Thin Cuticle Research Articles

Elatides harrisii, sp. nov., from the lower cretaceous of liaoning, China

A new species of the taxodiaceous genus Elatides, E. harrisii sp. nov., is described from the Lower Cretaceous of Liaoning, China. Its leafy shoots bear helically disposed, almost straight leaves with thin, epistomatic cuticles; the leaves are four-angled in transverse section and have a large resin duct. The female cone is terminal and is composed of dorsiventrally flattened cone scales with a long, acuminate, free distal end, the cuticles of which are essentially similar to those of the leaves. The ligule has a toothead distal margin. The seed is fragmentary; it has a thin outer cuticle of the integument and three cutinised layers inside the stone. There is a well developed pollen chamber and the apex of the nucellus forms a beak-like projection. The male cones are enclosed by bracts which resemble the leaves in cuticular structur. There are 4–5 pollen sacs per scale and the pollen grains are monoporate when well developed. Elatides harrisii is one of the most completely known species of Elatides so far described and is compared in detail with the European species. Other published occurrences of the genus in China are summarized and discussed.

Gill Symbionts in Thyasirids and Other Bivalve Molluscs

Prokaryote organisms have been found in the gills of six species of Thyasiridae, collected in the north-east Atlantic region, from depths of 15 to 1250 m. The fine structure of the gill epithelia and the symbiotic Gram-negative bacteria is described. The bacteria occur extracellularly, between a thin cuticle and the apical membrane of the host cell. This differs from the intracellular position of bacterial symbionts in two lucinid species, Lucinoma borealis and Myrtea spinifera, and many other bivalves already known to harbour symbionts in their gills. Four species of Thyasiridae and Diplodonta rotundata, a member of the closely related family Ungulinidae, were found to lack gill symbionts.

Morphogenetic factors controlling differentiation and dedifferentiation of epidermal cells in the gynoecium of Catharanthus roseus

During postgenital fusion of the distal adaxial surfaces of the two originally separate carpel primordia of Catharanthus roseus (L.) G. Don, approx. 400 epidermal cells undergo rapid dedifferentiation into parenchymatous cells. To characterize the mechanism of the induction of dedifferentiation, various types of both water-permeable and water-impermeable barriers were placed between pre-fusion carpels. Barriers which did not allow the passage of water-soluble agents blocked dedifferentiation. Barriers which allowed passage of water-soluble agents did not block dedifferentiation of the contacting epidermal cells, implicating a diffusible agent or "morphogen" as the factor responsible for dedifferentiation. Experiments with barriers of known pore size demonstrated that the molecular weight of this morphogen was less than 1000. The two cell walls and thin cuticle present at the site of this postgenital fusion do not block the movement of some substances between the fusing carpels. Tracer studies with tritium-labeled asparagine confirmed that substances can be transported across the fusion plane.

Water permeability of plant cuticles: permeance, diffusion and partition coefficients

Using isolated cuticular membranes from ten woody and herbaceous plant species, permeance and diffusion coefficients for water were measured, and partition coefficients were calculated. The cuticular membranes of fruit had much higher permeance and diffusion coefficients than leaf cuticular membranes from either trees or herbs. Both diffusion and partition coefficients increased with increasing membrane thickness. Thin cuticles, therefore, tend to be better and more efficient water barriers than thick cuticles. We compared the diffusion coefficients and the water content of cuticles as calculated from transport measurements with those obtained from water vapor sorption. There is good to fair agreement for cuticular membranes with a low water content, but large discrepancies appear for polymer matrix membranes with high permeance. This is probably due to the fact that diffusion coefficients obtained from transport measurements on membranes with high permeance and water content are underestimated. Water permeabilities of polyethylene and polypropylene membranes are similar to those of leaf cuticular membranes. However, leaf cuticles have much lower diffusion coefficients and a much greater water content than these synthetic polymers. This suggests that cuticles are primarily mobility barriers as far as water transport is concerned.

Histology of adult Litomosoides carinii (Nematoda: Filarioidea).

The histology of male and female Litomosoides carinii was studied in serial sections. The body wall of the female worm consists of a rather thin cuticle, very extended lateral hypodermal chords and small sectors of shallow coelomyarian muscle cells. In the female worm an intestinal lumen is found, which is filled with material throughout the worm's length. Both ovaries are situated close to the posterior end. In both genital tubes all stages of oogenesis and embryogenesis could be observed in approximately equal stages of development in most of the sections. The lateral chords of the male worm are very small, whereas the somatic muscle cells are large and of the circomyarian type. The intestine is a minute tube beside the much thicker testis and vas deferens. Considerable sexual dimorphism could be observed in almost all organs of adult Litomosoides carinii.

