The Institute of Agrifood Research and Technology (IRTA), attached to the Department of Agriculture of the Catalan government, has launched a new research activity aimed at achieving the cultivation of the Mediterranean spider crab, a highly valued and therefore species over-exploited. This research will be carried out at the IRTA Sant Carles de la Ràpita centre, through the aquaculture crops Sub-programme, and several ways to improve survival in the last larval stage, a key moment to achieve commercial breeding, will be studied.

The spider crab or ‘Cranca’, Maja brachydactyla (Brachyura, Majidae), is an extremely important commercial crab in Spain, where its populations are over-exploited. The biological characteristics and first experiences in captivity indicate that this crustacean is a potentially viable species for commercial cultivation.

In its favour, the spider crab has the advantage of its high fertility, as it can lay between 20,000 and 200,000 eggs per laying and perform 3-4 layings per year. It is also characterized by a short embryonic development, an abbreviated larval development (three stages) and a relatively fast growth of juveniles.

Previous studies have been conducted in laboratory conditions at the IRTA facilities, and they showed that one of the challenges for the commercial breeding focuses on optimizing larvae cultivation. Specifically, the key is improving survival in the last larval stage (megalopae), a critical phase in which settlement and metamorphosis occur. Therefore, it is necessary to determine the optimal cultivation parameters, enabling survival improvements at the beginning of the post larval development.

Food plays a key role in achieving this, and, with the aim of obtaining a suitable artificial diet for this stage of development, a previous detailed study of the development of their digestive system and then the determining the level of feed intake are essential.

This project is to determine what may be the effect of temperature and photoperiod on larval development (duration, survival and biochemical composition in each stage) and the effect of the substrate and substances that favour metamorphosis.

One of the challenges IRTA scientists intend to solve is getting to fully understand the morphology and anatomy of the digestive system of the larvae (by means of histological and cytological studies), determining the changes that occur along this complicated development process. Finally, they will also study the ingestion level of artificial diets that could open the door to further studies on the nutritional requirements of larvae.

Understanding and improving the cultivation of larval spider crab will enable new ways for future projects focused both on the conservation of this species in the wild and its commercial use, providing thus a more possibilities to produce a new species and new entrepreneurship for aquaculture companies.