A Study of the Structure and Gliding Movement of Gregarina garnhami

SYNOPSIS The structure and gliding movement of Gregarina garnhami Canning, a eugregarine found in the midgut of the desert locust, Schistocerca gregaria , have been studied by light microscopy and transmission and scanning electron microscopy (EM). Ultrastructural studies revealed that the cytoplasm of G. garnhami is separated from the epicyte folds by a basal lamina. The pellicle consists of 3 membrane layers. At the tips of the epicyte folds there are 2 sets of longitudinally oriented filaments. An ectoplasmic network is present in the ectoplasm and the endoplasm contains numerous paraglycogen granules. The effect of cytochalasin B on G. garnhami was studied. Examination of scanning EM preparations of gliding and stationary gregarines yielded inconclusive results. In some instances the epicyte folds were thrown into waves; in others the folds were straight, regardless of treatment before fixation. Gregarina garnhami glides through its environment without any apparent deformation in shape. As it moves, a mucus trail is left behind it. Phase-contrast observations were made of centrifuged gregarines in which the endoplasm was displaced. Centrifuged gregarines continued to glide. Displacement of the endoplasm allows visualization of the epicyte folds in gliding animals. No lateral waves were seen in the epicyte folds of gliding centrifuged animals.     

Scanning Electron Microscopy of Gregarines (Protozoa, Sporozoa) and Its Contribution to the Theory of Gregarine Movement

SYNOPSIS. Scanning electron microscopy was used to reveal detailed surface structure of 4 septate ( Gregarina cuneata, G. steini, G. rhyparobiae, Pileocephalus blaberae ) and one aseptate species ( Nematocystis elmassiani ) of eugregarines. The epicyte of all these gregarines is differentiated into a system of regular longitudinal folds. In the septate species these folds undulate so that these organisms glide along. The undulatory pattern is absent from Nematocystis , which does not glide. The theories and the mechanism of gregarine gliding are discussed.     

Trail‐following and trail‐searching behaviour in homing of the intertidal gastropod mollusc,Onchidium verruculatum

When uncovered by the tide, Onchidium verruculatum leaves its place of hiding, grazes on the rock surface, and thèn returns to its own home. Onchidium will follow its own mucus trail, most frequently towards the origin. This behaviour explains homing when the outward path is partly or completely retraced. Sometimes, however, homing occurs without contact with the outward trail. It was observed that trails were followed more closely at low humidities than at high humidities. No evidence was found for any method of orientation other than detection of chemical trials: when displaced onto sand Onchidium tend simply to crawl in a spiral until they contact their own trail. In addition to being a safe retreat, the home provides a fixed starting point to feeding excursions : this may facilitate re‐location of preferred feeding areas.     

Larval feeding behaviour of Tetanocera elata (Diptera: Sciomyzidae): potential biocontrol agent of pestiferous slugs

Examining predatory behaviour is useful for determining the potential of novel biocontrol agents. We investigated the predatory behaviour of Tetanocera elata (Fabricius) larvae on the pestiferous slug Deroceras reticulatum (Müller). Results indicate three prey-finding strategies, including the predator reaching its prey without previous contact with it or its mucus trail.     

The Three Cortical Membranes of the Gregarines (Parasitic Protozoa). III. Comparative Studies of the Membrane Proteins Among Different Sporozoan Species During Their Vegetative Phase1

ABSTRACT. The cortical membrane proteins of three gregarine and one coccidian species were compared using sodium dodecyl sulfate/polyacrylamide-gel electrophoresis. About 30 proteins were identified in the ghosts of Gregarina blaberae and G. garnhami and 20 in G. rhyparobiae ghosts and Sarcocystis tenella pellicles. No protein with the electrophoretic mobility of muscular actin was present in the ghosts of the sporozoan species under study. Each species possessed a characteristic electrophoretic pattern; no protein was present simultaneously in the four sporozoan species and only one protein band with a similar electrophoretic mobility was found in the three gregarine species (52 Kd protein). Two G. garnhami subpopulations living in Locusta migratoria and Schistocerca gregaria exhibited the same ghost protein pattern. Thus, large differences were observed between species and not within species, and the protein electrophoretic analysis appears to be a powerful tool for taxonomic investigations in gregarines. Gregarina blaberae and G. garnhami glycoconjugates were compared after periodate/Schiff staining of the polyacrylamide gel slabs. Several glycoconjugates were reported to belong to the cytoplasmic fraction; and, in view of cytochemical and ultrastructural data, a contribution of these glycocomponents to the secretion of a mucus is discussed.     

