---

This study was carried out to comparison and survey on metazoan parasites of Otolithes ruber in coastal waters of Persian Gulf and Sea of Oman. Totally 318 fish specimens were seasonally caught by gill net, bottom trawl and hook in Khozestan, Hormozgan and Sistan and Baluchestan Provinces from summer 2013 to spring 2014. Specimens immediately were frozen and transferred to laboratory and after measuring fish weight and length, parasitological survey conducted on external and internal organs. Totally, 20 different parasites species were observed from O. ruber in mentioned areas that some of them occurred in all three regions and the others were only in one or two areas. The results of this study showed that monogeneans and digeneans had the highest occurrence in three regions while other groups were less abundant in each area. The results of statistical analyses showed significant differences among parasites abundance in different seasons. As well as a significant differences were found between male and female and parasites abundance of Digenea in Khozestan, Monogenea and Cestoda in Hormozgan and Nematoda in Sistan and Baluchesta Provinces. The prevalence of parasites depends on environmental conditions and presence of intermediate hosts that these factors are likely to be different in the three regions.

---

In this study, gonad structure and oogenesis of ghost crab were studied based on macroscopic and microscopic analyses from January 2016 to February 2017. Female crabs were collected from sandy beach of Salahk port, Qeshm Island, monthly. In the laboratory, the crabs’ ovaries were dissected and prepared for histology. Based on external and morphological features, gonad developmental stages were investigated and afterwards each stage was microscopically described. According to the results, six ovarian developmental stages were recognized including: stage I: immature, stage II: rudimentary, stage III: developing, stage IV: intermediate, stage V: advanced, stage VI: spent. During oogenesis, the number of oocytes in secondary growth increased in the ovaries which was associated with a change in coloration and increase in the gonad volume. Oocytes growth process was classified in six stages: early primary growth, late primary growth, early secondary growth, mid-secondary growth, late secondary growth, and full-growth. According to results, shaping of perinuclear yolk complex observed just in late primary growth stage. Furthermore, starting of second growth was simultaneous to appearing of yolk globules in ooplasm. Also, most of oocytes were visible as light pink in full-Grown stage.
 

---

The present study aimed to identify, introduce and compare pseudoparasites in wild fish (Rutilus kutum and Mugilidae) and cage culture rainbow trout (Oncorhynchus mykiss) in the southern coast of the Caspian Sea. Wild fish specimens were collected from four stations in Anzali, Kiashahr, Chalus, Mahmoud‌abad and rainbow trout in three cages of Kiashahr, Abbas‌‌‌‌‌abad and Si-Sangan. After transferring the specimens to the laboratory, they were bio‌assayed and parasitological examination was performed on all internal and external organs. Free-living nematodes, pine pollen, pollen grain, protozoa, fungal spores, plant seeds, and filaments were isolated from fish as pseudoparasites. The highest percentage of pseudoparasites belonged to Pine pollen and was found in almost all fish organs. Free-living nematodes were isolated from the stomach, intestine, gills and Pollen grain from the liver, spleen, and kidneys of fish. Pseudoparasites are widespread in addition to they may be transmitted by food or randomly to fish. Pseudoparasites do not cause infection and disease in their host. Investigating and understanding them because of their importance in the parasitology can be useful for parasitologists and fish farmers to avoid the futile consumption of pharmaceuticals.
 

---

According to the importance and position of fish for human protein supply, studying pathogens and more familiarity with their parasitic diseases can be a step towards improving the knowledge of parasitology in the country. The aim of this study was to identify the metazoan parasites of the Indian mackerel (Rastrelliger kanagurta) caught from the coasts of the Oman Sea in the Chabahar region. In the present study, 61 pieces of R. kanagurta were caught in summer 2019. The fish were transported to the laboratory and their length and weight were measured. Different organs of the fish such as gills, eyes, stomach, pyloric caeca, gonads, and intestines were examined for isolated parasites were stabilized in alcohol 70% and/or formalin 10%. The identified parasites were from the digene category and including Lecithocladium angustiovum and prodistomum orientale with frequency of 100% and 26.4%, respectively, from the category of monogenic parasites, Indomazocraes sp. And another example of the family Mazocraeidae, both with prevalence of 1.9% and from the nematode genus, the larvae of the parasite Anisakis sp. were identified with a prevalence of 1.9%.The results showed that the digenean parasite Lecithocladium angustiovum had the highest severity of infection in the stomach (16.1±17.3). In this study, according to the results, the identified parasites included two digens at the genus and species levels, a monogenean at the genus level and another in the family of flatworm branches, a nematode at the genus level in roundworm branch. This is the first report of the Indian mackerel parasites from the Oman Sea coast. Also, the parasites of Prodistomum orientale, Indomazocraes sp. and a specimen belonging to the family Mazocraeidae are reported for the first time of this fish from the coasts of Iran.

---

The purpose of this study was to investigate the infestation of Portunus segnis with symbiotic organisms to determine the abundance, prevalence, and intensity of the infestation. A total of 86 blue swimming crabs were collected from Bandar Abbas coast during Summer and Autumn, 2018. Totally, 473 symbionts including Lepas anserifera, Chelonibia testudinaria, Philometra sp., Microstella norvegica, two unidentified species of order Cyclopoida, unidentified species of Ostracoda and Bivalvia were isolated. The prevalence of infection was 66.59, 1.47, 53, 13.5, 5.91, and 12.47%, respectively. Except for C. testudinaria, other taxa are reported for the first time in P. segnis and the Persian Gulf during this study. The intensity of infestation in both males and females did not show a significant difference, therefore, it can be concluded that this factor is not affected by gender in blue swimming crab. The intensity of infestation in autumn was approximately, four times more than summer (21 and 5.84, respectively). It is probably because of the suitable conditions and the larger size of the host in this season. Moreover, intensity of infestation in cluster 2 was almost four times more than in cluster 1, confirming the positive effect of size on the abundance of symbionts in P. segnis.