The Copepods distribution in the southern Caspian Sea at 18 semi-transect and 80 sampling station was investigated in 1995. In this survey, three sub-order, Calanoida, Cyclopoida and Harpacticoida were identified. Calanoids constituted the main population of copepods; normally over 90% of the total population of copepods was related to this sub-order.Copepods are the main population of the sea zooplankton. In spring, autumn and winter, COPEPODA had the main role in the formation of zooplanktonic population, but in summer, other species in addition to copepods affected the zooplanktonic population. In summer, most probably due to the increase in temperature and inlet of organic matters from rivers, species other than copepods grow in coastal regions. The copepods population in spring and summer was from 1949 to 16996 N/m3 and 6902 - 15032 N/m3, respectively; in autumn and winter it was from 9724- 32940 N/m3and 2965 - 13335 N/m3, respectively. The copepods diverse in more than 100m depth and their maximum population were in 10 and 20m layers.

Background and Objectives: Lake Tar is situated at an altitude of 3,230 meters above sea level and is surrounded by mountains ranging from 50 to 500 meters in height above the lake. The existence of these elevations next to each other, without a valley splitting them, has created a depression in which Lake Tar has formed. Crustacean zooplankton, especially Cladocera, play a significant role in most freshwater lakes and have become important bioindicators for assessing water quality and ecosystem health due to their sensitivity to environmental changes. Therefore, this study was conducted regarding the diversity and ecology of various microcrustacean species in the mountain lake Tar. Methods: In this study, sampling was conducted monthly along three stations from April to September 2021, and environmental parameters including water temperature, pH, electrical conductivity (EC), and dissolved oxygen (DO) were measured on-site. Additionally, for quantitative analysis, zooplankton were collected by filtering 100 liters of water through a 100-micron plankton net during each sampling. Findings: In Lake Tar, during the studied months, dissolved oxygen (DO) levels were high, with the highest value reaching a maximum of 13 milligrams per liter in April. The pH values varied between 7.23 and 8.3 during the study period, indicating alkaline values and a low range of variability influenced by snowmelt and the geology of the surrounding environment. Meanwhile, the values and seasonal patterns of environmental parameters fell within the range characteristic of oligotrophic lakes. Additionally, during the ice-free months in Lake Tar, three species of Daphnia and four species of cyclopoid were identified. Daphnia laevis and Daphnia ambigua were recognized as the most common and abundant recorded crustacean species. The identified cyclopoid species included Cyclops scutifer, Cyclops latipes, Cyclops venustus, and Cyclops exilis. In the crustacean community of Lake Tar, the abundance of adult cyclopoid copepods was significantly less than that of Cladocera (43 individuals per cubic meter). Despite the dominance of Cladocera, the average population density of Daphnia species reached a maximum of 480 individuals per cubic meter, which is within the density range of Cladocera in oligotrophic mountain lakes. The results also indicated that Lake Tar is a typical Cladocera-copepod lake and specifically a typical Daphnia-Cyclops Lake, in which planktivorous fish are absent. Conclusion: In this small and remote lake, most factors that can affect the presence and distribution of zooplankton are temporally variable and unpredictable. The results regarding the composition of Cladocera and Copepod crustaceans included the first records of Daphnia laevis, Daphnia ambigua, Cyclops scutifer, Cyclops latipes, Cyclops venustus, and Cyclops exilis in Iran, highlighting the important role that specific mountain lakes can play as aquatic biodiversity reserves. Ultimately, it seems that these natural, ancient, and unique lakes require greater efforts in research and monitoring, including studies related to vertical migrations and the adaptive mechanisms of crustacean communities during freezing periods. Background and Objectives: Lake Tar is situated at an altitude of 3,230 meters above sea level and is surrounded by mountains ranging from 50 to 500 meters in height above the lake. The existence of these elevations next to each other, without a valley splitting them, has created a depression in which Lake Tar has formed. Crustacean zooplankton, especially Cladocera, play a significant role in most freshwater lakes and have become important bioindicators for assessing water quality and ecosystem health due to their sensitivity to environmental changes. Therefore, this study was conducted regarding the diversity and ecology of various microcrustacean species in the mountain lake Tar. Methods: In this study, sampling was conducted monthly along three stations from April to September 2021, and environmental parameters including water temperature, pH, electrical conductivity (EC), and dissolved oxygen (DO) were measured on-site. Additionally, for quantitative analysis, zooplankton were collected by filtering 100 liters of water through a 100-micron plankton net during each sampling. Findings: In Lake Tar, during the studied months, dissolved oxygen (DO) levels were high, with the highest value reaching a maximum of 13 milligrams per liter in April. The pH values varied between 7.23 and 8.3 during the study period, indicating alkaline values and a low range of variability influenced by snowmelt and the geology of the surrounding environment. Meanwhile, the values and seasonal patterns of environmental parameters fell within the range characteristic of oligotrophic lakes. Additionally, during the ice-free months in Lake Tar, three species of Daphnia and four species of cyclopoid were identified. Daphnia laevis and Daphnia ambigua were recognized as the most common and abundant recorded crustacean species. The identified cyclopoid species included Cyclops scutifer, Cyclops latipes, Cyclops venustus, and Cyclops exilis. In the crustacean community of Lake Tar, the abundance of adult cyclopoid copepods was significantly less than that of Cladocera (43 individuals per cubic meter). Despite the dominance of Cladocera, the average population density of Daphnia species reached a maximum of 480 individuals per cubic meter, which is within the density range of Cladocera in oligotrophic mountain lakes. The results also indicated that Lake Tar is a typical Cladocera-copepod lake and specifically a typical Daphnia-Cyclops Lake, in which planktivorous fish are absent. Conclusion: In this small and remote lake, most factors that can affect the presence and distribution of zooplankton are temporally variable and unpredictable. The results regarding the composition of Cladocera and Copepod crustaceans included the first records of Daphnia laevis, Daphnia ambigua, Cyclops scutifer, Cyclops latipes, Cyclops venustus, and Cyclops exilis in Iran, highlighting the important role that specific mountain lakes can play as aquatic biodiversity reserves. Ultimately, it seems that these natural, ancient, and unique lakes require greater efforts in research and monitoring, including studies related to vertical migrations and the adaptive mechanisms of crustacean communities during freezing periods.

