Host adaptation and unexpected symbiont partners enable reef‐building corals to tolerate extreme temperatures

Understanding the potential for coral adaptation to warming seas is complicated by interactions between symbiotic partners that define stress responses and the difficulties of tracking selection in natural populations. To overcome these challenges, we characterized the contribution of both animal host and symbiotic algae to thermal tolerance in corals that have already experienced considerable warming on par with end‐of‐century projections for most coral reefs. Thermal responses in Platygyra daedalea corals from the hot Persian Gulf where summer temperatures reach 36°C were compared with conspecifics from the milder Sea of Oman. Persian Gulf corals had higher rates of survival at elevated temperatures (33 and 36°C) in both the nonsymbiotic larval stage (32–49% higher) and the symbiotic adult life stage (51% higher). Additionally, Persian Gulf hosts had fixed greater potential to mitigate oxidative stress (31–49% higher) and their Symbiodinium partners had better retention of photosynthetic performance under elevated temperature (up to 161% higher). Superior thermal tolerance of Persian Gulf vs. Sea of Oman corals was maintained after 6‐month acclimatization to a common ambient environment and was underpinned by genetic divergence in both the coral host and symbiotic algae. In P. daedalea host samples, genomewide SNP variation clustered into two discrete groups corresponding with Persian Gulf and Sea of Oman sites. Symbiodinium within host tissues predominantly belonged to ITS2 rDNA type C3 in the Persian Gulf and type D1a in the Sea of Oman contradicting patterns of Symbiodinium thermal tolerance from other regions. Our findings provide evidence that genetic adaptation of both host and Symbiodinium has enabled corals to cope with extreme temperatures in the Persian Gulf. Thus, the persistence of coral populations under continued warming will likely be determined by evolutionary rates in both, rather than single, symbiotic partners.     

Molecular identification and phylogenetic relationships of Coleoidea (Mollusca: Cephalopoda) from the Persian Gulf and Oman Sea reveals a case of cryptic diversity

The Persian Gulf and Oman Sea constitute one of the most important marine ecosystems and have many economically important aquatic species, including several coleoid cephalopods. Some coleoids are difficult to identify using traditional morphological characteristics. In this study, two mitochondrial fragments, cytochrome oxidase I (COI) and the large ribosomal subunit (16S rRNA), were used for identification of coleoid species in four regions in the northern Persian Gulf and Oman Sea. The study led to the identification of potential cryptic species of Sepia, Amphioctopus and Uroteuthis. Furthermore, Euprymna hyllebergi was reported for the first time from the Persian Gulf. A high diversity of Coeloidea was found in the study area. Mean intraspecific and interspecific nucleotide distances for COI were 0%–2% and 2%–7%, respectively, while these values for 16S rRNA sequences were 0%–1% and 1%–4%. Given the uncertainty about species identity and the high levels of intraspecific genetic diversity reported for some species in GenBank, a comprehensive global study will be needed to resolve the taxonomic status of several coleoid species.     

Length‐weight relationships of four sharks caught in the Northern Persian Gulf and Oman Sea

The length–weight relationships (LWRs) for four little‐known shark species collected in the Persian Gulf and Oman Sea from March 2014 to September 2015 are presented, namely: Carcharhinus dussumieri, Carcharhinus macloti, Chiloscyllium arabicum, and Chaenogaleus macrostoma.     

Molecular confirmation of the occurrence of Elysia cf. tomentosa (Mollusca: Heterobranchia) in the Persian Gulf

The molluscan fauna of the Persian Gulf has recently been relatively well documented, yet there are few records of heterobranch sea slugs (opisthobranchs) from the Arabian parts and no report from the Iranian waters. Here we report for the first time the occurrence of one of these molluscs in the northern Persian Gulf (Bandar Abbas, Iran). Sacoglossan specimens were collected in association with the seaweed, Caulerpa sertularioides. Since morphological attributes were not adequately reliable for species identification, molecular approaches were carried out. Maximum-likelihood and Bayesian Inference analysis of partial DNA sequences of the mitochondrial cytochrome c oxidase subunit I (COI) locus were used for DNA barcoding of large-bodied specimens of Elysia. All Persian Gulf specimens were genetically confirmed as Elysia cf. tomentosa sp. 5, one of at least five morphologically similar but genetically distinct species in the taxonomically challenging and unresolved E. tomentosa complex. This species has previously been recorded only from Australia and Thailand and our finding adds another distant point to the geographic distribution of this species.     