Etude de l'Ultrastructure de Gregarina polymorpha (Hamm.) en Syzygie

SYNOPSIS. The electron-microscope study of syzygy in Gregarina polymorpha , shows that this coupling, a prelude to cyst formation and to sexual phenomena, must not be considered as a simple pairing of individuals, but is rather the response of a gamont to a stimulus coming from another individual of a different sex. This response, in the species studied, can be recognized from the modifications that will appear progressively at the contact surfaces of the two gregarines. They affect only the protomerite apex of the posterior individual. There occur: rapid growth of the protomeritic epicyte; separation of this epicyte from the fibrillar zone underneath; formation of a protomeritic cup containing various inclusions; the disappearance of cuticular digitations and the formation of invaginations which become deeper and deeper.
All these modifications occur as soon as syzygy starts. They seem to indicate a reaction of the satellite epicyte to a possible stimulus coming from the anterior female gamont. This epicyte could play a different part from the initial one.
In the case of association between a primite and several satellites, the posterior gamonts react in a comparable manner but not together.     

L'Organisation Ultrastructurale Corticale de la Gregarine Lecudina pellucida; ses Rapports avec l'Alimentation et la Locomotion

SYNOPSIS. The structure of the cortical region (epicyte and ectoplasm) of the gregarine Lecudina pellucida , an intestinal parasite of the polychete worm Perinereis cultrifera was studied by electron microscopy.
The epicitary folds have 3 unit type membranes. Between the 1st and 2nd is a layer probably composed of fine longitudinal fibrils which has an arch-like or gutter-like structure at the crest of the folds. Inside these folds is cytoplasm without any noticeable differentiation or inclusion except for a granular (or finely fibrillar) layer under the limiting inner membrane and close to it.
The ectoplasmic zone of the entocyte is separated from the epicitary region by a lengthwise discontinuous cylindrical opaque layer, inwardly tangential to the folds. The ectoplasm lacks paraglycogen granules but has various organelles: apparently pinocytic vesicles against the wall between the folds, vesicles with myelinic membranes, opaque granules, a few mitochondria with blistered internal vesicles, and a few circular tubular fibers.
The superficial zone of the gregarine is supposed to contribute to nutrition, thru the extensive surface furnished by its folds and thru the pinocytic vesicles; but this alimentary intake is incomplete compared with that of the previously studied anterior region.
Insufficient mucus is discharged to account for locomotion. There are some circular ectoplasmic fibers, but locomotory myonemes are completely absent. However, there are deformations of the folds and corresponding waves that could account for locomotion by creeping or swimming. These movements of the folds might be due to the action of the contractile proteins and correspond with some of the layers seen in the wall.     

Trail-Following Behaviour in the Malacophagous Larvae of the Aquatic Sciomyzid Flies <Emphasis Type="Italic">Sepedon spinipes spinipes</Emphasis> and <Emphasis Type="Italic">Dictya montana</Emphasis>

The ability of neonate larvae of the aquatic sciomyzids, Sepedon spinipes spinipes (Scopoli) and Dictya montana Steyskal (Diptera), to follow snail mucus trails was assessed using filter paper Y-mazes. On finding a mucus trail, larval behaviour of both species switched from unstimulated to stimulated searching behaviour, the latter being characterised by an increase in larval velocity and the frequency of lateral head taps. When fresh mucus trails were used, all of the neonates displayed a positive response and followed the mucus trail into the experimental arm. In addition, for S. s. spinipes and D. montana 80.00% and 86.67% of larvae respectively exhibited a strong response and followed the trail to its end. The stimulatory substance (s), however, appears to become inactive with time and after 45 minutes none of the tested larvae reached the trail end. These results are discussed in relation to the ability of aquatic species to forage outside of water for prey and the implications for their use in the biological control of nuisance snails.     

