scholarly journals ABSORPTION OF THE HYDRANTH IN HYDROID POLYPS

1903 ◽  
Vol 5 (6) ◽  
pp. 297-303 ◽  
Author(s):  
H. F. THACHER
Keyword(s):  
Hydroid Polyps

Retinoids and pattern formation in a hydroid

Development ◽  
1984 ◽  
Vol 81 (1) ◽  
pp. 253-271
Author(s):  
W. A. Müller
Keyword(s):  
Retinoic Acid ◽  
Prolonged Treatment ◽  
Low Doses ◽  
Response Curves ◽  
Head Formation ◽  
Pulse Type ◽  
Head Activator ◽  
High Doses ◽  
Pattern Specification ◽  
Hydroid Polyps

The retinoids (retinol, retinal, retinoic acid) cause alterations in the pattern of limb elements in vertebrates (Summerbell & Harvey, 1983). As shown here, retinoids also influence pattern specification in hydroid polyps (Hydractinia echinata) in a way suggesting interference with the generation and transmission of signals responsible for the dimension and spacing of structures. A pulse-type application of low doses (e.g. retinoic acid 10-6 to 10-10 M, 4 h) causes metamorphosing primary polyps to develop more tentacles but fewer stolons per unit circumference, to shorten the length of the hydranth while the stolon elongates, and to bud secondary hydranths at high frequency 2–3 days after treatment (Fig. 3). Dose-response curves display optimum peaks. It is argued that the increase in budding rate is due to a reduction of the range of spacing signals emitted by the primary hydranth. In regenerating hydranths, low doses (10−10 to 10−9M) improve the rate of head formation, whilst medium doses (10−8 to 10−6M) result in more tentacles being regenerated. However, prolonged treatment with high doses (10−6 to 10−5 M) causes the animals to reduce all head structures and to transform eventually into stolons, in contravention of the rule of distal transformation that they normally obey (Fig. 8). The effects of the retinoids are counteracted by a putative morphogen, the endogenous inhibitor isolated from Hydra by Berking (1977). The Hydra-derived ‘head-activator’ displayed no stimulating effect on the number of tentacles and buds formed.

Cytophysiology of growth pulsations in hydroid polyps

1989 ◽  
Vol 249 (3) ◽  
pp. 258-270 ◽  
Author(s):  
L. V. Beloussov ◽  
J. A. Labas ◽  
N. I. Kazakova ◽  
A. G. Zaraisky
Keyword(s):  
Growth Pulsations ◽  
Hydroid Polyps

On the Mechanics of Growth and Morphogenesis in Hydroid Polyps

1974 ◽  
Vol 14 (2) ◽  
pp. 719-734 ◽  
Author(s):  
L. V. BELOUSSOV ◽  
J. G. DORFMAN
Keyword(s):  
Hydroid Polyps

Colonial Responses of Hydroid Polyps

1961 ◽  
Vol 38 (3) ◽  
pp. 559-577
Author(s):  
ROBERT K. JOSEPHSON
Keyword(s):  
Electrical Stimulation ◽  
Stimulus Strength ◽  
Sharp Threshold ◽  
Local Systems ◽  
Hydractinia Echinata ◽  
Hydroid Polyps ◽  
Conduction Of Excitation

1. Conduction of excitation in response to local mechanical or electrical stimulation has been studied in various hydroid species. 2. There are systems in the coenosarc of the stems and stolons of all species which conduct excitation at rates of from 1 to 3.5 cm./sec. 3. Two physiological types of conducting systems have been found. (a) Through-conducting systems, showing: all-or-none response, sharp threshold, reproducibility. (b) Local systems, showing: spread of response dependent upon stimulus strength, no sharp threshold, responses which decline with increasing distance from the stimulated point, variability. 4. Colonial co-ordination is better developed in those species whose colonies are structurally better developed. It is effected in most species by either (a) or (b). Both types are present together in Hydractinia echinata.

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