The virgin bursa copulatrix of the butterfly, Calpodes

The different parts of the bursa copulatrix of virgin females of Calpodes ethlius have fine structures consistent with their different functions. The thin pitted cuticle of the bursal sac and its underlying epithelium suggest an absorptive function, with their ‘pores’ and numerous mitochondria respectively. The highly folded junctional region with its robust muscle and epithelium anchored to the thick folded spinous cuticle by sockets and their tonofibrillae suggest a holding structure capable of great muscular activity. The bursal duct with its hardened cuticle might serve to hold the body of the elongated, cone-shaped sperm sac straight and in position so that its contents might be more easily squeezed out into the seminal duct, whose opening is adjacent to the open end of the sperm sac.

Cyto-differenciation de la glande urticante de la chenille processionnaire du pin, Thaumetopoea pityocampa schiff. (Lepidoptera : Thaumetopoeidae) au cours de son developpement larvaire

The Thaumetopoea pityocampa (Lepidoptera : Thaumetopoeidae) caterpillar produces a contact dermatitis known as erucism. The urticating hairs are located on 8 abdominal “mirrors”. Histological and immunological methods were used to study cellular differentiation of the urticating gland during larval development. Trichogen cells form a cell cluster, the urticating gland, inside the thin cuticle of the “mirror”. This gland is present as early as in the 1 st instar and becomes thicker during larval development. Only in the 3rd instar does this gland begin to produce the urticating hairs. It is also at this time that the urticating protein, thaumetopoein, is synthesised by the gland.

The largest Cambrian animal, Anomalocaris , Burgess Shale, British-Columbia

Isolated specimens of the appendage Anomalocaris canadensis have long been known; a single incomplete specimen of an animal having a pair of these appendages attached anteriorly is described. Seven dorsoventrally compressed, partly complete individuals of a similar animal that had a different pair of appendages (‘F’ of Briggs 1979) attached anteriorly are described, together with two obliquely compressed individuals that are thought to be conspecific. Surrounding the mouth of this latter species is a circlet of plates identical with the supposed medusoid coelenterate Peytoia nathorsti ; this species is referred to Anomalocaris; Laggania is a junior synonym. As now understood, Anomalocaris was an animal that reached a length of 0.5 m, the elongate body having a head region bearing one pair of large, lateral eye lobes, each borne on a short stalk, the single pair of appendages attached at the ventral, anterior margin. The 13 segments of the appendage in A. canadensis bore paired spines on the inner side, short spines on the outer side, and there was a terminal, spinose 14th segment. The appendage in A. nathorsti consisted of 11 segments, the 2nd to 10th bearing on the inner side a graduated series of spinose blades, and spines on the lateral and outer sides, the terminal 11th segment ending in a group of spines. The circlet of plates surrounding the mouth was situated ventrally on the head region immediately behind the appendages; the plates bore teeth and the circlet constituted a jaw mechanism; additional groups of spines were present in the buccal cavity. Beneath the head region, behind the mouth, were three pairs of semicircular flaps, strongly overlapping: on the tapering trunk were 11 pairs of triangular lateral lobes, widest at the mid-length of the trunk, reduced progressively in size backward. These lobes were strongly overlapping in the same sense as the flaps on the head, and attached low on the sides. The trunk termination was short and blunt, without any projecting spine or lobe. Attached to the side of the body, above each flap and lateral lobe, was a multi-lamellar structure, apparently a gill. A thin cuticle covered the head region dorsally, and ventrally around the appendages and jaw circlet, behind this becoming a lateral strip that narrowed backward. It is suggested that a thin cuticle covered the trunk region dorsally and hung down beside the gills; this covering may have been continuous, but possibly was divided into tergites. Irregular patches of apatite, and some matrix, occur in the trace of the alimentary canal, which extended to the tip of the trunk. Mineralized patches occur in association with the gills, and as transverse strips, presumed traces of some internal organ or structure. The cuticle of the appendages and jaw circlet was presumably stout, hence these parts of the body were more resistant to decay and so were preserved in isolation. The thin cuticle of the lateral lobes shows rays which were presumably thicker and strengthening in function. We suggest that this animal, the largest known from Cambrian rocks, swam by using the series of closely spaced lateral lobes essentially as a lateral fin along which waves of motion were propagated. If the waves were moved in either the same, or opposite, sense on each side, considerable manoeuvrability would have resulted. The anterior pair of appendages, and jaw mechanism, would have made Anomalocaris a formidable predator, particularly on soft-bodied benthos including the abundant arthropods without a mineralized exoskeleton. No fragments of hard parts have been observed in the gut, but there is evidence that it may have inflicted wounds on trilobites. Anomalocaris was a metameric animal, and had one pair of jointed appendages and a unique circlet of jaw plates. We do not consider it an arthropod, but the representative of a hitherto unknown phylum. It is best known from A. nathorsti , the single specimen of A. canadensis having a different appendage but the rest of the body similar, probably including the jaw circlet. The evidence is insufficient to reach any conclusion on whether or not these two 'species' may be sexual dimorphs of a single species. The single specimen of Amiella ornata is redescribed. It shows what may be lateral lobes like those of Anomalcris, but other features unlike it. We conclude that this specimen is not an example of Sidneyia inexpectans , and is too incomplete for its relationship to be determined.

