Stramonita brasiliensis (Gastropoda: Muricidae) living as inquiline on the shell of Pugilina tupiniquim (Gastropoda: Melongenidae)

We report the first documented association of the gastropods Stramonita brasiliensis Claremont and D. G. Reid, 2011 and Pugilina tupiniquim Abbate and Simone, 2015 based on specimens found in the intertidal zone off the state of Maranhão, northeastern Brazil. In total, 206 specimens of P. tupiniquim were observed and 91 had S. brasiliensis species on the dorsal surface of the shell. Three to six specimens were often found on the shell, which serves as a hard substrate for the occupation of the muricid. An association was inferred due to the high frequency of associated pairs, including the presence of S. brasiliensis spawns. It is also likely that P. tupiniquim plays a role in transporting S. brasiliensis from sandy plains to areas with favorable substrates and/or food sources. None of the shells exhibited perforations or injuries caused by S. brasiliensis. Pugilina tupiniquim was observed feeding on dead fish, while no feeding behavior of S. brasiliensis was observed in the region. Based on the evidence presented herein, the relationship between these gastropods is considered as a case of commensalism, more specifically inquilinism.