Pathology of midgut gland-cells of Penaeus monodon postlarvae after Leucaena leucocephala feeding

Abstract

ABSTRACT. Leucaena leucocephala, one of the promising feed sources in aquaculture of tropical regions, induces drastic pathological alterations in the midgut gland ( = hepatopancreas) cells of Penaeus monodon postlarvae. After 28 d feedng on a formulated diet containing Leucaena wlth natural mimosine content, the most severely affected cell type is the R-cell, followed by F-cells B-cells are only rarely pathologically changed. Artificial reduction of mimosine content prior to &et formulation results in less severe signs of pathology. The course of cell injury suggests that the nucleus is one of the primary targets of Leucaena toxicity to midgut gland-cells. Pathology starts, in all cell types, with alterations In the fibrillar component of the nucleolus accompanied by fading of the nucleoplasm and cytoplasm. Thereafter, the heterochromatin of the cell nucleus is step-by-step decondensed. Obviously, structural components of the nucleolus organizer region are changed, thus leadlng to a cessation of rRNA synthesis and eventually of ribosome production. The simultaneous decondensation of the nuclear heterochromatin may cause disturbances of cell function and finally lead to cell lysis. Prawns may die of septicemia when high numbers of midgut gland epithelium cells are destroyed. From the cytoplasmic organelles, only the mitochondria and F-cell dictyosomes display disorders in the early stages of pathology. These alterations are probably nucleus-independent. The darkening of the mitochondrial matrix may be caused by depletion of oxidative phosphorylation due to enzyme inhibition, whereas the vacuolization of the Golgi-cisternae in F-cells is interpreted as cytoskeleton injury.

Hepatopancreatic brush border lysis (HBL) -- a new bacterial disease of the shrimp Palaemon elegans

“…The most prominent feature of HBL cytopathology is the depression of individual, bacteria-contacted microvilli. Such a peculiar kind of bacterial attachment has not previously been reported for aquatic animals (Johnson 1983, Kinne 1983-1990). Adhesion of bacteria to surface structures of target cells is often a prerequisite of their pathogenicity (Huq et al 1986, Yamamoto & Yokota 1989.…”

“…(2) The observed discharge also does not reflect extrusion of R-cells and F-cells damaged by premature aging, chemicals, viruses, etc., because in such cells the organelles would be considerably transformed prior to rupture of the microvillous border (Vogt 1990). In HBL, however, the bacteria-contacted microvillous borders disintegrated before there was any obvious lesi.on, of the cell organelles (Fig.…”

Functional cytology of the hepatopancreas of Palaemonetes argentinus (Crustacea, Decapoda, Caridea) under osmotic stress

“…F cells are implicated in the synthesis and secretion of digestive enzymes and R cells store the lipids and glycogen, and are also implicated in the detoxification processes (Vogt and Quinitio, 1994;Icely and Nott, 1992;Johnston et al, 1998). The profound damages observed in these cells, particularly in R cells, such as nuclear retraction, pyknosis, cytoplasmic vacuolization, and cytoplasmolysis largely followed the scheme given by Vogt (1990) and Trump et al (1981) for this stage of necrosis. It has been suggested that Rcells are the most sensitive to metabolic and environmental changes such as starvation, salinity and pollutants (Storch and Anger, 1983;Masson, 2001;Vogt, 1987;Vogt and Quinitio, 1994).…”

“…In P. argentinus, the degenerative desquamation is a usual periodic event during the moulting cycle (Sousa and Petriella, 2000;2001). However, in this prawn, like in P. monodon (Vogt, 1990), A. longinaris (Masson, 2001), and P. muelleri (Cuartas et al, 2003), the increased desquamation produced by different stressors results in a high rate of cell loss that does not make possible the restitution of the damage tissue. This has been mentioned for Litopenaeus vannamei, L. stylirostris and Farfantepenaeus californiensis (Lightner and Redman, 1994) infected by the NHP virus, in which necrosis foci with important haemocytic infiltration were also characteristic.…”

“…This alteration was also observed in marine crustaceans acclimatized to low salinities, such as Artemesia longinaris (Masson, 2001) and Pleoticus muelleri (Cuartas et al, 2003). According to Vogt (1990), the process of desquamation in the hepatopancreas of P. monodon starts with the cells lysis, in particular Rcells, and the neighbouring cells protrude in small basolateral extensions, pushing the damage cells into the tubular lumen generating ulcerations. In P. argentinus, the degenerative desquamation is a usual periodic event during the moulting cycle (Sousa and Petriella, 2000;2001).…”