Theoretical morphology of a cichlid according to the approach of Systemic Morphometry

Abstract

We analyzed the body structure of the Blackstripe Cichlid Vieja fenestrata (G\"unther, 1860), a species with highly phenotypic variability, by the Systemics Morphometrics Methodology, previously proposed by one of the authors. From this perspective and considering the properties of its bauplan, we describe the expected morphometrics variability of this species. The Infinitesimal Change Rates (IChR) were obtained deriving the allometric equations that relate pairs of morphometric variables, and they demonstrated that the species' growth is continuous throughout its ontogeny. For some of the morphometric variables, relative growth trajectories were traced and their relationship with the IChR showed. Also, the observed and theoretical Systemic Phenotypical Spaces (SPS) were described by using three dimensional graphs and Mahalanobis Quadratic Distances (MQD). This was an alternate approach that allowed the analysis of the phenotypical spaces' properties in a wider, more objective, and analytical manner. We conclude that the morphometric variability observed in V. fenestrata agrees with the variability expected in the times and places sampled, although there are still some issues to be explained. We propose to incorporate the structural variance into the classical phenotypic variance equation, and consider the equality: phenotypic variance = SPS theoretical, (the phenotypic variance is equal to the theoretical Systemic Phenotypic Space), as a point of convergence between Quantitative Genetics and Systemic Morphometry.