The lymphoid organ in penaeids and it's interaction with moulting

Rusaini, (2006) The lymphoid organ in penaeids and it's interaction with moulting. Masters (Research) thesis, James Cook University.

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Prawn immunity is still a mysterious puzzle in immunology. However, this knowledge is important in culture management in order to avoid the devastating impact of infectious pathogens and economic losses. Furthermore, since the effectiveness of vaccination and immunostimulants is unclear, the enhancement of immune capability of prawns might provide a bright light to this industry. Therefore, the objective of this thesis was to develop a simple modified method of quantifying the histopathological changes of a component of the lymphoid organ (LO), the spheroid cells, and apply this technique in a study of the influence of moult cycle, lunar rhythm, and viral infections on spheroid cells quantification.

Moult cycles of P. monodon were studied by using setal development (setogenesis) and retraction of epidermis from the setal bases (apolysis) in the inner uropod adjacent to the telson tip. Five stages and four substages of the moult i.e. postmoult (stage A and B), intermoult (stage C), and premoult (stage D0, D1, D2 and D3/D4) and ecdysis (stage E) could be determined by applying these two criteria. However, unsynchronised development of these two criteria in abnormal prawns led to the difficulties in differentiating between stage B, C and D.

A modified transect technique seemed to offer a simple, rapid, and accurate method in analysing the abundance of spheroid cells in the lymphoid organ. Furthermore, one half longitudinal section of the cephalothorax represented the abundance of the spheroid cells in the lymphoid organ of penaeid prawns. Based on this technique, the fluctuation of the lymphoid organ spheroid (LOS) cells during the life of P.monodon was investigated. It was found that animal size (weight and total length) had no significant effect (P > 0.05; ANOVA) on the spheroid to total tissue (STT) ratio, the prevalence of vacuolated spheroids and the number of vacuoles in the spheroid cells.

Unfortunately, the cyclic phenomena of the prawn’s, moult cycle also showed no significant effect on any measure of spheroid cells (P > 0.05) rejecting the original hypothesis of this work. The effect of the prawn’s sex was variably related to the spheroid cells during the experiments. In the first two trials (Chapter 5 and 6), evidently sex had no significant effect on any measure of spheroid cells (P > 0.05). However, in the last experiment (Chapter 7) female bias on the ratio of STT was obvious (P < 0.05).

Lunar related patterns on the spheroid to total tissue ratio were evident during the experiments. It was found that the STT ratio was significantly lower at new moon than first quarter and full moons (P < 0.05). This indicated that increased activity of the prawns during the dark moon enhanced immunocompetence of the prawns to eliminate viral diseases. Moreover, apparently, the STT ratio of GAV-injected prawns was significantly higher than control prawns (P < 0.05). Together with this, the presence of distinct bacterial granulomas in the lymphoid organ implied that the formation of the spheroid cells in the haemal sinuses of the lymphoid organ was only associated with viral diseases not with bacterial infections.

Item ID: 2089
Item Type: Thesis (Masters (Research))
Keywords: lymphoid organs, penaeids, moult cycles, prawns, immunity, Penaeid monodon, spheroid cells, acquaculture
Date Deposited: 26 Feb 2009 02:47
FoR Codes: 06 BIOLOGICAL SCIENCES > 0608 Zoology > 060808 Invertebrate Biology @ 0%
07 AGRICULTURAL AND VETERINARY SCIENCES > 0704 Fisheries Sciences > 070401 Aquaculture @ 0%
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