Coral Coloration, Part 2: Fluorescence: Pigments 510 – 565 and Notes on Green Fluorescent Proteins

In Part 1 of this series, we began our review of fluorescent
pigments and also discussed the concepts of fluorescence
excitation and emission, Stokes shift, photoconversion and so
on. A review of that article is recommended if you are
unfamiliar with any of these terms. This time, our discussion
continues with green, yellow-green and yellow fluorescent
pigments and a few hypotheses concerning their function.
We’ll also see a couple of cases where light energy of
specific bandwidths has induced coloration changes.

IntroPhoto.jpg

This Hawaiian soft coral (Sinularia densa) demonstrates green fluorescence.
The reddish coloration is that of zooxanthellae or algal fluorescence.

Green fluorescence is perhaps the most common of any seen in
aquaria. Well over half of the 70 or so known fluorescent
pigments spanning 9 color categories can be described as
‘greenish.’ Fluorescence of green fluorescent
proteins (GFPs) can also combine with other
‘glowing’ pigments to form any number of
colors.

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Table 4 lists
the fluorescent proteins by emission maxima as described in
various works:

Table 4: Fluorescent Proteins by Emission Maxima
PigmentEmission23Excitation2Found in:Reference
P-510510479***Montastraea annularisMazel, 1995
P-510510****Ricordea floridaMazel, 1995
P-510510**498*Renilla muelleri (sea pansy)Labas et al., 2002
P-510510**490420Heteractis magnificaTu et al., 2003
P-510510**440*Montastraea cavernosaMazel et al., 2003
P-510-520510-520**440*Montastraea faveolataLesser et al., 2000
P-510-520510-520**440*Montastraea cavernosaLesser et al., 2000
P-510-623510-623****Montastraea cavernosa @ 40mVermeij et al., 2002
P-511511****Plesiastrea verispora (green morph)Salih et al., 2004
P-512512**503*Discosoma sp. 3Labas et al., 2002
P-512512****Plesiastrea verispora (blue morph)Salih et al., 2004
P-512512****Plesiastrea verispora (green morph)Salih et al., 2004
P-513513545490**Agaricia sp.Mazel, 1995
P-513513****Ricordea floridaMazel, 1995
P-514514490*501480Acropora asperaPapina et al., 2002
P-514514****Montastraea cavernosaKelmanson & Matz, 2003
P-515515****Mycetophyllia lamarckianaMazel, 1997
P-515515**~494*Mycetophyllia sp.Fux and Mazel, unpublished
P-515515**505*Montastraea annularisMazel, 1997; Manica & Carter, 2000
P-515515±3**505±3*Montastraea cavernosa (mc2/3/4)Kelmanson & Matz, 2003
P-515515****Lobophyllia hemprichii (red)Salih et al., 2004
P-515515****Colpophyllia natansFux and Mazel, unpublished
P-515515****Scolymia sp.Mazel, 1997
P-515515****Plesiastrea verispora (green morph)Gilmore et al., 2003
P-515515****Plesiastrea verispora (green morph)Salih et al., 2004
P-515515****Agaricia sp.Mazel, 1995
P-515515****Ricordea sp.Mazel, 1995
P-516516**486*Pocillopora damicornisSalih et al., 2000
P-516516**506~480Montastraea cavernosa (=mc2/3/4 – see P-515)Labas et al., 2002
P-516516****Lobophyllia hemprichiiNienhaus et al., 2005
P-517517555485505465Acropora tenuisPapina et al., 2002
P-517517574*506566Ricordea floridaLabas et al., 2002
P-517517**506*Ricordea floridaMazel, 1995
P-517517**507*Favia favusTsutsui et al., 2005
P-517517551483**Montastraea annularisMazel, 1995
P-518518**508475Ricordea floridaLabas et al., 2002
P-518518****Acropora cytheria @ Waikiki AquariumHochberg et al., 2004
P-518518****Acropora digitiferaHochberg et al., 2004
P-518518****Plesiastrea verispora (green morph)Salih et al., 2004
