This study aimed to compare the species and functional diversity of macrobenthic communities between natural and planted mangrove ecosystems. Samples were collected from two mangrove sites in the Gulf of Oman. Physicochemical properties of water and sediment characteristics were analyzed to assess their correlation with community structure. Additionally, the effects of structural complexity and monsoon season were examined by sampling from vegetated and unvegetated habitats across two seasonal phases. A total of 71 species were identified. Species and trait composition significantly differed between the two sites, with the planted site characterized by a high dominance of grazing gastropods and the absence of polychaetes. Species composition was strongly correlated with sediment characteristics, with the planted site exhibiting coarser, sandy sediments and the natural site comprising mainly finer silt and clay. Functional and species diversity indices were generally lower in the planted site. Diversity indices were not consistently higher in vegetated habitats. The monsoon season increased diversity indices, but only in unvegetated habitats of the natural ecosystem. Our results suggest that while mangrove plantations contribute to ecosystem formation and biodiversity enhancement, they do not yet support communities as diverse as those in natural mangroves. Environmental conditions and possible pollution may be influencing these differences, requiring further investigation. Improved afforestation strategies, waste management, and long-term monitoring are essential for fostering resilient mangrove ecosystems.

Geological history, including tectonic activity and sea-level changes, dispersal capability, and habitat continuity, are among the key players in shaping the phylogeography of marine species. The Persian Gulf is a shallow semi-enclosed marginal sea in the northwestern part of the Indian Ocean with harsh physical conditions. A variety of population structures have been revealed for different taxa of this area. In this study, we aim to address the population structure and demography of the native intertidal mudflat crab, Nasima dotilliformis, along the Persian Gulf, the Strait of Hormuz, and the Gulf of Oman, using morphological and genetic analyses. Nineteen morphometric characters, carapace shape variations, and mitochondrial marker (COI) were analyzed. Morphometric and geometric-morphometric analyses revealed population differentiations among the three regions, with the Persian Gulf being more distinctive. Genetic comparisons also confirmed the partial isolation of the Persian Gulf from the other two regions. As this species is an obligate inhabitant of intertidal muddy substrates, we hypothesize that habitat discontinuity between stations in the Persian Gulf and the Strait of Hormuz may be the primary driver of this differentiation. Demographic analyses (mismatch distribution and neutrality tests) show evidence of strong genetic drift in this species along the study area. We hypothesize that this species may be experiencing a bottleneck effect as a result of population collapse during the Last Glacial Maximum (LGM) when their muddy substrate was scarce. We believe that our results provide new insights to be considered in conservation actions to protect such a native species which has been morphologically/genetically isolated in the Persian Gulf.

In this study, the instability of morphological characters in adult females of Parvocalanus crassirostris (F. Dahl, 1894) is evaluated. More than 28 types of fifth legs were observed in female individuals of P. crassirostris, showing variation in shape, segmentation, spine-like setae size, and the presence or absence of spines on the legs. Compared to other diagnostic characters, this trait is considered to have low value due to its observed morphological variations. Additionally, diversity was observed in the ornamentation of the outer border of exopods 2 (Exp2) and 3 (Exp3), with different serration patterns on the second to fourth legs. Molecular analysis using the partial CO1 gene showed that all individuals, regardless of intraspecific variation in the type of modified fifth legs, belong to P. crassirostris. All observed morphs are described in this study to provide informative data for evaluating diverse character types. Among state-of-the-art methods, the confocal laser scanning microscope was used to examine this phenotypic diversity and to explore the main patterns and hypotheses related to the factors possibly affecting morphological trait inconsistencies in this species.

