A research on the relationship between the cephalic segment length (Lc) and total body length (Lt), and between the number of articles in the antenna flagellum and the total body length was conducted in a population of the terrestrial amphipod Talitroides topitotum (Burt, 1934) from Serra do Mar, Guaratuba, Paraná. It aimed to help the inference of the body length by measuring only the cephalic segment, and to know the relative age of individuals by counting the number of articles in their antenna flagellum. A total of 975 amphipods were caught with Malaise nets; they were photographed, the article number of the flagellum of the right and left antennae 1 and 2 was counted and cephalic segment length and their total body length was taken. There was a linear correlation between cephalic segment length and total body length defined through the equation Lc = 0.0506Lt + 0.3297; r² = 0.9577. There was a significant difference in the article number between the right and left flagellum, for both pairs of antennae. The difference was at most four articles for the fist antenna pair and twelve articles for the second one. The highest number of these articles between right and left flagellum showed a linear correlation with the total body length classes and it was expressed by the equation a1 = 4.3463Lt0.4264 for the first pair of antenna, and a2 = 10.5700Lt0.3581 for the second pair. I was possible to infer the relative stage of development of T. topitotum by measuring the cephalic segment length. However, only the highest number of articles between right and left flagellum constitutes a reference parameter for the inference of individual relative age in this species.
Antenna articles; cephalic segment length; body length
