Bioerosion by pit-forming, temperate-reef sea urchins: History, rates and broader implications
Fig 6
Field estimates of sizes of pits and urchin occupants.
Cube-root of pit volume plotted against cube-root of test volume of urchin occupant. Sandstone = tan circles (n = 50); mudstone = brown squares (n = 47); granite = gray diamonds (n = 9). ANCOVA revealed no significant difference in slopes and the same regression described all three data sets (r2 = 0.91, F1,95 = 956.7, p<0.0001). Least squared means of sandstone and mudstone were not significantly different from each other but both were significantly different from granite. The silhouettes of urchins and pits are scaled-sizes of the average diameter and height of urchins, and depth and width of the pits. The urchin silhouettes contain the average height:diameter ratios of the tests, which had the same pattern (no difference between sandstone and mudstone, but both sedimentary rocks were different from granite).