Structure of the auditory system of the weta Hemideina crassidens (Blanchard, 1851) (Orthoptera,Ensifera, Gryllacridoidea,Stenopelmatidae)

Summary This study of the ultrastructure of the auditory sensilla of the New Zealand weta, Hemideina crassidens, is the first such study on a member of the orthopteran Superfamily Gryllacridoidea. Ultrastructure of the auditory sensilla is similar in all of the tibial mechanosensory organs, here called subgenual organ, intermediate organ and crista acoustica by analogy with comparable structures in Tettigoniidae.Distal to each sensory soma is a dendrite containing multiple ciliary rootlets that fuse into a single ciliary root. This splits into nine root processes that pass around the outside of the proximal basal body and then rejoin at the level of the distal basal body, distal to which the dendrite has a modified ciliary structure with a circlet of nine peripheral paired tubes and rods as it passes through the proximal extracellular space. It is then enclosed by a zone of scolopale cell cytoplasm before expanding into a dilatation within the distal extracellular space. In some sensilla this space is partially occluded by electron dense material which is part of the scolopale cell. Distal to the dilatation the cilium shrinks and ends surrounded by the scolopale cap.Accessory cells consist of glia enwrapping the sensory neuron in the region of its soma, the scolopale cell surrounding the ciliary portion of the dendrite, and the attachment cell surrounding the scolopale cell and scolopale cap and connected to them by desmosomes. The attachment cells are filled with microtubules in differing densities and orientations. Lamellae are present in the acellular matrix surrounding the attachment cells. Banded fibres, presumably of collagen, are also present in the matrix.     

Light- and electron-microscopic analysis of the statocyst of the American crayfishOrconectes limosus (Crustacea,Decapoda)

Summary The statocyst ofOrconectes limosus contains static hairs arranged in four groups. All the hairs are the same in basic structure; they differ only in length and diameter and in their positions with respect to the other hairs in the group and to the statolith. In terms of functional morphology, each static hair is part of a unit consisting of an acellular lever string, three receptor cells, a scolopale cell, sheath cells, and enveloping cells. The lever string comprises two components in a characteristic longitudinal arrangement. The structure of the receptor cells resembles that of the arthropod chemo- and mechanoreceptors studied previously. The cilium and the postciliary section lie within two receptor cavities, formed by the scolopale cell and the sheath cells; the two cavities communicate with one another. The receptor cells are fixed in position by various structures. Proximally they form desmosomes with the scolopale cell, medially they are joined by filaments to the inner wall of cavity 1, and distally they are retained by a constriction between the two cavities. Two possible stimulus-mediating mechanisms are discussed: pressure changes in the receptor cavities and shearing of the base of the cilia with respect to the preciliary region. The lever string is part of the cuticle and hence is shed during molting. Nevertheless, the statocyst remains functional during this process because new structural units are formed below the old cuticle prior to ecdysis.Abbreviations a axon - b bulb - bb basal body - c cilium - cu cuticle - d dendrite - de desmosome - dm dense material - ec enveloping cell - f fulcrum - h hair - hs hair shaft - ir inner row of hair group - l lingula - ls lever string - m mitochondrion - n nucleus - or outer row of hair group - pcd postciliary dilation - R1 receptor cavity 1 - R2 receptor cavity 2 - rc receptor cell - ro rootlet - s sheath cell - sc scolopale cell - st statoconium - t tooth     

Femoral chordotonal organ in the legs of an insect,Chrysoperla carnea(Neuroptera)

The femoral chordotonal organ (FCO) inChrysoperla carneais situated in the distal part of the femur and consists of two scoloparia, which are fused at their distal end. The distal scoloparium contains 17-20 scolopidia, and the proximal one six scolopidia. Each scolopidium consists of two sensory cells and three types of enveloping cells (glial, scolopale and attachment cell). The sensory cells of different scolopidia do not lie at the same level in the FCO. Therefore the attachment cells of different scolopidia have different lengths. In the FCO, three types of ciliary roots are found in different sensory cells. The dendrite of the sensory cell terminates in a distal process, which has the structure of a modified cilium (9x2+0). The very distal part of the cilium is surrounded by an extracellular electron dense material, the cap, and ends in a terminal dilation. The scolopale cell contains the electron dense scolopale rods, consisting of plentiful microtubules. In their middle third the scolopale rods are fused and form the scolopale. In the FCO septate junctions, desmosomes and hemidesmosomes are found.     