Trail following behaviour in relation to pedal mucus production in the intertidal gastropod Monodonta labio (Linnaeus)

Trail following behaviour and pedal mucus production were investigated in the mid-shore topshell, Monodonta labio (Linnaeus) in Hong Kong. On the shore, individuals exhibited both conspecific and self trail following while awash on ebb and flood tides, although fidelity to resting sites during emersion on successive days was low. In the laboratory, animals that encountered trails that had been aged on the shore for different periods showed similar patterns of movement (distance moved, speed and tortuosity) suggesting that degradation of cues in the mucus that animals responded to did not occur until > 3 days post-deposition. Animals moved faster, with a lower rate of radular rasping, on freshly laid mucus trails than on a biofilm-covered substratum and did not change their speed when moving over aged (biofilm-covered) mucus compared to fresh mucus. Mucus production rates were similar when animals were crawling on vertical or horizontal surfaces, but significantly more mucus was produced when animals were emersed than when submerged. Mucus trail profiles were of variable thickness, but ‘double’ mucus trails (marker + tracker trails) did not contain significantly more mucus than ‘single’ trails (marker mucus only) and were considerably thinner than single trails suggesting tracker snails utilized mucus laid by marker snails, reducing their own deposition of mucus. Thus, while M. labio do not appear to utilize trails for orientation or refuge location, snails that follow trails have the potential to save energy through reducing mucus production or to gain energy through mucus ingestion. Given the role of pedal mucus production in the overall energy balance of gastropods, such energetic benefits are considerable and may have implications for the life history of the snail.     

Mucilage secretion and the movements of blue-green algae

Summary Recent discoveries of ultrastructures which might be involved in the gliding movements of blue-green algae have been reviewed, and in the light of these discoveries the role of mucilage secretion in movement has been reconsidered. The formation and behaviour of mucilage rings in filaments ofAnabaena cylindrica is described. The behaviour of the mucilage rings indicates that each cell has an autonomous gliding mechanism which is capable of immediate reversal, and that the gliding mechanism is probably located over the whole surface, rather than at the ends, of the cells. It follows that if mucilage secretion is the cause of movement it must take place over the whole surface of the cell: but if the ends of the cell are the sites of mucilage secretion, as seems likely, then gliding movement must be performed by some other process.A rather remarkable clumping phenomenon is described which takes place in dense suspensions ofAnabaena. It results from the gliding movements of randomly orientated filaments made mutually adhesive by the mucilage which surrounds them.     

Ovary,seed and fruit ofRutidea (Rubiaceae,Pavetteae)

The ovary ofRutidea is bicarpellate and incompletely bilocular (septum between locules not continuous). A solitary campylotropous ovule, ascending from a basal placenta, occurs in each locule. Based on their orientation and degree of curving, three ovule types are distinguished. As a consequence of the abortion of one ovule, the drupaceous fruits are one-seeded. The incomplete septum allows the spherical seed to fill out the entire interior of the fruit. The seeds are deeply ruminate (Spigelia type). They grow very fast, producing folds and undulations (ruminations) which invade and totally occupy the second locule, almost enveloping the aborted ovule. Comparisons with otherRubiaceae (especiallyPavetteae), show that hemianatropy and campylotropy occur more often in theRubiaceae than hitherto accepted. The study corroborates the close affinity betweenRutidea andNichallea.     

Ultrastructure of the taste disc in the red-bellied toad Bombina orientalis (Discoglossidae,Salientia)

The taste disc of the red-bellied toad Bombina orientalis (Discoglossidae) has been investigated by light and electron microscopy and compared with that of Rana pipiens (Ranidae). Unlike the frog, B. orientalis possesses a disc-shaped tongue that cannot be ejected for capture of prey. The taste discs are located on the top of fungiform papillae. They are smaller than those in Ranidae, and are not surrounded by a ring of ciliated cells. Ultrastructurally, five types of cells can be identified (mucus cells, wing cells, sensory cells, and both Merkel cell-like basal cells and undifferentiated basal cells). Mucus cells are the main secretory cells of the taste disc and occupy most of the surface area. Their basal processes do not synapse on nerve fibers. Wing cells have sheet-like apical processes and envelop the mucus cells. They contain lysosomes and multivesicular bodies. Two types of sensory cells reach the surface of the taste disc; apically, they are distinguished by either a brush-like arrangement of microvilli or a rod-like protrusion. They are invaginated into lateral folds of mucus cells and wing cells. In contrast to the situation in R. pipiens, sensory cells of B. orientalis do not contain dark secretory granules in the perinuclear region. Synaptic connections occur between sensory cells (presynaptic sites) and nerve fibers. Merkel cell-like basal cells do not synapse onto sensory cells, but synapse-like connections exist between Merkel cell-like basal cells (presynaptic site) and nerve fibers.     

