Description and analysis of eggs shape variation in birds through morphometric and image processing techniques

• Grant number: 06/04805-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: November 01, 2006
• End date: July 31, 2007
• Field of knowledge: Biological Sciences - Zoology - Morphology of Recent Groups
• Principal Investigator: Erika Hingst-Zaher
• Grantee: Fábio de Andrade Machado
• Host Institution: Museu de Zoologia (MZ). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Some distinct methods for the determination and analysis of avian egg shape have been proposed by different authors in the literature. However, conceptual and methodological problems often results in underestimating shape variation described by the mathematical models applied, or generate variables with dubious homology, hindering not only the comparison among them, but also any conclusion of biological and evolutionary significance. In the present work I suggest the employment of morphometrics and image processing techniques for the analysis of egg shape, focusing in the extraction of the bidimensional outline followed by its description by a parametric curve c(t)=(x(t),y(t)). Such curve can be manipulated for noise filtering and normalization. For the quantification of egg shape, I intend to exploit multiscale curvature (and probably also analog measurements). By this I will obtain variables relative to the whole egg outline, free from size effects and homologous among different shapes. The avian egg is a complex structure, the eggshell being a biomineralized tissue with composition and shape driven by a genetic program. Through this methodology I intend to discriminate the egg shape of different groups of birds in distinct taxonomic levels, correlating it to biological factors, such as size of the adult, habits and clutch size.