Animal Diversity Web

Geographic Range

Nimbochromis linni is endemic to Lake Malawi, one of the great lakes of the central African Rift valley system. Most of the lake is bordered by Malawi to the west and south, a large section of the eastern shore is bound by Mozambique, and the northeastern corner lies in Tanzania. N. linni, though not common, has lakewide distribution.

(DeMason, 1995)

• Biogeographic Regions
• ethiopian
  • native

Habitat

N. linni is found exclusively in Lake Malawi, typically along areas of steep sediment-free rocky shoreline. Rocks in the lake vary in size from less than a half meter to several tens of meters. The rocks are invariably covered with algae, but the steepness of the shoreline prevents sediment from accumulating on the rock surfaces. Though the sediment-free rocky areas are their primary habitat, breeding N. linni is found in the intermediate habitat of Lake Malawi. These regions have both rocks and sand, and form a transition zone between areas of completely rocky shore and the sandy/muddy lake floor.

The lake itself, the ninth largest in the world, is approximately 600 km in length and up to 80 km wide. It has a maximum depth of 700 meters, but only the upper 200 meters have sufficient oxygen to support fish. The surface temperature of the lake averages between 23° and 28°C. The chemical composition of the lake is relatively uniform, its pH varying from 7.8 to 8.5 depending on the CO2 content of the water. CO2 content is lower and thus pH is higher in the sheltered bays along the shoreline. It is believed that the alternation of steep, rocky shoreline with gently sloping, sandy shoreline is one of the major contributing factors for the extraordinarily diverse speciation of cichlids found in these waters.

(Eccles and Trewavas, 1989; Konings, 1995)

• Habitat Regions
• tropical
• freshwater

• Aquatic Biomes
• lakes and ponds

• Range depth

  0 to 60 m

  0.00 to 196.85 ft

Physical Description

N. linni is a reasonably large cichlid. Though fry emerge as 1 cm, adults grow up to 30 cm in length. N. linni has a characteristic color pattern of large brown melanic blotches over a light colored background, as well brownish spots on the head and body and fins. It is very close in appearance to its sister species/clade N. polystigma, though it can be distinguished by a long downward protruding snout. This “broken-nosed” appearance is due to an elongated premaxillary pedicle. Unlike most other teleosts, cichlids like N. linni have only one nostril on each side of the snout. N. linni also displays the cichlid characteristic of interrupted lateral line. The lateral line runs from the back of the head rearward along the arched back of the fish. About two-thirds of the way to the tail, the line stops. The line is described as interrupted because just below the ending of the first line, a second lateral line starts and goes straight back to the base of the tail. The dorsal fin of N. linni has a spiny rays, but has a soft-rayed trailing edge. N. linni has one pair each of pectoral and pelvic fins, one anal fin and a homocercal caudal (tail) fin.

In breeding season, males acquire a dark blue color over their entire body with a red anal fin and bright yellow tips on the outer edge of the anal and dorsal fins. Females also lose their mottled appearance, but turn gray-brown in color rather than the brilliant blue of sexually active males.

(Barlow, 2000; Burgess and Axelrod, 1975; Eccles and Trewavas, 1989; Oliver, 1997)

• Other Physical Features
• bilateral symmetry

• Range length

  30 (high) cm

  11.81 (high) in

Development

N. linni, like almost all Malawian cichlids, are maternal mouthbrooders. That is, females carry their eggs in their mouth for protection after fertilization until the fry (juvenile fish) are ready for release. This mouthbrooding serves an important function for the development of the embryo. The mother will periodically “chew” or rotate the eggs within her buccal cavity. This allows all eggs access to oxygenated water flowing through the female’s mouth. Also, this tumbling prevents the yolk from settling on the germinal disc, which would kill developing embryo.

(Axelrod and Burgess, 1976; Barlow, 2000)

Reproduction

During the spawning period, males will defend a territory, typically a flat rock or sandy area surrounded by other rocks. Since the males are stationary, females seek out male territories when they are ready to spawn. As mentioned in the physical description section, males acquire breeding coloration of a distinctive blue, probably associated with territorial defense and mate attraction. As females approach, the spawning is initiated by courtship and display by the male. Courting males will carry their fins erect and energetically perform a lateral display. It is believed that this display helps females recognize males as potential mates, an important factor given that Lake Malawi contains over 700 species of various cichlids.

