Application of Shape Analyses to Recording Structures of Marine Organisms for Stock Discrimination and Taxonomic Purposes

Abstract

Morphometric analysis of biogenic recording structures within marine organisms has applications in stock assessment, taxonomics, and ecomorphological studies, with shape variation markedly influenced by both genetics and the surrounding environment. Geometric morphometrics (GM) is an alternative approach to the “traditional” method of collecting linear measurements and applying multivariate statistical methods to these data. Landmark- and outline-based GM methods are suggested to have several advantages over the “traditional” method. Due to the increasing popularity of GM methods in the modern literature, this chapter first compares different morphometric techniques, and then reviews the methods applied to recording structures, with a focus on GM outline-based analyses. It is clear that outline methods have become a popular method of analysis for structures such as otoliths, particularly for the purpose of distinguishing between population components. However, for other structures such as beaks this technique is only in its early stages of application and is more difficult to apply but shows great promise for future studies. The advantages of using a holistic approach, incorporating several techniques including outline analysis for stock identification purposes is discussed.

The significance of cephalopod beaks as a research tool: An update

“…Several methods applicable to cephalopod beak shape analysis were developed to date (Fang et al, 2018;Lishchenko and Jones, 2021). Nowadays, the group of methods which can be called "traditional morphometrics" (measurements of the linear distances, or indices, based on these measurements), is criticised for leading to a significant loss of information due to the complexity of studied structures and the multicollinearity between measurements (Adams et al, 2004;Volpedo and Vaz-dos-Santos, 2015).…”

“…The most applied methods in this group are Fourier transform (where outlines are expressed as a function of equally spaced radii or of the tangent angle to the outline or of the curvilinear abscissa) and wavelet transform (with outlines expressed by a set of functions representing the dilations and translations of a single unique function). Application of both approaches to analyse the shape of cephalopod beaks have benefits and limitations (Lishchenko and Jones, 2021). Specifically, landmark-based methods allow selecting the points of interest which presumably have some biological or taxonomic meaning (e.g., rostral tip and wing fold, whose position reflects the length and curvature of the rostrum).…”

“…Thus, the software for automatic identification of the cephalopods based on the shape of their beaks may be based on Fourier or wavelet transformation, similar to the system developed for fish identification (Lombarte et al, 2006). It should be noted that accuracy of such an approach to identification may be improved if supplemented by the analysis of beak's pigmentation (Fang et al, 2017), or if only the pigmented part is analysed (Lishchenko and Jones, 2021).…”

“…Cephalopod beaks can also provide considerable information on a wide range of physiological, biological and ecological traits, including cephalopod availability, consumption of cephalopods, migrations, competition between cephalopod predators, levels of cephalopod scavenging by predators, distribution, age, growth, cohorts, life-events, stress, thermal changes, reproduction, feeding ecology, behavior, spawning areas, post-spawning mortality and sexual dimorphism [e.g., see review in Xavier et al (2016) and Arkhipkin et al (2018); Table 1]. More recently, new emergent techniques for work on beaks (e.g., stable isotope and trace elements analyses, geometric morphometrics and microstructure analysis) have provided further information on habitat and trophic position, composition, contamination, response of cephalopods to climate variability at individual and/or population levels, embryonic morphogenesis, paralarval ontogeny, ecology and age estimation (Cherel and Hobson, 2005;Perales-Raya et al, 2014b;Xavier et al, 2016;Perales-Raya et al, 2018;Queirós et al, 2018;Golikov et al, 2019a;Golikov et al, 2019b;Northern et al, 2019;Abreu et al, 2020;Queirós et al, 2020a;Armelloni et al, 2020;Queirós et al, 2020b;Franco-Santos and Vidal, 2020;Golikov et al, 2020;Perales-Raya et al, 2020;Fang et al, 2021b;Lishchenko and Jones, 2021). Consequently, the importance of cephalopod beaks in ecological studies continues to attract attention and recognition, with various workshops being organised (Clarke, 1986;Xavier et al, 2007a;Jackson et al, 2007;Xavier et al, 2015).…”

Intraspecific morphological variation in shads, Dorosoma anale and D. petenense (Actinopterygii: Clupeiformes: Clupeidae), in the Mexican Grijalva and Usumacinta river basins

“…This study used linear biometric and geometric morphometric methods. Notably, both analyses are complementary and have been widely used in ichthyology to identify intra-and interspecific morphological differences and describe patterns of variation (Kerschbaumer and Sturmbauer 2011;Tripathy 2020;Lishchenko and Jones 2021). Morphological differentiation was expected due to historical vicariance events that occurred during river separation and sea level changes in northern Middle America.…”