MICROWEAR ANALYSIS OF CRAB CLAW FINGERS: A FUNCTIONAL
MORPHOLOGICAL APPROACH
A thesis submitted
to Kent State University in partial
fulfillment of the requirements for the
degree of Master of Science
by
Eric J. Sload
August, 2014 Thesis written by
Eric J. Sload
B.S., Appalachian State University, Boone, NC, 2012
M.S., Kent State University, 2014
Approved by
______, Rodney Feldmann, Advisor
______, Daniel Holm, Chair, Department of Geology
______, Janis Crowther, Dean, College of Arts and Sciences
ii TABLE OF CONTENTS
LIST OF FIGURES …………………………………………………………………...…iv
LIST OF TABLES………………………………………………………………………...v
ACKNOWLEDGEMENTS ……………………………………………………………...vi
SUMMARY ...…………………………………………………………………………….1
INTRODUCTION ………………………………………………………………………..3
METHODS ....…………………………………………………………………………….7
RESULTS ……………………………………………………………………………….18
DISCUSSION …………………………………………………………………………...26
CONCLUSIONS ………………………………………………………………………..35
REFERENCES…………………………………………………………………………..37
APPENDIX………………………………………………………………………………43
iii LIST OF FIGURES
Fig. 1. - SEM micrographs illustrating A) spalling, in the upper left near the denticle tip
and; B) total surface destruction of a denticle………………………………...... 12
Fig. 2. - Scatterplot of wear features counted versus time tumbled in sediment, classified by
claw face....………………………………………………………………….……….19
Fig. 3. - SEM micrographs of the denticle surface from the right movable finger of a crusher
claw of Menippe mercenaria; at 20x (B), 52x (C), and 100x (D)
magnification………………………………………………………………………....24
iv LIST OF TABLES
Table 1. Specimen properties for fossil claws ………..………………………………...... 16
Table 2. - Output generated by generalized linear model and chi squared test in
R……….....………………………………………………………………….……….19
Table 3. - Results for intraoperator error analysis completed for taphonomic
study…………………………………...... 21
Table 4. - Results for intraoperator error analysis completed for major and minor claw
study…………………………………………………………………………………..22
Table 5. - Significance values from Kruskal-Wallis test of modern claws between claw types
at 20x, 52x, and 100x magnification………………………………………………….23
Table 6. - Significance values from Kruskal-Wallis test between modern and fossil crusher
claws at 100x magnification…………………………………………………………..25
Table 7. - Number of microwear features through intermolt rank……………………………34
Table 8. - Raw data used for analysis of tumbled specimen in taphonomic study at low (~10x)
magnification………………………………………………………………………….43
Table 9. - Raw data used for analysis of tumbled specimen in taphonomic study at high (~20x)
magnification………………………………………………………………………….46
Table 10. - Raw data used in analysis of major and minor claws...…………………………..48
v ACKNOWLEDGEMENTS
I would first like to thank my advisor, Dr. Rodney Feldmann for his help and support with this research, especially in regards to acquiring the materials required for making molds and casts. I would also like to thank my committee member Dr. Jeremy
Green for his help and experience with microwear studies, for helping me with the statistical work, and teaching me the methodology of microwear.
Dr. David Waugh and Merida Keatts helped me learn to use the scanning electron microscope at Kent State, and helped when the instrument needed fixing or maintenance.
Without their aid, this research would not have been completed.
I would also like to thank Ashleigh Stepp for completing the very tedious task of image randomization before each microwear analysis was carried out. Also, I thank
Roger Portell at the Florida Museum of Natural History for providing the specimens used in this study.
Portions of this research were presented at the Geological Society of America annual meeting in 2013, for which travel support was granted by the Graduate Student
Senate at Kent State University, and GSA.
vi SUMMARY
Traditionally, microwear analyses have focused on scratches, pits, and other scars on the surface of the teeth of vertebrates. These methods have proven effective in reconstructing the diet of extinct and extant taxa. Such studies have been completed on a wide range of vertebrates, including conodonts, fish, non-avian dinosaurs, and mammals, exhibiting the versatility of microwear analysis. This study applies the methods used in dental microwear analyses to study the potential functional and taphonomic significance of wear patterns on the claws of the Florida stone crab, Menippe mercenaria (Say, 1818).
Molds are made of the inner and outer claw surfaces, as well as the denticles using a high resolution polyvinylsiloxane compound, and casts are poured using epoxy resin. The study area was standardized by selecting the center of each claw finger molded. This replication procedure is used extensively in dental microwear studies. Scanning electron microscopy (SEM) in conjunction with the semi-automated software Microware 4.02 is used to quantify wear marks seen on cuticle. Patterns in wear features are then determined and an attempt is made to relate them to functional morphology. Number of scratches, mean scratch length, and angular dispersion were the primary factors used to make interpretations. Some differences are important to note, such as the varying hardness of decapod cuticle, as well as its softness in relation to enamel and dentine.
Also, the function of claws is very different from the role teeth occupy in the life of
1 2 vertebrates. Decapod claws function to capture food, to manipulate food toward the mouthparts, and to defend against predators; claws do not masticate the food.
Taphonomic effects on wear marks were investigated by tumbling a modern Menippe claw in sediment for set time intervals. Tumbling results suggest that transport in sediment does not produce new wear features and may obliterate previously deposited features. An SEM investigation was initiated using modern crab claws and fossil specimens, in which wear patterns on crusher and pincer claw types were compared statistically. These data showed no significant difference between claw types, and may have been the result of sampling site or other biomechanical and behavioral factors. This study is, to the author’s knowledge, the first of its kind attempted on an invertebrate taxon.
INTRODUCTION
Dental microwear studies have focused on the microscopic scratches, pits, and other wear marks found on the teeth of vertebrates. These studies are very useful for completing paleoecologic reconstructions by allowing researchers to determine feeding niche within a particular trophic system. Such work has been carried out on a number of extinct and extant taxa within the vertebrate realm, including mammals, fish, non-avian dinosaurs, and conodonts (e.g. Purnell, 1995; Purnell et al., 2006; Williams et al., 2009;
Green et al., 2012).
The aim of this study was to evaluate the applicability of methods previously only used for vertebrates on the claws of crabs. Dental microwear methods were used to replicate and analyze the functional surfaces of the claws of the Florida stone crab,
Menippe mercenaria (Say, 1818). The claw surfaces were imaged using scanning electron microscopy (SEM) to find any microwear features. These features were statistically analyzed for significance between major and minor claw types to test for a difference in use of the two claw types present on Menippe mercenaria.
The ecological role of the crab claw has been the subject of much study. A crab’s claw is an appendage used for many purposes, all of which may be categorized into three groups; foraging, agonistic behavior, and behavior associated with mating (Lee and
3 4
Seed, 1992). It is these three behaviors which apply the greatest selection pressures during the evolution of crab claws (Lee, 1995).
Foraging style appears to have an effect on heterochely in crabs, with more predatory crabs typically having a larger, more robust right claw and a more gracile left claw (Abby-Kailo and Warner, 1989), while non-predatory crabs typically exhibit isochely (Lee, 1995). Lee (1995) also suggested that presence or absence of symmetry in prey items (e.g. bivalves and gastropods, respectively) may also have an influence on claw structure.
