Rosa Rubicondior: Refuting Creationism - Biofluorescent fish 112 Million Years Before 'Creation Week'.

Tuesday, 24 June 2025

Refuting Creationism - Biofluorescent fish 112 Million Years Before 'Creation Week'.

Creationists bunker - Evidence keep out! No Science Allowed!

Studies Reveal Fish Biofluorescence Dates Back 112 Million Years | AMNH

I sometimes imagine creationists hiding inside a bunker with no windows, completely cut off from the reality outside, where a torrential rainstorm is underway. From within their sealed refuge, they declare to themselves—and to the world outside—that there is no evidence of rain, simply because they can’t see any.

Their only source of information is a handful of picture books depicting a tropical paradise where it never rains, so they believe everything beyond their bunker must be warm and sunny—just as the picture books describe. Anyone who tells them otherwise, or tries to show them a different picture, must be lying to trick them.

How else can creationists be so insulated from the reality of the deluge of scientific evidence in the real world?

That slightly tortured analogy is by way of introducing another couple of scientific papers concerning the evolutionary divergence of the phenomenon of biofluorescence. Unlike bioluminescence—where light is produced by a physiological process using ATP and functions in total darkness—biofluorescence involves the absorption of ambient light, which is then re-emitted at a different frequency. Specialised proteins absorb this light energy, become unstable in their excited state, and return to their ground state by releasing photons—hence biofluorescence functions in low-light conditions.

Fish in particular, but also sea turtles and corals, use these glowing patterns as signals—for attracting mates, confusing predators, and more. According to two newly published papers by a team led by researchers at the American Museum of Natural History (AMNH), this phenomenon first emerged around 112 million years ago—once again, firmly within Earth’s long pre–'Creation Week' history. Since then, biofluorescence appears to have evolved independently up to 100 times, a clear indication of its adaptive benefits in dimly lit ocean environments.

Beyond the evidence for biological activity in a time creationists claim the Earth didn’t even exist, there's another uncomfortable detail for them: the researchers declare that to understand the pattern of bioluminescence in nature, “...we need to understand the underlying evolutionary story...” Not something a creationist, labouring under the delusion that biologists are abandoning the theory of evolution in favour of creationism, would want to read.

Their findings are published open access in Nature Communications and PLOS ONE.

What is currently known about biofluorescence, its distribution and function? Biofluorescence is an optical phenomenon in which organisms absorb light, typically high-energy blue or ultraviolet (UV) light, and re-emit it at a longer, lower-energy wavelength, usually in the green, orange, or red spectrum. Unlike bioluminescence, which involves the production of light through chemical reactions (often ATP-driven), biofluorescence depends entirely on ambient light and does not generate light in complete darkness.

Current Understanding of Biofluorescence

Mechanism

Biofluorescence is driven by fluorescent proteins (e.g. green fluorescent proteins or GFPs), which absorb light and re-emit it at a different wavelength.
These proteins often contain chromophores that become excited by short-wavelength light (blue/UV), then release photons at a longer wavelength.
This phenomenon is passive: it needs external light to be visible.

Evolution and Distribution

Phylogenetic breadth: Biofluorescence has been observed across a wide range of taxa, including:

Marine organisms: Fish, sharks, corals, anemones, sea turtles, jellyfish, and crustaceans.
Terrestrial organisms: Some amphibians, reptiles, and birds (notably under UV light).
Fungi: Certain species exhibit UV-induced fluorescence.
Arthropods: Spiders and scorpions often fluoresce under UV light.

Independent origins: Recent research, including a 2025 study from AMNH, suggests that biofluorescence has evolved independently over 100 times, especially in marine environments.

Environmental Distribution

Most prevalent in marine environments, especially in:

Mesophotic and twilight zones (depths of 30–150 metres), where blue light penetrates but other wavelengths are filtered out.
Tropical coral reefs, where blue light is abundant and water clarity is high.

Less common but still found in terrestrial species, often visible only under artificial UV light in lab or field studies.

