Cell Tiss. Res. 163, 411-413 (1975) - 9 by Springer-Verlag 1975
Short Communication
The Reality of Arthropod Cuticular Laminae John E. Dalingwater* Department of Zoology, The University, Manchester, England
Summary. Examination of etched pyramids of decapod crustacean cuticles with the scanning electron microscope indicates that laminae are continuous around the angles of the pyramids. This observation is in direct contrast to the result expected on Bouligand's (1965, 1971) hypothesis and suggests that laminae may be real structures. Key words: Cuticle- L a m i n a e - A r t h r o p o d - Scanning electron microscopy. Introduction
Bouligand's (1965, 1971) view of the laminae of arthropod cuticles as artefacts resulting from the sectioning of a helicoidal array of flat sheets of fibres still retains its influence, although recently Dennell (1974), Mutvei (1974) and Dalingwater (1975) have presented evidence which casts serious doubts on the validity of Bouligand's theory. The continuing popularity of the Bouligand model perhaps lies in the elegant simplicity with which it explains the apparently bewildering structural complexity that arthropod cuticles present when they are viewed in angled sections or breaks at high magnifications. Yet Bouligand (1972) has had to adapt his first conception of the twisted model to account for some aspects of this morphological and developmental complexity, so that to some extent his views can be reconciled with a low angle Drach system (Bouligand's Fig. 32d, 1972). Despite these modifications, Bouligand retained his conviction that laminae are artefacts. However, a simple procedure can be employed to dispute this aspect of the Bouligand model and is described below.
Material and Methods Pyramids of cuticle from the chelae of the decapod crustaceans Homarus gammarus (L), Carcinus maenas (L.) and Cancer pagurus L. were fashioned by cutting out square blocks of cuticle with a diamond wheel and shaping them with fine carborundum powder on glass plates. The pyramids Send offprint requests to: Dr. J.E. Dalingwater, Department of Zoology, The University, Manche-
ster M 13 9PL, England. * I would like to thank Professor R. Dennell for helpful discussions and the Department of Textile Technology, UMIST, for SEM facilities.
412
J.E. Dalingwater
Fig. 1 A - D . Scanning electron micrographs of a fashioned pyramid of the cuticle of Cancer pagurus L. (A) Viewed from above; continuity of laminae around the angles is just apparent, x 160. (B) Detail of one of the angles of the pyramid in which continuity of laminae (narrow dark bands) is clearly apparent. Inverted signal, x 800. (C) and (D). An angle of the pyramid. Normal and inverted signal. The laminae (normal: light bands; inverted: dark bands) are continuous around the angle, x 260
were then etched with 1% hydrochloric acid for five minutes, and air-dried in dust-free conditions before being mounted on stubs, gold-coated, and examined with a Cambridge "Stereoscan" scanning electron microscope.
Observations and Discussion I n t h e B o u l i g a n d m o d e l (1965, 1971) t h e a p p a r e n t l a m i n a e a r e n o t i n r e g i s t e r a r o u n d t h e f o u r f a c e s o f a p y r a m i d o f c u t i c l e . D e n n e l l (1974) d e m o n s t r a t e d
Reality of Arthropod Cuticular Laminae
413
continuity of laminae around right-angled breaks by light microscopy, confirming Drach's (1939) observations. However, Bouligand (1972) had questioned the validity of such light microscope demonstrations by apparently indicating the interchangeability of I and F bands (laminae and inter-laminae s e n s u Dennell, 1974), depending on direction of illumination. The scanning electron micrographs presented here (Fig. 1 A - D ) support Drach's and Dennell's conclusions. On the Bouligand hypothesis there should be a discontinuity amounting to about half the lamina interval between corresponding laminae on each side of the angles of the pyramid, yet in fact the laminae appear to be continuous around the angles. This suggests the reality of laminae as structural components of the cuticle.
