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Gammarus (Crustacea: Amphipoda) are Gammaridae family that play an important role in food chain, environmental refining of organic matter and high sensitivity to environmental contamination. Therefore, it is important to identify them. Since the identification of the genus Gammarus is very difficult due to similar morphological features, the aim of the present study was to molecular identification and investigation of the phylogenetic relationships of G. komareki from the Jajrood River, east of Tehran compared to other parts of Iran and the rest of the world. For this purpose, sampling of G. komareki species in Jajrood River was done in season from October 2013 to July 2014. Samples were collected by a small manual tour. For molecular studies, some tissue was isolated from each sample with scalpel and fixed in 95% ethyl alcohol. The DNA of the samples was then extracted using the CTAB method and the gene fragment of a mitochondrial cytochrome oxidase (COI) subunit was amplified and sequenced. After gene fragment amplification and sequencing, Neighbor Joining and Maximum Likelihood trees were plotted using MEGA7 software. The results of the present study showed that although the specimens were morphologically belonging to Gammarus komareki species reported from other parts of Iran, Molecular studies showed that the samples of the present study were divided into two categories by being placed in two different clouds. Therefore, it is possible that these specimens may belong to separate species, which needs further investigation with other genetic markers.
 

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Epixanthus frontalis is the only known species of the genus Epixanthus from the Persian Gulf which include color polymorphic specimens. Considering that cryptic species are common among crustaceans, the aim of this study was to identify the cryptic species complexes the collected samples from the Persian Gulf. For this purpose, 4 colorful morphotypes of E. frontalis collected from rocky shores along Bushehr province. Then the first male gonopods was separated and photographed by scanning electron microscopy (SEM). For molecular studies samples of DNA extracted by using phenol-chloroform and mitochondrial cytochrome oxidase subunit gene segment (COI) was PCR and sequenced. The results showed that the nucleotide sequence of this gene fragment of the mitochondrial (COI) is not identical in all colorful morphotypes. These results reflected in the evolution of tree topology for all two analyses (maximum likelihood, bayesian). The study of apical ultrastructure segments of the first male species showed that it can be seen fundamental differences in the apical organs in some colorful morphotypes. Results of this study indicated that although the specimens assigned to single species morphologically, they may belong to different species based on their genotype. Further molecular studies with specific markers are needed for molecular identifications.