Functions

Biofluorescence appears to serve various ecological and evolutionary functions, though in many cases its role is still being explored. Proposed or confirmed functions include:

Communication

Many marine animals use fluorescent patterns for intraspecific signalling - to attract mates, recognise species or individuals, or communicate status.
These patterns are often invisible to the human eye but detectable to species with visual adaptations, such as yellow intraocular filters that enhance contrast.

Camouflage and Crypsis

In some species, fluorescence helps to blend into the background light environment, particularly in blue-dominated underwater settings.

Predation and Defence

Some species may use fluorescence to confuse predators, by disrupting outlines or creating misleading colour signals.
Conversely, some predators may use it to detect prey, especially those with fluorescence-enhancing vision.

UV Protection

There’s speculation that fluorescence might play a photoprotective role, helping organisms dissipate harmful UV radiation, though evidence is mixed.

Mimicry and Deception

There are hypotheses that biofluorescence may be involved in mimicry systems, for example, where one species mimics another's signals to exploit their behaviour.

Current Research Trends

Genetic basis: Studies continue to investigate the genes responsible for fluorescent protein synthesis and regulation.
Evolutionary mapping: Phylogenetic studies are increasingly pinpointing when and where fluorescence evolved in different lineages.
Sensory ecology: Researchers are exploring how animals perceive fluorescence and how this influences behaviour and evolution.
Biomedical applications: Fluorescent proteins from marine organisms, particularly GFP from jellyfish, have revolutionised molecular biology, enabling techniques like live-cell imaging.

Key References

Nature Communications (2025): Fluorescent protein evolution in marine fish
PLOS ONE (2025): Patterns of marine biofluorescence across taxa
AMNH Blog: Lay summary of recent biofluorescence findings

It is also explained in lay terms in an AMNH news blog.

Studies Reveal Fish Biofluorescence Dates Back 112 Million Years
Two new studies led by Museum researchers shapes our knowledge about the origins and scope of fish biofluorescence—the flashy phenomenon in which light is absorbed, transformed, and emitted as a different color.
The work, published recently in Nature Communications and PLOS One, finds that fish biofluorescence is ancient, first occurring at least 112 million years ago, and has evolved independently more than 100 times since, particularly among fish that live on coral reefs. The two studies also reveal that fish biofluorescence involves a larger assortment of colors than previously reported.

Researchers have known for a while that biofluorescence is quite widespread in marine animals, from sea turtles to corals, and especially among fishes, but to really get to the root of why and how these species use this unique adaptation—whether for camouflage, predation, or reproduction—we need to understand the underlying evolutionary story as well as the scope of biofluorescence as it currently exists.

Emily Carr, lead author
Richard Gilder Graduate School American Museum of Natural History, New York, NY, USA.

Carr and collaborators, including her Ph.D. advisor, Museum Curator John Sparks, surveyed all known biofluorescent teleosts—a type of bony fish that make up the largest group of vertebrates living today. They ended up with a list of 459 species, including 48 species that were previously unknown to be biofluorescent.

Their work suggests that this unique phenomenon first arose in eels at least 112 million years ago and has evolved more than 100 times. The evolution rate is especially high in fish species that live on coral reefs—10 times the rate of non-reef species. The increase coincides with the recovery of coral reefs following the Cretaceous-Paleogene (K-Pg) extinction about 66 million years ago.

These correlations suggest that the emergence of modern coral reefs could have facilitated the diversification of fluorescence in reef-associated teleost fishes.

Emily Carr.

The researchers used a specialized photography setup with ultraviolet and blue excitation lights and emission filters to look at the wavelengths of light emitted by fishes collected over the last decade and a half on Museum expeditions to the Solomon Islands, Greenland, and Thailand. Although the specimens in the study were previously observed fluorescing, the full range of their biofluorescent emissions was unknown.

The new work reveals far more diversity in colors emitted than had previously been reported. Some teleost families exhibit at least six distinct fluorescent emission peaks, which correspond with wavelengths across multiple colors.

