Table Of ContentThe Advances publishes reviews and critical articles covering the entire field of normal anatomy
(cytology, histology, cyto-and histochemistry, electron microscopy, macroscopy, experimental mor
phology and embryology and comparative anatomy). Papers dealing with anthropology and clinical
morphology will also be accepted with the aim of encouraging co-operation between anatomy and
related disciplines.
Papers, which may be in English, French or German, are normally commissioned, but original
papers and communications may be submitted and will be considered so long as they deal with a sub
ject comprehensively and meet the requirements of the" Advances".
For speed of publication and breadth of distribution, this journal appears in single issues which can
be purchased separately; 6 issues constitute one volume.
It is a fundamental condition that submitted m'1nuscripts have not been.and will not simultaneously
be submitted or published elsewhere. With the acceptance of a manuscript for publication, the pub
lisher acquires full and exclusive copyright for all languages and countries. 25 copies of each paper are
supplied free of charge.
Die Ergebnisse dienen der Veroffentlichung zusammenfassender und kritischer Artike1 aus dem
Gesamtgebiet der normalen Anatomie (Cytologie, Histologie, Cyto-und Histochernie, Elektronen
mikroskopie, Makroskopie, experimentelle Morphologie und Embryologie und vergieichende Ana
tomie). Aufgenommen werden ferner Arbeiten anthropologischen und morphologisch-klinischen In
halts, mit dem Ziel, die Zusammenarbeit zwischen Anatomie und Nachbardisziplinen zu fOrdern.
Zur Veroffentlichung ge1angen in erster Linie angeforderte Manuskripte, jedoch werden auch ein
gesandte Arbeiten und Originalmitteilungen beriicksichtigt, sofern sie ein Gebiet umfassend abhan
deln tind den Anforderungen der "Ergebnisse" geniigen. Die Veroffentiichungen erfolgen in eng
lischer, deutscher oder franzosischer Sprache.
Die Arbeiten erscheinen im Interesse einer raschen Veroffentiichung und einer weiten Verbrei
tung als einze1n berechnete Hefte; je 6 Hefte bilden einen Band.
Grundsatzlich diirfen nur Arbeiten eingesandt werden, die nicht gleichzeitig an anderer Stelle zur
Veroffentiichung eingereicht oder bereits veroffentiicht worden sind. Der Autor verpflichtet sich,
seinen Beitrag auch nachtriiglich nicht an anderer Stelle zu publizieren. Die Mitarbeiter erhalten von
ihren Arbeiten zusammen 25 Freiexemplare.
Les resultats publient des sommaires et des articles critiques concernant l' ensemble du domaine de
I'anatomie normale (cytologie, histologie, cyto- et histochimie, microscopie electronique, macros
copie, morphologie experimentale, embryologie et anatomie comparee). Seront publies en outre les
articles traitant de I'anthropologie et de la morphologie clinique, en vue d'encourager la collaboration
entre I'anatomie et les disciplines voisines.
Seront publies en priorite les articles expressement demandes, nous tiendrons toutefois compte"
des articles qui nous seront envoyes dans la mesure oil ils traitent d'un sejet dans son ensemble et
correspondent aux standards des «Revues ». Les publications seront faites en langues anglaise,
allemande ou francraise.
Dans l'interet d'une publication rapide et d'une large diffusion les travaux publies paraitront dans
des cahiers individuels, diffuses separement: 6 cahiers forment un volume.
En principe, seuls les manuscripts qui n'ont encore ete publies ni dans Ie pays d'origine ni a
a
I'entranger peuvent nous etre soumis. L'auteur s'engage en outre ne pas les publier ailleurs
ulterieurement. Les auteurs recevront 25 exemplaires gratuits de leur publication.
