Daphnia are little-known organisms—small crustaceans that reside in fresh bodies of water, such as ponds or lakes. Because of their similar form, their similar twitchy way of moving, and their aqueous niche, they have been nicknamed “Water Fleas.” Despite this epithet, the only other common characteristic Daphnia and fleas have is that they’re both arthropods (a skeletal system on the outside of their bodies). Shrimp are actually the closet “relative” of Daphnia. Daphnia have an almost transparent exoskeleton, providing a remarkable look inside their bodies. Daphnia vary widely and there exist more than 150 different species. Although relatively obscure, these animals are essential parts of the food chain, and for many fish, Daphnia is a main course. Daphnia themselves eat mostly algae and other microorganisms drifting in the water.
One of the most interesting things about Daphnia is their ability to have two separate methods of reproduction. In nice weather, when food is more available, Daphnia will practice parthenogenicity. Parthenogenicity is basically a form of asexual reproduction during which the parent produces one or multiple genetic clones. These offspring are born live, like humans, because the favorable conditions ensure a better chance of survival. Remember, the Daphnia at this time are all female! However, during bad weather, Daphnia will produce some eggs that will turn into males with the help of fertilization. Offspring from sexual reproduction will remain in their eggs in a state of suspend animation, until conditions and, correspondently, chances of survival have improved.
Since Daphnia are nearly transparent, their color is affected
by physical factors, such as their latest meal or the amount of oxygen in their environment. Their antennae allow them to move while their feet suck in food from their surroundings. A Daphnia’s clear, beating heart is present in the upper left corner of its body, and
Daphnia only have one eye. A Daphnia’s fascinating body structure offers endless hours of observation, and with a powerful enough microscope, the blood cells moving about its body can be seen.