P-518518****Montastraea cavernosaKelmanson & Matz, 2003
P-518518**503*Family PectiniidaeAndo et al., 2004
P-518518****Ricordea floridaMazel, 1995
P-519519**~505*Montastraea cavernosaKelmanson & Matz, 2003
P-519519****Lobophyllia hemprichii (red)Salih et al., 2004
P-519-557519-557590***Madracis carmabiVermeij et al., 2002
P-519-559519-559590***Madracis senariaVermeij et al., 2002
P-519-570519-570590-615***Madracis pharensis (green tissue)Vermeij et al., 2002
P-520520****Ricordea floridaMazel, 1995
P-520520**488*Goniopora tenuidensSalih et al., 1999
P-520-555520-555590***Madracis carmabiVermeij et al., 2002
P-520-558520-558590***Madracis senariaVermeij et al., 2002
520-570520-570590***Madracis pharensis (green tissue @ 10m)Vermeij et al., 2002
520-570520-570590***Madracis pharensis (green tissue @ 20m)Vermeij et al., 2002
520-570520-570590-620***Madracis pharensis (green tissue @ 40m)Vermeij et al., 2002
520-570520-570590***Madracis pharensis (green tissue @ 60m)Vermeij et al., 2002
P-522522**499**Anemonia sculata var. rufescensWiedenmann et al., 2000
P-522522****Montastraea cavernosaKelmanson & Matz, 2003
P-522-623522-623****Madracis formosa @ 40mVermeij et al., 2002
P-530530**450**Porites astreoidesMazel, 2003
P-532532590***Madracis pharensis (brown tissue @ 10m)Vermeij et al., 2002
P-532532****Madracis pharensis (red tissue @ 10m)Vermeij et al., 2002
P-533533590***Madracis pharensis (brown tissue @ 20m)Vermeij et al., 2002
P-534534575***Madracis formosa @ 60mVermeij et al., 2002
P-534534593***Montastraea cavernosa @ 60mVermeij et al., 2002
P-535535587***Madracis pharensis (brown tissue @ 60m)Vermeij et al., 2002
P-537537590***Madracis pharensis (grey and blue tissue @
10m)
Vermeij et al., 2002
P-538538~580*528494Zoanthus 2Matz et al., 1999
P-538538**525494Zoanthus sp.Yanushevich et al., 2002
P-540540****Plesiastrea verispora (blue morph)Salih et al., 2004
P-540540****Plesiastrea verispora (green morph)Salih et al., 2004
P-542542****Agaricia undata @ 40mVermeij et al., 2002
P-550550**530*Porites murrayensisDove et al., 2001
P-557557600545**Agaricia sp. Mazel, 1995
P-559559590***Madracis senaria @ 60mVermeij et al., 2002
P-560560590***Madracis pharensis @ 10m (grey tentacles)Vermeij et al., 2002
P-561561**548*Fungia concinnaKarasawa et al., 2004
P-561561587-616***Madracis senaria @ 40mVermeij et al., 2002
CP-562***562*Anemonia sulcata, immature P-595Wiedenmann et al., 2002
P-565565**490*Agaricia humilisMazel et al., 2003
P-565565**548*Cerianthus sp.Ip et al., 2004
P-573573510***Ricordea floridaMazel, 1995
P-574574517*506566Ricordea floridaLabas et al., 2002
P-574574550***Plesiastrea verisporaDove et al., 2001
P-575575~630*~525~570Montastraea cavernosaMazel, 1997
P-575575**506555Montipora (digitata/angulata)Mazel, unpublished
P-575575**557*DendronephthyaPakhomov et al., 2004
P-575575630*520*Scolymia sp.Mazel et al., 2003
P-575575**~569~540Phycoerythrin within symbiotic cyanobacteria in
coral
Mazel et al., 2004

Comments about
Green Fluorescent Proteins

It seems quite clear that GFPs emissions are quite varied
and abundant in coral reef animals. At least some GFPs require
the presence of oxygen for maturation – the transition
from a colorless state to one of fluorescence with the emission
peaking in the green portion of the spectrum, yet once mature,
oxygen apparently has no further effect (Tsien, 1998).
However, modification of environment can cause further
color-shifting, resulting in various apparent colorations
(Labas, 2002).

