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PubMed1984

Sense organs of the nematodes Trichinella pseudospiralis Garkavi, 1972 and T. nativa Britov et Boev, 1972.

The structure and distribution of the sense organs of the head and the tail of two day-old Trichinella species (females) have been determined by transmission (TEM) and scanning (SEM) electron microscopy. In both species occur 16 cephalic sense organs, which contain three modified dendritic processes, in addition to the amphids. The nerve cell bodies are situated in the area above the nerve ring. The amphid contains ten dendritic processes. The sense organs open to the external environment by pores through the cuticle. Above the bulbous tip, the dendritic processes are surrounded by hypodermal cells. They enter posteriorly the pseudocoelom and join in subventral, subdorsal and two sublateral nerves, with transparent nuclei, in the area above the nerve ring. The distribution of the sense organs of larvae from the muscles and from the uterus is similar to that of the adults. The dendritic processes are short, most of their distal chamber is compacted with a dense, filamentous material. The rectum in the tail end of the female is innervated from the dorsal ganglion composed by multipolar cells with numerous dendrites and a single axon. Close to the excretory pore occurs a hemizonid which consists of six to eight dendrites and is situated between the hypodermis and the muscles. This organ has not been found in the larva.

Animals↗
PubMed1995

Genetic determinants of sense organ identity in Drosophila: regulatory interactions between cut and poxn.

Two genes involved in defining the type of sense organ have been identified in Drosophila. The gene cut differentiates the external sense organs (where it is expressed) from the chordotonal organs (where it is not); among the external sense organs poxn differentiates the poly-innervated organs (where it is expressed) from the mono-innervated organs (where it is not). Here we show that the expression of poxn in normal embryos does not depend on cut, and that poxn is capable of inducing the expression of cut. We have identified a small domain of the very large cut regulatory region as a likely target for activation by poxn.

Animals↗
PubMed1992

The paired box gene pox neuro: a determinant of poly-innervated sense organs in Drosophila.

This study describes the structure and function of pox neuro (poxn), a gene previously isolated by virtue of a conserved domain, the paired box, which it shares with the segmentation genes paired and gooseberry. Its expression pattern has been analyzed, particularly during development of the PNS. We propose that poxn is a "neuroblast identity" gene acting in both the PNS and the CNS on the basis of the following evidence. Its expression is restricted to four neuronal precursors in each hemisegment: two neuronal stem cells (neuroblasts) in the CNS, and two sensory mother cells (SMCs) in the PNS. The SMCs that express poxn produce the poly-innervated external sense organs of the larva. In poxn- embryos, poly-innervated sense organs are transformed into mono-innervated. Conversely, ectopic expression of poxn in embryos transformed with a heat-inducible poxn gene can switch mono-innervated to poly-innervated sense organs. Expression of poxn in the wing disc is restricted to the SMCs of the poly-innervated sense organs, suggesting that poxn also determines the lineage of poly-innervated adult sense organs.

Amino Acid Sequence↗
PubMed2000

Neuralized functions cell autonomously to regulate Drosophila sense organ development.

Neurogenic genes, including Notch and Delta, are thought to play important roles in regulating cell-cell interactions required for Drosophila sense organ development. To define the requirement of the neurogenic gene neuralized (neu) in this process, two independent neu alleles were used to generate mutant clones. We find that neu is required for determination of cell fates within the proneural cluster and that cells mutant for neu autonomously adopt neural fates when adjacent to wild-type cells. Furthermore, neu is required within the sense organ lineage to determine the fates of daughter cells and accessory cells. To gain insight into the mechanism by which neu functions, we used the GAL4/UAS system to express wild-type and epitope-tagged neu constructs. We show that Neu protein is localized primarily at the plasma membrane. We propose that the function of neu in sense organ development is to affect the ability of cells to receive Notch-Delta signals and thus modulate neurogenic activity that allows for the specification of non-neuronal cell fates in the sense organ.

Animals↗
PubMed1977

Sense organs on the antennal flagellum of psocids (Insecta, Psocoptera).

