histology slides

Histology

by Catalina Brown 

Histology is a branch of anatomy used to study tissue structure and function in animals and plants.  Scientists use light and electron microscopes to analyze small sections of preserved tissue. Small pieces of tissue are fixed and embedded with paraffin or plastic, and thin sections are stained to identify parasites, bacteria and fungi or to find tissue abnormalities. Scientists also examine tissues to understand and describe pathological or other biological processes such as gonad development. Many FWRI groups, including Fish and Wildlife Health, Fish Biology and Shellfish Biology, use histology as an integral part of their research.  For example, histology has been used to determine the reproductive status of populations for decades. In 1991, the FWRI histology lab modified the periodic acid Schiff (PAS) metanil yellow (MY) stain to highlight different tissue components to determine reproductive stage of an animal.  This stain, which differentially colors cell components and accentuates contrast in tissue sections, provides sharp characterization of tissue morphology and is now used worldwide.  Histology is a critical tool used by scientists to study animal and plant disease and to evaluate the overall health of marine species that are important to Florida.

slides of cells
Trichodinella sp. parasite in the gill of a Red Drum – Sciaenops ocellatus. Figure A shows the parasite as seen under a wet mount used to examine fresh tissue with light microscopy. In figure B, the same parasite can be seen in gill tissue that has been processed for histology and stained with the PAS/MY stain. Photo credit: FWH staff.