The remarkable variation we observed across a wide array of these fluorescent fishes could mean that these animals use incredibly diverse and elaborate signaling systems based on species-specific fluorescent emission patterns.

John Sparks, supervising author.
Richard Gilder Graduate School
American Museum of Natural History, New York, NY, USA.

Technical details are reported in two papers; the first in Nature Communications, provides evidence of multiple instances of the evolution of biofluorescence:

Abstract
Biofluorescence, the absorption of high-energy light and its reemission at lower energy wavelengths, is widespread across vertebrate and invertebrate lineages, especially fishes. New observations over the past decade have significantly increased our understanding of the diversity and multifunctionality of fluorescence in fish lineages. In this study, we present a comprehensive account of all known biofluorescent teleosts and estimate the timing and frequency of the evolution of biofluorescence across this diverse group. We show that biofluorescence evolved numerous times in marine teleosts and is estimated to date back ~112 mya in Anguilliformes (true eels). Of the 459 known biofluorescent teleosts reported in this study, the majority are associated with coral reefs. We find that reef-associated species evolve biofluorescence at 10x the rate of non-reef species. Our results suggest that the chromatic and biotic conditions of coral reefs could have provided an ideal environment to facilitate the evolution and diversification of biofluorescence in teleost fishes.

Introduction
Biofluorescence results from the absorption of higher-energy light and its reemission at longer, lower-energy wavelengths by living organisms¹. It is a widespread phenomenon across the tree of life and occurs in most major clades of vertebrates^{1,2,3,4,5,6,7,8,9}. Biofluorescence is found in both terrestrial and marine organisms, although these environments have vastly different lighting conditions. Terrestrial ecosystems are brightly lit by sunlight, which contains a wide spectrum of wavelengths spanning the visible light spectrum. Alternatively, vast portions of the photic ocean are characterized by a relatively monochromatic, blue-shifted environment¹⁰. As sunlight hits and enters oceanic waters, longer wavelengths (yellow, orange, red) are rapidly absorbed, resulting in a limited bandwidth of blue light (470–480 nm) by around 150 m depth (frequently much shallower depending on water clarity)¹⁰. Thus, the ability to absorb shorter wavelength ambient blue light at depth and reemit it as longer wavelengths through the use of fluorescent compounds may be advantageous to marine organisms to increase visibility and contrast amidst the more monochromatic blue environment of the ocean1.

Biofluorescence is phylogenetically pervasive, yet it remains unknown how much of this potential visual signal is biologically relevant and serves a functional role, versus an anatomical byproduct (e.g., enamel)^4,11. For example, carnivorous pitcher plants (Nepenthaceae and Sarraceniaceae) fluoresce along the lip of the pitcher, which attracts insect prey^2,12. Sexual dimorphism in green biofluorescence and ultraviolet (UV) reflectance is thought to aid in the mating rituals of jumping spiders (Salticidae)³. In marine fishes, where fluorescent emissions mainly occur in the green to red portions of the visible spectrum, biofluorescence has been implicated in camouflage, communication, species identification, mating, and prey attraction^1,13,14,15. The Pacific spiny lumpsucker (Eumicrotremus orbis) exhibits sexually dichromatic fluorescent emission colors from the body that may enhance mate identification, whereas fluorescence of the pelvic disc in both males and females is thought to be utilized for signaling¹³. Biofluorescence is also notably prevalent in coral reef ecosystems. Scleractinian corals exhibit red and green fluorescence, which may increase contrast at depth, provide photoprotection for symbionts, and provide visual cues for other reef organisms^16,17,18,19. Some reef fishes may utilize biofluorescent corals and marine algae for camouflage. Scorpionfishes (Scorpaenidae) and threadfin breams (Nemipteridae) have been observed residing on or near backgrounds with similar fluorescent emission wavelengths to their bodies¹. Other reef fishes may be using biofluorescence for intraspecific signaling, including closely related species of reef lizardfishes (Synodontidae) that appear nearly identical under white light, but exhibit significant variation in fluorescent patterning¹. The potential multifunctional roles of biofluorescence may be linked to the increased rates of diversification of coral reef fishes^20,21,22.

