Introduction. Radix auricularia (Linnaeus, 1758) is a freshwater gastropod belongs to the Lymnaeidae (pond snails) family which act as intermediate hosts or vectors of various parasitic flukes. No study has yet been undertaken on the prevalence of Petasiger spp. infection in R. auricularia. Species of Petasiger (Dietz, 1909) are a cosmopolitan parasite that utilize snails as the first intermediate host, with vertebrates like amphibians larvae and fish as the second intermediate host, followed by fish-eating birds. The current paper is considered to be the first report of Petasiger exaeretus parasitized R. auricularia in Iraq, which is supported with molecular and phylogenetic analysis. Materials and method. Freshwater snails R. auricularia were collected during October 2016-September 2017 from different locations of Sufaia village on the Greater Zab river, Erbil province, Iraq. Results. A total of 307 freshwater snails R. auricularia were collected, only five of them were infected with a prevalence of Petasiger exaeretus (1.62%). Conclusions. The current study agrees with the opinion of Selbach, Soldánová (26), which suggested the possibility of a much higher morphological diversity within Petasiger species, based on the number of described cercariae, compared with adult forms.It is clear that P. phalacrocoracis specimens have often been erroneously designated as P. exaeretus by many authors (Našincová et al., 1994). Certain morphological similarities and dissimilarities between P. exaeretus and P. phalacrocoracis can be detected: the pear-shaped body resembles P. exaeretus, whereas, P. phalacrocoracis have an elongated body.

Freshwater mussels are a guild of stationary, suspended-feeding species; they perform significant ecological functions like nitrogen cycling, bioturbation that gives oxygen and habitat that other creatures need to survive, and increasing water clearance by filtration. Knowledge of the freshwater mussel Unio tigridis Bourguignat, 1852, distribution, and molecular study in Iraq was inadequate. In the current study, this species of freshwater Mussels belonging to the family Unionidae was collected from different locations in the Greater Zab River, from April to August 2022. The average water temperature of the site was arranged between (17.8 to 36.1 C°). All previous studies in the Kurdistan Region and Iraq were based on morphological characters and the current study was the first report of Unio tigridis that was confirmed by molecular genetics and COI gene, analyzed phylogenetically using Maximum Likelihood and Maximum Parsimony Methods.

The present study is concerned with the Chaetogaster limnaei retrieved from the freshwater snail Physa acuta collected from (March-October 2021) from various locations near Chama-dubz village on the Greater Zab River, Erbil province, Iraq. Some Physicochemical variables, like water temperature, pH, Dissolved Oxygen, and Calcium ion experiment on a freshwater snail. The result showed statistically significant differences among Monthly variations with variables (number of snails, water temperature, pH and DO, and Calcium ion). In addition, isolated the Chaetogaster limnaei from Physa acuta with a prevalence was 5.75% (33/574), which has no dorsal and ventral chaeta approximately 14 to 20 per bundle, lack in segments 3 to 5, and chaetae and a vestige of a prostomium with sharply bent teeth. The identified morphologically and molecularly confirmed by using a COI sequence marker confirmed a 100% match to species with accession number (KF952336.1). As a result, the current study is the first report of Chaetogaster limnaei in Iraq, supported by phylogenetic analysis using Maximum Likelihood and Maximum Parsimony Methods.