Daphnia species typically have bodies ranging from 1 to 5 mm (0.039–0.197 in) in length, segmented but not visibly so. The head is fused and typically bent downward toward the body, with a visible notch separating the two. In most species, the body is covered by a carapace, leaving a ventral gap where the five or six pairs of legs are situated. The most notable features include the compound eyes, the second antennae, and a pair of abdominal setae. Many species have translucent or nearly translucent carapaces, making them excellent subjects for microscopic observation, allowing one to observe the beating heart.