Hymedesmia paupertas (Bowerbank, 1866)
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publication ID |
https://doi.org/ 10.1007/s13127-013-0163-1 |
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persistent identifier |
https://treatment.plazi.org/id/03C687ED-3268-FFA0-FCE7-FE68C3A9FBE6 |
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treatment provided by |
Felipe |
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scientific name |
Hymedesmia paupertas |
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Hymedesmia paupertas View in CoL
An accurate mass search in DNP indicated that pigment 7 ( Table 1) detected from HPLC and LC-MS was lactarazulene, with OD(λ)max at 291, 376 and 605 nm. Absorbance spectra (350–700 nm) of lactarazulene from HPLC had only two OD(λ)max peaks at 376 nm and 605 nm ( Fig. 4a View Fig ). The corresponding absorbance spectra of lactarazulene detected from LC-MS was taken from the UV region to the green part of the visible spectrum, i.e. 220 nm – 500 nm with OD(λ)max at 291 nm and an OD(λ)max at 376 nm was measured ( Fig. 4a View Fig ). Pigment 7 suspected to be lactarazulene was purified and submitted to NMR analysis. Proton and carbon-13 NMR shifts were recorded and assigned unambiguously to lactarazulene with the help of 2D NMR methods. Additionally, the proton NMR shifts were compatible with those in the literature ( Takekuma et al. 1988). Carbon-13 NMR shifts in CDCl3 have, to our knowledge, not been reported previously. However, the reported 13C chemical shifts in C6D6 show close resemblance to our findings ( Fehler 2005) ( Table 2). There were several other pigments separated by HPLC that absorb in wavebands that potentially could be contributing to the colour of the sponge, but not all were identified (pigments 10–12, Table 1, Fig. 4b View Fig ). Chlorophyll a [Chl a, OD(λ)max 431 nm and a b c
1.6 0.014 1.2 1.2
1.4 0.012
1 1
1.2) 0.01 R 0.8 0.8 (
OD 0.8
1
OD
0.008
OD 0.6 0.6 Reflectance
0.6 0.004
0.006
0.4 0.4 Relative
0.4
0.2
0.002 0.2 0.2
0 0 0 0
250 350 450 550 650 350 400 450 500 550 600 650 700 380 430 480 530 580 630 680
Wavelength (nm) Wavelength (nm) Wavelength (nm)
8–12) detected with HPLC. c Absorbance spectra in vivo OD(λ) and in vitro OD(λ) plotted against reflection spectra in vivo R(λ) from the HI, illustrating that the OD(λ) spectra are inversely related to the R(λ) spectra. The spectra have been scaled to 1 at highest OD(λ) and R(λ) for easier comparison
663 nm, pigment 8] and diatoxanthin [OD(λ)max 454 nm and 484 nm, pigment 9] were identified by HPLC ( Table 1), but the concentration of these and the unidentified pigments were trace amounts compared to the concentration of lactarazulene. These results show that lactarazulene is the main pigment responsible for the blue colour of the sponge, whereas no epifauna were registered on the sponge. It is most likely that Chl a and diatoxanthin have entered the sponge matrix through filtration of water containing phytoplankton.
In vivo and in vitro absorbance spectra indicated high absorbance at wavelengths <380 nm and high absorbance in a broad wavelength band from 600 to 650 nm ( Fig. 4c View Fig ), corresponding to the absorbance spectra of lactarazulene. The HI R(λ) spectra were high for the 430–575 nm wavelength area with a R(λ)max at 475 nm, the OD(λ) for in vivo, in vitro and lactarazulene were correspondingly low in the same area ( Fig. 4c View Fig ) and show that R(λ) and OD(λ) for H. paupertas were inversely related. Chl a, diatoxanthin and the unidentified pigment (pigment 10–12) absorbs in the 400– 500 nm wavelengths ( Fig. 4b View Fig ), but does not seem to have a significant impact of the reflectance, probably due to its low concentration.
