''Pennella'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of large

copepod Copepods (; meaning 'oar-feet') are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (living in the water column), some are benthos, benthic (living on the sedimen ...

s which are common

parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...

s of large

pelagic The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the sur ...

fishes. They begin their life cycle as a series of free-swimming

plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...

larvae A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect developmental biology, development such as insects, some arachnids, amphibians, or cnidarians typical ...

. The females metamorphose into a parasitic stage when they attach to a host and enter into its skin. The males are free swimming. Due to their large size and mesoparasitic life history there have been a number of studies of ''Pennella'', the members of which are among the largest of the parasitic Copepoda. All species are found as adults buried into the flesh of marine bony fish, except for a single species, ''Pennella balaenopterae'' which can be found in the muscles and blubber of

cetacean Cetacea (; , ) is an infraorder of aquatic mammals belonging to the order Artiodactyla that includes whales, dolphins and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively c ...

s and occasionally other

marine mammal Marine mammals are mammals that rely on marine ecosystems for their existence. They include animals such as cetaceans, pinnipeds, sirenians, sea otters and polar bears. They are an informal group, unified only by their reliance on marine enviro ...

s, and is the largest species of copepod.

Biology

Like most parasitic copepods it is the female which is parasitic in ''Pennella'' while the males are free swimming. The female has a two host life cycle and egg production commences when an inseminated female settles on its ultimate host, usually a large marine fish such as a member of the cod family

Gadidae The Gadidae are a family of marine fish, included in the order Gadiformes, known as the cods, codfishes, or true cods. It contains several commercially important fishes, including the cod, haddock, whiting, and pollock. Most gadid species ar ...

tuna A tuna (: tunas or tuna) is a saltwater fish that belongs to the tribe Thunnini, a subgrouping of the Scombridae ( mackerel) family. The Thunnini comprise 15 species across five genera, the sizes of which vary greatly, ranging from the bul ...

. The intermediate host is usually a

flatfish A flatfish is a member of the Ray-finned fish, ray-finned demersal fish Order (biology), suborder Pleuronectoidei, also called the Heterosomata. In many species, both eyes lie on one side of the head, one or the other migrating through or around ...

or a

cephalopod A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...

. Before the parasite settles on the intermediate host there are two free swimming or copepodid larval stages, after which it settles on the gill tips of the intermediate host as a

sessile Sessility, or sessile, may refer to: * Sessility (motility), organisms which are not able to move about * Sessility (botany), flowers or leaves that grow directly from the stem or peduncle of a plant * Sessility (medicine), tumors and polyps that ...

chalimus larva. After four chalimus stages on the intermediate host the parasite becomes sexually mature and the free swimming males begin to copulate with the females while they are still sessile, a week after attaining maturity the females leave the intermediate host. Whether or not the females have copulated they become free swimming and the males will inseminate free swimming females as well. After a brief period as a free swimming animal the female infects its ultimate host and begins its main period of adult growth and begins to release eggs into the water.

Species

The genus contains 15 species: *''

Pennella balaenopterae ''Pennella balaenopterae'' is a large ectoparasite, ectoparasitic copepod specialising in parasitising marine mammals. It is the largest member of the genus ''Pennella'', the other species of which are parasites of larger marine fish. Descriptio ...

'' Koren & Danielssen, 1877 *'' Pennella cylindrica'' (Brady, 1883) *'' Pennella diodontis'' Oken, 1815 *'' Pennella elegans'' Gnanamuthu, 1957 *'' Pennella elongata'' (Lubbock, 1860) *'' Pennella exocoeti'' (Holten, 1802) *'' Pennella filosa'' (Linnaeus, 1758) *'' Pennella hawaiiensis'' Kazachenko & Kurochkin, 1974 *'' Pennella instructa'' C. B. Wilson, 1917 *'' Pennella makaira'' Hogans, 1988 *'' Pennella oxyporhamphi'' Sebastian, 1966 *'' Pennella sagitta'' (Linnaeus, 1758) *'' Pennella selaris'' Kirtisinghe, 1964 *'' Pennella tridentata'' Listowsky, 1892 *'' Pennella varians'' Steenstrup & Lütken, 1861

References

{{Taxonbar, from=Q4291877 Siphonostomatoida Copepod genera Taxa named by Lorenz Oken