It was puzzling why a barnacle that was adaptable to such a broad range of hosts, should avoid the sea turtle.

[2] C. patula has a conical shaped shell with smooth plates, with long cirri IV, V and VI.

In contrast, C. testudinaria has a flatter, less conical shape, the cirri IV, V and VI are short, and there are shallow oval depressions on the radii at the junctions of the plates.

[3] Applying a von Bertalanffy growth model to the population suggests that the maximum achievable size of C. testudinaria on loggerhead turtles in the wild is approximately 70 mm (2.8 in) in rostro-carinal length.

It has been shown that C. testudinaria can relocate on the turtle's shell,[5] usually towards the optimal position with maximum water flow and thus the greatest filter feeding opportunities.