From the red coloured Hymedesmia sponge, four pigments were detected by LC-MS analysis ( Fig. 5a View Fig ). Following a DNP search to identify the pigments, pigment 13 had no hits in the database and remained unidentified ( Table 1). The DNP database search returned three hits for pigment 14, 2(3H)- benzothiazolethione and two derivatives of the same compound ( Fig. 5a View Fig ). Like 2,6-benzothiazolediol and its derivatives from I. pacmata , 2(3H)-benzothiazoletione has been isolated from Micrococcus sp. in Tedania ignis and this might therefore be the source of the pigment isolated from Hymedesmia sp. 13-Propanoyloxylupanine (Pigment 15)—a derivative of 13-hydroxylupanin isolated from the plant genus Lupinus sp. —was also detected in Hymedesmia sp. , absorbing in the ultraviolet part (ODmax 284 nm). Pigment 16 detected from Hymedesmia sp. absorbs in the range of 400–550 nm with a OD(λ)max at 486 nm ( Fig. 5 View Fig ) indicating that this is the main spectra are inversely related to the R(λ). The spectra have been scaled to 1 at highest OD(λ) [except in vitro OD, which have been scaled to 1 at 471 nm, which is the highest OD(λ) for the indicated pigment absorbing in the visible spectrum] and R(λ) for easier comparison pigment responsible for the red colour of the sponge. The DNP database returned four hits for the pigment and three for potential pigment candidates have been isolated previously from the marine environment ( Table 1). Tedanin has been isolated from the sponges Tedania digitata and Ccathria frondifera, isotedanin from the sponge Agecas mauritiana ( Britton et al. 2004), 3,3′-dihydroxyleprotene from marine bacteria and 3.3.4.4′-tetrahydro-β,β- carotene-2.2′-dione from Carausius morosus (Phylum Arthropoda); this latter compound is most likely the pigment responsible for the colour of Hymedesmia sp. as it has been isolated from the marine environment before, but further analysis is needed to have certain identification.
The in vitro OD(λ) spectra corresponded to the absorption of pigments detected from LC-MS analysis in Fig. 5a View Fig with OD(λ)max at 284, 343, 411 and 471 nm. The in vivo OD(λ) spectra were not as pronounced as the in vitro spectra but had clearly a ODmax at 485 nm corresponding to pigment 16.
Most of the pigments detected from Hymedesmia sp. absorbed in the UV region, below the detection limit of the HI, as was the unidentified pigment 13 ( Table 1, Fig. 5a View Fig ). HI R(λ) spectra were inversely related to the OD(λ) spectrum of Hymedesmia sp. ( Fig. 5b View Fig ).
This study has initiated a spectral library of verified bio-optical signatures measured with HI and UHI. Objects of interest were identified using three different approaches: (1) traditional taxonomy based on morphology, needle preparation and colour (OOI was first sampled and then identified); 2) chemo-taxonomy (pigment isolation and characterisation, HPLC, LC-MS-QTOF, and NMR); and (3) bio-optical identification (HI and spectrophotometry). Morphological-featurebased taxonomy is time-consuming and expensive and misidentification can occur due to inexperience or the presence of morphological features that are not always species-specific. Chemo- and bio-optical taxonomy has been used for more than three decades for phytoplankton and macroalgae ( Roy et al. 2011), but obtaining pigment composition and corresponding optical signatures is quite a new approach for benthic animals ( Elde et al. 2012). Bio-optical identification (absorbance, reflectance and fluorescence exCitation spectra) has been used widely for both remote sensing and for in situ monitoring of micro- and macroalgae (reviewed by Johnsen et al. 2011). Hyperspectral imaging is a new identification technique for shallow-living marine organisms, corals, seagrass and micro- and macro-algae ( Klonowski et al. 2007; Volent et al. 2007). UHI has the potential to be a more automated method when used as a sensor on underwater robots such as ROV and AUVs ( Moline et al. 2005; Johnsen et al. 2013b). The use of HI as a taxonomic identification tool can be used unsupervised by discriminating between unknown OOI, or in supervised classification (as in this study) identifying and mapping an OOI with a known pigment signature. One problem that might arise, especially for organisms with a pigment content influenced by pigmented heterotrophic bacteria, is that the abundance and species distribution of pigmented microbes are influenced heavily by environmental properties such as temperature, salinity, nutrient level and competition for resources ( Hailian et al. 2006). Therefore, a given taxa may have diverse colorations and optical signature that may not be the same over any given distinct geographical and ecological areas; information of this sort also needs to be incorporated in the spectral library for world wide use. Also, many organisms have pigments absorbing in the UV part of the electromagnetic spectrum and it is possible that these pigments would be better suited to separate visibly similar coloured organisms. Extending the pigment search area into shorter wavelengths increases the opportunity to find species-specific absorbance traits (marker pigments).
The prototype HI sensor used in this study had low sensitivity at wavelengths below 420 and above 680 nm, while several of the pigments that characterised the OOI absorb below 420 nm into the UV region. A more UV and infrared (IR) sensitive sensor, with higher spatial and radiometric resolution has been developed and used with success on a ROV covering large areas of seafloor for habitat mapping and also creating geo-localised seafloor maps ( Johnsen et al. 2013a, b; Ludvigsen et al. 2013), but even more sensitive sensors needs to be developed to ensure more reliable and powerful identification and mapping tools for all kinds of marine organisms.
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