a:
Manuscripts should be addressed to / Manuskripte sind zu senden an / Envoyer les manuscrits
Prof. Dr. A. BRODAL, Universitetet i Oslo, Anatomisk Institutt, Karl Johans Gate 47 (Domus
Media), Oslo 1/Norwegen
Prof. W. HILD, Department of Anatomy, Medical Branch, The University of Texas, Galveston, Texas
77550/uSA
Prof. Dr. J. van LIMBORGH, Universiteit van Amsterdam, Anatomisch-Embryologisch Labora
torium, Mauritskade 61, Amsterdam-O/Holland
Prof. Dr. R. ORTMANN, Anatomisches Institut der Universitiit, Lindenburg, D-5000 KOin-Linden
thai
Prof. Dr. T. H. SCHIEBLER, Anatomisches Institut der Universitat, KoellikerstraBe 6, D-8700 Wiirz
burg
Prof. Dr. G. TONDURY, Direktion der Anatomie, GloriastraBe 19, CH-8006 Ziirich/Schweiz
Prof. Dr. E. WOLFF, Lab. d'Embryologie Experimentale, College de France, 11 Place Marcelin
Berthelot, F-75005 Paris/Frankreich
Advances in Anatomy, Embryology and Cell Biology
Ergebnisse der Anatomie und Entwicklungsgeschichte
Revues d'anatomie et de morphologie experimentale
Vol. 55 . Fasc. 3
Editors:
A. Brodal, Oslo' W. Hild, Galveston' J. van Limborgh,
Amsterdam' R. Ortmann, Kaln . T.H. Schiebler,
Wurzburg . G. Tandury, Zurich· E. Wolff, Paris
H.-J. Wagner
Cell Types
and Connectivity Patterns
in Mosaic Retinas
With 30 Figures
Springer-Verlag Berlin Heidelberg New York 1978
Priv.-Doz. Dr. rer. nat. Dipl.-Biol. H.-J. Wagner, Abteilung fill Klinische Morphologie,
Universitat VIm, Oberer Eselsberg, D-7900 VIm, Federal Republic of Germany
ISBN-13: 978-3-540-09013-7 e-ISBN-13: 978-3-642-67071-8
DOl: 10.1007/978-3-642-67071-8
Library of Congress Cataloging in Publication Data Wagner, H.-J. 1945- Cell types and
connectivity patterns in mosaic retinas. (Advances in anatomy, embryology, and cell biology; v.
55, fasc. 3) Bibliography: p. Includes index. 1. Retina. 2. Cell. 3. Cell aggregation. I. Title. II.
Title: Mosaic retinas. III. Series. [DNLM: 1. Retina-Cytology. WI AD433K v. 55 fasc. 3 / WW270
W133c] QL801.E67 vol. 55, fasc. 3 [QL949) 574.4'08s [591.1'823)78-10130
This work is subject to copyright. All rights are reserved, whether the whole or part of the materi
als is concerned specifically those of translation, reprinting, re-use of illustrations, broadcasting,
reproduction by photocopying machine or similar means, and storage in data banks.
Under § 54 of the German Copyright Law where copies are made for other than private use, a fee is
payable to the publisher, the amount of the fee to be determined by agreement with the publisher.
© Springer-Verlag Berlin Heidelberg 1978
The use of registered names, trademarks, etc. in this publication does not imply, even in the ab
sence of a specific statement, that such names are exempt from the relevant protective laws and
regulations and therefore free for general use.
Composition, printing and binding: H. Stiirtz AG, Universitatsdruckerei, Wiirzburg
2121/3321-543210
Contents
Abbreviations ............................................. 7
1. Introduction ....... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9
2. Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 10
2.1. Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 10
2.2. Methods ........................................... 12
2.2.1. Light Microscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 12
2.2.1.1. Routine Histology .................................... 12
2.2.1.2. Golgi Impregnation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 12
2.2.1.3. Isolated Cells . . . . . ................................. " 12
2.2.2. Electron Microscopy ................................. " 12
2.2.2.1. Routine Preparation .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 12
2.2.2.2. Golgi EM Technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 12
2.2.2.3. Ultra Histochemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 13
3. Results and Discussion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 13
3.1. Cells Participating in the Formation of the External Plexiform Layer . .. 13
3.1.1. Visual Cells ....................................... " 13
3.1.2. Bipolar Cells ........................................ 18
3.1.3. Horizontal Cells. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 21
3.1.4. Interplexiform Cells ................................... 23
3.1.5. Mtiller Cells. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 26
3.1.6. Cell Types of the External Plexiform Layer: Discussion . . . . . . . . . . .. 26
3.1. 6.1. Visual Cells ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 28
3.1.6.2. Bipolar Cells ........................................ 30
3.1.6.3. Horizontal Cells .................................... " 31
3.1.6.4. Interplexiform Cells ................................... 32
3.1.6.5. Mtiller Cells ....................................... " 32
3.2. Cell Mosaics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 33
3.2.1. Mosaics of Cells Participating in the Formation of the
External Plexiform Layer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 35
3.2.1.1. Visual Cell Mosaics . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . .. 35
3.2.1.2. Cone Horizontal Cells .................................. 46
3.2.2. Patterns in the Internal Plexiform Layer . . . . . . . . . . . . . . . . . . . . .. 46
3.2.3. Biological Significance of Pattern Formation in Teleost Retinas. . . . . .. 47
3.3. Patterns of Connectivity in the External Plexiform Layer. . . . . . . . . .. 48
3.3.1. General Morphology of Cone Pedic1es . . . . . . . . . . . . . . . . . . . . . . .. 49
3.3.2. The Ribbon Synapse. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 49
3.3.3. Constancy of the Number of Synaptic Ribbons in Different
Cone Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 56
3.3.4. Convergence and Divergence Between Cones and Cone Horizontal
Cells in Nannacara anomala .............................. 59
5
3.3.5. Contacts of Bipolar Dendrites in Tangential Sections. . . . . . . . . . . . .. 65
3.3.6. Functional Interpretation of the Patterns of Connectivity in the
External Plexiform Layer of Mosaic Retinas ................... 65
3.3.6.1. Intracellular Recordings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 65
3.3.6.2. Significance for Color Vision ............................. 67
3.3.6.3. Lateral Inhibition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 68
4. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 70
s.
