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Research study 1

photograph of a northern abalone Haliotis kamtschatkana courtesy Ron Long, Simon Fraser University, Burnaby
Northern abalone Haliotis kamtschatkana appears to eye a duncecap limpet, but its eyes have no image-resolving capacity 0.6X

Abalones  crawl using rhyhmic muscular schematic showing locomotory waves in the foot of an abalonecontractions of the foot.  The contractions, called compression waves, begin at the back of the foot and move to the front (right to left in the drawing).  Usually, three separate waves are present on the foot sole as the abalone is crawling.  Because the waves move in the same direction as the animal is moving, the locomotory mode is termed direct.  The foot sole is actually divided into halves, with waves moving on both halves, but asynchronously.  The abalone’s locomotory mode is thus termed direct ditaxic.  When an individual is crawling slowly, most of the foot surface is in contact with the substratum and therefore tenacity, or attachment strength, is high.  However, at higher crawling speeds, such as during rapid escape from a predator, 3 things change.  First, wavelength increases (i.e., fewer waves traverse the foot); second, the frequency of waves increases; and third, a trough forms along the middle of the foot running from front to back.  Together, these changes produce a 50% decrease in area of the foot contacting the substratum.  Tenacity is greatly reduced and, at high speed, the abalone appears to fly along the substratum. Drawing from Miller 1974 J Exp Mar Biol Ecol 14: 99; Donovan & Carefoot 1997 J Exp Biol 200: 1145. Photograph courtesy Ron Long, Simon Fraser University, Burnaby.

NOTE lit. “double arrangement” G.

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Research study 2
Other vetigastropods that use direct ditaxic locomotion are top shells Calliostoma ligatum and C. annulatum. photograph of a snail Calliostoma ligatum feeding
Calliostoma ligatum feeding on the side of an aquarium tank 1.3X
photograph of a snail Calliosoma annulatum
Calliostoma annulatum crawling on a rock surface 1.3X

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Research study 3


drawing of a foot-sole of a snail that employs ditaxic locomotory waves drawing of foot soles of a snail to show retrograde locomotion

Limpets Lottia spp., turban shells Chlorostoma (Tegula) spp., and top shells Pomaulax (Astraea) gibberosa are all close relatives of abalones, but use a different mode of locomotion known as retrograde ditaxic.  The foot sole is split as before but, instead of running in the same direction as the snail is moving as in the direct mode, the waves run in the opposite or retrograde direction (see diagram on Right).  The waves commence at the front of the animal initiated with an hydraulic extension of the front part of the foot, proceed to the back, and are known as elongation waves.   Usually 3 waves are present on the foot at any given time, 2 on one side and one on the other.  Drawing on Right from Miller 1974 J Exp Mar Biol Ecol 14: 99; drawing on Left modified from Donovan & Carefoot 1997 J Exp Biol 200: 1145.

NOTE  of the 4 locomotory modes used by gastropods, retrograde ditaxic is by far the most common.  Two other modes, direct monotaxic and retrograde monotaxic, are used by other species and will be considered elsewhere in the ODYSSEY.   They differ from ditaxic modes in that the muscular waves traverse the entire width of the foot

NOTE  a snail’s foot is not solid muscle; rather, it contains spaces, or lacunae, into and out of which hemocoelic fluid is pumped for extension and contraction, respectively.  The foot musculature works around and on these fluid-filled spaces and this hydraulic action produces considerable flexibility and contortability in the foot

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Research study 4

photograph of a snail Calliostoma ligatum from below to show foot musculature

Which is the faster mode, retrograde ditaxic (Calli-ostoma, Chlorostoma) or direct ditaxic (Haltiotis)?  Well, speed depends upon absolute size of the snail but, with this factored out, the 2 modes are quite similar.  In fact, absolute speed is most closely correlated with foot area so, with its large foot, an abalone leaves most other competitors far behind. For most species studied escape speeds, initiated by contact with a predator, are about double normal crawling speeds.  Miller 1974 J Exp Mar Biol Ecol 14: 99; Data for Haliotis from Donovan & Carefoot 1997 J Exp Biol 200: 1145.

