''Cardiodectes bellottii'' is a species of copepods in the family

Pennellidae Pennellidae is a family of parasitic copepods. When anchored on a host, they have a portion of the body on the outside of the host, whereas the remaining anterior part of the parasite is hidden inside tissues of the host. Genera There are 24 ge ...

. It is a parasite of fish. It is found in the Atlantic and Pacific Oceans as well as the Mediterranean Sea; specimens from the Pacific were formerly treated as a separate species, ''Cardiodectes medusaeus''. In the cnidarian '' Hydrichthys sarcotretis'', parasitism is taken a stage further when the hydrozoan attaches itself to the ''C. bellottii''. This is itself an ectoparasite of the northern lampfish (''Stenobrachius leucopsarus'') in the family Myctophidae. The copepod attaches itself to the

bulbus arteriosus In the circulatory system of fish, the bulbus arteriosus is a pear shaped chamber that functions as a capacitor, maintaining continuous blood flow into the gill arch Branchial arches, or gill arches, are a series of bony "loops" present in fish, ...

of the fish. Such a parasitic chain is known as

hyperparasitism A hyperparasite, also known as a metaparasite, is a parasite whose host, often an insect, is also a parasite, often specifically a parasitoid. Hyperparasites are found mainly among the wasp-waisted Apocrita within the Hymenoptera, and in two othe ...

. ''C. bellottii'' requires two hosts for proper development. It will go through five successive postembryonic stages, then only the postmated females will go into the pericardial cavity of a

lanternfish Lanternfishes (or myctophids, from the Greek μυκτήρ ''myktḗr'', "nose" and ''ophis'', "serpent") are small mesopelagic fish of the large family Myctophidae. One of two families in the order Myctophiformes, the Myctophidae are represente ...

. The actions of the copepod castrate its fish host. Both male and female fish do not reproduce and seem to grow faster when attacked by the copepod and it seems to have a negligible energy demand from them. The hydrozoan parasite castrates the copepod, a process called hypercastration.

References

Siphonostomatoida Animal parasites of fish Crustaceans of the Atlantic Ocean Crustaceans of the Pacific Ocean Fauna of the Mediterranean Sea Crustaceans described in 1882 {{copepod-stub