Understanding the factors shaping species morphology and genetic differentiation across habitats with environmental stress gradients is crucial for predicting their responses to environmental change. The Persian Gulf and the Gulf of Oman, 2 marginal seas in the northwestern Indian Ocean, offer contrasting environments and oceanographic histories: the Persian Gulf is a shallow, semi-closed, and geologically young sea connected to the Gulf of Oman via the narrow Strait of Hormuz, while the Gulf of Oman is a deeper, open oceanic basin with more stable conditions. This study examines the brachyuran crab Parasesarma persicum to explore population structure across this environmental gradient. We utilized an integrative approach, combining mitochondrial DNA analyses with linear and geometric morphometrics. Our phylogeographic analyses revealed a degree of population differentiation between the 2 gulfs. Demographic analyses indicate a recent population expansion in the Gulf of Oman and suggest that the Persian Gulf population originated from a recent post-glacial colonization event. Morphological analyses showed divergence among populations, reinforcing the genetic findings. Habitat discontinuity between localities, restricted connectivity through the Strait of Hormuz, and hydrodynamic barriers like circular currents at the Persian Gulf's entrance likely drive this segregated structure. We also hypothesize that the extreme conditions of the Persian Gulf may impose selective pressures on P. persicum, leading to divergence. This study highlights the importance of historical events, geographic isolation, habitat connectivity, and potential natural selection in driving divergence in P. persicum, suggesting that similar processes may shape population structures in other species inhabiting muddy intertidal environments in this region.

Freshwater ecosystems are increasingly threatened by climate change and basin fragmentation, leading to significant biodiversity loss. To investigate these critical phenomena, scientists utilize specific animal species as effective ecological indicators, providing cost-effective assessments of ecosystems health and prompting strategies for environmental sustainability. We used Potamon strouhali populations as indicators to assess potential ecological changes in freshwater basins of the southern Zagros Mountains by employing integrative approaches. Haplotype network revealing nine distinct haplogroups, each characterized by unique haplotypes that do no overlap with others. An analysis of molecular variance (AMOVA) demonstrated significant genetic variation among populations (86.46 %) compared to within-population variation (0.6 %). Additionally, a time-calibrated phylogenetic tree based on COI and 16S sequences indicated that the divergence time of two distinct morphotype clades occurred approximately two million years ago, likely due to the emergence of Kazerun fault. We conducted an ecological identity test and variable importance analysis based on 80 presence localities across their distribution range, revealing minimal ecological overlap between the two morphological lineages. The limited haplotype diversity in P. strouhali populations suggests restricted gene flow, likely due to habitat fragmentation and harsh conditions, signaling ecosystem decline. Conservation efforts are urgently needed to protect biota and habitat diversity and integrity in the freshwater ecosystems, especially since regional extinctions have been observed.

The Persian Gulf is a shallow, semi-enclosed marginal sea basin characterized by a distinct geological history, harsh environmental conditions, and intermittent connection with the Indian Ocean during the Pleistocene glacial periods. Brachyuran crabs constitute a diverse component of the Persian Gulf fauna, distributed unevenly in the various habitats. The biodiversity and regional biogeographic data for the Persian Gulf and Gulf of Oman crab fauna are still poorly understood and rarely incorporated into global biodiversity databases. Here, we have addressed this shortfall by mapping the regional distributions of 262 species of brachyuran crabs in the Persian Gulf and the Gulf of Oman and incorporating the data with open-access biodiversity databases. We used QGIS 3.24.3 and R 4.2.2 packages for mapping and analyzing the distribution records. Our analyses revealed that the Persian Gulf exhibits proportionally higher diversity metrics than the Gulf of Oman for brachyuran crabs. Cluster analysis revealed that the Iranian coasts are relatively differentiated from the Arabian coasts of the Persian Gulf and the Gulf of Oman. The distribution and alpha species richness patterns per hexagonal cells were higher in the Iranian coastal waters, particularly around the Strait of Hormuz and Qeshm Island. Furthermore, the distribution and species richness of the Persian Gulf brachyuran crabs were positively correlated with temperature (degrees C) and calcite (mol.m-3), while negatively correlated with dissolved oxygen (mol.m-3). Although our analyses did not recognize the Persian Gulf as a center of endemism, but highlighted it as an important peripheral region with significant influences on the present-day diversity and distribution of northwestern Indian Ocean brachyuran crabs. We believe that the present results reveal new insights to be considered in conservation actions to protect marine biodiversity in underrepresented and ecologically unique regions such as the Persian Gulf.