The sense organs on the antennal flagella of five species of winged psocids belonging to two families of Psocoptera, Psocidae and Leptopsocidae, have been examined, All agree in possessing tactile hairs, thick-walled chemoreceptors and long, porous chemoreceptors. Thin-walled chemoreceptors were identified in all species except Metylophorous novaescotiae. Coeloconic chemoreceptors were present in all species except Echmepteryx hageni. Campaniform sense organs were found only in Metylophorus novaescotiae and Psocus leidyi.

Animals↗
PubMed2000

Sense organ identity in the Drosophila antenna is specified by the expression of the proneural gene atonal.

We have shown that the basic helix-loop-helix transcription factor Atonal is sufficient for specification of one of the three subsets of olfactory sense organs on the Drosophila antenna. Misexpression of Atonal in all sensory precursors in the antennal disc results in their conversion to coeloconic sensilla. The mechanism by which specific sense organ fate is triggered remains unclear. We have shown that the homeodomain transcription factor Cut which acts in the chordotonal-external sense organ choice does not play a role in olfactory sense organ development. The expression of atonal in specific domains of the antennal disc is regulated by an interplay of the patterning genes, Hedgehog and Wingless, and Drosophila epidermal growth factor receptor pathway.

Animals↗
PubMed2003

Combinatorial expression of Prospero, Seven-up, and Elav identifies progenitor cell types during sense-organ differentiation in the Drosophila antenna.

The Drosophila antenna has a diversity of chemosensory organs within a single epidermal field. We have some idea from recent studies of how the three broad categories of sense-organs are specified at the level of progenitor choice. However, little is known about how cell fates within single sense-organs are specified. Selection of individual primary olfactory progenitors is followed by organization of groups of secondary progenitors, which divide in a specific order to form a differentiated sensillum. The combinatorial expression of Prospero Elav, and Seven-up allows us to distinguish three secondary progenitor fates. The lineages of these cells have been established by clonal analysis and marker distribution following mitosis. High Notch signaling and the exclusion of these markers identifies PIIa; this cell gives rise to the shaft and socket. The sheath/neuron lineage progenitor PIIb, expresses all three markers; upon division, Prospero asymmetrically segregates to the sheath cell. In the coeloconica, PIIb undergoes an additional division to produce glia. PIIc is present in multiinnervated sense-organs and divides to form neurons. An understanding of the lineage and development of olfactory sense-organs provides a handle for the analysis of how olfactory neurons acquire distinct terminal fates.

Animals↗
PubMed1994

Position-reading and the emergence of sense organ precursors in Drosophila.

Genetic analysis of development in Drosophila melanogaster has advanced our understanding of "position reading", where the expression of particular genes informs a cell of its position in the developing animal. The first step in localization of fly sense organs is the local expression of a gene conferring neural competence on epidermal cells. The four genes of the achaete-scute (AS-C) complex play crucial roles in the localization of sense organs. The resolution of local expression of AS-C genes along one dimension is about 10%; accuracy is improved by the balancing local expression of AS-C antagonist genes such as extramacrochaete. Position reading seems to depend primarily on such patterns of gene expression, and not upon the compartmental identity of the cells. No evidence has been found for differing roles of the four AS-C genes in the generation of sense organ progenitor cells or in the specification of neuronal properties of innervating neurons. The formation of each sense organ may be a unique case where the different proneural and neurogenic gene products have varying importance, and fortuitous local effects acting on this complex combination of factors have come to be important. The fly may be evolving from a flexible regular pattern to an inflexible irregular pattern strongly dependent on local factors, turning the fly into a crystallized system. (Written by R. Wayne Davies.).

Animals↗
PubMed2004

Reduction of brain and sense organs in the fossil insular bovid Myotragus.