photograph of black turban snail Chlorostoma funebralis photograph of northern abalone Haliotis kamtschatkana
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Research study 5

graph showing cost of transport of a variety of gastropods in comparison with other flying, running, and swimming organisms

Data on cost of transport, that is, the energy required to move a unit of mass over a unit of distance, show that adhesive crawling (i.e., crawling on a mucous film) is more energetically costly than other forms of transport (adhesive crawling is represented by coloured dots on the graph).  However, studies at the Bamfield Marine Sciences Centre, British Columbia show that cost of transport in the northern abalone Haliotis kamtschatkana (light blue dot on graph) is almost an order of magnitude less than in other marine snails and in a terrestrial slug (shown by yellow dots). In fact, the cost for abalone ranks along with some small-sized terrestrial runners. The explanation for the greatly reduced cost in abalones may lie in the fact that even at moderate relative locomotory speeds, much less of the foot of an abalone is in contact with the substratum than in most other marine snails, thus reducing frictional resistance and amount of mucus required to be produced. Donovan & Carefoot 1997 J Exp Biol 200: 1145.

NOTE the marine snails featured in the graph are from the Mediterranean Sea; the slug is Ariolimax columbianus, a west-coast species

NOTE  a later determination of the contribution of anaerobic energy to crawling in H. kamtschatkana requires that the “cost of transport” be adjusted upwards as shown by the new symbol in the figure (dark blue dot). Donovan et al. 1999 J Exp Mar Biol Ecol 235: 273.

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Research study 6

graph showing seasonal activity patterns in northern abalone Haliotis kamtschatkanaA follow-up investigation to Research Study 5 at Shannon Point, Washington assesses energy budgets in northern abalone Haliotis kamtschatkana, with emphasis on cost of activity.  Direct observation of field activity by SCUBA in Barkley Sound, British Columbia shows that an average abalone on a summer’s day spends about 10h quiescent, 12h alert, <1h feeding, and 1.5h crawling.  Comparative values during winter are 16h per day quiescent, 5h alert, 2h feeding, and <1h crawling (see graph upper Right).  In summer (June-Oct) 20% of all field animals are observed crawling, as compared with less than 5% in winter (Dec-Feb).  

By measuring oxygen consumption in a respirometer during these different activity states the researchers determine that activity accounts for 23% of total consumed energy during summer and 13% during winter (see graph lower Right). Donovan & Carefoot 1998 J Shellf Res 17: 729.photograph of abalone Haliotis kamtschatkana crawling on a sea cucumberAbalone



crawls over a sea
graph showing energy expended by northern abalone Haliotis kamtschatkana during different activitiescucumber Parastichopus californicus 0.7X



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Research study 7


graph showing tenacity of attachment of black turban snails Chlorostoma funebralis

Large foot-size in snails is correlated not only with speed, but with tenacity.  Studies done on the black turban shell Chlorostoma (Tegula) funebralis at Friday Harbor Laboratories, Washington show that tenacity simulated photograph of a black turban-shell Chlorostoma funebralis supporting a rock in airincreases linearly with foot area, as predicted by scaling principles (see graph).  Miller 1974 J Exp Mar Biol Ecol 14: 99.

NOTE study at the Scripps Institution of Oceanography, La Jolla, California shows that foot adhesion or tenacity in  Chlorostoma funebralis can be great.  For example, a 4g live mass individual can support a 40-60g rock in air for several moments, and a much larger rock than this in water (see photo simulation on Right).  If an attached Chlorostoma is turned upside-down, it releases its hold on the rock.  Gabaldon 1982 Veliger 25: 153

NOTE  regression statistics for this line are Y = 128.9 + 2.7X, p < 0.01.  Tenacity, as measured here, is the force required to pull the snail vertically off a smooth plastic surface underwater


Not too convincing...?!


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