Behavior
Adult anostracans swim constantly using the phyllopodous thoracic appendages. Waves of motion pass along the series of phyllopods to draw water and food particles into the food groove and to create an effective stroke with the swimming setae so that locomotion and feeding are accomplished simultaneously. Artemia also feeds by scraping algae from hard surfaces. Anostracans can make sudden quick moves by flexing the abdomen. The caudal furca is also equipped with plumose swimming setae.
>1f. With a dissecting microscope and incident illumination observe a living, active adult brine shrimp swimming in a dish of water. Note the orientation of the animal in the water. The preferred orientation is with the dorsum down butArtemia can swim right side up also. The filter-feeding mechanism works best when upside down. Which appendages are used for locomotion? Do the antennae seem to be involved in swimming? Does the animal ever stop swimming? Do you see any evidence of feeding by scraping the bottom? Watch for movement resulting from flicking the abdomen. How does it differ from motion produced by phyllopods? <
Artemia, with its three eyes, is sensitive to light intensity and exhibits highly variable responses to light. In general, Artemia is positively phototactic at low light intensities and photonegative at medium and high intensities. The response varies, however, depending on the physiological condition of the animal, wavelength, age, salinity, pH, and metabolic condition.
>1g. Place a dish containing larvae in a part of the room where it will receive uneven illumination. Leave the dish for 15 minutes or so and then observe the distribution of shrimp. Do they seem to be clustered in any particular region of the dish? How does this relate to the light source? You may want to design a series of more carefully controlled experiments to determine the effect of light intensity, life history stage, salinity, wavelength, or temperature. <
Most animals exhibit what is called the "dorsal light reaction" in response to the sun's rays by maintaining their dorsal surface up. A few animals, such as Artemia, backswimmers (hemipterous insects), and the fish louse, Argulus (a crustacean), reverse this response and exhibit a "ventral light reaction" and keep the ventral surface pointed toward light. Consequently, brine shrimp (and fairy shrimp) normally swim upside down (ventral side up), because in nature the light is overhead. A brine shrimp in a dish on the stage of a dissecting microscope withsubstage illumination, however, may reverse its orientation and swims with the ventral side down.
>1h. Place a brine shrimp or fairy shrimp in a small culture dish and put it on the stage of the dissecting microscope with the incident lamp on and the substage lamp off. Observe the swimming orientation of the animal. Turn the incident lamp off and the substage (transmitted) lamp on. Do this several times noting the response of the animal.