Our study of the fossil rupicaprine bovid Myotragus [Bate, 1909] from the Mediterranean island Majorca (Spain) provides evidence that this animal underwent significant changes (reduction) in the relative size of brain and sense organs after geographic isolation at the end of the Messinian Salinity Crisis (Miocene-Pliocene boundary, 5.2 Mya). The changes in the central nervous system of Myotragus parallel the pattern reported for domesticated animals, in which decrease in relative brain size is accompanied by a decrease in the relative size of their sense organs. We interpret the important size reduction of brain and sense organs in Myotragus as an adaptive strategy for more efficient energy use under the special environmental conditions of the insular ecosystem, characterized by absence of predation and limitation of trophic resources.

Animals↗
PubMed1995

Specification of sense-organ identity by a Caenorhabditis elegans Pax-6 homologue.

The Pax-6 transcription-factor gene, containing a paired domain and a paired-type homeodomain, is conserved in structure and ubiquitously present among Metazoa. It is required for development of the central nervous system, and is mutated in human aniridia, mouse and rat small eye and Drosophila eyeless. We identified the Pax-6 gene of the nematode Caenorhabditis elegans in genetic studies of male tail morphology. C. elegans Pax-6 encodes at least two independent genetic functions. One, like other Pax-6 genes, contains paired and homeodomains; this constitutes the genetic locus vab-3. The other, described here, is expressed from an internal promoter and contains only the homeodomain portion; this constitutes the genetic locus mab-18. The mab-18 form of the gene is expressed in a peripheral sense organ and is necessary for specification of sense-organ identity. Its function in this context could be to regulate the expression of cell recognition and adhesion proteins required for sense-organ assembly.

Amino Acid Sequence↗
PubMed1991

The emergence of sense organs in the wing disc of Drosophila.

We have examined the origin of a set of precisely located sense organs in the notum and wing of Drosophila, in transformant flies where lacZ is expressed in the progenitor cells of the sense organs (the sensory mother cells) and in their progeny. Here we describe the temporal pattern of appearance and divisions of the sensory mother cells that will form the eleven macrochaetes and the two trichoid sensilla of the notum, and five campaniform sensilla on the wing blade. The complete pattern of sensory mother cells develops in a strict sequence that extends over most of the third larval instar and the first 10 h after puparium formation. The delay between the onset of lacZ expression and the first differentiative division ranges from 30 h, in the case of the earliest mother cells, to 2 h for the latest mother cells. The first division shows a preferential orientation which is also specific for each sensory mother cell. Up to this stage, there is no marked difference between the three types of mechanosensory organs.

Animals↗
PubMed1999

Dominant-negative mutation in the beta2 and beta6 proteasome subunit genes affect alternative cell fate decisions in the Drosophila sense organ lineage.

In Drosophila, dominant-negative mutations in the beta2 and beta6 proteasome catalytic subunit genes have been identified as dominant temperature-sensitive (DTS) mutations. At restrictive temperature, beta2 and beta6 DTS mutations confer lethality at the pupal stage. I investigate here the role of proteasome activity in regulating cell fate decisions in the sense organ lineage at the early pupal stage. Temperature-shift experiments in beta2 and beta6 DTS mutant pupae occasionally resulted in external sense organs with two sockets and no shaft. This double-socket phenotype was strongly enhanced in conditions in which Notch signaling was up-regulated. Furthermore, conditional overexpression of the beta6 dominant-negative mutant subunit led to shaft-to-socket and to neuron-to-sheath cell fate transformations, which are both usually associated with increased Notch signaling activity. Finally, expression of the beta6 dominant-negative mutant subunit led to the stabilization of an ectopically expressed nuclear form of Notch in imaginal wing discs. This study demonstrates that mutations affecting two distinct proteasome catalytic subunits affect two alternative cell fate decisions and enhance Notch signaling activity in the sense organ lineage. These findings raise the possibility that the proteasome targets an active form of the Notch receptor for degradation in Drosophila.

Animals↗
PubMed1983

Miniaturization and its effects on cranial morphology in plethodontid salamanders, genus Thorius (Amphibia, Plethodontidae): II. The fate of the brain and sense organs and their role in skull morphogenesis and evolution.

