Marine species have veliger larvae. Torsion in gastropods has the unfortunate result that wastes are expelled from the gut and nephridia near the gills. A variety of morphological and physiological adaptations have arisen to separate water used for respiration from water bearing waste products. Gastropods are by far the largest group of molluscs. Gastropod feeding habits are extremely varied, although most species make use of a radula in some aspect of their feeding behavior. Some graze, some browse, some feed on plankton, some are scavengers or detritivores, some are active carnivores.
Brusca, R. Sinauer Associates, Sunderland, MA. These are species with general aquatic distribution in perennial waters. These are species that inhabit quiet bays or ponds. These are intermittant pool or intermittant stream species. These are riverine species. These are marsh species. These are mud flat species. These are species that burrow in sand or mud in rivers or lakes. These are deep water lake species. These are non-native species, introduced from other regions.
Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
To cite this page: Myers, P. Burch Consecutive high-velocity regions of muscular contraction were separated by d -shaped, dark blue regions zero velocity with respect to the substrate , which correspond to the interwave regions of muscular relaxation. The velocity profile of the ventral surface was not symmetric across each pedal wave. As a wave approached it, the speed of the speckle gradually increased, reached a maximum value and then decreased rapidly to zero after the wave passed Fig.
The velocity of the foot along the wave was not symmetric and the period over which acceleration occurred was approximately twice that of deceleration. The acceleration from zero to maximum velocity 3.
The kinematics of the pedal waves, including changes in wavelength and wave frequency, in relation to the overall crawling speed was investigated. We observed complex patterns of pedal wave propagation along the foot of all of the gastropod species crawling at constant speeds. In the case of garden snails, loping waves appeared frequently in addition to the forward-propagating pedal waves note that the animals that exhibited this dual mode of locomotion are not considered here.
In garden slugs and banana slugs, wave propagation exhibited distinct variations along the ventral surface, characterized by a dependence of the wave speed and wavelength on the position along the animal's foot. Although there was some level of variability, the data clearly showed that in both species the propagation speed of pedal waves was not constant, as was reported by Crozier and Pilz Crozier and Pilz, The wavelength and speed increased steadily with the distance to their origin the tail of the animal and peaked near the head.
The variations in wave speed with respect to the animal's centroid along the foot were considerable and the maximal wave speeds were 2. The ratio between peak speed of the pedal waves and the velocity of the animal's centroid increased with the number of waves observed on the ventral foot of the animal.
Representative patterns of A forward displacement, B the corresponding velocity and C the acceleration of the foot of a banana slug during the passage of a pedal wave. The velocity profile indicated that the wave geometry was not symmetric, showing slow acceleration at the posterior half of the wave and a more abrupt deceleration at the anterior half. Most of the wave-propagation patterns we observed coincided with the average pattern shown in Fig.
However, we also observed other, less-frequent wave propagation patterns. The wave configurations observed in all our experiments can be classified into three groups: 1 acceleration of pedal waves described above Fig. Representative measurements from three individual garden slugs of comparable sizes exhibiting these three wave configurations are plotted in Fig.
From these trajectories, we calculated the wavelength of the pedal waves Fig. In the most commonly observed wave pattern Fig.
The wavelength then decayed rapidly back to its initial value as the wave approached the anterior end of the animal. This behavior was clearly observed in the animals shown in Figs 1 and 3. A similar pattern in wave speed was observed as the waves progressed along the foot, indicating that wave speed was modulated by the wavelength while the wave temporal frequency remained constant, as expected in steady motion. In the next, less-frequent pattern Fig. Upon appearing at the posterior end of the foot, each wave quickly accelerated to a certain speed and remained constant as it progressed forward.
As the wave approached the anterior end of the foot, it decelerated quickly to its original speed. The propagation speed of pedal waves in garden slugs and banana slugs varied substantially as the waves propagated along the animal. The wave speed at locations very near both ends of the animals could not be measured owing to difficulties in identifying the exact location of the waves when they were very close to the rim see Fig.
