Cobitidae is the
family of the
true loaches, which are
Old World freshwater fish. They occur throughout
Eurasia and in
Morocco, and inhabit
riverine ecosystems. Today, most "
loaches" are placed in other families (see
below). But more than 100
species remain in the Cobitidae, while the number of
genera has almost doubled to nearly 30 in the past few years due to new discoveries and divisions of older genera. New species are being described regularly.
Description and ecology
The body forms of Cobitidae range from
vermiform –
worm-shaped, long and thin – to
fusiform –
spindle-shaped,
cylindrical and tapering toward the ends. Most true loaches do not have true
scales, and like many other
Cypriniformes or
catfishes, they have
barbels at their mouths (usually 3-6 pairs). Some other traits typically found in this family are a small bottom-facing mouth suited to their scavenging
benthic lifestyle, an erectile
spine below the eye, and a single row of
pharyngeal (throat)
teeth.
True loaches are mostly
scavengers and are omnivorous, usually not very picky about their food. They may eat aquatic
crustaceans,
insects and other small
invertebrates as well as scraps of organic
detritus. Many live in
eutrophic waters of generally poor quality and feed on
tubifex worms and similar
benthos associated with such habitat. Some of these loaches have adapted to low oxygen levels in warm, muddy rivers or dirty ponds by being able to gulp up
atmospheric oxygen from the air. Some species, particularly from the
genera Cobitis and especially
Misgurnus are sensitive to changing
air pressure. They change their behavior accordingly, and as these changes in activity are usually followed by a change in weather, they are commonly known as "weatherfishes" or "weather loaches".
Because of their scavenging nature and their ability to adapt to many freshwater ecosystems, some Cobitidae have been
introduced to foreign lands where they may pose problems to local wildlife as
invasive species. Other true loaches, many of them
migratory fish, have been seriously affected by
habitat destruction, chemical
pollution and
damming, and are considered
threatened species today. Some migratory species are popular
aquarium fish and since they are very hard to raise in captivity,
overfishing has seriously depleted once-common stocks in several cases.
Systematics
The other "
loaches" used to be included in this family, but nowadays are recognized as well-distinct members of the
order Cypriniformes. Together with the
suckers (Catostomidae), the "loaches" made up the
superfamily Cobitoidea. However, the
sucking loaches (Gyrinocheilidae) were easily recognizable as relatives of the suckers.
[Nelson (2006)]Eventually it was realized that the
hillstream loaches, though more similar to the true loaches than the other two presumed Cobitoidea, are nonetheless distinct enough to be better regarded a full-blown family Balitoridae. And as it seems the "sucking Cobitoidea" are quite distant indeed, perhaps even markedly closer to the
Cyprinidae, and thus the old superfamily
Catostomoidea warrants revalidation. Finally, the puzzling
mountain carps were most often considered a distinct family Psilorhynchidae in recent times. But in a number of systematic schemes, they were placed in the Balitoridae (or Balitorinae, when these were included in the Cobitidae). In fact, they seem to be loachlike
carps and belong in the
Cyprinidae.
[He et al. (2008)]The true loaches can be subdivided into two
subfamilies, the typically
fusiform Botiinae and the typically
vermiform Cobitinae:
- The Botiinae are the smaller subfamily, with 7 genera generally accepted today. Some of these are quite speciose however.
- The Cobitinae contain the remaining genera, but while a few make up the bulk of the remaining diversity of Cobitidae, many are very small or monotypic.
- * Pangio (formerly Acanthophthalmus)
Use by humans
Some true loaches are popular as
food fish in
East Asian countries such as
Japan. These are of importance in the
fisheries or being raised in
aquaculture. Small species may occasionally be caught for
bait.
As aquarium fish
Many of the more brightly-colored species, in particular
Botiinae, are popular with
freshwater aquarists and are therefore of importance in the
aquarium trade. The more colorful tropical species that are kept as pets are mainly
South Asian and
Southeast Asian
Botiinae. Cobitidae often encountered in aquarium trade include:
Cultural references
Loaches of some sort have been present in several
video games:
- Loaches also appear in the Nintendo DS game Animal Crossing: Wild World and its Wii sequel, Animal Crossing: City Folk. They are small fish found in rivers from March to May. Not rare, one specimen sells for a mere 300 bells (as much as a black bass); thus it is apparently not – as the player character wonders when catching one – a Hylian loach. The icon, though very restricted in resolution, is a correct depiction of a Cobitinae loach with a color pattern resembling some East Asian species of Cobitis.
Shakespeare's Henry IV, Part 1 Act 2 has:
"Why, they will allow us ne'er a jordan, and then we leak in your chimney; and your chamber-lie breeds fleas like a loach."
This might be a misprint, or an obsolete term for a
dovecote, then as today notorious for "breeding"
Ceratophyllus columbae fleas. Or it might indeed refer to the fish: the
Spined Loach (
Cobitis taenia), native to
England, is very prolific, and the phrase can be taken to imply "...hosts fleas as abundantly as the Spiny Loach spawns".
Footnotes