The selection pressures applied by agonistic behaviors are important when competition for habitat or food occurs. These pressures appear to favor larger chelipeds, as is evidenced by the increased use of the “meral spread” display, in which the crab extends the chelipeds laterally in a show of aggression (Smith et al. 1994 in Lee, 1995).
Sexual selection plays a strong role in the evolution of the crab claw. In crabs, as in many other arthropods, the claw is often used to attract mates, and is modified to do so, sometimes at the energetic expense of the crab (Lee, 1995). Some crabs take this use of the claw to the next level, using it solely for mating purposes, as in the male fiddler crab
(Uca, spp. Leach, 1814), the large claw is of no use for foraging (Lee, 1995). However, in most crabs a larger claw also adds the benefit of allowing the animal to capture larger prey, so the selective pressures do not always conflict (Lee, 1995). Evidence for the importance of the claw in sexual selection comes from the obvious difference in size between males and females of crabs, with the males possessing larger claws for use in mating displays (Lee, 1995). 5
The importance of phenotypic plasticity, or the ability for the morphology of an
organism to change in response to changing environmental factors, in claws was analyzed
and discussed by Palmer and Smith (1994). The authors manipulated the diet and claw
maneuverability of individuals of Cancer productus Randall, 1840, and found that claw
size changed significantly over consecutive molt cycles between crabs fed soft and hard
shelled prey. This ability to change the morphology of the claw has potentially
reverberating effects on cheliped evolution (Lee, 1995).
Lee (1995) asked the important question of the historical timing of cheliped
differentiation for predation relative to sexual dimorphism in crab claws. The question of which differentiation occurred first is an important, although unanswered one, largely due to the difficulty in sexing fossil crabs.
It is important to note that crabs do not eat with their claws, but rather use their
claws to manipulate food items toward the mouthparts, to burrow, and to defend
themselves, among other functions. Because of this, there is presumably a higher
possibility for non-feeding functions of the claws to influence microwear patterns.
Also, there are significant differences in the biomechanical and material
properties between crab claws and vertebrate dentition. Firstly, crab claws, even the
denticles and claw tips (Vickers Hardness Number of 252.8 ± 35.6) (Waugh et al., 2006) which are hardened relative to the rest of the cuticle, are softer than tooth enamel (327 to
397 Vickers Hardness Number) (Gutiérrez-Salazar and Reyes-Gasga, 2003). Also, crab
claws do not occlude as consistently along the entire claw length as most teeth do in the
jaw of vertebrates. There are also large differences in the direction and type of force 6 applied in claws and in jaws. A number of variables are discussed in relation to how they may affect the deposition of microwear features on crab claws. There are, however, some key similarities between crab claws and vertebrate jaws. They both process food items which may have grit included in them, and they both occlude using hardened, specialized elements of the skeleton.
Given the variety of functions inherent to the claws of crabs, it seems unlikely that any specific feeding habit or diet may be discerned from microwear from the claws.
However, given the wide array of feeding styles found in modern crabs, it may be possible to distinguish groups which acquire their food in very different ways. For example, it may be possible to distinguish a crab which feeds on bivalves from a crab which feeds by scraping algae off of rocks.
This study asks three principal questions to address the viability of microwear studies on crab claws:
1) Do the claws of modern Menippe mercenaria exhibit microwear features?
1a) Does microwear on fossil claws mimic that seen on modern claws?
2) Does microwear seen on fossil claws of Menippe represent use of the claw during
life or taphonomic effects?
3) Is there a difference between the microwear pattern on crusher and pincer claw
types?
The study conducted here focuses only on one species, Menippe mercenaria, and does not compare microwear patterns across taxa of crabs. This work is the first essential step necessary before moving on to larger interspecies analyses. METHODS
Sample preparation. -- In order to examine microwear on crab claws, readily
attainable specimens, Menippe mercenaria, were used. All claws used were from adults
which were harvested for human consumption from the Florida stone crab fishing
industry. Florida stone crabs are abundant and well-studied in the biological literature, and have well-known dietary habits.
Molds and casts were used to replicate the studied surfaces on crab claws. This was done to allow for reproducibility and to save the specimens from destructive sampling.
High quality molds were taken using President Microsystem regular body polyvinylsiloxane manufactured by Coltene Whaledent. This product has been shown to reproduce features down to a fraction of a micron (Galbany et al., 2004). This is a two part system which was mixed with an extrusion gun and applied to the claw surface using a wooden applicator stick, being careful not to contact the claw surface. The molding compound was then allowed to cure onto the claw surface for at least 5 minutes before removal. The first mold was discarded to ensure no dirt or debris was included in the final mold. The molding procedure was repeated in the same area. This final mold was allowed to cure and was removed from the specimen. Care was taken to avoid skin or any object contact with the replicated claw surface on the finished mold. After the mold
7 8
was successfully removed from the claw surface, it was surrounded by a containment
wall of lab putty. The putty used was Coltene Whaledent Lab Putty©, which is also a two
part mixture, consisting of a putty base and an activator. The putty and activator were
mixed by hand and used to build a retaining wall around the completed mold. The mold
was placed on a level plane inside this wall, and the wall was allowed to cure for at least
10 minutes.
Casts of the molded surfaces were poured using Buehler Epo-kwick© epoxy. This
is a two part epoxy, consisting of a resin base and a hardener. The epoxy was poured in a
5 to 1 resin to hardener ratio by weight into a small disposable cup and mixed gently for
at least 3 minutes to ensure thorough mixing of the two parts, which is important to
achieve a hard cast. The mixed epoxy was then gently poured into the mold, making sure
to avoid the creation of bubbles in the pour. The poured epoxy and mold were then
placed into a vacuum chamber and evacuated for 2 minutes, then allowed to slowly return
to ambient pressure. This step was repeated twice more for a total of three evacuations.
Any bubbles on the surface of the mold were removed before curing. The evacuated cast
was then allowed to cure for at least 48 hours in a desiccating chamber with drierite. This was done to reduce the amount of available water vapor in the air during curing, thus avoiding a phenomenon known as amine blush, in which water vapor reacts with amines in the epoxy to produce a greasy film on the exposed area of the curing cast, effectively rendering the cast unusable. After 48 hours, the cast was removed from the mold, again avoiding contact with the study surface. The cast was checked for surface bubbles, which if numerous may obscure the study surface from viewing under SEM. 9
Samples were prepared for viewing by SEM by first gently shaving the bottom of
the specimen (top of cast when being poured) with a blade to achieve a flat surface.
Epoxy dust was removed using compressed air. The specimen was then mounted to a
stub with a carbon tab. Colloidal silver liquid was used to adhere the specimen to the stub
and allow for electrical conduction in the SEM. The silver liquid was then allowed to dry
completely.
Samples were coated in gold by use of a gold sputter coater. Specimens were gold
coated for 90 seconds under a current of 18 milliamps. At this point, samples were ready
for viewing in SEM.
Sample Imaging. -- An Amray 1600t scanning electron microscope (SEM) was
used to image all specimens. SEM is frequently used for microwear applications (Rose,
1983; Galbany et al., 2004), as it allows for maximum visualization of topographic
features on a surface, and exceeds the magnification ability of light microscopes.
