| Abstrak/Abstract |
In this communication, we describe the water-hopping kinematics of the dusky-gilled mudskipper
(Periophthalmus variabilis), and by doing so elucidate an entirely new form of fish locomotion that has yet to be
reported in the public domain. Water-hopping is defined herein as an ability to hop once, or in succession, on the
surface of water without full submergence and without a fin-guided glide. We find that taxiing on the water
surface is the predominating kinematic movement used for the execution of successful water-hops. We observe
that an initial concentric ripple forms as the mudskipper impacts the water, and that subsequent taxiing on the
water surface generates a sinusoid-like ripple pattern in the water prior to take off. Interestingly whilst airborne,
the pectoral fins of P. variabilis appear to remain stationary, only to be deployed upon contact with the water.
When landing back onto the surface of the water, P. variabilis makes the initial contact via its pelvic region,
occasionally extending its pectoral fins during its descent. The reasons for pectoral and pelvic fin extension are
unclear, however, there may be either aerodynamic or hydrodynamic benefits in its doing so. This motion
furthermore prepares the mudskipper for either, a follow-on water-hop, or a discontinuation of movement altogether, as the body of the mudskipper becomes aligned in a way conducive to either. P. variabilis will launch
and land using both, horizontal surfaces such as littorals, and inclined-to-vertical surfaces such as rocks and
trees. |
