Original videos of our investigation.
A Heart of Seven Valves.
On the structure and mechanics in vivo of the ostial cells and the aortic valve of the Drosophila melanogaster larva heart by analyzing high resolution microscopic images
Authors: Claudia Rodríguez Rodríguez y Juan Sánchez Mateos.
Coordinator: Jesús Manjón Sánchez
High School: IES Maestro Gonzalo Korreas. 10400 Jaraíz (Cáceres, Spain)
Three courses ago, being in the first cycle of ESO, we investigated the cardiac beat in vivo of the zebrafish embryos (Danio rerio) and larvae and pupae of the fruit fly (Drosophila melanogaster) which we grew up in our centre on our own. Two principles guided our first scientific work: the observation of the vital activity of the early stages of the development of these organisms by non-invasive techniques and the use of modern techniques of digital processing of scientific images. That allowed us to get a fine quantitative analysis and to come conclusions based on the high spatial and temporal resolution of HD video images captured by compact cameras through the microscope eyepiece.
Drosophila melanogaster is one of the most useful invertebrate models in the research of both normal and pathologic physiology of the human heart. The larvae have a dorsal tubular vessel which has got a total of three pairs of ostiolar valves (incurrent) and one intracardiac aortic valve (excurrent). However, little is known about its pumping mechanics, and the activity of its ostia cells and much it is assumed. Furthermore, the biomechanics of both the ostia cells and the aortic valve have not been widely discussed in the scientific literature, showing a certain degree of ignorance of both their function and their structure in vivo. Even it is said that that cardiac contraction is peristaltic. In our research we show several findings obtained through the Full HD recordings of the activity of the larval heart and its cells.
The objectives of our research have been: firstly, to get Full HD video recordings of the in vivo activity of the wild type Drosophila melanogaster larval heart and secondly, to test three strong related hypothesis about cardiac mechanics of the fruit fly in its larval stages. The first hypothesis holds that the three pairs of ostiolar valves are formed by pairs of cells that open/close passively each one of the ostioles like bipartite clack valves. The second one is that despite its length the proper heart contracts and expands as a whole as it happens in the embryo. And the third one is that there exists a unique intracardiac valve in the larvae, the aortic valve, which is made up by two big occlusive cells that act passively and mark the beginning of the aorta.
In order to test all this, we recorded, in Full HD video, the cardiac activity of Drosophila melanogaster larvae without harming them. After processing the scientific images digitally, that we previously had obtained, we performed a fine both spatially and temporally analysis of both their structure and mechanics in order to test the three above mentioned hypothesis.
In conclusion, we strongly believe that we provide enough evidence to doubt about the passive nature attributed to the ostiolar cells in the mentioned hypothesis. At the same time, we have got unique images of the ostiolar cells of the Drosophila larva in action. And, finally, we can say now that the Drosophila larva heart contracts and expands as a whole, as in the embryo. There is not a peristaltic wave that progresses from the posterior end to the anterior region of the heart as it was said and believed.