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  • 1
    Electronic Resource
    Electronic Resource
    A fluid inclusion study of the porphyry-greisen, tungsten-molybdenum deposit at Mount Pleasant, New Brunswick, Canada (1985)
    Springer
    Mineralium deposita 20 (1985), S. 94-101 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Homogenization temperatures and salinity data are presented for fluid inclusions from hydrothermal gangue minerals (quartz and fluorite) associated with porphyry wolframite-molybdenite-arsenopyrite-sphaleritebismuth-chalcopyrite-cassiterite mineralization within the Fire Tower ore zone, Mt Pleasant, New Brunswick. The data indicate that ore mineral precipitation occurred within a temperature range of 260° to 490°C from moderate to high salinity (10–42 wt% NaCl equivalent) aqueous fluids. Two stages of hydrothermal activity characterized by high (〉30 wt% NaCl equivalent) salinity fluids are recognized; one which occurred at relatively high temperature (350°–490°C); and one which took place at lower temperature (180°–250°C). The high salinity, high temperature stage is interpreted to be the result of resurgent boiling. Dilution of these early fluids by convecting meteoric water resulted in low to moderate salinity fluids, which dominate the inclusion population. The low temperature, high salinity fluid inclusions are interpreted to represent late residual fluids derived from boiling which occurred as a result of a change in the pressure regime from dominantly lithostatic to hydrostatic conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00204317
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  • 2
    Electronic Resource
    Electronic Resource
    Selective and differential avoidance learning in the feeding and withdrawal behavior ofPleuobranchaea californica (1980)
    Springer
    Journal of comparative physiology 138 (1980), S. 157-165 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The marine gastropod molluskPleurobranchaea was avoidance conditioned by pairing food stimuli with conditional aversive electric shock. Yoked control specimens received explicitly unpaired food and shock in similar quantities to experimentals. All specimens were tested blind. 2. Experimental animals (N = 7) trained against squid homogenate (conditioned stimulus or CS) acquired an aversion to the squid, as evidenced by withdrawal from the CS (active avoidance learning; Fig. 1) and suppression of feeding behavior (passive avoidance learning; Figs. 2 and 3). The acquired aversion persisted for longer than 1 week, and was not displayed by control animals (N = 7). Statistically significant differences between experimentals and controls tested with squid were obtained in ten out of fifteen post-conditioning comparisons. 3. Experimental animals trained against squid homogenate, as well as control specimens in the same paradigm, showed a weak aversion to a homogenate of the sea anemoneCorynactis (Figs. 1–3). The difference between experimentals and controls when tested withCorynactis was statistically significant in only two out of fifteen comparisons, however. It may be concluded that the learned aversion was specific to the CS associated with shock (squid). 4. 42 specimens were subjected to modified differential avoidance conditioning, using various combinations of squid,Corynactis and shrimp as the CS+ (the food stimulus paired conditionally with shock) and CS− (the food stimulus not paired with shock). Differential avoidance learning, evidenced by a statiscally significant difference between responses to the CS+ and CS−, was evident in the withdrawal and feeding behaviors of individual animals, individual experiments on small groups of animals and in the aggregate data from all experiments (Figs. 4 and 5). 5. When data were categorized by the combination of stimuli used as the CS+ and CS−, the strongest differential learning was exhibited by the group in whichCorynactis served as the CS+ and squid as the CS− (Figs. 6–10). For certain combinations of food stimuli, differential learning was not obtained. 6. We conclude that the behavioral modification induced by avoidance conditioning ofPleurobran chaea's feeding and withdrawal behaviors is representative of genuine associative learning, and that the learned aversion is specific to the stimulus with which punishment is associated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00680439
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  • 3
    Electronic Resource
    Electronic Resource
    Chemoreception and mechanoreception in the gastropod molluscPleurobranchaea californica (1982)
    Springer
