Reproductive traits of the pagurid Sympagurus pictus (Smith, 1883) in the southern Gulf of Mexico

Abstract This study analyzes the population structure, reproductive biology, and bathymetric distribution of the pagurid crab Sympagurus pictus (Smith, 1883) in the southern Gulf of Mexico (18-26°N and 86-97°W) during 2009-2017. Specimens ( ) were collected with a shrimp trawl net in a depth range of 313-813 m. S. pictus distributed mainly at 400-699 m (temperature range of 5.7-13.8°C and salinity of 34.9-35.6 UPS) and occurred in higher abundances in summer. Morphometric analyses showed differences between sexes. The sex ratio favored females 1:1.43 and showed significant seasonal abundance variations. Minimum and mean size of sexual maturity were 8.5 and 11.7 mm of shield width (SW), respectively. Sympagurus pictus registered high fecundity (214-4630 eggs) and continuous reproduction with a peak in spring. Fecundity presented a significantly high variability and low correlation with size, but also significant. Compared to congeners, the species has larger eggs (0.37-0.45 mm 3 ). Unique adaptations include a flexible pseudoshell symbiosis with the anemone Paracalliactis obvolva , eliminating constraints on egg carriage and enabling isometric growth. This study extends the distribution of S. pictus in the Gulf of Mexico beyond 800 m depth and highlights its role as a dominant species in benthic ecosystems, driven by reproductive flexibility and symbiotic adaptations. Future research should explore larval development under in situ conditions and pseudoshell dynamics across life stages.