Clingfish Are Powerful Clingers in the Intertidal Zone, by Don Orth

Clingfish (Gobiesocidae) are the super suckers of the fish world! They spend their entire lives in the intertidal zones.  These nearshore waters have high, variable forces from crashing waves and strong water currents in marine intertidal environments. Clingfish are small (3-5 inches) and must hang on tight.  This family of fishes includes about 140 benthic fish species in 36 genera occurring in all major oceans and also in freshwater habitats. 

 Northern Clingfish Gobiesox maeandricus, Photo by Alison Young

Clingfish are so successful in the intertidal zone because they evolved modified pelvic fins to create a suction disc that acts as a morphological aid to resist the wave action.

Ventral sucking disc of the clingfish, showing epidermal papillae along disc margin.  Illustration by Green and Barber (1988)

But how does it cling so tight?  Super suction is made possible by the fusion of pelvic and pectoral fins to form special suction cup that can be flexed (Green and Barber 1988).  The suction disc also has a specialized epithelium, or microvilli.  Professor Adam Summers, University of Washington's Friday Harbor Laboratories, says these "thin hairs that are the same aspect ratio and length as the hairs on geckos’ feet or spiders’ toes or beetles’ feet.”   Papillae consist of tightly packed rods, which are divided into tiny filaments at the tips (Wainwright et al. 2013).  But these microvilli adhere underwater. When attaching to a surface, the fish rocks its pelvic girdle, forcing water out from under the disc and creating an area of sub-ambient pressure.  I call that “Suck Power!”

Clingfish adhering to a rock (a) is due to tiled papillae at the edge of the disc (b) and papillae are divided into fine filaments at the tips (c and d and zoomed-in SEM images).  (Wainwright et al. 2013). 

Clingfish do not simply hold fast in one location all the time. So the adhesive disc must work fast, be reversible and work on surfaces fouled by algae and encrusting organisms. This allows the clingfish to move in different ways.  Clingfish use a variety of feeding strategies to capture a diet of crustaceans and limpets.  Clingfish must also move to court, mate, and protect their offspring.  Pires and Gibran (2011) described how the clingfish moves by sliding the sucker disk across each stone, which is a slow form of movement.   The other movement type was “surfing” where the clingfish takes advantage of the ebbing tide and quickly moves a greater distance.  Clingfish are not good swimmers, so the ventral sucking disc is essential for moving around the intertidal zone.   Clingfish move over the entire shelter stone surface (see below for sequence of movements 1 through 8) and even rotate the body under the stone (b).  

Standard movements observed in a clingfish Gobiesox barbatulus (Pires and Gibran 2011).

Scientists devise ways of measuring everything.  Clingfish are capable of generating adhesive forces equal to 80 to 230 times their body weight, forces greater than engineered suction cups (Ditsche et al. 2013).  Watch the power of the suction disk to pick up 300 times its body mass. Why does anyone study clingfish sucking morphology?  It just might provide inspiration to the problem of creating a reversible approach to adhering to irregular, submerged surfaces.  So next time you are at the sea shore, turn over some rocks and observe these amazing little clingfishes.  

References

Ditsche, P., D.K. Wainwright, and A.P. Summers. 2014. Attachment to challenging substrates – fouling, roughness and limits of adhesion in the northern clingfish (Gobiesox maeandricus). The Journal of Experimental Biology 217:2548-2554  doi:10.1242/jeb.100149

Green, D.M., and D.L. Barber. 1988. The ventral adhesive disc of the clingfish, Gobiesox maeandricus: integumental structure and adhesive mechanisms.  Canadian Journal of Zoology 66:1610-1619.

Pires, T.H.S., and F.Z. Gibran. 2011.  Intertidal life: field observations on the clingfish Gobiesox barbatulus in southeastern Brazil.  Neotropical Ichthyology 9(1):233-240.

Wainwright, D.K., T. Kleinteich, A. Kleinteich, S.N. Gorb, and A.P. Summers. 2013. Stick tight: suction adhesion on irregular surfaces in the northern clingfish. Biology Letters 9: 20130234. http://dx.doi.org/10.1098/rsbl.2013.0234