GRINDSTAFF, J.L.*; SMITH, H.G.; Lund University; Lund University: Intestinal parasitism during development affects morphology and ornamentation of ring-necked pheasants

Although it is generally assumed that effects of the developmental environment are transient and have little impact on adult phenotype, a growing number of studies have found persistent effects of developmental stress on adult morphology and physiology. Several studies have found long-term effects of early nutritional conditions on morphology, secondary sexual characters, and physiology. However, it is likely that other sources of developmental stress may also have long-term effects on offspring phenotype. In particular, exposure to parasites and other pathogens during early ontogeny may have profound effects on adult morphology. Ring-necked pheasants (Phasianus colchicus) naturally suffer from high levels of intestinal parasitism (in our population over 90% of birds have at least one worm). These intestinal parasites include the nematodes Heterakis gallinarum, Syngamus trachea, and capillary worms (Capillaria spp.). To assess the effects of parasitism during development on adult morphology and ornamentation, we reduced intestinal parasite levels in one-half of naturally infected pheasant chicks using the anthelminthic drug fenbendazole. Pheasants experimentally cleared of intestinal parasites exhibited significantly faster tarsus growth and body mass gain. These effects were particularly pronounced in males. Furthermore, growth of the tarsal spur, a secondary sexual ornament of male pheasants, was also significantly enhanced by the removal of intestinal parasites. As the pheasants mature, we also expect to find effects of the removal of parasites during development on wattle coloration and final body size. Developmental stress induced by intestinal parasitism may have long-term effects on pheasant morphology and ornamentation, thereby maintaining ornamentation as an honest signal of an individual�s developmental history and possibly genetically based parasite resistance.