Host‐Parasite Relationship in a Susceptible and a Resistant Rose Cultivar Inoculated with Sphaerotheca pannosa: I. Fungal Growth, Mechanical Barriers and Hypersensitive Reaction

AbstractConidial germination and development of Sphaerotheca pannosa were studied on a susceptible and a resistant cultivar (rose Cardinal and rose Queen Elisabeth, respectively) in relation to the morphology of the leaf surface which was examined by scanning and transmission electron microscopy.Conidial germination was completed within 24 h in both cultivars and seemed to be higher in the resistant cultivar; fungal development, however, was stopped when the haustoria containing cells became necrotic.The only morphological difference between the leaves of the two cultivars is a thinner cuticle in rose Cardinal. Wax deposits on the leaf surface are similar; a layer of substances reacting to rhutenium red, most likely glycoproteins or protein‐polysaccharide complexes, also are similar.

THE POLLEN-STIGMA INTERACTION IN THE GRASSES. 7. POLLEN-TUBE GUIDANCE AND THE REGULATION OF TUBE NUMBER IN ZEA MAYS L.

SUMMARY The stigma of Zea mays can support the hydration and germination of considerable numbers of pollen grains, yet, in general, only one tube enters the micropyle to effect fertilisation. The numbers are reduced at various points in the pollen tube pathway, (1) by competition on the receptive trichomes and in the transmitting tracts, (2) by elimination of late-entering tubes at the stigma abscission zone, (3) at a constricted zone of the transmitting tracts in the upper ovary wall, and (4) in the vicinity of the micropyle. The control imposed at the abscission zone is higly effective. The entry of the first few tubes into the ovary wall induces a loss of turgidity of the cells of the zone and a disruption of the vasculation, and thereafter further tubes are irrevocably blocked in the main body of the stigma. The device maximises the period available for pollen capture and yet provides for the strict regulation of the number of tubes ultimately entering the ovary once pollination has taken place. Pollen tubes enter the ovary cavity by breaking through the inner epidermis of the ovary wall, which, like the contiguous inner integument, bears a thin discontinuous cuticle. Further passage is between the inner epidermis and the integument. Growth is irregular, but not wholly random, the tubes orienting themselves in the general direction of the micropyle following lines demarcated by the elongated cells of the epidermis and the integument. Almost throughout the pollen tube pathway, the cells in the vicinity show characteristics suggestive of a secretory function. The significance of this for pollen tube nutrition and guidance is briefly discussed.

IRON CRYSTALS IN THE ATTACHMENT ORGAN OF THE ERYTHROPHAGOUS COPEPOD CARDIODECTES MEDUSAEUS (PENNELLIDAE)

ABSTRACT The structure of the attachment organ of Cardiodectes medusaeus (Wilson) is examined by the use of light, scanning, and transmission electron microscopy. The entire attachment organ resides within the bulbus arteriosus of the host's heart. It is a syncytial mass measuring approximately 2 mm in diameter. The organ is covered by a thin cuticle. Transmission electron microscopy reveals a myriad of delicate microvilli projecting from the underlying cytoplasm to the inner surface of the cuticle. Nuclei, mitochondria, rough endoplasmic reticulum, free polyribosomes, autophagosomes, and Golgi apparatus are subcellular constituents of the organ. Large crystalline aggregates, dispersed throughout the cytoplasm, are visible with both light and electron microscopy. Prussian blue staining of the crystals indicates a high iron content. Ultrastructurally, the crystals are identical to ferritin, and function to detoxify and store iron obtained from blood meals. The role of the cytoplasmic organelles in digestion of blood and formation of iron crystals is examined. Because digestion of host erythrocytes, and synthesis and storage of ferritin occur within the attachment organ cytoplasm, the organ may be considered as an elaboration of the digestive tract.

