Morphological Characterization of Three Phenotypes of the Isopod Armadillidium vulgare

The morphological characteristics and ommochrome quantity in the integument of red, white, and wild type (black-grey) Armadillidium vulgare were studied. The red phenotype was found to possess two kinds of immature ommochrome pigment granules within its pigment cells, in addition to mature pigment granules. The immature granules seemed to contain uniformly distributed fibrilles, or to have an electron-dense central region surrounded by an electron-lucent outer edge. Since these immature pigment granules were typically observed to be distributed along with the mature ones, and were also more easily extractable than the wild type's, it is hypothesized that ommochrome granule maturation in the red phenotype may occur slowly due to a defect in the pigment granule internal process which combines pigments with matrix proteins. Regarding the white phenotype, although its pigment cells were undeveloped, several large-sized vesicles containing a small amount of electron-dense material appeared in the pigment cell cytoplasm. The wild and red type males of A. vulgare were found to have an ommochrome content twice as large as that of the corresponding females, with no ommochrome pigment being detected in the white phenotype. The genetic relationship between the white and red phenotypes was discussed using as a basis the observed pigment granule structure.     

Turnover of pigment granules: Cyclic catabolism and anabolism of ommochromes within epidermal cells

Ommochromes are end products of the tryptophan metabolism in arthropods. While the anabolism of ommochromes has been well studied, the catabolism is totally unknown. In order to study it, we used the crab-spider Misumena vatia, which is able to change color reversibly in a few days, from yellow to white and back. Ommochromes is the only pigment class responsible for the body coloration in this animal. The aim of this study was to analyze the fine structure of the epidermal cells in bleaching spiders, in an attempt to correlate morphological changes with the fate of the pigment granules. Central to the process of bleaching is the lysis of the ommochrome granules. In the same cell, intact granules and granules in different degradation stages are found. The degradation begins with granule autolysis. Some components are extruded in the extracellular space and others are recycled via autophagy. Abundant glycogen appears associated to granulolysis. In a later stage of bleaching, ommochrome progranules, typical of white spiders, appear in the distal zone of the same epidermal cell. Catabolism and anabolism of pigment granules thus take place simultaneously in spider epidermal cells. A cyclic pathway of pigment granules formation and degradation, throughout a complete cycle of color change is proposed, together with an explanation for this turnover, involving photoprotection against UV by ommochromes metabolites. The presence of this turnover for melanins is discussed.     

THE MICROSTRUCTURE OF THE COMPOUND EYES OF INSECTS

The apposition eyes of two diurnal insects, Sarcophaga bullata (Diptera) and Anax junius (Odonata), have been examined with the electron microscope. In the latter case only the rhabdom is described. The rhabdom of the fly consists of a central matrix and seven rhabdomeres, one for each retinula cell. The rhabdomeres show an ordered internal structure built up of transverse tubes, hexagonal in cross-section. These slender compartments running the width of the rhabdomere are 370 A in diameter. After fixation with osmium tetroxide the walls of the compartments are more electron dense than the interiors. The retinula cells contain mitochondria, and pigment granules smaller than those found in the pigment cells. These granules tend to cluster close behind the membranes which separate the retinula cells from their rhabdomeres. The rhabdom of the dragonfly is a single structure which appears to be composed of three fused "rhabdomeres," each similar to a rhabdomere of Sarcophaga. Reasons are given for believing that the rhabdom may be the site of photoreception, as well as the organ for analyzing plane-polarized light, as suggested by other workers.     

