[2] It is the rarest member of the remora family, though this may reflect more the uncommon collection of cetaceans in the wild rather than the whalesucker's actual abundance.

[3] The adhesive disk atop the head of the whalesucker is the largest amongst the remoras, bearing 25–28 lamellae and measuring 47–59% of the standard length.

[2] The whalesucker shares similar homologous structures to each living species of Echeneidae: each has a strong lower jaw, projecting forward and upward that becomes nearly horizontal to the surface of each remora's adhesion disk.

Chitinous material indicative of parasitic copepods or amphipods have been found in the stomachs of whalesuckers, suggesting a mutualistic relationship with their hosts.

[3] Off Fernando de Noronha, whalesuckers down to small (4 to 9 cm [1.6 to 3.5 in]) juveniles are associated with spinner dolphins, and are likely recruited year-round from flotsam.

Whalesuckers impose a hydrodynamic cost to their host, their adhesive disks can abrade the skin, and they sometimes attach to inconvenient locations, such as near the blowhole or the genitals.

[10] Recent studies of the Opithomyzonidae have found flaws in its perceived ancestry to the whalesucker due to its comparatively low six-to-eight-disc lamellae and lack of the adhesion disc's migration to the fish's skull.

What is speculated, is that the changes in the disc's length most likely occurred through performance-based natural selection through friction against surfaces of larger animals.

While the black salmon does not share the same feature of the adhesive disc as the whalesucker, both exhibited behaviors that enabled them to stay close to their host organisms for protection and resources.

[11] The whalesucker's true homologous origins may not be confirmed, its relationship to its phylogenetic relatives shows a similarity in both its morphology and behavior towards dolphins and blue whales.