东亚飞蝗Locusta migratoria manilensis（Mey．）膝下器中具橛感器的附属细胞和附属结构的超微结构

东亚飞蝗膝下器的具橛感器主要由三类细胞组成．即：感觉细胞、感橛细胞和冠细胞。感觉细胞为具橛感器的主要结构和功能细胞,其超微结构已在其他的文章中描述。感橛细胞是具橛感器的主要支持细胞,从近端到远端依次与神经胶质细胞、感觉细胞的远端树突部分和感觉纤毛部以及顶端细胞外结构——冠、冠细胞直接接触．感橛细胞内最明显的结构为感概,另外,感橛细胞质被高度“空化”。冠细胞紧密包围着感橛细胞和冠,冠细胞中含有大量的纵行微管．并将整个具橛感器连接到体壁上。     

The coelocapitular sensillum,an antennal hygro- and thermoreceptive sensillum of the honey bee,Apis mellifera L.

Summary The sensillum coelocapitulum, a hygro- and thermoreceptive sensillum of the honey bee, Apis mellifera, was investigated by electron microscopy. The cuticular apparatus of the sensillum is a mushroomshaped protrusion, devoid of pores, set in a narrow cylindrical pit positioned centrally within a cuticular, shallow depression. There may be three or four receptor cells. Three receptor cells have unbranched sensory cilia, containing densely packed microtubules, which extend distally into the cuticular apparatus and completely fill its cavity. These connecting cilia are of the usual 9+0 type. The fourth receptor, if present, has a thin sensory cilium which terminates beneath the cuticular apparatus. Its connecting cilium has armed outer doublets. The outer cavity is formed by two enveloping cells and is completely sealed off. Lipid deposits are present within the cavity and the tormogen cell. The thecogen cell has scolopale rod-like structures around the inner cavity. Features common to the insect hygro- and thermoreceptive sensilla are discussed in comparison with those of other insects.     

Structure of the subgenual organ in the green lacewing, Chrysoperla carnea

REM and TEM studies of the subgenual organ in Chrysoperla carnea (Neuroptera: Chrysopidae) show that it is composed of three scolopidia, each with one sensory, one scolopale and one cap cell. The distal part of the dendrite shows a cilium with a '9 + 0' structure. The cross-handing pattern of the ciliary root has a periodicity of bands of about 61 nm. The scolopale material in a certain part of the scolopale cell is organized into five rods. The cell bodies of all three cap cells form a lens-like structure. the velum, which is fixed to the leg wall and the trachea with an extracellular material. The importance of the velum is discussed. Four types of intercellular junction are found; spot desmosomes. belt desmosomes, septate junctions and gap junctions.     

Cytoskeletal modifications of the sensorimotor interneurons ofHydra vulgaris (Cnidaria,Hydrozoa), indicating a sensory function similar to chordotonal receptors of insects

Summary The battery mother cell complexes in the tentacles ofHydra vulgaris contain a neuronal cell known as sensorimotor interneuron that is characterized by a modified cilium lying parallel to the mesoglea. The cilium is surrounded by up to three rings of microvilli. Microvilli and cilium arise in an unusual antiparallel orientation from the opposite poles of a central cellular cavity. The lumen of this cavity communicates with the extracellular environment by way of a straight channel-like opening that is encircled by the microvillar rings. The modified cilium extends into the channel and terminates outside in the intercellular space. The wall of the cavity and the channel are stabilized by bundles of microtubules. A prominent glycocalyx interconnects all microvilli and links the innermost microvillar ring to the cilium. Within this contact region approximately 0.7 m in length the ciliary axoneme is specifically modified: all nine microtubule doublets and up to six additional microtubules are embedded in electron-dense material. The microtubule doublets are connected to the ciliary membrane by ledges of Y-shaped cross-bridging elements. These axonemal modifications resemble those known from the hydrozoan cnidocil complex or from the outer segments of insect mechanoreceptor cells. Distribution and orientation of the sensorimotor interneuron within the tentacles indicate a mechanosensory function of the cell similar to that of chordotonal receptors of insects.     

