Like other brachyuran crabs, sex can be determined in A. pisonii by examining the abdomen. In females, it is broader and can be tightly flexed to hold the egg mass, called a sponge (eg. Ruppert et al. 2004). For A. pisonii, Warner (1967) found that females from 1.5 to 1.7 cm were the most common size class to breed. As with most decapod crustaceans, fertilization occurs during copulation shortly after the female molts. The male transfers sperm-filled cases, called spermatophores, to the female. After the eggs are fertilized, the female broods them on her abdomen until hatching. Although this species reproduces continuously, the peak of egg hatching may occur during the rainy season (Conde & Díaz 1989) or may be synchronized with lunar rhythm (Warner 1967, Warner 1977). At this time, the female climbs down from the tree into the water and rapidly vibrates her abdomen to release a cloud of larvae (Warner 1977). Each reproductive female may repeat this process up to six times annually (Warner 1967).Embryology / Larval Development:Depending on carapace width, each female may hold between 5,000 and 35,000 eggs (Conde & Díaz 1989, Warner 1977). After fertilization occurs, eggs hatch in approximately 16 days and begin the larval cycle in the water column (Warner 1977). Larvae pass through four zoeal stages and one megalopa, measuring between 0.6 and 0.9 mm (Cuesta et al. 2006), before settling to the benthos as juvenile crabs. Factors such as salinity, temperature and diet may affect growth and the duration of the larval period (Anger 2001). At 25°C and 34ppt, the entire settlement process spans about 20 days, and field observations have led to the estimation that newly hatched larvae can reach a juvenile size of 10mm in four to five months (Warner 1967).
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