ArticlePublisher preview available

Synchrotron X-ray absorption spectroscopy of melanosomes in vertebrates and cephalopods: Implications for the affinity of Tullimonstrum

Proceedings of the Royal Society B

October 2019
286(1913)

DOI:10.1098/rspb.2019.1649

Authors:

Tim Astrop

University College Cork

Samuel M. Webb

SLAC National Accelerator Laboratory, Stanford University

Shosuke Ito

Fujita Health University

Show all 6 authorsHide

Screening pigments are essential for vision in animals. Vertebrates use melanins bound in melanosomes as screening pigments, whereas cephalopods are assumed to use ommochromes. Preserved eye melanosomes in the controversial fossil Tullimonstrum (Mazon Creek, IL, USA) are partitioned by size and/or shape into distinct layers. These layers resemble tissue-specific melano-some populations considered unique to the vertebrate eye. Here, we show that extant cephalopod eyes also show tissue-specific size-and/or shape-specific partitioning of melanosomes; these differ from vertebrate melanosomes in the relative abundance of trace metals and in the binding environment of copper. Chemical signatures of melanosomes in the eyes of Tullimonstrum more closely resemble those of modern cephalopods than those of vertebrates, suggesting that an invertebrate affinity for Tullimonstrum is plausible. Melano-some chemistry may thus provide insights into the phylogenetic affinities of enigmatic fossils where melanosome size and/or shape are equivocal.

A preview of this full-text is provided by The Royal Society.

Learn more

Content available from Proceedings of the Royal Society B

This content is subject to copyright.

royalsocietypublishing.org/journal/rspb

Research

Cite this article: Rogers CS, Astrop TI, Webb

SM, Ito S, Wakamatsu K, McNamara ME. 2019

Synchrotron X-ray absorption spectroscopy of

melanosomes in vertebrates and cephalopods:

implications for the affinity of Tullimonstrum.

Proc. R. Soc. B 286: 20191649.

http://dx.doi.org/10.1098/rspb.2019.1649

Received: 12 July 2019

Accepted: 27 September 2019

Subject Category:

Palaeobiology

Subject Areas:

palaeontology

Keywords:

fossil soft tissues, Konservat-Lagerstätten,

melanosomes, trace metals

Authors for correspondence:

Christopher S. Rogers

e-mail: christopher.rogers@ucc.ie

Maria E. McNamara

e-mail: maria.mcnamara@ucc.ie

Electronic supplementary material is available

online at https://doi.org/10.6084/m9.figshare.

c.4691789.

Synchrotron X-ray absorption spectroscopy

of melanosomes in vertebrates and

cephalopods: implications for the affinity

of Tullimonstrum

Christopher S. Rogers1, Timothy I. Astrop1, Samuel M. Webb2, Shosuke Ito3,

Kazumasa Wakamatsu3and Maria E. McNamara1

School of Biological, Earth and Environmental Sciences, University College Cork, Distillery Fields, North Mall,

Cork T23 TK30, Republic of Ireland

Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo

Park, CA 94025, USA

Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Aichi 470-1192, Japan

CSR, 0000-0001-7928-6280; MEM, 0000-0003-0968-4624

Screening pigments are essential for vision in animals. Vertebrates use

melanins bound in melanosomes as screening pigments, whereas cephalopods

are assumed to use ommochromes. Preserved eye melanosomes in the contro-

versial fossil Tullimonstrum (Mazon Creek, IL, USA) are partitioned by size

and/or shape into distinct layers. These layers resemble tissue-specific melano-

some populations considered unique to the vertebrate eye. Here, we show that

extant cephalopod eyes also show tissue-specific size- and/or shape-specific

partitioning of melanosomes; these differ from vertebrate melanosomes in

the relative abundance of trace metals and in the binding environment of

copper. Chemical signatures of melanosomes in the eyes of Tullimonstrum

more closely resemble those of modern cephalopods than those of vertebrates,

suggesting that an invertebrate affinity for Tullimonstrum is plausible. Melano-

some chemistry may thus provide insights into the phylogenetic affinities of

enigmatic fossils where melanosome size and/or shape are equivocal.

