''Nomeus gronovii'', the man-of-war fish, or bluebottle fish, 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 ...

of fish in the family Nomeidae, the driftfish. It is native to the

Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contine ...

and

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by t ...

s, where adults are generally found at depths from . It is notable for its ability to live within the deadly tentacles of a

siphonophore Siphonophorae (from Greek ''siphōn'' 'tube' + ''pherein'' 'to bear') is an order within Hydrozoa, which is a class of marine organisms within the phylum Cnidaria. According to the World Register of Marine Species, the order contains 175 specie ...

, the

Portuguese man o' war The Portuguese man o' war (''Physalia physalis''), also known as the man-of-war, is a marine hydrozoan found in the Atlantic Ocean and the Indian Ocean. It is considered to be the same species as the Pacific man o' war or blue bottle, which is ...

, upon whose tentacles and gonads it feeds. The fish is striped with blackish-blue blemishes covering its body, and the

caudal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

is extremely forked. It can reach a length of . It is of minor importance to

commercial fisheries Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often p ...

. This species is the only known member of its

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

Toxin avoidance

Rather than using mucus to prevent

nematocysts A cnidocyte (also known as a cnidoblast or nematocyte) is an explosive cell containing one large secretory organelle called a cnidocyst (also known as a cnida () or nematocyst) that can deliver a sting to other organisms. The presence of this c ...

from firing, as is seen in some of the

clownfish Clownfish or anemonefish are fishes from the subfamily Amphiprioninae in the family Pomacentridae. Thirty species of clownfish are recognized: one in the genus '' Premnas'', while the remaining are in the genus '' Amphiprion''. In the wild, t ...

sheltering among sea anemones, the fish appears to use highly agile swimming to physically avoid tentacles.Jenkins, R. L. (1983): Observations on the Commensal Relationship of ''Nomeus gronovii'' with ''Physalia physalis''. ''Copeia, Vol. 1983, No. 1 (Feb. 10, 1983), pp. 250-252''Purcell, J. E. & M. N. Arai (2001):
Interactions of pelagic cnidarians and ctenophores with fish: a review.
''Hydrobiologia, May 2001, Volume 451, Issue 1-3, pp 27-44 '' The fish has a very high number of

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristi ...

e (41), which may add to its agility and primarily uses its pectoral fins for swimming—a feature of fish that specialize in maneuvering tight spaces. It also has a complex skin design and at least one

antigen In immunology, an antigen (Ag) is a molecule or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune respons ...

to the man o' war's toxin. Although the fish seems to be 10 times more resistant to the toxin than other fish, it can be stung by the dactylozooides (large tentacles), which it actively avoids. The smaller gonozooids do not seem to sting the fish and the fish is reported to frequently "nibble" on these tentacles.

Naming

The specific name honours the

Dutch Dutch commonly refers to: * Something of, from, or related to the Netherlands * Dutch people () * Dutch language () Dutch may also refer to: Places * Dutch, West Virginia, a community in the United States * Pennsylvania Dutch Country People E ...

zoologist Zoology ()The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the animal kingdom, including the structure, embryology, evolution, classification, habits, and d ...

Laurentius Theodorus Gronovius (1730-1777). File:FMIB 51424 Portuguese-Man-of-War-Fish Nomeus gronovii.jpeg File:Nomeus gronovii north carolina.jpg File:Nomeus_gronovii_(Man-of-war_fish).gif

References

{{Taxonbar, from=Q1867449 Nomeidae Monotypic fish genera Fish described in 1789 Taxa named by Johann Friedrich Gmelin Fish of the Atlantic Ocean