Frequently Asked Questions - Lobster Anatomy
- If you look at the first pair of swimmerettes on the underside of the tail you will be able to tell if you have a male or female. If they are hard and rigid then you have a male and if they are soft and feathery you have a female. You can also tell by looking at the width of the tail. A female will have a wider tail compared with an equivalent size male, this is because she needs the extra width to carry her eggs.
- Lobsters come in just about every color. They can be blue, light yellow, greenish-brown, grey, dusty orange, white, some calico, and some with spots. Some even come in two colors, having half of their shell one color and the other half a totally different color. Of these only the white ones (true albinos) don't turn red when cooked. The hot water cuts the link between astaxanthin, a red substance contained in the lobster's shell, and protein which in cold water brings out the predominant coloring.
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A lobster can live for approximately 48 hours without water. Ensure that the lobster is kept cool and moist at all times when it is not in the water.
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Most lobsters are colored a mottled, dark greenish brown, but lobsters can also be found blue or yellow but these lobsters are very rare.
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The brain (supra-esophageal ganglion) is part of the lobster's central nervous system, which is composed of fifteen midline ganglia (groups of nerve cells). The brain receives primary visual (sight) information and olfactory (smell) information via the first pair of antennae and mechano-sensory (touch) information via the second pair of antennae. In general, the other ganglia are devoted to local control or functions within the segment where each ganglion resides. Overall, the central nervous system allows the lobster to react to its surroundings and control bodily functions.
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It is possible to collect urine from lobsters and has been done in some studies. Generally, tubing is placed over the urinary pores under the antennae with a sealant between the tubing and the carapace. Urine is then collected into whatever type of 'bag' or container is suitable for the study.
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Lobsters contain an organ call the Statocysts (organ for orientation and equilibrium) which is located at the base of its antennules. They are composed of 400-500 hairs which project into the statolith (sand granes cemented together). When the lobster shifts its orientation the fluid in the statocysts moves the hairs in a particular direction relative to the satolith. This movement stimulates some hairs more than others and gives the lobster its sense of direction and movement. This organ is also used by the lobster to give it its overall position and whether it is right side up or upside down. It functions much like a human’s inner ear.
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Lobsters use their Atennules (see diagram) for smell. They have the ability to recognize many different smells. We do not know if lobsters can hear as there has not been any evidence found to determine if lobsters are capable of hearing. Diagram courtesy of Department of Marine Resources, State of Maine
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To take blood you insert the needle just to the side of the nerve chord on the ventral sinus (bottom side of tail just slightly off the midline). For the most part lobster are conformors.
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Frequently I come across a cooked lobster where the meat is shriveled up within the shell. Is this what is referred to as a soft shell lobster or is this a lobster that is preparing to molt? Is this pre or post molted lobster?
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This occurs because the lobster is in the post-molt stage of their cycle. In a post molt the lobster has already shed it's old shell and needs to replinish on nutrients such as calcium to regain it's shell hardness. However, the shell hardness isn't the cause of making the lobster meat appear shriveled up. When a lobster is done molting there is an excess of water content inside them. When the lobster is cooked this water evaporates and makes the meat appear more shriveled then then when the lobster had a normal level of water content inside them. Another reason for the meat to be shriveled up is that they are being overcooked as well if you see this happening with lobsters that are not post molting
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The digestive system of crayfish is similar to the digestive system of lobsters. The lobster has a digestive system which consists of a long tract divided into three main regions: the foregut, midgut, and hindgut. Food is handled and processed first by the mouthparts and then is crushed by the mandibles before being swallowed. It then makes its way through the three main regions of the digestive system. Any remaining material (not digested) is packaged into fecal pellets surrounding by a mucous membrane. Contractions of the midgut force the pellets along to the hindgut and into the enlarged rectum. Rapid rectal contractions push the pellets out the anus at the base of the tail.
