An Overview of Interlocation Sexual Shape Dimorphism in Caquetaia kraussi (Perciformes: Cichlidae): A Geometric Morphometric Approach

Abstract

C. kraussii is an endemic fish species from Colombia and Venezuela and represents a valuable food resource for local human communities. Due to its economic importance, the management and captive breeding of this species are of special interest. However, the anatomical similarities between sexes have been a problem for visual identification. It is also important to indicate that C. kraussii has cryptic morphological behavior between sexes, a topic that has been one of the main problems for the implementation of management plans. The following research studied individuals from three different localities along the Canal del Dique, Bolívar Department in Colombia, in which the body shape of C. kraussii was analyzed using geometric morphometric analysis. The analyses detected the presence of intralocality sexual dimorphism in two of the three localities analyzed, showing a low morphological variability among males, presenting conserved body shape, as well as a greater morphological disparity among females. This sexual shape dimorphism may be associated with the environmental variation among different locations. These results suggest the presence of two evolutionary forces acting asymmetrically between the sexes of C. kraussii, with males mostly subject to sexual selection pressure, while females are mainly subject to environmental pressures.

Ecomorphology and Morphological Disparity of Caquetaia Kraussii (Perciformes: Cichlidae) in Colombia

“…The PLS analysis indicated that about 90% of the variation in body shape explained by PC1 was not due to the environmental variables measured. This agrees with the results of Hernández et al, 2022, which show marked sexual dimorphism, suggesting that the body shape of males of C. kraussii is more conserved, submitted mostly to sexual selection pressures, while the body shape of females appears to be affected by environmental pressures, from which it may be inferred that most body shape variation is subject to sexual selection [ 39 ]. By contrast, PC2 and PC3, which together explained about 10% of the body shape variation, are mostly (≈90%) determined by the dissolved oxygen and the T°-pH combination, respectively.…”

“…Photographs were taken with a high-resolution FUJIFILM X-T2 24-megapíxel camera; TPS programs was used to transform the photos to TIF format [ 46 ]. Fifteen landmarks were digitized using Hernandez et al [ 39 ]’s landmark map for Caquetaia kraussii ; they are illustrated in Figure 2 . The landmarks were digitalized and transformed to two-dimensional coordinates using the software tpsDig2 [ 47 ].…”

“… Graphical representation of C. kraussii showing the locations of 15 landmarks following Hernandez et al [ 39 ]. …”

“…It lives in a variety of habitats, from lotic areas such as the middle and lower parts of the Sinú, Cauca, Magdalena, San Jorge, Cesar, and Arauca Colombian Rivers, and lentic habitats such as freshwater or low salinity marsh with submerged vegetation [ 37 , 38 ]. Regarding morphological information on the species, the presence of sexual dimorphism between different localities along the “Canal del Dique” (Colombia) has recently been described, which could be associated with environmental variation [ 39 ]. Therefore, the objective of this study is to quantify the phenotypic variation in C. kraussii using advanced morphological tools that quantify shape in different populations of C. kraussii in the “Canal del Dique”, Colombia, and to evaluate associations between different ecological parameters of the study sites and the morphological differentiation of its populations.…”

On a remarkable sexual dimorphic trait on scales and fins of the old world Cyprinodontiformes (Actinopterygii: Aphaniidae)

“…Understanding and classifying the complexity of fish diversity and other organisms have historically been on the basis of comparative morpho‐anatomical characteristics. Part of this diversity may be established by natural and/or sexual selection (Hernandez et al, 2022). Based on the sexual selection theory, selection provides reproduction advantages to individuals of the same species and sex and affects the success of differential mating (Andersson, 1994; Hernandez et al, 2022; Lima‐Filho et al, 2017; Rodríguez et al, 2005).…”