''Alepas pacifica'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

goose barnacle Goose barnacles, also called stalked barnacles or gooseneck barnacles, are filter-feeding crustaceans that live attached to hard surfaces of rocks and flotsam in the ocean intertidal zone. Goose barnacles formerly made up the taxonomic order Ped ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Heteralepadidae Heteralepadidae is a family of goose barnacles. Genera The World Register of Marine Species The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an authoritative and comprehensive list of names of marine o ...

. It is a

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or wa ...

species and is an obligate associate of various species of

jellyfish Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella- ...

. It mainly occurs in the Pacific Ocean.

Description

''Alepas pacifica'' is a whitish, translucent species of stalked barnacle. Its plates are lightweight, only partially calcified and much reduced in size.

Distribution

''Alepas pacifica'' is found in tropical and subtropical waters in the Indian Ocean and the Pacific Ocean, its range extending from Australia and Malaysia to China, Japan and the western coast of North America. It is also known from the Atlantic Ocean.

Ecology

''Alepas pacifica'' lives in association with a jellyfish such as the ghost jellyfish ''Cyanea nozaki''. In this association it hangs from the margin of the bell. It is a similar colour to the whitish jellyfish, which makes it inconspicuous. It is a permanent resident, always associating with a jellyfish, and making use of the rich food supply in the surface waters in which the jellyfish floats. Other jellyfish which this barnacle uses as a

host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman * Michel Host ...

include Nomura's jellyfish (''Nemopilema nomurai''), the

egg-yolk jellyfish ''Phacellophora camtschatica'', commonly known as the fried egg jellyfish or egg-yolk jellyfish, is a very large jellyfish in the family Phacellophoridae. This species can be easily identified by the yellow coloration in the center of its body wh ...

(''Phacellophora camtschatica''), the purple-stripe jellyfish (''Chrysaora colorata''), and several other scyphozoan species. In the case of the egg-yolk jellyfish, a group of barnacles may be attached to the outside of the domed top of the bell, looking rather like an article of headwear. It is not apparent that the jellyfish is disadvantaged by the presence of the barnacle. Although normally a direct symbiont of jellyfish, this barnacle has been found attached to another barnacle of its own species which was itself attached to a jellyfish. These indirectly attached individuals were small and had longer penes than their directly attached counterparts, and may have acted as dwarf males.

References

{{Taxonbar, from=Q6569119 Barnacles Crustaceans described in 1907