1. Introduction

Screening pigments are an essential component of visual systems in animals as

they absorb errant light, thus allowing directional photoreception and the protec-

tion of photoreceptors from ultraviolet radiation [1]. Invertebrate screening

pigments include ommochromes, pterines and, less frequently, melanin [2]. In con-

trast, the primary screening pigment in vertebrates is melanin, occurring as

melanosomes (membrane-bound organelles) in the iris, choroid, retinal pigmented

epithelium (RPE) [3] and sclera [4] (figure 1). RPE melanosomes include spherical

and elongate forms that are partitioned spatially [5]. In bright incident light,

elongate melanosomes migrate to the apical processes of RPE cells, thus protecting

photosensitive pigments in photoreceptor cells from bleaching. Intriguingly, the

eyes of the enigmatic taxon Tullimonstrum gregarium (Carboniferous, Mazon

Creek, IL, USA) also exhibit successive layers of melanosomes of different geome-

tries. This feature was interpreted as evidence of a vertebrate affinity based on a

review of melanosome distribution and morphology in extant animals [2].

Whether invertebrate eye melanosomes are organized into successive tissue

layers as in vertebrates is, however, unknown. Resolving this requires systematic

investigation of screening pigments in invertebrate eyes. Cephalopods are an

ideal test case because they, like vertebrates, possess a complex camera-style eye

with multiple pigmentedtissue layers [6] and are known to produce melanosomes

(in the ink sac [7,8]). We systematically characterized the anatomical location and

chemistry of pigmented tissues, and the geometry of pigmentgranules, in the eyes

of the common octopus (Octopus vulgaris), European squid (Loligo vulgaris),

A new non-destructive method to decipher the origin of organic matter in fossils using Raman spectroscopy

Article

Full-text available

Aug 2024

Ancient biomolecules provide a unique perspective on the past but are underutilized in paleontology because of challenges in interpreting the chemistry of fossils. Most organically preserved soft tissues in fossils have been altered by thermal maturation during the fossilization process, obscuring original chemistry. Here, we use a comprehensive program of thermal maturation experiments on soft tissues from diverse extant organisms to systematically test whether thermally altered biosignatures can be discriminated using Raman spectroscopy. All experimentally matured samples show chemical signatures that are superficially similar. Comparative analysis of Raman spectra following peak deconvolution, however, reveals strong tissue-specific signals. Application of this approach to fossils from the Bolca (49 Ma) and Libros (10 Ma) Konservat-Lagerstätten successfully discriminates fossil vertebrate soft tissue from that of fossil plants. Critically, our data confirm that a robust interrogation of Raman spectra coupled with multivariate analysis is a powerful tool to shed light on the taxonomic origins of thermally matured fossil soft tissues.

Forged soft tissues revealed in the oldest fossil reptile from the early Permian of the Alps

Article

Full-text available

Feb 2024
Palaeontology

Tridentinosaurus antiquusrepresents one of theoldest fossil reptiles and one of the very few skeletal specimenswith evidence of soft tissue preservation from the Cisuralian(Early Permian) of the Italian Alps. The preservation andappearance of the fossil have puzzled palaeontologists fordecades and its taphonomy and phylogenetic position haveremained unresolved. We reanalysedT. antiquususing ultravio-let light (UV), 3D surface modelling, scanning electron micros-copy coupled with energy dispersive spectroscopy (SEM-EDS),micro x-ray diffraction (μ-XRD), Raman and attenuated totalreflectance Fourier transformed infrared (ATR-FTIR)spectroscopy to determine the origin of the body outline andtest whether this represents the remains of organically preservedsoft tissues which in turn could reveal important anatomicaldetails about this enigmatic protorosaur. The results reveal,however, that the material forming the body outline is not fos-silized soft tissues but a manufactured pigment indicating thatthe body outline is a forgery. Our discovery poses new ques-tions about the validity of this enigmatic taxon