During each image capture, an attempt was made to standardize the anatomical
location on the specimen imaged. This was done by choosing a landmark on the specimen surface, and aligning the field of view with such a landmark. Due to the variation in claw size and shape, even between claws of the same functional use (e.g. crushers or pincers), applying a morphometric standard to center each image was not possible, because such a standardization procedure would have resulted in imaging grossly different areas of the claw. Landmarks differed between each specimen; for an
example, see figure 3. 10
Brightness and contrast are both measured as relative values on the corresponding gauges in the SEM. Because of this, it was not possible to standardize every image to the same absolute value of brightness or contrast. To counter this issue, the operator adjusted the brightness and contrast to be in balance, meaning both brightness and contrast gauges read an average of zero across subsequent beam scans. However, in some cases, usually due to charging creating very dark areas, the contrast and brightness readouts were not reliable, so the operator adjusted both to maximize topographical features visible on the specimen.
For the majority of this study, emission was saturated at 85 microamps under
20kV accelerating voltage, which produced the optimal signal to noise ratio. Due to slight differences in manufacturing of tungsten filaments, each has a different saturation level.
All studies were done at a constant spot size and under 20 kV accelerating voltage.
Magnifications for each study will be discussed in their following sections, but the same magnifications were used for each sample in a given study.
Image Processing. -- Images were captured using an Orion PCI image digitization card and software. Images were captured at 3536 by 2830 pixels from the SEM. These images are larger than the native resolution of the monitor used during microwear analysis, so they were downsampled to 1349 by 1080 to optimally fit the monitor.
Downsampling was performed using Adobe Photoshop’s bicubic sharper algorithm, with image proportions locked.
Microwear analysis. -- Microwear counting was done using Microware 4.0.2 software written by P. Ungar (Ungar 1995, 2001). In order to minimize intraoperator 11
error and bias, SEM images were randomized and files renamed by a third party. Wear
marks on claw surfaces were then counted without the operator’s knowing exactly which
specimen and/or location was being analyzed. Thus, all images were analyzed in a single
sitting under blind conditions, again to minimize error within each study. Microware
software requires the operator to click on the image with the mouse pointer to define
endpoints of the major and minor axes of each wear pit or scratch observed by the operator. Upon definition of the axis lengths, the software stores the parameters of each wear mark in memory for analysis. When counting on a single specimen is complete, a descriptive statistical output is produced, and then exported to Microsoft Excel for further analysis. After counting was complete, random image filenames were matched to their originals to complete the analysis. It is not until this point that the operator knows which sample is represented in each image.
Because of the relative softness of crab cuticle in comparison to enamel or even dentine of teeth, it became necessary to differentiate between scratches and other wear marks seen on the surface, such as spalling (the removal of a layer of surface material by scraping) and total surface destruction (see Fig. 1). Such features are not readily quantified using established microwear techniques, and were ignored for the purpose of these studies. 12
Fig. 1. – SEM micrographs illustrating A) spalling, in the upper left near the denticle tip and; B) total surface destruction of a denticle. Note the lack of readily definable scratches on B. 13
Taphonomic Study. -- The first step in establishing the ecological or functional
viability of microwear on fossil crabs was to test if marks seen on cuticle were caused by
possible transport in sediment before burial. To accomplish this, a single right claw of an
adult Menippe mercenaria was tumbled in sediment made of a mixture of quartz and
limestone clasts for time periods of 0 (control), 4, 16, and 64 minutes without being
disarticulated. After each time period passed, the claw was removed, thoroughly cleaned,
and molded and cast in epoxy. Both the dactyl and fixed finger were molded and cast,
and samples prepared and imaged under SEM. Each claw was cast and imaged on three
faces; inner face, outer face, and denticles, producing a total of 6 casts for each tumbling
time sampled. Because it is unknown which area may be affected the most by tumbling in sediment, the center of each cast was imaged at low magnifications to capture the maximum surface area. Each face was imaged twice, at about 10x and 20x magnification,
with the magnification kept constant for each face on subsequent tumbling time captures,
even though there may be slight differences in magnification across images from
different faces. This was done using the zoom feature on the SEM, which allows the user
to fine tune the magnification between the larger steps available through the main
magnification dial. The magnification values given on the SEM readout are a digital
interpretation of an analog state of electron beam scanning area. In other words, if a SEM
micrograph displays “x10”, the real value of magnification could be 10.1x, or 10.2x, and
so on. Whether the SEM simply truncates the true magnification value after whole
numbers or if it rounds is unknown. For this reason, micrographs capturing a nearly 14 identical field of view may display slightly different magnification values. This phenomenon becomes amplified when working under high magnifications.
After images were captured from cast specimens, the images were processed as discussed above using Adobe Photoshop. These images were then randomized and analyzed using Microware 4.0.2 under blind conditions. Gathered data was analyzed using the statistical software package R. A summary generalized linear model and a chi squared value of significance was calculated, which may be seen in the results section.
Analysis of major and minor claws. -- A typical specimen of Menippe mercenaria has a right claw adapted for crushing armored prey and a left claw adapted for cutting soft prey (Simonson and Steele, 1981). These are colloquially referred to as “crusher” and “pincer” claws. The crusher claw is referred to as the major claw and the pincer the minor claw, regardless of which side of the animal on which it is found (Simonson and
Steele, 1981).
The goal of analyzing major and minor claws is to test the statistical significance of any possible difference in microwear patterns seen on these claw types. To do this, the most proximal denticles were studied on eight right handed major dactyls, two left handed minor dactyls, and one left handed minor fixed finger. Major claws are much more abundant than minor claws, because major claws are preferentially harvested from stone crabs for human consumption. On the major claw fingers, the proximal denticle was studied, whereas on minor claw fingers an area equal to that studied on the major fingers was studied, at the same point along the proximal-distal axis of the finger. This was done because denticles on minor claws are much smaller and more numerous than on 15
major claws, and do not occur at the same points along the claw finger. Molds and casts
were gathered from these samples, and prepared for imaging with SEM.
The study area was imaged under SEM at 20x, 52x, and 100x magnification. Each
image was centered on the center of the inner face of the denticle, and all specimens were
rotated to have the face being studied orthogonal to the incoming electron beam. The
trace of the denticle-inner face intersection was aligned to the East-West direction in each
micrograph. Subsequent magnifications were captured without moving the specimen
stage. Images were then processed in Adobe Photoshop and wear marks quantified using
Microware 4.0.2.
Data was gathered and organized in Excel, then analysis was carried out using
SPSS. To test differences seen between crushers and pincers, Kruskal-Wallis tests were
performed for each test variable. Since the data residuals were not normally distributed or
homoscedastic, a non-parametric test was needed. These tests examine the difference in
distribution of microwear parameters across claw types, and calculate if those differences
are statistically significant.
Fossil analysis. -- In addition to modern claws, five fossil specimens of Menippe mercenaria from the Florida Museum of Natural History were analyzed for microwear.
These specimens were all of Pleistocene age, collected from marl beds. The localities and stratigraphic unit from which these fossils were recovered may be seen in Table 1. All of these localities are along coastal south-western Florida, in the area around and between
Tampa to Port Charlotte. The three specimens from Pinellas County were collected from the Fort Thompson Formation, and the others collected from spoil, presumed of marl. All 16 five specimens contained the moveable finger, with some still retaining the entire propodus and carpus.
Each specimen was sampled for molding and casting from the most proximal denticle or denticle group, similar to the analysis of the modern specimens. Three right claws and two left claws were used for analysis. Table 1 shows the finger properties for each sampled claw.