Stock differentiation of the greater lizardfish Saurida tumbil (Teleostei: Synodontidae) collected along the western coast of the Arabian Gulf and Sea of Oman using meristic characters

Meristic variation among stocks of greater lizardfish Saurida tumbil through the western coasts of the Arabian Gulf and Sea of Oman was examined using meristic characters. Statistical analysis of meristic traits proposed that there is constrained migration of populations of greater lizardfish along the western coast of the Arabian Gulf and Sea of Oman. Overlapping of the two samples from the northern part of the Arabian Gulf (Iraq-Kuwait waters), three samples from the middle region of the Arabian Gulf (Bahrain-Qatar-Saudi Arabia) and two samples from the southern part of the Arabian Gulf/Sea of Oman (United Arab Emirates–Sultanate of Oman) suggested that there are three self-recruiting populations in the studied area. Inspection of the role of each meristic trait variable to Canonical discriminant analysis showed that changes among samples appeared to be linked with the pattern of distribution of water temperature and configuration of current in both the Arabian Gulf and Sea of Oman areas.     

Length‐weight relationships for five Clupeiformes species from the Persian Gulf and Oman Sea

Length‐weight relationships (LWRs) were determined for five Clupeiformes species representing three families collected from the Persian Gulf and Oman Sea. These are the first references on length‐weight relationships for two of these species (Ilisha megaloptera and Sardinella sindensis). A new maximum length record was obtained for one species (Ilisha melastoma).     

Hidden taxonomic characters in otoliths of blenniid fishes (Teleostei: Blenniidae) from the Iranian coasts of the Persian Gulf and Oman Sea ecoregions: A scanning electron microscopy approach

In the present work, the morphological characteristics of sagitta were described and analysed for 10 species of combtooth blennies (Blenniidae) inhabiting the intertidal region of the Persian Gulf and Makran zone of Oman Sea to see the taxonomic usefulness of otoliths, especially their hidden characters for species identification. Based on the obtained results, sagitta morphology could be considered as diagnostic characters distinguishing the genera Alticus, Antennablennius, Istiblennius, Omobranchus and Parablennius showing differences related to general shape, that is, elliptic/oval to triangular; shape of antirostrum and its degree of development; the degrees of convexity of ventral and dorsal margins, and shape of ostium. The common/general otolith characters shared in the all studied combtooth blennies, is the heterosulcoid condition, which is a shared character with Perciformes and Gobiiformes. The type of sulcus is ostial, and it can be considered as a plesiomorph character shared with a basal group of actinopterygian fishes. The obtained results could be useful in taxonomical, paleontological, ecological and food and feeding habits studies.     

mtDNA variation of the critically endangered hawksbill turtle (Eretmochelys imbricata) nesting on Iranian islands of the Persian Gulf

Genetic diversity of sea turtles (hawksbill turtle) was studied using sequencing of mitochondrial DNA (mtDNA, D-loop region). Thirty dead embryos were collected from the Kish and Qeshm Islands in the Persian Gulf. Analysis of sequence variation over 890 bp of the mtDNA control region revealed five haplotypes among 30 individuals. This is the first time that Iranian haplotypes have been recorded. Nucleotide and haplotype diversity was 0.77 and 0.001 for Qeshm Island and 0.64 and 0.002 for Kish Island, respectively. Total haplotype diversity was calculated as 0.69, which demonstrates low genetic diversity in this area. The data also indicated very high rates of migration between the populations of these two islands. A comparison of our data with data from previous studies downloaded from a gene bank showed that turtles of the Persian Gulf migrated from the Pacific and the Sea of Oman into this area. On the other hand, evidence of migration from populations to the West was not found.     

Molecular phylogeny of three mudskippers (Gobiidae) from the Persian Gulf and Gulf of Oman (Makran)

Presented is a phylogenetic reconstruction of mudskippers using sequences of the mitochondrial COI and cytb genes. The phylogeny combines the sequences of 12 species from GenBank with those of three species (Boleophthalmus dussumieri, Periophthalmus waltoni and Scartelaos tenuis) collected from the coastal area of the Persian Gulf and Oman (Makran) Sea and sequenced for the first time. Based on the Maximum likelihood and Bayesian methods, Periophthalmus forms a separate clade that is the sister lineage to a group formed by all remaining genera. The subfamilies Oxudercinae and Amblyopinae established on the basis of morphological characters have been shown to be paraphyletic and their use as taxonomic units is no longer recommended. The evolution of Periophthalmus waltoni, Periophthalmus barbarous and Boleophthalmus dussumieri is discussed based on molecular phylogenetic reconstruction.     

