Behavioral Responses to Changes in Hydrostatic Pressure and Light During Larval Development of the Lobster Homarus gammarus

1973 ◽  
Vol 30 (9) ◽  
pp. 1349-1360 ◽  
Author(s):  
G. P. Ennis
Keyword(s):  
Hydrostatic Pressure ◽  
Light Intensity ◽  
Average Rate ◽  
Stage Iv ◽  
Initial Response ◽  
Consistent Difference ◽  
Upward Movement ◽  
Downward Movement ◽  
Homarus Gammarus ◽  
Pressure Changes

Larvae of the lobster Homarus gammarus hatched and reared under laboratory conditions in shallow water responded to changes in hydrostatic pressure in a depth-regulatory manner. Responsiveness to instantaneous pressure increments ranging from 1 to 20 psi increased linearly and there was no threshold of sensitivity within the range tested. Pressure sensitivity was retained throughout larval life up to and including stage IV (megalopa) but responsiveness weakened with age at least up to stage III. Stage IV larvae were highly responsive to pressure changes but stage V (1st juvenile) lobsters were nonresponsive. Older larvae accommodated to sustained pressure more rapidly than younger larvae and larvae quickly became nonresponsive to repeated pressure changes. After being held at high pressure, larvae responded to slight pressure decreases by downward movement even though still held at pressures to which they would initially respond by vigorous upward movement. Larvae were more responsive to pressure in overhead light than in darkness but light intensity had no apparent effect on the initial response nor on the rate of accommodation to sustained pressure, but in darkness the initial response was slower. Responsiveness to sudden changes in light intensity was much less marked than to pressure changes and it also weakened with age. In the sea older larvae showed a stronger tendency for downward movement when released at the surface and a decreasing tendency for upward movement when released at depths of 25 ft (7.61 m) or more. The average rate of upward movement decreased over a 5-min period and there was no consistent difference in this rate or in the rate at which it decreased when larvae were released at different depths. The average rate of upward movement tended to decrease with age.

Behavioral Responses to Changes in Hydrostatic Pressure and Light During Larval Development of the Lobster Homarus americanus

1975 ◽  
Vol 32 (2) ◽  
pp. 271-281 ◽  
Author(s):  
G. P. Ennis
Keyword(s):  
Hydrostatic Pressure ◽  
Stage Iv ◽  
Homarus Americanus ◽  
Stage I ◽  
Upward Movement ◽  
Larval Life ◽  
Downward Movement ◽  
Vertical Movements ◽  
Instantaneous Pressure ◽  
Pressure Changes

Larvae of the lobster Homarus americanus hatched and reared under laboratory conditions in shallow water responded to changes in hydrostatic pressure in a depth-regulatory manner. Responsiveness to instantaneous pressure increments ranging from 1 to 20 psi increased linearly up to 10 psi but varied little at higher pressures. Sensitivity to pressure changes was retained throughout larval life up to and including stage IV (megalopa) but stage III and IV larvae were much less responsive than stage I and II. Stage V (1st juvenile) lobsters were nonresponsive to pressure changes. Larvae were much less responsive (in terms of vertical movements) to changes in light intensity than to changes in pressure, and there were no clear, sustained phototactic or photopathic responses in the vertical plane.In the sea, stage I, II, and III larvae showed limited downward movement when released at the surface and generally upward movement when released below the surface. Newly-molted stage IV larvae generally remained at the surface when released there and swam to the surface when released at the bottom; those 14–15 days after molting also tended to remain at the surface but when released at the bottom they generally remained there and found shelters. Newly-molted stage V juveniles generally remained where they were released, both at the surface and at the bottom, but those 13–15 days after molting when released at the surface generally swam to the bottom and found shelters, and when released at the bottom, remained there.

The Distribution of P O2 and Hydrostatic Pressure Changes Within the Branchial Chambers in Relation to GILL VENTILATION OF THE SHORE CRAB CARCINUS MAENAS L

1969 ◽  
Vol 51 (1) ◽  
pp. 203-220
Author(s):  
G. M. HUGHES ◽  
B. KNIGHTS ◽  
C. A. SCAMMELL
Keyword(s):  
Hydrostatic Pressure ◽  
Ventilation System ◽  
Carcinus Maenas ◽  
Pressure Change ◽  
Shore Crab ◽  
Positive Pressure ◽  
Transparent Plastic ◽  
Gill Lamellae ◽  
Minimum Disturbance ◽  
Pressure Changes

