Supporting information

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.