    Journal of comparative physiology 149 (1982), S. 221-234 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Sensory reception in the molluscPleurobranchaea californica was studied in whole animals and surgically reduced preparations by delivering chemical and mechanical stimuli while observing behavior or recording extracellularly the responses of the corresponding nerves. Sensory structures studied included the rhinophores, tentacles and oral veil. 2. Specimens reliably (50% or more) exhibited feeding responses to 10 of 18 amino acids tested (Table 1), including alanine and glycine. In 14 electrophysiological experiments on the rhinophore, medium to high centripetal responses to alanine and/or glycine were obtained in 7 preparations (Fig. 2), while little or no response was obtained in 7 preparations. Responses to different amino acids were sometimes mediated by the same centripetal unit (Fig. 2). 3. The rhinophore nerves showed vigorous excitatory responses to variations in the salt concentration (Figs. 3, 4), osmolarity (Figs. 5, 6), and pH (Figs. 7, 8) of sea water solutions directed onto the rhinophore sensory epithelium. The rhinophore and tentacle nerves showed strong excitatory responses to various salt solutions directed onto the corresponding sensory structure, including 1 osmolar NaCl, NaBr, NaI, Na2SO4 and KCl, but not LiCl (Table 2). Curves relating extracellular discharge to stimulus strength typically showed a minimum in the physiological range and increases to either side of this range (Figs. 4, 8). 4. All nerves studied showed excitatory responses to stimulation with mechanical stimuli (Figs. 9–11). Maps of receptive fields of different nerves (Fig. 10) delineated areas of functional innervation for each nerve and showed little overlap. The same centripetal unit(s) typically responded to mechanostimulation of a wide peripheral area (Fig. 11). 5. All nerves studied showed excitatory responses to application of liquefied food substances to the sensory structures (Figs. 12–15). Dose response curves for different food stimuli (Fig. 13) were similar except at higher stimulus strengths, where mean discharge rates were significantly different for different foods. These and other data furnish neurophysiological evidence for discrimination between different food stimuli, as suggested also by earlier behavioral studies (Davis et al. 1980). 6. For all stimuli, severing the afferent nerves leading from the peripheral sensory epithelium abolished electrophysiological responses. Therefore the responses observed were mediated by the sensory epithelium rather than by direct stimulation of peripheral ganglia or nerves. 7. It is concluded that the rhinophores, tentacles and oral veil participate not only in food detection but also have the sensory capacity to detect changes in several other environmental parameters. The data are consistent with the hypothesis that incoming afferent information is processed by peripheral ganglia before it is relayed centrally.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00619216
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  • 4
    Electronic Resource
    Electronic Resource
    Chemoreception and mechanoreception in the gastropod molluscPleurobranchaea californica (1982)
    Springer
    Journal of comparative physiology 149 (1982), S. 235-250 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Afferent chemosensory and mechanosensory pathways from peripheral sensory structures (the rhinophore and tentacle) to the cerebropleural ganglion (‘ brain ’) of the molluscPleurobranchaea were investigated using anatomical and electrophysiological methods. In both structures a sensory epithelium is connected by afferent nerves to a peripheral ganglion which sends a nerve (rhinophore or tentacle nerve) to the cerebropleural ganglion. 1. Filling the distal stumps of afferent nerves distal to the rhinophore and tentacle ganglia with cobaltous chloride (centrifugal fills of distal nerves) stained the somata of receptor cells in the sensory epithelium (Fig. 1), suggesting that primary afferent neurons project uninterrupted from the epithelium to the peripheral ganglia. 2. Filling proximal stumps of afferent nerves distal to the rhinophore and tentacle ganglia with cobaltous chloride (centripetal fills of distal nerves) stained mainly fiber tracts that terminated in the peripheral ganglia (Figs. 3, 5) suggesting that primary afferent input is processed mainly in these peripheral ganglia. 3. Filling distal stumps of nerves connecting the peripheral ganglia to the cerebropleural ganglion with cobaltous chloride (centrifugal fills of proximal nerves) stained approximately 100 somata in each peripheral ganglion but stained few axons in distal afferent nerves (Figs. 4, 5), suggesting that the rhinophore and tentacle nerves consist mainly of axons of interneurons arising in peripheral ganglia. Centripetal fills of proximal nerve stumps stained few (10–25) somata in the cerebropleural ganglion. 4. Transganglionic extracellular activity induced by extracellular stimulation of appropriate nerve roots was reversibly reduced in calcium-free sea water, indicating transmission of information across chemical synapses in the peripheral ganglia (Fig. 6). 5. Intracellular recordings were obtained from the somata of 79 interneurons in the tentacle and rhinophore ganglia while delivering sensory stimuli to the corresponding sensory structures. 53 cells showed reliably an action potential response to mechanical and/or chemical stimulation (Figs. 7, 9, 11–13, 15, 16, 18). The majority of cells were bimodal (mechano- and chemosensory), although monomodal (mechanosensory or chemosensory) cells were also encountered. In most cases (47/53) the response was excitatory, but in a few cases (6/53) inhibitory responses were obtained (Fig. 18). 6. Lucifer yellow injections were made for a representative number of such interneurons (Figs. 8, 10, 14, 17). Most of these showed monopolar neurons with a single axon passing from each soma into the rhinophore or tentacle nerve toward the cerebropleural ganglion, although injections of monomodal chemosensory interneurons (n = 2) revealed a bipolar configuration (Fig. 17). 7. The results collectively suggest that chemosensory and mechanosensory inputs from primary epithelial receptor cells of the rhinophore and tentacle are integrated in the peripheral ganglia and relayed to the central nervous system by a population of sensory interneurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00619217
