قياس الاستجابة التغذية الناجم عن الجلوتاثيون في حيدرة
Summary
Here we describe a simple assay for the quantification of the feeding response in hydra induced by the reduced form of glutathione. This assay relies on measuring the distance between the apical end of the tentacle and mouth of hydra.
Abstract
Hydra is among the most primitive organisms possessing a nervous system and chemosensation for detecting reduced glutathione (GSH) for capturing the prey. The movement of prey organisms causes mechanosensory discharge of the stinging cells called nematocysts from hydra, which are inserted into the prey. The feeding response in hydra, which includes curling of the tentacles to bring the prey towards the mouth, opening of the mouth and consequent engulfing of the prey, is triggered by GSH present in the fluid released from the injured prey. To be able to identify the molecular mechanism of the feeding response in hydra which is unknown to date, it is necessary to establish an assay to measure the feeding response. Here, we describe a simple method for the quantitation of the feeding response in which the distance between the apical end of the tentacle and mouth of hydra is measured and the ratio of such distance before and after the addition of GSH is determined. The ratio, called the relative tentacle spread, was found to give a measure of the feeding response. This assay was validated using a starvation model in which starved hydra show an enhanced feeding response in comparison with daily fed hydra.
Introduction
Hydra is the most primitive organism possessing a nervous system and chemosensation for detecting reduced glutathione (GSH) for capturing the prey1. It feeds on a variety of animals such as nematode, crustacea, insect larvae, tadpoles and newly hatched fish1. The movement of these prey organisms causes mechanosensory discharge of the stinging capsules called nematocysts from hydra, which are inserted into the prey2. GSH present in the fluid released from the injured prey subsequently activates the feeding response in hydra which includes curling of the tentacles to bring the prey towards the mouth, opening of the mouth, and consequent engulfing of the prey. Multiple molecules, such as dopamine3, glutamate4, GABA, glycine5, NMDA receptors6, and allatotropin7, have been shown to be involved in the feeding response in hydra. It has also been shown that the chemosensory response induced by GSH is modulated by the feeding status of the animal such that starved hydra exhibited enhanced feeding response1. Such an increase in the GSH sensitivity is biologically relevant since under starvation hydra need to find its prey at higher sensitivity.
Although the feeding response induced by GSH can be clearly observed under microscope, the methods typically used for measuring the feeding response observations are non-quantitative. In most of the cases, the time during which the mouth of the hydra remains open was taken as a measure of the feeding response8,9; whereas in another case, quantitation was based on the number of hydra out of a population showing the feeding response10. However, observing the mouth opening time of the hydra polyps is cumbersome and subject to variation induced by uncontrollable parameters such as the direction of the mouth orientation during observations. Similarly, since the feeding response is a quantitative parameter, population-based approaches are subject to variations/errors caused by the opinion or observational bias of the individual observer. To circumvent these issues we have developed a method for the relative quantification of the feeding response in hydra (Hydra vulgaris Ind-Pune11) based on the distance of the apical end of the tentacle from the mouth of the hydra polyp.
Protocol
Representative Results
Discussion
سلوك التغذية في حيدرة يمثل واحدا من أكثر أنظمة حسي كيميائي الأجداد في metazoans. على الرغم من أن تم الكشف عن وجود الجلوتاثيون في السائل القشريات صدر بعد بمساعدة كيسة خيطية التقاط الفريسة منذ فترة طويلة 1، وقد تميزت أيا من البروتين GSHR ولا المفترض الجين الترميز / ث من ه…
Declarações
The authors have nothing to disclose.
Acknowledgements
Authors are thankful to K. P. Madhu, Nita Beliappa and staff of the Media Centre of Indian Institute of Science Education and Research, Pune for their help in the video production. The work was supported by funding under the Centre of Excellence program of Department of Biotechnology, Government of India to SG and postdoctoral fellowship by Department of Science and Technology, Government of India to RK.
Materials
| Cooled Incubator | Panasonic | MIR-254-PE | |
| Microscope | Leica | S8AP0 | |
| Camera for the microscope | Leica | EC3 | |
| Reduced glutathione | Sigma | G4251 | Stored at 4°C. Bring the bottle to room temperature before opening to avoid oxidation |
| Image editing program | GIMP | Version 2.8 |
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