Twenty-seven species belonging to five genera of the family Trapeziidae inhabit the Indian Ocean and the Red Sea. These are: Hexagonalia brucei, Quadrella boopsis, Q. coronata, Q. maculosa, Q. reticulata, Q. serenei, Tetralia cavimana, T. cinctipes, T. fulva, T. nigrolineata, T. rubridactyla, T. vanninii, Tetraloides heterodactyla, Tetraloides nigrifrons, Trapezia cymodoce, Tr. digitalis, Tr. ferruginea, Tr. flavopunctata, Tr. formosa, Tr. guttata, Tr. lutea, Tr. punctipes, Tr. richtersi, Tr. rufopunctata, Tr. septata, Tr. speciosa, Tr. tigrina. The taxonomic status of one of these species, Quadrella serenei Galil, 1986, is discussed and the species is redescribed. Q. serenei was initially referred to as Q. cyrenae Ward, 1942 but it its concluded that Ward used specimens of Q. maculosa Alcock, 1898 in its description; Q. lewinsohni Galil, 1986 is a subjective synonym of Q. serenei. Another species, Trapezia punctipes Castro, 1997, is a new record for the region.
Crustacea, Brachyura, Trapeziidae, Indian Ocean, Red Sea, symbiosis.