Fine structure of aesthetasc chemoreceptors in the crayfish Orconectes propinquus

1986 ◽  
Vol 64 (2) ◽  
pp. 392-399 ◽  
Author(s):  
Ann Jane Tierney ◽  
C. S. Thompson ◽  
D. W. Dunham
Keyword(s):  
Distal Portion ◽  
Main Body ◽  
Decapod Crustaceans ◽  
Orconectes Propinquus ◽  
Outer Sheath ◽  
Apical Pore ◽  
Cell Layers ◽  
Chemical Stimuli ◽  
Sensory Endings ◽  
Sheath Cells

The outer antennular flagella of decapod crustaceans bear chemoreceptive hairs called aesthetascs. In the crayfish Orconectes propinquus these sensilla are located ventrally on the 11–13 most distal segments of the outer flagella. Two clumps of 3–6 aesthetascs occur on each segment, giving a total of approximately 80 aesthetascs per outer flagellum. Aesthetascs are100–150 μm long and about 12 μm in diameter. Each has a single annulation 30 μm from the hair base. The sensilla arise from immovable sockets and are directed distally at a 45° angle to the main body of the antennule. Aesthetascs lack an apical pore. However, the distal portion of each sensillum has thin cuticular walls which are readily penetrated by dye; this is probably the site where chemical stimuli enter. In O. propinquus each aesthetasc is innervated by 40–110 sensory neurons. Each neuron gives rise to a dendrite that branches into two cilia (9 × 2 + 2 structure; 0.15–0.20 μm in diameter). No further branching of outer dendritic segments occurs and thus each aesthetasc contains 80–220 sensory endings. Within the antennule lumen the dendrites are surrounded by two sheath cell layers, an inner layer and an outer layer. The inner sheath cells ascend 50 μm into the aesthetasc lumen; the outer sheath cells terminate at the sensilla bases. The outer dendritic segments gradually taper in diameter and terminate 25 μm from the sensilla tips.

Actin filaments in two spermatozoa of crustacea decapoda

1990 ◽  
Vol 48 (3) ◽  
pp. 70-71
Author(s):  
E. Dupré ◽  
G. Schatten
Keyword(s):  
Electron Microscopy ◽  
Actin Filaments ◽  
Low Voltage ◽  
Active Role ◽  
Main Body ◽  
Robinson Crusoe ◽  
Decapod Crustaceans ◽  
Actual Participation ◽  
Voltage Scanning ◽  
Scanning Electron

Sperm of decapod crustaceans are formed by a round or cup-shaped body, a complex acrosome and one a few appendages emerging from the main body. Although this sperm does not have motility, it has some components of the cytoskeleton like microtubules, which are found inside the appendages. Actin filaments have been found in the spike of penaeidae sperms. The actual participation of the crustacean decapod sperm cytoskeleton during fertilization is not well understood. Actin is supposed to play an active role in drawing the penaeidae shrimp sperm closer to the egg after bending of the spike. The present study was aimed at the localization of actin filaments in sperm of the Robinson Crusoe island lobster, Jasus frontalis and in the crayfish Orconectes propincus, by fluorescent probes and low voltage scanning electron microscopy.

scholarly journals THE ELECTRON MICROSCOPY OF THE HUMAN HAIR FOLLICLE

1957 ◽  
Vol 3 (2) ◽  
pp. 223-230 ◽  
Author(s):  
M. S. C. Birbeck ◽  
E. H. Mercer
Keyword(s):  
Hair Follicle ◽  
Cross Sections ◽  
Plasma Membranes ◽  
Membrane Complex ◽  
Outer Sheath ◽  
Root Sheath ◽  
Inner Root Sheath ◽  
Cell Layers ◽  
Adhesive Contacts ◽  
Similar Complex

