Analysis of disseminated neoplasia, other pathologies and DNA damage in the cockle Cerastoderma edule from the estuary of Urdaibai (NE of the Iberian Peninsula)

Zenaba Khatir

Disseminated neoplasia (DN) is one of three cancers that are known to be contagious and it is the only one that is prevalent in bivalves. This study aimed to analyse DN, occurrence of inflammatory reactions, parasites and DNA strand breakage in the common cockle Cerastoderma edule in samples collected from the NE of the Iberian Peninsula. Samples were collected through two sampling dates in January and April 2021. A significantly high female to male ratio was found in both samplings. Condition index (CI) was significantly higher in cockles sampled in the second sampling date where gametes were in advanced gametogenesis stage. Cockles sampled in January were either in post-spawning or resorption stages. Three types of circulating haemocytes were; granulocytes, hyalinocytes and haemocytes with an eccentric nucleus and a large vacuole engulfed in a thin layer of cytoplasm. This third type of haemocytes is rarely described in mollusc. Micronuclei and other nuclear abnormalities were detected in low frequencies in both samplings. Haemocytes infiltration was prevalent in all samples in different intensities. Higher prevalence of granulocytomas, brown cell accumulations, parasites and bacteria was observed in April samples. It was observed that, many cockles with parasite infections undergone gonad castration. In the analyses of DNA strand breakage, there was no significant difference between samples prepared from fresh or cryopreserved haemolymph. Data on the immunofunctional behaviour of haemocytes in C. edule is very limited, further investigations in this topic are essential to better understanding DN in this species.