Publisher Summary This chapter assembles data, which contribute to a physiological understanding of this pathway in insects, to appraise the role of ommochromes in insect life, and the relation of tryptophan metabolism to insect development. Tryptophan is an outstanding amino acid. It has the highest molecular weight of all amino acids occurring in proteins, and comprises, in its indolyl moiety, a system capable of donating electrons and; therefore, liable to form complexes with a range of other molecules. Molecular interactions have been observed between tryptophan and nucleic acids, and a variety of other molecules of biological importance. Organisms have taken advantage of the potentialities of this molecule and have transformed it into a wide range of biologically active compounds. In these, either the indole ring or its benzene nucleus are retained, the latter also being recast into the pyridine ring. In insects, a major product of tryptophan degradation is a group of 10 to 15 pigments, the ommochromes. Being brownish-yellow, bright red or dark violet-purple, these pigments produce the deep tinge of insect eyes and contribute to the brilliant coloration of many species.

The Tryptophan → Ommochrome Pathway in Insects

6 – Bile Pigments: Bilatrienes and 5,15-Biladienes

I. General.- 1 Introduction.- 2 Basis and Significance of Colour in Molecules.- 2.1 Physical Basis of Colour.- 2.2 The Electronic Basis of Colour.- 2.3 Other Optical Properties of Biochromes.- 2.3.1 Fluorescence and Phosphorescence.- 2.3.2 Dichromatism or Dichroism.- 2.3.3 Other Relevant Properties.- 2.4 Conclusion.- II. The Nature and Distribution of Zoochromes.- 3 The Chemical Classes of Zoochrome.- 3.1 Chromoproteins and Other Conjugates.- 3.2 Carotenoids.- 3.2.1 Properties.- 3.3 Fuscins.- 3.4 Chroman Biochromes.- 3.4.1 Flavonoids.- 3.5 Ternary Quinones.- 3.5.1 Properties.- 3.6 Metalloproteins.- 3.6.1 Copper Proteins.- 3.6.2 Iron Proteins.- 3.7 Pyrrolic Zoochromes.- 3.7.1 Properties.- 3.8 Indolic Zoochromes.- 3.8.1 Indigotins.- 3.8.2 Other Indolic Oligomeric Chromes.- 3.8.3 Indolic Melanins.- 3.8.4 Other Zoochromes of the Indolic Melanin Pathway.- 3.9 Ommochromes (Phenoxazones) and Related Bio-chromes.- 3.9.1 Properties.- 3.9.2 Other Zoochromes of the Kynurenine Pathway.- 3.10 Other N-heterocyclic Zoochromes: Purines, Pterins and Flavins (Isoalloxazines).- 3.10.1 Purines.- 3.10.2 Pterins.- 3.10.3 Flavins (Isoalloxazines).- 3.11 Other Zoochromes.- 3.12 Zoochromes in Relation to pH.- 3.13 Conclusion.- 4 The Taxonomic Distribution of Zoochromes.- 4.1 Distribution between Animals and Plants.- 4.2 Distribution between the Phyla and Classes of Animals.- 4.2.1 Conclusion.- 4.3 Distribution in the More Obsure Phyla and Classes.- 4.3.1 Conclusion.- 4.4 Distribution between Lower Taxonomic Units.- 4.5 Conclusion.- 5 Distribution and State of Zoochromes in the Body.- 5.1 Distribution of Zoochromes between Organs, Tissues and Fluids of the Body.- 5.1.1-5.1.16 Individual Organs, etc.- 5.1.17 Conclusion.- 5.2 The Location of Chromes within Organs and Tissues.- 5.2.1 Conclusion.- 5.3 The Location and State of Zoochromes within Cells.- 5.3.1 The Chromasome.- 5.3.2 Protozoan Chromes.- 5.3.3 State of Zoochromes in Storage and Scavenging Cells.- 5.3.4 Conclusion.- 5.4 Biochromes and the Solid State.- 5.5 The Stability of Zoochromes.- 5.6 General Conclusion.- III. Physiological Functions of Zoochromes.- 6 The Functions of Integumental Zoochromes.- 6.1 Integumental Colour-Change.- 6.1.1 Chromogenic Change.- 6.1.2 Chromomotor Colour-Change.- 6.1.3 The Mechanism of Chromomotor and Chromogenic Responses.- 6.1.3.1 Primary Responses.- 6.1.3.2 Secondary Responses.- 6.1.3.3 The Response-Mechanism as a Whole.- 6.2 Other Functions of Integumental Chromes.- 6.2.1 Protection against Radiation.- 6.2.2 Mechanical Protection.- 6.2.3 Chemical Defence.- 6.2.4 Thermal Regulation.- 6.3 Conclusion.- 7 Zoochromes and Sensory Perception.- 7.1 Light Perception.- 7.2 Colour Vision.- 7.3 Other Zoochromes of the Retina.- 7.4 Simple Photoperceptors.- 7.5 Zoochromes of Other Perceptor Organs.- 7.6 Conclusion.- IV. Biochemical Functions of Zoochromes.- 8 Oxidation-Reduction Functions of Zoochromes.- 8.1 The Biochromes of the Standard Respiratory Pathways.