''Homarus'' is a

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 ...

of lobsters, which include the common and commercially significant species ''Homarus americanus'' (the American lobster) and ''

Homarus gammarus ''Homarus gammarus'', known as the European lobster or common lobster, is a species of clawed lobster from the eastern Atlantic Ocean, Mediterranean Sea and parts of the Black Sea. It is closely related to the American lobster, ''H. ameri ...

'' (the European lobster). The

Cape lobster The Cape lobster, ''Homarinus capensis'', is a species of small lobster that lives off the coast of South Africa, from Dassen Island to Haga Haga. Only a few dozen specimens are known, mostly regurgitated by reef-dwelling fish. It lives in rock ...

, which was formerly in this genus as ''H. capensis'', was moved in 1995 to the new genus ''Homarinus''.

Description

''Homarus'' is one of three extant genera of clawed lobsters to show dimorphism between claws – a specialisation into a crushing claw and a cutting claw. The other similar genera are '' Nephrops'', which is much more slender, and has grooves along the claws and the abdomen, and '' Homarinus'', the

from South Africa, which is even smaller, and has hairy claws. tp://ftp.fao.org/docrep/fao/009/t0411e/t0411e09.pdf Subfamily Nephropinae Dana, 1852 pp. 51–86 in Holthuis (1991). While analyses of

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts * Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...

suggest a close relationship between ''Homarinus'' and ''Homarus'', molecular analyses using mitochondrial DNA reveal that they are not

sister taxa In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

. Both genera lack ornamentation such as spines and carinae, but are thought to have reached that state independently, through

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...

. The closest living relative of ''Homarus'' is ''

Nephrops norvegicus ''Nephrops norvegicus'', known variously as the Norway lobster, Dublin Bay prawn, ' (compare langostino) or ''scampi'', is a slim, orange-pink lobster which grows up to long, and is "the most important commercial crustacean in Europe". It is n ...

'', while the closest relatives of ''Homarinus'' are ''

Thymops ''Thymops birsteini'', the Patagonian lobsterette, is a species of lobster found around the coasts of South America, particularly the South Atlantic. It belongs to the monotypic genus ''Thymops''. Distribution ''T. birsteini'' is found on the co ...

'' and '' Thymopides''.

Species

Eight extinct species are known from the

fossil record A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

, which stretches back to the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

, but only two species survive. These two species, the American lobster and the

European lobster ''Homarus gammarus'', known as the European lobster or common lobster, is a species of clawed lobster from the eastern Atlantic Ocean, Mediterranean Sea and parts of the Black Sea. It is closely related to the American lobster, ''H. americ ...

, are very similar and may have speciated as recently as the

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...

, during climatic fluctuations. The best characters for distinguishing them are the geographic distribution, with the American lobster in the western Atlantic and the European lobster in the eastern Atlantic, and by the presence of one or more teeth on the underside of the

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ships * Ros ...

in ''H. americanus'' but not in ''H. gammarus''.

Fossil species

The boundaries between ''Homarus'' and the extinct genus ''

Hoploparia ''Hoploparia'' is a genus of fossil lobster belonging to the family Nephropidae. The type species of this genus is ''Hoploparia longimana''. These epifaunal carnivores lived from the Jurassic to the Paleogene The Paleogene ( ; also spelled ...

'' are unclear, and some species, such as ''

Hoploparia benedeni ''Hoploparia benedeni'' is a species of fossil lobster found in Cretaceous rocks in northern France. It was first described in 1886 by Paul Pelseneer. Stratigraphy and taxonomy The type specimen was discovered in 1868 near Grandpré, Ardennes ...

'' have been transferred between the two genera. Eight species have been assigned to ''Homarus'' from the fossil record. They are: *'' Homarus brittonestris'' Stenzel, 1945 – lower

Turonian The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous Epoch, or a stage in the Upper Cretaceous Series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded b ...

