Lobster reproduction is a unique and intricate process. It combines internal sperm storage with external fertilization, a method distinct in the marine world.
Mating and Sperm Transfer
Mating occurs shortly after the female molts, when her shell is soft and pliable, making her less vulnerable. The male turns the female onto her back and uses specialized appendages, known as gonopods or the first pair of swimmerets, to transfer sperm.
Sperm is packaged into a spermatophore and deposited into the seminal receptacle, an internal pouch on the female’s underside located between her last two pairs of walking legs. The female can store this sperm for an extended period, ranging from several months to up to two years.
Egg Development and Release
The female lobster begins the internal development of her eggs. The number of eggs a female can carry varies significantly, typically between 3,000 and 75,000, though larger females may carry over 100,000.
When the eggs are fully developed, the female positions herself, often by turning onto her back and cupping her tail. The eggs emerge from her oviducts, located at the base of her third pair of walking legs. As they are released, they are held externally on specialized appendages called swimmerets, located on the underside of her tail.
The Fertilization Event
Fertilization of lobster eggs is an external process. As the eggs are extruded from the oviducts, they pass over the seminal receptacle, where the stored sperm is released. Sperm exits not through the main orifice, but through two grooves located posterior and lateral to it. These grooves allow spermatozoa to fertilize the eggs as they move past.
A sticky, glue-like substance is secreted simultaneously, adhering the newly fertilized eggs to the fine hairs on the female’s swimmerets. This adhesive attachment secures the eggs to the female, where they will remain for their incubation period.
Incubation and Hatching
The eggs are carried by the female on her swimmerets, a state known as “berried.” This incubation period typically lasts 9 to 12 months, varying with water temperature and other environmental factors. The female cares for her developing brood, using her swimmerets to fan the eggs, which provides aeration and helps to keep them clean from debris and microorganisms.
As the embryos inside the eggs develop, the eggs undergo a color change, often starting as dark green and gradually turning reddish-brown as hatching approaches. Hatching occurs over several nights, when the female shakes her tail and fans her swimmerets, releasing the larvae into the water column. These newly hatched larvae are planktonic, meaning they drift in the ocean currents as they begin their independent life stages.