Stylatula sp.

Chen, Jei-Ying & Williams, Gary C., 2015, X-ray Microanalysis and the Chemical Elemental Composition of Gorgonian and Pennatulacean Axial Structures (Anthozoa, Octocorallia), Proceedings of the California Academy of Sciences 62 (16), pp. 399-415 : 410-412

Stylatula sp.

Figures 11A–B, 12A–B , 13A–F .

From the element linescan graph Figure12B one can easily identify the dramatic drop of the calcium (in dark blue) weight percentage right on the range of the central core region, while other elements like carbon (in red), magnesium (in green), aluminum (in light green) and fluorine (in yellow) are increasing in value instead. Also noticeable are the void zones on both sides of the central core, which may probably be caused by the discontinuity of the surface on the boundaries between the core and the peripheral axis that ultimately resulted in the discontinuity of the X-ray detection as well. One single peak of calcium is shown in the central core region, which might be attributed to the broken pieces of debris from the more calcareous fringe of the core-axis intersection. The line patterns of most other elements like sodium (in dark green), silicon (in light blue), sulfur (in blue), strontium (in pink), ytterbium (in purple) and iron (in magenta) are relatively smooth compared to the big shifts of the line patterns of the elements mentioned above; thus, we know that those elements have more even overall distributions along the transect line.

Two area scans were performed between the two highly different atomic number contrast areas — the outer region of the axis and the central core — to determine the chemical compositions of the two distinct sites. From EDS results and the bar chart of spectrum 1, eleven elements were found as follows — three major elements: carbon (18.76 wt%), oxygen (40.09 wt%) and calcium (37.07 wt%); two minor elements: fluorine (1.47 wt%) and magnesium (1.48 wt%); and six trace elements: sodium (0.35 wt%), aluminum (0.08 wt%), iron (0.04 wt%), strontium (0.09 wt%) and REE ytterbium (0.22 wt%). The weight percentage of all elements can be seen in Table 6. This finding suggests that the outer region of the axis has a similar chemical distribution to most other species examined previously in having similar identified elements.

TABLE 6. EDS results of spectrum 1 for sea pen Stylatula sp. axial cross-section surface from

Figure 13A . (All results are in weight%)

Element ਖ F Na Mg Al S Ca Fe Sr Yb Total Spectrum 1

18.76 40.09 1.47 0.35 11.48 0.08 0.35 37.07 0.04 0.1 0.22 100 (Weight%)

Surprisingly, the EDS results from spectrum 2 showed dramatic changes in chemical composition of the central core; the most obvious change is the enormous drop in calcium weight percentage from 37.07 wt% to 0.32 wt%, making carbon a trace element, instead of as the always prominent major element; a large decrease in oxygen weight percentage is also observed, from 40.09 wt% to 8.46 wt%; while sulfur and iron weight percentage remain almost unchanged. Other changes include the addition of silicon and largely elevated amounts of carbon (from 18.76 wt% to 60.07 wt%), fluorine (from the previously 1.47 wt% to 24.14 wt%), and aluminum (from 0.08 wt% to 5.57 wt%), which make fluorine now a major element and aluminum now a minor element. The new discovery of barium is also surprising inasmuch as no other species examined here has been shown to contain barium. The overall element list for the identified twelve elements of spectrum 2 is shown in Table 7.

TABLE 7. EDS results of spectrum 2 for sea pen Stylatula sp. axial cross-section surface from

Figure 13A . (All results are in weight%)

Element ਖ F Na Mg Al Si ᜙ Ca Fe Ba Total Spectrum 2

60.07 8.46 24.14 0.02 0.08 5.57 0.25 0.04 0.32 0.32 0.09 0.64 100 (Weight%)

412 PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES Series 4, Volume 62, Part 2, No. 16

Figures

FIGURE 12. Energy dispersive spectrometer (EDS) linescan dataset. (A) EDS linescan site of interest BSE image in a cross-sectional view of a sea pen Stylatula sp. axial skeleton acquired by INCA Energy software using same region as Figure 11, horizontal linescan through the middle of the axis was applied for EDS analysis to examine the distribution of elements along the line. Scale bar = 900 μm. (B) Element linescan result displaying grouped linescans as colored: carbon (red), oxygen (orange), fluorine (yellow), sodium (green), magnesium (light green), aluminum (bright green), silicon (aqua), sulfur (light blue), calcium (blue), strontium (pink), ytterbium (purple), iron (hot pink).

FIGURE 13. Energy dispersive spectrometer (EDS) area scan dataset. (A) and (B) EDS site of interest BSE image in a higher magnification cross-sectional view of the sea pen Stylatula sp. axial skeleton, acquired by INCA Energy software, partial area scans (spectrum 1 and 4) were applied for between site comparison purpose. Scale bar = 300 μm. (C) and (D) Bar charts of the quantitative results from spectrum 1 and spectrum 4. (E) and (F) EDS results for spectrum 1 and 4.