Ultrastructure and Cytochemistry of the Cell Types in the Larval Hematopoietic Organs and Hemolymph of Drosophila Melanogaster. (drosophila/hematopoiesis/blool cells/ultrastructure/cytochemistry)

Abstract

The ultrastructure of the primordial blood cells in the first and second hematopoietic lobes of the late second and third instar larva and prepupa of Drosophila melunogaster was compared with the ultrastructure of the blood cells found freely in the larval hemolymph. Within the hematopoietic lobes two principal cell-types were detected : (i) the prohemocytes and proplasmatocytes, and (ii) different developmental stages of crystal cells., Prohemocytes are characterized by a ribsome-rich cytoplasm, showing small amounts of mitochondria, rough ER and Golgi complexes and few primary lyosomes. Prohemocytes differentiate into proplasmatocytes. When released into the hemolymph they transform further into plasmato-, podo-, and lamellocytes. This differentiation pathway is characterized by a gradual, numerical increase of cytoplasmic organelles, the development of the lysosomal system and the aquisition of the capacity for phagocytosis and melanin formation. The differentiation of a procrystal cell into a crystal cell involves a number of intermediate stages, during which the crystalline material is produced, accumulated,and crystallized. Primary and secondary lysosomes in the primordial blood cells of the hematopoietic organs as well as the free blood cells in the hemolymph were identified cytochemically with the help of the acid phosphatase test. The capacity for melanin synthesis was studied with the phenol-and polyphenol oxidase test.Work on the circulatory system of Drosophilu melanoguster has recently been reviewed by RIZKI (1). Its main components are: i. the dorsal vessel with the 'lymph glands' and the pericardial cells and ii. the hemolymph -hemocyte system. The free blood cell-types in the larval hemolymph have been studied and designated by RIZKI and his collaborators (1-5).

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

“…The main differences between pseudopodocytes and plasmatocytes are their size and the numerous pseudopodia present at the surface of the pseudopodocytes. Another hemocyte type called podocyte was previously described in D. melanogaster showing similar cytoplasmic extensions (Rizki and Rizki, 1980;Shrestha and Gateff, 1982). These cells also showed the same ultrastructural characteristics as the ones of plasmatocytes, and were then considered as a possible intermediate stage of plasmatocytes differentiating into lamellocytes.…”

How Drosophila combats microbial infection: a model to study innate immunity and host–pathogen interactions

“…The haemolymph does not play a role in oxygen transport but is the major site of resistance during systemic infection. Drosophila larvae and adults contain a few thousand blood cells, which can be divided into the following four types on the basis of structural and functional features: secretory cells; plasmatocytes (the most numerous cells, essentially phagocytic); lamellocytes (required for encapsulation of parasites); and crystal cells (involved in the melanization process) [4,5,6 •• ]. Drosophila haematopoiesis occurs in two major phases.…”

The peripheral nervous system supports blood cell homing and survival in theDrosophilalarva

“…Many molecular and cellular aspects of hemocyte development and responses are well conserved between Drosophila and vertebrates Hartenstein, 2006;Lemaitre and Hoffmann, 2007;Martinez-Agosto et al, 2007). In Drosophila, undifferentiated prohemocyte progenitors and three differentiated blood cell lineages are being distinguished (Rizki, 1978;Shrestha and Gateff, 1982;Lanot et al, 2001;Hartenstein, 2006). Macrophages, or plasmatocytes, that express Peroxidasin (Pxn) (Nelson et al, 1994;Tepass et al, 1994;Stramer et al, 2005) and Hemolectin (Hml) (Goto et al, 2001;Sinenko and Mathey-Prevot, 2004), correspond to vertebrate myeloid cells and represent 90-95% of hemocytes at most developmental stages (Tepass et al, 1994;Lanot et al, 2001;.…”

“…Previous reports described a population of posterior dorsal-vessel-associated sessile hemocytes as a hematopoietic compartment that is actively involved in larval immunity (Shrestha and Gateff, 1982;Stofanko et al, 2008;Markus et al, 2009), and cell transplantation experiments suggested persistence of embryonic hemocytes (Holz et al, 2003). Because these reports left important open questions regarding the lineage, anatomical locations and inductive microenvironments, we systematically investigated the biology of the Drosophila larval hematopoietic system.…”