Surnrnary .......................................... 72
6. References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 74
Subject Index ............................................. 80
6
Abbreviations
ad arciform density
adcp accessory double cone pedicle
ama amacrine cell
ascel accessory single cone ellipsoid
ascn accessory single cone nucleus
ascp accessory single cone pedicle
bi bipolar cell
bia bipolar axon
biat bipolar axon terminal
bp basal process
eel cone ellipsoid
cho cone horizontal cell
choa cone horizontal axon
chon cone horizontal nucleus
cp cone pedicle
cscel central single cone ellipsoid
cscn central single cone nucleus
cscp central single cone pedicle
dca double cone axon
dcel double cone ellipsoid
dcmy double cone myoid
dcn double cone nucleus
dcos double cone outer segment
dcp double cone pedicle
f filament
gcd ganglion cell dendrite
gcn ganglion cell nucleus
ho horizontal cell process
ips interplexiform cell soma
ipt interplexiform cell terminal
Ibia large bipolar cell axon
Ibid large bipolar eell dendrite
Ibis large bipolar cell soma
mbia intermediate bipolar cell axon
mbiat intermediate bipolar cell axon terminal
mbid intermediate bipolar cell dendrite
mbis intermediate bipolar cell soma
mf Miiller cell
pdcp principle double cone pedicle
prel bundle of photoreceptor ellipsoids
ra rod axon
rei rod ellipsoid
rho rod horizontal cell
rmy rod myoid
rn rod nucleus
ros rod outer segment
rs rod spherule
sbia small bipolar cell axon
sbiat small bipolar cell axon terminal
sbid small bipolar cell dendrite
sbis small bipolar cell soma
sc single cone
sca single cone axon
scel single cone ellipsoid
scmy single cone myoid
7
scn single cone nucleus
scos single cone outer segment
scp single cone pedicle
sr synaptic ribbon
srd synaptic ridge
sv synaptic vesicle
ELM external limiting membrane
ENL external nuclear layer
EPL external plexiform layer
GeL ganglion cell layer
ILM internal limiting membrane
INL internal nuclear layer
IPL internal plexiform layer
PEL pigment epithelial layer
The bar in the lower part of each picture gives the equivalent distance in !lm (exception, Figs.
20-22: distance in nm). If not otherwise mentioned micrographs are taken from the retina of
Nannacara anomala.
8
1. Introduction
In many parts of vertebrate and invertebrate central nervous systems, groups of nerve
or receptor cells can be found that are arranged and connected according to a precise,
functionally defined pattern (Braitenberg, 1973; Santini, 1975; Strausfeld, 1976;
Chan-Palay, 1977). In these cases, groups of cell bodies or synapses appear as basically
similar configurations, which, however, are different in detail from each other. Such
abstract patterns of connectivity are of a statistical nature and do not allow, in a given
example, for the prediction of the localization or connections of a particular cell.
"Wiring diagrams", therefore, can be obtained only from a multitude of individual
observations. In contrast, in several sensory organs, concrete patterns occur that con
sist of a regular, mosaic-like, and geometric arrangement of similar cell types. The
constancy of such a mosaic allows predictions about certain units of the pattern on the
basis of only a few exemplary observations. Typical examples are found in the visual
system: In the compound eye of insects, each ommatidium contains a definite number
of visual cells that are grouped around the optical axis in a hexogonal array (Kirsch
feld, 1967); in the vertebrate retina, mosaics of geometrically arranged cones are found
most frequently in lower vertebrates; they are common among teleosts. A number of
studies have dealt with their phylogenetic significance and their functional role as
adaptation to specific environments or modes of feeding. The results of these investi
gations, however, are quite complex, providing neither simple nor clear explanations of
this phenomenon (Engstrom, 1963b; for literature see Ahlbert, 1975).