Fluorescent Coloration is Not Produced by
Zooxanthellae!
This is one of the persistent myths
within the hobby yet there is no data to support this
view. To the contrary, the evidence does support
fluorescent pigment production by the host. Kawaguti
(1966) shows several electron photomicrographs of pigment
granules apparently being produced by a coral cell’s
endoplasmic reticulum. With that said, zooxanthellae
pigmentation (photopigments including chlorophyll a,
, peridinin and perhaps others) can greatly
influence the non-fluorescent coloration ranging from brown to
yellow-green.

Possible
Functions of GFP-like Compounds

Opinions on possible function (or non-function) of
fluorescent proteins are almost as numerous as the number of
papers addressing the subject. Here are a few:

Photoprotection? Perhaps the most popular concept is
one where pigments act as sunscreens – photoprotectants
– against ultraviolet or visible radiation. Fairly early
on in the course of ‘serious’ coral reef studies,
Kawaguti (1944) was of the opinion that fluorescent pigments in
corals act to shield symbiotic zooxanthellae from ‘strong
sunlight.’ His idea became mantra for decades and
sporadic re-visitations seemed to confirm his thoughts (see
Salih et al., 1998; Salih et al., 2000 and others).

Fluorescent pigments can cause a reflection of light, which
can be 40-80% higher than that of adjacent
non-fluorescent cells (Salih et al., 1998), leading to the
conclusion that polyp retraction can produce a highly
reflective layer of varying optical density thereby protecting
gonads and high-growth areas (polyp tips,
‘anchoring’ basal tissues).

However, Mazel et al. (2003) found no photoprotective
quality associated with green fluorescent proteins (with
emission spectra peaking at 500nm to 518nm
bandwidth).

A Photosynthetic Aid? Schlichter et al. (1985) were
perhaps the first to describe fluorescence as a potential aid
to photosynthesis. These researchers documented
behavior of fluorescent granules and dispersed pigmentation in
the deep-water coral Leptoseris fragilis (found at
depths of 100-145m, or ~325-475’ at Eilat, Israel on the
Red Sea). Normally, this coral appears dark brown since its
chromatophores (pigment-containing granules) are beneath a
layer of symbiotic zooxanthellae. However, the color changes
from to green in less than 1 minute after coral is transferred
to daylight conditions. It is thought that host tissue
contractions could force zooxanthellae downwards, or move
chromatophores upwards through displacement, possibly via a
vascular microtubule system within the coral’s tissue.
Schlichter states that violet light is absorbed by the host
pigment and is fluoresced as bluish-green light that is usable
in photosynthesis. These deep-water corals receive only up to
10 µmol·m²·s PAR at noon and would need to
efficiently collect light – much radiation making it
through a densely packed zooxanthellae layer above the
fluorescent pigment could be absorbed and fluoresced in an
altered wavelength. Though the paper does not state as much, it
could be that fluorescence shifts absorbed wavelengths to a
bandwidth normally rarified at this depth thus avoiding
photosaturation at those wavelengths usually transmitted
through the water column. See Figure 36.

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In a later paper, Schlichter et al. (1986) further discuss
that pigment granules (chromatophores) fluoresce reddish while
the intense turquoise autofluorescence seems dispersed
throughout the cytoplasm, and is not in any specialized
structure. Interestingly, we could speculate that the red
fluorescence is also of benefit to
photosynthesis.

Fig36.JPG

Figure 36. The colored lines
represent excitation and emission – the excitation being
the initial peak. Fluorescence is noted at excitation
wavelengths of 380, 390 and 400 nm. Little fluorescence is
noted when the pigment(s) is exposed to bandwidths peaking at
430 and 510nm. After Schlichter et al., 1986.

Phototaxis: A Beacon for Zooxanthellae? This
rather interesting concept involves phototaxis (a movement of
an animal or plant towards light) and was proposed by
Hollinsworth et al. in 2005. Cultured motile
(non-symbiotic) zooxanthellae were exposed to white light which
was split into a spectrum and projected on the culture flask.
The idea was to determine if these dinoflagellates had a
preference for any particular ‘color.’ Apparently
they did – they swarmed in the area illuminated by green
light. Blue light attracted significantly fewer zooxanthellae.
Interestingly, previous observations suggested the motile
zooxanthellae would move out of the area irradiated with
ultraviolet wavelengths. These observations prompted a
hypothesis – green fluorescence may act as a beacon,
attracting free-swimming zooxanthellae to coral recruits or
planulae. Of course, other factors are undoubtedly in involved
with corals attracting symbionts – corals are known to
release chemical cues to the environment and it has been proven
that zooxanthellae can swim against weak currents to reach a
host (Pasternak et al., 2006). If we were to mesh these
observations, we might arrive at the hypothesis that chemical
cues released by the coral act as a navigational beacon to
potential symbionts while green fluorescence is akin to landing
strip lights.

