Morphological studies on the periostracum of the fresh-water mussel Amblema (uniondae): Light microscopy, transmission electron microscopy, and scanning electron microscopy

The structure of the periostracum in the fresh-water mussel Amblema has been described using light microscopy, transmission elec;ron microscopy, and scanning electron microscopy. The structure and evolutive course of the periostracum was studied along its entire length, from the periostracal groove until it forms the tough outer covering of the shell. At least five structurally and functionally distinct regions were identified. In addition, the periostracum itself was seen to be a multilayered structure consisting of three major layers which are themselves subdivided into minor layers. From these morphological observations, a regulatory role for the various periostracal layers in mineral trapping, nucleation, and the subsequent formation of the prismatic and nacreous layers of the shell can be postulated.     

Morphological studies on the calcification process in the fresh-water mussel Amblema

Light microscopy, transmission electron microscopy, scanning electron microscopy, various histochemical procedures for the localization of mineral ions, and analytical electron microscopy have been used to investigate the mechanisms inherent at the mantle edge for shell formation and growth in Amblema plicata perplicata, Conrad. The multilayered periostracum, its component laminae formed from the epithelia lining either the periostracal groove or the outer mantle epithelium (of the periostracal cul de sac), appears to play the major regulatory and organizational role in the formation of the component mineralized layers of the shell. Thus, the inner layer of the periostracum traps and binds calcium and subsequently gives rise to matricial proteinaceous fibrils or lamellar extensions which serve as nucleation templates for the formation and orientation of the crystalline subunits (rhombs) in the forming nacreous layer. Simultaneously, the middle periostracal layer furnishes or provides the total ionic calcium pool and the matricial organization necessary for the production of the spherical subunits which pack the matricial ‘bags’ of the developing prismatic layer. The outer periostracal layer appears to be a supportive structure, possibly responsible for the mechanical deformations which occur in the other laminae of the periostracum. The functional differences in the various layers of the periostracum are related to peculiar morphological variables (foliations, vacuolizations, columns) inherent in the structure and course of this heterogeneous (morphologically and biochemically) unit. From this study, using the dynamic mantle edge as a morphological model system, we have been able to identify at least six interrelated events which culminate in the production of the mature mineralized shell layers (nacre, prisms) at the growing edge of this fresh-water mussel.     

Scanning electron microscopy of the electric tissue ofNarcine brasiliensis

The anatomy of electroplaques of Narcine brasiliensis has been studied by scanning electron microscopy. The ventral faces of the plaques are innervated with an abundance of branching nerves in close contact with the underlying (postsynaptic) membrane. Large numbers of troughs and evaginations of the postsynaptic membrane serve to increase its surface area. Fibroblasts are closely associated with the dorsal faces which appear covered with a matrix of fibrous material. Well-washed dorsal surfaces of single electroplaques are free of this matrix. The dorsal surface area is considerably increased by tubules extending into, and projections out of, the surface.     

黑翅土白蚁触角感器的扫描电镜观察

【目的】通过黑翅土白蚁Odontotermes fomosanus(Shiraki)幼蚁、工蚁、兵蚁触角感器种类、数量及分布的研究,分析不同龄幼蚁、工蚁和兵蚁的触角感器特征,为进一步研究触角感器发育特点及不同个体的行为分化机制提供参考。【方法】通过扫描电镜观察触角形态,分析触角节数、感器种类、数量及分布特征。【结果】工蚁、兵蚁、幼蚁个体触角长度差异显著,触角长度顺序:工蚁>兵蚁>3龄幼蚁>2龄幼蚁>1龄幼蚁;触角感器共有9种类型,分别为短毛形感器、长毛形感器、短刺形感器、长刺形感器、锥状B?hm氏鬃毛、球状钟形感器、刺突状钟形感器、球状钟形感器与刺突状钟形感器中间型、长刺具泡状感器。工蚁、兵蚁缺少长刺具泡状感器。幼蚁触角感器种类和数量随龄数而增加,1龄幼蚁具7种感器,缺少球状钟形感器和球状钟形感器与刺突状钟形感器中间型2种类型;2龄幼蚁具有8种感器,缺球状钟形感器;3龄幼蚁具有全部9种类型感器。【结论】黑翅土白蚁幼蚁、工蚁、兵蚁触角节数和感器显著差异,可作为幼蚁龄数以及非生殖品级判别的形态指标,应用于白蚁非生殖品级行为多型等相关研究。     

豆柄瘤蚜茧蜂触角感受器的扫描电镜观察(英文)