Fine structural studies of Johnston's organ in the tobacco hornworm moth,Manduca sexta (Johannson)

There are approximately 650 scolopidial units in Johnston's organ of the tobacco hornworm moth, Manduca sexta. These sensory units exhibit greater complexity than noted previously (Gray, '60; Howse, '65; Uga and Kuwabara, '65; Moeck, '68; Ong, '69; Schmidt, '69). Each scolopale is innervated by a bipolar neuron whose dendrite terminals are modified into three ciliary structures. The largest of these differentiates near the tip into a multitubular structure. The remaining two cilia are structurally similar along the entire length of the scolopale shaft. From each of their bases, a collagen-like structure differentiates into numerous microtubules which extend proximally into individual channels of dendritic cytoplasm. A third channel, with a less developed root apparatus, was apparent for the largest cilium. Preliminary evidence suggests a proprioceptive function for this structure rather than an auditory one.     

Ultrastructure of the sense receptors of adult Multicotyle purvisi (Trematoda, Aspidogastrea)

The following presumptive sense receptors of adult Multicotyle purvisi from the intestine of freshwater turtles in Malaya are described by transmission electron microscopy: disc-like receptor with many electron-dense collars and modified ciliary rootlet forming a 'disc'; non-ciliate receptor with long rootlet; non-ciliate receptor with branching rootlet and dense mass of irregularly arranged microtubules; non-ciliate receptor with rootlet fanning out from basal body, cross-striated in its upper and with electron-dense structures in its lower part; uniciliate receptor with thick layer of cytoplasm around axoneme; receptor with short cilium, at base of deep invagination of tegument; receptor with short cilium terminating in an electron-dense apical cap; and uniciliate receptor with long cilium. In addition, there may be a small non-ciliate receptor with a long ciliary rootlet at the base of the thick dorsal tegument, and uniciliate receptors differing from the uniciliate receptor with long cilium in the number of electron-dense collars and the length of the cilium and ciliary rootlet. Implications of the findings for the phylogeny of the parasitic Platyhelminthes and for evolutionary trends within that group arc discussed. The considerable degree of divergence of receptor types between the species of one family is attributed to the archaic nature of the group.     

The metathoracic wing-hinge chordotonal organ of an atympanate moth,Actias luna (Lepidoptera,Saturniidae): a light- and electron-microscopic study

Summary The structure of a simple chordotonal organ, the presumed homologue of the noctuoid moth tympanal organ, is described in the atympanate moth, Actias luna. The organ consists of a proximal scolopidial region and a distal strand, which attaches peripherally to the membranous cuticle ventral to the hindwing alula. The strand is composed of elongate, microtubule-rich cells encased in an extracellular connective tissue sheath. The scolopidial region houses three mononematic, monodynal scolopidia, each comprised of a sensory cell, scolopale cell, and attachment cell. The dendritic apex is octagonally shaped in transverse section, its inner membrane lined by a laminated structure reminiscent of the noctuoid tympanal organ collar. A 9+0-type cilium emerges from the dendritic apex, passes through both the scolopale lumen and cap, and terminates in an extracellular space distal to the latter. Proximal extensions of the attachment cell and distal prolongations of the scolopale cell surrounding the cap are joined by an elaborate desmosome, with which is associated an extensive electron-dense fibrillar plaque. Within the scolopale cell, this plaque constitutes the scolopale rod material. The data are discussed in terms of both the organ's potential function, and its significance as the evolutionary proto-type of the noctuoid moth ear.     

