Suction disk performance of echeneid fishes

The anatomy of the suction disk of two species of echeneid fishes, Echeneis naucrates L., 1758 and E. neucratoides Zuiew, 1786, is described, and measurements of their suction performance on both smooth and textured surfaces are given. Disk muscles erect or depress the numerous paired laminae, or toothed plates, which bear two to four rows of posteriorly directed spinules. The erect laminae create a sub-ambient chamber, allowing these fishes to adhere to other fish and inanimate objects. Resting sub-ambient suction pressure differentials were recorded, as were the greatest sub-ambient pressure differentials as the fish were pulled posteriorly to simulate drag induced by a swimming host. The resting pressure differential averaged -0.5 kPa, with no significant difference between Plexiglas((R)) and shark skin surfaces. With a force applied to their caudal peduncle, the echeneids generated suction pressure differentials averaging -92.7 kPa within the disk cavity while attached to Plexiglas. On shark skin, the use of spinules increased friction and reduced the maximum sub-ambient suction pressure differential to -46.6 kPa; considerably more force (17.4 N) was required to dislodge the echeneids from the shark skin than from the smooth Plexiglas (11.2 N).