Mazon Creek Fossils Brought to You by Coal,Concretions, and Collectors

Article

Oct 2023

The late Carboniferous (Middle Pennsylvanian, ∼307 mya) Mazon Creek Lagerstätte found in Northern Illinois, USA is unique for its exceptional biotic diversity as well as the human endeavors, both professional and avocational, that brought vast numbers of fossils and new species to science. In 1997, the Mazon Creek Fossil Beds, exposed along the Mazon River near Benson Road, Morris Illinois became a National Historic Landmark. The fossils are preserved in siderite (iron carbonate, FeCO 3 ) concretions within the lower 3-8 meters of the Francis Creek Shale Member of the Carbondale Formation, and often retain outlines of original soft tissues. The Mazon Creek biota includes over 465 animal and 350 plant species representing more than 100 orders, which is attributed to the preservation of organisms from multiple habitats and the large number of specimens collected. That phenomenon was made possible by coal extraction bringing concretions to the surface and highly motivated amateur collectors pursuing them. Some of the formerly mined areas continue to draw collectors and are preserved as part of the Mazonia-Braidwood State Fish and Wildlife Area. The fossils, fossil collectors and collection sites are a significant part of our cultural and scientific geoheritage.

Recent Advances in Characterization of Melanin Pigments in Biological Samples

Article

Full-text available

May 2023
INT J MOL SCI

The melanin pigments eumelanin (EM) and pheomelanin (PM), which are dark brown to black and yellow to reddish-brown, respectively, are widely found among vertebrates. They are produced in melanocytes in the epidermis, hair follicles, the choroid, the iris, the inner ear, and other tissues. The diversity of colors in animals is mainly caused by the quantity and quality of their melanin, such as by the ratios of EM versus PM. We have developed micro-analytical methods to simultaneously measure EM and PM and used these to study the biochemical and genetic fundamentals of pigmentation. The photoreactivity of melanin has become a major focus of research because of the postulated relevance of EM and PM for the risk of UVA-induced melanoma. Our biochemical methods have found application in many clinical studies on genetic conditions associated with alterations in pigmentation. Recently, besides chemical degradative methods, other methods have been developed for the characterization of melanin, and these are also discussed here.

The Tully monster remains an evolutionary enigma

Article

Jan 2025
Geol Today

Simon Braddy

The affinities of the Tully monster ( Tullimonstrum gregarium ), from the late Carboniferous Mazon Creek Lagerstätte (~309 Ma) of Illinois, have been debated since its discovery. Tullimonstrum is up to ~35 cm long with a long proboscis ending in pincers and an elongate tapering body with caudal dorsal and ventral fins. This iconic evolutionary enigma or ‘weird wonder’ has been suggested to relate to arthropods, various ‘worms’, tunicates, conodonts, lancelets, vetulicolians and even vertebrates, but it may be a mollusc (Caenogastropoda) such as a pterotracheid (heteropod) pelagic gastropod, similar to Pterotrachea coronata (the ‘sea elephant’).

Development of the Use of Synchrotron Radiation for the Study of Cultural Heritage Materials

Chapter

Dec 2024

Synchrotron-X-ray fluorescence provides elemental signatures for diverse coloration mechanisms in fossil insects

Preprint

Full-text available

Jun 2024

Numerous fossil insects exhibit color patterning, but the coloration mechanisms responsible are largely unknown. Here, we use non-destructive SRS-XRF to characterize the spatial distributions of elements in the cuticles of 78 extant and 15 fossil insects collected from six independent fossil localities. LDA reveals a strong taxonomic signal whereby members of the same order or family show similar chemical signatures. Within genera, cuticle regions containing different pigments have distinct chemistries, i.e. broad taxonomic trends in chemistry are overprinted by a strong pigment-specific signal. The chemistry of fossil insect cuticles differs to that of extant analogues and is controlled by both taxonomy and depositional context, indicating diagenetic overprinting of original cuticle chemistry. Despite this, cuticle regions with different visual tones in fossils contain specific suites of elements, suggesting that original color influences the preserved chemical signal.