1. The three cylinders of cells, each one cell thick, which together constitute the inner root sheath, arise from the peripheral portions of the undifferentiated matrix. These cells, like the hair cuticle, are stabilised by the spread of adhesive contacts between their plasma membranes which occurs in the mid-bulb and upper bulb of the hair follicle. 2. The characteristic intracellular product of all three cell layers is trichohyaline. This substance is formed in the first place as amorphous droplets which subsequently transform into a birefringent form. 3. This transformation, involving the formation of a birefringent product from an amorphous precursor, is in contrast to the formation in the cortex of keratin which originates in a fibrous form. 4. Trichohyaline appears first and transforms first in the cells of Henle which are nearest the outer sheath and the dermal supply vessels. This transformation occurs at the level of the neck of the follicle. Synthesis and transformation in the cells of Huxley and the sheath cuticle lag behind the similar events in the cells of Henle. The transformation does not begin until the lower prekeratinous zone in the Huxley and cuticle cells. 5. The amorpous-fibrous transformation occurs rapidly cell by cell and involves the conversion of all the trichohyaline droplets. In longitudinal sections the birefringent modification can be seen extending from the droplets in both directions parallel to the axis of the hair. In cross-sections the images of the transformed material are difficult to interpret. They may be seen as sections of corrugated sheets (∼100 A thick) or condensed fibrils ∼100 A in width. 6. At the same time that the trichohyaline transforms, the spacing between the cell membranes increases and a dark deposit appears centrally between them. This membrane complex, and the similar complex of the hair cuticle cells described in Part 2, may be specialised formations whose purpose is to hold the hardened cells together.

Fine structure of sensilla on the ovipositor of the tephritid fly Urophora affinis

1986 ◽  
Vol 64 (4) ◽  
pp. 973-984 ◽  
Author(s):  
R. Y. Zacharuk ◽  
R. M. K. W. Lee ◽  
D. E. Berube
Keyword(s):  
Fine Structure ◽  
Epidermal Cell ◽  
Fruit Flies ◽  
Sheath Cell ◽  
Outer Sheath ◽  
Dendritic Segment ◽  
Tubular Body ◽  
Tubular Bodies ◽  
Sheath Cells

There are four types of sensilla on the ovipositor blade of Urophora affinis Frauenfeld, one more than was observed on three other species of fruit flies studied by other authors. Three of the types, uniporous gustatory pegs, campaniform organs, and tactile short hairs are common to the four species and generally are in similar positions on the blade. The fourth, uniporous gustatory plates, were noted in U. affinis only. The chemosensilla are innervated by three chemosensory dendrites that terminate below the pore and a mechanosensory dendrite with a tubular body that is attached to a basal cuticular apodeme of the covering cuticle. The dendritic tubular bodies of the campaniform organs and tactile hairs terminate parallel to the surface in a right-angular bend, where they are attached to basal apodemes of the covering cuticle. The chemosensilla and tactile hairs have individual outer and inner sheath cells, but the campaniform organs have individual inner sheath cells only. The part of the ciliary dendritic segment that is encased by the dendritic sheath passes through an epidermal cell, often with several sensilla sharing the same epidermal cell in place of an outer sheath cell. The role of these sensilla during oviposition is discussed.

Coupling of Environmental and Endogenous Factors in the Control of Rhythmic Behaviour in Decapod Crustaceans

1997 ◽  
Vol 77 (1) ◽  
pp. 17-29 ◽  
Author(s):  
Hugo Aréchiga ◽  
Leonardo Rodríguez-Sosa
Keyword(s):  
Higher Order ◽  
Circadian Rhythmicity ◽  
Decapod Crustaceans ◽  
Endogenous Factors ◽  
Environmental Signals ◽  
Motor Responses ◽  
Behavioural Responses ◽  
Retinal Photoreceptors ◽  
Behavioural Patterns ◽  
Chemical Stimuli

Behavioural patterns of crustaceans are known to vary within the 24 hour cycle and in relation to environmental signals. Light and chemical stimuli induce specific behavioural responses. Retinal and extra-retinal photoreceptors use different motor responses to illumination selectively. Light responsiveness is modulated at various levels, from the light admittance to the retina, up to the integration in higher order interneurones and motorneurones. An endogenous circadian rhythmicity contributes to the various elements of the system.

