Locomotion
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Research study 1
 

photograph of a moon snail Euspira lewisii crawing on the top of the sand
Moon snails have 3 modes of locomotion.  When crawling on the sand surface they use either cilia or muscular foot contractions, and when burrowing they use muscular hydraulics.

NOTE when crawling on the surface using muscular contractions the mode of crawling is direct monotaxic. This means that contraction waves on the foot pass from posterior to anterior, in other words, in the direction of travel, and that the waves traverse the entire width of the foot.  Information of this and other locomotory modes in gastropods is found elsewhere in the ODYSSEY: LEARN ABOUT ABALONES & RELATIVES: LOCOMOTION



Moon snail
Euspira lewisii, recently emerged from the sand,
crawls past an anemone Pachycerianthus fimbriatus 0.33

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Research study 2
  photograph of a moon snail travelling through sand with the main body parts labelledphotograph of head-on view of a moon snail burowing in sand

Details of burrowing of the moon snail Euspira lewisi are provided in a study using specimens from Departure Bay, British Columbia.  The chief organ involved, the aquiferous system, is a large and expansible system of interconnected lacunae or sinuses that branch to fill the entire portions of foot and mesapodial/postpodial complex.  These lacunae communicate with the outside via many tiny slits (40┬Ám in size) along both sides of the postpodium.  The slits have associated muscles allowing them to be opened and closed.  During uptake of seawater the muscles relax and actually lengthen through swelling of sheaths that surround them and their combined action enlarges the aquiferous sinuses.  During expulsion of water the muscle sheaths detumesce, the muscles contract, and water is forced out of the aquiferous spaces.  The exudable fluid within the spaces makes up over 40% of the total mass of the expanded snail.  Burrowing within the sand is accomplished by first thrusting forward with the propodium.  The propodium then dilates, fills with water, pushes the substratum aside, and pulls the body and shell along. The author specifically notes that a terminal anchor, as employed by burrowing bivalves, is not involved. Bernard 1968 J Fish Res Bd Can 25 (3): 541.

NOTE  a propo of nothing in particular: if invasive surgery were found to be necessary when working on moon snails Euspira lewisii, then research findings at Bamfield, British Columbia on methods of anaethesia may be useful. The author tests a number of traditional and newer chemicals, some of which are effective, but notes that hypothermia (temperature reduced to 2oC over a 1-h period) seems to work as well as chemicals for routine uses such as surgery.  Bourne 1984 Veliger 26: 327.  

drawings of burrowing in moon snailsNOTE  other descriptions of burrowing in moon snails differ from that provided here.  Thus,in this description for a European species, the mesopodium is expanded and acts as a penetration anchor.  Simultaneously, the tip of the propodium is drawn into a wedge by contraction of muscles and is driven into the substratum by hydraulic forces.  The propodium is then expanded to form a terminal anchor and the shell is pulled down by muscle contraction.  The shell is mostly covered by the propodium, resulting in a streamlined shape to pass through the sand.  Trueman & Ansell 1969 Oceanogr Mar Biol Ann Rev 7: 315.

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photograph of a 3-D model of a snail to show how it burrows taken from a videa

CLICK HERE to see a video of the burrowing movements described in Research Study 2 above. Video courtesy Cindy Young, UBC.

NOTE video replays automatically

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Research study 3
 
photoraph of a moon snail Euspira lewisii travelling over a surf-generated sand waveLife in shallow sandy areas means exposure to waves and the liklihood of a soft, bulbous-shaped snail like Euspira lewisii being flipped over. The photos below show the sequence of righting from an upside-down position. Note that righting involves much the same sequence of movements as described for burrowing; in fact, the snail ends up with its propodium partially buried. The final flip to upright posture occurs quite quickly. In Photo 8 the moon snail is facing the camera, with one tentacle showing and siphon partially extended on the right. In its rolling around, the snail has picked up a piece of membranous green alga Ulva which is stuck on its front just below the lower edge of the mesopodium.
photograph 1 in a series showing righting movements of a moon snail Euspira lewisii on sand photograph 2 in a series showing righting movements of a moon snail Euspira lewisii on sand photograph 3 in a series showing righting movements of a moon snail Euspira lewisii on sand photograph 4 in a series showing righting movements of a moon snail Euspira lewisii on sand
photograph 5 in a series showing righting movements of a moon snail Euspira lewisii on sand photograph 6 in a series showing righting movements of a moon snail Euspira lewisii on sand photograph 7 in a series showing righting movements of a moon snail Euspira lewisii on sand photograph 8 in a series showing righting movements of a moon snail Euspira lewisii on sand
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CLICK HERE to see a video of a moon snail Euspira lewisii burying itself. The video starts with a snail placed in an aquarium tank upside-down, and the process is of burying is similar to that shown in Research Study 3 above. The video takes a while to play through, but is worth watching.

NOTE the video replays automatically. It is rather long and may take a few moments to download

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