European spider crab

Description

Maja squinado (the European spider crab, spiny spider crab or spinous spider crab) is a species of migratory crab found in the north-east Atlantic and the Mediterranean Sea. The look of the European spider crab is similar to the much larger Japanese spider crab. The young of M. squinado are slightly longer than 1mm after hatching, and weigh approximately 0.12 mg at this time. Within 4-8 days, the larva moults numerous times, finally ending with morphological changes that presumably include the further development and increase in size of the cephalothorax. In a second phase, the Carapace grows to a length of approx. 2mm, and weighs approx. 0.3 mg. The larva then undergoes metamorphosis to the first juvenile instar, and changes its planktonic life to a benthic one (living on the sea floor). Its appearance is also similar to that of the adult animal. From this stage only growth and the formation of sexual maturity follows. In observations under laboratory conditions, approx. 10.5% of the hatched zoea made it to this stage. The same conditions in terms of food, temperature and the like cannot be created in a laboratory. Animals in the first juvenile stage perform their first moult about 21 days after hatching, and therefore enter the second juvenile stage. Here there is a considerable increase in the length of the carapace to approx. 4.51 mm. The second moult marks the beginning of the third juvenile stage, the animal now has the appearance of the adult, with a carapace length of approx. 5.63 mm, but is not sexually mature. Juvenile animals spend another 2 years moulting and growing in size. The juvenile animals live in shallow water in winter, between rocks in coastal kelp forests. They spend the summer on small rocky reefs at a depth of only about 4 m. After this time, they reach a carapace length between 6-13 cm, with no noticeable sex-specific differences. During this time they are not yet sexually mature. There are two main periods for the critical moults that follow the approximately two-year period of growth leading to sexual maturity: the first, the prepubertal, in April, and the second, the pubertal, from July to October. However, in captive animals it has been noticed that in very large individuals that are in the phase before one of the two moults, one moult may be lost entirely, or be very late. Likewise, three moults have been observed on some individual specimens. The average time interval between the two critical moults is 104 days.