Melanosome Origins, Diversity and Functional Relevance Across Animals

Chapter

Apr 2023

Liliana D'Alba

Melanosomes are important organelles melanin is produced stored and mobilized throughout animal tissues. Melanins confer unique properties to these organelles, including strong light absorption, antioxidant capabilities and mechanical stiffness. Melanosomes perform many essential functions across the animal tree. Several recent discoveries about the chemistry and melanosome ontogeny have emerged, but a broad comparative framework still is needed. This chapter reviews the hierarchical structure, development, functions and evolution of melanosomes. It focuses on variation in melanosome morphology, elucidation of melanosome chemistry as a whole and the relationships between them with the functions they perform. An attempt is made to integrate the knowledge gathered so far about the correlation between the formation of amyloid protein scaffolds and melanogenesis across animal groups to generate hypotheses on their evolution. From this perspective, melanosomes (membrane-bound) were most likely present in animals early since the origins of the immune system and at the origin of organelles. The remaining knowledge gaps are highlighted throughout the chapter and a review of the most recent advances in analytical techniques used to elucidate the physicochemical properties of individual melanosomes describes potential ways to advance our understanding of these still, enigmatic organelles.

Biotechnological Production of Melanins with Recombinant Microorganisms

Chapter

Full-text available

Apr 2023

Most organisms can synthesize a variety of natural polymers called melanins. These substances serve protective roles against physical and chemical stressors. These products result from the enzyme-catalyzed oxidation of phenolic and indolic substrates which polymerize to produce melanins such as eumelanin, pheomelanin, pyomelanin, and allomelanins. Tyrosinase and laccase protein families are primarily involved in the production of melanin. The pharmaceutical, cosmetic, optical, and electrical industries all use melanins as functional polymeric materials. The development of biotechnological processes to produce melanins is becoming an attractive alternative compared to their extraction from plant or animal matter, in which they are only present at low concentrations. Numerous types of bacteria are naturally capable of producing melanin. Using genetic engineering techniques, it is currently possible to overexpress in microorganisms the genes for melanin-producing enzymes. These advancements have allowed increasing the productivity of melanogenic organisms and have enabled the creation of novel recombinant microbial strains that can synthesize a variety of melanins. Furthermore, strains capable of completely synthesizing melanins from basic carbon sources on a gram-scale basis have been developed by metabolic engineering of microbial hosts through altering pathways relevant to the availability of melanogenic precursors. The most recent discoveries in the development of recombinant melanin-producing strains and manufacturing methods are compiled and reviewed in this chapter.

The Role of Melanin in Fungal Disease

Chapter

Apr 2023

Many fungi produce melanins, which can play critical roles in virulence and pathogenicity. In fungal pathogenic species, melanin confers protection against host immune defense mechanisms that involve both chemical and physical antimicrobial defense strategies. In this piece, we review the different types of melanin produced by fungi, their structure and localization in the fungal cell, and how melanin interacts with the host to aid the fungus during infection and persistence.

Tissue-specific geometry and chemistry of modern and fossilized melanosomes reveal internal anatomy of extinct vertebrates

Article

Full-text available

Aug 2019

Significance Recent reports of nonintegumentary melanosomes in fossils hint at functions for melanin beyond color production, but the biology and evolution of internal melanins are poorly understood. Our results show that internal melanosomes are widespread in diverse fossil and modern vertebrates and have tissue-specific geometries and metal chemistries. Tissue-specific chemical signatures can persist in fossils despite some diagenetic overprint, allowing the reconstruction of internal soft-tissue anatomy in fossil vertebrates, and suggest that links between melanin and metal regulation have deep evolutionary origins in vertebrates.