1. A technique is described for replacing part of the branchiostegite of Carcinus maenas by a transparent plastic ‘window’ for direct observation of the gills in situ with minimum disturbance. 2. Observation of dye streams shows that most water enters the hypobranchial space through the Milne-Edwards openings above the chelae, flowing anteriorly and/or posteriorly to ventilate most of gills 3-8. Water also enters above the pereiopods to ventilate the rest of the gills. Water passes from the hypobranchial to the epibranchial space, confirming that there is a counterflow with respect to the circulation of blood through the gill lamellae. 3. By sampling water at different points in the branchial system, patterns of oxygen removal were studied. The gradients confirmed the direction of water flow observed by the use of dyes. 4. Rhythmic changes in hydrostatic pressure in normal forward-pumping of 3-12 mm. H2O were recorded from the branchial cavities, superimposed on a maintained negative pressure relative to that outside the crab of 0-10 mm. H2O. Reversals produced a brief positive pressure change of 0-22 mm. H2O. 5. The possible relationships of the rhythmic pressure changes to scaphognathite movements are discussed. 6. The role of reversals is discussed and it is concluded that their primary function during ventilation is in helping to clean the ventrally facing gill surfaces. But they are also important in respiration under certain special conditions which arise during the normal life of the animal. 7. The utilization of O2 during its passage over the gills is low (7-23%) in spite of the counterflow. Possible explanations of this are discussed in relation to a model of the whole ventilation system.

Changes of Internal Hydrostatic Pressure and Body Shape in Acanthocephalus Ranae

1966 ◽  
Vol 45 (2) ◽  
pp. 197-202
Author(s):  
R. A. HAMMOND
Keyword(s):  
Hydrostatic Pressure ◽  
Internal Pressure ◽  
Body Length ◽  
Body Shape ◽  
Muscular Activity ◽  
The Body ◽  
Trunk Muscles ◽  
Rapid Rise ◽  
Indirect Methods ◽  
Pressure Changes

1. Two indirect methods for recording changes of hydrostatic pressure within the trunk of Acanthocephalus ranae have been described. 2. Internal pressure has been shown to be lowest when the trunk is fully contracted and the proboscis invaginated, and highest when the trunk is fully elongated. 3. A rapid rise of internal pressure occurs when the circular trunk muscles contract. 4. Overall internal pressure changes of up to 0.5 cm. Hg have been shown to occur in active specimens. 5. The body length when fully extended is only 40-50% greater than when contracted. 6. The correlation between muscular activity, body shape, and internal hydrostatic pressure in A. ranae is discussed

Some Aspects of Gas Exchange in Tuna

1972 ◽  
Vol 56 (3) ◽  
pp. 809-823
Author(s):  
E. D. STEVENS
Keyword(s):  
Hydrostatic Pressure ◽  
Gas Exchange ◽  
Oxygen Uptake ◽  
Average Rate ◽  
Oxygen Removal ◽  
Skipjack Tuna ◽  
Partial Pressure Of Oxygen ◽  
Free Swimming ◽  
Flow Rates ◽  
Theoretical Predictions

1. Some aspects of gas exchange in restrained skipjack tuna were analysed. 2. The average rate at which water flowed over the gills was 2.81/min. kg. 3. The concentration of oxygen in water entering and leaving the gills was measured and used to calculate oxygen uptake (692 mg/h.kg) and utilization (0.71). 4. The drop in hydrostatic pressure as water flowed over the gills was 1.9 cm water and agrees favourably with theoretical predictions. 5. The partial pressure of oxygen was measured in blood afferent and efferent to the gills and used to calculate effectiveness of oxygen removal from the water (90%) and the transfer factor for oxygen (0.12 ml/min.kg.mmHg). 6. The average utilization measured in free-swimming tuna was 0.56. 7. The extraordinary ability of tuna to efficiently extract oxygen from the water at high gill water flow rates is discussed.

