Lobster reproduction involves a sequence of biological events, from courtship to the complex development of their young. Their propagation in the ocean depths showcases unique adaptations. Understanding these stages provides insight into the life history of these crustaceans.
Mating Rituals
Lobster courtship begins with the female seeking out a dominant male, often attracted by his size and aggressive demeanor. She approaches his den, releasing pheromones from openings near her antennae to signal her readiness to mate and to calm him. This chemical communication is detected by the male’s antennules, potentially spanning distances up to seven times the lobster’s body length.
If the male accepts her invitation, he may beat his swimmerets to spread these pheromones throughout his den, and she may place her claws on his head as a sign of acceptance. The female then molts within the safety of the male’s burrow. The male protects her during this soft-shell period, which can last for several days to a couple of weeks, until her new shell begins to harden.
Reproductive Process
Mating occurs shortly after the female has molted. The male lobster turns the female onto her back, belly-to-belly, to transfer sperm. He uses specialized appendages called gonopods, which are modified swimmerets, to deposit sperm packets known as spermatophores into a seminal receptacle located between the female’s third pair of walking legs.
The female can store these sperm packets for extended periods, sometimes up to 15 months or even two years, until environmental conditions are favorable for egg extrusion. When she is ready to lay her eggs, she curls her tail to form a brood chamber. As the eggs are released from her ovaries, they pass over the stored sperm, where external fertilization occurs.
After fertilization, the female attaches the eggs to fine, feathery hairs (setae) on her swimmerets, located on the underside of her abdomen, using a glue-like substance. A female lobster carrying eggs is referred to as “berried,” a term derived from the berry-like appearance of the egg mass. The number of eggs can vary significantly with the female’s size, ranging from approximately 3,000 to over 100,000 eggs for larger individuals.
Hatching and Larval Development
The incubation period for the attached eggs can last from 9 to 12 months, during which the female cares for them by fanning them with her swimmerets to ensure oxygenation and cleanliness. The eggs change color as they develop, typically starting as dark green, then turning black, and eventually becoming reddish as the embryo consumes the yolk and becomes visible through the translucent outer layer.
When ready to hatch, the female lifts her tail into the water current and beats her pleopods. This action releases the tiny, spider-like first-stage larvae, known as naupliosoma or stage I larvae, into the water column. These microscopic larvae are planktonic, meaning they drift with ocean currents and are highly vulnerable to predation.
Over the next 3 to 10 weeks, the larvae undergo several molts, progressing through various larval stages (typically three to four stages for American lobsters, or up to 11 for some species like the red rock lobster). Each molt brings them closer to the adult form, with the development of swimmerets and a more recognizable lobster shape. After the final larval molt, the post-larval stage begins, where the young lobsters settle to the seafloor and seek shelter, transitioning from a free-swimming existence to a bottom-dwelling life.