Fossil insect eyes shed light on trilobite optics and the arthropod pigment screen

Article

Full-text available

Sep 2019
NATURE

Fossilized eyes permit inferences of the visual capacity of extinct arthropods1–3. However, structural and/or chemical modifications as a result of taphonomic and diagenetic processes can alter the original features, thereby necessitating comparisons with modern species. Here we report the detailed molecular composition and microanatomy of the eyes of 54-million-year-old crane-flies, which together provide a proxy for the interpretation of optical systems in some other ancient arthropods. These well-preserved visual organs comprise calcified corneal lenses that are separated by intervening spaces containing eumelanin pigment. We also show that eumelanin is present in the facet walls of living crane-flies, in which it forms the outermost ommatidial pigment shield in compound eyes incorporating a chitinous cornea. To our knowledge, this is the first record of melanic screening pigments in arthropods, and reveals a fossilization mode in insect eyes that involves a decay-resistant biochrome coupled with early diagenetic mineralization of the ommatidial lenses. The demonstrable secondary calcification of lens cuticle that was initially chitinous has implications for the proposed calcitic corneas of trilobites, which we posit are artefacts of preservation rather than a product of in vivo biomineralization4–7. Although trilobite eyes might have been partly mineralized for mechanical strength, a (more likely) organic composition would have enhanced function via gradient-index optics and increased control of lens shape.

The ‘Tully Monster’ is not a vertebrate: characters, convergence and taphonomy in Palaeozoic problematic animals

Article

Full-text available

Feb 2017
Palaeontology

The affinity of Tullimonstrum gregarium, a pincer-mouthed, soft bodied bilaterian, has been subject to debate since its recovery from Carboniferous coal deposits at Mazon Creek, Illinois. After decades of impasse focused on mollusc, arthropod and annelid attributes, two recent, yet conflicting, high-profile studies concluded that the ‘Tully Monster’ is a vertebrate, a relative of lampreys or jawed fishes. Here, we find that structures described as supporting vertebrate, and particularly crown vertebrate, affinity face significant challenges from biological, functional and taphonomic perspectives. Problems with comparator choice, interpretation of taphonomic processes at Mazon Creek and estimation of convergence within the bilaterian tree may have misled these recent studies, leading to conclusions which do not accommodate current understanding of the vertebrate record. For example, the absence of taphonomically-expected synapomorphies in Tullimonstrum (e.g. otic capsules, body pigment) calls into question vertebrate identity and implies that convergence or deeper origins are responsible for vertebrate-like traits. Further, phylogenetic placement within vertebrates is only made possible by the constraints of a chordate-only dataset with limited outgroups and use of selective characters. Long-discussed alternative placements among molluscs (e.g. heteropod gastropods), arthropods (e.g. anomalocarids) or elsewhere within non-vertebrate deuterostomes are more congruent. Indeed, many of these lineages independently evolved vertebrate-like traits, including complex eyes and ‘teeth’. Thus, given the totality of evidence, Tullimonstrum should be excluded from the vertebrate crown. Potential assignments for aberrant bilaterians, common throughout the Palaeozoic fossil record, need to be considered in light of the number and likelihood of required exceptions to established schemes.

Melanin fate in the human epidermis: a re-assessment of how best to detect and analyze histologically

Article

Full-text available

Mar 2016
EXP DERMATOL

Melanin is the predominant pigment responsible for skin colour, and is synthesized by the melanocyte in the basal layer of the epidermis and then transferred to surrounding keratinocytes. Despite its optical properties, melanin is barely detectable in unstained sections of human skin. However, identification and localization of melanin is of importance for the study of skin pigmentation in health and disease. Current methods for the histologic quantification of melanin are suboptimal, and are associated with significant risk of misinterpretation. The aim of this study was to re-assess the existing literature, and to develop a more effective histological method of melanin quantification in human skin. Moreover, we confirm that Warthin-Starry (WS) stain provides a much more sensitive and more specific melanin detection method than the common-place Fontana-Masson (FM) stain. For example, WS staining sensitivity allowed the visualization of melanin even in very pale Caucasian skin that was missed by FM or Von Kossa (VK) stains. From our re-assessment of the histology-related literature we conclude that so-called 'melanin dust' is most likely an artefact of discoloration due to non-specific silver deposition in the stratum corneum. Unlike FM and VK, WS was not associated with this non-specific stratum corneum darkening, misinterpreted previously as 'degraded' or so-called 'dust' melanin. Finally, WS melanin particle counts were largely similar to manual counts by transmission electron microscopy, in contrast to both FM and VK. Together these findings allow us to propose a new histology/Image J-informed method for the accurate and precise quantification of epidermal melanin in skin. This article is protected by copyright. All rights reserved.