These potential visual functions of biofluorescence all require that fluorescent emissions lie within the spectral sensitivity of relevant signal-receivers: conspecifics, predators, and/or prey¹. Shallow water reef fishes often have relatively good color vision with two or three visual pigments, allowing them to navigate the chromatically complex ecosystem of coral reefs²³. Although most reef fishes are sensitive to shorter wavelengths (blue), some species (e.g., Pomacentridae and Labridae) exhibit long-wavelength sensitivity as high as 600 nm (red)²⁴. In addition, members of many families of marine fishes have been reported to possess yellow intraocular lenses that function as long-pass filters and can facilitate the visualization of longer fluorescent wavelengths^1,25. Behavioral experiments support fluorescent recognition for sex identification in the fairy wrasse (Cirrhilabrus solorensis)²⁶. Whereas, direct testing of the visual system in the swell shark (Cephaloscyllium ventriosum) and chain catshark (Scyliorhinus rotifer) revealed that fluorescence functions to increase luminosity contrast with the background environment and between skin patches at depth¹⁴. However, our knowledge of the visual capabilities of biofluorescent fishes is extremely limited²³, as is our understanding of fluorescent molecules. Green fluorescent proteins (GFP), similar to the GFP that was first isolated from the hydrozoan Aequorea victoria²⁷, have only been isolated and characterized in three species of Anguilliformes (true eels)^28,29,30. Smaller fluorescent metabolites were found to be responsible for the green fluorescent emissions in elasmobranchs14, whereas no red fluorescent molecules have yet been isolated from fishes despite the prevalence of red fluorescence across Teleostei.

Given the various proposed functions of biofluorescence and the visual capabilities of marine fishes, further research into its evolution and diversification is crucial. Previous investigations of the phylogenetic distribution of biofluorescence in teleosts found that the phenomenon is both phylogenetically widespread and phenotypically variable across the assemblage^1,31,32. However, no recent work has accounted for and incorporated information from the huge increase in biofluorescent teleost diversity that has been documented within the past decade.

Herein we investigate the early evolution of biofluorescence in Teleostei, determine when the phenomenon first evolved in this group, reconstruct the evolutionary patterns of fluorescent emission colors in various lineages, and report on the number of times the phenomenon is known to have independently evolved across this huge and remarkably diverse (>30,000 species) vertebrate assemblage. We also investigate whether the rise and global expansion of modern coral reefs contributed to the incredible diversity of biofluorescence we observe across modern teleost lineages.

Fig. 1: Trimmed Rabosky et al.⁴⁵ phylogeny of Teleostei showing ancestral state reconstructions of biofluorescence (absence/presence).

Major clades where biofluorescence is widespread (A–F) and the oldest reconstructed node where biofluorescence is present (A) are labeled and indicated with an additional outline circle: A) Anguilliformes, B) Labriformes, C) Perciformes, D) Syngnathiformes, E) Pleuronectiformes, and F) Blenniiformes.

Photographs: NOAA, Vincent Hyland/Wild Derrynane, John Sparks, Mason Thurman.

Carr, E.M., Martin, R.P., Thurman, M.A. et al.
Repeated and widespread evolution of biofluorescence in marine fishes. Nat Commun 16, 4826 (2025). https://doi.org/10.1038/s41467-025-59843-7

Copyright: © 2025 The authors.
Published by Springer Nature Ltd. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

The second paper, in PLOS ONE, presents the evidence for the exceptional variation in biofluorescence emission spectra:

Abstract
Biofluorescence is a phylogenetically widespread phenomenon among marine fishes, yet the phenotypic diversity in fluorescent emission wavelengths (e.g., green, red) remains poorly studied across the broad diversity of marine teleosts. In this study we investigate the fluorescent emission spectra from a diverse array of 18 teleost families and record fluorescent emission peaks over multiple body regions. Our results show that fluorescent emission spectra are remarkably diverse among teleost families, as well as within genera. Fluorescent emissions also vary across different body regions within some individuals. We show that members of the families Gobiidae, Oxudercidae, and Bothidae exhibit at least six distinct, non-overlapping fluorescent emission peaks. Nine of the 18 families examined in this study were found to have at least four distinct and non-overlapping fluorescent emission peaks. Further, we find that several families exhibit multiple discrete emission peaks for a single fluorescent color (i.e., wavelength range), including multiple distinct peaks within the green and red portions of the spectrum. The interplay between different fluorescent emission wavelengths and notable variation in the distribution of fluorescence on the body could allow for a wide array of fluorescent patterns to be produced by an individual or among closely related species. Our results reveal far more diversity in both fluorescent emission wavelengths (colors) and in the distribution of fluorescent molecules across the body than had previously been reported in the literature. We characterize this novel variation in biofluorescent emissions across an array of teleost families and discuss the potential implications of this exceptional phenotypic variability.

Introduction
Biofluorescence results from the absorption of high energy, shorter wavelength light by an organism and its reemission at longer, lower energy wavelengths [1.1]. Although present in numerous invertebrate and vertebrate lineages [1.1–7.1], fluorescence is particularly phylogenetically widespread and phenotypically variable in marine fishes, where fluorescent emissions are generally reported within the red and green portions of the visible spectrum [1.1,8.1,9.1]. Several recent studies have documented this widespread presence of biofluorescence across ray-finned fishes [1.1,8.1,10.1–12.1], but relatively few of these report fluorescent emission spectra [1.1,8.1,12.1–14.1]. Anthes et al. [14.1] documented variation in red fluorescent emissions within several teleost families, finding three general groups of emission peaks: near red, deep red, and far red. However, their analysis excluded all emission peaks below 580 nm (i.e., green-yellow) [14.1]. No study to date has focused on investigating variation in fluorescent emission peaks across the full range of fluorescent wavelengths observed in teleosts [1.1,13.1]. This highlights a large gap in knowledge, especially considering prior studies have reported the presence of multiple fluorescent colors (e.g., green and red) even within an individual [1.1,9.1,13.1].

Fishes have been hypothesized to use biofluorescence for functions such as intraspecific signaling, visual enhancement, and camouflage [1.1,10.1,11.1,15.1]. However, these potential functions require that signal receivers can visualize fluorescent emissions, either as a color signal or as enhanced contrast (e.g., against a background or substrate) [1.1]. Most fluorescent teleosts are cryptically patterned reef fishes [1.1] whose eyes are generally most sensitive to shorter wavelengths of blue, green, and yellow [16.1,17.1]. Blue and green wavelengths are the most common at depth, as the attenuation of sunlight through water rapidly removes longer (orange-red) wavelengths. This creates a monochromatic blue environment of 470–480 nm by around 150 m depth in clear oceanic waters [18.1]. One of the potential benefits of fluorescence in marine environments is that it restores longer wavelengths (green-red) in these habitats where only shorter blue wavelengths can penetrate [1.1,11.1]. Interestingly, many reef fishes (e.g., Pomacentridae, Gobiidae, Labridae) possess long wavelength sensitivity (LWS) opsins in their eyes, that may allow them to visualize orange and red wavelengths [16.1,19.1,20.1].

Although the potential function of biofluorescence remains unknown in most lineages of marine fishes, recent studies hypothesize that it could serve as a visual aid. Bright green fluorescence was shown to significantly increase contrast at depth in catsharks, making it easier for conspecifics to see each other in these dimly lit environments [11.1]. Red fluorescence in the eyes of certain reef fishes or on the fins in cryptically-patterned species is hypothesized to provide a visual aid and may function in intraspecific signaling [12.1,14.1]. In addition, many reef lineages possess yellow intraocular filters in their lenses or corneas [21.1]. These filters can function as long-pass filters, which may enhance the perception of longer wavelength fluorescent emissions within a primarily blue ambient environment [1.1]. Although further studies are needed to determine and compare the diversity of visual spectral ranges broadly among teleosts, in general, many reef fishes are capable of visualizing the green through red portions of the spectrum common in fluorescent emissions [16.1,19.1,20.1].