As a result, the measured normalized wave velocity shown in the figures Fig. Representative patterns of wave propagation in garden slugs. Three wave-progression patterns were identified: 1 acceleration of pedal waves A,D,G , 2 symmetric acceleration and deceleration B,E,H and 3 constant wave speed along the animal C,F,I. Each column represents data collected from an individual garden slug. Although three distinct wave propagation patterns were observed, constant wave acceleration along the animal Fig.
The statistical distribution of the wave-speed patterns in small garden slugs and banana slugs is shown in Fig. This figure contains data from 22 garden slugs and six banana slugs in 41 and 12 steady-speed crawling trials, respectively. No more than three trials from each animal were included in this analysis and the number of wave propagation patterns observed in multiple trials of an individual animal was normalized by the total number of trials conducted in that individual.
Vertical displacements of the foot were measured during the passage of muscular contractions and relaxations. The sign of such displacement can also be determined by joint examination of the displacement vs time curve Fig. Percentage distribution of the three wave propagation patterns shown in Fig. Data are from 22 garden slugs and six banana slugs in 41 and 12 steady-speed crawling trials, respectively. Substrate deformation caused by a moving gastropod reflected the regional variations in the ventral surface movement Fig.
During steady locomotion, the muscular foot of the animal pushed the substrate backwards in each of the interwave regions blue regions in Fig. By contrast, the animal pulled the substrate forwards beneath its tail and head yellow regions in Fig.
This deformation pattern was observed consistently in both garden slugs and snails Fig. Interestingly, the magnitude of substrate deformation was modulated by the distance between the pedal waves, reaching maximum levels beneath the stationary interwaves and minimum levels beneath the waves. Each pedal interwave produced backward-directed stresses along the direction of motion whereas forward-directed stresses were imposed on the substrate underneath the regions occupied by the rim, the pedal waves and the anterior and posterior ends of the animal Fig.
The spatial organization of longitudinal stresses on the ventral foot surface is depicted in Fig. By invoking Newton's third law, we expect that similar stresses were exerted along the opposite direction on the animal's foot. As a result, the foot surface experienced a forward push on the stationary interwaves and a backward drag on the forward-moving waves and rim.
Relative vertical displacement of the foot between the locations corresponding to the blue and red lines shown in Fig. Deformation generated by a moving garden snail on the surface of the substrate in the animal's direction of motion longitudinal. A Two-dimensional contour map of the longitudinal deformation as a function of the longitudinal x and transversal y spatial coordinates.
Red, the animal is deforming the gel towards the right of the panel underneath the head and tail; blue, the animal is deforming the gel towards the left of the panel under the interwaves.
B Longitudinal deformation along the centerline of the ventral foot u centerline as a function of x. In both panels, the origin of the coordinate system is located at the intersection between the centerline of the ventral foot and the head of the animal.
The black undulating pattern and the black horizontal line have been included to indicate the position of the waves and interwaves relative to the peaks and valleys of the deformation field.
The horizontal stresses perpendicular to the direction of motion formed a train of paired patterns of opposite signs Fig. These stress patterns appeared in the regions of the substrate underneath the interwaves, indicating that these areas were pushed inwards toward the centerline of the animal in addition to being pushed backwards along the direction of motion. Although the substrate deformation reached positive peaks beneath the head and tail of the animal, it always remained negative beneath the waves and interwaves.
This spatial organization is depicted in Fig. Overall, the horizontal stress distribution along the direction of motion Fig. The maximum stress magnitude beneath the interwaves was significantly higher than that in the wave and rim regions. The ratios between the maximum stress magnitudes beneath the interwave regions and the wave regions were 2. Spatial distribution of the propulsive stresses generated by two terrestrial gastropods while crawling on a gelatin substrate.
The data in the left column are from a garden slug and the data in the right column are from a garden snail. A,B Contour maps of substrate deformation in the animal's direction of motion. C,D Contour maps of horizontal stresses in the direction of motion. These stresses were normalized with the normal stresses caused by the animal's weight estimated to be spatially uniform and equal to the ratio of the animal weight to the area of the foot.
E,F Contour maps of horizontal stresses in the direction perpendicular to the motion. G,H Brightness images showing the ventral foot of each animal and the marker beads used to measure the propulsive stresses.
