Copepods: Copepoda

Physical characteristics: Adult females measure 0.147 inches (3.75 millimeters) in length, while males are 0.074 inches (1.9 millimeters). The fore body is long and the mouthparts are absent. The antennules are short in both males and females; those of the males are bent. The first four pairs of thoracic limbs are well developed, but the last pair is small. They are in the shape of two rounded structures, or lobes. The short abdomen has a pair of egg-bearing spines and a pair of large structures on the tip.

Geographic range: This species is found in the Northeastern Atlantic Ocean.

Habitat: The free-living adults live along the coast and are found in the upper layers of water. Parasitic nauplius larvae develop inside the bodies of snails or worms.

Adults lack mouthparts and do not eat. The nauplius larvae absorb nutrients from their hosts. (Illustration by John Megahan. Reproduced by permission.)

Diet: Adults lack mouthparts and do not eat. The nauplius larvae absorb nutrients from their hosts.

Behavior and reproduction: Females carry their eggs on long spines. The eggs hatch into free-living nauplius larvae. The nauplius finds a host and attaches itself with special claws on the antennae and jaws, or mandibles. They eventually burrow through the skin. Once inside, the nauplius becomes sacklike in shape and its appendages rootlike. They use their appendages to soak up nutrients from the host's body. When the last larval stage is reached, the larva leaves the host and molts to become an adult.

Little is known about mating behavior. Males presumably grab females with their antennules and use their swimming limbs to transfer the sperm packet.

Monstrilla grandis and people: This species does not impact people or their activities.

Conservation status: This species is not considered threatened or endangered. ∎