Brasseur L et al. (2018), Identification and quantification of spinochrom...

ECB-ART-46595

R Soc Open Sci 2018 Aug 01;58:171213. doi: 10.1098/rsos.171213.

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Identification and quantification of spinochromes in body compartments of Echinometra mathaei''s coloured types.

Brasseur L , Demeyer M , Decroo C , Caulier G , Flammang P , Gerbaux P , Eeckhaut I .

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Sea urchin pigmentation is mainly due to polyhydroxy-1,4-naphthoquinones called spinochromes. If their molecular structures are well known in test and spines of many species, their abundance and distribution in other body compartments remain unstudied. The aim of this study is to analyse the pigment composition in four body compartments (test/spines, digestive system, gonads and coelomic fluid) of four coloured types of the sea urchin Echinometra mathaei. Qualitative and quantitative measurements by mass spectrometry highlight the existence of 13 different pigments; among which are five isomers of known spinochromes as well as three potentially new ones. The composition comparison shows the largest spinochrome diversity in ''test/spines'' body compartments. The spinochrome concentrations vary from 48 to 1279 mg kg-1 of dried body compartment. It is the highest in the digestive system, although it is also important in the organic fraction of the ''test/spines'' body compartment. This observation may be explained by higher exposures of some body compartments to external environments and by the protective role fulfilled by spinochromes against microorganisms, ultraviolet radiation and reactive oxygen species. The ''black'' type-the most common coloured type in coral reefs-has the highest concentration of spinochromes indicating their importance in Echinoids'' fitness by acting as a protective agent.

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Genes referenced: irak1bp1 LOC100887844

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	Figure 1. Coloured types of the collected E. mathaei. From right to left: black, purple, brown and green.
	Figure 2. Description of (a) E. mathaei type population in Toliara bay (Madagascar), (b) wet weight (g) of sampled individuals of E. mathaei (n = 5), (c) diameter (cm) of sampled individuals of E. mathaei (n = 5), (d) dried body compartment weight (g) of sampled individuals of E. mathaei (n = 5).
	Figure 3. PHNQ molecular structures from E. mathaei. Isomers of the Spinochrome A and the Spinochrome D are not represented in this figure. The Echinamine A and B are both represented as we cannot make a clear-cut distinction. The potentially new PHNQ are represented with their hypothetical defined functional groups. The annotation is defined as the number of functional groups × Rposition on figure = functional group.
	Figure 4. Full scan (−) mass spectrum of the PHNQ extract from test and spines from the ‘black’ type of E. mathaei (third replicate). MS signal annotated by ion mass corresponds to PHNQ molecules identified in E. mathaei and listed in table 2.
	Figure 5. LC-MS analysis of the PHNQ extract from test and spines from the ‘black’ type of E. mathaei (third replicate). Peaks are annotated by numbers assigned to PHNQ molecules identified in E. mathaei and listed in table 3. The chromatogram time window is limited to the first 10 min in this figure for clarity.
	Figure 6. Hypothetical molecular structures of isomers and new PHNQ molecules from E. mathaei based on retention time. The annotation is defined as Rpossible position(s) on figure = functional group. The ‘/’ on R annotation shows the possibility of choice between two positions. The ‘,’ on R annotation shows all positions of the functional groups. The ‘*’ on R annotation means that if one position of the first functional group is chosen, the position of the other functional group has to be the complementary number (e.g. if the position of the methyl group on the Spinochrome 252 is the R4, the position of hydroxyl group will be the R7).
	Figure 7. Comparison of the PHNQ contents of the body compartments from different coloured types of E. mathaei. The intensities of the PHNQ ions observed in the mass spectrum, the IS intensity and the dried body compartment weight are used to calculate the main normalized content of each PHNQ molecule. The exact values of means and their standard deviations are detailed in table 3.

References [+] :

Ageenko, Pigment cell differentiation in sea urchin blastula-derived primary cell cultures. 2014, Pubmed, Echinobase