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The terms shell dwellers or shelldwellers, shell-breeding, or ostracophil are descriptive terms for cichlid fish that use the empty shells of aquatic snails as sites for breeding and shelter. The terms have no taxonomic basis, although most shell-dwelling cichlids are from Lake Tanganyikas lamprologine lineage. [1] Many shell dwelling cichlids are popular with fishkeepings and are frequently kept in aquaria. [1]
In Lake Tanganyika the shells inhabited are from the genus Neothauma , [1] while shells used by Pseudotropheus lanisticola in Lake Malawi are from genus Lanistes . [2]
Around 24 species of lamprologine cichlids use abandoned shells for shelter and breeding in Lake Tanganyika. Most, however, are not obligate shell-breeding cichlids and will spawn in other caves or crevices. [1]
There are several groups the shell dwellers can be placed into:
Shell dwellers are found throughout Lake Tanganyika, along the coasts of Zambia, Democratic Republic of Congo, Burundi and Tanzania.
Shell dwellers are carnivores that primarily feed on zooplankton and other microscopic and near-microscopic foods.
Cichlids' distinctive pharyngeal teeth, in the throat of the fish, are present in shell dwellers, though small. Armed with those and the usual teeth along with the typical dissolving qualities of water shell dwellers can eat a variety of foods in the wild and in captivity. Many species have been known to pull small snails from their shells to eat, to catch and devour the fry of other fish, and to go after small crustaceans.
As with other cichlids they protect their young, and the distinctive shell-dwelling provides them with a defensible nursery.
Generally eggs are laid by the female within the shell and fertilized as she lays them or immediately after by the male.
The female will protect the shell, fanning her pectoral fins to keep the internal water oxygenated, and often rearranging the substrate to create barriers or to hide the shell from predators.
Eggs hatch within 48 hours, dependent primarily on temperature, and the yolk sac is absorbed within five days. Fry typically emerge from the shell a week after spawning, although they remain quite benthic for days or weeks after their emergence.
The Malawi shell dweller, Pseudotropheus lanisticola , was first identified in 1964 along with many other mbuna in that lake, but the Tanganyikan shell dwellers were found primarily in the late 1970s and early 1980s. Altolamprologus compressiceps was identified in 1958 but the shell-dwelling varieties were found much later.
The shell-dwelling species' needs are very similar. The basic aquarium setup and equipment are appropriate with a few changes. First, the substrate should be sand. Many of the species are very accomplished diggers and for security may bury all or part of a shell, use sand as a territorial barrier, or generally amuse the owner by spitting, sifting, or throwing it. Second, hard, alkaline water must be provided, which should also be kept free of ammonia and nitrites and with low nitrates. Finally, appropriate shells must be provided. Common shells used for shell dwellers include authentic Neothauma shells, ocean turbo shells, escargot shells, whale eye shells, and Ampullariidae-family shells. Shells must be of an appropriate size for the species, have a round opening, and have open coils. Numbers of shells will vary; for colonial species, hundreds may be ideal. For brevis types, a single shell per pair is often representative.
Mbuna is the common name for a large group of African cichlids from Lake Malawi, and are members of the haplochromine family. The name mbuna means "rockfish" in the language of the Tonga people of Malawi. As the name implies, most mbuna are cichlids that live among the piles of rocks and along the rocky shores of Lake Malawi, as opposed to the utaka, cichlids that live in the open water or on sandy shores or soft substrates. Some species of mbuna are highly sexually dimorphic, although many are not. Among biologists, almost all of the cichlid species of Lake Malawi, including mbuna and non mbuna such as the utaka, are believed to have descended from one or a very few species that became isolated in the lake. With rising water levels, new habitats could be colonized and the many isolated rocky outcrops allowed new mbuna species to form. Their striking colors, intriguing behavioral characteristics, and relative hardiness make them very popular despite their unique demands for the home aquarist.
Maylandia estherae is a haplochromine cichlid. It is a rock dwelling fish or mbuna from Lake Malawi. This fish, like most cichlids from Lake Malawi, is a mouthbrooder - females hold their fertilized eggs then fry in their mouths until they are released after about 21 days.
Pseudotropheus is a genus of fishes in the family Cichlidae. These mbuna cichlids are endemic to Lake Malawi in Eastern Africa.
Neolamprologus brichardi is a species of cichlid endemic to the alkaline waters of Lake Tanganyika in East Africa. It is a popular aquarium fish kept in the fishkeeping hobby, where it is known under a variety of common names including Princess cichlid, Princess of Burundi, Lyretail cichlid, Fairy cichlid and Brichard's lamprologus. In addition, the species is also the subject of numerous studies on fish behaviour. It is closely related to N. pulcher from the southern half of Lake Tanganyika and some have recommended merging the two into a single species.
Maylandia or Metriaclima is a genus of haplochromine cichlids endemic to Lake Malawi in East Africa. They belong to the mbuna (rock-dwelling) haplochromines.
Neolamprologus similis is a shell-dwelling cichlid endemic to Lake Tanganyika where it is only known along the shores of the Democratic Republic of the Congo and Tanzania. N. similis is copper coloured with vertical white stripes running from the head to near the base of the tail. It can reach up to 5 centimetres (2.0 in) in total length. It is a popular freshwater aquarium fish.
