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The killifish genus Aphaniops consists of nine species distributed in Eastern Africa and the Middle East. However, distinguishing these species from each other based on morphological traits is challenging. Here we investigate the utility of otoliths (sagittae) in distinguishing between A. dispar, A. ginaonis, A. hormuzensis, A. kruppi and A. stoliczkanus. Our approach is based on otoliths from 89 specimens and involves (1) otolith morphometrics, following prior recommendations, (2) shape analysis of otolith contours based on discrete wavelet transformation—a novel method in killifish otolith research—and comparative statistical analyses. Both methods reveal significant interspecific variation in the otolith regions of the rostrum, antirostrum and excisura. While method (1) effectively discriminates most species, method (2) struggles to differentiate A. hormuzensis, A. stoliczkanus and A. kruppi. Additionally, both methods encounter challenges in correctly classifying A. hormuzensis due to the high otolith variability of this species in our sample. Possible factors accounting for their variability are environmental fluctuations at the sampled hot sulphuric spring (Khurgo) and potential introgressive hybridization. We conclude that otolith morphometry is a valuable tool for Aphaniops species identification. Furthermore, we found that the distinctiveness of species‐specific otolith traits increases with the divergence age of the species. [ABSTRACT FROM AUTHOR]

To evaluate scale morphological variability (shape, size, topological macro‐ and microstructures, ornamentation patterns) of cyprinid fishes, nine species of the genus Garra were selected and their scales from five different body regions were studied by using light and scanning electron microscopy. The scales of the examined species were thin with a central or antero–centrally positioned focus, with no cteni in the posterior part. In addition to these typical characteristics, some morphological variation was observed in the overall shape (irregular round, true oval, round‐triangular, irregular pentagonal, hexagonal, irregular hexagonal, pentagonal, ovoid), and the focus shape. These variations were mainly dependent on the fish lengths and the flank region. Morphological analysis clustered the examined species into two distinct groups. Group I consisted of G. amirhosseini and G. gymnothorax, while Group II has three subgroups, which include G. persica and G. mondica (subgroup I), G. meymehensis, G. rossica, G. nudiventris, G. hormuzensis (subgroup II), and G. rufa (subgroup III). The grouping of the studied Garra species based on the current scale morphological characters and the molecular data was only consistent for G. rossica and G. nudiventris. In addition, in the phylogenetic tree, G. persica, G. mondica, G. amirhosseini, and G. hormuzensis formed a distinct clade. However, these species did not represent close relationships in the dendrogram obtained from the scale morphology. A possible explanation why the grouping of the studied Garra species based on their scale morphological characters does not match their phylogenetic relationships is that most of the scale morphological traits vary depending on the fish size and the location of the scales on the flank. Therefore, except for some traits, that is, central or antero–centrally positioned focus, having no cteni, a specific sectioned form so called "tetra‐sectioned" type, the other examined variables are not useful enough to be used in the taxonomic study of the examined cyprinid fishes. Therefore, scale morphological characters should be used carefully for taxonomic purposes. Research Highlights: Shape, size, topological macro‐ and microstructures, and ornamentation patterns of nine species of the genus Garra were studied by using light and scanning electron microscopy.The scales were thin with a central or antero–centrally positioned focus, with no cteni in the posterior part.Morphological variation was observed in the overall shape (irregular round, true oval, round‐triangular, irregular pentagonal, hexagonal, irregular hexagonal, pentagonal, and ovoid), and the focus shape.The grouping of Garra species based on the current scale morphological characters and the molecular data was only consistent for G. rossica and G. nudiventris. [ABSTRACT FROM AUTHOR]

Scale morphology and its structural details were studied with morphometry, geometric morphometrics, and scanning electron microscopy in five Iranian Aphanius species and examined comparatively with molecular phylogeny. Scales were cycloid and circular in A. farsicus Teimori, Esmaeili & Reichenbacher and A. vladykovi Coad, cycloid and polygonal in A. isfahanensis Hrbek, Keivany & Coad and A. sophiae (Heckel), and were spined and polygonal in A. dispar Rüppell. Univariate analysis indicated that the relative length of anterior margin of radii played a significant role in the separation of some species studied (P < 0.05). Canonical Variates Analysis (CVA) based on seven landmarks showed clear separation between the Iranian inland and inland-related Aphanius species (IIRAS) group (four species) and the brackish water species (A. dispar). The lepidonts were conical in the IIRAS group with the exception of A. isfahanensis (rounded) and were rounded in A. dispar. Based on the basal position of the brackish water Aphanius species in the phylogenetic trees of the genus Aphanius, it can be assumed that the presence of rounded lepidonts was a primary state in their scales or is the result of convergent evolution. Also, the polygonal state in the scales of Aphanius species was a primitive shared character state.