利用扫描电镜对豆柄瘤蚜茧蜂Lysiphlebus fabarum的触角感受器进行了观察, 发现有7 种感受器, 分别为毛形感受器、刺形感受器Ⅰ型、刺形感受器Ⅱ型、锥形感受器、腔锥形感受器Ⅰ型、腔锥形感受器Ⅱ型和板形感受器。毛形感受器是数量最多的感器; 除了腔锥形感受器Ⅱ型只在雌虫触角发现外, 雌、雄触角感受器的类型和结构没有较大的差别, 并且腔锥形感受器Ⅱ是数量最少的感器。     

Scanning electron microscopy of post-ejaculatory spermiogenesis in the tick Ornithodoros moubata

The final stages of spermiogenesis in ticks occur in the female genital tract. Scanning electron microscopy was used to follow the morphologic changes that occur in the sperm during this post-ejaculatory spermiogenesis in the African soft tick, Ornithodoros moubata, and to determine a time sequence for its occurrence in vivo. Characteristic features of the maturing and mature cell described include (1) differentiation and detachment of the operculum, (2) changes in cell shape corresponding to different developmental stages, (3) passive migration of the nucleus and acrosome from an anterior to a posterior position, and (4) eversion of that portion of the acrosomal canal containing the nucleus and acrosome. A possible fate for the remainder of the acrosomal canal is suggested by extrusion and detachment of spherical structures, the ‘posterior bubbles’, from the posterior end of the mature supermatozoon. A mechanism for cellular elongation resulting from contractions of the outer sheath is proposed.     

Scanning electron microscopy studies on the first-instar larva of Dermatobia hominis

Abstract. First-instar larvae of Dermatobia hominis collected 1, 4 and 7 days after having penetrated experimentally infected rats, were studied by scanning electron microscope (SEM) observation. On the pseudocephalon there are basiconic and trichoid sensilla (antennal sensory complex), and basiconic, coeloconic and campaniform sensilla (maxillary sensory complex). The thoracic segments bear several rows of small, backwardly pointed, spines, and trichoid, campaniform, coeloconic and pit sensilla. The anterior spiracle is a minute opening. Both small and large spines directed posteriorly are on the first to fourth abdominal segments, which also bear coeloconic and companiform sensilla. These sensilla are present on the unarmed (fifth and sixth) and armed (seventh) abdominal segments. The seventh and the last (eight) abdominal segments have forwardly directed spines. Each spiracular plate has two spiracular openings and four spatulate-like structures called sun rays. The anus and the coeloconic sensilla are proeminent on the last segment. The results are compared with other parasitic dipteran larvae, and emphasize that the multiple types of sensilla on D. hominis larva may have importance in establishing the parasitic phase of the life cycle of this insect.     

Scanning electron microscopy studies of cuticle micromorphology in Cycas L. (Cycadaceae)

Abstract

A scanning electron microscopy (SEM) study of Cycas cuticle characteristics was undertaken in order to expand our knowledge of microscopic characters not observable under light microscopy and to clarify unresolved affinitites among some species within the genus. Whole leaf and isolated cuticle specimens from the middle region of leaflets of greenhouse-grown plants of Cycas revoluta, Cycas rumphii, Cycas circinalis, Cycas media, and Cycas normanbyana were examined using SEM for interior and exterior features. Characteristics in common include hypostomy, hair bases on abaxial and adaxial surfaces, adaxial cells randomly arranged, adaxial exterior cuticle smooth, and stomata sunken to various degrees but stomatal pit always formed by two layers of epidermal cells. Stomatal complex is of the polyperigenous type. Stomata randomly dispersed and oriented, and except C. revoluta, are not contiguous. Stomata deeply sunken in C. revoluta, intermediate in C. rumphii and C. normanbyana, and less sunken in C. circinalis and C. media. Aperture between guard cells extends the entire stomatal length in C. rumphii and C. normanbyana, ～80% in C. circinalis and C. media, and ～50% in C. revoluta. Cuticular features of C. revoluta show the greatest difference from the other species in complex relief of exterior cuticle and interior cuticular structure of subsidiary cells; C. media and C. circinalis show close similarity to each other and their stomatal complex dimensions fall within the same unique cluster using principal component analysis under normalized variables. C. normanbyana and C. rumphii show the most similarity to each other in cuticular micromorphology. Stomatal complex dimensions of these two species fall into a second cluster that also includes C. revoluta. These data contrast with current taxonomy placing C. normanbyana synonymous to C. media.     