Lamprologus is a genus of fishes from the cichlid family. They are native to Lake Tanganyika and the Congo River Basin in Africa. The type species for this genus is Lamprologus congoensis, a species from the Congo River. The genus is under some revision and may eventually be restricted to these riverine types.
Altolamprologus is a small genus of pseudocrenilabrine cichlids endemic to Lake Tanganyika in eastern Africa. They inhabit areas of the lake with large amounts of rock, most frequently in water two to ten metres in depth. Two formally described species comprise this genus, with perhaps one dwarf A. compressiceps-like species being considered an unedescribed species by some.
Neolamprologus is a genus of cichlids endemic to eastern Africa with all but one species, Neolamprologus devosi from the Malagarasi River, occurring in Lake Tanganyika. It is the largest genus of cichlids in Lake Tanganyika and also the largest genus in the tribe Lamprologini, which includes Altolamprologus, Chalinochromis, Julidochromis, Lamprologus, Lepidiolamprologus, Telmatochromis and Variabilichromis. The latter is a monotypic genus doubtfully distinct from Neolamprologus.
Lamprologus ocellatus is a species of shell dwelling cichlid endemic to Lake Tanganyika. It is a popular aquarium fish due to its small size, appearance, and intelligence.
The haplochromine cichlids are a tribe of cichlids in subfamily Pseudocrenilabrinae called Haplochromini. This group includes the type genus (Haplochromis) plus a number of closely related genera such as Aulonocara, Astatotilapia, and Chilotilapia. They are endemic to eastern, southern and northern Africa, except for Astatotilapia flaviijosephi in the Middle East. A common name in a scientific context is East African cichlids – while they are not restricted to that region, they are the dominant Cichlidae there. This tribe was extensively studied by Ethelwynn Trewavas, who made major reviews in 1935 and 1989, at the beginning and at the end of her career in ichthyology. Even today, numerous new species are being described each year.
Pseudotropheus crabro, the Bumblebee Cichlid or Hornet Cichlid, is a species of cichlid endemic to Lake Malawi where it is found in different habitats but most frequently in large caves or in the vicinity of large boulders. This species can reach a length of 16 centimetres (6.3 in) SL.
Neolamprologus multifasciatus is one of the small shell-dwelling cichlids endemic to Lake Tanganyika. The male reaches 5 cm (2 in) in length, and the female only 2.5 cm (1 in) in the aquarium. In the wild, they reach only 3 centimetres (1.2 in) in standard length of male and female reaches less than 2.2 centimetres (0.87 in) in standard length. This makes them one of the smallest cichlid species in the world. Its natural habitat is the Neothauma shell beds of Lake Tanganyika, where it forms huge colonies with thousands of individuals. Their unique behavior is associated with their affinity to shells. They burrow sand to move shells, take refuge in shells and also breed in them. They have pale white coloring with black vertical bars running the length of their bodies. The species is sexually monomorphic, meaning sexing individuals is extremely hard or impossible based on external appearance alone.
Pseudotropheus johannii or the bluegray mbuna is an African freshwater fish from the family Cichlidae.
Malawi eyebiter is a species of fish in the family Cichlidae. This predatory cichlid is endemic to Lake Malawi in East Africa.
Lamprologus signatus is a species of cichlid endemic to Lake Tanganyika where it prefers deep waters over muddy substrates. This species is a shell dweller. This species can reach a length of 5.5 centimetres (2.2 in) TL. It can also be found in the aquarium trade.
Neolamprologus fasciatus is a species of cichlid endemic to Lake Tanganyika. This species spawns in empty snail shells. This species can reach a length of 15 centimetres (5.9 in) TL. This species can also be found in the aquarium trade. They are piscivores and their prey includes the cichlid fish Variabilichromis moorii.
Utaka is the term used for open water-dwelling cichlids found in Lake Malawi, the most diverse source of cichlids in the world of aquaria. Among others, they comprise all the members of the genera Copadichromis and Mchenga.
Pseudotropheus sp. "acei" is a Mbuna cichlid from Lake Malawi that grows to around 7 in (18 cm) in length. Although known for many years, it has not been formally described. There are two different varieties: The most common yellow-tailed Pseudotropheus sp. "acei" (Msuli), and the white-tailed Pseudotropheus sp. "acei" (Ngara). Like most Mbuna, it dwells in shallower waters, however it will sometimes go near the surface, which is very uncommon for Mbunas. It is a very common fish for fish-keepers. It gets its common name from its blue body and yellow tail. Originally discovered in 1922 by Regan, the acei was originally believe to be a Pseudotropheus, but was later changed to Gephyrochromis and then back again. It prefers the sandy and rock filled shoreline where sunken logs are easily accessed. This species has developed the advantage of being able to harvest algae from submerged logs and roots. They are equipped with typical Gephyrochromid cuspid-like teeth that are flat for removing epixlyic or epilithic algae from wood. In the lake, schools of 30-50 individuals surrounding a large log are not uncommon, however in the rocky areas; schools usually consist of 3-10 individuals.
Lamprologini is a tribe of African cichlid fishes. It contains seven genera and nearly 100 species. Over half of the species in this tribe are in the large genus Neolamprologus. Most genera in the tribe are endemic to Lake Tanganyika, but one species of Neolamprologus is from the Malagarasi River in Tanzania, and several species of Lamprologus are from the Congo River Basin.