Histopathology as a tool to monitor long term changes in coastal ecosystem: a case study using mussel, Mytillus edulis galloprovincialis

Abstract

Reproductive condition, parasites and pathology in mussel, Mytillus edulis galloprovincialis were surveyed from March to September 2009. Thirty mussels were collected monthly from Masan Bay along the southern coast of Korea. For histological examination, the middle part of the body which contains the gonad and the digestive gland was removed to prepare histology. The histological preparation was examined under a light microscope to determine the reproductive stage, digestive gland atrophy and other pathological conditions. In this study, the mussels were found to be exclusively dioecious and only 1 hermaphrodite was found in July. Most mussels were in late development stage in March (70.0%) and April (40.0%) and ripe individuals were observed in May (43.3%). Spawning mussel was observed at the entire course of the study and mostly in June (52.0%). The pathological conditions such as neoplasia, necrosis and shrinkage of digestive tubule were also observed during the study period although the values were below 15 %. However, digestive gland atrophy index increased from July and was peaked in September. High digestive gland atrophy observed in September was coincided with the poor post spawning conditions and thermal stressor due to the relatively higher water temperature recorded in this month in the year.