Evolution of sideways locomotion in crabs
- Graduate School of Integrated Science and Technology, Nagasaki University, Japan
- National Kaohsiung University of Science and Technology, Taiwan
- Susami Crustacean Aquarium, Japan
- Department of Entomology and Plant Pathology, Auburn University, United States
- Kitakyushu Museum of Natural History and Human History, Japan
Figures
Figure 1 with 2 supplements
Distribution of Forward–Sideways Index (FSI) values among crab species exhibiting forward and sideways locomotion.
Gold bars represent species classified as forward movers, and blue bars represent species classified as sideways movers.
-
Figure 1—source data 1
Species-level Forward–Sideways Index (FSI) values and selected reference-circle radii for the 50 species analyzed.
- https://cdn.elifesciences.org/articles/110015/elife-110015-fig1-data1-v1.xlsx
Figure 1—figure supplement 1
Gaussian mixture fit to dominant peak locations.
Dominant peak locations were extracted from mixture models fitted to each taxon’s continuous angle distribution. A two-component Gaussian mixture model fitted to these locations yielded an estimated cutoff at 49.4° (dotted line). Classifying taxa using this data-informed cutoff produced an identical forward/sideways classification to our original approach using Forward–Sideways Index (15 forward, 35 sideways).
-
Figure 1—figure supplement 1—source data 1
Gaussian mixture-model results for continuous bout-angle distributions of the 50 species, including model selection, peak locations, and component weights.
- https://cdn.elifesciences.org/articles/110015/elife-110015-fig1-figsupp1-data1-v1.xlsx
Figure 1—figure supplement 2
Morphospace of crab locomotor modes based on relative carapace length (CL/CW) and relative carapace depth (CD/CS).
Forward- and sideways-moving taxa overlapped broadly in morphospace, although phylogenetically informed ANOVA detected a significant difference in CL/CW but not in CD/CS. CL, carapace length; CW, carapace width; CD, carapace depth; CS, carapace size, defined as the geometric mean of CL, CW, and CD. 1. Arcania heptacantha; 2. Arcotheres sinensis; 3. Atergatis floridus; 4. Austruca lactea; 5. Calappa philargius; 6. Cardisoma carnifex; 7. Carpilius convexus; 8. Chaceon granulatus; 9. Charybdis (Charybdis) japonica; 10. Chionoecetes opilio; 11. Coenobita purpureus; 12. Cyclograpsus intermedius; 13. Dorippe sinica; 14. Dotilla wichmanni; 15. Enoplolambrus validus; 16. Epixanthus frontalis; 17. Erimacrus isenbeckii; 18. Eriocheir japonica; 19. Eriphia ferox; 20. Gaetice depressus; 21. Gecarcoidea lalandii; 22. Geothelphusa dehaani; 23. Grapsus albolineatus; 24. Hemigrapsus sanguineus; 25. Hyas alutaceus; 26. Lauridromia dehaani; 27. Lybia tessellate; 28. Lydia annulipes; 29. Macrophthalmus (Mareotis) japonicus; 30. Matuta victor; 31. Mictyris brevidactylus; 32. Mursia armata; 33. Neohymenicus orientalis; 34. Ocypode stimpsoni; 35. Oregonia gracilis; 36. Parasesarma pictum; 37. Paromola japonica; 38. Percnon planissimum; 39. Pilodius areolatus; 40. Pilumnus vespertilio; 41. Plagusia squamosa; 42. Portunus pelagicus; 43. Ranina ranina; 44. Sayamia germaini; 45. Schizophrys aspera; 46. Scopimera globosa; 47. Scylla serrata; 48. Thalamita sima; 49. Tiarinia cornigera; 50. Xenograpsus testudinatus.
Figure 2 with 3 supplements
Representative circular histograms of movement directions in crabs.
(a) Forward movement in Ranina ranina (FSI = 0.89). (b) Sideways movement in Geothelphusa dehaani (FSI = –0.70). The 0°–180° axis denotes the crab’s body axis before movement, with bars indicating the frequency of movement direction.
-
Figure 2—source data 1
Tracking coordinates of the anterior and posterior carapace landmarks of Ranina ranina used to generate the circular histogram in Figure 2a.
- https://cdn.elifesciences.org/articles/110015/elife-110015-fig2-data1-v1.zip
-
Figure 2—source data 2
Tracking coordinates from the first recording segment of Geothelphusa dehaani used to generate the circular histogram in Figure 2b.