Intertidal mudflats are highly productive ecosystems and contribute significantly to the coastal dynamics in the northwestern Indian Ocean. The endemic to the northwestern Indian Ocean crab, Leptochryseus kuwaitense, is the predominant species in this ecosystem and is responsible for most bioturbation through burrow construction. The present study aims to investigate the phylogeography of L. kuwaitense by collecting samples from five localities along the Persian Gulf and the Gulf of Oman, using COX1 sequences and geometric-morphometric analyses. Phylogeographic analyses revealed some degrees of genetic differentiation among the five localities, but did not detect any obvious geographic pattern, and no isolation was recovered between the Persian Gulf and the Gulf of Oman. Morphometric analysis also revealed no notable differences in shape between the two gulfs. This pattern of population structure is likely due to the disconnection between the sheltered mudflats, the typical habitat of L. kuwaitense, along the studied localities. The lack of geographic pattern in the genetic structure is probably imposed by the complex surface currents in this area. Demographic results indicate a recent population expansion for L. kuwaitense along the northwestern Indian Ocean. The Bayesian Skyline Plot revealed that the increase in effective population size happened during the last glacial maximum, through which a large proportion of mudflats in the northwestern Indian Ocean were unsuitable for this crab.

The current patterns of biodiversity have significantly been affected by glacial-interglacial cycles during the Pleistocene period. True freshwater crabs are considered as poor dispersers and terrestrial barriers restrict gene flow between their local populations. Recent studies, however, suggest that certain environmental conditions, such as periods of heavy rainfall and humidity, can facilitate their between-drainage dispersal and will result in the evolution of homogenous genetic patterns among different drainage systems. Here we tested this hypothesis by comparing populations of the endemic freshwater crab Potamon elbursi Pretzmann, 1962 distributed in two drainage systems, the Caspian Sea and Namak Lake, in northern Iran. Our results based on the genetic analysis of 70 new and 61 previously published sequences of the mitochondrial cytochrome oxidase subunit I gene revealed a substantial haplotype diversity in some populations and high levels of local population structuring in others. Initially, we found mixed evidence of genetic differentiation and connectivity among drainages and populations. Genetic differentiation between the two drainages only became apparent after the Sepirdood population (which belongs to the Caspian Sea drainage) was excluded. Subsequently, the two drainages showed significant genetic distinctions, with a limited gene flow between them. Our demographic analyses supported recent population bottlenecks, followed by a rapid demographic and/or spatial expansion dating back to the Pleistocene climatic fluctuations. Species distribution modelling suggests that precipitation during warm weather conditions profoundly affects the distribution of P. elbursi. This study indicates that freshwater crabs can override short land barriers under favorable weather conditions and will have conservation implications in the face of contemporary climatic fluctuations.

The freshwater crab Potamon persicum Pretzmann, 1962 in Iran is distributed along the western Alborz Mountains, its range extending southeast through the whole Zagros Mountains. We expected a high geographic differentiation within Potamon persicum between the main drainage systems in the region (Khalij Fars-Oman, Markazi and Urmia basins). To test this hypothesis, we conducted conventional morphometric and geometric-morphometric analyses. Comparison of males and females between populations of three main drainage systems showed significant differences of eleven traits. We also detected significant sex-specific differences among the three main drainage systems. The results are supported by geometric-morphometric analysis of the carapace shape, as carapace shape varies between sex and populations of three main drainage systems. Based on both analyses, populations of Khalij Fars-Oman and Markazi basins are similar to each other. Furthermore, a higher differentiation was seen between populations from Markazi and Urmia basins. We hypothesize that the P. persicum geographic differentiation is a result of both isolation by topography and climate during the Pleistocene glacial periods.

