Lobster, solitary crustacean with large claws


Photo credit: Ranko

Whether American or European, the lobster is distinguished by a pair of disproportionately sized claws that crush as well as they cut. This article immerses us in the cold waters of the planet, so appreciated by this large crustacean. Let’s get to know a solitary animal, which has the particularities of molting throughout its life and being able to regenerate its lost legs.

What kind of animal is the lobster?

The lobster is a crustacean (it has a hard shell) and decapod (it has 10 legs). The genus Homarus includes 2 species:

The American lobster (Homarus americanus) is also called Canadian lobster, Canada being its leading exporter. The most widespread species in the world, it has a blue-green to red-brown color. Larger than its European counterpart, the American lobster has an average weight of 3 kilos and 50 cm in length. The record stands at nearly 20 kilos; The European lobster (Homarus gammarus) is also called blue lobster or Breton lobster (more rarely and only in France). This crustacean has a bluish, often dark shell, with white tips of the legs and orange antennae. It weighs on average 2 kilos for a size of 35 cm. What are the physical characteristics of the lobster?

As a decapod crustacean, the lobster has an exoskeleton, articulated legs, antennae, and breathes through gills. Its body consists of a cephalothorax (the head and thorax are in one piece), and an abdomen comprising 5 parts. The animal is best known for its large pincers, the usefulness of which we will study in more detail below. Interesting fact: if the lobster loses one of its limbs, it can regenerate it during its successive molts. The regeneration of legs or claws is a crucial adaptation for the survival of these animals which can lose their appendages during territorial fights or encounters with predators. Also called autotomy, this phenomenon requires a lot of energy from the lobster and may require several molts before the new leg reaches full functionality.

What are lobster claws used for?

Located on the cephalothorax, the 5 pairs of lobster legs each have a specific function:

The first pair of legs, placed at the front, grows disproportionately. It is made up of chelipeds ending in pincers. The largest (nicknamed “hammer pincer” or “crusher pincer”) is used to crush the shell of its prey. The smallest (called “scissor pliers” or “cutting pliers”) has sharper edges, useful for cutting flesh. Also faster, this pincer is used to defend itself and capture small fish and then carry them to its masticatory apparatus; The other 4 pairs of legs, called pereiopods, are mainly used for locomotion. In which waters of the world do lobsters live?

Although the distribution area differs depending on the species, lobsters have in common that they prefer cold seas:

The American lobster lives in the Atlantic Ocean, along the coasts of North America. In the United States, it occurs primarily off North Carolina and in the Gulf of Maine. Lobster is especially abundant in Canada, in the Strait of Belle-Isle between Labrador and Newfoundland, in the southern Gulf of St. Lawrence, as well as all along the coast of the Gulf which borders the maritime provinces (Gaspésie, Nova Scotia, New Brunswick). The crustacean is also found in the French archipelago of Saint-Pierre and Miquelon; The European lobster is distributed in coastal waters from Norway to Morocco (Atlantic, English Channel, North Sea, western and central Mediterranean). The species lives near the French coast, off the coast of Cotentin, towards the Channel Islands and also in British waters. How does the lobster set up its burrow?

The lobster is found from the bottom of the infralittoral level (at the limit of the areas emerged at low tide) to a depth of 50 m. The decapod crustacean favors rocky bottoms in which it can hide. Failing that, it digs a sort of burrow under large stones or a basin in malleable substrates (mud, gravel) in order to shelter there. These materials allow the construction of galleries as well as 2 entrances and 2 exits minimum. Lobsters rarely live in sandy areas which are too unstable to provide solid shelter. Outside of the breeding season, this solitary creature spends its days in its burrow, access to which it blocks with its 2 large pincers.

What do lobsters eat?

At nightfall, this nocturnal species leaves its burrow in search of food. A carnivorous predator, the lobster essentially composes its menu with invertebrates living on the seabed. Its diet includes other crustaceans (crabs), mollusks (mussels, clams) but also periwinkles, marine worms, sea urchins. , starfish, fish and can occasionally consume some algae. To facilitate its research, the lobster relies mainly on its antennae equipped with small sensory hairs, called chemoreceptors, which are capable of detecting chemical molecules (pheromones, amino acids, etc.) emitted by other organisms. Its appendages also detect movements and vibrations in the water, allowing it to spot the presence of potential prey, even in the dark.

How do lobsters reproduce?

Reproduction occurs in the days following the female’s molt, which then becomes “soft”. This diffuses chemical substances (sex pheromones) which inhibit aggressiveness and induce seductive behavior in the male (which remains “tough”). After mating, the pair shares the same burrow for a few days, then separates. Between the months of June and August, the female remains at the bottom of the burrow on her back and lays up to 40,000 eggs, which she places on her abdominal appendages, as they are expelled. Firmly anchored by filaments, the eggs hatch 8 months later to release larvae measuring a few millimeters. During their planktonic life, the larvae are prey to a multitude of marine animals (fish, anemones, crabs, cuttlefish, etc.) to the point that their survival rate is estimated at less than 2%. After 4 moults, they adopt the shape and behavior of small lobsters and settle on the bottom.

What is the life expectancy of a lobster?

The slow development of the juvenile extends over approximately 5 years, during which it molts around twenty times to become an adult. During molting, the lobster takes refuge at the bottom of its burrow, stops feeding then folds into a V shape. The membrane that connects its cephalothorax to its abdomen tears, leaving a cavity through which it can exit and swell with water to reach a larger size. During its life, the crustacean only shows signs of aging late and continues to reproduce throughout its existence. It ends up dying when, having become too big, it no longer has the energy necessary to begin a new molt. The wear and tear of the shell and the resulting diseases sound the death knell for the crustacean which can, however, live for around fifty years.

Is the lobster an endangered species?

We saw above that during the larval stage, lobster predators are numerous. Juveniles measuring a few centimeters are the prey of large fish, cuttlefish, octopuses and crabs. Outside of the moulting period, adult lobsters only have humans as predators. During the 17th and 18th centuries, the crustacean was so abundant and accessible in Europe that it was used as bait for fishing or to feed prisoners and common people. Little appreciated, the animal was nicknamed the “sea cockroach” but over time, it became a delicacy and sought after. After the Second World War, lobster populations experienced a sharp decline in a large part of their range, particularly in the northern hemisphere, before recovering in the late 1980s. Today, the American lobster and European lobsters are not considered globally threatened species. In most regions, their numbers are relatively stable, while in others, they may face pressures due to overfishing and eutrophication of their environment.

Does the lobster feel pain?

The question regularly comes up in the news and sparks lively debates. For some scientists, the lobster’s nervous system is much less complex than that of vertebrates, and the size of its brain is too small to be able to transmit signals associated with pain. Experiments carried out in 2013 at Queen’s University Belfast established that crustaceans avoid situations causing suffering and wiggle their injured legs. According to this study, this reaction involves the feeling of pain. Other researchers suggest that their behavior is an instinctive response to ensure their survival. When in doubt, some countries have taken the lead by legislating. For example, Norway, Austria, Switzerland and New Zealand have banned the boiling of live lobsters. Regulations stipulate that shellfish must be stunned before being boiled, in order to limit the stress and suffering these animals could experience.

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