Table 1. - Specimen properties for fossil claws.
Name Finger Hand Type Locality Formation Age Sarasota Undocumented Plio- County, Pleistocene UF114935 Dactyl Right Crusher FL Charlotte Spoil, unkown Pleistocene UF51027 Dactyl Right Crusher County Pinellas Fort Thompson Late UF5892 Dactyl Left Pincer County Fm. Pleistocene Pinellas Fort Thompson Late UF5904 Dactyl Left Crusher County Fm. Pleistocene Pinellas Fort Thompson Late UF5907 Dactyl Right Crusher County Fm. Pleistocene
Each cast was prepared for SEM analysis and three micrographs were taken for each specimen, one each at 20x, 52x, and 100x magnification. This was done to make comparison with modern specimens possible. The micrographs were processed and counted for microwear using Microware 4.0.2 during the same session as the modern major and minor claws analysis. These data were then used for analysis in SPSS.
Intraoperator Error. -- For all microwear studies, it is important to assess how consistent the operator is when counting wear marks on a computer monitor. Because microwear data are relative, it is imperative that the operator test him/herself for error 17 within each study. This is accomplished by having the third party who randomizes the files for analysis duplicate several images in the output folder which is given to the operator. This is done without the operator knowing which image files have been duplicated. With a large enough sample size, it is very difficult or impossible to recognize a repeated image, given that the repeated image is far enough away from its twin in the order of analysis. After the operator has counted the microwear on all samples, the third party gives the operator the key with which to re-match the randomized files with their original names given during SEM imaging. The duplicated images were then analyzed pairwise to test for intraoperator error. Ideally, both images in a single pair would yield identical microwear data. A Wilcoxon signed ranks test was used to test the duplicated pairs for error, or statistically significant difference between duplicates. The Wilcoxon signed ranks test was designed for non-parametric analysis of paired datasets. This analysis was carried out for both microwear studies undertaken using SPSS. Data for intraoperator error may be found in the results chapter. RESULTS
In both microwear studies carried out here, mean scratch length, standard deviation of mean scratch length, mean orientation, standard deviation of mean orientation, angular dispersion (a measure of the orientation of scratches relative to one another), and number of features counted were the variables analyzed. Microware also
gathers data relating to the minor axis, or width, of features, but those data are not used
here, as the minor axis of each feature was too small to reliably measure.
Taphonomic Study. -- A generalized linear model was used to test if differences in
wear marks as a function of tumbling time were significant, employing the R statistical
package (downloadable at www.r-project.org), the results of which may be seen in Table
2. R allows the user to define the distribution used when running the calculation, which in
this case was Poisson, because number of features counted is a count vector. A chi
squared test was then performed with the results from the generalized linear model using
the residual deviance and degrees of freedom. A non-significant value of 0.0578 was
produced, which suggests no significant relationship between tumbling time and number
of wear marks counted.
18 19
Table 2. – Output generated by generalized linear model and chi squared test in R. Note the p value is above 0.05.
Residual deviance Degrees of freedom Chi squared result (p) 33.296 22 0.05782972
Number of features vs. tumbling time, by face 20
18
16
14
12 Dactyl Denticles Dactyl Inner Face 10 Dactyl Outer Face 8 F Denticles
Number of features (N) 6 F Inner Face F Outer Face 4
2
0 0 10 20 30 40 50 60 Tumbling time (minutes)
Fig. 2. – Scatterplot of wear features counted versus time tumbled in sediment, classified by claw face. F = Fixed finger.
20
A scatter plot was made (Fig. 2), which does not show a significant change in the
number of wear features counted through tumbling time. This suggests that with more
tumbling time, neither deposition nor removal of wear marks would occur. King et al.
(1999) found that with tumbling time, wear marks were obliterated from an enameled
tooth. This lack of change suggests that wear marks seen on crab claws are likely a result of the functional use of the claw and not from post-mortem sediment-cuticle interaction.
It is also possible that 64 minutes of tumbling was not enough time to deposit a
significant amount of wear on cuticle. This seems unlikely, however, due to the fact that
quartz is much harder than cuticle. Further evidence in favor of removal of, versus
deposition of, wear marks can be found on the claws themselves. It is evident that
through more use of the claws, the most used regions on each finger, typically on the
denticles and distal ends of the fingers, become very worn, causing any wear marks
previously deposited to be obliterated (see Figure 1). This likely occurs from the fingers contacting one another during denticle occlusion and from interaction with foreign materials during claw closing. This would cause claws sampled from later in the molt cycle to yield fewer wear marks, rather than more. This appears to be caused by the deposition of a very high number of wear marks over a long time, allowing the wear marks to begin overlapping each other, causing obliteration of any original features.
Intraoperator error was calculated for this portion of the study. A Wilcoxon signed ranks test was run to test for significant difference between replicate images within the study, a procedure similar to Purnell et al. (2006). Non-significant values were 21
found for each variable studied, meaning that intraoperator error did not contribute to
variance seen in the data in any meaningful way.
Table 3. – Results for intraoperator error analysis completed for taphonomic study.
Significance values below 0.05 denote significant intraoperator error between replicate
images.
Tested Pair
Major X Major SD Orient X Orient SD R N
Z -1.784 -0.255 -0.561 -1.376 -1.478 -0.333 2 tailed significance 0.074 0.799 0.575 0.169 0.139 0.739
Major and Minor Claw Analysis. -- The goal of analyzing major (crusher) and
minor (pincer) claws was to investigate any differences seen in wear patterns between
two claw types within the same species, Menippe mercenaria. Each microwear variable was tested between claw types within a single magnification (20x, 52x and 100x). To streamline data gathering, axial lengths were not measured in absolute units, thus microwear data could only be compared within micrographs of the same magnification.
This produced three compound tests, one for each magnification. The results of the
Kruskal-Wallis tests may be seen in Table 5. Images captured from SEM may be seen in
Figure 3. The Kruskal-Wallis test was used because it is non-parametric, and gives a more conservative interpretation of variance between non-normal populations (Strait,
1993), so is less likely to commit a type I error. For all variables, the only statistically 22
significant difference between major and minor claws was found in N (number of wear
marks counted), and OrientX (average wear mark orientation) at 20 times magnification.
All other values displayed no significant difference between major and minor claws.
Fossil Claw Analysis. -- Additional Kruskal-Wallis tests were used to compare the
fossil specimens to the modern claws. These tests demonstrated that the fossil crusher
claws showed no significant difference from modern crusher claws in all microwear
variables studied. In other words, fossil claws exhibit the same randomness in their
microwear data as modern claws. The results of this comparison may be seen in Table 6.
Intraoperator error was also calculated for this portion of the study. A Wilcoxon signed ranks test was run, resulting in non-significant values for all variables studied between replicate images.
Table 4. – Results for intraoperator error analysis completed for major and minor claw study. Significance values below 0.05 denote significant intraoperator error between replicate images.
Tested Pair
Major X Major SD Orient X Orient SD R N
Z -0.357 -0.968 -0.561 -0.051 -0.102 -0.307 2 tailed significance 0.721 0.333 0.575 0.959 0.919 0.759
23
Table 5. – Significance values from Kruskal-Wallis test of modern claws between claw types at 20x, 52x, and 100x magnification. Values below 0.05 denote significant difference between major and minor claws for that magnification and test variable.