Understanding the patterns and drivers of biodiversity in intertidal zones is essential for developing effective conservation strategies. The taxonomic and functional diversity of macrofaunal communities was studied in the arid mangrove system of the Persian Gulf and Gulf of Oman. The study further aimed to investigate whether the main functional traits differ between habitats. All macrofauna samples and environmental variables were taken from two habitats including vegetated habitat and adjoining mudflats. A total of 85 taxa was found, of which 19 taxa were exclusive to vegetated habitats and 20 to mudflats. Mollusca were the most species-rich group in both habitats, followed by Arthropoda and Annelida. When comparing diversity indices among regions and habitats the Shannon-Wiener diversity index was significantly higher in vegetated habitats compared to mudflats. However, these trends were less consistent for the functional diversity measures being very much region-dependent. The results showed that functional trait structure was more uniform than the taxonomic structure across regions and habitats. The trait modalities biodiffuser, surface deposit-feeder, burrower, free-living, planktotrophic, 2-5 years, and 10-50mm were common at both habitats. However, the modalities detritivore and grazer/scarper, and direct larval development were significantly higher in vegetated habitats than in mudflats. The vegetated habitats exhibited the more functionally redundant communities than mudflats, possibly due to higher taxonomic diversity observed in this habitat or the presence of the species with similar functions in the ecosystem. The combined investigation of species and functional diversity of mangrove macrofauna communities conducted in this research is essential for effective management and conservation efforts aimed at protecting mangrove ecosystems and to preserve the goods and services they provide.

Abstract The tropical Indo-West Pacific (IWP) is one of the species-rich and high endemicity hotspots around the East Indies Triangle. However, recent research demonstrates that peripheral regions may act as evolutionary incubators, sharing unique genetic lineages with other regions of the IWP. The Persian Gulf is a shallow semi-enclosed marginal sea basin characterized by geological history, stressful environmental conditions, and intermittent connection with the Indian Ocean during the Pleistocene glacial periods. Understanding the global distribution and importance of environmental variables in shaping species richness patterns of brachyuran crabs in this region is necessary for comprehending evolutionary and ecological processes, as well as conservation priorities. We merged our own distribution dataset of 261 species of brachyuran crabs in the Persian Gulf and Gulf of Oman with the GBIF and OBIS open-access biodiversity datasets, which lack the data from this region. QGIS 3.24.3 and R 4.2.2 packages were used for data analysis and visualization of the distribution records. The highest sampling effort (1,955), species richness (225 spp.) and ES50 (expected number of species) (40.94), along with 21 endemic species of brachyuran crabs were observed in the Persian Gulf. Distribution and species richness of brachyuran crabs significantly increased with temperature (°C) and calcite (mol.m-3), and decreased with dissolved oxygen (mol.m-3), and nitrate (mol.m-3), the focus of this study. This study suggested that the Persian Gulf, as a peripheral region, may play a role in shaping brachyuran diversity and current species distribution. This highlights the importance of prioritizing marine protected areas and establishing species management in this economically and ecologically important region.

This taxonomic study describes Liomera schubarti n. sp., a newly discovered xanthid crab inhabiting live coral in the Persian Gulf. The new species shares a general resemblance with four other species of this genus, L. bella, L. margaritata, L. rugata and L. yaldwyni, particularly in carapace morphology, but it can be distinguished by the fusion of carapace areolets, specific pattern of granules on the outer surface of the chela and the unique structure of the male first gonopod. This contribution enriches our understanding of the xanthid crab diversity in the Persian Gulf.

