Cancer Pagurus - Life Cycle

Life Cycle

Reproduction occurs in winter; the male captures the female and holds her under himself until she moults. Internal fertilisation takes place before the hardening of the new carapace, with the aid of two abdominal appendages (gonopods). After mating, the female retreats to a pit on the sea floor to lay her eggs. Between 250,000 and 3,000,000 fertilised eggs are held under the female's abdomen for up to eight months until they hatch.

The first developmental stage after hatching is a planktonic larva (1 mm) called the zoea that develops into a postlarva (megalopa), and finally a juvenile. The first juvenile stage is characterised by a well-developed abdomen, which will, in time, become reduced in size and folded under the sternum. Juveniles settle to the sea floor in the intertidal zone, where they stay until they reach a carapace width of 60–70 mm (2.4–2.8 in) and then migrate to deeper water. The growth rate in males slows from an increase in carapace width of 10 mm per year before it is eight years old, to 2 mm per year thereafter. Females grow at about half the rate of males, probably due to the energetic demands of egg laying. Sexual maturity is reached at a carapace width of 12.7 cm (5.0 in) in females, and 11 cm (4.3 in) in males. Longevity is typically 25–30 years, although exceptional individuals may live for up to 100 years.