Lobster Molting: How Do Lobsters Grow?

Estimated reading time: 11 minutes

Let’s dive into the captivating world of lobster molting, and how lobsters grow. These clawed crustaceans aren’t just a delicious culinary delicacy celebrated for their sweet and succulent meat. Lobsters are fascinating creatures that like other species with exoskeletons made up of chiton go through the dangerous and laborious process of molting.

The next time you crack into a lobster and go for that butter dip, take a moment and think about this incredible invertebrate and the journey it goes through. This article will dive into the complex process of molting as well as how molting in lobsters makes them vulnerable to microorganisms, fungi, and pathogens.

Overview of Lobster Anatomy and Molting

Before we can break down the process of how lobsters molt, we need to begin by understanding their anatomy. The hard outer shell of lobsters is called an exoskeleton. It protects the lobster and keeps it safe. However this hard shell doesn’t grow with the lobsters and will need to be shed multiple times of the life of the lobster.

Outer Anatomy of Lobsters

• Antenna – Lobsters have four long thing antennas covered with tiny hairs. These allow the lobsters to smell.
• Carapace – This is the hard, armor like shell from eyes to above the tail, minus the claws, knuckles, and tail. The stalks, and eyes that are located on the long stalks, are attached to the carapace.
• Legs – Lobsters have 10 legs. Eight legs were used for walking while the other two called the pincers have the claws attached to them.
• Tail – This makes up the largest piece of meat in the lobster. Combined with the tail helps the lobster swim and can also be used in defense.
• Claws – The claws of the lobster are used both to catch their food as well as protect themselves against predators. The larger of the two claws is called the crusher claw while the smaller one is called the pincer or cutter claw. The claws are attached to the knuckles of the lobster which is believe by many to be the tastiest bite of the lobster.

Internal Anatomy of Lobsters

• Digestive System – Lobsters have a three-part digestive system – foregut, midgut, and hindgut. The foregut breaks down food, the midgut absorbs nutrients, and the hindgut eliminates waste. They also have grinding teeth for breaking down hard-shelled prey
• Circulatory System – Lobsters have an open circulatory system, meaning their blood is not always contained within blood vessels. Instead, their blood flows through a series of sinuses and cavities. Lobsters have clear-colored blood that turns blue due to copper in their blood cells. Their circulatory system also includes a heart, which pumps blood throughout their body.
• Nervous System – Lobsters have ganglia throughout their body, allowing them to react to stimuli and sense their surroundings. They also possess compound eyes and antennae to navigate their environment.
• Respiratory System – Lobsters breathe through the gills in their abdomen. Water flows over the gills to extract oxygen. Swimmerets on their abdomen help move water over the gills.
• Reproductive System – Male lobsters have a pair of reproductive organs called testes, while female lobsters have ovaries. During mating, the male transfers sperm to the female using specialized appendages called gonopods. Female lobsters carry fertilized eggs on their pleopods (swimmerets) until they hatch into larvae.

The Molting Cycle of Lobsters

The molting process gets its start with a hormonal change. Hormones are released, softening the exoskeleton between the abdomen and tail. To get out of its old shell, the body shell splits and the skin between the tail and body shell opens. Next the lobster rolls over on its side and bends itself almost in half to pull itself out of its old shell. The new shell lobster then pumps itself with fluid to enlarge the very soft shell.

Once a lobster has molted, it  absorbs sea water to rehydrate as quickly as possible which lowers the concentration of protein in the lobster’s hemolymph (or blood).The new shell is paper thin and the lobster is very vulnerable to predators at this time. The lobster then focuses on feeding and “filling” up that new shell and, as it does that, the protein level increases.

Molting and Lobster’s Vulnerability to Microorganisms

When lobsters molt, they are at their most vulnerable. Until their soft shells harden they’re susceptible to predators and microorganisms. It is much easier for microorganisms to penetrate through a lobster’s shell during the molting process and right after when the new shell is soft. Once microorganisms have penetrated the shell they can then cause infection and disease.

Microbial Ecology of Lobsters

You might be wondering what is a microbe and how does it relate to lobster molting? There are nine major types of microbes. Bacteria, protozoa which is similar to bacteria, fungi, algae, slime molds, lichen, viruses, and prion make up the most common microbes. Lobsters molt throughout their lifespan making them more vulnerable to several types of microbes during this period of time.

Microbial Colonization in Lobsters

The two parts of the body most susceptible to microbes in the lobster are the shell, and the gut. Especially during the period that the lobster is molting its shell or after it has just molted its shell, it allows bacteria, viruses, fungi, and other types of microbes to enter its system. Vibrio is the most common microbe in the lobster’s gastrointestinal tract while bacteria are the most common in the shells. However, it varies by not only the location of the lobsters but also the temperature of the water.