Asexual reproduction in the suctorianDiscophrya collini

Summary Discophrya collini reproduces asexually through the formation of a ciliated swarmer by evaginative budding. This process is initiated by the repeated replication of a single subcortical kinetosome to form a kinetosome field. The epiplasm of the multilayered cortex covering this field becomes reduced in thickness and the whole cortex invaginates to produce an internal embryonic cavity. The kinetosomes become organised into rows, and each produces a cilium which projects into the cavity. On completion of the embryonic cavity its walls are extruded through the cavity opening to form an external ciliated swarmer connected to the parent by a thin bridge of cytoplasm. It is suggested that this evagination is induced by a rapid breakdown of supporting microtubules in the cavity wall and the subsequent hydrostatic pressure exerted by the body cytoplasm. The connecting bridge shows no specialised ultrastructural features and separation of swarmer from parent probably is achieved by the active movement of the swarmer. The cytoplasm of the swarmer is similar in structure to that of the adult cell but contains a number of primordia of tentacle axonemes. The infraciliature resembles that of other suctorian swarmers. On settling, the cilia of the swarmer are lost, at least some by resorption, a stalk may be secreted and the axoneme primordia are extended to form functional tentacles.     

Microtubule reorganization,cell wall synthesis and establishment of the axis of elongation in regenerating protoplasts of the algaMougeotia

Summary Microtubule reorganization and cell wall deposition have been monitored during the first 30 hours of regeneration of protoplasts of the filamentous green algaMougeotia, using immunofluorescence microscopy to detect microtubules, and the cell-wall stain Tinopal LPW to detect the orientation of cell wall microfibrils. In the cylindrical cells of the alga, cortical microtubules lie in an ordered array, transverse to the long axis of the cells. In newly formed protoplasts, cortical microtubules exhibit some localized order, but within 1 hour microtubules become disordered. However, within 3 to 4 hours, microtubules are reorganized into a highly ordered, symmetrical array centered on two cortical foci. Cell wall synthesis is first detected during early microtubule reorganization. Oriented cell wall microfibrils, co-aligned with the microtubule array, appear subsequent to microtubule reorganization but before cell elongation begins. Most cells elongate in the period between 20 to 30 hours. Elongation is preceded by the aggregation of microtubules into a band intersecting both foci, and transverse to the incipient axis of elongation. The foci subsequently disappear, the microtubule band widens, and microfibrils are deposited in a band which is co-aligned with the band of microtubules. It is proposed that this band of microfibrils restricts lateral expansion of the cells and promotes elongation. Throughout the entire regeneration process inMougeotia, changes in microtubule organization precede and are paralleled by changes in cell wall organization. Protoplast regeneration inMougeotia is therefore a highly ordered process in which the orientation of the rapidly reorganized array of cortical microtubules establishes the future axis of elongation.     

THE FINE STRUCTURE OF COCKROACH CAMPANIFORM SENSILLA

Campaniform sensilla on cockroach legs provide a good model system for the study of mechanoreceptive sensory transduction. This paper describes the structure of campaniform sensilla on the cockroach tibia as revealed by light- and electron-microscopy. Campaniform sensilla are proprioceptive mechanoreceptors associated with the exoskeleton. The function of each sensillum centers around a single primary sense cell, a large bipolar neuron whose 40 µ-wide cell body is available for electrophysiological investigation with intracellular microelectrodes. Its axon travels to the central nervous system; its dendrite gives rise to a modified cilium which is associated with the cuticle. The tip of the 20 µ-long dendrite contains a basal body, from which arises a 9 + 0 connecting cilium. This cilium passes through a canal in the cuticle, and expands in diameter to become the sensory process, a membrane-limited bundle of 350–1000 parallel microtubules. The tip of the sensory process is firmly attached to a thin cap of exocuticle; mechanical depression of this cap, which probably occurs during walking movements, effectively stimulates the sensillum. The hypothesis is presented that the microtubules of the sensory process play an important role in mechanoelectric transduction in cockroach campaniform sensilla.     

