Comparative ultrastructure and ornamentation characteristics of scales in gobiid species (Teleostei: Gobiidae) using the scanning electron microscope

Abstract

To study scale based phylogenetic affinity, the ultrastructure and ornamentation characteristics of body key scales were studied for 12 gobiid species from the Iranian coast of the Persian Gulf including Qeshm and Hormuz Islands and the Makran coast of the Oman Sea using scanning electron microscopy (SEM) technique. The scales were removed from below the first dorsal fin, cleaned in potassium hydroxide solution 1%, and were prepared for the SEM imaging. The presence of both ctenoid and cycloid scales in the studied gobiids was revealed. The focus of ctenoid scales was positioned posteriorly, while the focus of cycloid scales was positioned in the postero-central part of the scale. In all the studied species, radii were located only on the anterior part of the scale, and the primary radii were dominant. Also, there were no granules in the inter circular space, but bifurcation was observed in some circuli.In most species, the teeth-like structures called lepidonts were present on the crest of circuli, which functionally help to firmly attach the scales to the epithelium. The dendrogram of the between-groups-linkage method sorted the gobiid species into the two main groups of five distinct clusters: (a) Cryptocentroides arabicus and Cryptocentrus cyanotaenia (the Cryptocentrus-lineage); (b) Bathygobius meggitti and Bathygobius cocosensis (the Glossogobius-lineage); (c) Coryogalops adamsoni and Coryogalops tessellatus (the Gobius-lineage); (d) Acentrogobius dayi, Istigobius ornatus,Favonigobius reichei, Aulopareia ocellata, and Silhouettea ghazalae (the Gobiopsis-lineage). It seems that the dendrogram topology obtained based on the macro-and microscopic structures of scales, reveals phylogenetic lineages of gobies that have already been proposed for these taxa. Hence, the results of this study are largely consistent with the previous molecular studies on the gobiid fishes and implied that besides other data, the analysis of scale shape and scale-surface microstructures could be served to study the diversification of gobiid species.

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

“…The shape and surface ornamentations of the scales (e.g., circuli, ctenii, focus size and position, lepidont, and radii) have long been used as systematic characters (Casteel, 1972;Fouda, 1979;Gholami, Teimori, Esmaeili, Schulz-Mirbach, & Reichenbacher, 2013;Ibanez & Jawad, 2018;Kobayashi, 1955;Sadeghi, Esmaeili, Teimori, Ebrahimi, & Gholamhosseini, 2020;Van Oosten, 1957), and also applied for functional approach (e.g., Burdak, 1979).…”

Morphological and microstructural characteristics of scales in longnose goby Awaous jayakari (Teleostei: Gobiidae): Light and scanning electron microscopy approaches

“…Microscopic examinations revealed the presence of scales with polygonal (hexagonal and pentagonal), circular/discoid, oval/elliptical, and quadrilateral/square shapes in different body regions of A. jayakari in three size groups dominated by polygonal scales. Polygonal scales have also been reported for some other gobies (Sadeghi et al, 2020). According to Sadeghi et al (2020), the scale shapes (Key scales) were generally polygonal or close to polygonal in 10 out of 12 studied gobiid species.…”

“…Polygonal scales have also been reported for some other gobies (Sadeghi et al, 2020). According to Sadeghi et al (2020), the scale shapes (Key scales) were generally polygonal or close to polygonal in 10 out of 12 studied gobiid species. Exceptions for two species of Cryptocentrus-lineage, Cryptocentroides arabicus (Gmelin, 1789) and C. cyanotaenia (Bleeker, 1853) (Gobiidae: Gobiinae).…”

“…In their study, Purrafee Dizaj et al (2020) and Sadeghi et al (2020) have underlined that the morphological analysis of the scales of the clupeids and gobies were largely consistent with their phylogenetic affinities using (COI sequences) and therefore, macro and micro scale morphological characteristics could effectively contribute to the F I G U R E 1 9 Light microscopy details of scales in 13 regions of a small size (I) A. jayakari (s11, F), SL 48.7 mm, scale bar = 0.5 mm…”

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

“…We, therefore, concluded that variation of scale characters in the studied Mullidae fishes has probably taxonomic and even phylogenetic information in both species and genus levels because the scale morphological‐based tree was largely consistent with the known systematics of the studied fishes. However, because of the direct environmental effects on the scale, body region‐dependent variation of scale, and also the fish‐length‐dependent changes of the fish scale, therefore, the scale should be used carefully for taxonomic purposes (e.g., Helfman, Collette, & Facey, 1997; Motamedi, Teimori, Amiri, & Askari Hesni, 2020; Purrafee Dizaj et al, 2020; Sadeghi, Esmaili, Teimori, Ebrahimi, & Gholamhosseini, 2021, this study).…”