Abstract
Attachment in the lumpsucker is initiated by the contraction of a horizontal pair of red muscles (I) running between the sucker skeleton and the hyoid arch. The force that they generate is translated through. nearly 90° by an arrangement of skeletal elements, ligaments and tendons, thus creating a negative pressure (c. 1 kPa) beneath the sucker. Sectioning of muscle pair (I) abolishes the ability to attach to the substratum. Further muscle pairs (II-X) are made up of white muscles which variously spread or unpeel the sucker. Muscular unpeeling is antagonized by elasticity of the cartilagenous sucker skeleton. Vertical forces of 98.3-101.6 kN m-2 sucker area were required to dislodge suckers. This implies a mean suction efficiency of 95.8 %. This high value suggests that adhesive mucus may contribute to attachment. On a polypropylene surface suckers sustained lateral forces of c. 5 N before sliding. Sub sucker (= interval) pressures reached high levels on attachment, but decayed in c. 10 s to levels which were then sustained for < 60 min. Ventilatory movements caused regular fluctuations in interval pressure. Lumpsuckers are capable of moving along the substratum without total detachment of the sucker. ‘Movements on the sucker’ (duration < 2 s) were accomplished by brief unpeeling of one laterofrontal portion of the sucker accompanied by single beats of one or both pectoral fins. Mature male lumpsuckers have significantly larger suckers than females of equivalent weight.