Histopathology
Histopathological study was carried out on the treated and control
gills of tilapia to assess the damages caused to internal organs. Gills
were chosen for the study since they are considered to be the main
portal entry of external particles such as microorganisms. The control
gills, infected gills and treated gills (exposed to the plant extracts for
treatment) were used for this study. In the control gills, clear morphology
showing hyaline cartilaginous rods in each of the filaments with
clear primary lamellae and secondary lamellae were seen. Single large
sized squamous epithelial cells and muscle cells lay scattered on both
ides of the lamellae as seen in Fig. 3a. Infected gills showed complete destruction
of lamellae which was also reported in our previous study
(Thanigaivel et al., 2014). However in the ethanol and aqueous seaweed
extract treated groups, the gill lamellae were clearly seen although
there were slight inflammation of organs, and slight destruction of gill
morphology as shown in Fig. 3b, c. This corroborates with the results
of Nasiruddin et al. (2013) who reported that treatment with different
seed extracts showed histopathological variations in the different organs
of Heteropneustes fossilis (Bloch) depending on the toxicity of the
ethanol and aqueous extracts of the three botanicals Lagerstroemia
speciosa (L.) Pers, Dipterocarpus turbinatus, Gaertn and Hevea brasiliensis
used.