Scanning electron microscopy of glochidia and juveniles of the freshwater mussel,Hyriopsis myersiana

Summary

The ultrastructure of early stages of the mussel, Hyriopsis (Limnoscapha) myersiana (Lea, 1856), was observed by scanning electron microscopy from the glochidial period until the onset of the juvenile stage 10 days later. Further observations were performed for an additional 13 days to assess juvenile development. Glochidia extracted from the brood chambers have a hookless, semi-oval and equivalve calcareous shell with numerous pores in the internal surface, pits in the external surface and cuticular spines in the ventral region. Keratin fibers with a random arrangement in the cuticle of the glochidial shell were also detected. The appearance of the foot within 10 days of in vitro glochidial culture was considered the main feature of metamorphosis to the juvenile stage. Another change during the following 13 days was the formation of a new periostracum exhibiting growth lines under the old glochidial shell. This development occurs mainly in the anterior region and is followed by hardening of the periostracum matrix by calcium deposition. Periostracum growth gradually became apparent in the lateral and posterior regions at the end of this period. The retraction of spines and the alteration of the external surface of the old shell are also described. It is speculated that transcuticular filaments identified in the juvenile stage may have sensory or metabolic exchange functions. The prominent foot, gradually covered by long dense cilia, shows rhythmical movements which suggest a role in feeding. Similarly, cilia present in the mantle may also be involved in the capture of food, while microvilli may facilitate absorption of dissolved materials. Longer cilia, sparsely distributed in the mantle, may function as chemo- or tactile sensors.     

Scanning electron microscopy of trichomes of cheilanthes (sinopteridaceae)

Brittonia - The trichomes of two problematic complexes in the genusCheilanthes were studied. In one group, the trichomes ofC. tomentosa are long, multicellular, uniseriate, and flat whereas those...     

Scanning electron microscopy of the labia of Baylisascaris procyonis (Nematoda)

The labial organization of adult Baylisascaris procyonis was studied by scanning electron microscopy, and found to be similar for males and females. The apical part of each lip was smooth, and the basal part reticulated. The dorsal lip possessed two dorsolateral double papillae and two internal labial papillae; the two subventral lips each had one ventrolateral double and one externolateral papilla, two internal labial papillae, and an amphid. The small papilla of each double set was dome-shaped and smooth, whereas the large papilla was broad and had a prominent central pore. The externolateral papillae had raised, highly sculptured surfaces with numerous slits and creases present. Amphids resembled those of previously studied nematodes. The internal labial papillae consisted of pits. Denticles arose as a single row from the apical edge of the inner labial surface, were usually evenly spaced, and pyramidal or conoidal in shape. They were typically unicuspid, but bicuspid denticles were occasionally seen. Denticle shape and size varied between specimens and on each specimen. A pit was seen in the cuticle in the central region of the denticular row of all lips. Several of these findings represent new information concerning ascaridoid nematodes.     

Scanning and transmission electron microscopy of oral sucker papillae of Philophthalmus megalurus

Edwards H. H., Nollen P. M. &; Nadakavukaren M. J. 1977. Scanning and transmission electron microscopy of the oral sucker papillae of Philophthalmus megalurus. International Journal for Parasitology7: 429–437. Scanning electron microscopy reveals papillae on both the inside and outside of the oral sucker of the eyefluke, Philophthalmus megalurus. In the transmission electron microscope the papillae can be divided into 3 different types with 2 of these types occurring on the outside of the oral sucker. One type of outer papilla contains a bulb cell which is terminated by a cilium having an apparent typical arrangement of microtubules. This type is a presumed sensory receptor having tango- and/or rheoreceptor function. The second type of outer papilla contains a gland cell which secretes electron-dense granules to the outside of the fluke. The third type of papilla is found only on the inside of the oral sucker and contains a bulb cell terminated by a cilium which does not have the typical 9 + 2 arrangement of microtubules. Instead, their numbers increase to over 60 randomly arranged microtubules. This inner papilla is felt to have chemoreceptor function because of its location and the presence of the modified cilium. The bulb cell of the inner papilla contains 2 newly described features. The first is granular, and associated with microtubules; it may be a possible nucleating site for microtubule synthesis. The second structure is a crystalline inclusion of unknown function and origin.     

Scanning electron microscopy of the eggs of Palingenia longicauda (Olivier) (Ephemeroptera : Palingeniidae)

The eggs of Palingenia longicauda (Ephemeroptera : Palingeniidae) were studied by scanning electron microscopy (SEM), and showed a biconvex shape with the 2 aspects joined along a thick peripheral border. The eggs were completely wrapped by an exochorion that differs in thickness and organization according to the region of the chorionic surface. The thickest part of the exochorion formed a plaque, which also covered part of the peripheral border, and was constituted of a network of filaments. The remaining part of the exochorion was composed of a thin wrinkled sheet. The micropyle, hitherto unknown in Palingeniidae, appeared as a round opening penetrating into the plaque. The fibrillar network surrounding the micropyle dove-tailed with the egg chorion, forming a differentiated raised process. This peculiar interconnection facilitates egg anchoring to the substratum, and is an adaptation of the fibrous coat to the aquatic environment.     