Ultrastructure and migration of screening pigments in the retina of Pieris rapae L. (Lepidoptera,Pieridae)

Summary The retinal morphology of the butterfly, Pieris rapae L., was investigated using light and electron microscopy with special emphasis on the morphology and distribution of its screening pigments. Pigment migration in pigment and retinula cells was analysed after light-dark adaptation and after different selective chromatic adaptations. The primary pigment cells with white to yellow-green pigments symmetrically surround the cone process and the distal half of the crystalline cone, whilst the six secondary pigment cells, around each ommatidium, contain dark brown pigment granules. The nine retinula cells in one ommatidium can be categorised into four types. Receptor cells 1–4, which have microvilli in the distal half of the ommatidium only, contain numerous dark brown pigment granules. On the basis of the pigment content and morphology of their pigment granules, two distal groups of cells, cells 1, 2 and cells 3, 4 can be distinguished. The four diagonally arranged cells (5–8), with rhabdomeric structures and pigments in the proximal half of the cells, contain small red pigment granules of irregular shape. The ninth cell, which has only a small number of microvilli, lacks pigment. Chromatic adaptation experiments in which the location of retinula cell pigment granules was used as a criterium reveal two UV-receptors (cells 1 and 2), two green receptors (cells 3 and 4) and four cells (5–8) containing the red screening pigment, with a yellow-green sensitivity.     

A single-base deletion in an ABC transporter gene causes white eyes, white eggs, and translucent larval skin in the silkworm w-3(oe) mutant

The w-3(oe) silkworm mutant has white eyes and eggs due to the absence of ommochrome pigments in the eye pigment cells and serosa cells. The mutant is also characterized by translucent larval skin resulting from a deficiency in the transportation of uric acid, which acts as a white pigment in larval epidermal cells. A silkworm homolog of the fruitfly white gene, Bmwh3, a member of ATP-binding cassette transporter superfamily, was mapped on the w-3 locus. The w-3(oe) mutant has a single-base deletion in exon 2 and a premature stop codon at the 5' end of exon 3. These results show that w-3 is equivalent to Bmwh3 and is responsible for the transportation of ommochrome precursors and uric acid into pigment granules and urate granules, respectively.     

Die Wanderung der Pigmentgranula in der Epidermis beim physiologischen Farbwechsel von Carausius morosus

Carausius morosus is one of the few insects exhibiting physiological colour change in the epidermal cells. The distribution of ommochromes, carotinoids, and pterindines is analysed in light and dark adapted animals.In light adapted animals the ommochrome granules are concentrated at the proximal cell membrane. During dark adaption they move to the distal cell membrane, dispersing there over the whole cell forming a shield of dark pigment. The carotinoid granules behave in a similar way. The rod shaped pteridine granules are concentrated in the distal half of the epidermis. They show no daytime dependent movements. However, they take part in the physiological colour change indirectly. Apparently, biliverdin is not attached to granules but dissolved in the epidermal cells.     

Microtubules in the epidermal cells of Carausius morosus (Br.). Their pattern and relation to pigment migration

The existence of one or several systems of microtubules, consisting of a central bundle that branches off towards the basal and distal ends of epidermal cells of Carausius morosus has been shown by indirect immuno-fluorescence microscopy using monospecific anti-tubulin. The pattern of microtubules coincides with the position of the ommochrome granules and their migration path during physiological colour change. The ommochrome granules stick to isolated bundles of microtubules. Small bundles of microtubules extend almost perpendicularly towards the apical cell membrane where they are attached. Distally they are covered by pore channels within the cuticle. Parallel to the basal cell membrane and in close contact with it, there are very small bundles of microtubules. These findings strongly support the idea that during physiological colour change the ommochrome granules migrate along a firmly fixed system of microtubules.     

