Sustaining a thriving lobster fishery through science and community.


Lobster Biology

Table of Contents Introduction
What's in a name?
Body Plan
Physiological Processes
   Molting & Growth
   Nervous & Sensory Systems
   Muscular System & The Lobster's Tail
Life Cycle
Larvae & PostLarvae
The Lobster's Future


Two species of lobster belong to the genus Homarus, both of which are common and of extreme commercial importance - - Homarus americanus and Homarus gammarus (= vulgaris). Homarus americanus is commonly known as the American lobster, the Northern lobster, or the Maine Lobster. Homarus gammarus, or the European lobster, is found in the eastern Atlantic from northwestern Norway (Lofoten Islands) to the Azores and Morocco from the low tide mark to 150 meters, but is usually not found much deeper than fifty meters. It is also present in the northwestern regions of the Black Sea and in parts of the Mediterranean. (Figure from: Holthuis, L.B. (1991) Marine Lobsters of the World: An Annotated and Illustrated Catalogue of Species of Interest to Fisheries Known to Date. FAO Species Catalog, FAO Fisheries & Synopsis, No. 125, Vol. 13, Rome: 292 pps. Used with permission.)

The American lobster is the largest of the two and is found in the northwest Atlantic from Labrador to Cape Hatteras, North Carolina from the intertidal to 480 meters, but is most common from four to fifty meters. The great chelae of the American and European lobsters are asymmetrical with one being the large, crusher claw and the other being the small, cutter or seizer claw. (Figure from: Holthuis, L.B. (1991) Marine Lobsters of the World: An Annotated and Illustrated Catalogue of Species of Interest to Fisheries Known to Date. FAO Species Catalog, FAO Fisheries & Synopsis, No. 125, Vol. 13, FAO-UN, Rome: 292 pps. Used with permission.)

Life Cycle

New lobster life begins as thousands of fertilized, bead-sized, pine green eggs (about 1 mm in diameter) are pushed out of the oviducts through openings at the base of the female's third walking legs. The embryos travel along the underside of their mother's abdomen until they reach the long hairs on her swimmerets (= pleopods), where they attach and remain glued for the next nine to twelve months. Inside of the eggs, the embryos grow by shedding their inelastic shell or exoskeleton. Fully developed embryos hatch as pre-larvae that cling to their mother's pleopods. Prelarvae remain attached until the female releases them by fanning her swimmerets in rhythmic waves. On their way toward the surface waters, they molt into the first larval stage. (Figure from: Templeman, W. (1937) Egg-laying and hatching postures and habits of the American lobster (Homarus americanus). Journal of the Biological Board of Canada 3: 339-342.)

Lobsters have three distinct, planktonic larval stages, all of which are found at the water surface during daylight hours and bright moonlight. The term plankton comes from the Greek word planktos meaning "to drift" or "to wander". Larval lobsters are not particularly capable swimmers so their gross movements are largely controlled by the direction of wind and water currents, which happen to be onshore during periods of larval release. Metamorphosis from the larval to a postlarval stage occurs at the fourth molt. These postlarvae are strong swimmers and it is currently thought that they make excursions to the sea bottom, or benthos (from the Greek, meaning "depth of the sea"), sampling the substrate to find a suitable settlement site. From settlement onward, the lobster will remain a benthic creature.

Settling postlarvae find holes in rocks, dig tunnels in eel grass beds, burrow into peat reefs or find other dark shelters where they presumably remain hidden for the first year of their lives. As they grow larger, the juveniles are found outside of shelters more often and seem to explore and forage away from their burrows. Adolescent stages, large but not yet sexually mature, live lives similar to that of adults. Adulthood is reached after five to eight years, depending largely on the water temperature where they have grown up. Mating is apparently seasonal, but has never been witnessed in the wild. Laboratory observations reveal that adult males and females form a brief pair bond before mating. The female lobster molts in the shelter of the hard-shelled male, mates with him, and then remains with her mate for a few days while recovering from molting. The female moves out, lives on her own, and has a voracious appetite for two months or more, while her shell finishes hardening. She then extrudes and broods her fertilized eggs, and the cycle repeats itself.



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