In both images, the animals were crawling from the left to the right. The net propulsive force generated by the pedal waves of an animal in steady-speed motion considered here was offset by the viscous shear forces of the rim and waves, which can be calculated by integrating the stress beneath the interwaves.
In spite of the complex stress patterns generated beneath the animal's ventral foot surface, the net forward force was found to balance the sum of the backward shear forces produced by the forward-moving waves and the rim. The calculated propulsive forces were normalized by the weight of the animal in order to compare the propulsive forces for animals of different weight.
For garden snails, there was a trend of increasing normalized propulsive force with increasing crawling speed Fig. For the garden slug, however, there was no clear correlation between normalized propulsive force and crawling speed, possibly owing to the limited spatial resolution of our stress measurements in this case.
Because the width-to-length ratio of a garden slug's foot is smaller than that of a garden snail, the fine-scale details of the slug's stress distributions could not be captured as precisely as the garden snail's, resulting in less accurate, resultant propulsive forces. The ventral surface of a locomoting terrestrial gastropod is characterized by a train of alternating pedal wave and interwave regions that propagates from tail to head. The interwaves are stationary with respect to the ground whereas the waves move faster than the animal.
The wave train is surrounded by a continuous rim that moves at the velocity of the animal Fig. Overall, the motion of the ventral surface observed in this study was in agreement with previous studies Crozier and Pilz, ; Denny, ; Jones, ; Lissmann, a ; Lissmann, b ; Parker, However, close examination of our high-resolution measurements revealed that the spatiotemporal organization of both pedal waves and interwaves is more complex than had been previously assumed.
The waves are not symmetric Fig. Previous studies considered that pedal waves are symmetric and that both their length and propagation velocity are constant. Consistent with the premise of constant pedal wave properties, Denny also assumed that there is no pressure build-up between consecutive waves Denny, It appears that recent mathematical models on the propulsion mechanics of adhesive crawlers have relied on most of these assumptions Chan et al.
Sketch of the spatial organization of the horizontal stresses exerted by terrestrial gastropods on a substrate. A Stresses in the direction of motion plan view. B Stresses in the direction normal to motion plan view. C Side view of the animal. V wave , speed of the pedal waves. Our measurements of the motion of speckles on the surface of the ventral foot revealed asymmetric displacement pulses during the passage of each wave. Furthermore, the waves themselves were found to deform and accelerate as they progressed from the posterior to the anterior end of small garden slugs and banana slugs.
Among the different wave-propagation patterns that were observed, steady wave acceleration lengthening of the wavelength followed by abrupt deceleration shortening of the wavelength was clearly predominant.
Our traction measurements clearly showed that the variable speed of the pedal waves modulated the magnitude of the stresses under each wave. The pedal wave asymmetry and acceleration we observed are two potential contributors to the locomotion of terrestrial gastropods that have not been considered previously and warrant exploration in future modeling efforts. In fact, the observation that steady wave acceleration was present in two species that differ widely in size, such as garden slugs and banana slugs, suggests that this pattern is mechanically relevant to the locomotion of the animal.
Two-dimensional substrate deformation and stresses generated by the ventral foot surface elucidated the mechanical role of the pedal waves in pedal force generation. A net forward force was generated beneath each stationary interwave, where the animal pressed its foot against the substrate and pulled it backwards Fig.
The sum of the propulsive forces generated under the interwaves was shown to balance the sliding friction caused by the forward-moving waves and the continued translation of the rim, head and tail of the animal. Abstract Research on the adhesive locomotion of terrestrial gastropods is gaining renewed interest as it provides a source of guidance for the design of soft biomimetic robots that can perform functions currently not achievable by conventional rigid vehicles.
Publication types Research Support, Non-U. Plant Methods By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate. Advanced search. Skip to main content Thank you for visiting nature. Abstract Gastropods move using a single appendage—the foot. Access through your institution.
Buy or subscribe. Rent or Buy article Get time limited or full article access on ReadCube. References 1 Jones, H. Google Scholar 2 Lissman, H. Google Scholar 3 Miller, S. Article Google Scholar 4 Denny, M. Google Scholar 6 Ferry, J. Google Scholar 7 Creeth, J. Google Scholar 9 Lissman, H.
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