L'ultrastruttura dell'organo dell'emolinfa nella larva di Drosophila melanogaster

Summary The structures formerly described as blood-forming organs or lymph glands in Drosophila melanogaster were re-examined by means of phase contrast, polarized light, and electron microscopy. As a result, the term haemolymph organ is suggested as more appropriate for these peculiar organs. Haemolymph organs of second and third instar larvae, and first stage (white) pupae from a wild strain (Varese) were studied; the methods are described in detail.The haemolymph organ consists of two voluminous anterior lobes and several smaller posterior ones that are ovoid or tubular in shape. The anterior lobes comprise an outer capsule containing some muscle cells, a supporting stroma, and various kinds of cells. The stroma appears to consist of lamellated material of scleroprotein nature similar to that described in other organs of numerous insect species. This material must be considered as a component of the connective tissue characteristic of insect organs.The cells are isolated or organized in groups of various sizes. The following types can be distinguished: rounded cells that are poorly differentiated, polygonal cells with well developed cytoplasm rich in organelles, polygonal cells with clear cytoplasm, and cells that appear to be intermediate form of the types mentioned above.The morphological data presented confirm that the haemolymph organ produces and releases into the haemolymph various types of cells; of these the polygonal cells have a phagocytic and excretory function while only hypotheses can be presented at present concerning the role of the rounded cells. In addition the presence of polygonal cells with clear cytoplasm, showing signs of secretory activity, suggest that the haemolymph organ is involved in the production of substances constituting the fluid fraction of the haemolymph.

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Ricerca eseguita con i sussidi del C.N.R. (Impresa Genetica).