Population Biology and Larvae of the Anchialine Crab Munidopsis polymorpha (Galatheidae) from Lanzarote (Canary Islands)

The galatheid Munidopsis polymorpha Koelbel, 1892, is found at high population density in an anchialine pool (Jameos del Agua) on Lanzarote. Ovigerous females on an average carry 1-4 eggs. Larval development is advanced. Only 2 zoeal stages, which are unable to undergo locomotion, precede molt to a small crab. Munidopsis polymorpha is not preyed upon in the Jameos del Agua. Population density is regulated less by available food than by the number of available hiding places for resting phases. Population density is probably increased by the fact that the highly territorial crabs periodically alternate in feeding in the same grazing areas and in hiding. The percentage of ovigerous females and the average number of eggs per female is negatively correlated with the number of specimens per area. During the years of investigation from 1976-1989, the number of ovigerous females and the average number of eggs per female have decreased considerably in parts of the pool. Consequently, the general population density has become drastically reduced. This is attributed to the construction and opening of the Jameos del Agua for tourism.