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  • 5
    Electronic Resource
    Electronic Resource
    Motor program switching inPleurobranchaea (1981)
    Springer
    Journal of comparative physiology 145 (1981), S. 277-287 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The gastropod molluskPleurobranchaea performs at least two distinct cyclic behaviours using its buccal musculature, namely ingestion of food and egestion of unpalatable objects. The movements and motor programs underlying each of these behaviours have been characterized by cinematography and electromyography in intact specimens. A third buccal movement of unknown behavioural significance, is also described. 2. Both ingestion and egestion entail cyclic protraction and retraction of the radula within the buccal mass at slightly different cycle frequencies (Table 1). Cinematography has revealed three principal differences in the respective movements (Figs. 1, 2): 1) during egestion, the radula protraction phase of the movement cycle (the functional power stroke) is proportionately longer in duration than protraction during ingestion (the functional return stroke); 2) during the retraction phase of ingestion the radula is medially folded and rolls inward, while during the retraction phase of egestion the radula is flattened and does not roll inward; 3) during ingestion the jaws close near the end of retraction, while during egestion the jaws close near the beginning of retraction. 3. The functional morphology of the buccal musculature was studied anatomically (Fig. 3) and physiologically (Table 2). Attention was focussed on seven muscles, two radula retractors, two protractors, a buccal constrictor, jaw closer and lip retractor. 4. Electromyograms (EMG's) from five of these muscles were made during ingestion, egestion and the third, undefined rhythm. Ingestion and egestion are characterized by reliable differences in EMG activity which are consistent with observed differences in the movements (Figs. 4–6, Tables 3 and 4). The EMG differences during egestion include: 1) a relative increase in protractor muscle discharge (duration and intensity); 2) reduction or elimination of discharge in the buccal constrictor, a muscle which contributes to radular folding; 3) increase in the activity of lip retractor and jaw closer muscles; 4) a phase advance of the jaw closer muscle in the retraction phase of the cycle. The respective motor programs for the different behaviours are summarized in bar diagrams (Fig. 7). 5. The results are consistent with the hypothesis that ingestion and egestion employ the same basic central nervous oscillator and motor neurons, with distinctions between these behaviours caused by shifts in the balance of activity in different motor pools.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00605040
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  • 6
    Electronic Resource
    Electronic Resource
    Reciprocal inhibition between feeding and withdrawal behaviors inPleurobranchaea (1980)
    Springer
    Journal of comparative physiology 139 (1980), S. 77-86 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The interaction between two discrete behavioral acts, feeding and withdrawal from tactile stimulation, was examined in 32 specimens of the marine molluskPleurobranchaea. The experimental paradigm (Fig. 2) incorporated gradation of the intensity of the respective sensory stimuli for both behaviors over a wide range. 2. Withdrawal amplitude was suppressed during simultaneous feeding in individual animals (Figs. 5 and 7) and in grouped data from all 32 subjects (Fig. 9). The suppression of withdrawal was greater with increased feeding intensity (Fig. 9). 3. Feeding intensity declined during simultaneous withdrawal in individual animals (Figs. 6 and 8) and in grouped data from all subjects (Fig. 10). The suppression of feeding during withdrawal was greater with increased withdrawal intensity, and less with increased feeding intensity (Fig. 10). 4. It is concluded that feeding and withdrawal interact reciprocally rather than hierarchically, and a modified scheme for the overall organization ofPleurobranchaea's behavioral hierarchy is presented (Fig. 11). The findings are discussed from an evolutionary, ethological and neurophysiological view point.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00666197
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  • 7
    Electronic Resource
    Electronic Resource
    Motor program switching inPleurobranchaea (1982)
    Springer