双斑长跗萤叶甲触角感器的扫描电镜观察

利用扫描电镜观察了双斑长跗萤叶甲Monolepta hieroglyphica(Motschulsky)成虫触角及其感器的形态与分布。结果表明:双斑长跗萤叶甲成虫触角为线状,由柄节、梗节和鞭节组成,鞭节有9节,其中,雄虫的触角比雌虫长;感器类型有毛形感器(1型、2型和3型)、刺形感器、锥形感器(1型和2型)、腔锥形感器、Bhm氏鬃毛、钟形感器共9种。雌雄成虫触角感器类型无差异,但雄虫触角上的感器分布要比雌虫的稠密。     

Scanning electron microscopy studies of antennal sensilla of Monolepta hieroglyphica

利用扫描电镜观察了双斑长跗萤叶甲Monolepta hieroglyphica (Motschulsky)成虫触角及其感器的形态与分布.结果表明:双斑长跗萤叶甲成虫触角为线状,由柄节、梗节和鞭节组成,鞭节有9节,其中,雄虫的触角比雌虫长;感器类型有毛形感器(1型、2型和3型)、刺形感器、锥形感器(1型和2型)、腔锥形感器、B(o)hm氏鬃毛、钟形感器共9种.雌雄成虫触角感器类型无差异,但雄虫触角上的感器分布要比雌虫的稠密.     

Scanning electron microscopy (SEM) of the chick embryo primitive streak

The structure of the cells forming the primitive streak was examined by SEM in a series of embryos at Hamburger and Hamilton's stages 2--5. Specimens were prepared by stripping the endoderm from fresh embryos in New Culture and by fracturing whole fixed embryos along and at right angles to the primitive streak. At all stages of examination the SEM appearance of cells within the privitive streak was quite different from that of ectodermal, endodermal or mesodermal cells away from the streak. Streak cells were closely packed, lay with their long axes directed from ectoderm to endoderm and possessed many flat leaf-like processes. By contrast the ectoderm formed a columnar epithelium, the endoderm a flat epithelium and the mesoderm was a layer of loosely arrangedcells with long. thin processes. Within the streak SEM did not show any differences between cells that could identify them specifically as future endoderm or mesoderm cells. It was concluded that during gastrulation all the cells migrating through the primitive streak have the same appearance regardless of their eventual destination in the embryo. This structure may be attributable to the type of movement made by cells during invagination.     

Scanning electron microscopy studies of erythrocytes in Huntington's disease.

Scanning electron microscopic study of unmanipulated erythrocytes from Huntington's Disease (HD) patients disclosed an increased number of stomatocytes compared to controls. This morphological alteration may reflect a membrane abnormality and supports our previous electron spin resonance results (Butterfield $\text{et al}$, Nature (1977)$\text{267}$, 453–455) which suggests that HD may have diffuse membrane involvement.     

Scanning electron microscopy of Entomophthora virulenta and Conidiobolus coronatus (Entomophthorales: Entomophthoraceae)

The scanning electron microscope was used to delineate the morphological differences between Entomophthora virulenta and Conidiobolus coronatus isolated from field-infected cabbage and seedcorn maggots, Hylemya brassicae and H. platura. This SEM study supports the removal of C. coronatus from the genus Entomophthora on the basis of microconidial development and resting spores with villose appendages.     

拉步甲成虫触角感器的扫描电镜观察

利用扫描电子显微镜,观察了拉步甲Carabus lafossei成虫触角感器的类型、数量和分布规律。结果表明:拉步甲触角表面存在7类、12种感器类型,包括3种毛形感器(Sensilla trichodea,ST)、3种刺形感器(Sensilla chaetica,SCh)、2种锥形感器(Sensilla basiconca,SB)、Bhm氏鬃毛(Bhm bristles,BB)、腔锥形感器(Sensilla coeloconica,SCo)、腔形感器(Sensilla cavity,SCa)和钟形感器(Sensilla campaniformia,SCam),感器类型在雌、雄个体间无差异;雌、雄个体各节触角的感器数量和分布不均匀。研究结果为今后开展电生理学和行为生态学研究打下了基础。