Tropheus moorii (blunthead cichlid) is a species of cichlid endemic to Lake Tanganyika in Africa. Over 40 different color morphs of this species are dispersed throughout the lake, ranging from dark green to flame red and yellow. They mostly feed on filamentous algae on the rocky shallows they inhabit. T. moorii is a maternal mouthbrooder, so eggs are fertilized and young are carried in the mouth of the female while they hatch and develop.
Territorialism
Both male and female adults occupy individual feeding territories. Blunthead cichlids inhabiting territories at greater depth tend to have smaller adult body sizes and larger territories compared to those in shallows. Males have larger territories than females. A female leaves her territory to pair with a male and usually visits several territories multiple times before choosing a male. After the male and female form a pair bond, the female forages in his territory up to three weeks under his protection before spawning. A female's ovaries do not fully mature until she pairs with a male and feeds from his territory. After spawning, the female leaves the male's territory to occupy a small unclaimed area for the mouthbrooding period. In contrast to the frequent movement of females, a male usually remains in his territory for months even if he is never visited by females.
Interspecies interactions
Often, blunthead cichlid feeding territories are adjacent to territories of conspecific and heterospecific neighbors. A male T. moorii usually courts a female conspecific, which visits his feeding territory.
In Lake Tanganyika, blunthead cichlids coexist with other herbivorous cichlids P. trewavasae, P. orthognathus, P. polyodon, and T. temporalis. T. moorii, P. polyodon, and T. temporalis individuals are not aggressive towards one another, but are aggressive towards individuals of other species and conspecifics. Although their territories often overlap, individuals of the three species do not usually interact due to the dietary differences that exist. For example, P. polyodon and P. trewavasae mostly feed on unicellular algae rather than filamentous algae.
Having overlapping territories with P. polyodon may benefit T. moorii individuals since P. polyodon removes silt from the rock surface as they feed. This allows T. moorii to easily scrape filamentous algae from the rocks. Having overlapping territories with P. trewavasae may benefit T. moorii individuals because both defend their territory from much larger P. orthognathus individuals. They also are able to drive them away, whereas an individual blunthead cichlid may not be able to defend territory successfully. This is an example of commensalism rather than mutualism because individuals would defend their territories regardless.
Size-dependent dominance hierarchies
T. moorii participates in size-dependent dominance hierarchies when defending territory from intruders. If an individual intrudes on a T. moorii territory, the interaction may be a one-sided (territory owner towards the intruder) attack, one-sided display (spread and quiver fins/tail to intimidate), mutual attack, or mutual displays. These usually occur at or near the borders of the territories. In a one-sided attack, the territory owner chases the intruder until it leaves the territory.
Interactions vary depending on the relative size of the territory owner and intruder. Individuals tend to perform one-sided attacks on neighbors smaller than them and perform one-sided displays towards those larger than them. Attacks may occur inside or outside the feeding territory of the territory owner, while displays usually take place within the territory. Displays are very rare when a large difference in body size (more than 2.5 cm)exists, and more common when the difference is smaller (less than 2 cm). Mutual attacks are very likely to occur when the individuals are of similar size. Neighbors (having an adjacent territory) are more likely to respond to an attack with a display compared to a non-neighbor. In observed interactions between specifically P. orthognathus and T. moorii individuals with adjacent territories, the larger fish attacked the smaller one regardless of species, and no displays occurred.