Involvement of the striped dolphin (Stenella coeruleoalba) melon in immune function: A histological and...

The striped dolphin (Stenella coeruleoalba) is a small pelagic dolphin. The melon, present in most odontocetes, is a rounded structure located in the center of the forehead, between the blowhole and the tip of the head. The dolphin's melon, as well as the blubber, consists of a lipid component similar to that of adipose tissue, with large, rounded cells closely related to each other and a muscular component. The melon primarily plays a role in echolocation, but this organ can also be involved in immune function. Numerous studies have demonstrated the accumulation of contaminants, such as heavy metals, in the fatty tissues of cetaceans (melon and blubber), which alter the immune system and stimulate an inflammatory response. This study aims to describe the involvement of Stenella coeruleoalba melon in immune function. Histological samples of the melon of Stenella coeruleoalba, were used in this study. To describe the morphology of this organ, the sections of the tissue were stained with Giemsa, Masson, and Mallory staining techniques. Immunoperoxidase and immunofluorescence techniques using specific antibodies such as MHC II, Langerin/CD 207, TLR2, and CD14 were used to characterize melon immune cells, providing novel insights into their immunological features. The results showed scattered immune cells among melon adipocytes immunoreactive to the tested antibodies; macrophages are the principal immune cells infiltrating adipose tissue, and their function is to secrete proinflammatory mediators. Furthermore, the adipocytes themselves appear to be labeled with the antibodies used. This study demonstrates the involvement of the dolphin melon in immune function, helping us better understand the immune system of cetaceans, which is still little understood. Furthermore, it could also demonstrate that analyses of blubber collected from deceased individuals of highly protected species can provide valuable information on their health status and exposure to contaminants.