Molecular Characterization of the CYTB Gene of Radix auricularia Linnaeus, 1758 (Mollusca, Gastropoda, Lymnaeidae) in Al-Chibayish of Thi-Qar Province, Southern Iraq

Radix auricularia (R. auricularia) is widely distributed in Iraq, including Al-Chibayish marshes and found to be in many morphs. The study aimed to determine the regions of the mitochondrial genome of R. auricularia documented in NCBI and analyze the CYTB gene using bioinformatic tools. From November 2023 to May 2024, R. auricularia snails (480) were collected from six stations (A to F) in the Euphrates River in Al-Chibayish and had morphometric measurement variations. DNA was extracted from the station snails and the partial CYTB gene was amplified. For sequencing, four purified PCR products (approximately 400 bp) were randomly selected for each station. The bioinformatics results showed that the mitochondrial genome of R. auricularia contained 24 non-protein-coding genes and 13 protein-coding genes, including CYTB, NAD5, NAD6 and NAD4L. The protein-coding genes were divided into two groups, overlapping (30.77%) and non-overlapping (69.23%). The CYTB and NAD4L genes partially overlapped and the NAD6 and NAD5 genes partially overlapped as well. The highest shell measurements were noted in the A station snails followed by E, C, F, B and D stations. Six unique haplotypes (H1 to H6) were identified in Al-Chibayish based on this portion of the CYTB gene. H1 was common and was distributed across five stations (A, C, D, E and F) whereas H2 and H3 were only found in the B station. However, H4, H5 and H6 were limited to the C, D and E stations, respectively. H1 and H4 were identical at amino acid levels. Similarly, H2 and H5 were also identical but H3 and H6 were partially identical. The partially overlapped CYTB gene is a suitable molecular marker in the identification of infraspecific R. auricularia snails in Al-Chibayish and could be broadly applied in the intraspecies recognition of molluscan taxa