English: A calanoid copepod photographed under a microscope using a 4x objective and dark-field microscopy. The specimen was collected in April 2021 from an old mine in Lääne-Virumaa, Estonia, which fills with water in the spring. Calanoids are the largest representatives of copepods. The image clearly shows the species' characteristic elongated body structure, reddish-brown coloration, and particularly striking long setose antennae used for swimming. The body is distinctly divided into anterior and posterior regions, and the appendages show characteristic setae. The image was captured using dark-field microscopy, where light rays are directed at the specimen from the sides using a special condenser so that no direct light reaches the objective lens. In the microscope, we only see the light that is reflected or scattered by the specimen. This technique particularly emphasizes the transparent parts and setae of the animal. The image was created using focus stacking technique, which ensures great depth of field throughout the subject.