�ber den Feinbau der Chorda dorsalis von Branchiostoma lanceolatum

1968 ◽  
Vol 87 (1) ◽  
pp. 69-81 ◽  
Author(s):  
Ulrich Welsch
Keyword(s):  
Branchiostoma Lanceolatum ◽  
Chorda Dorsalis

The effects of lowered salinity upon Branchiostoma lanceolatum from the English Channel

1981 ◽  
Vol 61 (3) ◽  
pp. 685-689 ◽  
Author(s):  
J. Binyon
Keyword(s):  
Body Weight ◽  
Osmotic Stress ◽  
Sea Water ◽  
English Channel ◽  
Sharp Threshold ◽  
Branchiostoma Lanceolatum

Previous work has indicated that, although in possession of numerous supposedly osmoregulatory structures, Branchiostoma lanceolatum from the English Channel is unable to regulate its body weight in diluted sea water. In vitro measurements of the rate of flagella activity in those organs similarly indicates no increase under hypo-osmotic stress. There is however quite a sharp threshold around 18‰, below which flagella activity ceases quite abruptly. A similar situation obtains with the gill cilia although the animal can remain alive at these salinities for a period of several weeks.

Ciliary Activity and Oxygen uptake in Branchiostoma Lanceolatum(Pallas)

1965 ◽  
Vol 43 (1) ◽  
pp. 1-12
Author(s):  
W. A. M. COURTNEY ◽  
R. C. NEWELL
Keyword(s):  
Oxygen Uptake ◽  
High Rate ◽  
Ciliary Activity ◽  
Oxygen Utilization ◽  
Nervous Control ◽  
Pharyngeal Wall ◽  
Temperature Range ◽  
Zero Rate ◽  
Branchiostoma Lanceolatum ◽  
Set Up

1. The rate of oxygen uptake by single specimens of Branchiostoma lanceolatum has been shown to vary considerably. Some animals in sealed vessels at 50° C. were able to utilize the oxygen linearly down to less than 20% of air saturation. Others ceased to absorb oxygen at high saturations while yet others displayed two different rates in a sequence starting initially with a high rate. 2. There are three possible rates of oxygen utilization, as well as a zero rate, for an animal at any temperature between 10 and 19° C. Animals in gravel exhibit only two rates at lower temperatures. 3. The slowest rate varies exponentially with temperature but the two faster rates show a rapid increase between 10 and 15° C. with little change outside this temperature range. 4. The effect of size and temperature on the increased oxygen uptake during the faster rates of respiration are discussed. It is suggested that ciliary activity of the pharynx could be associated with the extra oxygen utilization. 5. It has been found that there are three inhalant stream velocities, a fast, a slow and a zero rate with no intermediate rates. 6. Study of the isolated portions of the pharyngeal wall confirm that the fast inhalant current is set by the activity of all the cilia to give a feeding stream. The slow stream is set up by the lateral cilia, which continue to beat when the frontal cilia and most of the lateral cilia have been inhibited by lowered oxygen concentrations. 7. The lateral cilia have been shown to be under nervous control and to be inhibited by pressure on the pharyngeal bars. This mechanism depends on the presence of a connexion between the pharyngeal bars and the endostyle.

scholarly journals XV. On the chorda dorsalis

1841 ◽  
Vol 131 ◽  
pp. 195-199
Keyword(s):  
Whole Body ◽  
Chorda Dorsalis ◽  
Embryonic Structure

For the discovery of the remarkable structure in the embryo of some of the Vertebrata denominated the chorda dorsalis, we are indebted to Professor Baer. This naturalist considered it “the axis around which the first parts of the fœtus form,” and “the true virga mensoria for the whole body and all the chief systems.” Reichert supposes it to be that embryonic structure which serves as a “support and stay” for parts developed in two halves. In the course of my researches on the mammiferous ovum, an object was noticed which seems to correspond in appearance to the incipient chorda now referred to. I am desirous of drawing attention to this similarity in appearance, but more particularly to point out some important differences between my own observations and those of others, as to the mode of origin of the objects in question, and their relation to surrounding parts. For, should it be found that these objects are the same, my belief is that even the most recent views on the incipient growth of the embryo must undergo a change.

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