Understanding population dynamics requires knowledge of reproductive aspects such as sexual maturity, fertility, and growth changes of body components. We analyzed the relative growth and morphometry in a native brachyuran crab, Leptochryseus kuwaitense (Jones & Clayton, 1983), that dominates mud flats along the Iranian coast of the Persian Gulf and Gulf of Oman. The carapace (length, width, height, front), pleon (abdomen) (length and width of the first, third, fifth, and sixth segments), second, third, and fourth walking legs (total length, length, and width of the merus), cheliped propodus (length and width), and eye dimentions (distance between the two eyes and eye-stalk length), and total weight were recorded for 83 specimens. A regression model with a segmented relationship was employed to examine the relative growth patterns of the characteristics in question. The breakpoints identified in the analysis provided insights into the body size at which crabs attain sexual maturity. The carapace length of sexual morphometric maturity in males and females was 20.43 mm and 19.20 mm, respectively. Males exhibited a positive allometric growth for most traits, with adults having a greater slope than juveniles with the exception of body height, weight, and in some traits (e.g., cheliped length and width) this slope is more than double. By contrast, the growth equation for females is positive allometric for the majority of traits in juveniles, whereas were negative allometric in mature individuals. Juvenile individuals of both sexes exhibited morphological similarities, but females tended to have a smaller body size compared to males. The carapace length of the largest male was 24.2 mm (with mean of 21.71 mm, N = 43), 21.7 and (with mean of 20.14 mm, N = 40) for females, a characteristic that is likely associated with their reproductive biology. Because males are larger in body size, energy investment in the growth of walking legs and chelipeds may be crucial for mating and intreasexual cambating. The rate of growth thus exhibited a more rapid increase in males. Our results indicate that the chelipeds do not play a role in combat, but the coloration of the male cheliped plays a role in its selection by females.

Understanding population dynamics requires knowledge of reproductive aspects such as sexual maturity, fertility, and growth changes of body components. We analyzed the relative growth and morphometry in a native brachyuran crab, Leptochryseus kuwaitense (Jones & Clayton, 1983), that dominates mud flats along the Iranian coast of the Persian Gulf and Gulf of Oman. The carapace (length, width, height, front), pleon (abdomen) (length and width of the first, third, fifth, and sixth segments), second, third, and fourth walking legs (total length, length, and width of the merus), cheliped propodus (length and width), and eye dimentions (distance between the two eyes and eye-stalk length), and total weight were recorded for 83 specimens. A regression model with a segmented relationship was employed to examine the relative growth patterns of the characteristics in question. The breakpoints identified in the analysis provided insights into the body size at which crabs attain sexual maturity. The carapace length of sexual morphometric maturity in males and females was 20.43 mm and 19.20 mm, respectively. Males exhibited a positive allometric growth for most traits, with adults having a greater slope than juveniles with the exception of body height, weight, and in some traits (e.g., cheliped length and width) this slope is more than double. By contrast, the growth equation for females is positive allometric for the majority of traits in juveniles, whereas were negative allometric in mature individuals. Juvenile individuals of both sexes exhibited morphological similarities, but females tended to have a smaller body size compared to males. The carapace length of the largest male was 24.2 mm (with mean of 21.71 mm, N = 43), 21.7 and (with mean of 20.14 mm, N = 40) for females, a characteristic that is likely associated with their reproductive biology. Because males are larger in body size, energy investment in the growth of walking legs and chelipeds may be crucial for mating and intreasexual cambating. The rate of growth thus exhibited a more rapid increase in males. Our results indicate that the chelipeds do not play a role in combat, but the coloration of the male cheliped plays a role in its selection by females.

Palapedia schubarti n. sp. is the third species of the genus Palapedia , described from the northwestern Indian Ocean. Two species, P. persica and P. apeli , had already been recorded from the Persian Gulf, and the new species is described from farther south in Socotra Island. Palapedia persica has appendages markedly ornamented with large denticles, while P. apeli has distinctly smooth appendages. Compared to the two above-mentioned species, the new species has an intermediate position regarding the spination, with small denticles on the upper margin of the palm, fingers and anterior margin of walking legs. The morphology of the first male gonopod of P. schubarti n. sp. is very close to P. rastripes , described from Ceylon, and P. truncatifrons described from Japan. The new species, however, is easily distinguishable from those two congeners in having a spade form ending and several other characteristics of chelipeds and carapace.