THE FINE STRUCTURE OF ASTROCYTES IN THE CEREBRAL CORTEX AND THEIR RESPONSE TO FOCAL INJURY PRODUCED BY HEAVY IONIZING PARTICLES

Normal and reactive astrocytes in the cerebral cortex of the rat have been studied with the electron microscope following focal alpha particle irradiation. The presence of glycogen and approximately 60-A fibrils identify astrocyte cytoplasm in formalin-perfused tissue. The glycogen particles facilitate the identification of small processes and subpial and perivascular end-feet. Both protoplasmic and fibrous astrocytes contain cytoplasmic fibrils and should be distinguished on the basis of the configuration of their processes and their distribution. Acutely reactive astrocytes are characterized by a marked increase in the number of glycogen granules and mitochondria from the first day after irradiation. These cells later hypertrophy and accumulate lipid bodies and increased numbers of cytoplasmic fibrils. The glial "scar" consists of a greatly expanded volume of astrocyte cytoplasm filled with fibrils and displays no signs of astrocyte death, reversion to primitive forms, or extensive multiplication.     

LIPOFUSCIN (AGING) PIGMENT GRANULES OF THE NEWBORN HUMAN LIVER

We have observed pigmented cytoplasmic granules, with the characteristic staining properties of lipofuscin (ceroid, "wear-and-tear") pigment, in newborn human liver. The pigment is found at the periphery of the lobule in hepatocytes and some bile ductular cells. It is acid-fast, PAS-positive after diastase digestion, slightly argyophilic and sudanophilic, and markedly Schmorl's- and peroxidase positive in paraffin sections. Difficult to see in sections stained with hematoxylin and eosin, the pigment can be detected in unstained sections. The granules also resemble lipofuscin found in adult tissues, in their ultra-structural and enzymatic properties. They are polymorphic, contain granular material of moderate and high electron opacity, and are delimited by a single membrane. Acid phosphatase and β-glucuronidase activities are visualized in the newborn granules, identifying them as lysosomes. The granules also contain copper and, to a much lesser extent, iron. The accumulation of lipofuscin pigment in lysosomes in many tissues correlates well with aging, and this process has been interpreted as a reflection of cellular degeneration or wear-and-tear. However, the presence of lipofuscin granules as a constant component of neonatal liver suggests that they are not a measure of cellular senescence.     

THE CYTOLOGY OF THE NORMAL PARATHYROID GLANDS OF MAN AND VIRGINIA DEER : A Light and Electron Microscopic Study with Morphologic Evidence of Secretory Activity

The normal parathyroids of six humans and a Virginia deer were studied by light and electron microscopy. The parenchyma of the deer parathyroid is composed of uniform chief cells, which contained 100 to 400 mµ electron-opaque, membrane-limited granules, presumed to be secretory granules, in addition to the usual cytoplasmic organelles. Desmosomes are present between adjacent cells, and rare cilia are observed protruding from the chief cells into the intercellular space. The human parathyroids contain chief cells in two phases—active and inactive—as well as oxyphil cells. Active chief cells have a large Golgi apparatus, sparse glycogen, numerous secretory granules, and rare cilia. Inactive chief cells contain a small Golgi apparatus, abundant glycogen, and few secretory granules. Both forms have the usual cytoplasmic organelles and, between adjacent cells, desmosomes. Oxyphil cell cytoplasm is composed of tightly packed mitochondria and glycogen granules, with rare secretory granules. Cells with cytoplasmic characteristics intermediate between chief and oxyphil cells, possibly representing transitional cells, have been observed. Secretory granules of both man and deer are composed of 100 to 200 A particles and short rods, and the granules develop from prosecretory granules in the Golgi region of the cell. The human secretory granules are smaller and more variable in shape than those of the deer. The granules are iron and chrome alum hematoxylin-positive, argyrophilic, and aldehyde fuchsin-positive, permitting light microscopic identification. They are also found in the capillary endothelial cells of the parathyroid and in its surrounding connective tissue. The secretory granules of the parathyroid cells can thus be followed from their formation in the Golgi apparatus almost to their extrusion into the blood stream.     