Relative size and arrangement of the brain and paired sense organs are examined in three species of Thorius, a genus of minute, terrestrial salamanders that are among the smallest extant tailed tetrapods. Analogous measurements of representative species of three related genera of larger tropical (Pseudoeurycea, Chiropterotriton) and temperate (Plethodon) salamanders are used to identify changes in gross morphology of the brain and sense organs that have accompanied the evolution of decreased head size in Thorius and their relation to associated changes in skull morphology. In adult Thorius, relative size (area measured in frontal plane, and length) of the eyes, otic capsules, and brain each is greater than in adults of all of the larger genera; relative size of the nasal capsules is unchanged or slightly smaller. Interspecific scaling phenomena--negative allometry of otic capsule, eye and brain size, isometry or slight positive allometry of nasal capsule size, all with respect to skull length--also are characteristic of intraspecific (ontogenetic) comparisons in both T. narisovalis and Pseudoeurycea goebeli. Predominance of the brain and eyes in Thorius results in greater contact and overlap among these structures and the nasal capsules in the anterior portion of the head. This is associated with anterior displacement of both the eyes and nasal capsules, which now protrude anterior to the skull proper; a change in eye shape; and medial deformation of anterior braincase walls. Posteriorly, predominance of the otic capsules has effected a reorientation of the jaw suspensorium to a fully vertical position that is correlated with the novel presence of a posteriorly directed squamosal process and shift in origin of the quadropectoralis muscle. Many of these changes in cranial morphology may be explained simply as results of mechanical (physical) interactions among the skeletal, nervous, and sensory components during head development at reduced size. This provides further evidence of the role of nervous, sensory, and other "soft" tissues in cranial skeletal morphogenesis, and reinforces the need to consider these tissues in analyses of skull evolution.

Animals↗
PubMed1999

Wingless signaling leads to an asymmetric response to decapentaplegic-dependent signaling during sense organ patterning on the notum of Drosophila melanogaster.

Wnt and Decapentaplegic cell signaling pathways act synergistically in their contribution to macrochaete (sense organ) patterning on the notum of Drosophila melanogaster. The Wingless-signaling pathway was ectopically activated by removing Shaggy activity (the homologue of vertebrate glycogen synthase kinase 3) in mosaics. Proneural activity is asymmetric within the Shaggy-deficient clone of cells and shows a fixed "polarity" with respect to body axis, independent of the precise location of the clone. This asymmetric response indicates the existence in the epithelium of a second signal, which we suggest is Decapentaplegic. Ectopic expression of Decapentaplegic induces extra macrochaetes only in cells which also receive the Wingless signal. Activation of Hedgehog signaling generates a long-range signal which can promote macrochaete formation in the Wingless activity domain. This signal depends upon decapentaplegic function. Autonomous activation of the Wingless signal response in cells causes them to attenuate or sequester this signal. Our results suggest a novel patterning mechanism which determines sense organ positioning in Drosophila.

Animals↗
PubMed1977

Observations on the lateral-line sense organs of the Salamander Neurergus crocatus crocatus Cope (Amphibia: Urodela).

The lateral-line system of the subadult and adult Neurergus crocatus crocatus Cope is retained throughout the life. It is constructed of pear-shaped sense organs or neuromasts which in the subadults are confined entirely to the epidermis with their apices opening distally to the exterior at the general level of the epidermal surface whereas in the adults they are embedded proximally more than halfway in the dermis with their distal apices opening into shallow grooves slightly below the regular epidermal surface. Dimensional differences are also observed between these organs in both stages. The neuromasts are constructed of 4 distinct cell types: sense cells, basal cells, sustentacular cells and mantle cells. These cells differ morphologically, structurally, topographically and functionally. The sense cells are clup-shaped, sensory, central in position and couched among the extremely elongated supporting basal and sustentacular cells, all of which are covered laterally by the extremely slender protective mantle cells. In both the mature and larvae, differences are observed among these cells in their size, number, location and arrangement. The sense organs are richly-supplied and well-nourished with vascular and nervous supplies.

Animals↗
PubMed1995

Transduction and adaptation in spider slit sense organ mechanoreceptors.

