The decapod crustaceans of the Gulf of Oman have been documented based on the published literature and new sampling along the Iranian coast between 2005 and 2015. A total of 121 species were collected along the Iranian coast, of which 43 are new records for the Gulf of Oman. The Decapoda of the Gulf is currently represented by 258 species belonging to five infraorders: Axiidea, Achelata, Anomura, Brachyura, and Caridea. Brachyura, with 176 species, are the best represented group, followed by Anomura and Caridea with 42 and 17 species, respectively. The least diverse groups are Achelata, with five species, and Axiidea, with three. On the basis of the available information, the northern (Iranian) coast with 189 species is more diverse than the southern (United Arab Emirates and Oman) coast with 134 species.

The present annotated checklist contains 43 species of thoracican barnacles known to date from the area, 33 and 26 from the Persian Gulf and the Gulf of Oman, respectively. Nine species are new records for the area including Amphibalunus subalbidus (Henry, 1973), Armatobalanus allium (Darwin, 1854), Chelonibia patula (Ranzani, 1818), Conchoderma hunteri (Owen, 1830), Lepas anserifera Linnaeus, 1767, Lithotrya valentiana Reinhardt, 1850, Megabalanus coccopoma (Darwin, 1854), Megabalanus occator (Darwin, 1854) and Platylepas hexastylos (Fabricius, 1798), of which A. subalbidus and M. coccopoma are reported as alien species from the region.

The marine environment of the Persian Gulf is characterized by extreme biophysical factors, like high salinities. This gulf is a semi-enclosed basin and is connected to the Gulf of Oman via the narrow Strait of Hormuz that may act as a barrier to gene flow between the two gulfs. Consequently, animal populations living in the Persian Gulf are hypothesized to be isolated and thus to evolve independently from neighbouring populations. We tested this hypothesis with the xanthid crab,Leptodius exaratus(H. Milne Edwards, 1834), which is one of the most common intertidal crabs occurring in the Persian Gulf and the Gulf of Oman. Four-hundred-and-fifty specimens were collected from eight sampling sites, i.e., four sites each in the Persian Gulf and the Gulf of Oman. Fifteen morphometric characters were measured. Males and females were analysed separately to avoid bias as a consequence of sexual dimorphism. Due to the lack of normal distribution in males, two different approaches were carried out in this paper. Female specimens were included in parametric analyses, while males were tested with permutational multivariate analyses of variance. In female morphometric characters,t-test analyses showed significant differences between the two sets of populations, and the discriminant analysis showed divergence between the two groups (with 83% correct groupings). In the males, the applied analyses showed a significant difference () between the two gulfs. These divergences can be interpreted as a consequence of regional adaptations and a low rate of larval migration between the two gulfs.

Mangrove crabs are important components of mangrove forests however their large scale habitat suitability and conservation received little attention. The Metopograpsus thukuhar/cannicci species complex is a mangrove dwelling species occurs in the Indo-Pacific mangrove forests. Since identifying the complex suitable habitat is critical for its conservation, we modeled global habitat suitability of the complex within marine biogeographic realms and estimated representation of the complex suitable habitats within marine protected areas. We found that the complex’ largest and smallest suitable ranges are located in Central Indo-Pacific and Temperate Southern Africa realms, respectively. Only 12.5% of the complex suitable habitat is protected. The highest proportion of the complex’ protected suitable habitat (22.9%) is located in Western Indo-Pacific realm while the lowest proportion of the complex’ protected suitable habitat (1.38%) is located in Central Indo-Pacific realm. Suitable unprotected habitats of the complex identified in this study have high priority for conservation and should be included in marine protected areas to ensure species conservation. Our results show that species distribution models are practical tools to study marine species distribution across large spatial scales and help marine conservation planning.