Development of the ciliary complex and microtubules in the cells of rat subcommissural organ

Summary The fine structure of the rat subcommissural organs from the late stages of gestation through the postnatal to the adult stages was studied with the electron microscope. Emphasis in this report is placed on the development of the cilium with its affiliated structures. With the progress of cytodifferentiation centrioles originally located in the Golgi region migrate to the cell apex, where each then serves as a basal body to form a cilium which has a 9+2 organization of substructures. Thus, each of the mature subcommissural cells is provided with two cilia of motile type. Satellites first appear on one side of the basal body at about 17 fetal days, rapidly increase in number with age, and finally surround the basal body, forming an elaborate latticework. In the perinatal period microtubules progressively increase in number in the distal cytoplasm, which concurrently elongates and forms a prominent projection in the brain ventricle. Closely associated with the microtubules are large clusters of dense granular masses with an undefined border, which bear a close resemblance to the dense masses appearing in the differentiating cells of respiratory epithelium and having been generally assumed to be the precursor substance for centriole replication. However, the mature subcommissural cells contain no centrioles other than the preexisting pair, each of which has organized a cilium. The dense masses in the subcommissural cells are presumed to be involved in the formation of the cytoplasmic microtubules instead of new centrioles.Work supported by the National Science Council, the Republic of China, and by the China Medical Board of New York, Inc. A preliminary report was presented at the 6th International Congress for Electron Microscopy, Kyoto, 1966 (Lin, H.-S., andI-1. Chen: Satellites of the ciliary basal body and microtubules in the cells of the rat subcommissural organ. In: Electron Microscopy (R. Ueda, ed.) Vol. II, 461–462. Tokyo: Maruzen Co., Ltd. 1966).     

THE RELATIONSHIP BETWEEN THE FINE STRUCTURE AND DIRECTION OF BEAT IN GILL CILIA OF A LAMELLIBRANCH MOLLUSC

This paper describes the fine structure and its relationship to the direction of beat in four types of cilia on the gill of the fresh-water mussel Anodonta cataracta. The cilia contain nine outer, nine secondary, and two central fibers, such as have been described previously in other material. Each outer fiber is a doublet with one subfiber bearing arms. One particular pair of outer fibers (numbers 5 and 6) are joined together by a bridge. The two central fibers are enclosed by a central sheath; also present in this region is a single, small mid-fiber. The different groups of fibers are connected together by radial links that extend from the outer to the secondary fibers, and from the secondary fibers to the central sheath. The basal body consists of a cylinder of nine triplet fibers. Projecting from it on one side is a dense conical structure called the basal foot. The cylinder of outer fibers continues from the basal body into the cilium, passing through a complex transitional region in which five distinct changes of structure occur at different levels. There are two sets of fibers associated with the basal bodies: a pair of striated rootlets that extends from each basal body down into the cell, and a system of fine tubular fibers that runs parallel to the cell surface. The relationship between fine structure and direction of beat is the same in all four types of cilia examined. The plane of beat is perpendicular to the plane of the central fibers, with the effective stroke toward the bridge between outer fibers 5 and 6, and toward the foot on the basal body.     

Ultrastructure of a possible new type of crustacean cuticular strain receptor in Carcinus maenas (crustacea,decapoda)

