TRANSLOCATION OF INGESTED MICROPLASTICS IN TILAPIA AND POSSIBILITY OF HABITUATING TO SUCH INGESTION

It has been estimated that trillions of plastic particles are currently floating on the surface of the oceans and can degrade to form microplastics (MPs) that range in size from 1 - 1000 μm . The ingestion of MPs can alter digestive enzymes and cause severe histopathological damage in some fish species. This could be due to their physical presenc e via translocation, but has only been shown in a few studies.    The aim of this study was to fed tilapia MP contaminated feeds (at 0.1 or 1.0%) and the fish were sampled at 2 week intervals for plasma biochemistry,  intestinal digesta short chain fatty acids (SCFA), potential presence of MPs in the liver, gills and muscle as well as liver histopathology, trypsin activity and HSI.

Diets (isontirogenous/isolipidic) were formulated to meet the requirements of tilapia. MPs were added at expense of cellulose. Treatment s were triplicated with 10  juveniles (23 g) in each and fed twice daily to apparent satiation.  After 2 weeks, fish were sacrificed, sampled and measured for the above parameters, and this was repeated after another 2 weeks.

At both weeks, feed intake significantly decreased in th e 0.1 and 1.0% MP treated diets. F ish often repeatedly expelling and chewing the food. MPs were detected in the gills, liver and mus cle, indicating translocation. Liver histopathology revealed severe damage that included hemorrhaging and extensive necrosis (Fig. 1). Both liver trypsin activity and HSI were also significantly lower along with intestinal digesta SCFA. After another 2 weeks, these parameters normalized to  the control with the liver only showing some localized instances of inflammation.  MPs in the liver also decreased.  

These findings  have been facilitated by excreting MPs, as the number of translocated MPs in the liver decreased, but the exact mechanism(s) for this finding should be explored further.