Physical description
The wild-type of the species has 8-9 black vertical bars on a blue-grey body, along with a dark blotch on the operculum. Juvenile convict cichlids are monomorphic until they reach sexual maturity. Unusually for fish, the female is more highly coloured. She has more intense black bands across the body, and pink to orange colouration in the ventral region and on the dorsal fin. In contrast, the male is mostly gray with light black stripes along the body. On the other hand, male convict cichlids are larger than females, and they have more pointed ventral, dorsal and anal fins which often extend into filaments. In addition, older males frequently develop vestigial fatty lumps on their foreheads. The average standard length of breeding sized males in the wild ranged from 6.3-6.6 centimeters, while breeding sized females ranged from 4.2-5.5 centimeters. The maximum standard length has been reported to be 10 centimeters, with total length near 12 centimeters. Body weight has been reported to range from 34-36 grams (1.2-1.3 oz). Selective breeding has resulted in a leucistic strain of convict cichlids, in which the dark barring of the wild type is absent. These are also known as white convicts, pink convicts, gold convicts and A. nigrofasciata "Kongo", The leucistic colouration is caused by a mutation in an autosomal gene and is recessively inherited.
Diet
In natural habitats, the species feeds on crustaceans, small fish, insects, various worms, plants and algae. It has been demonstrated in laboratory studies that social status and associated stress can affect digestive function in convict cichlids.
Taxonomy and intraspecific variation
The species originally was described in 1867 by Albert Günther after having been collected in Central America by Frederick DuCane Godman and Osbert Salvin. In 2007, the species was moved from the genus Archocentrus to a new genus, Amatitlania based on a study of Archocentus species by Juan Schmitter-Soto. However, a 2008 study led by Oldrich Rican has suggested that all the species in Cryptoheros and Amatitlania, including Amatitlania nigrofasciata, should be moved into the genus Hypsophrys. A number of synonyms exist for this species including: Archocentrus nigrofasciatus, Cichlasoma nigrofasciatum, Cryptoheros nigrofasciatus and Heros nigrofasciatus.
The convict cichlid does display significant variation in colouration across its range in Central America. Some of these regional variants are now considered different species. In the cichlid-keeping hobby, one such fish Amatitlania siquia "Honduran Red Point" was collected from a stream in Honduras by Rusty Wessel. The Honduran Red Point Convict ranges from Atlantic Honduras south to Costa Rica. Other new species formerly included in A. nigrofasciata are:
- Amatitlania coatepeque, from Lake Coatepeque in El Salvador, and
- Amatitlania kanna, from the Atlantic side of Panama
The type species name, A. nigrofasciata, which used to cover all these species, has recently been restricted to the northern convict cichlid population ranging from El Salvador to Guatemala on the Pacific coast of Central America and from Honduras to Guatemala on the Atlantic coast.
The common name convict cichlid is, like the species name, derived from the vertical black stripes on the fishes body and their similarity to the striped prison uniforms of British convicts. Similarly, the species epithet nigrofasciatus literally means black-striped.
Distribution and habitat
Convict cichlids are endemic to the lakes and streams of Central America. In particular, the species occurs along the eastern coast of Central America from Guatemala to Costa Rica, and on the western coast from Honduras to Panama. Convict cichlids prefer moving water, and are most frequently found in habitats with cover in the form of rocks or sunken branches. Convict cichlids are relatively tolerant of cool water, an ability which has allowed the species to colonise volcanic lakes at elevations of 1500 m (4920 feet). At four natural habitats of the convict cichlid in Costa Rica, the pH was found to range from 6.6 - 7.8, while alkalinity ranged from 63 to 77 ppm CaCO3. The daily water temperature ranged from 26-29 °C (79-84 °F).
Feral populations
The species also occurs outside its natural range in Australia: in the warm effluent of power stations in Victoria, and in tropical Queensland. In addition to Australia, the species has been introduced to Réunion, Japan, Mexico, and the USA.
Reproduction
Like most cichlids, convicts exhibit parental care of both eggs and free-swimming fry. The species can reach sexual maturity as young as 16 weeks of age, though sexual maturity is more commonly reached by 6 months. Sexually mature convicts form monogamous pairs and spawn in caves or crevices. In the wild, the fish dig up caves by moving earth from underneath large stones. The eggs are laid on the upper or side surfaces of the cave and are adhesive.
After fertilization the eggs take approximately 72 hours to hatch. During that time, the parents expel intruders and potential egg predators from the territory around the nest. They also fan the eggs, moving water with their fins over the batch of eggs to bring oxygenated water to the eggs. They fan the eggs not only during the day but also at night, using their sense of smell to recognize the presence of the eggs in the dark, and keeping their pelvic fins in contact with the eggs to remain at the right distance for fanning. The parents also use their sense of smell to recognize each other at night, and also to detect and react to the presence of potential egg predators.
After hatching, a further 72 hours is required for the larvae to absorb their yolk sacs and develop their fins prior to becoming free-swimming fry. While in this free swimming stage, fry forage during daylight in a dense school and return to the cave or crevice before the night. Like other cichlids, the parents also retrieve their young just before night onset, sucking up three or four fry at a time into their mouth, swimming back to the nest, and spitting the young into it. The parents do this in anticipation of night arrival, using an internal time sense to know that night is approaching, as shown by laboratory experiments in which convict cichlids continued to retrieve even before nights that were not preceded by any signal such as dim light. During the night, the fry remain as a bunch at the bottom of the cave or nest, where they are fanned by the parents.
Both parents remain involved in guarding the fry from brood predators and engage in behaviors to assist feeding such as moving leaves or fin digging. Brood care of eggs, larvae and free-swimming juveniles in the wild can last 4-6 weeks, and occurs only once per season for the majority of females. In contrast, females in aquariums are known to breed many times per year with short intervals of 12-13 days between broods, as long as suitable rocks or similar surfaces are available for them to lay their eggs on. In captivity, breeding pairs of convict cichlids have been demonstrated to adopt similarly aged fry from other parents. In other cichlids it has been suggested this behavior may reduce predation on the fry belonging to the adoptive parents, through a dilution effect.
In the aquarium
Convict cichlids are easily maintained and bred in aquariums. The aquarium should be decorated to mimic the natural environment and should include rocks and artificial caves for breeding. The species is an unfussy omnivore and most types of prepared fish foods are readily accepted. The species will also consume aquarium plants. Convict cichlids are aggressively territorial during breeding and pairs are best kept alone in suitably sized aquariums. It has been suggested that brood care is reduced in aquarium strains. Due to the tendency of the species to dig, external filtration is recommended over undergravel filter systems. The relatively small size of this species, along with ease of keeping and breeding, make the convict an ideal cichlid for beginners and advanced aquarists alike interested in observing pair bonds and brood care in the aquarium.