Integration of Hydrostatic Pressure Information by Identified Interneurones in the Crab Carcinus maenas (L.); Long-Term Recordings

2001 ◽  
Vol 54 (1) ◽  
pp. 71-79 ◽  
Author(s):  
P. J. Fraser ◽  
A. G. Macdonald ◽  
S. F. Cruickshank ◽  
M. P. Schraner
Keyword(s):  
Hydrostatic Pressure ◽  
Gas Phase ◽  
Progress Monitoring ◽  
Carcinus Maenas ◽  
Shore Crab ◽  
Pressure Sensitive ◽  
Animal Navigation ◽  
Tidal Changes ◽  
Pressure Changes

This paper was first presented at the RIN97 Conference held in Oxford under the auspices of the Animal Navigation Special Interest Group, April 1997.Migrating species may utilise hydrostatic pressure. In the aquatic environment, hydrostatic pressure changes much more rapidly than in air. In shallow water, tidal changes will impose larger percentage changes on organisms than those experienced in deep water. Small changes in pressure often cause locomotion (barokinesis) accompanied by orientation to light or gravity, often partially compensating for the equivalent depth change. Until recently, identification of hydrostatic pressure receptors without a gas phase has proved elusive, but it is now known that thread hair receptors in the statocyst of the shore crab Carcinus maenas respond to small changes in hydrostatic pressure. Using a tide machine, the responses of thread hairs to sinusoidally changing pressure cycles have been examined, and this paper reports progress monitoring this receptor and making long-term recordings from hydrostatic pressure sensitive pathways in the crab's nervous system.

Chemotherapy-free interval following initial chemotherapy in patients with stage IV colorectal cancer

2009 ◽  
Vol 27 (15_suppl) ◽  
pp. e15096-e15096
Author(s):  
G. Melmed ◽  
C. Becerra ◽  
G. Saracino ◽  
E. Bowman ◽  
A. D. McCollum
Keyword(s):  
Colorectal Cancer ◽  
Medical Center ◽  
Financial Burden ◽  
Stage Iv ◽  
Progression Free Survival ◽  
Response Duration ◽  
Initial Response ◽  
Patient Characteristics ◽  
Health Care Economics ◽  
Free Interval

e15096 Background: Patients with metastatic colorectal cancer (mCRC) have improved survival due to recent advances in systemic therapy. It remains unclear whether patients responding to initial chemotherapy can be offered a chemotherapy free interval (CFI) without compromising survival. An initial CFI is potentially beneficial from a quality of life and health care economics standpoint. Methods: We studied patients with mCRC treated at Baylor University Medical Center (Dallas, TX) who had a CFI after first-line chemotherapy. Eligible patients had unresectable mCRC and had stable or responding disease after initial chemotherapy. Records were analyzed to record patient characteristics, chemotherapy details, initial response, duration of CFI, progression free survival (PFS), and overall survival (OS). Results: We identified 29 eligible patients treated between 11/02 and 11/08. Analyses are based on data from 8/08. Patient characteristics included: median age 63 (range 34–81), M/F 16/13, ECOG PS 0 (9) or 1 (20), and median number of sites of disease 2 (range 1–7). Initial chemotherapy regimens included mFOLFOX6 with or without bevacizumab (10), FOLFIRI/bevacizumab (12), XELOX/bevacizumab (2), 5-fluorouracil/leucovorin/bevacizumab (3), and capecitabine with or without bevacizumab (2). With a median follow-up of 31.1 months, the median duration of CFI was 8.0 months (95% CI: 4.3–9.6). In addition, the median OS was 33.7 months (95% CI: 27.8 -56.3) and PFS was 15.0 months (95% CI: 9.4–21.4). Conclusions: In this selected group of patients with mCRC, we found a CFI of 8 months. The OS nearing 34 months and PFS of 15 months compares favorably with other studies of patients treated for mCRC. An initial CFI may reduce the medical and financial burden of therapy for patients with mCRC without compromising outcomes and warrants further study. [Table: see text]

A cognitive approach to early conservatism

2014 ◽  
Vol 13 (2) ◽  
pp. 234-254 ◽  
Author(s):  
Pascal Fischer
Keyword(s):  
French Revolution ◽  
The Political ◽  
Upward Movement ◽  
Downward Movement ◽  
Cognitive Approach ◽  
Conceptual Metaphor Theory ◽  
Content Type ◽  
Metaphor Theory ◽  
George Lakoff ◽  
The One

Conservatism is notoriously difficult to define. In the present study, conceptual metaphor theory is used to elucidate the nature of this ideology in its early phase when it emerged in England as a force struggling with the ideas of the French Revolution. It can be shown that conservative authors frequently do not conform to the pattern of orientational metaphors described by George Lakoff and Mark Johnson (1980), according to which “up” is usually regarded as positive and “down” as negative. Conservatives often associate their own ideas with depth or a downward movement, whereas the loathed ideas of the political opponents are related to height or an upward movement. This dichotomy is closely connected to the polarity between solidity, stability and weight on the one hand and gaseity, volatility and lightness on the other. The study bases its analysis on numerous political tracts, pamphlets, and novels from the 1790s and early 1800s.