- 8.1.1 The Molecular Basis of the Action of Respiratory Chromoproteins.- 8.2 Other Redox Reactions Catalysed by Chromoprotein Enzymes.- 8.3 Redox Functions of Other Zoochromes.- 8.4 Photochemical Redox Catalysis by Zoochromes.- 8.5 Biochromes and Bioluminescence.- 8.6 Redox Zoochromes that are Vitamins.- 8.7 Conclusion.- 9 Zoochromes that Transport Oxygen.- 9.1 Physiological Properties of Oxygen-transport-Zoo-chromes.- 9.1.1 Haemoglobins.- 9.1.2 Haemerythrins.- 9.1.3 Haemocyanins.- 9.2 The Molecular Basis of O2-Transport.- 9.2.1 Haemoglobins.- 9.2.2 Haemerythrins.- 9.2.3 Haemocyanins.- 9.2.4 Comparison between the Classes of Oxygen-carriers.- 9.3 Other Metalloproteins and Oxygen-transport.- 9.4 Conclusion.- 10 Zoochromes in Other Aspects of Metabolism.- 10.1 Zoochromes and Digestive Fluids.- 10.2 Zoochromes as End-products of Metabolism.- 10.3 Conclusion.- 11 Pathological States Involving Zoochromes.- 11.1 The Destruction of Zoochromes by Light.- 11.2 Photodynamic Actions of Biochromes.- 11.3 Qualitative Chromopathies.- 11.4 Deficiency and Excess of Dietary Chromes.- 11.5 Deficiency and Excess of Endogenous Chromes.- 11.6 Parasitism and Zoochromes.- 11.7 Conclusion.- V. The Significance of Zoochromes for Reproduction and Development.- 12 Zoochromes in Reproduction and Development.- 12.1 Reproduction.- 12.1.1 Chromes of the Reproductive Organs.- 12.1.2 Integumental Chromes.- 12.1.3 Pubertal and Seasonal Changes.- 12.1.4 Reproductive Metabolism.- 12.1.5 Control of Reproduction.- 12.1.6 Conclusion.- 12.2 Zoochromes in the Ontogenesis of Animals.- 12.2.1 Effects of the Classes of Biochrome on Embryogenesis.- 12.2.2 Pigment Formation by the Embryo.- 12.2.3 Chromogenic Changes during Metamorphosis.- 12.2.4 Conclusion.- VI. Evidence from Chromogenesis in the Individual.- 13 The Evidence from Chromogenic Pathways.- 13.1 Known Chromogenic Pathways.- 13.1.1 Carotenoids.- 13.1.2 Chromones and Flavonoids.- 13.1.3 Ternary Quinones.- 13.1.4 Porphyrins.- 13.1.5 Indolic Melanins.- 13.1.6 Ommochromes.- 13.1.7 Purines, Pterins and Isoalloxazines.- 13.2 Adaptive Features of Chromogenic Pathways.- 13.2.1 The Primality of Chromogenic Pathways.- 13.2.2 Sophistication of Chromogenic Pathways.- 13.2.3 Economy in Chromogenic Pathways.- 13.2.4 Chromogenic Pathways in the Different Taxa.- 13.3 Interrelationships between Chromogenic Pathways.- 13.3.1 General Similarities between Chromogenic Pathways.- 13.3.2 Paths Beginning in a Common Precursor.- 13.3.3 Connections between Pathways.- 13.3.4 Convergence between Pathways.- 13.3.5 Interaction between Members of Different Chromogenic Paths.- 13.3.6 Biochromes Acting as Coenzymes in Chromogenic Paths.- 13.4 Conclusion.- 14 Evidence from the Control of the Supply of Biochromes.- 14.1 Uptake and Handling of Exogenous Chromes.- 14.1.1 Carotenoids.- 14.1.2 Other Exogenous Zoochromes.- 14.1.3 Chromes Acquired Both Exogenously and Endogenously.- 14.1.4 Conclusion.- 14.2 The Control of Chromogenesis.- 14.2.1 Feedback Control of Chromogenesis.- 14.2.2 The Systemic Control of Haem-Synthesis.- 14.2.3 The Control of Phase-coloration in Insects.- 14.2.4 The Control of Exogenous Integumental Chromes.- 14.2.5 The Indirectness of Chromogenic Controls.- 14.2.6 The Chain of Intermediation in Chromogenic Controls.- 14.2.7 Conclusion.- 15 The Development of Integumental Colour-Patterns.- 16 The Genetic Basis of Chromogenesis.- 16.1 Genetic Colour-Polymorphism.- 16.2 General Properties of Chromogenic Mutants.- 16.3 The Alleles at Individual Loci.- 16.4 Alleles at Chromoprotein Loci.- 16.5 The Number and Types of Chromogenic Loci.- 16.6 Interactions between Chromogenic Loci.- 16.7 Chromogenes and Taxonomy.- 16.8 Conclusion.- VII. Evolutionary Evidence and General Assessment.- 17 Zoochromes and Evolution.- 17.1 Fossil Zoochromes.- 17.2 Prebiological Evolution of Organic Chromes.- 17.3 Chromes and the First Discrete Organisms.- 17.4 The Evolution of Chromes in Animals.- 17.5 Conclusion.- 18 General Assessment.- 18.1 Outstanding Adaptations of Zoochromes.- 18.2 Chromatological Problems.- 18.2.1 Problems Concerning Specific Classes of Inte-gumental Chrome.- 18.2.2 Problems Concerning Chromes Other than those of the Integument.- 18.3 Unidentified Zoochromes.- 18.4 Conclusion.- Subject and Systematic Index.

