Abstract
Hemocytes represent one of the most important defense mechanisms against foreign material in Crustacea and are also involved in a variety of other physiological responses. Fluorescent lectin-binding assays and cytochemical reactions were used to identify specificity and distribution of carbohydrate moieties and presence of several hydrolytic enzymes, in hemocytes of whiteleg shrimp Litopenaeus vannamei. Two general classes of circulating hemocytes (granular and agranular) exist in L. vannamei, which express carbohydrates residues for FITC-conjugated lectins WGA, LEA, and PNA; UEA and Con-A were not observed. Enzymatic studies indicated that acid phosphatase, nonspecific esterase, and specific esterases were present; alkaline phosphatase was not observed. The enzymes and carbohydrates are useful tools in hemocyte classification and cellular defense mechanism studies.
Highlights
In crustacean decapods, the defense system relies on humoral and cellular mechanisms, with cellular defense coordinated by circulating hemocytes [1]
Description of hemocyte types using morphological criteria previously developed for the shrimp [21] shows three basic cell types: small-granule cells (SGC), large-granule cells (LGC), and hyaline cells (HC)
Controls with the inhibitory saccharides demonstrated that the binding of fluorescein isothiocyanate- (FITC-)lectin was specific, since the presence in the incubation medium of the appropriate haptenic sugar (Table 1) abolished or markedly decreased fluorescence
Summary
The defense system relies on humoral and cellular mechanisms, with cellular defense coordinated by circulating hemocytes [1]. Structure, function, and classification of hemocytes in decapods indicate three fundamental types, according to the number and size of granules present: hyaline cells, small-granule cells, and large-granule cells [4]. These types are described for penaeid shrimp [5, 6] and freshwater crayfish [7, 8]. Hemocytes can recognize and eliminate or sequester invading pathogens through phagocytosis, encapsulation, and secretion of lysosomal enzymes and bacteriostatic substances [9, 10]. Granular hemocytes carry out phagocytosis by engulfing small foreign particles. Invertebrate hemocytes have several carbohydrate moieties that act as receptors for invading pathogens, where binding of lectins and carbohydrates leads to structural changes of the complex that induce activation of hemocytes [17, 18]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
