Histology: Biology on a Microscopic Level

Scientists at the Marine Mammal Pathobiology Laboratory (MMPL) perform necropsies (non-human autopsies) on manatees and, as necessary, on a variety of other marine animals. During necropsy of fresh carcasses, tissue samples are cut from a variety of organs and placed in a preservative so they may be used for histology: the study of the structure of organic tissues. The preservative used in this process stops decomposition and hardens the tissues. Tissues are trimmed further and then treated with stains to help emphasize cellular components. The stained sections are embedded in paraffin (wax) and sliced extremely thin (to 10 micrometers). These sections are applied to a glass slide so they can be examined under a light microscope. In general, MMPL scientists conduct histology for four reasons:

1. Track or Monitor Changes-In addition to determining "normal" tissue conditions, histology allows scientists to recognize tissue changes over time.
2. Observe Pathologies-Scientists are still learning about the pathologies (the conditions and processes of diseases) in manatees and other species. Many of these pathologies can be identified microscopically.
3. Cause of Death-Violent causes of death, such as impact from watercraft or boat propellers, may be obvious in necropsy. However, other causes of death may not be readily apparent without histological information.
4. Archives-Historical information is kept through storing preserved tissues for later use, also known as tissue banking. This archiving process will allow scientists studying manatees in the future to compare their research with data from the past. Tissue banking gives scientists the potential to study much larger groups of animals over longer periods of time.

Fresh carcasses provide the most useful histological information. Unfortunately, after death, manatees and other animals and plants decay quickly in Florida's warm, humid climate. As tissues and cells degrade, less histological information can be retrieved from them. The histological information gleaned from each sampled carcass provides researchers with additional information about both individual animals and the species as a whole. This effort is vital to manatee research, so whenever possible, researchers include histology collection as part of necropsies. While every manatee death is a tremendous loss, each manatee carcass provides a new opportunity to learn information that may allow scientists to help conserve the manatees that are still living. The organized collection of histological data and other samples allows researchers access to additional information that may ultimately lead to improved conservation of this endangered species.