1. Mechanoreceptor neurons in spider (Cupiennlus salei) slit sense organ were examined by intracellular current- and voltageclarry recordings. Steps and pseudorandomly modulated displacement stimuli were delivered to the mechanosensitive cuticular slits. The resulting responses were used to determine the response dynamics and signal-to-noise ratio (SNR) of mechanoelectrical transduction. 2. Neurons were separated into two groups that, in terms of their afferent discharges, displayed different adaptations to displacement stimuli. Both responded at the onset of the step but then adapted fully, either immediately or within 10-200 ms. Voltage-clamp recordings showed only small differences in the receptor currents of the two groups. 3. Displacement of the slit caused a large inward current that decayed in seconds to a steady level of approximately 10-25% of the initial transient. When adapted to a steady displacement, the neurons responded to superimposed displacements in the same direction with additional transient currents, whose decay could be fitted by two exponentials with time constants of approximately 10 and 100 ms. In contrast, displacement in the opposite direction caused small "outward" currents without obvious adaptation. This behavior persisted with increasing background displacements, suggesting a shift in the displacement-response curve along the displacement axis. 4. White noise stimulation supported the step data and confirmed that the receptor's sensitivity was independent of mean slit membrane displacement. When the relative displacement of the stimulus (i.e., strain) was held constant at different maintained backgrounds, the SNR of the neurons remained fairly constant at approximately 2-10 over the frequency range from 4 to 450 Hz. The receptor current frequency responses showed high-pass characteristics, with a two- to sevenfold enhancement of the response amplitude and a phase lag relative to the stimulus of 90 degrees at 300 Hz. Low coherence values in the frequency range of 0.5-125 Hz were explained by nonlinear adaptation. 5. We conclude that, by rapidly adapting to the mean displacement of the slit membrane, slit organ mechanoreceptor neurons maintain a high sensitivity and SNR that allow the detection of small and rapid changes in cuticular strain.

Acoustic Stimulation↗
PubMed1977

On the ultrastructure of the abdominal sense organ of the giant scallop, Placopecten magellanicus (gmelin).

The abdominal sense organ of the giant scallop, Placopecten magellanicus, is composed of two cell types. The presumed receptor cells bear a single cilium 60 to 70 micrometer in length. The microvilli at the apices of these cells may also be modified into microvillous whorls. From eight to twelve ciliated cells are associated with a single mucous cell. The mucous cells have a much greater diameter than the ciliated cells and contain many electron-dense mucous granules. No function has yet been determined for the ciliated cells, although a number of theories are presented.

Abdomen↗
PubMed2006

Lyriform slit sense organs on the pedipalps and spinnerets of spiders.

Lyriform slits sense organs (LSSO) are a precise assembly of stress detecting cuticular slit sensilla found on the appendages of arachnids. While these structures on the legs of the wandering spider Cupennius salei are well studied in terms of morphology, function and contribution to behaviour, their distribution on pedipalps and spinnerets of spiders is not well explored. A study was therefore carried out to observe the distribution of LSSO on pedipalps and spinnerets of some spider species. Haplogyne spiders belonging to family Pholcidae have a simple complement of LSSOs represented by one or two LSSOs on their femur. The entelegyne spiders possess a complex assembly of LSSOs on the distal segments of their pedipalps. Various types of LSSOs are found on the pedipalps indicating a capacity for analysis of complex cuticular stress. It is suggested that the complexity of LSSOs on pedipalps of entel-egyne spiders relates to courtship and spermatophore transfer and may help in reproductive isolation. Lack of LSSOs on the distal segments of pedipalps leads us to infer that unlike legs, pedipalps are less likely to receive vibratory input through their distal segments. Spinnerets have a relatively simple complement of LSSOs. One LSSO is found only on anterior spinnerets and it is a common feature observed among spiders, irrespective of the variations in web building behaviour. The orb-weaving araneid Argiope pulchella, however, has two LSSOs on the anterior spinneret. As non-web builders and orb weavers do not differ markedly in terms of LSSOs on the spinnerets and LSSOs are simple in nature (type A), it is likely that spinning and weaving are not largely regulated by sensory input from LSSOs on the spinnerets.

Animals↗