This survey was carried out by R/V Guilan ship with a conical plankton net of 100 micron mesh by vertical hauls at different stations and depths of 5, 10, 20, 50 and 100m in 2010. In this study, 16 species formed the zooplankton community including 4 species of COPEPODA, 4 species of Rotatoria, 2 species of Protozoa and 4 species of Cladocera from Holoplanktons and 2 species of Balanus sp and Lamellibranchiata larvae from Meroplanktons. The annual results revealed that the mean abundance of zooplankton were 5477±5815 ind/m3 in spring but the maximum biomass (64.58±124.61mg/m3) was in winter that was affected by Rotatoria. The maximum mean abundance and biomass of COPEPODA were in summer that were 2830±2342 ind/m3 and 22.52±21.78 mg/m3, respectively and the abundance decreased gradually since autumn and reached the least in winter but increased since spring. The mean maximum abundance of Cladocera (115±142 ind/m3) was in spring but it gradually decreased, The Protozoa constituted the least community and biomass of zooplankton in southern area of Caspian Sea. The zooplankton community also was affected by Meroplanktons including Cirripedia and Lamellibranchiata Larvae in spring and the Rotatoria contributed highly in zooplankton community in winter with the mean abundance and biomass of 2604±5876 ind/m3 and 50.71±115.33 mg/m3 respectively. It was observed the reduction trend in abundance from surface depths to deeper depths in whole of the year. There were 75% of zooplankton community in stations with 5 to 20m depth and 25% of community in stations with 50 to 100m depth in spring, and also 74% in stations with 5 to 20m depth and 26% in stations with 50 to 100m depth in summer, 73% in stations with 5 to 20m depth and 27% in stations with 50 to 100m depth in autumn and 85% in stations with 5 to 20m depth and 15% in stations with 50 to 100m depth in winter. In analysis of different area of southern basin of Caspian sea the maximum abundance was observed in west in spring, summer and winter which were 7514±8115 ind/m3, 3909±2609 ind/m3 and 8129±11587 ind/m3, respectively. There was 2283±2134 ind/m3 in center area in autumn. The annual statistical analysis revealed that, there was significant difference in total zooplankton community between sampling stations, depths and layers in whole of the year.

