Microscopical studies on the hemocytes of bivalves and their phagocytic interaction with selected bacteria (original) (raw)
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Diseases of Aquatic Organisms, 1997
Phagocytosis of foreign materials by haemocytes is an important aspect of the internal defence of bivalve molluscs. Two main haemocyte types can be distinguished in the haemolymph of the clam Ruditapes decussatus: granulocytes and hyalinocytes. The ability of clam haemocytes to phagocytose zymosan particles, Vibrio P1 cells and trophozoites of the protistan parasite Perkinsus atlant~cus was demonstrated by means of in vitro assays. However, clam haemocytes did not phagocytose atlanticus zoospores in the assays. Granulocytes showed the highest phagocytic capacity in each assay. Phagocytic capacity of haemocytes was not significantly affected by clam age. An ultrastructural study of phagocytosis showed the following sequence of events: engulfment of particles by pseudopods, formation of a phagocytic vacuole, fusion of lysosomes with the phagocytic vacuole, and digestion of the particles giving rise to residual bodies that might be discharged.
Characterization of hemocytes from different body fluids of the eastern oyster Crassostrea virginica
Fish & shellfish immunology, 2017
Bivalve hemocytes are involved in a variety of physiological and immunological functions. Circulating hemocytes in the hemolymph represent the main component of the internal self-defense system while hemocytes present in the extrapallial space (between the mantle and the shell) are actively involved in biomineralization and shell formation. This study focused on the characterization of hemocytes from different body fluids of the eastern oyster Crassostrea virginica. Hemocytes present in the hemolymph were compared to those contained in the extrapallial fluid. Hemocytes associated with the mucus layer covering pallial organs (mantle, gills, body wall) were also investigated because of their potential role as sentinel cells. Hemocytes were characterized using flow cytometry in conjunction with fluorescent epitope markers (clusters of differentiation, lectins) as well as functional assays (i.e. phagocytosis and reactive oxygen species -ROS). Compared with the hemolymph, there was a sig...
Diseases of Aquatic Organisms, 1993
Hemocytes represent the most important internal defense mechanism against foreign material in marine bivalve molluscs. Variations in their density were induced in the hemolymph of 2 economically important clam species (Ruditapes philippinarum and R. decussatus) after challenge with a pathogenic bacteria (Vibrio PI) and after starvation. The number of circulating hemocytes increased in both species 72 h post-challenge when compared to control animals. Following 1 wk starvation, a marked reduction of hemocyte density occurred compared to the control values. It is suggested that reversible migration of hemocytes from the tissues to the circulatory compartment or vice versa explains these variations. Consequently, the hemocyte density may be a quantifiable parameter of the immunodefense response of bivalve molluscs to physiological or pathological stress.
Fish & Shellfish Immunology, 2013
A comparative analyses of hemocytes of molluscs, Pila globosa (Gastropoda: Prosobranchia), Bellamya bengalensis (Gastropoda: Prosobranchia) and Lamellidens marginalis (Bivalvia: Eulamellibranchiata) were carried out for morphotype and subpopulation identification, analyses of phagocytosis and generation of cytotoxic agents. Flow cytometry and microscopic analyses of hemocytes revealed the existence of agranulocytes (blast like cells, round hyalinocytes and spindle hyalinocytes), semigranulocytes (semigranular asterocytes and round semigranulocytes) and granulocytes (round granulocytes, spindle granulocytes and granular asterocytes) as three morphotypes. In P. globosa, granulocytes and semigranulocytes and in B. bengalensis granulocytes and agranulocytes are the chief phagocytes and major producers of superoxide anion and nitric oxide. In L. marginalis, granulocytes were identified as principal phagocytes with prominent activity of superoxide anion and nitric oxide. Highest activity of phenoloxidase was recorded in the agranulocytes of P. globosa with moderate activities among other morphotypes of all three species. Differential result may be due to species specific response, non-identical habitat preference and related adaptation of the species to their different ecological niches.
… on Invertebrate and …, 1991
The chief importance of J'hemocytes as immune effectors in molluscs has led to develop researches for in vitro culture. The chemiluminescence technique has been used to estimate the phagocytosis capacity of Crassostrea gigas hemocytes according to different culture media and times. Sea water was used as a basic medium. Additives, such as antibiotics or glucose and buffers, such as Tris or Hepes, were tested as weIl as artificial sea water. Hemocyte chemiluminescence activities were recorded at t=o in relation to the medium composition. The highest values were observed when hemocytes were kept in sea water without any modification. Whichever medium, chemiluminescence activity was substantially decreased when hemocytes were previously kept in vitro for a few hours. Thus, chemiluminescenee~techniquecould be a well-adapted method to estimate the funetional capaeity of mollusc hemocytes and to study medium composition in prospect of long-term molluscan cell cultures. Despite present limitations of short-term hemocyte primarycultures, they were used to study in vitro the interactions between hemocytès and some mollusc-specific pathogens. The hemoeyte recognition and entry mechanisms of Bonamia ostreae (Protozoa: Ascetospora), an intrahaemocytic parasite of fIat oyster Ostrea edulis, were investigated. Moreover, it was demonstrated that hemocyte respiratory burst was not triggered during parasite phagocytosis. Similar experiments were performéd wi th St-Jacques scallop (Pecten maximus) hemocytes and a host-specifie gill Rickettsialeslike organism, leading to evidenee some pathogen adaptation for escaping host-immune response. These first in vitro models extrapolated to other pathogens anti-infectious immune response of
New Insights from the Oyster Crassostrea rhizophorae on Bivalve Circulating Hemocytes
PLoS One
Hemocytes are the first line of defense of the immune system in invertebrates, but despite their important role and enormous potential for the study of gene-environment relationships, research has been impeded by a lack of consensus on their classification. Here we used flow cytometry combined with histological procedures, histochemical reactions and transmission electron microscopy to characterize the hemocytes from the oyster Crassostrea rhizophorae. Transmission electron microscopy revealed remarkable morphological characteristics, such as the presence of membranous cisternae in all mature cells, regardless of size and granulation. Some granular cells contained many cytoplasmic granules that communicated with each other through a network of channels, a feature never previously described for hemocytes. The positive reactions for esterase and acid phosphatase also indicated the presence of mature cells of all sizes and granule contents. Flow cytometry revealed a clear separation in complexity between agranular and granular populations, which could not be differentiated by size, with cells ranging from 2.5 to 25 mm. Based on this evidence we suggest that, at least in C. rhizophorae, the different subpopulations of hemocytes may in reality be different stages of one type of cell, which accumulates granules and loses complexity (with no reduction in size) as it degranulates in the event of an environmental challenge. Citation: Rebelo MdF, Figueiredo EdS, Mariante RM, Nó brega A, de Barros CM, et al. (2013) New Insights from the Oyster Crassostrea rhizophorae on Bivalve Circulating Hemocytes. PLoS ONE 8(2): e57384.
