|Hemolymph collection from the adductor sinus NMR image of Elliptio complanata|
A trip to a veterinarian with a pet experiencing healthproblems will usually prompt sampling for diagnostic tests. The AECL has been been working to enhance opportunities for diagnosing health problems in freshwater mussels.
Hemolymph has been harvested for decades for health assessment of marine bivalves, and prior graduate student Lori Gustafson, adapted similar techniques for freshwater mussel hemolymph sampling during field studies. Where marine bivalve hemolymph is generally sampled after boring a hole in the shell to obtain a sample from the pericardial sinus, the sample collection technique Lori developed can be performed in the field without damaging shell integrity. Hemolymph can be harvested from the adductor sinus of freshwater mussels and used to assess organ function, take cell counts, examine hemolymph smears to identify changes in cell morphology, obtain cells for genetic analysis, or conduct toxicologic studies.
Necropsy (examination of the internal organs of an animal) is used to examine and animal after it has died or been euthanized. Tissues are generally taken for histopathological analysis. Similar studies have been conducted with marine bivalves for decades, and numerous pathogens affecting the health and well-being of marine bivalves have been identified using histopathological techniques. Histopathlogic analysis can also yield information about exposure to toxins, such as polychloriinated biphenyls (PCBs) that can affect the health of freshwater bivalves. The AECl in cooperation with Aquatic Pathologist, Mac Law, performs histopathologic analysis to identify potential health problems in freshwater bivalves.
The health status of freshwater bivalves is dependent on the quality of food available for intake and digestion. We know little about the nutritional health requirements of freshwater mussels. Chemical analysis of bivalve tissues can yield useful information about the nutritional status of freshwater bivalves.
Nuclear Magnetic Resonance Imaging
Bivalves have traditionally been killed and bisected when biologists have attempted to learn about their internal anatomy. However, bisection of the adductor muscles releasing the valves for visualization of internal structures, also distorts the ability to visualize their internal anatomy. Nuclear magnetic resonance (NMR) imaging techniques however, provide a useful means of studying the internal anatomy of freshwater bivalves without sacrificing them or altering the anatomic relationship between internal structures. Mike Holliman, a prior NCSU post-doctoral student recently explored using these advanced imaging techniques in the first published examination of freshwater bivalves using NMR imaging.
Numerous pollutants that are potentially harmful to both humans and aquatic fauna have been documented in surface waters around the globe. The effects of the chemicals can be acute and cause rapid mortality, or chronic and produce health effects that might not initially result in the death of aquatic fauna. Although acute events that release high concentrations of contaminants into surface often cause mortality the only evidence of the event that is usually observe is the mortality. Animals that die from these exposure are rapidly removed by scavengers and decomposition,. Chronic insidious exposure to harmful contaminants however often leaves a signature that is evident during histopathologic examination, or can be detected in tissue levels. The AECL works closely with pathologists and toxicologists to examine the consequences of contaminant exposure, and their potential contribution to the evident and continuing decline of freshwater bivalves.