Variable tested Magnification Major X Major SD Orient X Orient SD R N 20x 0.307 0.838 0.041 1.000 1.000 0.041 52x 0.838 0.683 0.153 0.540 0.540 0.303 100x 0.221 0.102 0.221 0.683 0.683 0.680
.
24
Fig. 3. – SEM micrographs of the denticle surface from the right dactyl of a crusher claw of Menippe mercenaria; at 20x (B), 52x (C), and 100x (D) magnification. A is reference image for same claw as in B, C, and D, with area studied in box. Arrows denote scratch used as a landmark.
25
Table 6. – Significance values from Kruskal-Wallis test between modern and fossil crusher claws at 100x magnification. Values below 0.05 denote significant difference between major and minor claws for that magnification and test variable.
Variable tested Magnification Major X Major SD Orient X Orient SD R N 100x 0.414 0.221 0.683 0.307 0.307 0.758
DISCUSSION
Several variables which affect the deposition of wear marks in cuticle surfaces
contribute to microwear on crab claws. Taphonomy, cuticle properties, biomechanics,
diet, and molting need to be taken into consideration before making interpretations from
any pattern seen in microwear.
Taphonomy. -- Taphonomic tests suggest that transport in sediment would have either negligible or destructive effects on the number of wear marks counted on the claws of the Florida stone crab, Menippe mercenaria. These results support the hypothesis that microwear on crab claws is deposited during life from some functional use of the claw.
This is not surprising, knowing that crab cuticle is much softer (Vickers Number of 252.8
± 35.6; Waugh et al., 2006) than quartz (Vickers Number of 713.8 – 790.3, Baker et al.,
1959 and Lawn, 1993; in Lucas, 2004) and many of the other minerals commonly found along shallow coastal waters. The fossils used here were collected from marl beds in southwestern Florida. The sediment used for tumbling simulates this lithology well, with a mixture of limestone and quartz clasts. Menippe is known to live in areas of varying substrate from hard rocky areas to soft muddy bottom, and may often shelter in biotic structures (Beck, 1997). Future researchers should be careful to note the lithology from which fossil crabs are recovered, as this has a potential to affect the taphonomic history of the fossil in regards to sediment-cuticle interaction. Also, grain size of substrate has
26 27
the potential to affect the width of wear marks, as larger grains would logically imprint
wider wear marks into cuticle. However, any signal related to grain size in microwear
could be potentially attenuated by the variance in force applied. For example, a small
grain could possibly leave behind just as wide an imprint as a larger grain, given more
force used applied with the smaller grain. The mixture of scratch widths easily visible in
this study could possibly be linked to sediment size of substrate, but those data are not
analyzed due to their difficulty to measure accurately. The fossils used here were in many
ways a “best case scenario” for taphonomic history, being found in relatively
uncompacted and mineralogically soft sedimentary rocks. It would be advisable to limit
microwear studies to fossils found in predominantly carbonate lithologies, rather than
purely detrital or volcaniclastic deposits, as these typically contain a higher fraction of
silica and would logically have more potential to obliterate microwear features. The
fossils used here were also all original cuticle, with no evidence for replacement or widespread chemical alteration during diagenesis. Replacement of cuticle might have an effect on preservation of microwear features, but additional study with preservation style is needed to determine the feasibility for microwear analysis on replaced fossils.
Petrographic analysis would be advisable for future studies to assess the possibility of reworking, especially when working with older fossils.
Additionally, hydrodynamics may be cited to assess the likelihood of deposition of wear marks on crab claws. Typically, shortly after death, the arthrodial membranes which hold the segments of the crab skeleton together disintegrate, and the skeletal pieces are dispersed in the current. Crab claws are known to be very resistant to taphonomic 28
effects, a characteristic which has been linked to the enhanced deposition of calcium in
those regions of the cuticle (Mutel et al., 2008). Most crab claws are roughly cylindrical
in cross section, being longer proximo-distally than wide dorso-ventrally. Thus, the most
stable hydrodynamic configuration for a crab claw to be transported across a sediment surface would be to roll along in a plane perpendicular to the proximal-distal plane. This direction of transport would likely produce an abundance of scratch marks oriented transverse to the long axis of the claw. The tumbling experiment did not produce this pattern, which suggests that the cuticle in claws may indeed be resistant to abrasion from sediment. However, the tumbling experiment was not set up so the claw tumbled in only one plane.
Cuticle properties. -- The exoskeleton of crabs is composed of cuticle, which is the principal material in the exoskeleton of all arthropods. The cuticle in crabs is composed of chitin, which is then structurally hardened with calcium ions (Chen at al.,
2008). Chitin is composed of fibers which stack together in a horizontal arrangement, which then further stack into a “twisted plywood” structure (Chen et al., 2008). Waugh et al. (2006) reported micro-indentation hardness test values from denticle and non-denticle regions the claws of Callinectes sapidus. The denticle portion of the claw yielded a
Vickers Hardness Number of 252.8 ± 35.6, while the non-denticle region yielded 64.0 ±
18.1. Medical research shows the hardness of the enamel layer in human teeth to be hardest on the occlusal surface, with a Vickers Hardness Number ranging between 327 and 397 (Gutiérrez-Salazar and Reyes-Gasga, 2003). Thus, denticle cuticle on crabs is softer than the enamel on teeth, but the difference is somewhat less than one might 29
predict from so weak a material as chitin. This hardness in the claws is most likely
derived from the deposition of amorphous calcium salts in place of organic matter in the
denticle regions (Waugh et al., 2006).
This difference in hardness needs to be taken into account when measuring and
interpreting microwear data. Although even the hardest cuticle on the denticles of crabs
falls short of enamel, microwear analyses are still possible. It has been shown that
statistically meaningful microwear may be preserved in tooth dentine of some mammals
(Green, 2009). Gutiérrez-Salazar and Reyes-Gasga (2003) reported maximum Vickers
Hardness Numbers of 55.5 to 57.5 for dentine in human teeth. Thus, it follows logically
that microwear has the potential to be preserved in the harder regions of crab cuticle.
Biomechanics. -- Like the jaw of a vertebrate, a crab claw occludes so that the denticles process prey items and any sediment or objects between the claw fingers. Crabs as a group have the ability to generate large forces when occluding their claws. Schenk
and Wainwright (2001) calculated the mechanical advantage of claws from six crab
species. Mechanical advantage describes the effective ratio of the forces input to the claw
by the adductor muscles to the forces exerted at the surfaces of the claw. Of these six species, three xanthid crabs were molluscivorous. Of these, Menippe mercenaria had the largest mechanical advantage of 0.428 ± 0.005. The next highest value came from
Panopeus herbstii, at 0.372 ± 0.006. This shows that individuals in the genus Menippe possess very strong claws, which affects the deposition of wear marks during occlusion.