- https://cdn.elifesciences.org/articles/110015/elife-110015-fig2-data2-v1.zip
-
Figure 2—source data 3
Tracking coordinates from the second recording segment of Geothelphusa dehaani used to generate the circular histogram in Figure 2b.
- https://cdn.elifesciences.org/articles/110015/elife-110015-fig2-data3-v1.zip
-
Figure 2—source data 4
Tracking coordinates from the third recording segment of Geothelphusa dehaani used to generate the circular histogram in Figure 2b.
- https://cdn.elifesciences.org/articles/110015/elife-110015-fig2-data4-v1.zip
-
Figure 2—source data 5
Tracking coordinates from the fourth recording segment of Geothelphusa dehaani used to generate the circular histogram in Figure 2b.
- https://cdn.elifesciences.org/articles/110015/elife-110015-fig2-data5-v1.zip
-
Figure 2—source code 1
R code used to calculate movement directions from tracking coordinates and generate the circular histogram for Ranina ranina in Figure 2b.
- https://cdn.elifesciences.org/articles/110015/elife-110015-fig2-code1-v1.zip
-
Figure 2—source code 2
R code used to calculate movement directions from tracking coordinates and generate the circular histogram for Geothelphusa dehaani in Figure 2b.
- https://cdn.elifesciences.org/articles/110015/elife-110015-fig2-code2-v1.zip
Figure 2—figure supplement 1
Circular histograms showing movement direction for species 1–16.
Numbers in the plot correspond to the species numbers shown in Figure 1—figure supplement 2.
Figure 2—figure supplement 2
Circular histograms showing movement direction for species 17–32.
Numbers in the plot correspond to the species numbers shown in Figure 1—figure supplement 2.
Figure 2—figure supplement 3
Circular histograms showing movement direction for species 33–50.
Numbers in the plot correspond to the species numbers shown in Figure 1—figure supplement 2.
Figure 3 with 1 supplement
Ancestral state reconstruction of locomotion in crabs under the all-rates-different (ARD) model.
Gold circles at the tips indicate forward locomotion, whereas blue circles indicate sideways locomotion. Pie charts at internal nodes and along branches represent the posterior probabilities of each locomotor state, estimated from 500 stochastic character maps. The x-axis shows geological time, scaled in millions of years before present (mya).
-
Figure 3—source data 1
Pruned phylogenetic tree used for the ancestral-state reconstruction in Figure 3, provided in Newick format.
- https://cdn.elifesciences.org/articles/110015/elife-110015-fig3-data1-v1.zip
-
Figure 3—source data 2
Continuous FSI values and discrete forward/sideways locomotor states for the 50 terminal taxa used in the ancestral-state reconstruction in Figure 3.
- https://cdn.elifesciences.org/articles/110015/elife-110015-fig3-data2-v1.zip
-
Figure 3—source code 1
R code used for stochastic ancestral-state reconstruction of forward and sideways locomotion and generation of Figure 3.
- https://cdn.elifesciences.org/articles/110015/elife-110015-fig3-code1-v1.zip
Figure 3—figure supplement 1
Ancestral state reconstruction of locomotion in crabs under the equal-rates (ER) model.
Gold circles at the tips indicate forward locomotion, whereas blue circles indicate sideways locomotion. Pie charts at internal nodes and along branches represent the posterior probabilities of each locomotor state, estimated from 500 stochastic character maps. The x-axis shows geological time, scaled in millions of years before present (mya).
Figure 4
Video acquisition and analysis workflow.
(a) Experimental setup used to record each crab’s behavior. (b) Extraction of two-dimensional position coordinates from video frames.
Figure 5
Method for determining movement directions of each crab.
For each movement bout, movement direction was defined as the angle between the previous body axis (from tail to head) and the displacement vector of the body’s center (referred to as the midpoint). Displacement was measured when the midpoint reached the reference circle. These values across all movement bouts were then used to calculate the Forward–Sideways Index (FSI).
Additional files
Download links
A two-part list of links to download the article, or parts of the article, in various formats.
Downloads (link to download the article as PDF)
Open citations (links to open the citations from this article in various online reference manager services)
Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)
Evolution of sideways locomotion in crabs
eLife 15:RP110015.
https://doi.org/10.7554/eLife.110015.3