In insects as well as in several teleosts, it has been observed that mosaics are not
restricted to the layer of photoreceptor cells but may also occur in more central layers
of the visual pathway (Braitenberg, 1967; Wagner, 1972; Strausfeld, 1976). This would
suggest that such patterns do not result from an "attempt" to obtain a high visual cell
density by creating this special way of packing (Locket, 1975) but that they are a mor
phologic expression of certain patterns of neuronal connectivity (Wagner, 1976b).
Thus correspondences in arrangement of visual cells and neurons in the inner retinal
layers present an opportunity for elucidating connectivity patterns in the synaptic
layers of the retina. In species without regularly arranged cells, only the convergence
between certain types of receptor cells and subsequent neurons can be examined; in
mosaic retinas, however, it is possible to study directly the divergence between these
cell types. This particular aspect could not be considered in investigations of the gold
fish (Stell, 1967, 1975, 1976; Stell et aI., 1975) or the rudd (Scholes, 1975) because
of the irregular arrangement of receptors and neuronal elements in these species. The
present investigation represents the first attempt to obtain quantitative data concern
ing the degree of divergence in a vertebrate retina.
Although the formation of patterns can be observed in both synaptic layers of the
retina, this study deals predominantly with the external plexiform layer. This layer
constitutes the primary center of neural integration in the retina, where visual cell
pedicles represent the afferent parts that are connected to dendrites of bipolar cells
as efferent parts. Horizontal and interplexiform cells, as interneurons, control the pro
cess of direct signal transmission.
A South American cichlid fish (Nannacara anomala) was the system of choice be
cause, in this species, only two types of cones and one type of rod are found in the
visual cell layer, and only two types of horizontal cells in the inner nuclear layer. In
9
this respect, the structure of the external plexiform layer is much less complicated
than that in cyprinids (goldfish, rudd, see Ali and Anctil, 1976), which are more com
monly studied. Despite the relatively simple organization of the outer retinal layers,
Nannacara, like the majority of other cichlid species, is a fish that is predominantly
visually oriented. This has been demonstrated most clearly in ethologic experiments
by Kuenzer (1968). Eibl-Eibesfeldt (1969) showed that other cichlid fish, too, mainly
use optical stimuli for their highly differentiated behavior. This species, therefore, is
proposed as a model from which some general conclusions may be drawn concerning
the principles of connectivity, which should also hold for species with a more compli
cated retinal structure.
Using methods of classical neuroanatomy like silver impregnation after Golgi-Cajal,
an inventory is presented of cell types that participate in the formation of the external
plexiform layer. Connections between receptor cells and secondary neurons, traced in
thick sections, are confirmed and examined more closely in semi- and ultrathin sec
tions of Golgi-impregnated cells. This qualitative analysis is followed by a quantitative
evaluation in tangential sections in which the total extent of dendritic trees can be de
monstrated with all their terminals. On the basis of these observations, schematic dia
grams of connectivities in the external plexiform layer are designed that provide infor
mation about the degrees of convergence and divergence.
A central point of interest in the external plexiform layer is the so-called ribbon sy
napse. It comprises a complex of individual synapses and is involved in the signal
transmission from visual to bipolar and horizontal cells. For a more detailed charac
terization of its constituents, ultrastructural and ultrahistochemical investigations are
carried out with the synaptic ribbon itself and the adjacent membrane complexes. In
a comparative study about the number of ribbon synapses in the cone pedicles of four
species with different cone mosaics, some principles of connectivity in the external
plexiform layer are discussed.
2. Materials and Methods
2.1. Materials
The species studied are listed in Table 1 according to their systematic position. This table also con
tains short notes about habitat, origin, number, and age of the experimental animals. Based on
their origin, several groups may be distinguished: The major object of this study, Nannacara ano
mala, was obtained either by breeding in the laboratory or from local pet shops. Other aquarium
fish like goldfish and piranha also were purchased from pet shops. Brook trout yearlings were pro
vided by the provincial fish hatchery at St. Faustin (Quebec, Canada). The two hiodontid species
were caught alive in the north of the province of Quebec, in the lake of Montigny. The group of
tide pool-fishes comprises an ecologic community from rocky areas of the Brasilian coast. These
species were caught by Prof. M.A. Ali by seining at the Instituto de Biologia marinha of the Uni
versidade de Sao Paulo (Brasil).
In the present study, only light-adapted specimens were used.
10
