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Artemia: A Model Specimen


Figure 6 : Synchronized movements like couple swimming (day 19). Bright-fi eld, objective Pl 2.5/0.08, fl ash.


the specimen’s surface is hit by the illuminating light beams, and fi ne details such as hairs and eye pigments can be seen at higher resolution and clarity. In bright-fi eld images, however, elderly Artemia may appear as dark silhouettes because of their thickness and density. T rough daily observations young explorers can comprehend the phenomena of growth, diff erentiation, and maturation. T e actual length of growing Artemia can be measured on the screen or on photographic prints. For this task photographs should be projected or printed as large as possible in order to obtain appropriate precision in measurements so that estimations can be made to 0.1 of a millimeter. Body lengths should be measured from the head to the caudal furca (see Figure 2 ). For each magnifi cation used, students can learn how


to evaluate the respective horizontal fi eld width. T e millimeter scale of a small transparent ruler imaged with the microscope is suffi cient for this task at low magnifi cations. For higher magnifi cations (10× objective lenses, for instance), the ruler should be replaced by a calibration slide (slide micrometer). Young students also can learn that higher levels of differentiation correspond with greater variation in locomotion patterns. Motion patterns can be documented by


video clips. Even slow-motion videos can be produced by most consumer digital cameras and modern smartphones (for example, see web sources [g] and [h]). Pedagogically, it can be regarded as an advantage that the whole “metamor- phosis” from young larvae to mature animals can be observed within a rather short period of 4 or 5 weeks. The animals show morphological changes every few days. Thus, young “scientists” will not be overstrained or bored. Young investigators might be motivated to pursue further experi- ments involving digital image processing, especially creating digital “dark-field” or digital “phase contrast” images. For advanced students a variety of further experiments can be suggested so that Artemia can be used for introductions to statistical analyses and several types of physiological and ecological investigations. Thus, by studying Artemia students can comprehend some general principles of scientific workflows.


Conclusion Artemia sp. is well suited for educational projects leading to insights about important phenomena of life, such as


Figure 7 : Examples of various movement patterns in elderly individuals (days 26–32). Same equipment as Figure 4 .


16


Figure 8 : Digital inversion of bright-fi eld images. Original photomicrographs taken in brightfi eld with a fl ash (a, c) and inverted to “digital darkfi eld” (b, d) on day 8 (a, b) and day 28 (c, d).


www.microscopy-today.com • 2018 July


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