The tenacity of the limpet, Patella vulgata L.: An experimental approach

It has been shown that adhesion of the limpet, Patella vulgata L. is influenced by both physical and physiological factors. The tenacity is sensitive to surface properties of the substratum, varying inversely with the contact angle which water makes with a substratum. This can be explained in terms of thermodynamics. Surface roughness also affects tenacity and this is explained in the same manner. Different angles of detachment were tested and it was clearly shown that when a strong peeling component was introduced, a much reduced force was needed to detach a limpet. Contrary to a normal pull, when a shear pull is exerted the force is not proportional to the surface area of the foot. It has also been shown that the speed of separation affects the measured tenacity; there is a speed at which tenacity will be maximum. The effect of water temperature on tenacity has been tested, tenacity increasing with rising temperature (7, 13, 20 °C). At the higher temperatures limpets are able to contract the foot muscles more powerfully, indicating that increased foot rigidity increases tenacity. By measuring the tenacity of limpets left out of water for different periods of time it has been shown that desiccation has no effect on tenacity, but a change from aquatic to aerial respiration increases tenacity. Tenacity has also been measured when the limpets have been subjected to a reduction in metabolic rate. The effect of both anoxia and narcotization shows that reduced muscle tonus, especially in the foot, results in decreased tenacity. These results further demonstrate that foot rigidity is essential for efficient adhesion. Eimpets from different habitats (exposed and sheltered) and vertical distribution (high and low level on shore) exhibited no differences in tenacity. During locomotion limpets leave a mucous trail, most of the mucus being confined to the edge of the trail. Water is incorporated anteriorly under each new locomotory wave and these pockets of water are used to release the mucus from the substratum during locomotion. It is concluded from this study that limpet adhesion can be explained solely by the tackiness of the pedal mucus, tack being due to the stored elastic energy within the mucous layer itself.     

Continuous observations of bacterial gliding motility in a dialysis microchamber: The effects of inhibitors

Use of a dialysis microchamber has allowed continuous observations on the same set of gliding bacteria during changes in the composition of the perfused medium. This procedure has revealed the presence of an adaptive, cyanide-insensitive metabolic pathway, which allows cyanide-treated Flexibacter BH3 to begin gliding again at a reduced rate when glucose is the substrate. In addition, it has revealed that individual flexibacter cells can maintain their gliding motility for up to 20 h in the absence of exogenous substrate.Gliding in Flexibacter BH3 was prevented by those inhibitors blocking the electron transport process. Inhibitors of glucose metabolism did not prevent motility, since the flexibacters obviously metabolize endogenous substrate under such circumstances. Proton ionophores, which induce membrane depolarization, rapidly inhibited gliding in Flexibacter BH3. This inhibition was irreversible in the case of gramicidin S. Gliding was not inhibited by cytochalasin B or antiactin antibody. High concentrations of Ca²⁺ were particularly inhibitory to the gliding process. The significance of these results is discussed in relation to a possible mechanism of gliding involving the generation of rhythmical contractions in the outer cell membrane of Flexibacter BH3.Abbreviations used CCCP carbonyl cyanide m-chlorophenyl hydrazone - DNP p-dinitrophenol - GMCS gramicidin S - HQNO 2-heptyl-4-hydroxyquinoline N-oxide - PCMB p-chloromercuribenzoate - CM complete Lewin's medium - BS Lewin's basal salts     

Use of terrestrial chemical trails for nest orientation in an open nesting wasp, <Emphasis Type="Italic">Dolichovespula saxonica</Emphasis> F.