GFP: A Shading Function for Photoreceptors?
This thought was advanced in a paper by Shagin et al.
(2004) and briefly discussed the possibility that GFP might
shield the photoreceptors of the jellyfish Aequorea
victoria
. In addition, Burr et al. (2000) advanced the
possibility of a protein (hemoglobin) in a nematode as possibly
possessing an optical function. (Hemoglobin concentrates
densely around Mermis nigrescens’
photoreceptor and is thought to play a role in
phototaxis.) Some coral species have photoreceptors as
well (Gorbunov and Falkowski, 2002), but to my knowledge no one
has advanced a hypothesis linking fluorescence and protection
of coral photoreceptors via optical shading. However a
shielding function by GFP has been suggested for the
non-photosynthetic soft coral Carijoa riisei
(Khang and Salih, 2005).

This ends our discussion of potential functions of GFPs, and
we will now turn our attention to specific green fluorescent
proteins beginning with P-512.

Green-Blue
Pigments

P-512

Host: Discosoma, Pigment 3

  • Excitation: 503nm
  • Emission: 512nm
  • Stokes shift: 9nm
  • Reference: Labas et al., 2002
  • Comments: P-512 is one of several identified in the Discosoma genus.
    See Figure 37.
Fig37.JPG

Figure 37. This pigment absorbs blue and blue-green light.
After Labas et al., 2002

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P-513

Host: Agaricia sp.

  • Excitation: Not listed
  • Emission: 513nm
  • Stokes shift: N/A
  • Reference: Mazel, 1995
  • Comments: With shoulders at 545 nm and 490 nm. See Figure
    38.

Host: Ricordea florida

  • Excitation: Not listed
  • Emission: 513nm
  • Stokes shift: N/A
  • Reference: Mazel, 1995
  • Comments: In addition to the peak fluorescence at 513nm, Ricordea florida reportedly
    has a single shoulder at ~550-565nm. (R. florida specimens are
    variously colored green, blue, fluorescent orange, pink, copper, yellow
    and multiple combinations – Sprung and Delbeek, 1997).
Fig38.JPG

Figure 38. Note that the
chart’s line represents the emission spectrum. The
absorption curve probably resembles that in Figure 37. After
Mazel, 1995.

P-514

Host: Acropora aspera

  • Excitation: 501nm, shoulder at 480nm
  • Emission: 514nm, shoulder at 490nm
  • Stokes shift: 13nm
  • Reference: Papina et al., 2002
  • Comments: Collected off the coast of Okinawa, Japan in 1.5m
    of water, in August of 2001. This Acropora specimen
    appeared yellow-green in natural light and fluoresced
    bluish-purple when excited with UV-A radiation peaking at
    365nm. Shifts in pH (5.0-8.0) do not significantly affect
    excitation and emission wavelengths or fluorescent quantum
    yield. See Figure 39.

Host: Montastraea cavernosa

  • Excitation: ~505nm
  • Emission: 514nm
  • Stokes shift: ~9nm
  • Reference: Kelmanson and Matz, 2003
  • Comments: Found in a red M. cavernosa specimen
    collected in the Florida Keys National Marine
    Sanctuary.

Host: Entacmaea quadricolor (Actinaria)

  • Excitation: N/A
  • Emission: 514nm
  • Stokes shift: N/A
  • Reference: Wiedenmann et al., 2002
  • Comments: Precursor to P-611. The fluorescence is stable
    over a pH range of 4-10.
Fig39.JPG

Figure 39. More than a few
hobbyists have seen this particular fluorescent pigment. After
Papina et al., 2002.

P-515

P-515’s fluorescence can contribute significantly to
daylight appearance and is often found in conjunction with
other fluorescent pigments (Fux and Mazel, 1999).