This study reports the first record of two brachyuran crab species, Austruca albimana Kossmann, [21] and Tirmilyra concinnus Ghani and Tirmizi [18], from the western Indian coast. Their identification, taxonomic observations, and geographic distribution are provided. The species belong to the families Ocypodidae and Leucosiidae, respectively. This is the first report from Indian waters, as the species are so far reported from Oman, Iran and Persian Gulf. These records emphasize the need for research and conservation efforts in the region to explore the diversity and distribution of brachyuran crabs in Indian waters.

Abstract Understanding population dynamics requires knowledge of reproductive aspects such as sexual maturity, fertility, and growth changes of body components. We analyzed the relative growth and morphometry in a native brachyuran crab, Leptochryseus kuwaitense (Jones & Clayton, 1983), that dominates mud flats along the Iranian coast of the Persian Gulf and Gulf of Oman. The carapace (length, width, height, front), pleon (abdomen) (length and width of the first, third, fifth, and sixth segments), second, third, and fourth walking legs (total length, length, and width of the merus), cheliped propodus (length and width), and eye dimentions (distance between the two eyes and eye-stalk length), and total weight were recorded for 83 specimens. A regression model with a segmented relationship was employed to examine the relative growth patterns of the characteristics in question. The breakpoints identified in the analysis provided insights into the body size at which crabs attain sexual maturity. The carapace length of sexual morphometric maturity in males and females was 20.43 mm and 19.20 mm, respectively. Males exhibited a positive allometric growth for most traits, with adults having a greater slope than juveniles with the exception of body height, weight, and in some traits (e.g., cheliped length and width) this slope is more than double. By contrast, the growth equation for females is positive allometric for the majority of traits in juveniles, whereas were negative allometric in mature individuals. Juvenile individuals of both sexes exhibited morphological similarities, but females tended to have a smaller body size compared to males. The carapace length of the largest male was 24.2 mm (with mean of 21.71 mm, N = 43), 21.7 and (with mean of 20.14 mm, N = 40) for females, a characteristic that is likely associated with their reproductive biology. Because males are larger in body size, energy investment in the growth of walking legs and chelipeds may be crucial for mating and intreasexual cambating. The rate of growth thus exhibited a more rapid increase in males. Our results indicate that the chelipeds do not play a role in combat, but the coloration of the male cheliped plays a role in its selection by females.

The Zagros Mountains, characterized by complex topography and three large drainage systems, harbor the endemic freshwater crab Potamon persicum in Iran. Our study delves into the evolutionary history of P. persicum, utilizing two mitochondrial and one nuclear marker. We collected 214 specimens from 24 localities, identifying 21 haplotypes grouped into two major evolutionary lineages. Substantial differentiation exists between drainage systems and lineages. Historical demographic analysis revealed a significant decrease in population size during the late Holocene, accompanied by a recent population bottleneck. Species distribution modeling has revealed eastward shifts in suitable habitats between the last glacial maximum and the present day. Following the last glacial maximum, habitat fragmentation occurred, resulting in the establishment of small populations. These smaller populations are more vulnerable to climatic and geological events, thereby limiting gene flow and accelerating genetic differentiation within species. Historical biogeographic analysis traced the origin of P. persicum to the western Zagros Mountains, with major genetic divergence occurring during the Pleistocene. Our genetic analyses suggest that P. persicum may have shown a genetic pattern similar to a classical ring species before the Pleistocene. The Namak Lake sub-basin could have served as a contact zone where populations did not interbreed but were connected through gene flow in a geographic ring. Currently, genetic separation is evident between basins, indicating that P. persicum in the Zagros Mountains is not a contemporary ring species. Also, our biogeographical analysis estimated that range evolution may have been driven initially by dispersal, and only during the late Pleistocene by vicariance.