*'' Homarus davisi'' Stenzel, 1945 – lower

*'' Homarus hakelensis'' (Fraas, 1878) – Cenomanian *'' Homarus lehmanni'' Haas, 1889 –

Rupelian The Rupelian is, in the geologic timescale, the older of two ages or the lower of two stages of the Oligocene Epoch/ Series. It spans the time between . It is preceded by the Priabonian Stage (part of the Eocene) and is followed by the Chattian ...

*'' Homarus mickelsoni'' (Bishop, 1985) – lower

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campani ...

*'' Homarus morrisi'' Quayle, 1987 –

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

*'' Homarus neptunianus'' Polkowsky, 2004 – Oligocene *'' Homarus travisensis'' Stenzel, 1945 – middle

Albian The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous Epoch/ Series. Its approximate time range is 113.0 ± 1.0 Ma to 100.5 ± 0 ...

Distribution

The two extant species of ''Homarus'' are both found in the

North Atlantic Ocean 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 ...

. ''H. americanus'' is found from

Labrador , nickname = "The Big Land" , etymology = , subdivision_type = Country , subdivision_name = Canada , subdivision_type1 = Province , subdivision_name1 ...

North Carolina North Carolina () is a state in the Southeastern region of the United States. The state is the 28th largest and 9th-most populous of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, Georgia and ...

in the western North Atlantic, while ''H. gammarus'' is found from

Arctic Norway Arctic Norway ( no, Det arktiske Norge) comprises the northernmost parts of Norway that lie above the Arctic circle. Norway reaches from approximately 58°N to 81°N, so large parts lie north of the Arctic circle at 66°33′. In Norway, the nam ...

Morocco Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria t ...

, including the

British Isles The British Isles are a group of islands in the North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner and Outer Hebrides, the Northern Isles, ...

and the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ...

Life cycle

Mating In biology, mating is the pairing of either opposite- sex or hermaphroditic organisms for the purposes of sexual reproduction. ''Fertilization'' is the fusion of two gametes. ''Copulation'' is the union of the sex organs of two sexually reprod ...

in ''Homarus'' is complex and is accompanied by a number of

courtship Courtship is the period wherein some couples get to know each other prior to a possible marriage. Courtship traditionally may begin after a betrothal and may conclude with the celebration of marriage. A courtship may be an informal and private m ...

behaviours. Males build mating shelters or burrows, and larger males can attract more females, producing a polygynous mating system. A few days before moulting, a female will choose a mate, and will remain in his shelter until the moult. The male will then insert a

spermatophore A spermatophore or sperm ampulla is a capsule or mass containing spermatozoa created by males of various animal species, especially salamanders and arthropods, and transferred in entirety to the female's ovipore during reproduction. Spermatophores ...

into the female's seminal vesicle, where it may be stored for several years. The

eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

of ''Homarus'' species are laid in the autumn, being fertilised externally as they exit, and are carried by the female on her pleopods. The eggs generally hatch in the spring as a pre-larva, which rapidly develops into the first larval phase. This is followed by three

zoea Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow. The ...

l phases, the total duration of which can vary from two weeks to two months, depending on the temperature. At the following moult, the young animal becomes a post-larva, with a gross form resembling the adult lobster. Although it can swim, using its pleopods, the post-larva soon settles to the bottom and lives as a juvenile for 3–5 years. As adults, ''Homarus'' species moult increasingly infrequently. The size at

sexual maturity Sexual maturity is the capability of an organism to reproduce. In humans it might be considered synonymous with adulthood, but here puberty is the name for the process of biological sexual maturation, while adulthood is based on cultural definit ...

varies with temperature; it is around for female ''H. americanus'' in southern

New England New England is a region comprising six states in the Northeastern United States: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. It is bordered by the state of New York (state), New York to the west and by the Can ...

, but around the Bay of Fundy. In ''H. gammarus'', the size at sexual maturity is less well defined, but is in the range .

Notes

References

Bibliography

External links

* {{Authority control True lobsters Crustaceans of the Atlantic Ocean Extant Albian first appearances