Chemical, experimental, and morphological evidence for diagenetically altered melanin in exceptionally preserved fossils

Article

Full-text available

Sep 2015

Significance Melanin is a widespread pigment that provides black to reddish brown hues to organisms. Recent evidence has shown that melanin is retained in exceptionally preserved fossils, including feathered dinosaurs, allowing the reconstruction of ancient color patterns. However, little is known about the chemical preservation of melanin or its distribution in the fossil record. Here, we show that melanin is preserved in a number of soft-bodied fossils, but its burial under high pressure and temperature for millions of years alters its original chemistry. The widespread occurrence of melanin substantiates the applicability of reconstructing aspects of original color patterns and allows us to dismiss the alternative suggestion that these structures are microbial in origin.

Acid hydrolysis reveals a low but constant level of pheomelanin in human black to brown hair

Article

Nov 2017

We previously reported a constant ratio of the benzothiazole-pheomelanin marker thiazole-2,4,5-tricarboxylic acid (TTCA) to the eumelanin marker pyrrole-2,3,5-tricaboxylic acid (PTCA) in eumelanic, black human hair. A constant level (20-25%) of benzothiazole-type pheomelanin was recently demonstrated in human skin with varying concentrations of melanin. Therefore, in this study, we aimed to investigate the origin of pheomelanin markers in black to brown human hair by developing a method to remove protein components from hair by heating with 6 M HCl at 110°C for 16 h. For comparison, synthetic melanins were prepared by oxidizing mixtures of varying ratios of dopa and cysteine with tyrosinase. Hair melanins and synthetic melanins were subjected to acid hydrolysis followed by alkaline H2O2 oxidation. The results show that the hydrolysis leads to decarboxylation of the 5,6-dihydroxyindole-2-carboxylic acid moiety in eumelanin and the benzothiazole moiety in pheomelanin and that eumelanic human hair contains 11 to 17% benzothiazole-type pheomelanin. This article is protected by copyright. All rights reserved.

The eyes of Tullimonstrum reveal a vertebrate affinity

Article

Apr 2016

Tullimonstrum gregarium is an iconic soft-bodied fossil from the Carboniferous Mazon Creek Lagerstätte (Illinois, USA). Despite a large number of specimens and distinct anatomy, various analyses over the past five decades have failed to determine the phylogenetic affinities of the 'Tully monster', and although it has been allied to such disparate phyla as the Mollusca, Annelida or Chordata, it remains enigmatic. The nature and phylogenetic affinities of Tullimonstrum have defied confident systematic placement because none of its preserved anatomy provides unequivocal evidence of homology, without which comparative analysis fails. Here we show that the eyes of Tullimonstrum possess ultrastructural details indicating homology with vertebrate eyes. Anatomical analysis using scanning electron microscopy reveals that the eyes of Tullimonstrum preserve a retina defined by a thick sheet comprising distinct layers of spheroidal and cylindrical melanosomes. Time-of-flight secondary ion mass spectrometry and multivariate statistics provide further evidence that these microbodies are melanosomes. A range of animals have melanin in their eyes, but the possession of melanosomes of two distinct morphologies arranged in layers, forming retinal pigment epithelium, is a synapomorphy of vertebrates. Our analysis indicates that in addition to evidence of colour patterning, ecology and thermoregulation, fossil melanosomes can also carry a phylogenetic signal. Identification in Tullimonstrum of spheroidal and cylindrical melanosomes forming the remains of retinal pigment epithelium indicates that it is a vertebrate; considering its body parts in this new light suggests it was an anatomically unusual member of total group Vertebrata.

