“…However, we still have a limited understanding of what drives unionid movement behaviour (Haag, 2012). While movements in response to light cues have been recorded in a number of marine and freshwater bivalve speciessuch as in king scallops, Pecten maximus, zebra mussels, Dreissena polymorpha, and golden mussels, Limnoperna fortuneand encompass both positive and negative phototactic responses (Enever et al, 2022;Toomey et al, 2002;Uryu et al, 1996), the role of light as a potential stimulus of unionid locomotion is largely unresolved. Yet, light availability and intensity have been shown to affect non-locomotion unionid behaviours such as valve closure (Braun and Job, 1965;McIvor, 2004) and to trigger changes in feeding rates (Hills et al, 2020).…”