Chlorophyll <Emphasis Type="Italic">a</Emphasis> as a measure of seasonal coupling between phytoplankton and the monsoon periods in the Gulf of Oman

We present data from a long time-series study to describe the factors that control phytoplankton population densities and biomass in the coastal waters of Oman. Surface temperature, salinity, nutrients, dissolved oxygen, chlorophyll a (Chl a), and phytoplankton and zooplankton abundance of sea water were measured as far as possible from February 2004 through February 2006, at two stations along the southern coast of the Gulf of Oman. The highest concentrations of Chl a (3 mg m⁻³) were recorded during the southwest monsoon (SWM) when upwelling is active along the coast of Oman. However, results from our study reveal that the timing and the amplitude of the seasonal peak of Chl a exhibited interannual variability, which might be attributed to interannual differences in the seasonal cycles of nutrients caused either by coastal upwelling or by cyclonic eddy activity. Monthly variability of SST and concentrations of dissolved nitrate, nitrite, phosphate, and silicate together explained about 90% of the seasonal changes of Chl a in the coastal ecosystem of the Gulf of Oman. Phytoplankton communities of the coastal waters of Oman were dominated by diatoms for most part of the year, but for a short period in summer, dinoflagellates were dominant.     

An overview of Iranian mangrove ecosystems, northern part of the Persian Gulf and Oman Sea

Iranian mangrove forests occur between longitude 25°19′ and 27°84′, in the north part of the Persian Gulf and Oman Sea. In 2002, it was estimated that 93.37 km² of Iranian shorelines were covered with mangrove forests, with the largest area (67.5 km²) occurring between the Khamir Port and the northwest side of Qeshm Island, and the smallest area (0.01 km²) in the Bardestan estuary. Only two species of mangrove are found in the Persian Gulf: Avicennia marina from Avicenniaceae and Rhizophora macrunata from Rhizophoraceae. A. marina is the dominant specie in these forests whereas Rh. macrunata is found only in the Sirik region. Overexploitation of mangrove leaves and oil pollution are the main causes of mangrove destruction in this region.     

Length–weight and length–length relationships of three Blenny species from the Persian Gulf and the Gulf of Oman

The present study provides the length–weight and length–length relationships information (LWR & LLR) for three Blenny species; Antennablennius adenensis from the coast of Larak Island in the Persian Gulf and Istiblennius pox and Omobranchus mekranensis, which were captured in the coasts of Chabahar city in the Gulf of Oman, Iran. Total length (TL) and standard length (SL) were determined as well as weight. Specimens were collected occasionally in summer 2017 and winter 2018 by Hand net. The length–weight parameter b for these species was 2.84, 3.29 and 3.06 respectively with a high coefficient of determination (r² ≥ 0.95). All LLRs were highly correlated (r² > 0.99). All three species had no previous report for LWR and LLR estimates in FishBase.     

Fish communities on the world's warmest reefs: what can they tell us about the effects of climate change in the future?

To examine the role of climatic extremes in structuring reef fish communities in the Arabian region, reef fish communities were visually surveyed at four sites within the southern Persian Gulf (also known as the Arabian Gulf and The Gulf), where sea-surface temperatures are extreme (range: 12-35° C annually), and these were compared with communities at four latitudinally similar sites in the biogeographically connected Gulf of Oman, where conditions are more moderate (range: 22-31° C annually). Although sites were relatively similar in the cover and composition of coral communities, substantial differences in the structure and composition of associated fish assemblages were apparent. Fish assemblages in the southern Persian Gulf held significantly lower estimates of abundance, richness and biomass, with significantly higher abundances of smaller sized individuals than Gulf of Oman assemblages. Functionally, southern Persian Gulf sites held significantly lower abundances of nearly all the common fish trophic guilds found on Gulf of Oman sites, although higher abundances of herbivorous grazers were apparent. These results suggest the potential for substantial changes in the structure of reef-associated fish communities, independent of changes in habitat within an environment of increasing fluctuations in oceanic climate.     