    Journal of comparative physiology 147 (1982), S. 143-154 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Three distinct motor programs, namely ingestion, egestion and a third slower rhythm, have been identified in the buccal musculature of intact specimens of the gastropod molluscPleurobranchaea (Croll and Davis 1981). In the present study we have elicited each of these motor programs and characterized them in greater detail utilizing the technically more amenable reduced preparation, consisting of mouth, buccal mass, esophagus and attached central nervous system. 2. The ingestion motor program, rigorously identified by inward movement of objects placed in the buccal mass, is characterized by alternate bursts of activity in protractor and retractor muscles. The duration of the retraction phase of the cycle is longer than the duration of the protraction phase. The buccal constrictor muscle fires in phase with retractors. Salivary duct activity is in phase with protraction. In accordance with these muscle activities, the activity of buccal nerve root 3 is of longer duration and more intense than that of buccal root 1 during ingestion, and the salivary nerve is active in bursts during ingestion. The stomatogastric nerve fires cyclically in phase with retraction. 3. The egestion motor program, rigorously identified by outward movement of objects, is also characterized by alternate bursts of activity in protractor and retractor muscles. The egestion motor program differs from ingestion, however, in several specific respects. First, the duration of the protraction phase of the cycle is longer than the duration of the retraction phase. Second, the buccal constrictor muscle is silent during egestion. Third, the salivary duct is typically also silent during egestion. Fourth, the amplitude of recorded potentials from retractor muscles (m.1 and m.3) is significantly suppressed during egestion. Fifth, as would be expected, the activity of buccal nerve root 1 is longer and more intense than that of buccal root 3. Sixth, the salivary nerve is silent. Seventh, the stomatogastric nerve fires tonically rather than cyclically during egestion. 4. The ‘neutral’ or third buccal rhythm is generally significantly slower than ingestion or egestion, but is qualitatively similar in most respects to ingestion and dissimilar from egestion. 5. Stretching the esophagus induces the egestion motor program. This reflex is interpreted as a ‘clearance’ reflex which ensures egestion of objects too large to swallow. 6. Low-intensity stimulation of the stomatogastric nerve elicits a motor rhythm similar to ingestion but different from egestion. High-intensity stomatogastric nerve stimulation elicits the ingestion motor program, interrupted by stereotypic episodes of egestion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00609839
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  • 8
    Electronic Resource
    Electronic Resource
    Archaean subduction inferred from seismic images of a mantle suture in the Superior Province (1995)
    [s.l.] : Nature Publishing Group
    Nature 375 (1995), S. 670-674 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The Superior Province of Canada consists of an alternating sequence of granite-greenstone belts and metasedimentary sub-provinces that decrease in age from 3,100 Myr in the north to 2,650 Myr in the south (Fig. 1). This sequence probably arose through the amalgamation of ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/375670a0
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  • 9
    Electronic Resource
    Electronic Resource
    Behavioral suppression of head grooming in the male praying mantis during mating (1986)
    Springer
    Naturwissenschaften 73 (1986), S. 333-334 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00451486
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  • 10
    Electronic Resource
    Electronic Resource
    Paddle cilia (discocilia) in chemosensitive structures of the gastropod mollusk Pleurobranchaea californica (1982)
    Springer
    Cell & tissue research 222 (1982), S. 25-40 
    Details
    ISSN: 1432-0878
    Keywords: Paddle cilia ; Discocilia ; Pleurobranchaea ; Chemoreceptors ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Scanning electron microscopy of various regions of the body of the marine gastropod Pleurobranchaea californica (McFarland) has revealed a characteristic cell type that bears cilia with dilated discoid-shaped tips. The tips of the cilia consist of an expansion of the ciliary membrane around a looped distal extension of the axoneme. These kinocilia have been observed in numerous other marine invertebrates and are generally referred to as paddle cilia (Tamarin et al. 1974) or discocilia (Heimler 1978). Although many functions have been proposed for paddle cilia, little empirical evidence supports any of the proposals. In Pleurobranchaea we have found that the distribution of this ciliated cell type corresponds exactly to areas of the body known from behavioral studies (Lee et al. 1974; Davis and Matera 1981) to mediate chemoreception. Transmission electron microscopy of the epithelium lining the rhinophores and tentacles of Pleurobranchaea revealed details of the ultrastructure of these ciliated cells and showed that they are primary receptors. These ciliated receptors lie in a yellow-brown pseudostratified columnar epithelium that superficially resembles the olfactory mucosa of vertebrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00218286
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