Pathogenic Bacteria Affecting Lobster Meat

Part of enjoying lobster in varies dishes such as lobster rolls, lobster risotto, and lobster pizza is knowing all about food safety. Lobster, just like any other seafood or even ingredients needs to be both handled and cooked properly. It’s especially important to understand for those that might be immune compromised.

Vibrio Parahaemolyticus and Vibrio Vulnificus

These are both species of gram negative bacteria. They are commonly found in warm, salty water and are more likely to affect species like spiny lobster, rock lobster, and Caribbean lobster. Both can cause gastrointestinal illnesses.

Listeria Monocytogenes

This bacteria can cause serious illness in young children, the elderly, and those with compromised immune systems. Unlike the above two bacteria, this has been found in cold water lobsters such as Atlantic Maine lobster. Symptoms include headaches, body pain, nausea, stiffness, and even miscarriages in pregnant women.

Salmonella Spp.

While salmonella is more commonly associated with poultry, dairy, meat, and eggs, it can be found in seafood as well. However, you are more likely to find it in other types of seafood such as shrimp and fish.

Spoilage Bacteria

It’s easy to tell when both raw lobster meat and cooked lobster meat have gone bad. Aside from the smell, you can also tell by the color. If the meat is green, white, or grayish in color you can tell the meat has gone bad because of bacteria. You also always want to avoid lobster meat that is slimy, or has any sort of film on it. This is why it’s so important to always source your lobsters from a reputable and dependable business like LobsterAnywhere.

Microbial growth is the main cause of spoilage not just in lobsters, but in food in general. They can invade in many different ways including from the blood stream, the gills, and even the flesh of fish. When lobsters molt and they no longer have their hard, protective shell, this is an easy way for bacteria to enter the system. Two of the most common bacteria that cause spoilage are psuedomonas spp. and shewanella putrefaciens. However, shewanella putrefaciens is much more common in warm climates and is more likely to affect spiny lobsters and rock lobster.

What is Lobster Shell Disease?

Epizootic Shell Disease is an infection of the outer shell of the American lobster that is caused from chitinolytic bacteria. This disease causes a degradation of the shell as well as lesions. It can also lead to secondary infections and ultimately death.

Lobsters that suffer from epizootic shell disease also molt more often. Lobster with this disease have higher levels of the hormone that stimulates molting, ecdysone. Because the disease causes lesions that can make the shell adhere to the bodies of the lobster, the shell can get stuck causing them to struggle and eventually die. Climate change and warmer water temperatures are thought to be one of the causes of this disease.

Viruses in Lobsters

Unlike other types of microbes in lobster, viruses in lobster is much more rare. The only known virus in clawed lobsters like Maine lobster is the Homarus gammarus nudivirus. Warm water lobsters, which are a different species and more closely related to shrimp, have been noted to have white spot syndrome. White spot syndrome is more commonly found in farm raised species like shrimp and can kill an entire population.

How to can you tell a lobster that just molted?

Marine Scientist, Joseph Kunkel explains that you can identify when a lobster molted by the presence of hemolymph. This is the blood protein present in lobsters. A newly molted lobster does not accumulate enough of this protein because it is needed to build its new exoskeleton. This is also why you will not find the presence of the white gelatinous substance in a cooked soft-shell lobster. The hard shell lobster, on the other hand, will have more meat and higher hemolymph protein levels as evidence by congealed blood when cooked.

Shell Color of Molted Lobsters

The color of a hard-shell lobster’s meat is also different than that a soft-shell lobster. You will notice that a soft-shell lobster has a brighter red color, due to the carotenoid pigments becoming more concentrated right before, or right after, a lobster molts. A hard-shell lobster’s meat is also red, but it’s a bit duller in color.

Some prefer hard shells for their meaty taste and firm, dense texture. While others prefer the sweeter, tender taste of soft shells. Learn more about the differences in hard shell lobsters versus soft shell lobsters.

Lobster Molting Facts

• Hard shell lobsters have more meat than a softshell lobster. Here at LobsterAnywhere we only sell hard shell, Maine Grade A lobster. Not only do soft shell lobsters have less meat, but they are more fragile and susceptible to injury.
• It takes a lobster about 30 minutes to complete the molting process, but it can take several weeks for the soft shell to fully harden.
• The molting process in lobsters is caused by the release of a hormone called ecdysone.
• Lobsters never stop molting. They will molt multiple times throughout their lifespan. On average a lobster will molt around 25 times in their first 5-7 years of life.
• Female lobsters generally only mate when they are in their soft shell state.

Frequently Asked Questions

What type of Lobster Does LobsterAnywhere Sell?

Here at LobsterAnywhere , we sell the American Lobster, aka Homarus Americanus, a species of lobster found on the Atlantic coast of North America. These cold water lobsters are straight off the Maine coast, only have two large claws and whiter meat than warm water lobsters, and are what people think of when they refer to Maine lobster. The Maine lobster is available as hard shell lobsters, which is what we ship live.