The Significance of Zoochromes

4 – carotenoids in fish feeds

The isopods Asellus intermzedius, Lirceus garmani, and L. lineatus were studied to document further the occurrence of altered pigmentation in these hosts infected with species of Acanthocephalus. Specimens of A. intermedius from central Illinois, L. garmani from northwestern Arkansas, and L. lineatus from northwestern Ohio revealed differences in normal integumental pigmentation related to species, sex, reproductive state, and size. Integument of males and females of the three species was found to be more lightly pigmented when specimens harbored male, female, or multiple infections with acanthocephalans. Comparisons of light transmission through wholemounts of respiratory opercula of A. interinedius dem- onstrated that there was no significant difference in pigmentation among infection types. Regression analyses indicated (1) that the normnnal relationship between isopod length and pigmentation had been disrupted by acanthocephalan infections; (2) that a developmental relationship existed between isopod (length) and acanthocephalan (volume); (3) that there was not a direct relationship between acanthocephalan size and altered pigmentation, as might be expected for a gradual "depigmentation" process; and (4) that eye size was unaffected by parasitism. On the basis of these findings, the terminol- ogy, "pigmentation dystrophy," is proposed as more appropriate than the previously used terms, "non- pigmentation," 'depigmentation," and "color dichromatism."

Effects of acanthocephalans on pigmentation of freshwater isopods

The integumental pigments of some isopod crustacea

The tissue-pigments of some fresh-water leeches

Distribution of protoporphyrin, ferrihaem and indoles in the body-wall of Lumbricus terrestris L.

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The integumental pigments of some isopod crustacea

The tissue-pigments of some fresh-water leeches

Distribution of protoporphyrin, ferrihaem and indoles in the body-wall of Lumbricus terrestris L.