Ultrastructural studies of ascospore liberation in Pyronema domesticum

1977 ◽  
Vol 55 (19) ◽  
pp. 2544-2549 ◽  
Author(s):  
Ching-Yuan Hung
Keyword(s):  
Single Unit ◽  
Spore Wall ◽  
Main Body ◽  
Large Vacuole ◽  
Ultrastructural Studies ◽  
Apical Pore ◽  
Total Disappearance

Ascospores of Pyronema domesticum contain three distinct spore wall layers. The liberation of ascospores presumably commences immediately after the three spore wall layers are formed. This is evidenced by the fact that vesiculation of the investing membrane was observed at the time when three wall layers could be distinguished. Vesiculation continues until the total disappearance of the perispore. Concurrently the epiplasm of the ascus degenerates and converts into a large vacuole within the ascus. Spores are violently ejected through the apical pore that is surrounded by a weakened apical ring. Presumably eight ascospores are discharged at the same time but do not adhere as a single unit. The operculum is generally not hinged to the main body of the ascus and an ascus without ascospores degenerates.

Ultrastructure of the aporous sensilla on the galea of larval Mamestra configurata (Walker) (Lepidoptera: Noctuidae)

1994 ◽  
Vol 72 (11) ◽  
pp. 2032-2054 ◽  
Author(s):  
Vonnie D. C. Shields
Keyword(s):  
Distal Portion ◽  
Sheath Cell ◽  
Mamestra Configurata ◽  
Bipolar Neuron ◽  
Campaniform Sensillum ◽  
Tubular Body ◽  
Lepidoptera Noctuidae ◽  
Sheath Cells

The galea of fifth-instar Bertha armyworms, Mamestra configurata, has three types of aporous sensilla: one spire-shaped basiconic peg, two short basiconic pegs, and one campaniform sensillum. The spire-shaped peg is set in an inflexible socket, innervated by three bipolar neurons, and enveloped by three sheath cells. One microtubule-laden dendrite completely fills the distal portion of the dendritic sheath and ends within the peg. It is joined by a lamellate and a scolopidium-like dendrite that end near and below the base of the peg, respectively. The ciliary sinus is large and the membrane of the enveloping inner sheath cell is highly elaborate. This sensillum exhibits features characteristic of thermo-hygrosensilla. The short basiconic pegs and campaniform sensillum are each innervated by a single bipolar neuron and each is associated with three sheath cells. In both sensilla, the dendrite ends in a tubular body, typical of mechanosensilla.

Sexual dimorphism in crayfish chelae: functional significance linked to reproductive activities

1976 ◽  
Vol 54 (2) ◽  
pp. 220-227 ◽  
Author(s):  
Roy A. Stein
Keyword(s):  
Sexual Dimorphism ◽  
Functional Significance ◽  
Dry Weight ◽  
Specific Interactions ◽  
Decapod Crustaceans ◽  
Predator Defense ◽  
Orconectes Propinquus ◽  
Sexual Encounters ◽  
Total Dry Weight ◽  
Reproductive Activities

Chelae of decapod crustaceans are massive structures that often make up 35–50% of their total dry weight. In most cambarid crayfishes, males have longer and heavier chelae than females. Important functions of chelae of Orconectes propinquus include (1) capture and manipulation of prey, (2) defense against predators, (3) inter- and intra-specific interactions, and (4) reproductive activities. In the laboratory, males with large chelae were more likely to survive predation, occupy positions of dominance, and copulate with females, than males with small chelae. However, chelae appeared most important for reproductive activities (male–male interaction for females as well as sexual bouts with females) and secondary for prey manipulation and defense. In sexual encounters, males used their chelae to grasp and hold females during copulation. Because males with large chelae could interact more successfully with larger more fecund females, these males may contribute proportionally more genes to future populations than males with small chelae. Consequently, selection should favor large chelae in males. Because size of chelae is reduced in nonmating males during summer, I hypothesize that large chelae are only essential for reproductive activities and not necessarily required for effective prey manipulation or predator defense.