Morphological Characterization of the Hemocytes of the Clam,Ruditapes decussatus(Mollusca: Bivalvia)
Journal of Invertebrate Pathology, 1997
Josef Berger and Klára Slavíčková (2008) Morphological characterization of hemocytes in the adult linden bug, Pyrrhocoris apterus (L.) (Heteroptera). Zoological Studies 47(4): xxx-xxx. The morphology of hemocytes of the adult linden bug, Pyrrhocoris apterus (L.) (Heteroptera) was characterized via light (both classical and confocal) and transmission electron microscopy. Based on this characterization, we classified hemocytes into 4 distinct types: prohemocytes, granulocytes, plasmatocytes, and spherulocytes. Differential hemocyte counts are described. We propose using the Pappenheim panoptic stain to identify different hemocyte populations of P. apterus. These results are the beginning building blocks of a knowledge base for our ongoing studies of the function of P. apterus hemocytes. As certain morphological characteristics are similar to mammalian blood cells which are used in hemotoxicological safety screening, the use of P. apterus as a new hematotoxicological biomodel is suggested.
Sydney rock oyster (Saccostrea glomerata) hemocytes: Morphology and function
Journal of Invertebrate Pathology, 2007
In this study, three major hemocyte types were identified in the Sydney rock oyster. They were characterized primarily by light and electron microscopy based on the presence or absence of granules and nucleus to cytoplasm ratios. Hemoblast-like cells were the smallest cell type 4.0 ± 0.4 lm and comprised 15 ± 3% of the hemocyte population. They had large nuclei and scanty basic cytoplasm. This cell type also had some endoplasmic reticuli and mitochondria. The second major type were hyalinocytes. Hyalinocytes represented 46 ± 6% of all hemocytes. They were large cells (7.1 ± 1.0 lm) that had low nucleus:cytoplasm ratios and agranular basic or acidic cytoplasm. Hyalinocytes had the ability to phagocytose yeast cells and formed the core of hemocyte aggregates associated with agglutination. Four discrete sub-populations of hyalinocytes were identified. The third major cell type were the granulocytes, comprising 38 ± 1% of the hemocyte population. These cells were large (9.3 ± 0.3 lm) and were characterized by cytoplasm containing many acidic or basic granules. Granulocytes were more phagocytic than hyalinocytes and they formed the inner layer of hemocytes during the encapsulation of fungal hyphae. Five discrete sub-populations of granulocytes were identified based on the types of granules in their cytoplasm. Flow cytometry showed that the hemocytes of rock oysters could be divided into between two and four major cell types based on their light scattering properties. The most common of the cell types identified by flow cytometry corresponded to hyalinocytes and granulocytes. Cytochemical assays showed that most enzymes associated with immunological activity were localized in granulocytes. Their granules contained acid phosphatase, peroxidase, phenoloxidase, superoxide and melanin. Hyalinocytes were positive only for acid phosphatase. All of these observations suggest that Sydney rock oysters have a broad variety of functionally specialized hemocytes, many of which are involved in host defense.
Fish & shellfish immunology, 2015
Deep-sea mytilid mussels harbor symbiotic bacteria in their gill epithelial cells that are horizontally or environmentally transmitted to the next generation of hosts. To understand the immune defense system in deep-sea symbiotic mussels, we examined the hemocyte populations of the symbiotic Bathymodiolus mussel species Bathymodiolus japonicus, Bathymodiolus platifrons, and Bathymodiolus septemdierum, and characterized three types of hemocytes: agranulocytes (AGs), basophilic granulocytes (BGs), and eosinophilic granulocytes (EGs). Of these, the EG cells were the largest (diameter, 8.4-10.0 μm) and had eosinophilic cytoplasm with numerous eosinophilic granules (diameter, 0.8-1.2 μm). Meanwhile, the BGs were of medium size (diameter, 6.7-8.0 μm) and contained small basophilic granules (diameter, 0.3-0.4 μm) in basophilic cytoplasm, and the AGs, the smallest of the hemocytes (diameter, 4.8-6.0 μm), had basophilic cytoplasm lacking granules. A lectin binding assay revealed that concana...