Adaptive Phenotopic Plasticity in the Midas Cichlid Fish Pharingeal Jaw

Adaptive phenotypic plasticity is being increasingly recognized as an important role in adaptive radiation. The plasticity leads to the production of phenotypes that are well suited for the ecological niches. The Midas cichlid fish, which are distributed in the Nicaraguan great lakes and several crater lakes, have been known for their intraspecific polymorphism, and phenotypic plasticity. The lower pharyngeal jaw of the Midas cichlid fish Amphilophus citrinellus was tested in different diets for its phenotypic plasticity. The study found that different diets induced changes on the lower pharyngeal jaw of the Midas cichlids fish, and that changes were due to the mechanical stimulations of the jaws, but not to nutritional composition. The result of jaw differentiation suggest that adaptive phenotypic plasticity of the Midas cichlid fish could be an important factor in its speciation.
Introduction Adaptive radiation generally refers to an event in which a lineage rapidly diversifies into the newly formed lineages evolving different adaptations (1). Several factors trigger adaptive radiation, for instances, the organisms evolve to exploit a new niches or resources, or specialization subdivide a single niche into many new niches by evolving to take advantage of different food (1). Some of known adaptive radiation are Darwin’s fitches(2), Honey creepers on the Hawaiian islands(3), and Cichlid fish in East African lakes(4). These examples show that specialization to certain diet is accompanied by morphological adaptations, and result in different shapes and sizes of species. Phenotypic plasticity is being recognized as an important role in adaptive radiation by relatively rapid change on species morphology (5). For example, the length of the hindlimbs of Anolis sagrei lizard were found that the individuals lived on broad surfaces developed longer hindlimbs for rapid locomotion, to capture prey, and escape predators, but the ones lived in narrow