Macrothrix marthae, a new species (Crustacea : Anomopoda : Macrothricidae), a highly specialized macrothricid from Mexico

Macrothrix marthae new species is described from a tropical epi-contental l agoon, near the gulf coast of Mexico. The structure of the second antenna r esembles some taxa related to the Macrothrix triserialis-group, but mostly to the South-American Macrothrix superaculeata (Smirnov, 1982). However, pa rthenogenetic females of M. marthae are characterized by both morphological differences and strong specialization for scraping in the thoracic limbs I -V. Some of these distinguishing characters are: internal distal lobe of tr unk limb I with three strongly pectinate setae, limbs II, III, and V with m odified setae bearing well-developed pectens. The postabdomen has small spi nes, with no lobe formation. The new species was found to be associated wit h water hyacinth roots, and the adaptations observed are thought to be used to scrape efficiently organic matter from these roots.