Morphology and ontogenetic changes in otoliths of the mesopelagic fishesCeratoscopelus maderensis(Myctophidae),Vinciguerria attenuataandV. poweriae(Phosichthyidae) from the Strait of Messina (Mediterranean Sea)

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)

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.

Scanning electron microscopy and morphological analysis reveal differences in the otolith morphology of three species of the family Lethrinidae (Teleostei: Perciformes) from Yemen

Otoliths, or ear-stones, are calcareous components in the static-acoustic organs of teleost fishes with a characteristic morphology. As such, they are widely used in fisheries because of the information stored in them concerning, for example, environment, age, and so forth. Otoliths of three lethrinid species Lethrinus borbonicus (Valenciennes, 1830), L. lentjan (Lacepède, 1802), and L. mahsena (Forsskål, 1775) were collected from fish caught along the Red Sea coast of Yemen. Images taken with a scanning electron microscope were used to determine their characteristics. Twenty-two characters were defined to describe the shapes of the otoliths. Eleven measurements of distance between selected features were used for a linear regression and multivariate analysis to characterize the species by their otoliths. The results illustrate ontogenetic changes for different age groups based on the recorded shapes. All three species show a linear relationship between the total length and the morphometric measurements. A linear discriminant analysis shows marked differences between the otoliths of the three species and emphasizes the importance of the measured variables. Otoliths of L. lentjan and L. borbinicus are more similar to each other and differ from those of L. mahsena. A comparison with previously published otoliths of the species studied from other areas confirms an intraspecific uniformity across larger geographic distances, making the characters useful for diagnostic purposes.

Otolith Analyses Highlight Morpho-Functional Differences of Three Species of Mullet (Mugilidae) from Transitional Water

Otoliths are used in taxonomy and ichthyology as they can provide a wide range of information about specimens. They are an essential tool to monitor the most sensitive species for a sustainable exploitation level. Despite the increasing use of sagittae in research, their inter- and intra-specific variability and eco-functionality are still poorly explored. This paper aims to investigate the inter- and intra-specific variability of Mugilidae sagittae using morphological and morphometrical analysis, as well as scanning electron microscopy and shape analysis. The sagittae of 74 specimens belonging to three different Mugilidae species, collected from a coastal lagoon, were analyzed to give an accurate description of their morphology, morphometry, shape and crystalline habits. The results highlighted the intra- and inter-specific variability of sagittae, showing morphometrical differences among species and slight differences between left and right sagittae in C. labrosus individuals. Moreover, SEM images showed a peculiar crystal organization, with several different crystal habits and polymorphs. This study provides an accurate description of sagittae in the studied species, deepening the knowledge on inter- and intra-specific variations and crystal habits and providing data which will be useful for future studies on otoliths. With this data, it will be possible to improve conservation and exploitation sustainability in sensitive habitats.

Intra- and interspecific variability among congeneric Pagellus otoliths

Otolith features are useful tools for studying taxonomy, ecology, paleontology, and fish biology since they represent a permanent record of life history. Nevertheless, the functional morphology of otoliths remains an open research question that is useful to completely understand their eco-morphology. This study aims to deepen the knowledge of intra- and interspecific variation in sagitta morphology in three congeneric seabreams, to understand how such variability could be related to the lifestyles of each species. Therefore, the sagittae (n = 161) of 24 Pagellus bogaraveo, 24 Pagellus acarne, and 37 Pagellus erythrinus specimens, collected from the south Tyrrhenian Sea, were analyzed using scanning electron microscopy and a stereomicroscope to assess morphometric features, variability between otolith pairs and the external crystalline structure the of sulcus acusticus. Statistical analysis demonstrated that, between the species, variability in sagittal otolith rostral length growth and sulcus acusticus features, correlated with increased fish total length and body weight. Moreover, slight differences between otolith pairs were detected in P. acarne and P. erythrinus (P < 0.05). The results confirm changes in otolith morphometry and morphology between different congeneric species and populations of the same species from different habitats.