This would likely affect the scratch width, with stronger claws making wider scratches upon abrasion. 30
In addition to claw strength, claw geometry must to be considered. Crab claws display an immense range of morphologies, from gracile to robust. Many species lack denticles completely on the claws, and the shape of denticles may affect the nature of microwear deposited on their surface. Vermeij (1977) showed that mechanical advantage at the proximal region of claw fingers may approach 1, and declines toward the distal end. This gives the wide molariform denticle at the base of the finger the greatest force with which to crush molluscan prey items. In the microwear study here, no significant difference was found in any parameter between the proximal regions of the major
(crusher, strong) and minor (pincer, cutter, fast) claws, except for number and mean orientation at low (20x) magnification. This could be in part due to similarity in mechanical advantage between crusher and pincer claws in the region of the claw fingers studied. The proximal regions of the claw have high mechanical advantages for both claw types (major and minor), so the forces applied here may be more similar than at the distal regions, where mechanical advantage differs. This gradation may cause claw tips, rather than proximal areas, to yield more differences between crusher and pincer microwear patterns. Brown et al. (1979) noted the similarity of proximal dentition between major and minor claws in Menippe, where both possess a large proximal molariform denticle.
Brown et al. (1979) also performed mechanical advantage experiments on the claws of
Menippe mercenaria. They calculated the type and magnitude of force generated at different regions along both major and minor claws. Their experiments yielded compressive forces at the proximal region of the claw as 132.09 Newtons for minor
(pincer, cutter, fast) and 131.41 Newtons for major (crusher, slow) claws. These values 31
seem consistent with the data gathered in this study, where no significant difference may
be seen between the proximal microwear on major and minor claws.
Another variable to note is type of force exerted during occlusion (Brown et al.,
1979). In some cases, as in the proximal regions studied in this work, the forces were
purely compressional, with opposing denticles occluding orthogonally to one other. In
other areas of the claw, notably the tips and distal denticles on minor claws, the forces
exerted are mostly shear, with denticles occluding at an angle to each other, to rip apart material between the fingers (Brown et al., 1979). This difference in claw force geometry will logically affect the amount of pressure which may be applied to the surface of occluding denticles, and therefore has the potential to change the nature of microwear deposited on such surfaces.
Diet. -- Because this is the first study of its kind, an extant species of crab with well-known dietary habits was selected. Menippe mercenaria has been studied extensively (e.g. Menzel and Nichy, 1958; Sinclair, 1977; Brown et al, 1979; among others), largely because of its economic importance as a major fishery in the American
South. Menippe claws are harvested from adult crabs, and the animal is returned to the
sea to regenerate new claws and allow for continued spawning (Simonson and Steele,
1981). This produces a large number of readily available Menippe claws to study.
Menippe has a well-known diet, consisting mostly of oysters, other clams, barnacles, and
other marine invertebrates (Menzel and Hopkins, 1955; Williams, 1984). However,
Menippe does not select exclusively hard shelled prey items, it preys on almost anything
it can catch with its claws. This differs from other species of crabs that feed almost 32 exclusively on one item, such as Mithraculus sculptus Lamarck, 1818; the emerald crab, feeding on algae (Coen, 1988). It should also be noted that Menippe has been observed burrowing in sediment or other, harder substrates for shelter (Whitten et al., 1950; Wass,
1955; Powell and Gunther, 1968; Costello et al., 1979 in Williams, 1984). This burrowing behavior is a potential source for microwear on claws, and also a possible factor which may be used in inter-species analyses. It may be that burrowing behavior contributed to high angular dispersion (low R values) of the microwear seen in this study, making the wear marks appear random.
Menippe mercenaria possess dimorphic claws, one strong claw and one fast claw.
Dimorphism in crab claws has been suggested to allow for more diverse prey selection
(Abby-Kailo and Warner, 1984). No research has been done to quantify the difference in prey selection between the strong and fast claws of Menippe. It seems possible from the biomechanical research done that Menippe may be able to break bivalve shells with either claw. Microwear studies in the future need to be done in the context of inter-claw and inter-species diet comparisons, preferably in an experimental setting. Without these data, interpretations of diet from microwear are difficult to make. However, these behaviors are consistent with the microwear found on the claws of Menippe. Because no significant difference was found between major and minor claws, except at low magnifications for two variables studied, it cannot be said from these data that Menippe uses its crusher claw for a significantly different purpose than the pincer claw. Another possibility is that the functional uses of the claws do not leave consistent microwear patterns. It seems unlikely that Menippe would align a bivalve in its claw in any precise orientation before crushing, 33 although research needs to be done to test this. If this is indeed the case, the resulting microwear pattern would not follow any discernable pattern, because of the large variation in shell shape, size, and ornamentation available for predation. In short,
Menippe uses its claws for various purposes and to feed on a spectrum of prey items; all characteristics which create a lack of differentiation in microwear pattern between major and minor claws.
Molting. -- Crabs, as well as all arthropods, molt during their life cycle. During molting, the animal sheds the exoskeleton and replaces it. In Menippe, the molting cycle repeats several times through ontogeny. Each time the animal molts, the claw is shed, with the internal musculature remaining. This process likely affects the microwear features seen on crab claws. In this work, modern crusher claws were arranged from newest (most recently molted) to oldest (least recently molted). This ordering likely does not reflect age of the crab to which the claw belonged, but rather a more abstract intermolt ranking. This ordering was done by visually estimating the amount of wear on the claws. Interestingly, the number of wear marks along this ordering follows a logical succession. It appears that the number of wear marks is initially low, increases to a maximum, then drops off as the claw surfaces become more abraded through use (Table
7). Studies concerning the turnover rate of dental microwear have been carried out on velvet monkeys, and have concluded that microwear on the teeth of vertebrates may be completely obliterated in a matter of 1 to 2 weeks, given an abrasive diet (Teaford and
Oyen, 1989). Without raising crabs in a laboratory setting, it was not possible to control for this apparent variation in wear amount between intermolt ranks. 34
Table 7. – Number of microwear features through intermolt rank.
Number of microwear features (N) Intermolt Rank 20x 52x 100x 1 19 16 19 2 18 25 12 3 33 70 9 4 43 47 26 5 12 29 37 6 8 11 25 7 8 14 11 8 2 16 18
It should be noted that the periodicity of molting may vary between taxa. This would create the need to standardize claw sampling to control for variation in number and pattern of microwear features. Another way around this inherent variability is to gather a large sample size in which the experimenter is able to show the full range of intermolt rank for each species studied. In other words, it would be best to avoid comparing recently molted claws to newly regenerated claws. In the fossil record, it may be reasonable to assume that molts, rather than carcasses, would represent a more standardized intermolt rank, being preferentially found at the end of a natural molt cycle; although research needs to be done to gather in-depth data describing the variation of microwear features through the molt cycle of crabs. CONCLUSIONS
From the data gathered, it is apparent that microwear features found on the claws of Menippe mercenaria were deposited during life and are likely not a result of taphonomic conditions. From the data gathered, no difference was seen between major and minor claw types, suggesting some randomness in the data. This lack of difference is either the result of a genuine lack of difference in functional use of major and minor claws, or by the proximal nature of the area sampled due to biomechanical similarities in major and minor claws at that location. Future researchers are advised to study four regions comparatively; the proximal and distal regions of both major and minor claws.
Microwear should then be compared statistically between claw type (i.e. major versus minor), and between region (i.e. proximal versus distal on the same claw type). This would permit quantification of intra-species variation in microwear. This is the vital step necessary before moving on to inter-species studies of crab claw microwear.