Morphological variations of an invasive cyprinid fish (Carassius gibelio) in lentic and lotic environments inferred from the body,otolith, and scale shapes

This study investigated the morphological variation of gibel carp Carassius gibelio collected from various water bodies in Türkiye. The fish samples were obtained from three dams (Karacaören-1, Karakaya, and Keban), two natural lakes (Beyşehir and Suğla), and a river (the Tigris River). The dimorphism in body shape was examined with geometric morphometrics, while elliptic Fourier analysis and shape indices were used to describe the variation in lapilli otoliths (hereafter “otoliths”) and scale shapes. The body of C. gibelio revealed higher variations, particularly in the body depth, snout length, caudal fin, and caudal peduncle, among different stations. Geometric morphometric analysis determined a streamlined body shape of C. gibelio in the Tigris River compared to other stations, while C. gibelio from the natural lakes had a deeper body shape. The body of C. gibelio exhibited a significant homogenous shape between the Beyşehir and Suğla lakes, providing the lowest Procrustes distance. The elliptic Fourier analysis revealed that the otolith shape varied significantly between all stations. However, the scale shape was remarkably similar among nearby areas such as Karacaören dam, Suğla, and Beyşehir lakes. These results evinced high degree of intra-population morphological variation in C. gibelio in response to prevailing environmental conditions that probably facilitate their successful establishment in a novel environment.     

Macro- and microscopic morphology of the flank scales of families Lutjanidae and Serranidae from the Persian Gulf Coral Reefs (Teleosts: Perciformes)

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.     

Shell geometric morphometrics in Biomphalaria glabrata (Mollusca: Planorbidae) uninfected and infected with Schistosoma mansoni

Freshwater planorbid mollusks belonging to the genus Biomphalaria act as intermediate hosts for Schistosoma mansoni,the etiological agent of human intestinal schistosomiasis,in the Neotropical Region.Identification ofBiomphalaria spp.are carried out based on morphological characters,and the Schistosoma infection are determined by the presence of cercariae (verified through microscope preparation and mounting).Recently,the geometric morphometrics has proven to be a useful tool for determining shape differences in disease vectors arthropods.Due to this,we used geometric morphometrics to determine Biomphalaria glabrata shell differences (shape and size)between uninfected and infected specimens.We digitalized 12 anatomical points over the shell left side (from umbilicus to the last whorl) by combining type Ⅰ and Ⅱ landmarks and sliding semilandmarks;the coordinates were aligned by generalized Procrustes analysis.Principal component analyses were implemented for examining main variation axes,and discriminant analysis for testing group membership significance.We found significant separation between infected and uninfected shell conformation.All specimens were 100％correctly classified.The main differences occur in the peristome.The Kruskal-Wallis test finds significant differences in shell isometric size among infected and uninfected specimens.These findings correspond to other studies of traditional morphometrics,that infected snails showed the reduction in shell size in contrast to those uninfected specimens.     

Length–weight relationships of three fish species of coral reef fishes from the northeastern of the Persian Gulf

The investigation presents length–weight relationships for three coral reef fish species: Cephalopholis formosa (Shaw, 1812); Chaetodon nigropunctatus Sauvage, 1880; and Pomacanthus maculosus (Forsskål, 1775). The specimens were captured between April to August 2015 by spear‐gun and wire trap (mesh size: 35 mm) in coral reefs of the northeastern areas of the Persian Gulf.     

Phylogeography of Walton’s Mudskipper,Periophthalmus waltoni Koumans, 1941 (Perciformes: Gobiidae), from the Persian Gulf and Gulf of Oman

Mudskippers are amphibious air breathing fish with terrestrial adaptations in contrast to entirely aquatic fish. They are adapted to living on mudflats and show morphological, physiological, and behavioural features that could affect their phylogeny and phylogeography. A comparative genetic analysis was carried out on 100 specimens of the mudskipper Periophthalmus waltoni Koumans, 1941 from eight different sites along the coast of the Persian Gulf and Gulf of Oman. Phylogeographic inference based on two mitochondrial markers (Cyt b and D-loop) suggests that P. waltoni populations are divided into two well-divergent clades western and eastern. This is likely related to the geohydrological history of the area during the last Pleistocene glaciations. The regional phylogeographies are apparently also influenced by ecological and geographical barriers such as salinity, water current, and the geographic position of the Strait of Hormuz.     

Solea stanalandi,a new sole from the Persian Gulf

A new soleid flatfish,Solea stanalandi, is described from two specimens collected in 1–7 m in the Persian Gulf near Dhahran, Saudi Arabia. It is distinctive among species of the genus in having 57–59 dorsal rays, 46 anal rays, 104–106 pored scales in the straight portion of the lateral line to the caudal-fin base, a body depth of 2.45–2.5 in standard length, a large black spot on the outer half of the pectoral fin of the ocular side, and a similar narrower dark spot on the pectoral fin of the blind side.