Intrasexuelle Konflikte bei weiblichen Schneckencichliden Lamprologus ocellatus

Brandtmann G. Intrasexuelle Konflikte bei weiblichen Schneckencichliden Lamprologus ocellatus. Bielefeld (Germany): Bielefeld University; 2002.Paarungsmuster stellen den Ausgang eines Konfliktes dar. Ressourcenverteilung, Räuberdruck, Kosten und Nutzen des Gruppenlebens modulieren diese Systeme. Die Cichlidenart Lamprologus ocellatus aus dem Tanganyika-See ist in ihrer Fortpflanzung strikt an leere Schneckenhäuser gebunden, die als Eiablageplatz dienen und sowohl die Jungfische als auch die Adulten vor Fressfeinden schützen. Dominante Männchen können mehrere Schneckenhäuser monopolisieren und damit Weibchen in ihrem Territorium verteidigen (fakultative Polygynie). Weibchen versuchen ihrerseits, andere Weibchen von prospektiven Paarungssituationen fernzuhalten und sind auch gegeneinander aggressiv, wenn sie fest an Schneckenhäusern angesiedelt sind. Die vorliegende Arbeit kombiniert Freiland- und Laborbefunde und untersucht, welche Faktoren die Abstände zwischen Weibchen und damit das Paarungsmuster beeinflussen. Es wurden ökologische (Ressourcenverfügbarkeit, Räuberdruck) und soziale Faktoren (innerartliche Konflikte) untersucht

Female-female conflict in the harem of a snail cichlid (<i>Lamprologus ocellatus</i>): behavioural interactions and fitness consequences

Female intra-sexual competition plays an important role in the settlement process during pair or harem formation and in established harems of Lamprologus ocellatus , a small snail shell inhabiting cichlid from Lake Tanganyika. Larger females settle first and this could partly be due to male preference for larger females as shown in simultaneous choice tests but is also due to dominance of the larger female. Smaller females were unable to settle close to a larger one. Even when snail shells were not limiting the smaller was either unable to settle or had to settle at a considerable distance. This effect was independent of prior residence. Intense female-female aggression suggests that close settlement is disadvantageous to females. Genetic analyses of maternity using microsatellite length polymorphism at five loci showed a reproductive skew between females in a harem. Additionally, it proved brood mixing in aquaria as well as in the field. Brood mixing can be detrimental to female breeding success through interbrood cannibalism if size difference of juveniles amounts to 5 mm. Territoriality of juveniles, shown even between same-sized siblings, may cause indirect mortality through earlier dispersal of young. Females rejected experimentally added larger juveniles but accepted young smaller than their own fry. Acceptance of smaller juveniles could be advantageous through a dilution of predator attacks but it also appears to induce costs since females with young at the shell do not rear another brood. Large median distances of 91 cm maintained aggressively between breeding females in the field may serve to minimize the adverse effects of breeding in a harem

Female-female conflict in the harem of a snail cichlid (Lamprologus ocellatus): Behavioural interactions and fitness consequences

Brandtmann G, Scandura M, Trillmich F. Female-female conflict in the harem of a snail cichlid (Lamprologus ocellatus): Behavioural interactions and fitness consequences. BEHAVIOUR. 1999;136(9):1123-1144.Female intra-sexual competition plays an important role in the settlement process during pair or harem formation and in established harems of Lamprologus ocellatus, a small snail shell inhabiting cichlid from Lake Tanganyika. Larger females settle first and this could partly be due to male preference for larger females as shown in simultaneous choice tests but is also due to dominance of the larger female. Smaller females were unable to settle close to a larger one. Even when snail shells were not limiting the smaller was either unable to settle or had to settle at a considerable distance. This effect was independent of prior residence. Intense female-female aggression suggests that close settlement is disadvantageous to females. Genetic analyses of maternity using microsatellite length polymorphism at five loci showed a reproductive skew between females in a harem. Additionally, it proved brood mixing in aquaria as well as in the field. Brood mixing can be detrimental to female breeding success through interbrood cannibalism if size difference of juveniles amounts to greater than or equal to 5 mm. Territoriality of juveniles, shown even between same-sized siblings, may cause indirect mortality through earlier dispersal of young. Females rejected experimentally added larger juveniles but accepted young smaller than their own fry. Acceptance of smaller juveniles could be advantageous through a dilution of predator attacks but it also appears to induce costs since females with young at the shell do not rear another brood. Large median distances of 91 cm maintained aggressively between breeding females in the field may serve to minimize the adverse effects of breeding in a harem