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Jannicke Wiik-Nielsen

A female roundworm coils around a male whose two needle-like mating structures, called spicules, protruding from its posterior end. A type of parasitic nematode, roundworms infect fish as well as birds and seals. Identifying them, Wiik-Nielsen says, "is important in terms of seafood safety and public health, as humans may be infected."

This detail of a roundworm head shows the parasite's mouth and three lips.

The outer part of a tapeworm's body is called the tegument; through it the parasite absorbs nutrients from its host. This photo reveals the tiny, bristle-like microvilli that cover the tegument and help maximize its surface area.

A detail of a tapeworm head reveals grooves known as bothria, which the tapeworm uses to attach itself to a host's intestinal wall.

Tapeworms are parasites that live in the intestines of humans and animals, including many fish. They do not have a digestive tract, so instead they absorb nutrients from their host's digested food.

A dog flea has a mouth designed to pierce skin and suck blood and elongated hind legs to facilitate jumping. Its body is flat and covered with spines and bristles. This shape, Wiik-Nielsen says, "helps with forward movement through dense fur, prevents dislodgement, and steadies the flea during feeding."

This detail of a dog flea reveals one of the parasite's two antennae, which "play a significant role in host-finding," Wiik-Nielsen says, "and are also crucial for successful mating."

Wiik-Nielsen found this bee in her garden. The structures at the base of its head are called mandibles, which bees use for cutting, eating pollen, and working wax, Wiik-Nielsen says.

Pollen grains dot the surface of a bee nose, magnified some 1,200 times.

Bumblebees "are important agricultural pollinators," Wiik-Nielsen says. The one shown here is magnified approximately 40 times.