大草蛉成虫复眼的外部形态及其显微结构

用扫描电镜和光学显微镜观察了大草蛉Chrysopa pallens Ramber成虫复眼的外部形态及明、暗适应和性别对其显微结构的影响。结果发现：（1）其复眼呈半球形,位于头部两侧,略成“八”字形排列,单个复眼约由3 600个小眼组成,最前和最后小眼之间的夹角约为180°,最上和最下小眼之间的夹角约200°;（2）小眼主要由角膜、晶锥和6～8个小网膜细胞、基膜组成,外围环绕有2个初级虹膜色素细胞和6个次级虹膜色素细胞,基膜处有色素颗粒分布;（3）暗适应时,晶锥开裂程度较大,远端5～7个网膜细胞核向远端移动,与晶锥近端相接或接近,次级虹膜色素颗粒亦向远端移动包围晶锥;明适应时,晶锥开裂程度小或闭合,远端网膜细胞核向近端移动,透明带显现,大部分次级虹膜色素颗粒亦向近端移动分布在小网膜细胞柱周围,包被透明带;（4）在相同的明、暗适应下,雌、雄成虫复眼的显微结构无明显差异。结果表明大草蛉复眼为透明带明显的重叠象眼,其小眼不但具有次级虹膜色素颗粒纵向移动的常规调光机制,还存在晶锥开闭、远端网膜细胞核移动和基膜色素颗粒纵向扩散的调光新机制。     

Developmental changes in the amount of pigments,inorganic material and uric acid inLocusta migratoria cinerascens Fabr. (Orthoptera,Acrididae) epidermis,during the last larval instar and the imaginal life

Summary Locusta epidermal cells accumulate in their cytoplasm various inclusions which give rise to tegumentary patterns of brown spots and lines.Five major types of inclusions are identified. Ultrastructural examination and electron microprobe studies show that types 1, 2 and 3 correspond to successive steps of concentric pigment and mineral deposition on a matrix. Type 3 is the richest in ommochromes (acridiommatins 1 and 2), and mineralized with calcium phosphate. Type 4 is characterized by pigment and mineral disappearance, which in type. 5 are substituted by uric microcrystals. From the end of the 4^th instar to the beginning of the imaginal life, three generations of inclusions are observed to succeed each other in the different epidermal cells. Tergal, pleural and sternal areas are characterized by the morphology and biochemical composition of the inclusions they accumulate. Despite cellular asynchronism, ecdysis is accompanied by a phase of pigment and cation elimination followed by the storage of uric microcrystals.Abbreviations L larval instar (numbered I to V) Abbreviations used in Figs 2, 3 and 4 B basal membrane - Cu cuticle - E epidermis - Gly glycogen - Ly lysosome - M muscle cell - N nucleus - P pigment (ommochrome) granule - SC secretory cell - tu microtubule - Ur uric acid microcrystal     

The nauplius eye complex in 'conchostracans'(Crustacea, Branchiopoda: Laevicaudata, Spinicaudata, Cyclestherida) and its phylogenetic implications

The nauplius eye in Cyclestherida, Laevicaudata and Spinicaudata (previously collectively termed Conchostraca) consists of four cups of inverse sensory cells separated by a pigment layer and a tapetum layer. There are two lateral and two medial cups, a ventral medial cup and a posterior medial cup. The pigment and tapetum layers contain two different kinds of pigment granules, the inner pigment layer relatively large, dark (and electron dense) granules, and the outer tapetum layer light, reflective pigment granules. The presence of four cups and two different kinds of pigment granules are interpreted as autapomorphies of Phyllopoda. The position and shape of the nauplius eye in Spinicaudata is very distinct and herein interpreted as an autapomorphy of this taxon.Additional frontal eyes might be present dorsally or ventrally in varying proximity to the nauplius eye, but they have separate nerves from their sensory cells to the nauplius eye centre in the protocerebrum. Rhabdomeric structures are present in all these frontal eyes, evidencing their light sensitivity. In Lynceus biformis and L. tatei (Laevicaudata), two pairs of frontal eyes were found. In Cyclestheria hislopi (Cyclestherida), an unpaired ventral frontal eye is present. We did not find additional frontal eyes in Limnadopsis parvispinus and Caenestheriella sp. (Spinicaudata).     

