Reproductive biology

Embiotocids are viviparous (give birth to live young), and males have a thickened anterior portion of the anal fin that aids in internal fertilization. They display elaborate courtship behaviors, reminiscent of a small cross-section of the varied courtship behaviors found in cichlids. Some cichlids, for example, members of the genera Crenicara, Sarotherodon, and Etroplus, are capable of changing sex. When a group of females finds themselves without access to a male, the dominant female is able to generate testicular tissue sufficient to fertilize the eggs of the remaining females.

Primitively, cichlids likely formed monogamous pairs, in which both parents guarded eggs laid on the substrate. Cich-lids exhibiting this behavior include the Indian etroplines, most Central American taxa, many South American taxa (such as Pterophyllum and Symphysodon), as well as several African groups (including Hemichromis and the lamprologines). Some cichlids have evolved polygamy and mouth brooding as embellishments of the original reproductive mode. Mouth brooders allow the eggs and young to develop inside the safety of the buccal cavity of one or both parents. As the young mature, they make feeding excursions outside, but quickly retreat into the adult's mouth at the first sign of danger. It is fascinating that following egg deposition, females of some mouth-brooding species collect the eggs into their mouths with such alacrity that males do not have time to fertilize them externally. On the anal fin of many such males, however, are conspicuously colored spots, called egg dummies, which bear a remarkable resemblance to the actual eggs. The female notices these spots and nips at them (in an apparent attempt to collect them into her mouth, some have argued), and the male releases sperm at the same time. Thus the eggs are fertilized inside the mouth of the female.

In one instance, a noncichlid has devised a means of capitalizing on the mouth-brooding habit of cichlids at their expense. Synodontis multipunctatus, a mochokid catfish, is a brood parasite on several species of mouth-brooding cichlids in Lake Tanganyika. Catfish eggs are concealed among the cichlid eggs during spawning, and are then taken into the mouth of the adult cichlid. As development proceeds, the young cat-fishes devour the cichlid fry from the safety of the parental

Cichlid Egg

Cross-section of a female Oreochromis mouth-brooder. (Illustration by Michelle Meneghini)

buccal cavity, so that ultimately the cichlid parents find themselves caring for a small brood of catfish and none of their own progeny!

Many cichlids expend enormous energy in altering their surroundings prior to reproduction. Elaborate sand nests, in the form of pits or cone-shaped mounds, are constructed by the males of some cichlid species for spawning. Some nest mounds are enormous, and require many days work by the male, moving sand one mouthful at a time. In certain species, lekking occurs: males build their nests in aggregations of various sizes. In Lake Malawi, male Copadichromis eucinostomus come together in groups as large as 50,000 individuals, stretched over several miles of sand, each guarding a cone-shaped nest. In Lake Tanganyika, numerous species from the tribe Lamprologini take advantage of abundant snail shells on the lake bottom as places of refuge and spawning sites. Neo-lamprologus callipterus, a haremic species, is noteworthy in that the males are dramatically larger than the females (as much

Female Biology

Some catfish eggs have evolved to look like cichlid eggs, so when a female cichlid (Tropheus moorii) collects her own eggs in her mouth, she inadvertantly collects some catfish eggs and raises them too. When the catfish eggs hatch, the young catfish eat the cichlid eggs. (Illustration by Michelle Meneghini)

Some catfish eggs have evolved to look like cichlid eggs, so when a female cichlid (Tropheus moorii) collects her own eggs in her mouth, she inadvertantly collects some catfish eggs and raises them too. When the catfish eggs hatch, the young catfish eat the cichlid eggs. (Illustration by Michelle Meneghini)

Mouth Brooders Reproduction

Male rift lake cichlids have spots on their anal fins. When a female swims around collecting her eggs in her mouth after releasing them to be fertilized (1), she often mistakes the spots on the male's fin to be eggs. She bites the anal fin (2), and the eggs in her mouth are then fertilized. (Illustration by John Megahan)

Male rift lake cichlids have spots on their anal fins. When a female swims around collecting her eggs in her mouth after releasing them to be fertilized (1), she often mistakes the spots on the male's fin to be eggs. She bites the anal fin (2), and the eggs in her mouth are then fertilized. (Illustration by John Megahan)

30 times by weight), and only females occupy shells during spawning. Selection seems to maintain this size dimorphism because males need to be large enough to carry shells to their territories, while females need to be small enough to spawn inside the shells.

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