Host: Mycetophyllia lamarckiana

  • Excitation: ~500-505nm
  • Emission: 515nm
  • Stokes shift: 10-15nm
  • Reference: Mazel, 1997
  • Comments: See Figure 40.

Host: Montastraea annularis

  • Excitation: Not listed
  • Emission: 515nm
  • Stokes shift: N/A
  • Reference: Mazel, 1997

Host: Montastraea sp.

  • Excitation: Not listed
  • Emission: 515nm
  • Stokes shift: N/A
  • Reference: Fux and Mazel, unpublished

Host: Montastraea cavernosa

  • Excitation: 505±3
  • Emission: 515±3nm
  • Stokes shift: ~10nm
  • Reference: Kelmanson and Matz, 2003.
  • Comments: M. cavernosa can contain a number of
    pigments. There are several with similar emissions, and are
    referred to as P-515±3 by Kelmanson and Matz. See Figure 41.

Host: Scolymia sp.

  • Excitation: Not listed
  • Emission: 515nm
  • Stokes shift: N/A
  • Reference: Fux and Mazel, unpublished

Host: Mycetophyllia sp.

  • Excitation: Not listed
  • Emission: 515nm
  • Stokes shift: N/A
  • Reference: Fux and Mazel, unpublished

Host: Colpophyllia sp.

  • Excitation: Not listed
  • Emission: 515nm
  • Stokes shift: N/A
  • Reference: Fux and Mazel, unpublished

Host: Plesiastrea verispora

  • Excitation: Not listed
  • Emission: 515nm
  • Stokes shift: N/A
  • Reference: Gilmore et al., 2003.
  • Comments: These Plesiastrea specimens (appearing blue
    in natural light due to a non-fluorescent chromoprotein) were
    collected in 5-9m of water at Port Jackson,
    Australia.
Fig40.JPG

Figure 40. Excitation and emission
wavelengths of a pigment found in the stony coral
Mycetophyllia. After Mazel, 1997.

Fig41.JPG

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Figure 41. The spectral signature
of this pigment is very similar to a number of pigments found
with stony corals Montastraea. After Kelmanson and Matz,
2003.

IntroPhoto.jpg

Figure 42. Green fluorescence
comes in many variations, as this photograph from LA hobbyist
Dave Botwin’s reef aquarium demonstrates.

P-516: Precursor of Pigment
581

Commercially available as EosFP.

Host: Montastrea cavernosa

  • Excitation: 506nm
  • Emission: 516nm
  • Stokes shift: 10nm
  • Reference: Labas et al., 2002
  • Comments: Relative brightness of this green form is 1.28
    (when compared to a modified form of A. victoria GFP).

Host: Pocillopora damicornis

  • Excitation: 486nm
  • Emission: 516nm
  • Stokes shift: 30nm
  • Reference: Salih et al., 2000.

Host: Lobophyllia hemprichii

  • Excitation: ~510nm
  • Emission: 516nm
  • Stokes shift: 6nm
  • Reference: Nienhaus et al., 2005
  • Comments: These researchers observed this green form
    (emission peak at 516nm) maturing to red fluorescence (peak at
    581nm) when irradiated with ‘blue’ light (actually
    violet) at ~400nm. This maturation is driven by light energy
    and not chemical oxidation. See Figure 43 for
    excitation/emission spectra.
Fig43.JPG

Figure 43. A photoconvertible
pigment found in Lobophyllia stony corals. After
Nienhaus et al., 2005.

P-517

Host: Ricordea florida

  • Excitation: Not listed
  • Emission: 517nm
  • Stokes shift: N/A
  • Reference: Mazel, 1995

Host: Montastraea annularis

  • Excitation: Not listed
  • Emission: 517nm
  • Stokes shift: N/A
  • Reference: Mazel, 1995
  • Comments: Emission has shoulders at 551nm and
    483nm.

