paired biramous appendages (composed of a peduncle and two rami) on the three segments of the pleon. Each pair can be clasped together via small coupling hooks on the peduncles and used in amphipods for swimming (Barnard and Karaman, 1991). See figure

Five pairs of disk like covers on the underside of the abdomen. The 2 anterior pairs in Porcellio scaber contain primitive lungs (these appear as whitish patches)

the 5 pairs of flattened gills on the pleon segments. Each pleopod has 2 lobes, the inner (concealed in life) functions in water vapor absorption and nitrogenous excretion, the outer serves in respiration and may bear invaginated lungs. The first 2 pairs of pleopods are lengthened in males and serve in sperm transfer.