Intra-population variability of the saccular, utricular and lagenar otoliths of the garfish Belone belone (Linnaeus, 1760) from South-Western Ionian Sea (Central Mediterranean Sea)

Abstract

The garfish Belone belone represents the only valid endemic Belone species for the Mediterranean Sea and the eastern Atlantic Ocean. It shows a wide global distribution range, with a high commercial value and ecological relevance in the pelagic domain. Despite this, there needs to be more knowledge regarding the otoliths of this species, with the total absence of descriptions regarding asterisci and lapilli from Mediterranean populations and a lack of studies on the reliability of shape analysis on its sagittae. The present paper aims to provide the first main contours description of the three otoliths pairs from a Mediterranean population, providing an accurate investigation of morphology, morphometry, and intra-specific variability of sagittae, lapilli, and asterisci. Results showed (i) the absence of directional bilateral asymmetry and sexual asymmetry for the three otoliths pairs, (ii) a different morphology and morphometry of sagittae, lapilli and asterisci than those described in the literature, and (iii) an enhanced variability between sagittae morphometry and shape between the three investigated size classes. All these data confirmed the reliability of the studied species of shape analysis, showing a geographical and size-related variability of otoliths features probably related to genetics, environmental conditions, and life habits variations.

Keywords: Asterisci; Belone belone; Lapilli; Sagittae; Garfish; Ionian Sea; Shape analysis.

Fig. 1

Map of the Mediterranean Sea with sampling area of B. belone specimens analyzed in this study highlighted by the red circle

Fig. 2

Stereoscope images of left sagittae belonging to size class I (a), II (b) and III (c). Scale bar: 1 cm

Fig. 3

Linear Discriminant Analysis (LDA) between sagittae morphometric parameters from the three investigated size classes (aqua dots I, blue dots II and red dots III)

Fig. 4

Mean shape of the left sagittae contours belonging to the three size classes (a) and to males (M) and females (F) (b)

Fig. 5

Linear Discriminant Analysis (LDA) between elliptic Fourier descriptors calculated for the different size classes (aqua dots I, blue dots II and red dots III). Ellipses include a 95% confidence interval

Fig. 6

Stereoscope images of the dorsal (a) and ventral (b) sides of left lapillus. Scale bar: 0,5 cm

Fig. 7

Pearson correlation matrix assessed between biometric specimens’ data (total fish length, TL, and body weight, BW) of the investigated species and morphometric lapilli parameters

Fig. 8

Mean shape of the left (L) and right (R) lapilli contours

Fig. 9

Stereoscope images of the external (a) and internal (b) faces of the right asteriscus. Scale bar: 0,5 cm

Fig. 10

Pearson correlation matrix assessed between biometric specimens’ data (total fish length, TL, and body weight, BW) of the investigated species and morphometric asterisci parameters

Fig. 11

Mean shape of the left (L) and right (R) asterisci contours