A REAPPRAISAL OF TULLIMONSTRUM GREGARIUM

Chapter

Dec 1979

Merrill W. Foster

Tullimonstrum gregarium from the Essex fauna of Illinois is believed to be somewhat less bizarre in morphology than has been suggested by previous studies. The segmentation in fossil specimens appears to be primarily a post-mortem feature related to the break-down of body musculature. The apparent claw at the end of the proboscis is interpreted as either a buccal mass with the buccal cavity exposed or a highly modified bifurcate buccal mass. The stylets or teeth in the buccal mass are somewhat curved and bear a groove on one side. They resemble lateral and marginal radular teeth in molluscs. They may represent parts of a typical radula that was largely lost in fossilization or all of a highly specialized radula without many teeth.

Physical and chemical characterization of iris and chorold melanosomes isolated from newborn and mature cows

Article

May 2005
PHOTOCHEM PHOTOBIOL

Bovine iris and choroid melanosomes at two ages (< 1 week and > 2 years) were examined by inductively coupled plasma mass spectrometry (ICP-MS), elemental analysis, infrared spectrometry (IR) and X-ray photoelectron spectrometry (XPS). When iris and choroid melanosomes at the same age were compared, the quantification of metal elements by ICP-MS revealed that choroid melanosomes had a higher binding capacity for the carboxylate-binding metal ions (e.g. Na+, K+, Mg2+, Ca2+ and Zn2+). Elemental analysis showed a higher O:N ratio in choroid melanosomes. Both observations suggested that choroid melanosomes have a higher content of carboxylate-containing monomer than iris melanosomes. IR spectrometric analysis showed a red shift (similar to 8 cm(-1)) of the absorption peak of aromatic C=C, C=N and C=O at similar to 1630 cm(-1) in the IR spectrum of iris melanosomes relative to choroid melanosomes. Increased conjugation in the molecular structure of the pigment is proposed to contribute to this peak shift. It is also notable that although the elemental analysis showed different C, N and 0 contents in the two types of melanosomes, XPS showed almost the same elemental compositions on the surface of two types of iris and choroid melanosomes studied. When the melanosomes from the same tissues at different ages were compared, ICP-MS analysis suggested that the number of carboxylate groups in the melanosomes decreased with age. Both elemental analysis and XPS showed that CA ratio decreased with age, which was proposed to be due to both a decrease in carboxylate groups in mature samples and to the fissure of phenol rings caused by age-associated oxidation. Such age-related oxidative damage diminishes conjugation and is manifested by blue shifts of absorption peaks for aromatic double bonds in the IR spectra of mature melanosomes. XPS analysis showed that the ratio of C-O: C=O decreased with age. These tissue-related and age-related chemical differences between samples affected the optic density and metal binding properties of melanosomes, which are believed to be closely associated with the biological functions of melanins.

The Tully monster and a new approach to analyzing problematica

Article

Jan 1991

B.S. Beall

Reinvestigation of the Upper Carboniferous problematic Tully monster, Tullimonstrum gregarium, from Illinois, USA, emphasizes that 1) an unequivocal interpretation of the morphology of a fossil often may be unattainable, 2) a combined cladistic-phenetic approach using a phylogenetic computer program permits identifying sister group relationships and testing hypotheses of affinities; and 3) this approach permits classification in a repeatable and testable manner. When alternative interpretations of 21 characters of Tullimonstrum were compared with character states in 13 other OTU's plus an outgroup in preliminary analyses using a phylogenetic computer program, most of the resulting cladograms indicate close affinities with the Conodonta; almost as many corroborate Foster's (1979) hypothesis of a molluscan affinity with Tullimonstrum. -from Author

Synchrotron X-ray absorption spectroscopy of melanosomes in vertebrates and cephalopods: Implications for the affinity of Tullimonstrum

Abstract

Recommended publications

Tissue-specific geometry and chemistry of modern and fossilized melanosomes reveal internal anatomy...

Synchrotron x‐ray fluorescence analysis reveals diagenetic alteration of fossil melanosome trace met...

Maturation experiments reveal bias in the chemistry of fossil melanosomes

Hierarchical biota-level and taxonomic controls on the chemistry of fossil melanosomes revealed usin...