Describing morphological structures, especially when working with extremely small specimens, can be a difficult and often frustrating endeavor. The most difficult part is visualizing three dimensional structures.
What is the best imaging method?
The answer is not trivial. There is no one method that we can use for all structures. There are various methods of imaging we can utilize, whether we want to see surface sculptures, relative position of structures, muscles, or any other structure we might need to visualize. Scanning electron microscopy is excellent for examining surface sculpture, but we cannot see past the surface of a structure, nor can we see color with this method. Bright field microscopy using a stereo or compound microscope allows us to see color, and using transmitted light, we can see through transparent structures. Using laser scanning confocal imagery, we can highlight various materials by causing them to fluoresce at different wavelengths, which we can display in different colors. This allows us to see the limits of different materials such as muscles and sclerites. The point of imaging a structure is to help us visualize a structure but it is also to help us describe structures to others, because a picture is worth a thousand words.
In the Deans lab we have recently explored some methods for visualization that allow us to see the shape and relative position of structures. Images have been produced of the ovipositor structure of Trassedia luapi (Hymenoptera: Megaspilidae) using both bright field microscopy and laser scanning confocal microscopy. The ovipositor is the structure that a female uses to lay eggs on or in her host. The ovipositor of Trassedia luapi is only about 1.5mm long. Because of the high magnification we use to view such small structures, the range of focus is extremely narrow. To account for this, images are taken at several planes of focus. Using the appropriate software, the series of images are used to build a single image where all parts of the structure are in focus. This is an excellent method for visualizing a three dimensional structure, however it can be difficult to determine the arrangement of structures on top of one another. Using the same set of images, we can create videos that move progressively through the set of images. This visualization technique gives us a perspective of depth. With laser scanning confocal images, we can also produce a rotating three dimensional model of the structure.