METHODS OF STUDYING HARPACTICOIDS

A full description of a harpacticoid is difficult to achieve without dissecting the animal and studying its parts under the highest powers of the light microscope. Fortunately the observations necessary to identify an animal with a known species usually can be made on a whole mount, although viewing with oil immersion optics is often required. Techniques vary from worker to worker; one excellent set of methods is given by Hamond (1969).

Usually the animal is mounted with the ventral side uppermost so that details of the appendages can be seen but it may be necessary also to view from the dorsal and lateral aspects, or to roll the animal over so that the relevant details may be observed better. Temporary mounts are thus more useful than permanent ones and media such as glycerol, lactic acid, lactophenol, poyvinyl lactophenol, or various proprietary mount ants can be used. It is most important that the mount ant is reasonably viscous, so that the animal is not squashed when the cover glass is put on and so that it may be rolled to the desired aspect. Some mountants, e.g. lactic acid, have a rapid clearing action which is not entirely desirable, particularly if the mount is to be kept for some time, as the fine details become difficult to see. Light staining of the specimen may be helpful, but often is not necessary. Among suitable stains are Acid Fuchsin, Chlorazol Black, Lignin Pink, Orange G and Rose Bengal.