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Lobster blood (hemolymph) is often tested for protein concentration using a hand-held refractometer. This instrument measures the refractive index of fluids which is determined by the amount of dissolved solids, such as protein, in a sample. It is important to use a temperature-compensated instrument for these measurements. A more detailed discussion can be found through the link and reference: Measuring total protein concentration in blood of the western rock lobster (Panulirus cygnus George) by refractometry. Oliver MD and MacDiarmid AB. Blood refractive index and ratio of weight to carapace length as indices of nutritional condition in juvenile rock lobsters (Jasus edwarsii).
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Similar to insects, the nervous system of a lobster is very simple and neither insects nor lobsters have real brains. Lobsters have a series of 15 nervous ganglia that span the length of the lobster, on the ventral side or belly side, with nerves projecting from each of these ganglia. The first ganglion is the closest thing to a brain. In general, for an organism to perceive pain it must have a complex nervous system. Many scientists that are studying the nervous system of lobsters tell us that they do not process pain. Lobsters don’t have a cerebral cortex, which is where pain is processed in humans or dogs and cats. If they do feel pain, it is most definitely in a different way than humans do. A new study out of Norway concluded that most invertebrates - including lobsters, crabs, worms, snails, slugs and clams - probably don't have the capacity to feel pain.
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Yes, a lobster does have a heart; it is a single-chambered sac consisting of striated muscles with several openings called ostia. The heartbeat is controlled by the cardiac ganglia and is known as a neurogenic system (of neural origin), as opposed to that of humans - a myogenic system (of muscular origin). They do have blood; it’s called hemolymph as it is more or less composed of blood and lymph together. Just like human blood, lobster hemolymph transports blood cells as well as oxygen and other gases, nutrients, wastes, hormones and other molecules involved in the internal defense. Unlike human blood, lobster blood varies from white to grey to pink in color.
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There has been a bit of work done on Lobster DNA. There is an active research project on Lobster Genomics looking at EST (expressed sequence tags). You can find the DNA sequence data at the following website http://www.marinegenomics.org/.
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Similar to insects, the nervous system of a lobster is very simple and neither insects nor lobsters have real brains. Lobsters have a series of 15 nervous ganglia that span the length of the lobster, on the ventral side or belly side, with nerves projecting from each of these ganglia. The first ganglion is the closest thing to a brain. Lobsters have what is termed a 'simple' digestive system. The stomach contains a structure called the gastric mill made up of mineralized 'teeth' used to grind up their food. Lobsters use gills to breathe much the way that fish do - they don't have lungs. The circulatory system of a lobster consists of a heart and some arteries but lobsters do not have veins rather, their blood (hemolymph) eventually gathers in large sinuses before returning to the heart. Lobsters have muscles but no bones. The muscles are attached to their exoskeleton (shells) for support.
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The different colors are caused by genetic differences in the pigments that make up the shell color. Rather than containing all the pigments that combine to make a green-brown color the shell of a blue lobster (for an example) contains only a blue pigment. Genetic differences can also cause other strange colorings such as light orange, light yellow, greenish-brown, grey, dusty orange, white, some calico, and some with spots.
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Lobsters do not have lungs, but they have to ability to uptake oxygen from air via their gills, if they are kept moist and cool. I have never seen or heard of a holding system in which lobsters could be kept alive for up to one month, out-of-the-water. Some holding systems are using 100% chilled relative humidity but only for a few days (mist or shower systems). Trickle-down systems can hold lobster for several weeks. In trickle-down systems, lobsters are kept in plastic totes with holes at the bottom, several totes being stacked on top of each other, and where chilled water trickle down from the top tote to the one underneath until the water reaches the bottom one and then is recirculated back to the top one.
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I wonder if it wasn’t simply a foreign body in the stomach, or more likely the gastroliths (structures located in the stomach that accumulate minerals (mostly calcium) prior to molting, so it can be reabsorbed and used in the new shell). The gastroliths are white and can get over 1 cm in diameter.
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Similar to insects, the nervous system of a lobster is very simple and neither insects nor lobsters have real brains. Lobsters have a series of 15 nervous ganglia that span the length of the lobster, on the ventral side or belly side, with nerves projecting from each of these ganglia. The first ganglion is the closest thing to a brain. In general, for an organism to perceive pain it must have a complex nervous system. Many scientists that are studying the nervous system of lobsters tell us that they do not process pain. Lobsters don’t have a cerebral cortex, which is where pain is processed in humans or dogs and cats. If they do feel pain, it is most definitely in a different way than humans do. A new study out of Norway concluded that most invertebrates - including lobsters, crabs, worms, snails, slugs and clams - probably don't have the capacity to feel pain.