Further studies on the development of the eye of Drosophila melanogaster. I. The ommatidia

Electron microscope observations on the differentiating Drosophila eye show an extensive proliferation of parallel arrays of microtubules at periods preceding, or coinciding with, alterations in cellular morphology. In the retinular cells they are aligned in the direction of elongation and close to the developing rhabdomeres, forming a cylinder around the central ommatidial axis. At a later stage, in the cone cells, they are aligned in the direction of cellular contraction. Thus as in other developing systems microtubules appear to be directly involved in the morphogenesis of the Drosophila eye. In the retinular cells they gradually disappear during elongation, whereas they persist in the cone cells. The pigment cells contain few of these structures. The distribution of two types of specialised cell attachments, adhering zones and septate desmosomes is discussed in relation to intercellular morphogenesis and communication. The rhabdomeres originate from infoldings of the plasma membrane which later grow out into typical microvilli. Unusul cytoplasmic granules are described in the pigment cells of early pupae.     

Eye color pigment granules in Drosophila mauritiana: mosaics produced by excision of a transposable element

Compound eyes of the white-peach (wpch) mutant strain of Drosophila mauritiana have some pigment and receptor cells with wild-type eye color pigmentation. These eyes are mosaic, because excision of a transposable element reverts wpch to wild type during the development of somatic cells. Wild-type patches have three types of pigment granule residing in three respective cell types: primary pigment cells, secondary pigment cells, and retinula (visual receptor) cells. Most aspects of these granules, as well as all other aspects of compound eye ultrastructure, are exactly as in the better studied sibling species D. melanogaster. In the wpch parts of the eye, small and giant unpigmented "pigment granules" reside in secondary pigment cells. These white granules are just like the corresponding granules of w mutant D. melanogaster. Small vs. large patches of pigmented cells likely represent excision events occurring late vs. early respectively during development. Mosaics of eye color markers have been important in developmental analyses; the ease of constructing mosaics of D. mauritiana gives this preparation advantages for mosaic analyses.     

LOCALIZATION OF ACID PHOSPHATASE IN LIPOFUSCIN GRANULES AND POSSIBLE AUTOPHAGIC VACUOLES IN INTERSTITIAL CELLS OF THE GUINEA PIG TESTIS

The intracellular localization of acid phosphatase in guinea pig testicular interstitial cells was investigated by incubating nonfrozen thick sections of glutaraldehyde-perfused testis in a modified Gomori medium and preparing the tissue for electron microscopy. Lipofuscin pigment granules in these cells contain dense pigment, granular matrix, and often a lipid droplet. Reaction product is seen in the matrix of the pigment granules, and they may therefore be called residual bodies. At least some of the dense pigment appears to be derived from myelin figures and membrane whorls, since suitable intermediates can be seen. Lipid droplets found free in the cytoplasm are another possible source of pigment. In both cases the chemical mechanism is presumed to be autoxidation of unsaturated lipid. Acid phosphatase is present in the inner cisterna of Golgi elements. Enzyme activity also appears in possible autophagic vacuoles bounded by double membranes; the reaction product lies between the membranes. Consideration of the enzyme as a tracer suggests that the autophagic vacuoles are derived from the Golgi complex. Possible stages in the formation of these vacuoles by the inner Golgi cisternae are observed.     

