New osteological and morphological data of four species ofAphaniops(Teleostei; Aphaniidae)

Abstract

Aphaniops dispar, widespread around the Arabian Peninsula, was recently separated in four species (A. dispar, A. hormuzensis, A. kruppi, A. stoliczkanus) by molecular results and colour patterns, but the morphological differences are small and call for more studies. Here we report differences in skeleton and median fin osteology of these species. In addition, we introduce the term 'modified caudal vertebra' to describe caudal vertebrae that are not directly associated with caudal ray support but are visibly modified from a 'usual' caudal vertebra. Aphaniops hormuzensis, an endemic species to southern Iran, has a significantly higher number of modified caudal vertebrae compared to the more widespread A. stoliczkanus and A. dispar, and also to A. kruppi. This is a surprising result as the caudal skeleton and related structures of the posterior caudal vertebral column have yielded successful results in separating between families or genera, but there are only a few studies that have examined these structures for their role in species diagnosis. Our study also highlights that state‐of‐the‐art methods in X‐raying and improved staining procedures assist in the discrimination of superficially similar species.

Axial skeleton morphology of the Western Palearctic aphaniid fishes (Teleostei: Cyprinodontiformes; Family: Aphaniidae)

“…We showed that all species of the genus Aphanius and also Paraphanius mento displayed a straight epural bone in their caudal skeleton, while all species of the genus Aphaniops (except A. furcatus) exhibited a sinuous and thick epural bone in their caudal skeleton. In their study, Charmpila et al (2020) showed that epural bone in four Aphaniops species, that is A. dispar, A. hormuzensis, A. kruppi and A. stoliczkanus all was thick and sinusoidal in shape, which is in agreement with our study. This characteristic had previously been reported for A. stoliczkanus (as Aphanius dispar in Costa, 2012), A. richardsoni, A. ginaonis and A. hormuzensis (Costa, 2012;Motamedi et al, 2018;.…”

“…Costa (2012) reported this character also for Aphanius isfahanensis, and two of the Anatolian Aphanius species but we did not observe it in the herein examined A. isfahanensis. Our study supports the assumption of Charmpila et al (2020) in which a sinuous epural could be the first detected morphological synapomorphy for the "inner" clade of Aphaniops.…”

“…In the study of Charmpila et al. (2020), the mean of the TV for genus A. dispar was counted as 26.9.…”

“…genus Aphanius) varied from 26 to 31 (mean 27.0 ± 0.15), and in the brackish water group (genus Aphaniops), it ranged from 25 to 28 (mean 26.5 ± 0.73), and for the two examined specimens of the genus Paraphanius, it was 26 and 27 (see also Tables 1 and 3). In the study of Charmpila et al (2020), the mean of the TV for genus Aphaniops was counted as 26.9 ± 1.06.…”

“…Concerning the pattern of variation in the number of the TV for the examined aphaniid fishes, it could be accentuated that (a) Aphaniops dispar (a brackish water member) displayed the lowest total vertebrae (TV = 24-25), while the two species of genus Aphanius, that is A. anatoliae from Anatolia (TV = 31) and A. arakensis from the Namak Lake basin of Iran (TV = 28-29) revealed the highest number, and (b) a higher inter-specific variation could be observed for the genus Aphaniops in compare to the genus Aphanius (see also Table 3). In the study of Charmpila et al (2020), the mean of the TV for genus A. dispar was counted as 26.9.…”