The scale morphology of pleuronectiforms in the Gulf of Oman remains insufficiently known. This study used light microscopy and morphological analysis to examine scale variation across the flank of four Tonguefishes species; Cynoglossus arel, C. bilineatus, C. lingua, and C. puncticeps. Scales were extracted from six flank regions, three on the eyed and blind sides, respectively. The most differentiated species was C. arel, which showed significant differences in four size variables in five regions. In Cynoglossus arel and C. lingua, the scales of the eyed side were ctenoid, and those scales from the blind side were cycloid; C. puncticeps have ctenoid scales on both flank sides and C. bilineatus has cycloid scales on both sides. All species' scales on the blind side have fewer ctenial spines (except in C. bilineatus). This study indicated that scale morphology demonstrated considerable variation among the flank regions of the examined species. As a result, the scales from the head and the trunk regions of the eyed side and the scales from the head region of the blind side have a good power of species separation in this family. [ABSTRACT FROM AUTHOR]

Scale development and its regeneration potency were evaluated in a desert killifish Aphaniops hormuzensis (family Aphaniidae) in laboratory conditions by using light and scanning electron microscopy. Scale development in A. hormuzensis took 156 days at room temperature. Four specific regions of scale formation were detected. The first scale development began 13 days post‐hatching (dph) (total length [TL] = 8.5 mm) at the caudal peduncle region and is extended anteriorly 26 dph (TL = 13.6 mm) at the area below the dorsal fin. Scales began forming independently in the head region at 33 dph (TL = 21.7 mm), and in the abdominal region, began at 41 dph (TL = 25.8 mm). Additional points of scale origin were detected on the sides of the operculum or behind and below the eyes. Scale regeneration in the caudal peduncle started 6 days after removal (dar). In 16 dar, the microstructural features appeared and the growth circles, a wide and oblong focus (focus length = 0.6 ± 0.05 µm), and lepidonts were also formed. In 36 dar, the scale shape was gradually changed from circular to a polygon, and radii were distinguishable in the anterior field. The pattern of scale formation could be useful in enhancing the understanding of systematics and phylogeny, functional morphology, and habitat use. It could also be useful in helping to define the Larval/juvenile transition period. Research highlights: The squamation development in Aphaniops hormuzensis took 156 days at room temperature.The development of the first scales began 13 days after hatching at the caudal peduncle region and it is completed in 56 days.It could be useful in helping to define the Larval/juvenile transition period. [ABSTRACT FROM AUTHOR]

Macro‐ and microscopic characteristics of flank scales for 12 species were investigated from the Persian Gulf Coral Reefs. In Lutjanus argentimaculatus and L. russellii (family Lutjanidae), the scales of different flank regions were not different, while four characters showed variation in the scale of L. lutjanus i.e., scale shape (pentagonal, hexagonal and square), anterior margin (waved, scalloped and smooth), focus shape (circular and oblong) and focus position (postero‐central and central), displayed variation. Scale type (ctenoid) and posterior margin (transforming ctenii) did not show variation and could be considered to be specific in this family. In Epinephelus chlorostigma (family Serranidae), the scales of flank regions did not display variation, while in E. areolatus, E. diacanthus and E. radiates, the scales showed considerable variation. The most variable characters were scale shape, posterior margin and focus shape. Therefore, in fish systematics studies on the base of scale, it is particularly important to compare scales from the same flank regions. Also, some criteria such as size‐dependent alternation, ontogenetic changes and variation between flank regions, should be considered. This study supports the potential of scale morphology to help for the understanding of fish diversity in the coral reef ecosystem. [ABSTRACT FROM AUTHOR]

The axial skeleton morphology of eighteen aphaniid species was examined for the first time by X‐ray radiography, a non‐lethal method. The number of total vertebrae in the genus Aphanius is ranged from 26 to 29, in Aphaniops, it is ranged from 24 to 28, and in Paraphanius mento, it is ranged from 26 to 27. The vertebral column in Aphanius was often slightly curved, and it is varied from almost straight (most common) to slightly or strongly curved and straight in two others. The caudal skeleton of the family Aphaniidae is characterized by a single and completely fused hypural plate, and a total number of 9–12 branched segmented soft rays, a single and elongate epural bone. All examined species of the genus Aphanius and Paraphanius mento displayed a straight epural bone in their caudal skeleton, while it was often sinuous‐like and thick in all species of the genus Aphaniops. This study supports the assumption that a sinuous epural is likely the first detected morphological synapomorphy for the "inner" clade of Aphaniops. The family Aphaniidae is closer to Cyprinodontidae, Valenciidae and Fundulidae than other cyprinodontiforms in the caudal skeleton, which is in agreement with the multigene phylogeny of cyprinodontiforms. [ABSTRACT FROM AUTHOR]

