AbstractThe spider crab Maiopsis panamensis is the largest brachyuran crab in the Gulf of California and is found mainly in deep water. This study of the spider crab reproductive cycle in Mexican coastal waters used histological and chemical methods to describe oogenesis in detail and to define a scale of maturity based on visible characteristics for the different stages of gonial cells. The criteria used in the description of oogenesis were oocyte diameter, nucleus morphology, ooplasm characteristics, and degree of yolk accumulation, as well as lipid, protein, and carbohydrate content. These results showed that maturation and spawning are continuous in this species during most of the year, with small variations in the proportion of ovigerous females. The lowest frequency of mature females was found in spring (March to May) and summer (June to August). The organisms migrate to greater depths in the second half of the year. Maiopsis panamensis was found to have high reproductive potential because each female can produce multiple generations of oocytes in the ovaries while carrying the ovigerous mass. These characteristics mean that females spawn and hatch larvae numerous times throughout the year. Studies on the biology of this spider crab combined with study of techniques for catching them would allow informative strategies towards the sustainable use of this species in the Mexican Pacific Ocean and the Gulf of California.