Homarus is a genus of , which include the common and commercially significant species Homarus americanus (the American lobster) and Homarus gammarus (the European lobster).
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
Cape lobster from South Africa, which is even smaller, and has hairy claws.
[ftp://ftp.fao.org/docrep/fao/009/t0411e/t0411e09.pdf, pp. 51–86 in Holthuis (1991).]
While analyses of morphology suggest a close relationship between Homarinus and Homarus, molecular analyses using mitochondrial DNA reveal that they are not sister taxa.
Species
Eight extinct species are known from the
fossil record,
which stretches back to the
Cretaceous,
but only two species survive. These two species, the
American lobster and the
European lobster, are very similar and may have
speciation as recently as the
Pleistocene, 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 in
H. americanus but not in
H. gammarus.
[ In Holthuis (1991).]
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Mostly around the British Isles. |
| Atlantic coast of North America, from Labrador in the north to Cape Hatteras, North Carolina in the south |
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Fossil species
The boundaries between
Homarus and the extinct genus
Hoploparia are unclear, and some species, such as
Hoploparia benedeni 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
-
Homarus davisi Stenzel, 1945 – lower Turonian
-
Homarus fami Garassino, Pasini, Nyborg, Haggart, 2021 – Albian
-
Homarus lehmanni Haas, 1889 – Rupelian
-
Homarus mickelsoni (Bishop, 1985) – lower Campanian
-
Homarus morrisi Quayle, 1987 – Eocene
-
Homarus neptunianus Polkowsky, 2004 – Oligocene
-
Homarus travisensis Stenzel, 1945 – middle Albian
Distribution
The two extant species of
Homarus are both found in the North Atlantic Ocean.
H. americanus is found from
Labrador to
North Carolina in the western North Atlantic,
while
H. gammarus is found from
Arctic Norway to
Morocco, including the
British Isles and the Mediterranean Sea.
Life cycle
Mating in
Homarus is complex and is accompanied by a number of courtship behaviours.
Males build mating shelters or burrows, and larger males can attract more females, producing a polygynous mating system.
A few days before
ecdysis, a female will choose a mate, and will remain in his shelter until the moult. The male will then insert a
spermatophore into the female's seminal vesicle, where it may be stored for several years.
The eggs of
Homarus species are laid in the autumn, being fertilised externally as they exit, and are carried by the female on her
.
The eggs generally hatch in the spring as a pre-larva, which rapidly develops into the first larval phase.
As adults, Homarus species moult increasingly infrequently. The size at sexual maturity varies with temperature; it is around for female H. americanus in southern New England, but around the Bay of Fundy.
Notes
Bibliography
External links
