Scales and otoliths as identity cards of the Indian oil sardine Sardinella longiceps (Teleostei: Clupeiformes) populations: Ultrastructure and ornamentation characteristics using light and scanning electron microscopy

Abstract

Scale and otolith morphology and morphometry of Indian oil sardine Sardinella longiceps (Clupeidae) were investigated and described using light and scanning electron microscopy from eight different body regions for scales and the right and left otoliths. Scales of the Indian oil sardine show general characteristics of the other studied clupeids sand that are easily distinguishable from other fish groups, by having striae in the posterior field. The studied cycloid scales of S. longiceps were classified into three types based on the overall shape including circular (e.g. true circular and cordate), pentagonal and quadrilateral in the different body regions. The circular shape was the most common shape (87.5%), while the quadrilateral and pentagonal forms constituted 6.25% each. The results also showed that the relative scale size (J-index) plays a desirable contribution in separating the examined populations. The results showed that the mean (or relative) scale size for all the eight regions in the Oman Sea population is larger than the Arabian Sea population. Also, another scale variable, the scale shape index (Si index), demonstrated variation (a mean of 0.86 to 1.1) in different regions of both populations from the Oman and Arabian Seas. Interestingly, here, we found that scale characters of S. longiceps not only differ from its other congeneric species, but also differ in the populations from both sides of the Oman Sea (Iran and Oman) and the Arabian Sea. It shows a positive signal for the presence of different taxonomic and management unit in the Oman and Arabian Seas. The idea should be approved by using integrated molecular and morphological traits. The otolith morphology of S. longiceps from the Oman and Arabian Seas was more conservative than the scales, which can be due to its function actin primarily as a balance organ and also enhancing hearing. The overall shape of S. longiceps otolith was lanceolate, with an elongated morphology and a well-developed rostrum, an ostial sulcus acusticus that opens to the anterior/ dorsal margin. These morphological characters are also found in the Iranian population of S. longiceps. However, otolith displayed variation in biometric parameters among two populations and left and right otoliths and the RRL parameter were important characters to discriminate

Scales surface topography: Comparative ultrastructural and decorative characteristics of a modern elasmoid fish scales in a cyprinid fish, Garra shamal (Teleostei: Cyprinidae) using digital optical light and scanning electron microscope imaging

“…Fishes with about 36,305 species (Fricke et al, 2020) are the most rich‐species group of vertebrates in the world with a high diversity in morphology, biology, ecology, genetics, and behavior. Nature is influential in most of the strategies ending in the creativity of a specific character, which appeared as a strong tool for species recognition to be used as an identity card (Al Jufaili et al, 2022; Laidre, 2021). These fundamentally different strategies emerged in the course of evolution (Al Jufaili et al, 2022; Laidre, 2021).…”

“…Nature is influential in most of the strategies ending in the creativity of a specific character, which appeared as a strong tool for species recognition to be used as an identity card (Al Jufaili et al, 2022; Laidre, 2021). These fundamentally different strategies emerged in the course of evolution (Al Jufaili et al, 2022; Laidre, 2021). To study systematics and phylogeny of this diverse taxon, numerous morphological and molecular characteristics are used (e.g., Echreshavi et al, 2021; Esmaeili, Sayyadzadeh, et al, 2020; Esmaeili, Teimori, et al, 2020; Teimori & Esmaeili, 2022; Zarei et al, 2021).…”

“…The optical light microscopy (LM) and scanning electron microscopy (SEM) techniques, however, had particular contributions to our knowledge of fish scale morphology to be used sufficiently in fish and fisheries investigations to improve our knowledge to understand fish systematics and also to assess their phylogenetic relationships (e.g., Baudelot, 1873; Bräger et al, 2017; Chu, 1935; Cockerell, 1915; Lagler, 1947; Roberts & Aspy, 1993; Williamson, 1851). Therefore, since that time, fish scale morphology and their outer surface ornamentations and especially their surface microstructures have been widely studied in many fishes (Al Jufaili et al, 2021, 2022; Esmaeili et al, 2019; Esmaeili & Gholami, 2007; Ferrito et al, 2003; Jawad, 2005; Lanzing & Higginbotham, 1974; Purrafee Dizaj et al, 2020; Sadeghi et al, 2021; Seshappa, 1999). However, information on the scale morphology and structure of many inland fishes of the Arabian Peninsula including Oman is rare and it is limited to a few recent studies (Al Jufaili et al, 2021).…”

Imaging scale surface topography of an endemic cyprinid fish, Garra sharq from the Arabian Peninsula: An integrated optical light and scanning electron microscopy approach

“…Fish scale morphology and their outer surface ornamentations and especially their surface microstructures have been widely studied in many fishes (e.g., Al Jufaili et al, 2021, 2022; Esmaeili et al, 2007, 2019; Ferrito et al, 2003; Jawad, 2005; Lanzing & Higginbotham, 1974; Purrafee Dizaj et al, 2020; Sadeghi et al, 2021; Seshappa, 1999). However, information on scale morphology, topography, and microstructure of many fishes of the world especially the endemic fishes of the Arabian Peninsula is rare and is limited to a few recent studies (Al Jufaili et al, 2021).…”