THE FINE STRUCTURE OF GIARDIA MURIS

Giardia is a noninvasive intestinal zooflagellate. This electron microscope study demonstrates the fine structure of the trophozoite of Giardia muris in the lumen of the duodenum of the mouse as it appears after combined glutaraldehyde and acrolein fixation and osmium tetroxide postfixation. Giardia muris is of teardrop shape, rounded anteriorly, with a convex dorsal surface and a concave ventral one. The anterior two-thirds of the ventral surface is modified to form an adhesive disc. The adhesive disc is divided into 2 lobes whose medial surfaces form the median groove. The marginal grooves are the spaces between the lateral crests of the adhesive disc and a protruding portion of the peripheral cytoplasm. The organism has 2 nuclei, 1 dorsal to each lobe of the adhesive disc. Between the anterior poles of the nuclei, basal bodies give rise to 8 paired flagella. The median body, unique to Giardia, is situated between the posterior poles of the nuclei. The cytoplasm contains 300-A granules that resemble particulate glycogen, 150- to 200-A granules that resemble ribosomes, and fusiform clefts. The dorsal portion of the cell periphery is occupied by a linear array of flattened vacuoles, some of which contain clusters of dense particles. The ventrolateral cytoplasm is composed of regularly packed coarse and fine filaments which extend as a striated flange around the adhesive disc. The adhesive disc is composed of a layer of microtubules which are joined to the cytoplasm by regularly spaced fibrous ribbons. The plasma membrane covers the ventral and lateral surfaces of the disc. The median body consists of an oval aggregate of curved microtubules. Microtubules extend ventrally from the median body to lie alongside the caudal flagella. The intracytoplasmic portions of the caudal, lateral, and anterior flagella course considerable distances, accompanied by hollow filaments adjacent to their outer doublets. The intracytoplasmic portions of the anterior flagella are accompanied also by finely granular rodlike bodies. No structures identifiable as mitochondria, smooth endoplasmic reticulum, the Golgi complex, lysosomes, or axostyles are recognized.     

Morphological and Biochemical Characterization of the Cream Markings in the Integument of the Female Isopod,Armadillidium vulgare

Cream markings aligned along the dorsal region of the female isopod, A. vulgare, were investigated with light and a fluorescence microscope and an electron microscope. Biochemical studies were also carried out. The cream markings were observed in the dorsal integument as a group of cream-colored chromatophores that emit a yellow fluorescence. These chromatophores, which are distinguishable from ommochrome chromatophores, contained numerous granules in the cytoplasm, and these granules (0.6–3.0 μm in length by 0.4–1.5 μm in width) were electron-lucent and spheroidal in shape with a concentric arrangement of membranes. Based on various biochemical analyses, the principal component of the yellow pigment isolated from the cream markings was identified as sepiapterin. These facts revealed that the cream markings are the chromatophores that contain pteridine granules. The males have no cream markings like those of the females, since the cream-colored chromatophores are externally hidden by the ommochrome chromatophore layer. The content of sepiapterin in the males was about two times greater than that in the females. This quantitative difference in sepiapterin content between males and females suggests that the pteridine formation in this pigment cell may be regulated by hormones associated with sex determination.     

Defence function of pigmentocysts in the karyorelictid ciliate Loxodes striatus

The karyorelictid ciliate Loxodes striatus has pigment granules which are similar in size, structure and distribution to the pigmentocysts in the heterotrich ciliates, Blepharisma japonicum and Stentor coeruleus, which are known to be extrusomes for chemical defence against predators. We examined whether the pigment granules of L. striatus are also defensive organelles. We showed that: (1) pigment granules of L. striatus are extrusive organelles; (2) bleached cells of L. striatus produced by inducing a massive discharge of pigment granules are more vulnerable than normally pigmented cells to the raptorial ciliate Dileptus margaritifer and the turbellarian Stenostomum sphagnetorum, while they are indistinguishable from intact cells in external morphology and the capacity to grow; (3) the cell-free fluid (CFF) which contains the pigment discharged from pigment granules of L. striatus induced in D. margaritifer behavioural and pathological reactions which are essentially the same as those observed in the interaction with L. striatus, and this effect of the CFF disappeared when the pigment was bleached by light. We conclude that pigment granules of L. striatus are extrusomes for chemical defence against predators, and that the defence is based on the toxic pigment contained in these organelles.