Membrane specializations in the rectal papillae ofCeratitis capitata(Diptera)

Abstract The fine structure of the rectal ampulla of Ceratitis capitata has been studied with SEM, TEM and freeze-fracture techniques. The rectal papilla organization is that already seen in other advanced Diptera and comprises a cell cortical layer and a medullary cell complex. The former is lined by a thin cuticle showing small cavities which probably represent preferential sites for water uptake. The cytoplasm of the cortical cells is filled with stacks of infolded plasma membrane associated with mitochondria. At the level of these complex structures, scalariform and reticular septate junctions have been observed. Both these junctions seem to be implicated in the integrity of the intercellular space and of the stacked regions, thus facilitating the ion pumping through the stacks. The study also confirms the presence of a series of intercellular compartments (lateral dilatations; the sinus and the basal infundibulum) through which the water uptake is realized.

Development of the larval tunic in a compound ascidian: morphogenetic events in the embryos of Distaplia occidentalis

The larval tunic of Distaplia occidentalis is a complex investment consisting of extracellular filaments and an amorphous ground substance. The principal elements of the tunic are two thin cuticles and two subcuticular compartments. Compacted filaments and small amounts of ground substance characterize the cuticles. Dispersed filaments and large amounts of ground substance distinguish the compartments. The cells of the embryonic epidermis apparently secrete both the filaments and the ground substance. The elements of the larval tunic differentiate sequentially over a period of approximately 2 weeks. The outer cuticle appears 3–4 days after neurulation and it gradually lifts from the surface of the epidermis as the outer compartment forms. Tapered folds of the outer cuticle and extensions of the outer compartment produce the dorsal, ventral, and posterior fins of the larva. Test cells, occupying the perivitelline space around the embryo, release multigranular "ornaments" that adhere to the external surface of the outer cuticle. The inner cuticle and the inner compartment arise during the 4 days prior to hatching. The inner compartment over the truncal epidermis expands significantly to accommodate cells which emigrate from the body cavity (hemocoel).

'Campaniform' structures on lobster antennae are dermal glands.

The dome-shaped ('campaniform') cuticular structures found in small depressions on the lateral antennular flagella of the lobster (Homarus gammarus) were investigated by means of electron-microscopic methods. Each dome (diameter: 4-5 micron), which is surrounded by a 3-5 micron wide cuticular collar, is associated with a cell (soma size: long axis 90 micron, short axis 24 micron) showing fine-structural details characteristic of a dermal gland, e.g., a ductule lined by thin (cuticulin-like) cuticle and a well-developed granular endoplasmic reticulum. This ductule ends within the dome, which consists of spongious cuticle and, when seen from outside, resembles the cuticular cap of a typical campaniform sensillum of insects (Fig. 1 b). The fine-structural findings, especially the lack of any sensory element, are clear evidence against previous descriptions of these structures as representing 'campaniform sensilla of crustaceans'.

THE STRUCTURE OF THE PERICARP AND TESTA OF BARLEY

Detailed microscopic study of the covering layers of the mature barley grain shows that beneath the husk the pericarp consists of highly compressed cell material bound by a thin outer cuticle. The testa is a double cell layer, also bound by an outer cuticle. An innermost cuticular membrane separates the testa from the remains of the nucellus. This membrane is of nucellar origin and not part of the testa. The outer cuticle of the testa is incomplete in the ventral furrow and in the micropylar area of the grain. The absence of the testa cuticle and the relatively uncompressed nature of the pericarp at the micropyle may facilitate uptake of solutes by the embyro.

Catecholamines in haemolymph and cuticle during larval, pupal and adult development of Manduca sexta (L.)

Catecholamines in haemolymph and cuticle of the tobacco hornworm, Manduca sexta (L.), were analyzed by liquid chromatography with electrochemical detection. During pupal tanning, N- β-alanyldopamine (NBAD) was the major dopamine derivative in haemolymph. It increased to maximal titres by the time of larval-pupal ecdysis, and subsequently decreased as pupal cuticle tanned. NBAD progressively increased in cuticle for several days after ecdysis. N-acetyldopamine (NADA), although present in only minor amounts in pupae, was the primary catecholamine in haemolymph of both larvae and adults shortly before and after ecdysis. NADA predominated in the hard colourless cuticle of the larval head capsule, and in the wings and abdominal tergites of the adult. NBAD, however, was predominant in the dark cuticle of larval mandibles, and in the thin soft larval abdominal cuticle after stabilization. Dopamine, the precursor of NBAD and NADA, was usually the second or third most abundant catecholamine in both haemolymph and cuticle. The kinds of sclerotins produced may depend in part upon the relative abundance of the different catecholamines which are selectively incorporated into the various regions of the exoskeleton. The catecholamines in haemolymph occurred mainly as ring hydroxyl conjugates that were probably β-glucosides. The relative percentage of free or unconjugated compounds increased after ecdysis and accumulated in cuticle. Conjugation, therefore, appears to be important for sequestration of tanning precursors in haemolymph, followed by hydrolysis and uptake of free catecholamines for stabilization and pigmentation of new cuticle.

