Otolith Morphometric and Shape Distinction of Three Redfin Species under the Genus Decapterus (Teleostei: Carangidae) from Sulu Sea, Philippines

Abstract

Otoliths are paired calcified structures in the inner ear of teleosts that function in hearing and balance. In this study, the use of otolith morphometrics and shape analysis were explored to delineate the redfin species under the genus Decapterus from the Sulu Sea, Philippines, namely, Decapterus kurroides, D. smithvanizi, and D. tabl. Results showed that the mean otolith shapes are unique within species (p < 0.001). The otolith size-related (OW—otolith weight, OL—otolith length, OH—otolith height, OA—otolith area, and OP—otolith perimeter) and shape-related (RE—rectangularity, SQ—squareness, EL—ellipticity, RO—roundness, AR—aspect ratio, FF—form factor, CO—compactness, and CI—circularity) morphometric indices also showed significant variations (p < 0.001) among the three species. Distinct regions differentiating D. kurroides from the other two species were seen along the dorsal margin of the otoliths, which was supported by its significantly higher values for OH (size-related index) and RO (shape-related index). In addition, the morphometric indices showed significant variations (p < 0.001), except for RE. Furthermore, it was revealed that the size-related indices were able to separate D. kurroides from the other two species, which turned out to be indifferent. The results provided relevant data on the use of otoliths as an additional confirmatory tool in species delineation of the identified redfin species, and, therefore, offer opportunities of applying the same method in delineation and, eventually, identification of species from other genera, especially those that closely resemble each other.

Differentiation of Spatial Units of Genus Euthynnus from the Eastern Atlantic and the Mediterranean Using Otolith Shape Analysis

“…From the analysis in the paper, the differentiation results are similar to other previously published results for different species of one same genus [27,91,[99][100][101]. Some studies have been carried out using otolith shape analysis in tunas and small tunas, mainly for stock delimitation [29][30][31].…”

“…The high differentiation and classification rates observed for our research-collected otoliths indicate that, as previously confirmed by genetic analyses, it follows that there are clear otolith shape differences between the Northeast Temperate Atlantic together with the Mediterranean Sea and Eastern Tropical Atlantic areas with a high degree of confidence. A pattern that is repeated in this type of study in the differentiation of species from shape otoliths, which is also fulfilled in our work, is that at least three otolith morphological descriptors analyzed show significant variations between the groups of individuals analyzed and 25% of the otolith outlines present great divergences [85][86][87][88][89][90][91]. Perhaps these are results to consider when carrying out an analysis of this type for the differentiation between species.…”

“…There is abundant scientific literature that applies otolith shape analysis as a stock differentiator or population structure descriptor [79][80][81][82][83][84]. This technique has also been widely used for the differentiation between species [85][86][87][88][89][90][91], demonstrating that it is an efficient technique for this type of analysis [28]. The shape of the otolith is known to vary depending on the ecological, evolutionary, and phylogenetic characteristics of each species [92].…”

Discrimination of Schizothorax grahami (Regan, 1904) Stocks Based on Otolith Morphology

“…In addition, in some other population studies, the overall discrimination success rate obtained by using elliptic Fourier coefficients exceeded 90.0% [40,41]. Morales et al conducted research on the otolith morphometric and shape distinction of three redfin species under the genus Decapterus (Teleostei: Carangidae); their results showed that the otolith shape analysis was effective in separating the redfin species of Decapterus from the Sulu Sea and identifying regions of marked differences in the otolith outline [42]. This research is similar.…”