Innervation of sheath cells of an insect sensillum by a bipolar type II neuron

1980 ◽  
Vol 58 (7) ◽  
pp. 1264-1276
Author(s):  
R. Y. Zacharuk
Keyword(s):  
Epidermal Cells ◽  
Type Ii ◽  
Outer Sheath ◽  
Bipolar Type ◽  
Dendritic Branches ◽  
Insect Sensillum ◽  
Dense Vesicles ◽  
Chemical Mediators ◽  
Type Ii Neuron ◽  
Sheath Cells

A multiterminal bipolar type II neuron is situated centrally in each mandible of an elaterid larva. It is ensheathed by a glial cell to the base of the two terminal scolopophorous sensilla in the terminal mandibular tooth but its terminal branches are naked. These branches extend along the outer surfaces of the inner and outer sheath cells of and the adjacent surfaces of the epidermal cells around both sensilla. The dendrite and its branches contain longitudinal microtubules, peripheral mitochondria, and clear and variously dense vesicles. It has no ciliary region. The dense vesicles are more numerous in newly molted than in intermolt larvae. Unique plates of endoplasmic reticulum and vesiculating bodies occur in the sheath and epidermal cells adjacent to the naked dendritic branches. This neuron may control the secretory activities of the sensillar sheath cells and adjacent epidermal cells through release of appropriate chemical mediators.

scholarly journals Migration and Keratinization of Cells in Wool Follicles

1980 ◽  
Vol 33 (5) ◽  
pp. 587 ◽  
Author(s):  
RE Chapman ◽  
AM Downes ◽  
PA Wilson
Keyword(s):  
Distal Part ◽  
Follicle Cells ◽  
Outer Root Sheath ◽  
Proximal Half ◽  
Outer Sheath ◽  
Root Sheath ◽  
Inner Root Sheath ◽  
Outer Root Sheath Cells ◽  
Migration Of Cells ◽  
Sheath Cells

Migration of' cells in wool follicles of an adult Merino sheep was studied autoradiographically in skin samples taken at intervals after an intravenous injection of [3Hjthymidine. Fibre arid inner root sheath cells incorporated [3Hjthymidine in a cone-shaped region of the follicle bulb. Labelled inner sheath cells migrated out of the bulb ahead of contemporaneous cells in the fibre and remained in advance, although to a progressively lesser extent, until the inner sheath cells sloughed into the follicle lumen. Outer root sheath cells incorporated [3Hjthymidine along the length of the follicle. Cells in the proximal half of the outer sheath migrated inwards and distally and sloughed into the follicle lumen before contemporaneous inner sheath cells. Other cells in the distal half of the outer sheath migrated past the level where cells from the proximal population were shed and also sloughed into the lumen. In the most distal part of the outer sheath, which formed the epidermis-like lining of the follicle canal, little migration of cells was observed during 8 days of observation.

The localization of nitrate-assimilating enzymes in leaves of plants with the C4-pathway of photosynthesis

1971 ◽  
Vol 49 (1) ◽  
pp. 137-142 ◽  
Author(s):  
Gary E. Mellor ◽  
E. B. Tregunna
Keyword(s):  
Glutamate Dehydrogenase ◽  
Nitrite Reductase ◽  
Nitrate Reduction ◽  
Bundle Sheath ◽  
Nitrate Content ◽  
Mesophyll Cells ◽  
Gomphrena Globosa ◽  
Bundle Sheath Cells ◽  
Cell Layers ◽  
Sheath Cells

The vascular bundle of leaves with the C4-pathway of photosynthesis is usually surrounded by two concentric chlorophyllous cell layers: an outer mesophyll layer and an inner bundle sheath layer. The localization of the nitrate-assimilating enzymes, nitrate reductase, nitrite reductase, and glutamate dehydrogenase in Zea mays, Gomphrena globosa, and Sorghum sudanense was studied by differential grinding. Nitrate reduction to nitrite appears to occur primarily in mesophyll cells. The nitrate content of the mesophyll cells was much higher than the nitrate content of the bundle sheath cells. The distribution of nitrite reductase seemed to be related to the presence of chloroplasts with grana. Ammonia incorporation into organic compounds by glutamate dehydrogenase was localized in the bundle sheath cells.

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