Shell morphology changes in the scallop Aequipecten tehuelchus during its life span: a geometric morphometric approach

Abstract

Shell morphology is a central feature of bivalve biology in fields such as taxonomy, evolution, and functional anatomy. When allometric shell growth occurs, traditional morphometric methods usually fail to provide robust, size-free shape variables. We used a more integrative approach, geometric morphometrics, to examine ontogenetic changes in the shell of the scallop Aequipecten tehuelchus. A single cohort that settled early in 2004 at a site in San José Gulf in northern Patagonia, Argentina, was sampled at irregular intervals over 5 yr. Different developmental stages had significant differences in shell shape. There was significant ontogenetic allometry, mainly reflected in the shape of the shell disc and the symmetry of the auricles. The most noticeable morphological changes in shell shape and size took place within the first 2 yr of life. Three different shell ecophenotypes were discriminated: spat, juveniles, and adults. Spat had a relatively large anterior auricle and a circular disc; auricles in juveniles were more symmetrical and the shell disc more elongated; and during the adult stage the auricles were small and asymmetrical and the disc elliptical. These 3 phenotypes may reflect changes in the scallop's life habits, as individuals develop from attached spat to actively swimming juveniles to more sedentary adults.

Does shell shape variation play a role in conservation of the long‐lived freshwater bivalve Diplodon chilensis (Bivalvia, Hyriidae)?

“…Despite the clear differences in life style between juveniles and adults regarding burial ability, feeding habits and food availability, D. chilensis shell shape remains constant over lifetime both in the river and in the lake population. In contrast, shell shape changes related to changing behavioural patterns throughout life have been reported for several species (Demayo, Cabacaba, & Torres, 2012;Guarneri et al, 2014;Márquez, Amoroso, Gowland Sainz, & Van der Molen, 2010).…”

“…Recently, geometric morphometric analysis has been increasingly employed in bivalve studies with different objectives: recognition of phenotypic fishery stocks (Márquez, Robledo, Escati Peñaloza, & Van der Molen, 2010;Palmer, Pons, & Linde, 2004;Rufino et al, 2012), paleoenvironmental and paleoclimate reconstruction (Aguirre, Perez, & Sirch, 2006;Aguirre, Richiano, Álvarez, & Farinati, 2016;Gordillo, Márquez, Cárdenas, & Zubimendia, 2011), and analysis of evolutionary processes (Schneider, Fürsich, Schulz-Mirbach, & Werner, 2010;Sherratt, Alejandrino, Kraemer, Serb, & Adams, 2016;Tang & Pantel, 2005). In addition, geometric morphometrics have been used to study ontogenetic shape changes (Márquez, Amoroso, Gowland Sainz, & Van der, 2010) and to evaluate the invasive success of introduced freshwater species (Sousa et al, 2007). Among geometric morphometrics techniques, landmarks together with semilandmarks have been successfully applied recently in bivalve studies (Leyva-Valencia et al, 2012;Morais et al, 2013).…”

Morphological and Molecular Differences Between the Invasive BivalveRuditapes philippinarum(Adams & Reeve, 1850) and the Native SpeciesRuditapes decussatus(Linnaeus, 1758) from the Northeastern Adriatic Sea

“…A number of studies deal with geometric morphometric analyses within species (Zelditch & Fink 1995, Rosas & Bastir 2002, M arquez et al 2010) and among species (Penin & Berge 2001, Rosenberg 2002 Kosnik et al 2006, Ampili & Shiny Sreedhar 2015 and to examine pattern of shell development (Roopnarine 2001, Tang & Pantel 2005. To facilitate the discrimination between Ruditapes philippinarum and Ruditapes decussatus, a non-invasive morphometric method based on the elliptic Fourier analyses of the external shell shape was recently suggested (Costa et al 2008(Costa et al , 2010.…”

Landmark-based geometric morphometric analysis of body shape variation within population of Ibis fish, Ambassis interrupta, collected from Masao River, Butuan City, Philippines

“…Overall and localized fluctuating asymmetries were determined by subjecting the paired landmark coordinates to Procrustes ANOVA following the method of Klingenberg (1998) and using the SAGE software version 1.0 [17]. Landmark-based geometric morphometric analysis was used to describe the body shape variation that exists among Ambassis interrupta fish samples from Masao River, Butuan City, Philippines.…”

“…The differences between population means, or the deviation an individual from its population mean are visualized in at least two ways by the landmark data. An alternative way to inspect the variability of landmark points in tangent space is to run a principal component analysis (PCA) on the tangent coordinates derived from Procrustes analysis [17]. The result of the Principal Component Analysis (PCA) is shown in Table III.…”