Elsevier

Aquaculture

Volume 191, Issues 1–3, 20 November 2000, Pages 45-52
Aquaculture

Crustacean haemocytes and haematopoiesis

https://doi.org/10.1016/S0044-8486(00)00418-XGet rights and content

Abstract

Crustacean haemocytes play important roles in the host immune response including recognition, phagocytosis, melanization, cytotoxicity and cell–cell communication. Classification of the haemocyte types in decapod crustaceans is based mainly on the presence of cytoplasmic granules into hyaline cells, semigranular cells, and granular cells. Each cell type is active in defence reactions, for example; in crayfish, the hyaline cells are chiefly involved in phagocytosis, the semigranular cells are the cells active in encapsulation, while the granular cells participate in storage and release of the prophenoloxidase (proPO) system and cytotoxicity. The haematopoietic tissue has been described in several crustacean decapod species and shown to be the haemocyte-producing organ. Tentative stem cells have been shown to be present in this tissue. Using in situ hybridization, we demonstrated that proPO is not present in the haematopoietic tissue of crayfish which suggests that protein expression is different between circulating haemocytes and the cells in the haematopoietic tissue.

Introduction

The circulating haemocytes of crustaceans and other invertebrates are essential in immunity, performing functions such as phagocytosis, encapsulation, and lysis of foreign cells Smith and Söderhäll, 1983a, Ratcliffe et al., 1985, Söderhäll and Smith, 1986, Johansson and Söderhäll, 1989, Söderhäll and Cerenius, 1992. The number of free haemocytes can vary and can, for instance, decrease dramatically during an infection Persson et al., 1987b, Smith and Söderhäll, 1983a, Smith et al., 1984, Lorenzo et al., 1999. Thus, new haemocytes need to be compensatorily and proportionally produced, and it is commonly believed that haemocytes are released continuously, although at varying rates, from a specialized haematopoietic tissue. This tissue has been identified in several crustacean species Ghiretti-Magaldi et al., 1977, Hose et al., 1992, Martin et al., 1993, Chaga et al., 1995.

Research in the defensive role of haemocyte in crustacean is rapidly progressing, whereas the knowledge on haematopoietic tissue is limited. In order to elucidate the defence mechanisms and allow comparative studies among the different crustacean species, it would be helpful to establish a uniform classification scheme for crustacean haemocytes and haematopoietic tissue. For most crustacean species, the variation in total haemocyte and differential count values are high between individual animals. Consequently, they cannot be used to evaluate the physiological state of the animal. In this review, we briefly point out some works on crustacean circulating haemocytes, on the morphology of the haematopoietic tissue and the cells found, including molecular characteristics of circulating haemocytes and haematopoietic tissue.

Section snippets

Haemocytes

In order to study crustacean haemocytes in an optimal way, it is preferable to work with isolated populations of the different cell types. The success of the isolation of haemocytes depends on the efficiency of anticoagulant used. Söderhäll and Smith (1983) established a protocol for isolation and separation of each cell type for marine decapod species, for example, Carcinus maenus, Cancer pagurus, Macropipus depurator, Eupagurus bernhardus and Nephrops norvegicus (Söderhäll and Smith, 1983,

Haematopoiesis

In many crustaceans, the sheet-like haematopoietic tissue is situated on and covers the dorsal and dorsolateral sides of the stomach and is surrounded by connective tissue. Cells, believed to be haematopoietic cells, of different morphology are organized and densely packed in small lobules, and some of these morphological cell types are also found in the interlobular spaces. This situation has been found in the crab C. maenas (Ghiretti-Magaldi et al., 1977), the lobster Homarus americanus

Molecular characteristics of haemocytes and haematopoietic tissue

The morphologically and functionally different populations of circulating haemocytes described above have also, naturally, been found to be different at the molecular level. This has been shown clearly with separated haemocytes in several species, primarily in crayfish, using a variety of assays (Table 3). In particular, proteins, which are part of or associated with the proPO system, such as proPO and peroxinectin, are present in the semigranular and granular cells and are not detected in the

Acknowledgements

This work was supported by the Swedish Natural Science Research Council, the Swedish Forestry and Agricultural Research Council, and the Swedish Medical Research Council.

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    Present address: Department of Medicine, University of Wisconsin, 4285A Medical Sciences Center, 1300 University Avenue, Madison, WI 53706_1532, USA.

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