Host: Acropora tenuis

  • Excitation: 505nm, shoulder at 465nm.
  • Emission: 517nm, 555nm and 485nm.
  • Stokes shift: 12nm
  • Reference: Papina et al., 2002
  • Comments: This A. tenuis specimen was collected in
    August 2001 at a depth of 1.5m in Okinawa, Japan. It appeared
    to the observer as brown in natural light, and fluoresced green
    under a black light. Spectral chart is that of an intact coral.
    Papina et al. noted no significant shifts of either fluorescent
    quantum yield or spectral characteristics over a pH range of
    5.0 to 8.0. See Figure 44.
Fig44.JPG

Figure 44. Acropora tenuis
specimens are not rare in coral aquaria. After Papina et al.,
2002.

P-517 variant: Precursor of
Pigment 593

Commercially available as Kikume or KikGR.

Host: Favia favus

  • Excitation: 507nm
  • Emission: 517nm
  • Stokes shift: 10nm
  • Reference: Tsutsui et al., 2005
  • Comments: Pigment 517 from Favia favus is
    photoconvertible to P-593 (green to red). Relative brightness (compared
    to an engineered GFP from
    Aequorea victoria) is 1.12. See Figure 45.
Fig45.JPG

Figure 45. The spectra of a GFP
from a stony coral in its immature state. The mature form is
red with a peak emission at 593nm. After Tsutsui et al.,
2005.

Pigment 517 variant: Precursor to
Pigment 574

Host: Ricordea florida

  • Excitation: 506nm
  • Emission: 517nm
  • Stokes shift: 11nm
  • Reference: Labas et al., 2002
  • Comments: See Figure 46.
Fig46.JPG

Figure 46. If we are to believe
the thoughts of some researchers, this
‘double-peaked’ spectrum is indicative of a pigment
in transition from green to red. This pigment was isolated from
Ricordea florida. After Labas et al., 2002.

P-518

Host: Ricordea florida

  • Excitation: Not listed
  • Emission: 518nm
  • Stokes shift: N/A
  • Reference: Mazel, 1995

Host: Acropora cytheria

  • Excitation: Not listed
  • Emission: 518nm
  • Stokes shift: Not listed
  • Reference: Hochberg et al., 2004
  • Comments: This particular Acropora cytheria specimen
    was grown at the Waikiki Aquarium under a combination of artificial light
    (metal halide lamps) supplemented with afternoon sunlight (J.C. Delbeek,
    personal communication).

Host: Acropora digitifera

  • Excitation: Not listed
  • Emission: 518nm
  • Stokes shift: Not listed
  • Reference: Hochberg et al., 2004
  • Comments: Found in an Acropora digitifera specimen on
    a shallow reef flat (depth of 0.1m; ~4”), Mayoette,
    Comorros.

Host: Family Pectiniidae

  • Excitation: 503nm
  • Emission: 518nm
  • Stokes shift: 15nm
  • Reference: Ando et al., 2004
  • Comments: This is an interesting protein – its
    fluorescence is ‘switchable.’ The green pigment is
    bleached upon exposure to intense light at ~490nm. The green
    fluorescence returns upon exposure to violet light at about
    400nm. This photoconvertible pigment (from green fluorescence
    to non-fluorescent) is commercially available as
    “Dronpa” (“Dron” being a ninja term for
    ‘vanishing’ and ‘pa’ for
    photoactivatible) and was isolated from a coral in the family
    ‘Pectiniidae’ (which includes genera Echinophyllia, Oxypora, Mycedium and Pectinia – Veron,
    1986). Relative brightness of this green form is 2.40 (when compared
    to a modified form of A. victoria GFP).

Host: Ricordea florida

  • Excitation: 508nm
  • Emission: 518nm
  • Stokes shift: 10nm
  • Reference: Labas et al., 2002

Host: Montastraea cavernosa

  • Excitation: ~505nm
  • Emission: 518nm
  • Stokes shift: ~13nm
  • Reference: Kelmanson and Matz, 2003
  • Comments: This pigment was found in a green fluorescent M. cavernosa collected
    in the Florida Keys.
Fig47.JPG

Figure 47. Spectral signatures of
P-518 isolated from Ricordea florida by Labas et al.,
2002. The excitation and emission spectra are identical to that
of P-518 described in Montastraea cavernosa by Kelmanson and
Matz (2003).

P-518 could also be an immature green form of the red
fluorescent protein Kaede (P-582), although it is difficult to
believe the pigment would not mature in shallow water as
described by Hochberg et al., 2004. This could simply be a
non-photoconvertible form of P-518.

