The name ancistrus derives from the Greek 'agkistron' meaning hook - a reference to the form of the cheek odontodes. The genera Pristiancistrus, Thysanocara and Xenocara are now synonyms of Ancistrus.
Appearance and anatomy
Ancistrus species show all the typical features of the Loricariidae. This includes a body covered in bony plates and a ventral suckermouth. The feature most commonly associated with the genus are the fleshy tentacles found on the head in adult males; females may possess tentacles along the snout margin but they are smaller and they lack tentacles on the head. Tentacules, tentacles directly associated with odontodes, develop on the pectoral fin spine of the males of some species. Males also have evertible cheek odontodes which are less developed or absent in females. They also lack odontodes along the snout. In comparison with a typical pleco, a bristlenose is typically shorter (15 cm or less), more flattened and fatter with a comparatively wider head. Colouration is typically mottled brown, grey or black. Small white or yellow spots are common. Unlike other plecos which commonly grow to over a foot long, the bristlenose pleco may only grow to half the size, this makes it a suitable species of pleco for the smaller tank.
Distribution and habitat
The Ancistrus is one of the widest ranging genera of the family, and representatives are found throughout the range of Loricariidae. They are found throughout rivers and floodplain areas of the Amazon River in South America. There are also some species, A. cryptophthalmus and A. formoso, that live in caves.
The diet of this genus is typical for a Loricariid - algae and aufwuchs. Bristlenoses do not school but hide when not feeding, juveniles however are typically found in brightly lit shallows at the water margin making them susceptible to predation by birds.
Breeding takes place in hollows, caves and mud holes in banks. Males may clean the inside of the cavity with their suckermouth before allowing the female to approach and inspect the nest. Courtship includes expanding the dorsal and caudal fins and attempts by the male to escort the female to the nest. While the female inspects the nest, the male keeps close contact. The female may lay 20-200 adhesive eggs, usually to the ceiling of the cavity.
The female plays no role in parental care; the male takes care of its young. Males will clean the eggs and the cavity with its fins and mouth. Males inspect eggs to remove diseased or infertile eggs, and aerates the clutch by fanning them with its pectoral and pelvic fins. During this time, a male usually will not leave the cavity to feed, or will leave only occasionally and quickly return. The eggs hatch in 4–10 days over a period of 2–6 hours; the male guards the eggs for 7–10 days after hatching. The fry remain in the cave, attaching to the walls and ceiling with their mouths, absorbing their yolk sac in 2–4 days and becoming free swimming.
Males of these species are competitive and territorial. Males display to each other by positioning themselves parallel to each other, head to tail, with dorsal and caudal fins erect and cheek odontode spines everted. If this escalates to combat, the males will circle each other and direct attacks at the head. If an intruding male manages to evict another male from the nest, it may cannibalize the other male's young.
A male bristlenose may guard several clutches of eggs simultaneously. Females prefer males that are already protecting eggs and may prefer males that are protecting larvae; it has been suggested that the tentacles may act as a fry mimic to attract females, which would allow males without eggs in their nest to compete with males guarding eggs. Several clutches in various states of development from eggs to free-swimming larvae can be found in one nest.
In the aquarium
These fish are often kept by aquarists as they are dutiful algae-eaters and smaller in adult size than the common plecos usually seen in petshops. Size is up to 15 cm (male), 12 cm (female), recommended temperature 23-27 degrees Celsius, lifespan up to 12 years. They are hardy animals, tolerant to a wide range of water conditions, breeding easily in captivity, compatible with most other freshwater fish, though typically mottled brown in colour, other species are more exotic - spots of bright yellow on a dark background being a common patternation, albino variants are also common. The albino morph is not caused by exposure to light during development, it is a morph controlled by genetics.
Feeding is easy, bristlenoses will graze on algae and other surface growing organisms as well as eating algae wafers or tablets, flake food, squash, spinach, cucumber, zucchini, green beans and peas however they have been known to accept frozen bloodworms as part of their diet. Aquarium specimens may starve for lack of algae or other plant matter; algae wafers or other low-protein foods are recommended. Keepers should watch for the abdomen to take on a sunken appearance, indicating insufficient nutrition.
Like other plecs benefit from the addition of bogwood, which they will rasp at and use as a hiding place - in the absence of other plant matter (sources of fibre) wood may be essential to the survival of these fish in the aquarium as it helps digestion of typically high protein fish food.
Sexing is very easy as the female will occasionally have bristles around the edge of the chin and the male will have them up the center of the head
Breeding is also possible: Males attract females to small cave or hollow, then guard eggs after fertilization through hatching (4–8 days) until fry are free swimming (4–6 days after hatching); the aquarist need only supply a suitable cave, food, and one of each sex.
Caution should be taken with the spines (odontodes) - although the risk of personal injury is small with this genus the hooked nature of the odontodes means that a bristlenose may become trapped in non-natural material such as sponge filters and netting.
There are currently 64 recognized species in this genus:
- List of freshwater aquarium fish species
- Xenocara, a computer infrastructure in OpenBSD that was named after the genus of fish
- Froese, Rainer, and Daniel Pauly, eds. (2007). Species of Ancistrus in FishBase. May 2007 version.
- Armbruster, Jonathan W.. "Ancistrus (Kner, 1854)". http://www.auburn.edu/academic/science_math/res_area/loricariid/fish_key/Ancistrus/ancistrus.html.
- Sabaj, Mark H.; Armbruster, Jonathan W.; Page, Lawrence M. (1999). "Spawning in Ancistrus (Siluriformes: Loricariidae) with comments on the evolution of snout tentacles as a novel reproductive strategy: larval mimicry" (PDF). Ichthyol. Explor. Freshwaters 10 (3): 217–229. http://www.auburn.edu/academic/science_math/res_area/loricariid/fish_key/Ancistrus.pdf. Retrieved 2009-06-22.
- Trajano, Eleonora (2001). "Habitat and population data of troglobitic armored cave catfish, Ancistrus cryptophthalmus Reis, 1987, from central Brazil (Siluriformes: Loricariidae)" (PDF). Environmental Biology of Fishes 62: 195–200. doi:10.1023/A:1011884829498. http://www.springerlink.com/content/r74402qj14261353/fulltext.pdf.
- Satora, L. (1998). "Histological and ultrastructural study of the stomach of the air-breathing Ancistrus multispinnis (Siluriformes, Teleostei)" (PDF). Can. J. Zool. 76: 83–86. doi:10.1139/cjz-76-1-83. http://article.pubs.nrc-cnrc.gc.ca/ppv/RPViewDoc?_handler_=HandleInitialGet&journal=cjz&volume=76&calyLang=fra&articleFile=z97-167.pdf.
- Green, Douglas. [www.keepingandbreedingbristlenose.com "Mr."] (eBook). Aquatic ecology. Online. pp. 688. Archived from the original on 2010. www.keepingandbreedingbristlenose.com.
- Shane Linder. "An introduction to the bushy nose plecos of the genus Ancistrus". planetcatfish.com. http://www.planetcatfish.com/shanesworld/shanesworld.php?article_id=314.
- Froese, Rainer, and Daniel Pauly, eds. (2011). Species of Ancistrus in FishBase. December 2011 version.