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The only reference that I could find on "lobster memory" is the one below with abstracts: Anim Behav. 1998 Dec; 56(6):1553-1560. Individual recognition and memory in lobster dominance. Karavanich C, Atema J. Department of Zoology, North Carolina State University American lobsters, Homarus americanus, form stable dominance relationships in captivity. Size, sex and stage in the moult cycle are important determinants for dominance. Other factors, such as recent agonistic experience play a role. This paper investigates how lobsters maintain their stable dominance relationships: they may recognize individuals or alternatively, recognize overall dominance status. We paired lobsters in two consecutive 'boxing matches'. Results indicate that lobsters remember familiar opponents when kept either in isolation or in communal tanks for 24 h between their first and second fights. Subordinates immediately backed away from familiar dominants, avoiding a second fight. In some animals, this memory lasted between 1-2 weeks if pairs were kept separate between the first and second fights. When paired for the second fight against unfamiliar dominant lobsters, subordinate lobsters from first fights actively fought and won the encounter. These results suggest that lobsters are capable of 'individual recognition'. In nature, the observed social organization of lobsters may be maintained by individual recognition of a small number of residents inhabiting separate, nearby shelters. (c) 1998 The Association for the Study of Animal Behaviour.
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The lobster has a digestive system which consists of a long tract divided into three main regions: the foregut, midgut, and hindgut. Food is handled and processed first by the mouthparts and then is crushed by the mandibles before being swallowed. It then makes its way through the three main regions of the digestive system. Any remaining material (not digested) is packaged into fecal pellets surrounding by a mucous membrane. Contractions of the midgut force the pellets along to the hindgut and into the enlarged rectum. Rapid rectal contractions push the pellets out the anus at the base of the tail.
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Lobster will periodically shed their shells as they grow. This can happen as many as 25 times before they are 6-7 years old; then males shed every year and mature females every two years. When lobsters become very large molting is less frequent. After they shed, they have a paper thin shell, which can take up to two months to harden, and are called soft-shell, new-shell or shedders. The debate goes on as to which is most tasty, though the soft-shell are definitely easier to crack!
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Lobsters "smell" their food by using four small antennae on the front of their heads and tiny sensing hairs that cover their bodies. Their sense of smell is so fine that they can sniff out a single amino acid that tags their favorite food.
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The teeth of a lobster are in its stomach. The stomach is located a very short distance from the mouth, and the food is actually chewed in the stomach between three grinding surfaces that look like molar surfaces, called the "gastric mill".
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Yes this is called reflex amputation (autotomy). They can discard a limb, this can be a lifesaving phenomenon. Lobsters have the ability to regenerate some of their body parts, for example, the claws, walking legs, and antennae. The fact that lobsters are capable of limb loss and regeneration is indicative of a very primitive nervous system and their differential sensitivity to pain compared to humans or other types of animals (they can drop a claw, etc. and go off like nothing happened).
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That red "stuff" is the lobster roe or coral. It is the female lobster's unfertilized eggs. Lobster roe is often considered a gourmet delicacy.
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The tomalley is the lobster's liver and hepatopancreas. It is often thought to be a delicious treat; however many advise against eating the tomalley. According to the Advanced Seafood Handbook, "there are no known safety considerations when it comes to eating lobster meat". However, consumers are advised not to eat the tomalley, the light green substance found in the lobster's carapace. This is the liver and pancreas, which are thought to accumulate contaminants from the environment. Much like the liver of other animals, the lobster's tomalley is the natural filter to prevent contaminants, like dioxins, from entering the system. It is a reassuring indication of the lobster's natural defense system at work, keeping the lobster meat wholesome, nutritious and delicious.
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A lobster that has lost one claw or has any missing appendage is called a cull. One that has lost two claws is called a bullet, dummy or log. Lobsters can grow back new claws, legs, and antennae.