The taxonomic validity of the recently described endemic species Aphaniops hormuzensis (Cyprinodontiformes: Aphaniidae) from southern Iran has been questioned as its original description did not include data from another recently described endemic species, i.e. A. kruppi from eastern Oman. Because of the absence of mitochondrial COI gene sequences, Aphaniops hormuzensis was also not included in recent phylogenetic studies. We therefore generated COI gene data for A. hormuzensis and used the new data to construct a phylogenetic tree that also included A. kruppi (amongst other species). Bayesian and Maximum likelihood phylogenetic analyses reveal that both A. hormuzensis and A. kruppi are monophyletic, with high support values. We conclude that A. hormuzensis is a valid species, which is distinct from A. kruppi and also from A. ginaonis, another tooth-carp endemic to southern Iran. Our results add further support to the taxonomic distinctness of A. hormuzensis from southern Iran. [ABSTRACT FROM AUTHOR]

The diagnostic features of otolith morphology were provided for the clupeid fishes of the Iranian brackish and marine resources to be used as diagnostic features for the identification of clupeids diversity in these regions. Fish individuals belong to 20 species belong to 13 genera, and four families were collected from the Caspian Sea, the Persian Gulf and the Makran zone of the Oman Sea. Overall, seven otolith morphotypes were distinguished, that is lanceolated (45%), fusiform (20%), boot‐like (15%) and clamp‐like, pentagonal, elliptic and rectangular (each 5%, respectively). The univariate analysis showed that all variables except shape index [sulcus area (SS)/otolith area (OS)] and ROx (roundness) were significantly different among the clupeid species. The interspecific relationships of the otoliths were analysed based on the data of otolith morphology and otolith shape indices. Both dendrograms showed somehow an obvious separation among the studied species. However, the interspecific relationships in the dendrogram based on the otolith morphology have a better resolution. These phenotypic relationships based on otolith morphology among the studied clupeids are largely consistent with the previous hypothesis on the systematics of these fishes and emphasized that the morphological and morphometric features of the otolith, which are highlighted in this study, could be adequately used as diagnostic features for the identification of clupeids diversity. [ABSTRACT FROM AUTHOR]

The scale morphology of a native goby, Awaous jayakari (Gobiidae) was studied using scanning electron microscopy and light microscopy. The morphological descriptions were based on the scale's type, shape, and features of the anterior, posterior, and lateral fields. Further characteristics of the focus, circuli, radii, lepidonts, and cteni, were investigated. Morphometric indices were calculated for some scales. Shape variability of scales was high in different regions. However, the majority of scales displayed a polygonal shape (hexagonal and pentagonal). Both ctenoid and cycloid scales were observed in the studied fishes. The ctenoid scale of A. jayakari was peripheral and characterized by the presence of one row of marginally located spines in two completed and uncompleted subtypes. The focus was positioned posteriorly or postero-centrally. The microscopic examinations revealed the presence of lepidonts of different sizes being very tiny, small, or prominent performing flat, blunt, pointed, short, or truncated shapes. The rostral margin of the scales was convex to moderately flattened and represented striate, scalloped, or waved types. Lateral fields were often flattened in all regions, while convex in the lateral fields of the scales of some individuals. The posterior field showed variations in different regions, for example, tapered and flattened ends. The anterior-posterior axis presented a laterally expanded or an elongated extension. The considerable morphological variation in the scales of various body regions makes it difficult to nominate a typical scale to be used in taxonomic studies. However, the key scales can be used for the comparison of different Awaous species. [ABSTRACT FROM AUTHOR]

The active geology and ecological diversity in the Persian Gulf drainages create a rich source of biodiversity for the tooth‐carp fishes from which evolutionary processes can be studied. Here, we explored morphological differentiation in tooth‐carp Aphaniops hormuzensis from three ecologically diverse habitats (Khurgu sulphuric spring, Shur high‐salinity river and the urban canal) in the Hormuz riverine system, southern Iran. The evidence of sexual dimorphism was found in fish and otolith traits mainly in the Khurgu spring. The extreme conditions of the Khurgu spring could lead to the microhabitat segregation by fish individuals with different ages and spatial sexual segregation, and caused high intrapopulation differentiation in this site. However, the most diverged population belonged to the urban canal, which had more elongated pre‐ and post‐dorsal lengths, as well as a deep otolith. In sum, the observed phenotypic variations in A. hormuzensis are mainly influenced by sex‐dependent factors such as sexual dimorphism and the specific ecological condition of the Khurgu sulphuric spring (extreme sulphur‐rich habitat) and the urban canal (high food availability and hybridization event). This study provides the basic opportunity to explore the relative roles of ecological divergence and habitat differences in the morphological differentiation of A. hormuzensis. [ABSTRACT FROM AUTHOR]