(Axelrod and Burgess, 1976; DeMason, 1995; Konings, 1995)

• Mating System
• polygynous

Though N. linni have a short breeding period every year, this period does not occur in the same months for all individuals. The breeding season depends on the sexual readiness of each individual, and can take place at any time during the year. Females will deposit their eggs on the rock or flat sandy area. The number of eggs is not well documented but generally cichlids of Lake Malawi rarely deposit more than 50 eggs, sometimes as few as 5. As soon as spawning takes place, the female will pick up the eggs in her mouth. The male will then present and quiver his anal fin and release his sperm. The female will then ingest the sperm and the eggs will be fertilized within the buccal cavity of her mouth. “Buccal” fertilization results in eggs that are exposed to the environment for a very brief period of time. This confers the obvious advantage of decreased vulnerability to the many hostile oophagous, or egg-robbing, cichlids in search of a quick and highly nutritious meal.

(Axelrod and Burgess, 1976; DeMason, 1995; Konings, 1995)

• Key Reproductive Features
• iteroparous
• year-round breeding
• sexual
• fertilization
  • external
• oviparous

• Breeding season

  varies among individuals

• Range number of offspring

  5 to 50

• Average time to hatching

  18-24 days

N. linni, like almost all Malawi cichlids, are maternal mouthbrooders, that is, only females care for eggs and fry. This may account for the female's more cryptic breeding coloration. Once fertilization has taken place, the female will move out of the male’s territory and incubate the eggs within her mouth for 18 – 24 days. After release of the fry, female N. linni will provide postnatal protection for their young for up to six weeks; the female will take the fry back into her mouth when danger is near and at night for shelter.

(Axelrod and Burgess, 1976; DeMason, 1995; Konings, 1995)

• Parental Investment
• female parental care

Behavior

N. linni is a solitary predator, like many of the larger piscivores.

• Key Behaviors
• natatorial
• motile
• solitary

Communication and Perception

In cichlids, communication takes place largely through body language, positioning of fins, flaring of opercles and color changes.

(Barlow, 2000)

• Communication Channels
• visual

• Perception Channels
• tactile
• chemical

Food Habits

N. linni is a piscivore (fisheater) and is unique among predatory cichlids in feeding habits. They typically eat young mbuna (various other cichlids endemic to Lake Malawi) that live and hide among the rocks near the lakeshore. Adults are too large to follow their prey into their crevice hideouts. Instead, they slowly swim in search of a specific place to feed, typically a crevice into which a small cichlid has approached or entered. They will stealthily approach the area and position their distinctive downward-protruding snout at the edge of the crack. N. linni will remain motionless for several minutes observing the mbuna prey, its mottled coloring helping to camouflage it. When the prey is in range of its protractile mouth, N. linni will expand its buccal cavity and open its jaws. The result is enormous negative pressure that sucks the “hapless” mbuna out of its shelter. Once the prey is captured, the pharyngeal jaws take over moving the prey down the gullet.

(Barlow, 2000; Konings, 1995)

• Primary Diet
• carnivore
  • piscivore

• Animal Foods
• fish

Predation

Other larger piscivorous cichlids may prey on N. linni, and certainly on their fry. They have no documented anti-predator adaptations.

(Axelrod and Burgess, 1976)

Economic Importance for Humans: Positive

N. linni is popular as an aquarium fish.

• Positive Impacts
• pet trade

Economic Importance for Humans: Negative

No known negative impact

Conservation Status

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

• CITES

  No special status

Other Comments

N. linni is named in honor of Dr. Wayne Linn, a United States Peace Corps Volunteer who worked with the Malawi Fisheries Department and was originally described under the genus Haplochromis.

(Eccles and Trewavas, 1989)

Contributors

William Fink (editor), University of Michigan-Ann Arbor.

Pier Sun Ho (author), University of Michigan-Ann Arbor.

References

Axelrod, H., W. Burgess. 1976. African Cichlids of Lake Malawi and Tanganyica (5th ed.). Neptune City, NJ: TFH Publications.

Barlow, G. 2000. The Cichlid Fishes: Nature's grand experiment in evolution. Cambridge, MA: Perseus Publishing.

Burgess, W., H. Axelrod. 1975. Haplochromis linni, a New Species of Cichlid From Lake Malawi. Tropical Fish Hobbyist, 23(5): 36-41.

DeMason, L. 1995. A Guide to the Tanzanian Cichlids of Lake Malwai. Ft. Myers, FL: National Art Publishing.

Eccles, D., E. Trewavas. 1989. Malawian Cichlid Fishes: the classification of some Haplochromine genera. West Germany: Lake Fish Movies.

Konings, A. 1995. Malawi Cichlids in their Natural Habitat (2nd ed.). Germany: Cichlid Press.

Oliver, M. 1997, 11 June 1998. "Are There Any Cladistic Analyses of Malwai Cichlids? (from unpublished Ph.D dissertation, Yale University, 1984)" (On-line). Accessed 19 October 2002 at http://malawicichlids.com/mw01007.htm.