Observations on the Effects of Changes of Hydrostatic Pressure on the Behaviour of Some Marine Animals

1964 ◽  
Vol 44 (1) ◽  
pp. 163-175 ◽  
Author(s):  
A. L. Rice
Keyword(s):  
Hydrostatic Pressure ◽  
Experimental Method ◽  
Relative Importance ◽  
Marine Plankton ◽  
Marine Animals ◽  
The Hours ◽  
Gravity Receptors ◽  
Pressure Changes ◽  
Increased Activity ◽  
Increased Pressure

An apparatus and experimental method for the investigation of the effects of changes of pressure on the behaviour of marine animals is described.In 43 of a total of 53 species examined in this apparatus definite responses to abrupt pressure changes of 1000 millibars or less have been observed, increased pressure generally causing increased activity and movement upwards or towards the light, and decreased pressure causing decreased activity and movement downwards or away from the light. The relative importance of light and gravity in the orientation of these movements is generally correlated with the degree of development of the light and gravity receptors in the species concerned.The possible significance of these pressure responses in nature is discussed and it is suggested that pressure may be an important factor affecting the distribution of marine plankton, particularly during the hours of darkness.

scholarly journals Evidence of protandry in Aa Rchb.f. (Orchidaceae, Cranichideae)

Lankesteriana ◽  
2011 ◽  
Vol 11 (3) ◽  
Author(s):  
Delsy Trujillo ◽  
Thassilo Franke ◽  
Reinhard Agerer
Keyword(s):  
Cell Death ◽  
Developmental Stages ◽  
Ventral Side ◽  
Dorsal Side ◽  
Upward Movement ◽  
Downward Movement ◽  
Self Pollination ◽  
Flower Stage ◽  
Male Phase ◽  
Early Flower

Protandry has been described in orchids since Darwin (1862) as a strategy to promote cross-pollination. Three different forms of protandry have been reported in tribe Cranichideae: downward movement of the labellum in Spiranthes species, upward movement of the column in Sauroglossum elatum Lindl. and Manniella spp., and downward movement of the column in Prescottia stachyodes (Sw.) Lindl. In the present work, through longitudinal and transverse sections of flowers of different developmental stages, we reported column movement of Aa erosa (Rchb.f.) Schltr. and the mechanism responsible for the movement. Our result shows that in an early flower stage (male phase), the column of Aa erosa is straight. The gradual cell death of the dorsal side of the column and size increase of the cells of the ventral side cause the column to bend downward to almost 90o representing the female stage. Some authors have suggested self-pollination in Aa. But flies exploring inflorescences of Aa species have been observed in the field by the author. This observation plus the evidence of protandry in Aa erosa could discard self- pollination as the only strategy of pollination in this genus. 

The Responses of Nephtys (Polychaeta: Annelida) to Changes in Hydrostatic Pressure

1969 ◽  
Vol 50 (2) ◽  
pp. 501-513
Author(s):  
ELFED MORGAN
Keyword(s):  
Hydrostatic Pressure ◽  
Phase Angle ◽  
Pressure Change ◽  
Stimulus Level ◽  
Rate Of Change ◽  
Swimming Activity ◽  
Sine Function ◽  
Pressure Changes

1. An increase in pressure elicited swimming in Nephtys, the number of worms induced to swim being related to the amplitude of the pressure change within the range of stimuli investigated. A decrease in pressure inhibited swimming. 2. The latency of the response to both an increase and a decrease also appears to be related to the magnitude of the stimulus, the worms responding more rapidly to the bigger pressure changes. 3. Brief pulses of pressure lasting 1 sec. elicited neither increase nor decrease in the level of swimming, but pulses of 5 sec. duration induced some individuals to swim. Releasing the pressure at the end of the 5 sec. period resulted in a decrease in the swimming activity below the pre-stimulus level. It is suggested that the different responses may be mediated via separate receptor mechanisms. 4. Phase-angle analysis of the responses to cyclical changes in pressure suggested that the worms were responding primarily to the rate of change of pressure, but the response did not appear to be a simple sine-function of the stimulus. The worms also seemed to be responding in part to some component occurring at twice the basic cycle.

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