Epidermis structure in Mesembryanthemaceae

The Mesembryanthemaceae, which inhabit the deserts and semi-deserts of Southern Africa, exhibit two very different types of epidermis. The first is characterized by thick outer cell walls encrusted by oxalate crystals, a thick cuticle and thick wax layers. In the second type, the epidermal cells exhibit only very thin outer cell walls, not encrusted by oxalate crystals, a very thin cuticle, and wax layers are poorly developed; the most prominent feature of this type is the occurrence of huge idioblasts often protruding as ‘bladder cells’. With regard to the climatic conditions in the native habitats this type of epidermis must be called ‘abnormal’. Both types of epidermis may form sculptures of three distinct size classes, which are not necessarily homologous. The function of these sculptures is still poorly understood. There is evidence that the sculptures influence the optical properties of the surfaces and thereby the radiation balance (and heat stress) of the leaves.From recent research, it has become evident that the two different types of epidermis are the anatomical expression of two different strategies for survival under extreme conditions. Species with the idioblast type of epidermis exhibit a strategy that might be called ‘opportunistic’. These species have developed a mechanism of gaining water from the atmosphere during the night under favourable conditions. There are indications that the idioblasts are involved in this mechanism.

Structural features of the leaf epidermis of Halodule uninervis

Leaf blade epidermal cells of the marine angiosperm Halodule uninervis (Forssk.) Aschers resemble transfer cells since they possess a highly invaginated plasmalemma with which numerous mitochondria are often associated. However, wall ingrowths found in transfer cells of terrestrial plants are lacking. The plasmalemma is invaginated around fibrillar material which is not continuous with the cell walls and which appears to be structurally different from cell wall material. Epidermal cells possess an organelle-rich cytoplasm in which chloroplasts and electron-dense deposits feature prominently. The outer cell wall is about twice as thick as the other walls and seems to have a porous texture. A thin but distinct cuticle covers the leaf surface. Often minute cavities occur within the cuticle adjacent to the wall. Epiphytic algae and bacteria are frequently found in close association with the epidermis. Based on structural features, it would appear that leaf blade epidermal cells of H. uninervis play an important role in the leaf’s activities such as synthesis of carbohydrates, absorption and secretion of solutes and osmoregulation.

Branchial Water Movement in the Grapsid Crab Sesarma Reticulatum Say

Dehydrated Sesarma reticulatum first test water with their setose pereopods before immersing themselves in it. Water is then conducted from the substrate to the branchial chamber by capillary action of closely spaced plumed setae at the bases of pereopods 1-5. In contrast to the case of the ocypodid crabs Ocypode and Uca, there is no negative pressure in the branchial chamber to assist in water uptake. Branchial water flows out of the mouth primarily across the pterygostomial region of the branchiostegite where geniculate setae and pairs of cuticular ridges are present. The face of each ridge is covered by a thin cuticle beneath which is a pore opening to the spongy vascular epithelium of the dorsal branchial chamber. Staining with reduced methylene blue suggests that some gas exchange may occur across the cuticular ridges and that the spongy vascular epithelium may act as a lung. Stout comb setae on the medial surface of the cheliped clean the geniculate setae of the pterygostomial region. The morphology of the cuticular terraces of the lateral, dorsal surface of the carapace and the setae and ridges of the branchiostegal region both aid in returning water to the branchial

Pinus radiata needle studies: Fine structure of epidermal cells of the needle primordium.

Pinus radiata needle primordia were examined for ultrastructural features of their epidermal cells. Epidermal cells consisted of thin walls, a thin cuticle over the outer tangential wall, plasmodesmata in all except the outer tangential wall, moderately dense cytoplasm with poorly differentiated plastids, abundant mitochondria, dictyosomes and rough endoplasmic reticulum, cortical microtubules, and several small vacuoles. A prominent nucleus with often two or more nucleoli was characteristic of these cells.