University of Bath PHD A biomimetic approach to adaptive camouflage: The function of iridophore and leucophore cells found in the bright white tissue regions of Sepia officinalis Parfitt, A. R. Award date: 2004 Awarding institution: University of Bath Link to publication Alternative formats If you require this document in an alternative format, please contact: [email protected] General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Download date: 08. Oct. 2021 A B io m im e t ic A pp r o a c h to A d a pt iv e Ca m o u f l a g e The function of iridophore and leucophore cells found in the bright white tissue regions of Sepia officinalis Submitted by A. R. Parfitt for the degree o f PhD Department of Mechanical Engineering University of Bath 2004 COPYRIGHT Attention is drawn to the fact that copyright of this thesis rests with its author. This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that its copyright rests with its author and that no quotations from the thesis and no information derived from it may be published without prior written consent of the author. UMI Number: U207134 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. Dissertation Publishing UMI U207134 Published by ProQuest LLC 2014. Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code. ProQuest LLC 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106-1346 <] 6 5 " " 1 -,o“ ; 5 ... PkA>,.......... *<v 4 v• J- «V» v »■ V* * ,• UNIVERSITY OF BATH LIBRARY AUTHOR ARPARFITT YEAR SUBMITTED 2004 TITLE A BIOMIMETIC APPROACH TO ADAPTIVE CAMOUFLAGE Attention is drawn to the fact that the copyright of this thesis rests with its author. This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that the copyright rests with its author and that no quotation from the thesis and no information derived from it may be published without the prior written consent of the author. This thesis may be made available for consultation within the University Library and may be photocopied or lent to other libraries for the purpose of consultation. A b s t r a c t This investigation focuses on the ultrastructure and function of (bright) white tissue regions found in the common cuttlefish, Sepia officinalis. It illustrates that iridophore cells are orientated in a random manner, within the white regions, and explains how this indiscriminate arrangement may produce structural colours o f a low iridescence. Iridescence is also reduced by the presence of leucophore cells. These cells possess Mie light scattering elements, which are responsible for the bright white appearance o f the tissue. The direction and area of scatter is presented for a range of wavelengths. Iridophore and leucophore cell morphology is transformed by physiological quantities of the neurotransmitter acetylcholine. These ultrastructural changes are described, and the advantages to camouflage and communication are considered. Mechanisms employed by the cuttlefish to utilise natural light for camouflage purposes are mimicked in man-made materials to create a number o f colour-changing plastics. T a b l e of C o n t e n t s Page: A b stra c t................................................................................................................... ii List of Tables and Figures........................................................................ vi Acknowledgements ............................................................................................ ix Part 1 - Background and Introduction G e n e r a l I ntroduction ................................................................................. 1 M il it a r y v e h ic l e c a m o u f l a g e ............................................................ 2 I ntroduction T o C e p h a l o p o d s ......................................................... 4 Sepia officinalis.................................................................................................. 6 Introduction .......................................................................................................... 6 C hromatophore Or g a n s : A S u m m a r y ......................................... 8 Part 2 - Method M a t e r ia l s A nd M e t h o d s ............................................................................. 11 W e lfa r e of E xperimental A n i m a l s .............................................. 11 T r a n s p o r t Of L ive S p e c i m e n s .............................................................. 11 C are of L ive S p e c im e n s and A q u a r iu m C o n d it io n s .. 12 A n a e s t h e s i a ............................................................................................................... 13 A naesthetising P r o c e d u r e ..................................................................... 13 P r e p a r a t io n of the In t e g u m e n t ....................................................... 14 C h e m ic a l F ix a t io n Of T he In t e g u m e n t F or L ight M i c r o s c o p y ................................................................................................................. 15 C h e m ic a l F ix a t io n Of T he In t e g u m e n t F or E l e c t r o n M i c r o s c o p y .................................................................................... 15 A ffects Of T he N eurotransmitter A cetylcholine ( A C h ) .................................................................................................................................. 18 Preliminary Observations...................................................................... 18 ACh affects on ultrastructure............................................................ 18 C ryofixation .......................................................................................................... 19 Cryofixation Method.................................................................................... 20 Freeze-substitution Method ................................................................. 20 S p e c im e n Se c t i o n i n g .................................................................................... 21 Os m o l a r i t y ............................................................................................................ 23 S t e r e o l o g y ............................................................................................................ 23 P olarization ....................................................................................................... 24 Part 3 - Light Reflecting Cells I ntroduction t o W h it e S k in C o m p o n e n t s ...................... 25 R e s u l t s : W h it e S k in C o m p o n e n t s ........................................... 29 D i s c u s s i o n : B r ig h t W h it e S k in C o m p o n e n t s 34 I ntroduction to D e r m a l I r id o p h o r e C e l l s 36 Ir id o s o m a l P l a t e l e t s and C y t o p l a s m ic S p a c e s ... 36 R e f r a c t iv e In d e x ......................................................................................... 37 iii Ir id o s o m a l P l a t e l e t C o m p o s i t i o n ........................................... 37 Ir id o s o m a l P l a t e l e t D istribution ......................................... Ir id o s o m a l P l a t e l e t Or i e n t a t i o n ........................................... 40 1) M u l t i -L a y er Interference .................................................... 40 2) D if f r a c t io n G r a t i n g s ................................................................... 41 D e v e l o p m e n t of Ir id o p h o r e C e l l s ........................................... 42 A ctive Ir id o p h o r e C e l l s ..................................................................... 43 P o la r ise d L ig h t R e f l e c t io n and P e r c e p t io n 43 R e s u l t s : D e r m a l I r id o p h o r e C e l l s ...................................... 45 Iridosomal platelets................................................................................. 64 Summary of iridosomal platelets and their size 74 Ir id o p h o r e C ell Or i e n t a t i o n ....................................................... 74 D is c u s s i o n : D e r m a l I r i d o p h o r e C e l l s ............................. 78 M o r p h o l o g y ....................................................................................................... 78 Iridosomal platelet composition ................................................ 79 Cytoplasmic channels............................................................................. 80 Intrairidosomal spaces.......................................................................... 83 Opt ic a l M e c h a n i s m s ................................................................................. 84 Hypothesis for random orientation ........................................... 88 I ntroduction T o C e p h a l o p o d L e u c o p h o r e C e l l s ..