The long term goal of this research is to understand the nature of the developmental genetic differences that make all individuals of a species unique, and distinguish the various species from one another. Towards this end, differences between two types of fishes that are closely related, but genetically distinct, will be studied. The Mexican tetra, Astyanax mexicanus, has some populations that live in rivers and others that live in caves. Cave forms differ from their surface relatives by having greatly reduced eyes and pigmentation. The caves in which they live provide little food and they have adapted to this by developing a slower metabolism. Other senses are overdeveloped to compensate for the lack of vision: e.g., smell, taste and the ability to detect vibration and current. Not only can they survive eternal darkness, they thrive in caves.
The genome of this species will be mapped at a fine scale using microsatellite DNA markers, in hybrids between the cave and surface forms. The map and further analysis of the hybrids will permit the detection and characterization of genes (QTL) that are responsible for the differences between cave and surface forms. The results will give estimates of the "genetic architecture" of trait differences: the number of genes involved and magnitudes of their individual effects, and their positions in the genome relative to one another. Positional information of some of the major effect QTL will be used to identify and clone the genes; this will facilitate their functional analysis. The results will shed light on the genetic pathways involved in development and maintenance of complex traits, like the vertebrate eye and other aspects of the sensory system, control of pigmentation, behavior and metabolism. The results will also inform on the nature of genetic differences distinguishing populations and species, and on the constraints on evolutionary change resulting from trait correlations.
