This specie is relatively rare in the aquarium trade and much sought after by enthusiasts as a result.
It looks similar to its only congener A. sidthimunki but according to the original description by Kottelat and Chu (1987)[2] can be told apart by colour patterning which uniquely consists of a solid dark lateral stripe and another running along the dorsal mid-line.
A. sidthimunki differs by possessing two dorsal stripes anterior to the dorsal-fin and none behind, though in reality some specimens do have what could be described as a stripe posterior to the dorsal-fin which is usually broken by pale, saddle-like markings.
In adult A. sidthimunki there are numerous transverse, vertical bars connecting the two stripes and extending to the ventral surface; these may also be present in A. nigrolineata but are much less prominent and normally only extend the full distance between the stripes in the rear portion of the body.
The genus Ambastaia was erected by Kottelat (2012) to accommodate these two species which are former members of both Botia and Yasuhikotakia.
Members are currently diagnosed from other botiids solely on the basis of adult colour pattern and its ontogeny, the former comprising a whitish-yellowish background with a black midlateral stripe on each flank and an additional, middorsal stripe, with vertical bars connecting these two stripes and extending onto the lower portion of the body.
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.
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 Ambastaia 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.
Ambastaia 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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