Summary The long-cheeked wasp Dolichovespula saxonica typically constructs exposed nests which can be reached by flying. Usually foragers do not walk on substrates in the close vicinity of the nests as cavity breeding wasps do (Steinmetz et al., 2002). Unexpectedly, when forced to walk outside the nest instead of flying in an artificial tunnel system, D. saxonica foragers lay a terrestrial trail and use it for orientation in the nest area in our experiments. 41% of the foragers followed the trail in a direction they were not accustomed to. We suggest that the foragers have employed the same orientation cues normally used for orientation in the close vicinity of the nest when approaching a free-hanging nest by flying, for example nest odour. Nest odour substances may have been transferred to the substrate as a trail as a consequence of foragers walking through the tunnels.Received 23 August 2002; revised 27 January 2003; accepted 30 April 2003.     

Choroidal folds in association with optic disc drusen

Choroidal folds are undulations in Bruch's membrane, the retinal pigment epithelium and possibly the outer retina. They can result from any intra- or extraocular process that induces sufficient compressive stress within the choroid, Bruch's membrane and retina to force these tissues to buckle. Numerous ocular as well as systemic conditions have been associated with choroidal fold formation. Presented for discussion is a patient with unilateral choroidal folds and optic disc drusen. Arguments both for and against a direct association between the two conditions are made. Emphasis is placed on the differential diagnosis, clinical evaluation, etiology and management of choroidal folds.     

Mucus trail following by the snail Biomphalaria glabrata (Say)

An experimental procedure involving time-lapse cinematography was used to investigate the responses of the freshwater pulmonate, Biomphalaria glabrata (Say), to their mucus trails. It has been shown that individuals of this species are capable of following their own trails and also those laid by other individuals of the same species. The capacity of mucus trails to influence snail behaviour is lost after a brief period of between 10 and 30 min. The snails tend to move in the direction the trail was laid with expectation greater than by chance. They do not follow mucus trails laid by another species, Limnaea stagnalis. The possible adaptive significance of trail following is discussed.     

Partial characterisation of high-molecular weight glycoconjugates in the trail mucus of the freshwater pond snail Lymnaea stagnalis

We have studied the glycoconjugates in trail mucus of the pond snail Lymnaea stagnalis. The mucus was dissolved with 6 M guanidinium hydrochloride (GuHCl) and the major component was comprised of very high-M_r glycoconjugates that were eluted in the void volume of a Sepharose CL-4B gel-filtration column. This high-M_r material was pooled and thereafter subjected to density gradient centrifugation first in 4 M GuHCl/CsCl and subsequently 0.2 M GuHCl/CsCl to further remove non-glycosylated proteins and DNA. The harvested glycoconjugate pool chromatographed in the void volume of Sepharose CL-2B. However, reduction of disulfide bonds lowered the molecular size of approximately 80% of the void material yielding a major fragment and some minor smaller fragments in gel chromatography. The reduced glycoconjugates were digested with papain and yielded high molecular weight, proteinase-resistant glycopeptides. This fragmentation pattern is similar to that found for oligomeric gel-forming mucins in mammals and the amino acid composition (60% Ser/Thr) and sugar analysis of the glycopeptides is consistent with mucin-like molecules, there being no significant amounts of xylose or uronic acids. The residual 20% of the preparation, which apparently resisted reduction and protease digestion, had a similar amino acid composition to the bulk, but was somewhat different in sugar composition, containing some xylose and a significant amount of glucuronic acid. The two groups of molecules had very different morphologies in the electron microscope. Taken together, these data suggest that trail mucus is a complex mixture of at least two families of protein-glycoconjugate molecules based upon the gel-forming mucin and proteoglycan families, though we cannot rule out that polysaccharides may also be present.     

The trail of the african urticating antTetramorium aculeatum: Source,potency, and workers' behavior (Hymenoptera: Formicidae)

This paper studies the production of and the response to the trail in the African urticating ant,Tetramorium aculeatum under a variety of laboratory conditions. The trail was found to contain a complex mix of substances. Two of these components are secreted by the poison gland: The most volatile one is an attractant and increases the ants' linear speed; the other is the trail pheromone, which may act for days on a dry substrate. A third component is present on the last abdominal sternite. It acts as an attractant and a locostimulant and is synergistic of the trail pheromone. The activity of these substances increases with the age of the workers. While following a trail, foragers, even unrewarded, reinforce it with both the poison gland contents and the synergistic compound. The ants follow trails better in darkness than in light. A wetted trail rapidly loses its activity. The article suggests an explanation for the functioning ofT. aculeatum's natural trails, including the role of its different components.