American
Lobster
Homarus americanus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Malacostraca
Order: Decapoda
Suborder: Pleocyemata
Infraorder: Astacidea
Superfamily: Nephropoidea
Family: Nephropidae
Genus: Homarus
Species: H. americanus
Binomial name
Homarus americanus
The American lobster is a species of lobster (scientific
name Homarus americanus), also known as the northern lobster,
or the Maine lobster. They thrive in cold, shallow waters
where there are many rocks and other places to hide from
predators. Lobsters are solitary and nocturnal.
Found along the coast of North America as far south as
North Carolina, they are famously associated with the
colder waters around the Canadian Maritimes, Newfoundland
and Labrador, Massachusetts, and Maine, where they can
grow to enormous sizes. They commonly range from 20cm
to 60cm in length and 0.5kg to 4kg in weight, but have
been known to reach lengths of well over 1 meter and weigh
as much as 20kg or more, making this is the heaviest marine
crustacean in the world.
The adult lobster's main natural enemy is the codfish,
but other enemies include haddock, flounder, and other
lobsters. Overfishing of cod in the early 20th century
has allowed the lobster population to grow enormously.
Molting and Mating
Lobsters shed their shells 2-3 times per year while juvenile,
but only once a year or less often when fully mature,
about 4 to 7 years old. When the lobster gets near its
next shedding period, it will start to grow a new shell
underneath the current one. The outer shell will become
very hard and darken, becoming covered with black marks
that look like scratches. (They are now known, very unimaginitively,
as hardshells.) The line that runs along the back of the
lobster's carapace will begin to split, and the two halves
of the shell will fall away. Claws and tail will be pulled
out from the old outer shell, as the inner shell is very
malleable. The old shell is often eaten for calcium recovery
and the leftovers are sometimes buried.
Females can only mate right after molting, but larger
females can store sperm for several batches of eggs from
a single coupling. All females store the sperm to fertilize
eggs later, not at the time of copulation. While getting
ready to molt the female will find the den of a suitable
male and visit it several times. When finally ready to
molt the female will do so in that den. After the molt
the male will wait for the shell to start to harden, gently
stroking the paper thin new shell with his large antennae.
After several minutes male will raise himself on his claws
and tail, then use his legs to flip over the female and
get on top. The male has a pair of hardened swimmerets,
or fins on the bottom, that match a pair of swimmerets
on the female which have an opening between them. The
sperm, contained in a gelatinous blob called a spermatophore
slides down notches in the male's swimmerets into the
female. The outside end of the spermatophore hardens to
block the hole. The receptacle on the female is part of
her shell so she will need to use the sperm before her
next molt or lose it. The male dismounts and then may
eat the female's shell. The female will then stay in the
den for several days while her shell hardens more. Lobsters
do not mate for life, contrary to some myths. The female
seeks the most alpha male she can find, and the male will
mate with as many females as he can.
In the first two weeks after molting, lobsters are very
vulnerable, as their shells are so soft they can neither
move very fast nor defend themselves with their claws.
They will often fall prey to other lobsters, especially
egg-bearing females, who become very defensive when carrying
their eggs.
A lobster can locate the direction a smell is coming from
much the same way we can hear the direction a sound comes
from. In addition to sensing the presence of a smell,
the antennules can judge water speed to improve direction
finding.
Eyes:
The eyes of these lobsters are different from almost all
other animals. Rather than using lenses to focus light
on sensitive cells, narrow tapered channels lined with
a crystalline material reflect the light on the retinal
cells. This same design is proving useful for focusing
x-rays and other hard to refract light -- as in the namesake
Lobster-ISS x-ray telescope.
Legs and Claws
The first pair of a lobster's ten legs are the called
the claws and are usually used for hunting and fighting,
not locomotion. The other eight legs are used for walking.
At first the claws of a lobster are both identical, but
with use the lobster will start to favor one over the
other. The favored claw will get bigger and be filled
with primarily slow-acting muscle tissue which cannot
react quickly, but does not tire quickly either. This
is the crusher claw. The other claw, the pincher, will
develop fast-acting muscle tissue useful for grabbing
prey quickly. During lobster to lobster fights, one typical
move is claw lock where the two lobsters will grab each
other's crusher claw and have a showdown of muscle and
shell strength.
Eggs
They are green, and very small, about 1 mm in diameter.
They are carried by the female on the underside of the
tail for a period of about one month, whereupon they are
released over several days and hatch. The number of eggs
carried by a single female can range well into the tens
of thousands, but the survival rate is very low, speculated
at around 0.1 percent. Older females produce vastly more
eggs than younger ones. In one observation (Francis Herrick,
in the 1890s) 5-inch (13 cm) females were found to have
about 4,000 eggs, while 10 inch (25 cm) ones produced
about 50,000 eggs.
Eggs and newly hatched lobsters can by carried very long
distances by ocean currents. Within the egg lobsters molt
thirty-five times. At the time of hatching, the larva
still looks more like a shrimp than a lobster. For several
weeks, the larva floats near the surface of the sea, eating
and growing. It has small fins that allow some movement,
but not real swimming. The final juvenile stage, the postlarva
stage, has been called the "superlobster" by
some. It is the only time in a lobster's life that it
can swim forward, an act which bears some resemblance
to Superman flying. At this age the lobster is about 2
cm long. This stage lasts a week or two, during which
the lobster will swim during the day, at speeds of up
to 20 cm per second -- fast enough to cover 10 km per
day. The superlobster will seek a rocky bottom with good
hiding places. Without anywhere to hide it quickly falls
prey to small fish, such as sculpin and cunner.
For a lobster to be kept by fishermen in the United States,
the carapace must span at least 3 and 1/4 inches (8.255
cm) between the eye socket and the first tail joint. In
Maine, there is also a legal maximum of 5 inches (12.7
cm), but in parts of some states, such as southeastern
Massachusetts, there is none. To protect known breeding
females, lobsters that are caught carrying eggs are to
be notched on a tail flipper (second from the right, if
the lobster is right-side up and the tail is fully extended).
Following this, the female cannot be kept or sold, and
is commonly referred to as a "punch-tail" or
as "v-notched". The maximum size in Maine ensures
that there will be older males to mate with the protected
females.
Lobsters as a food
They are a popular food, commonly boiled or steamed; for
either method, they must be alive until they are cooked
to avoid food poisoning. They can survive out of water
for up to two days if kept refrigerated.
Lobster on its own is very low fat but not suitable for
low sodium diets. One common way of serving lobster tail
is in surf and turf. They have a greenish or brownish
organ called the tomalley that performs the functions
of the liver and pancreas in a human, i.e. it filters
out toxins from the body. Some diners consider it a delicacy,
but others avoid it, considering it a toxin source.
Lobster Types
• American lobster (Homarus americanus)
• Blue
Lobster
• Cape lobster (Homarus capensis)
• European lobster (Homarus gammarus)
• New Zealand lobster (Metanephrops challengeri)
• Norway lobster (Nephrops norvegicus)
• Red lobster (Eunephrops bairdii)
See also
• Spiny
Lobster
• Tomalley (the soft green liver of the lobster)
• Bubba the lobster
• How
to Boil Lobster
• How
to Eat Lobster
• Live
Maine Lobsters
This article is licensed under the GNU
Free Documentation License.
It uses material from the Wikipedia
article "American Lobster".
|
