Life Sciences Commons^™

'Eve' In Africa: Human Evolution Meets Molecular Biology, Robert D. Seager

Faculty Publications

Recent advances in the study of human origins have increased our understanding of our ancestors. There have been new, major fossil finds. WT 17000, a 2.5 million-year-old robust Australopithecus found in Kenya (Walker et al. 1986), led to a revision of early hominid phylogeny (Delson 1986; 1987). Existing fossil materials have been reassessed. For example, Tattersall (1986) maintains that at least two unrecog­- nized hominid species (Homo neanderthalensis, H. hei­ delbergensis and possibly H. steinheimensis ) existed be­ tween the times of H . erectus and fully modern H . sapiens.

Adaptive Coloration In Texas Fiddler Crabs (Uca), Carl L. Thurman

Faculty Publications

Five species of fiddler crabs occupy a variety of intertidal niches along the Texas coast. Each Uca is adapted to a specific array of physical factors in the environment. Some aspects of their adaptations are reflected by body color. Interspecific differences in morphological coloration are correlated with camouflage and substrate characteristics. Intraspecific color variation is expressed through neurosecretion-mediated physiological change in cellular pigment distribution. Adaptation to a dark or light colored background reveals different "secondary" chromomotor capabilities for each species. In addition, pigments in melanophores, leucophores and erythrophores exhibit circadian rhythms of dispersion and aggregation.

During a "primary" chromomotor response …