While this study was not able to identify specific correlations between function and microwear for multiple species, it has confirmed that microwear does exist on the claws of crabs and that cross-species analyses may be possible with the correct selection of samples and sample areas. Interspecies analyses of claw microwear have the potential to be very useful indicators of claw function, but researchers must be careful to examine differing claw morphologies, small differences in cuticle hardness, and size of crab claws
35 36 between taxa in order to accurately compare microwear patterns. These variables are all potentially overcome, given careful selection of species, and attention to sampling area.
This study represents the critical initial steps toward extending the versatility of microwear analysis to the invertebrate realm.The next step in decapod microwear research is an attempt at cross-species analysis. From this study, it would seem wise to select two distinctly different specialist feeders with highly adapted claw morphologies, such as deposit feeders and herbivorous crabs. The comparison between such species would most likely yield meaningful and significant results, and provide needed numerical microwear data for distinction between major claw morphologies.
This study is the first of its kind attempted on an invertebrate. The data gathered here are not conclusive in documenting the usefulness of studies on crab microwear as a whole, but are encouraging. It is evident that microwear is preserved on crab claws, is measurable using methods previously only applied to dentition of vertebrates, and may be useful for distinguishing between broad functional uses of the claw. REFERENCES
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APPENDIX
Tables of data used in microwear analyses. For all tables, “MajorX” is the average feature length along the major axis;
“MajorSD” is the standard deviation of feature length; “OrientX” is the average orientation, in degrees from 0 to 180,
of measured features; “OrientSD” is the standard deviation of orientations measured; “R” is the angular dispersion, or
degree of parallelism of features, where a value of 1 denotes completely parallel features, and 0 denotes completely
randomly oriented features; and N is the number of features counted. 43
Table 8. – Raw data used for analysis of tumbled specimen in taphonomic study at low (~10x) magnification. Cast
column denotes location on claw of casted surface, time is minutes of tumbling, and image file is the randomized image
name used in blind studies.
Cast Time ImageFile MajorX MajorSD OrientX OrientSD R N Dactyl 0 A14 21.39 15.747 117.31 43.961 0.308 10 Denticles Dactyl 4 A20 20.68 18.168 110.88 49.334 0.226 9 Denticles Dactyl 16 A46 13.63 8.219 153.04 25.279 0.677 8 Denticles
Dactyl 64 A58 15.09 6.359 179.54 29.657 0.585 6 Denticles Dactyl Inner 0 A3 23.23 11.223 106.04 30.979 0.557 5 Face Dactyl Inner 4 A16 21.98 11.542 148.5 47.697 0.25 12 Face Dactyl Inner 16 A24 26.69 13.176 91.61 44.812 0.294 6 Face Dactyl Inner 64 A47 15.74 10.879 147.59 36.64 0.441 10 Face Dactyl 0 A50 31.04 12.93 25.7 46.631 0.265 19 Outer Face Dactyl 4 A18 26.44 14.604 48.17 39.737 0.382 10 Outer Face Dactyl 16 A35 20.86 12.11 33.36 24.016 0.703 10 Outer Face Dactyl 64 A41 19.56 8.843 36.55 37.97 0.415 7 Outer Face IF Denticles 0 A28 16.31 9.459 165.89 56.349 0.144 13 IF Denticles 4 A38 19.39 10.248 135.57 35.411 0.465 7 IF Denticles 16 A36 17.08 10.488 55.67 57.044 0.137 14 IF Denticles 64 A60 16.66 7.004 144.7 46.631 0.265 7 IF Inner 0 A44 22.66 31.437 159.62 15.71 0.86 6 Face IF Inner 4 A25 28.91 14.636 136.8 43.004 0.324 5 Face IF Inner 16 A23 11.88 4.371 69.11 47.213 0.257 4 Face IF Inner 64 A21 19.75 11.841 144.01 35.559 0.462 7 Face 44
IF Outer 0 A45 19.37 6.368 58.97 44.122 0.305 13 Face IF Outer 4 A31 16.14 7.111 60.64 53.357 0.176 12 Face IF Outer 16 A30 14.82 6.034 60.53 48.881 0.233 17 Face IF Outer 64 A19 17.34 5.265 8.88 51.649 0.196 12 Face
45
Table 9. - Raw data used for analysis of tumbled specimen in taphonomic study at high (~20x) magnification.
Cast Time ImageFile MajorX MajorSD OrientX OrientSD R N
Dactyl 0 A5 23.04 20.668 31.41 61.642 0.098 16 Denticles Dactyl 4 A49 27.2 23.09 112.89 51.607 0.197 12 Denticles Dactyl 16 A29 19.4 6.416 163.89 14.905 0.873 7 Denticles Dactyl 64 A12 25.71 13.649 178.87 39.596 0.384 7 Denticles Dactyl Inner 0 A15 33.28 13.963 117.94 33.046 0.514 10 Face Dactyl Inner 4 A40 36.49 19.634 175 65.401 0.073 10 Face Dactyl Inner 16 A27 33.5 19.859 68.69 75.922 0.029 10 Face Dactyl Inner 64 A51 29.46 18.156 127.13 38.652 0.402 8 Face Dactyl 0 A4 40.63 27.342 35.18 56.216 0.145 12 Outer Face Dactyl 4 A9 56.84 39.325 135.3 49.045 0.23 5 Outer Face Dactyl 16 A2 42.85 9.992 19.56 41.652 0.347 3 Outer Face Dactyl 64 A1 30.14 7.254 40.61 11.37 0.924 5 Outer Face 46
IF Denticles 0 A11 25.29 16.886 51.25 46.306 0.27 15
IF Denticles 4 A48 21.01 9.642 133.7 67.936 0.06 9
IF Denticles 16 A55 25.37 24.528 80.53 68.334 0.058 17
IF Denticles 64 A7 27.34 12.599 78.87 44.639 0.297 3
IF Inner 0 A37 23.27 4.041 149.29 26.921 0.643 2 Face IF Inner 4 A8 31.24 11.575 143.97 35.969 0.454 7 Face IF Inner 16 A22 23.3 4.935 108.66 31.442 0.547 3 Face IF Inner 64 A33 35.65 22.563 123.9 34.489 0.484 5 Face IF Outer 0 A32 30.33 14.049 56.35 50.308 0.213 15 Face IF Outer 4 A10 20.63 10.581 77.71 35.668 0.46 12 Face IF Outer 16 A17 26.44 14.125 103.91 41.38 0.352 8 Face IF Outer 64 A39 34.85 21.231 145.52 52.465 0.186 9 Face
47
Table 10. – Raw data used in analysis of major and minor claws. Here, crusher is used for major and pincer for minor claw type. Table organized by age (modern or fossil), finger, hand, and claw type. Magnification denoted in “Name” field. “ImageFile” gives the random file name seen by the operator during blind analysis.
