Digital light microscopy to characterize the scales of two goatfishes (Perciformes; Mullidae)

Abstract

The normal and lateral line scales from above the head and four flank regions were investigated in two goatfishes by using light microscopy to evaluate the microscopic characteristics of scale surface ornamentation from different body parts of these fishes and to add new morphological data for their discrimination. The body scales were removed and digital images captured with a Dino‐Lite digital camera connected to a Leica compound microscope. The presence of both transverse and longitudinal radii was a distinctive characteristic for the scales of studied goatfishes. The most distinctive features of the key scales discriminating the two goatfishes were the scale shape, the presence of irregular grooves in scale surface, the presence of transverse radii in the lateral fields, and the availability of lepidont at the anterior field. The lateral line scale ornamentations were almost similar in two species; however, the lateral line canal was branching in Parupeneus heptacanthus. Scale extension index indicated that in both species, the dimension of normal key scales tends to the right, while the dimension of lateral line scales tends to the left. This study accentuated that scales from different body regions may exhibit variation in surface ornamentations, that scale morphology could successfully be used to discriminate the examined goatfishes, and that the use of fish scale microscopy is an easy and relatively rapid method and does not require fish sacrifice. Since fish identification is essential for the conservation and management of species, the use of scale morphology to this purpose appears particularly promising.

Scanning electron microscopy and morphological analysis reveal size‐dependent changes in the scale surface ornamentation of tooth‐carp Aphaniops hormuzensis (Teleostei; Aphaniidae)

“…However, the comparison of scale variation from two examined body regions revealed that the scales from the caudal peduncle region demonstrated more sizedependent changes than those scales from below the dorsal fin. This confirms the previous studies that scale from different body regions may exhibit different surface ornamentations (e.g., Bräger & Moritz, 2016;Sabbah et al, 2020). The result of our study is also in agreement with the findings of Teimori et al (2021) in which the scales of small tooth-carps had often a large focus, while the scales of large fishes displayed often a small focus.…”

“…They are placed in three categories, that is, cycloid, ctenoid, and spinoid (Roberts, 1993; Wainwright & Lauder, 2016). The previous studies have shown that differences in scale type and morphology often exist among clades (Arratia, 2000; Roberts, 1993), within clades (Ibanez & Jawad, 2018), and even within regions of a single individual (Dapar, Torres, Fabricante, & Demayo, 2012; Motamedi, Teimori, Masoumi, Mohammadzadeh Shaghooei, & Mousavi, 2019; Sabbah, Teimori, & Hesni, 2020). One of the first classifications of fishes was based on scales (see Agassiz, 1834; Arratia, 2000, see figure 2).…”

Hidden morphological and structural characteristics in scales of mullid species (Teleostei: Mullidae) using light and scanning electron digital imaging

“…Thereafter, scales were subjected to digital imaging using a Nikon Eclipse 80i Digital Imaging Head connected to a computer. The digital images were then used for morphological descriptions and measurements (Sabbah et al, 2020).…”

“…However, the scale structure has lees been addressed in goatfishes of the Mullidae and are limited to Dapar et al (2012) on the Indian goatfish, Parupeneus indicus (Lacepède, 1802), and Sabbah, Teimori, and Askari Hesni (2020) on the Cinnabar goatfish, P. heptacanthus and Sulphur goatfish, Upeneus sulphureus (Cuvier, 1829).…”

“…Mullids have been subjected to various morphological, biological, and molecular studies (e.g., Golsline, 1984; Randall & Kulbicki, 2006; Uiblein et al, 2018; Uiblein & Causse, 2013; Uiblein & Gouws, 2015), however, light and scanning electron microscopy data on scales of these are scare (Dapar et al, 2012; Sabbah et al, 2020).…”