A hitherto unknown sensillum type, the “intracuticular sensillum” was identified on the dactyls of the walking legs of the shore crab, Carcinus maenas. Each sensillum is innervated by two sensory cells with dendrites of “scolopidial” (type I) organization. The ciliary segment of the dendrite is 5–6 μm long and contains A-tubules with an electron-dense core and dynein arm-like protuberances; the terminal segment is characterized by densely packed microtubules. The outer dendritic segments pass through the endo- and exocuticle enclosed in a dendritic sheath and a cuticulax tube (canal), which is suspended inside a slit-shaped cavity by cuticular lamellae. The dendrites and the cavity terminate in a cupola-shaped invagination of the epicuticle. External cuticular structures are lacking. Three inner and four to six outer enveloping cells are associated with each intracuticular sensillum. The innermost enveloping cell contains a large scolopale that is connected to the ciliary rootlets inside the inner dendritic segments by desmosomes. Scolopale rods are present in enveloping cell 2. Since type I dendrites and a scolopale are regarded as modality-specific structures of mechanoreceptors, and since no supracuticular endorgan is present, the intracuticular sensilla likely are sensitive to cuticular strains. The intracuticular sensilla should be regarded as analogous to insect campaniform sensilla and arachnid slit sense organs.     

Surface fine structure of the subfornical organ in the Japanese quail,Coturnix coturnix japonica

The surface ultrastructure of the subfornical organ (SFO) was investigated in the Japanese quail. The SFO consists of a body and a stalk. The body of the SFO can be divided into rostral and caudal parts. On the rostral part, each ependymal cell possesses a short central solitary cilium; clustered cilia are also occasionally seen. Microvilli are abundant. On the caudal part, cells with a solitary cilium are fewer in number, and clustered cilia are rarely found. Microvilli are not as abundant as on the rostral part. In addition, large bulbous protrusions, tufts of small protrusions, deep funnel-shaped hollows, small pinocytotic invaginations and possible cerebrospinal fluid-contacting axons are sporadically observed on the surface of various regions of the body. Each ependymal cell of the stalk has a wide apical surface. A central solitary cilium, microvilli and other structures are observed more rarely on the stalk than on the body, while clustered cilia are not seen on the stalk. These structures are compared with those of the mammalian SFO and further discussed in relation to the possible dipsogenic receptor function for angiotensin II.     

An ultrastructural investigation of the hypocerebral organ of the adult Euperipatoides kanangrensis (Onychophora, Peripatopsidae)

The hypocerebral organs of Euperipatoides kanangrensis are a pair of spherical vesicles located ventral to the cerebral ganglia. They develop in the embryo from the most anterior pair of ventral organs, in the antennal segment. The wall of each hypocerebral organ is a dense epithelium of elongate cells with peripheral nuclei. The cytoplasm of the cells includes numerous mitochondria, Golgi bodies and microtubules. The small lumen, located eccentrically within the organ, contains concentrically layered electron-dense material resembling cuticle.Each hypocerebral organ is enclosed by a layer of extracellular matrix continuous with that surrounding the adjacent cerebral ganglion. There are no nerve connections between ganglion and organ, but cellular connections traverse the intervening matrix and could serve as a communication pathway. The ultrastructure of the hypocerebral organs indicates that they are glands.     

Fine structure of the dorsal bristle complex and pellicle of Euplotes

The fine structure of the dorsal bristle complex and pellicle of non-developing Euplotes eurystomus is described in detail by scanning and transmission electron microscopy. The bristle-pit unit is a highly differentiated complex of organelles. The bristle complex is composed of a pair of kinetosomes (basal bodies) joined by a connective. The anterior kinetosome bears the bristle cilium, which contains a polarized network of particles (“lasiosomes”). The posterior kinetosome bears a very short, knob-like “condylocilium,” and has an associated striated fiber. Accessory ribbons of microtubules are also associated with the kinetosome couplets. Parasomal sacs, a septum connecting the bristle cilium to the anterior wall of the pit, core granules of the kinetosomes, and large membranous ampules are described. The organization of the bristle complex bears many similarities to the somatic ciliature of other ciliates. The pellicle of Euplotes is composed of a continucus outer cell membrane subtended by membranous alveoli, which contain a “fibrous mat.” Two sheets of subpellicular microtubules (longitudinal and transverse) are located just beneath the alveoli. The “epiplasm” seen in some other ciliates is apparently absent in Euplotes. The texture of the cell surface is a pattern of folds or rugae composed of the outer cell membrane and the upper membrane of the alveolus. The pattern of rugae probably defines the “silverline-system” of light microscopy.