Age Finger Hand Type Name ImageF Major MajorS Orient OrientS R N ile X D X D Mode Movable Right Crush C1_Denticle_100 6 30.97 8.878 123.99 44.357 0.301 19 rn er x Mode Movable Right Crush C1_Denticle_100 188 33.7 23.912 118.73 47.225 0.256 16 rn er x_SP4 Mode Movable Right Crush C1_Denticle_20x 154 24.07 14.252 174.87 48.037 0.245 19 rn er _SP4 Mode Movable Right Crush C1_Denticle_52x 78 33.66 16.634 39.64 58.432 0.124 16 rn er _SP4 Mode Movable Right Crush C2_100x 91 40.04 16.724 135.34 36.684 0.44 18 rn er Mode Movable Right Crush C2_20x 25 22.99 9.585 151.52 26.726 0.647 12 rn er Mode Movable Right Crush C2_52x 173 33.89 20.828 143.77 28.973 0.599 25 rn er Mode Movable Right Crush C3_100x 180 54.89 42.566 157.64 32.619 0.522 33 rn er Mode Movable Right Crush C3_21x 93 32.2 15.927 156.34 27.838 0.623 9 rn er 48
Mode Movable Right Crush C3_52x 119 37.99 27.025 146.79 24.66 0.69 70 rn er Mode Movable Right Crush C4_1000x_loc2 13 93.54 62.266 137.51 13.769 0.89 10 rn er Mode Movable Right Crush C4_100x 74 55.21 34.126 155.17 27.572 0.629 35 rn er Mode Movable Right Crush C4_100x 158 54.63 42.196 155.07 32.595 0.523 43 rn er Mode Movable Right Crush C4_100x_loc2 38 60.61 49.826 147.47 22.162 0.741 32 rn er Mode Movable Right Crush C4_20x 57 34.72 24.944 137.55 30.912 0.558 26 rn er Mode Movable Right Crush C4_520x_loc2 135 136.36 85.518 149.73 21.132 0.761 13 rn er Mode Movable Right Crush C4_52x 86 50.19 39.342 162.74 33.041 0.514 47 rn er Mode Movable Right Crush C5_100x 45 72.5 44.035 0.49 25.284 0.677 11 rn er Mode Movable Right Crush C5_100x 63 71.89 45.989 3.89 25.231 0.678 12 rn er Mode Movable Right Crush C5_20x 64 25.25 13.297 148.94 25.024 0.682 37 rn er Mode Movable Right Crush C5_52x 121 58.32 32.939 159.55 27.735 0.625 29 rn er Mode Movable Right Crush C6_100x 9 57.71 37.536 149.55 38.13 0.412 8 rn er Mode Movable Right Crush C6_2_100x 136 72.12 36.92 171.23 30.997 0.556 11 rn er Mode Movable Right Crush C6_2_20x 40 24.14 12.355 157.72 67.757 0.06 26 rn er 49
Mode Movable Right Crush C6_2_20x 196 22.18 9.991 163.52 57.697 0.131 31 rn er Mode Movable Right Crush C6_52x 75 35.43 16.115 157.5 28.852 0.602 11 rn er Mode Movable Right Crush C7_100x 186 48.49 30.849 145.89 39.164 0.392 8 rn er Mode Movable Right Crush C7_20x 68 18.32 4.791 67.36 34.511 0.484 11 rn er Mode Movable Right Crush C7_52x 101 37.63 15.392 130.75 46.618 0.266 14 rn er Mode Movable Right Crush C7_52x 148 36.91 12.969 133.56 43.526 0.315 12 rn er Mode Movable Right Crush C8_100x 1 90.33 55.322 5.28 9.938 0.941 2 rn er Mode Movable Right Crush C8_20x 11 24.82 15.531 170.49 35.859 0.456 18 rn er Mode Movable Right Crush C8_52x 37 33.7 14.153 22.5 55.959 0.148 16 rn er Mode Movable Left Pince P1_100x 73 73.45 33.733 40.99 35.975 0.454 15 rn r Mode Movable Left Pince P1_100x 82 70.59 29.74 42.91 40.584 0.366 16 rn r Mode Movable Left Pince P1_100x_interden 142 31.11 13.484 75.74 31.117 0.554 16 rn r t Mode Movable Left Pince P1_200x_loc2 166 123.76 49.918 32.77 39.211 0.391 6 rn r Mode Movable Left Pince P1_200x_loc2 208 69.4 28.335 30.11 40.16 0.374 11 rn r Mode Movable Left Pince P1_20x 35 18.06 10.687 14.06 60.494 0.107 6 rn r 50
Mode Movable Left Pince P1_52x 161 38.68 15.314 34.39 49.984 0.218 21 rn r Mode Movable Left Pince P1_52x_interdent 232 21.9 11.675 140.5 51.858 0.194 13 rn r Mode Movable Left Pince P2_100x 242 22.76 5.992 117.69 29.299 0.592 8 rn r Mode Movable Left Pince P2_100x_loc_inte 7 35.49 23.241 81.87 31.681 0.542 34 rn r rdent Mode Movable Left Pince P2_100x_loc_inte 141 41.69 29.053 79.35 29.22 0.594 27 rn r rdent Mode Movable Left Pince P2_20x 2 17.98 10.758 82.28 16.704 0.843 10 rn r Mode Movable Left Pince P2_52x 115 34.61 18.028 78.34 28.681 0.605 10 rn r Mode Immova Left Pince P3_100x 14 30.25 21.396 106.44 23.711 0.709 17 rn ble r Mode Immova Left Pince P3_100x 164 39.42 15.833 104.58 34.119 0.492 13 rn ble r Mode Immova Left Pince P3_100x_interden 12 35.89 15.969 100.57 26.276 0.656 19 rn ble r t Mode Immova Left Pince P3_20x 19 33.66 20.264 107.59 32.665 0.522 10 rn ble r Mode Immova Left Pince P3_50x_interdent 169 32.06 16.316 107.95 32.425 0.526 25 rn ble r Mode Immova Left Pince P3_52x 100 36.08 21.639 108.09 27.611 0.628 16 rn ble r Fossil Movable Right Crush UF114935_100x 106 92.73 37.67 130.53 40.752 0.363 5 er Fossil Movable Right Crush UF114935_20x 3 25.46 5.229 135.82 28.552 0.608 3 er 51
Fossil Movable Right Crush UF114935_52x 8 42.92 20.829 159.67 54.564 0.163 10 er Fossil Movable Right Crush UF114935_52x 133 56.03 16.556 141.66 31.978 0.536 5 er Fossil Movable Right Crush UF51027_100x 194 27.32 10.325 143.79 26.016 0.662 12 er Fossil Movable Right Crush UF51027_20x 10 20.1 15.877 151.54 30.444 0.568 12 er Fossil Movable Right Crush UF51027_52x 17 26.52 14.386 161.52 38.392 0.407 24 er Fossil Movable Left Pince UF5892_100x 193 47.66 16.309 96.65 48.234 0.242 6 r Fossil Movable Left Pince UF5892_20x 66 26.61 11.224 147.92 42.994 0.324 15 r Fossil Movable Left Pince UF5892_52x 168 38.7 14.099 163.6 52.405 0.187 13 r Fossil Movable Left Pince UF5892_52xinter 110 51.03 19.024 146.07 36.069 0.452 11 r dent Fossil Movable Left Crush UF5904_100x 156 19.27 12.038 149.22 50.166 0.215 19 er Fossil Movable Left Crush UF5904_100x 189 17.15 9.891 156.8 50.302 0.214 21 er Fossil Movable Left Crush UF5904_20x 112 6.59 2.338 40.85 23.42 0.715 7 er Fossil Movable Left Crush UF5904_52x 59 15.89 6.626 157.43 47.809 0.248 12 er Fossil Movable Right Crush UF5907_100x 31 NA NA NA NA NA N er A Fossil Movable Right Crush UF5907_20x 155 NA NA NA NA NA N er A 52
Fossil Movable Right Crush UF5907_52x 159 NA NA NA NA NA N er A
53