P-519

Host: Montastraea cavernosa

  • Excitation: Not listed
  • Emission: 519nm
  • Stokes shift: N/A
  • Reference: Kelmanson and Matz, 2003
  • Comments: Pigment 519 was found in a red fluorescent M.
    cavernosa
    collected in the Florida Keys. No excitation
    wavelength is listed; however, its emission spectrum is almost
    identical to P-518.

P-520: Precursor of Pigment
580.

  • Host: Ricordea florida
  • Excitation: Not listed
  • Emission: 520nm
  • Stokes shift: N/A
  • Reference: Mazel, 1995.
  • Comments: This pigment might be the immature form of the
    ‘red’ fluorescent P-580. See below.

Host: Montastraea cavernosa

  • Excitation: 508nm, with a shoulder at 572nm
  • Emission: 520nm, with shoulder at 580nm
  • Stokes shift: 12nm and 8nm
  • Reference: Labas et al., 2002.
  • Comments: Possibly the same pigment found in Ricordea
    florida
    by Mazel (1995)?

P-520: Precursor of Pigment
611.

  • Host: Entacmaea quadricolor
  • Excitation: ~500nm
  • Emission: ~520nm
  • Stokes shift: 20nm
  • Reference: Nienhaus et al., 2003.

P-522

Host: Montastraea cavernosa

  • Excitation: Not listed
  • Emission: 522nm
  • Stokes shift: N/A
  • Reference: Kelmanson and Matz, 2003.
  • Comments: This pigment was found in a red Montastraea
    cavernosa
    collected in the Florida Keys National Marine
    Sanctuary.

Host: Anemonia sculata

  • Excitation: 511nm
  • Emission: 522nm
  • Stokes shift: 11nm
  • Reference: Wiedenmann et al., 2000
  • Comments: Note the double-peaked emission in Figure
    48.
Fig48.JPG

Figure 48. The excitation and
emission suggest photoconversion is possible in this pigment.
After Wiedenmann et al., 2000.

P-530

Host: Porites astreoides

  • Excitation: ~500nm
  • Emission: 530nm
  • Stokes shift: ~30nm
  • Reference: Mazel et al., 2003
  • Comments: See Figure 49 for excitation and emission
    spectra.
Fig49.JPG

Figure 49. Spectral qualities of a
pigment found in the Caribbean coral Porites astreoides.
After Mazel et al., 2003.

Yellow-Green
Pigments

P-538

Host: Zoanthus 2.

  • Excitation: 528nm
  • Emission: 494nm and 538nm
  • Stokes shift: 10nm
  • Reference: Matz et al., 1999; Labas et al., 2002
  • Comments: P-538 was isolated by Matz et al. (1999)
    from a Zoanthus species and found in combination with
    another fluorescent pigment (P-506). Fluorescent
    Quantum Yield and Relative Brightness are fairly low –
    0.42 and 0.38, respectively. See data of Yanushevich et al.
    (2002) in Figure
    50.
Fig50.JPG

Figure 50. After Yanushevich et
al., 2002. Excitation and emission spectra are practically
identical to those presented by Matz et al.,
1999.

Fig51.JPG

Figure 51. Compare the spectral
qualities of this pigment to that in Figure 50 – they are
almost identical. After Matz et al.,
1999.

P-550

Host: Porites murrayensis

  • Excitation: 530nm
  • Emission: 550nm
  • Stokes shift: 20nm
  • Reference: Dove et al., 2001
  • Comments: This coral was purple when viewed in natural light
    due to the presence of a non-fluorescent protein. Maximum host
    tissue/zooxanthellae absorbance is at 576nm (data not
    shown).

P-557

Host: Agaricia sp.

  • Excitation: Not listed
  • Emission: 557nm
  • Stokes shift: N/A
  • Reference: Mazel, 1995
  • Comments: Emission also has shoulders at 600nm and 545nm.
    Reports of this particular pigment are practically
    non-existent, with Mazel’s reports being the only ones of
    which I am aware. See Figure 52. (Mazel reports yellow Agaricia are
    common in Bonaire – personal communication).
Fig52.JPG

Figure 52. A rather unique
yellowish fluorescent protein found it in the Caribbean stony
coral Agaricia. After Mazel, 1995.

