Perissodus microlepis Breeding Guide

How to breed the scale-eating Perissodus microlepis, a Lake Tanganyika cichlid with an asymmetric mouth and socially monogamous biparental mouthbrooding.

Overview

Perissodus microlepis is a specialised scale-eating cichlid endemic to Lake Tanganyika, reaching about 11 cm in total length and inhabiting the shallow rocky shore. It is a textbook example of lateral asymmetry: the population contains two morphs, one with mouthparts twisted to the left that eats scales from the right flank of prey, the other a mirror image; the relative abundance of the two morphs is regulated by frequency-dependent selection. For breeding, it is socially monogamous with biparental care.

Conditioning

In the wild this species feeds by tearing scales from other fish, so it is a difficult specialist for the aquarium and is best regarded as a curiosity for advanced keepers. Conditioning a pair requires a diet that satisfies its carnivorous, scale-eating biology, which is one reason it is rarely bred deliberately.

Breeding Setup

A pair needs the hard, alkaline conditions of Lake Tanganyika and the shallow rocky habitat the species occupies in the wild. Because the species is problematic with most tankmates owing to its scale-eating habit, a settled monogamous pair on its own is the realistic breeding unit.

Spawning Behavior & Trigger

The species is socially monogamous, but genetic studies of wild broods reveal that the mating system is in fact polygamous, with both extra-pair paternity and extra-pair maternity documented. Females mouthbrood the eggs and early larvae for about 9 to 11 days, after which the brood becomes free-swimming.

Egg & Fry Care

After the maternal mouthbrooding phase of roughly 9-11 days, both parents guard the free-swimming juveniles together on the substrate for several weeks. Field studies record extensive brood mixing, with the proportion of unrelated juveniles in a brood ranging from 5 to 57 percent (mean about 28 percent), and parents, particularly males, farming out offspring to other pairs; the data best support the selfish shepherd effect, in which foster parents preferentially accept smaller unrelated young.

Common Challenges

The chief obstacle is the species' scale-eating diet, which makes it incompatible with most tankmates, especially long-finned and small fish, and difficult to feed appropriately. Its specialised biology and the rarity of deliberate captive spawning mean breeding is an advanced undertaking rather than a routine project.