References Bouligand, Y. : Sur une architecture torsad6e r~pandue dans de nombreuses cuticules d'Arthropodes. C. r. hebd. S6anc. Acad. Sci., Paris 261, 3665-3668 (1965) Bouligand, Y.: Les orientations fibrillaires dans le squelette des Arthropodes. I. L'exemple des crabes, l'arrangement torsad+ des strades. J. Microsc. (Fr.) 11, 4 4 1 - 4 7 2 (1972) Bouligand, Y. : Twisted fibrous arrangements in biological materials and cholesteric mesophases. Tissue and Cell 4, 189-217 (1972) Dalingwater, J.E.: SEM observations on the cuticles of some decapod crustaceans. Zool. J. Linn. Soc. 56, 300-327 (1975) Dennell, R. : The cuticle of the crabs Cancer pagurus L. and Carcinus maenas (L.). Zool. J. Linn. Soc. 54, 241 - 2 4 5 (1974) Drach, P. : Mue et cycle d'intermue chez les Crustac6s D6capodes. Annls Inst. Oc~anogr., Monaco 19, 103-391 (1939) Mutvei, H. : SEM studies on arthropod exoskeletons. Part I : Decapod crustaceans Homarusgammarus L. and Carcinus maenas (L.). Bull. geol. Instn. Univ. Upsala N.S. 4, 73 - 8 0 (1974)
Received July 24, 1975/in revised form August 14, 1975
Short Communication
The Reality of Arthropod Cuticular Laminae John E. Dalingwater* Department of Zoology, The University, Manchester, England
Summary. Examination of etched pyramids of decapod crustacean cuticles with the scanning electron microscope indicates that laminae are continuous around the angles of the pyramids. This observation is in direct contrast to the result expected on Bouligand's (1965, 1971) hypothesis and suggests that laminae may be real structures. Key words: Cuticle- L a m i n a e - A r t h r o p o d - Scanning electron microscopy. Introduction
Bouligand's (1965, 1971) view of the laminae of arthropod cuticles as artefacts resulting from the sectioning of a helicoidal array of flat sheets of fibres still retains its influence, although recently Dennell (1974), Mutvei (1974) and Dalingwater (1975) have presented evidence which casts serious doubts on the validity of Bouligand's theory. The continuing popularity of the Bouligand model perhaps lies in the elegant simplicity with which it explains the apparently bewildering structural complexity that arthropod cuticles present when they are viewed in angled sections or breaks at high magnifications. Yet Bouligand (1972) has had to adapt his first conception of the twisted model to account for some aspects of this morphological and developmental complexity, so that to some extent his views can be reconciled with a low angle Drach system (Bouligand's Fig. 32d, 1972). Despite these modifications, Bouligand retained his conviction that laminae are artefacts. However, a simple procedure can be employed to dispute this aspect of the Bouligand model and is described below.
Material and Methods Pyramids of cuticle from the chelae of the decapod crustaceans Homarus gammarus (L), Carcinus maenas (L.) and Cancer pagurus L. were fashioned by cutting out square blocks of cuticle with a diamond wheel and shaping them with fine carborundum powder on glass plates. The pyramids Send offprint requests to: Dr. J.E. Dalingwater, Department of Zoology, The University, Manche-
ster M 13 9PL, England. * I would like to thank Professor R. Dennell for helpful discussions and the Department of Textile Technology, UMIST, for SEM facilities.
412
J.E. Dalingwater
Fig. 1 A - D . Scanning electron micrographs of a fashioned pyramid of the cuticle of Cancer pagurus L. (A) Viewed from above; continuity of laminae around the angles is just apparent, x 160. (B) Detail of one of the angles of the pyramid in which continuity of laminae (narrow dark bands) is clearly apparent. Inverted signal, x 800. (C) and (D). An angle of the pyramid. Normal and inverted signal. The laminae (normal: light bands; inverted: dark bands) are continuous around the angle, x 260
were then etched with 1% hydrochloric acid for five minutes, and air-dried in dust-free conditions before being mounted on stubs, gold-coated, and examined with a Cambridge "Stereoscan" scanning electron microscope.
Observations and Discussion I n t h e B o u l i g a n d m o d e l (1965, 1971) t h e a p p a r e n t l a m i n a e a r e n o t i n r e g i s t e r a r o u n d t h e f o u r f a c e s o f a p y r a m i d o f c u t i c l e . D e n n e l l (1974) d e m o n s t r a t e d
Reality of Arthropod Cuticular Laminae
413
continuity of laminae around right-angled breaks by light microscopy, confirming Drach's (1939) observations. However, Bouligand (1972) had questioned the validity of such light microscope demonstrations by apparently indicating the interchangeability of I and F bands (laminae and inter-laminae s e n s u Dennell, 1974), depending on direction of illumination. The scanning electron micrographs presented here (Fig. 1 A - D ) support Drach's and Dennell's conclusions. On the Bouligand hypothesis there should be a discontinuity amounting to about half the lamina interval between corresponding laminae on each side of the angles of the pyramid, yet in fact the laminae appear to be continuous around the angles. This suggests the reality of laminae as structural components of the cuticle.
References Bouligand, Y. : Sur une architecture torsad6e r~pandue dans de nombreuses cuticules d'Arthropodes. C. r. hebd. S6anc. Acad. Sci., Paris 261, 3665-3668 (1965) Bouligand, Y.: Les orientations fibrillaires dans le squelette des Arthropodes. I. L'exemple des crabes, l'arrangement torsad+ des strades. J. Microsc. (Fr.) 11, 4 4 1 - 4 7 2 (1972) Bouligand, Y. : Twisted fibrous arrangements in biological materials and cholesteric mesophases. Tissue and Cell 4, 189-217 (1972) Dalingwater, J.E.: SEM observations on the cuticles of some decapod crustaceans. Zool. J. Linn. Soc. 56, 300-327 (1975) Dennell, R. : The cuticle of the crabs Cancer pagurus L. and Carcinus maenas (L.). Zool. J. Linn. Soc. 54, 241 - 2 4 5 (1974) Drach, P. : Mue et cycle d'intermue chez les Crustac6s D6capodes. Annls Inst. Oc~anogr., Monaco 19, 103-391 (1939) Mutvei, H. : SEM studies on arthropod exoskeletons. Part I : Decapod crustaceans Homarusgammarus L. and Carcinus maenas (L.). Bull. geol. Instn. Univ. Upsala N.S. 4, 73 - 8 0 (1974)
Received July 24, 1975/in revised form August 14, 1975
