp. also possess sharp, motile, sub-ocular spines which are normally concealed within a pouch of skin but erected when an individual is stressed, e.g., if removed from the water. Care is therefore necessary as these can become entangled in aquarium nets and those of larger specimens can break human skin.
Botiids are also susceptible to a condition commonly referred to as 'skinny disease' and characterised by a loss of weight. This is especially common in newly-imported specimens and is thought to be caused by a species of the flagellate genus Spironucleus.
It's treatable although the recommended medication varies depending on country. Hobbyists in the UK tend to use the antibiotic Levamisole and those in the United States Fenbendazole (aka Panacur).
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