Caprella equilibra Say, 1818: 391 –392; McCain, 1968: 25, figs. 12, 13; McCain & Steinberg, 1970: 19; Cavedini, 1982: 500; Lazo-Wasem & Gable, 1987: 335–336, fig. 10; Krapp-Shickel, 1993: 782 –783, fig. 533; Díaz et al., 2005: 3 –4. fig. 4; Guerra-García & Ros, 2012: 76–78, fig. 2; Paz-Ríos et al., 2014: 2524 –2526, fig. 2; Sánchez-Moyano et al., 2015: 84 –89, figs. 3–5.
Caprella aequilibra Mayer, 1882: 45, pl. 1, fig. 7; pl. 2, figs. 1–11; pl. 4, figs. 20–25; pl. 5, figs. 16–18; Chevreux & Fage, 1925: 455, fig. 433
(See a detailed complete list of synonymies in McCain & Steinberg, 1970)
Remarks. No specimens of Caprella equilibra have been found or examined during the present study. Schellenberg (1928) recorded the species from Port Said (Mediterranean side at the entrance of the Canal). Recently, studies on the fouling community in the Suez Canal by Emara & Belal (2004) reported the presence of Caprella equilibra in Bitter Lake and Lake Timsah. Future studies are necessary to confirm if the species is also distributed along the Red Sea or if it is restricted to the Canal.
Distribution. Globally distributed: Mediterranean, Black Sea, Atlantic Ocean, Indian Ocean and Pacific Ocean (see McCain, 1968 and McCain & Steinberg, 1970 for details). Takeuchi & Sawamoto (1998) found C. equilibra as abundant in plankton samples. We have also observed for this species a great ability to disperse in the water column and colonize buoys and fouling structures. This could explain its wide distribution.