In this study, we compare emission spectra within 18 biofluorescent families across the phylogeny of Teleostei [1.1,9.1]. We document significant variation among families and genera, and over body anatomy within individual species. The objectives of this study are to: 1) record detailed fluorescence emission spectra across a wide array of teleost families that have been shown to exhibit biofluorescence; 2) determine and characterize how fluorescence emission spectra vary within a family, genus, and species; 3) analyze variation in fluorescence emission wavelengths by anatomical region within an individual; and 4) discuss the implications of variation in fluorescent emission spectra (i.e., the presence of several distinct emission peaks within a lineage or species). This study expands our understanding of the variation of biofluorescence in teleosts and highlights the importance of measuring fluorescent emission spectra as it relates to taxonomy, fluorescent proteins, and potential visual functions.

Fig 2. Representative images of biofluorescent teleosts examined in this study.
A) Eviota prasites (Gobiidae), B) Trimma fangi (Gobiidae), C) Enneapterygius niger (Tripterygiidae), D) Helcogramma striata (Tripterygiidae), E) Ecsenius axelrodi (Blenniidae), F) Engyprosopon mozambiqense (Bothidae), G) Japonolaeops dentatus* (Bothidae), H) Cynoglossus microlepis (Cynoglossidae), I) Gymnothorax zonipectis (Muraenidae), J) Cheilinus oxycephalus (Labridae), K) Pseudocheilinus evanidus (Labridae), L) Saurida micropectoralis*,‡ (Synodontidae), M) Upeneus sundaicus* (Mullidae), N) Taenianotus triacanthus (Scorpaenidae), O) Sebastapistes fowleri (Scorpaenidae), P) Aulostomus chinensis (Aulostomidae), Q) Kaupichthys diodontus (Chlopsidae).

*Images of the same specimen without (top) and with (bottom) a 561 nm long-pass filter to block emitted green fluorescence.
‡Saurida micropectoralis (L) is shown in dorsal and lateral views for green fluorescence.
Scale bars (white lines) shown in each image are 1 cm.

Carr EM, Thurman MA, Martin RP, Sparks TS, Sparks JS (2025)
Marine fishes exhibit exceptional variation in biofluorescent emission spectra.
PLoS One 20(6): e0316789. https://doi.org/10.1371/journal.pone.0316789

Copyright: © 2025 The authors.
Published by PLOS. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

These two new papers on the evolution of biofluorescence in marine fish present yet another awkward hurdle for creationists—one they're likely to ignore, dismiss, or misrepresent. The first problem is temporal: the evidence shows that biofluorescence originated at least 112 million years ago, deep in the Cretaceous period. That's more than 100 million years before the supposed 'Creation Week' of young-Earth creationist dogma. If life was only created 6,000 to 10,000 years ago, then marine animals with complex signalling systems—reliant on quantum-level photon re-emission—should not be turning up in a fossil-calibrated phylogeny stretching back over 100 million years.

Second, the findings demonstrate that biofluorescence has evolved independently in multiple lineages—up to 100 times across different fish groups—strongly suggesting an adaptive function that was honed by natural selection. This repeated, convergent evolution is precisely what evolutionary theory predicts and explains well, but what creationism finds difficult to account for without resorting to ad hoc reasoning or vague appeals to 'design'.

Finally, and perhaps most damningly for creationist narratives that like to claim evolution is a failing theory, the researchers themselves explicitly state that to understand patterns of biofluorescence in nature, we must understand their *evolutionary history*. This is a blunt rejection of the idea that biologists are abandoning evolutionary theory. On the contrary, it's yet another example of evolution doing what it always does: providing a coherent, testable framework for making sense of nature's complexity—without invoking magic, mystery, or myth.

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