Genetic Basis of Parental Care in Cichlid Fish
In recent years, cichlid fish have been of particular interest to geneticists studying vertebrate speciation and behavioral patterns in new animal models. Cichlid fish are any of the more than three thousand species belonging to the family Cichlidae in the order Perciformes. As they are typically freshwater fish, cichlids are most commonly found within lakes in tropical America, southern Asia, and Africa. The species in the lakes of Africa, including Lake Victoria and Lake Malawai, are of particular interest to researchers due to their recent diversification and speciation over the past million years (Kocher 2). The nearly 2,000 species of ...view middle of the document...
In mouth-brooding, the eggs are taken up into one or another parent’s mouth and incubated for some period of time, typically in the range of two to three weeks. In biparental mouth-brooders, the eggs are periodically transferred between the male and female parents, although most mouth-brooders are uniparental female mouth-brooders (Sefc 2). While 95% of mouth-brooding genera are found in African lakes, approximately 70 percent of substrate-guarding genera are found in the Americas (Hilber 2).
Konrad Lorenz, among other prominent biologists, has cited experimental evidence for gene-behavior linkages. Experiments have shown that the basis of worker honey bees reacting to diseased or dead pupae are genetic, tracing one gene related to opening of the diseased cell containing the pupae and another to removal of the diseased pupa. Other gene-behavior links have been observed in behaviors such as aggression in honeybees, bird migratory patterns and nesting habits, and various cichlid behaviors (Saladin). Because of the clearly distinct differences between the two types of parental care in cichlid fish and the clearly separate evolutionary pathways between the two as a result of the different populations based on two different continents, the genetics of the parental care behaviors of cichlids have been of particular interest to behavioral geneticists. It has been suggested that linkage mapping and studies of gene expression could be applied to cichlids in order to gain an understanding of the genetic basis of these variations in behavior (Kocher 10). Due to their strengths as laboratory organisms and their interesting and distinct parental behaviors, cichlids are thus an excellent option for studying organismal diversity in behavior.
Cichlids are ideal laboratory organisms, as they adapt readily to captivity and are easy to obtain from pet shops and biological organism supply centers. Further, as they are one of the most common hobbyist aquarium fishes in the world, abundant resources are available for learning about the care and upkeep of an enormous myriad of cichlid fish species. Moreover, cichlids are primarily herbivores and occasionally detritivores. As a result of this, upon maturation, most will accept common fish flake foods found in typical pet stores (Kocher 5). In the lab, the generation time for cichlids is typically as short as six to nine months, making the fish a strong model for creating multiple generations in a timely manner. This short generation time thus makes the option of performing multiple crosses an option (Kocher 5).
For most maternal mouth-brooding cichlids like Cyprichromis leptosoma and Astatotilapia burtoni, the female is typically in the range of three to four inches long for fully mature adults. When fertile, she will release eggs into the water a few at a time before catching them in her mouth. At this time, after an elaborate series of mating rituals including choreographed movements and tail biting, the eggs are...
