Structural and functional characterization of pseudopodocyte, a shaggy immune cell produced by two Drosophila species of the obscura group

We recently reported that most of the Drosophila species of the obscura group were unable to mount cellular capsules and no lamellocyte was ever found in the hemolymph of any of the tested species. Only three species were able to encapsulate, despite lacking lamellocytes. Their encapsulation ability was always associated with the presence of an unpreviously described kind of capsule-forming immunocytes designated as “atypical hemocytes”. Here, we describe the ultrastructural and functional characteristics of this type of hemocyte. We show that these cells share many ultrastructural and morphological features with Drosophila melanogaster plasmatocytes, although they are involved in the formation of the external layers of the cellular capsule, a functional property exhibited by lamellocytes in D. melanogaster. Due to the high number of pseudopodes in these cells, we suggest to name them “pseudopodocytes”. After structural and functional characterization of these atypical hemocytes, their ambiguous status between plasmatocytes and lamellocytes is discussed.

► Most of Drosophila species of the obscura group are unable to encapsulate and carry no lamellocyte in their hemolymph.
► However, encapsulation in two obscura species is associated with the presence of pseudopodocytes.
► Structural and functional characterization shows pseudocytes share features with both plasmatocytes and lamellocytes.
► Their ambiguous status is discussed.