The purpose of this study was to identify and investigate the density and distribution of COPEPODA and cladosera and the structural analysis of their dominant species in the Arvand river by SEM (scanning electron microscope). Sampling was conducted with 50 μ m mesh size plankton net at 6 stations and four times (in different seasons) with three reputation. The samples were detected by phase contrast microscopy and SEM. Totally 15 species of COPEPODA and 5 species of cladocera were identified in the river. The highest density of planktonic crustaceans including COPEPODA and cladocera with a mean density of 9481 and 3155 individuals per cubic meter was calculated in summer. These species, Acartia faoensis, Canthocalanus pauper, Subecalanus flemingeri, Labidocera acuta, which accounted for 61% of the total copepods abundance and 54% of the cladosera abundance were related to Moina macrocopa and Daphnia longisoina. The integrity of the river were studied using saprobic index, which showed mesosaprobic-β (medium pollution) with mean 2. 48 points.

The study was carried out to investigate a heavy outbreak of crustacean parasiteLernaea cyprinacea in fishes from Choghakhor Lagoon in spring and summer 2008 following the report of natives and fishermen on the mortality of fishes in the Lagoon. Sixty five fish from different species were studied which 49 fish (75.38 percent) found to be invaded by Lernaea and 16 fish (24.62 percent) didn’t show any parasitic infection sign. The highest infection rate was observed in Capoeta damascina. The results also showed that there is no significant relation between infection rate with weight and age of fishes. The site specifity of the parasite was also studied and the highest number of parasites were found on the base of pectoral fin and the lowest were observed on the head and operculum and the differences was statistically significant (p<0.05).

The aim of this investigation was to study the Calanoid Copepods density and diversity in Bahrakan waters (Hendijan Harbor, Persian Gulf, Iran). Sampling was conducted during July, August and October 2010 and December, February and April 2011. Zooplankton were collected with plankton tows using 100- μm mesh net. Environmental parameters including salinity, temperature and dissolved oxygen were measured. In this study, 16 species of Calanoids were identified, among them; Acartiella faoensis with relative frequency of 28% was the most abundant species during the studying period. This species was first reported from the Persian Gulf Iranian waters. The Calanoid density was highest in August and lowest in December and February. There was Positive significant correlation coefficient between density of Calanoids and water temperature (P<0.05). The Shannon diversity index was maximum in July and ranged from 0. 98 to 2. 42 during the year.

Infection with Ligula intestinalis was found to be the main cause of fish mortality in Satarkhan Dam of East Azerbaijan Province. Zooplanktons, fish, water and water birds were sampled and studied for infestation with the parasite. We randomly sampled 100 copepods, fixed them in Chloridric Acid 0.01% for 3-4 minute until tissue became soft and colored by Logol. After washing the sample with distilled water, the parasites were separated and identified perevalance of infection was sixteen (1% male and 15% female Cyclops).

The meiobenthic harpacticoids of the Persian Gulf and the Gulf of Oman has been almost unknown. During October 2014 to September 2016, interstitial and phytal harpacticoids were collected from tide pools in 30 different localities along the Iranian coast of the Persian Gulf and the Gulf of Oman. The new information on the distribution of 26 species and 12 families is provided, here. The most species-rich family was Laophontidae with seven species, followed by Miraciidae with four species. In this paper, all the species were considered new records for the area. Furthermore, the first checklist of meiobenthic Harpacticoids is provided.