P-561 (Kusabira-Orange)

Host: Fungia concinna

  • Excitation: 548nm
  • Emission: 565nm
  • Stokes shift: 17nm
  • Reference: Karasawa et al., 2004.
  • Comments: Commercially available from MBL International
    under the trade name “Kusabira-Orange”. Wild type
    P-561 has a fluorescent quantum yield of 0.45, and is not pH
    sensitive (pKa <5.0). The Japanese name for Fungia is
    “Kusabira-ishi.”
    See Figure 53.
Fig53.JPG

Figure 53. A true orange
fluorescent protein found in the popular ‘mushroom’
stony coral (Fungia). After Karasawa et al., 2004.

P-562 (or asCP-562)

Host: Anemonia sculata

  • Excitation: 559nm
  • Emission: 562nm (immature form)
  • Stokes shift: 52nm
  • Reference: Wiedenmann et al., 2002
  • Comments: This yellow green pigment is found in the anemone
    (Anemonia sculata) and is technically fluorescent
    although laboratory instruments are needed to detect it. Under
    certain conditions, this pigment can transform from
    yellow-green to red with a very weak emission maximum at
    611nm.

P-565

Host: Agaricia humilis

  • Excitation: 490nm
  • Emission: 565nm
  • Stokes shift: 75nm
  • Reference: Mazel et al., 2003.
  • Comments: See Figure 53.

Host: Cerianthus sp.

  • Excitation: 548nm
  • Emission: 565nm
  • Stokes shift: 17nm
  • Reference: Ip et al., 2004.
  • Comments: This pigment is apparently spectrally different
    from the P-565 found in Agaricia stony corals.
Fig54.JPG

Figure 54. A yellowish
pigment from the stony coral Agaricia. After Mazel et
al., 2003.

An Early GFP Description

In homage to Siro Kawaguti, one of the first researchers of
coral coloration, Table 3 describes some of the properties of
fluorescent pigments found in Pacific corals. Though much of
Kawaguti’s early works were completed and published in
the late 1930’s and 40’s, his ideas, for the most
part, have withstood the test of time. His equipment was not as
sophisticated as that of today and did not offer great
precision, yet his descriptions are remarkable. His works offer
perspectives on GFPs and the varieties of coral hosts and
complement later research. Note that his work deals with mostly
emission wavelengths (as seen in the ‘1st
Band’ and ‘2nd Band’ columns)
while absorbance (‘Max. Abs. 1’ and ‘2’
columns is rarely described. See Table
5.

Table 5. Kawaguti’s early observations of Pacific corals’ fluorescence.
Green Fluorescence
Coral1st Abs. Band2nd Abs. BandMaxima Abs.1Maxima Abs. 2
Fungia actiniformis498-521475-484512480
Montipora verrucosa505-514***
Porites (arboreal)515-525495**
Fungia repunda504-517476-483**
Montipora ramosa498-511486504-507*
Tridacophyllia lacinata488-511467-471**
Pachyseris rugosa498-509***
Caulastrea tumida498-510***
Hydnophora microconos498-511***
Acropora hyacynthus498-512474**
Acropora haimei498-513471**
Pocillopora acuta498-514***
Favia sp.500-507***
Mycedium elephantotus491-505***
Herpetolitha limax493-508***
Lobophyllia hemprichii494-514***
Lobophyllia corymbosa501-514473**
Psammocora contigua482-498463**
Euphyllia glabrescens489-500***
Galaxea fascicularis488-501***
Pocillopora eydouxi473-489***
Plerogyra sinuosa488-507***
Echinopora lamellosa491-503***
Goniopora sp.485-501458-466**
Acropora arcuata494-503***
Cyphastrea mocrophthalma482-499462-466**
Tridacophyllia lacinata493-504***

Next time, we’ll look at more fluorescent pigments and
discuss how light can cause coloration shifts in at least some
pigments.

Interested parties can correspond with the author at
RiddleLabs@aol.com.

References

Please see Part 1 (Volume V, Issue IX) for a full listing of references
used in this
series.

Category:
  Advanced Aquarist
Dana Riddle
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 Dana Riddle

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