SIZE AT ONSET OF MATURITY AND FECUNDITY VARIATIONS AMONG FIDDLER CRABS POPULATION (UCA THAYERI RATHBUN, 1900) FROM DEFFERENT SUBTROPICAL MANGROVES

NEGREIROS-FRANSOZO MARIA LUCIA; COLPO KARINE

MAÓ - MENORCA - ESPAÑA

Congreso; 36th European Marine Biology Symposium - a marine science odyssey into the 21st Century.; 2001

Some environmental features have been shown as Influencing mangrove crabs populations, mainly the ones that feed diirectly on vegetable material (e.g. Aratus pisonii). However, concerning their deposit feeding habits, the fiddler crabs could be affected by avalability of organic material in the sediment. The size at onset of maturity of U. thayeri estimated by means of relative growth technique and the species fecundity in six different mangrove areas were the goal of the present research. Crabs were captured monthly by two collectors during 15 minutes in each site, throughout a year period. Some ecological factors were monitored, being the organic matter content of the sediment considered the most important. All crabs were measured at maximum carapace width, abdominal width at the base of the 5th somite and chelar propodus length. Sex of each crab was determined according to abdominal morphology. Ovigerous condition was also checked. Fecundity for ovigerous crabs with eggs in initial embryonic development stage was determined by counting of sub-samples using a splitter sampler (Motoda). Fiddler crabs mature in a largest size In more productive mangroves with a highestorganic matter content. Additionally, the reproductive potential of the studied populations can be also dependent on environmental resources as the fecundity index was also higher in such sites. Based on the present results, it can be assumed that both reproductive aspects are a reflex of the species phenotypic plasticity.