First observations of the burrows of Anguilla japonica

Abstract

The burrow morphology of the Japanese eel Anguilla japonica was studied using in situ resincasting in a mud bottomed tidal drainage channel adjacent to the Fukui River in Tokushima, Japan. Two eels (62Á5 and 56Á3 cm total length) were initially fished from the burrows to verify that they were being used by A. japonica. Casts were made of 10 burrows that were found to have from one to three openings and main tunnels that were parallel to the axis of water flow in the channel. The maximum depths of the tunnels in the mud were 17Á8-30Á0 cm. The diameters of main tunnels ranged from 1Á2 to 7Á9 cm, were almost always wider than the bodies of the Japanese eels examined, and were more variable in the horizontal axis than in the vertical axis. There were no other animals capable of constructing a long and thin burrow in this channel, so these observations indicate that anguillids are able to construct their own burrows in soft mud sediments that may be used for extended periods of time. # 2005 The Fisheries Society of the British Isles

How American eels Anguilla rostrata construct and respire in burrows

“…Since the walls of a mud burrow are not rigid, it is possible for an eel to reverse its orientation without creating a permanent chamber. Orientation reversals may have been the cause of the large diameter of Japanese eel burrows reported by Aoyama et al (2005). Orientation reversals have also been recorded in other burrowing fish, e.g.…”

“…The burrows observed in the present study qualify as horizontal burrows, but in 3 of 15 cases, the shallow depth of aquarium mud may have constrained burrow depth. Horizontal burrows were also reported for the Japanese eel (Aoyama et al 2005). Although reversal of eel orientation within burrows was recorded in the lab and in the field, no enlarged interior chambers were found during burrow excavations.…”

“…In temperate regions, anguillid eels occupy the substrate throughout winter (Smith & Saunders 1955, Thomas 1968. Aoyama et al (2005) made resin casts of burrows excavated by Japanese eels Anguilla japonica (Temminck & Schlegel 1846) in a tidal channel, and found that burrows had up to 3 openings and ranged in depth from 18 to 30 cm. Wintering burrows of American eels may show a visible depression (pock mark) at the surface (Smith & Saunders 1955), but visible marks have not been reported for summer burrows.…”

The Design and Testing of RoboClam: A Machine Used to Investigate and Optimize Razor Clam-Inspired Burrowing Mechanisms for Engineering Applications

“…For the up/down motion of RoboClam, the energy lost to soil deformation during one stroke is (3) where the subscript u designates the up/down piston, ∆p u is the pressure difference over the piston, δ 1 and δ 2 are the starting and ending displacements of the stroke, A u is the area of the piston, F u,friction is the measured frictional force in the piston, and m u is the total mass moving up and down.…”

“…As many organisms have evolved to embed themselves into undersea substrates [1][2][3][4][5][6][7][8][9][10][11], our hypothesis is that nature has found an optimized solution to subsea burrowing. This paper describes the design and testing of RoboClam, a robot that mimics the kinematics of the Atlantic razor clam, Ensis directus, in order to probe the limits of Ensis-inspired burrowing.…”