N-USOC / Research / WOSP

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WOSP
- Short and Long-Term Effects of Microgravity on the Development of Rotifers and Nematodes

Acronym:	WOSP
Full name:	Short and Long-Term Effects of Microgravity on the Development of Rotifers and Nematodes
Principal Investigator:	Dr. Claudia Ricci, Universita'degli Studi di Milano, Italia
Hardware developer:	EADS Space Transportation, Friedrichshafen, Germany, and Laben S.p.A., Italy
Increment(s) assigned:	TBD
Manifested:	TBD
Point of Contact:	PI: Dr. Claudia Ricci, claudia.ricci(at)unimit.it N-USOC: Ann-Iren Kittang, ann-iren.kittang(at)bio.ntnu.no

Research summary Two aquatic microscopic metazoan species - the rotifer Macrotrachela quadricornifera and the nematode Panarolaimus rigidus, will be cultivated inside the EMCS onboard the ISS. The aim of the experiment is to determine the effect of microgravity on the arrangement of the cytoskeleton and investigating the animals developmental process (both species are early determined) and their morphology (both are eutelic). The species are launched in anhydrobiotic conditions. In space, re-hydration is started in the first chamber by adding the culture medium. Parallel experiments for each taxon (rotifers and nematodes) shall run at 21°C in both the static centrifuge and under 1xg as a reference on the movable centrifuge. The medium has to be replaced frequently. In order to preserve its nutritional characteristics, the medium, prepared by mixing water and food powder, can not be stored longer than 15 days. The density of animals and their health condition are checked by means of the camera provided by the EMCS facility (magnification 10x to 50x). From 6th to 8th day of cultivation of nematodes (longer time for rotifers), eggs or juveniles will be transferred to a new culture chamber where the second generation will develop and reproduce. Animals in the first culture chamber shall be collected on a filter and desiccated under controlled humidity conditions (3 days at 98% RH and then maintained at 30-40% RH for rotifers; 1 day at 98%, then to 40% in two days for nematodes). The desiccated animals will be stored at -20?C until return to ground. The above procedure will be repeated for several generations in order to have a multigenerational experiment. The goal is to have 5 generations including the one started from ground.

Experiment Unique Equipment (EUE) The development of five consecutive generations of Rotifer requires a system able to breed, divide and maintain separated generations within an increment period. Five generations can be cultivated by exploiting a back and forth method using two Culture Chambers only. (A minimum of two chambers are needed in order to separate eggs from animals.) The Rotifer experiment is executed as follows: During hydration, animals are moved to the 1st Culture Chamber. Then animal grow and lay eggs that will fasten to the walls. Laid eggs are suspended by using a stirrer and moved to the 2nd Culture Chamber; the animals will be suspended with the stirrer and moved to the desiccation chamber connected to the 1st Culture Chamber. Eggs hatch and develop in the 2nd Culture Chamber, the resulting population lays eggs that will be separated from the animals and transferred to the 1st Culture Chamber, while the animals will be moved to another desiccation chamber connected to the 2nd Culture Chamber for drying. The experiment continues until the 5th generation by moving eggs from one Culture Chamber to the other at given time intervals. The rotifer desiccation procedure consists of 3 days at 98% RH and then 30-40% RH. The chamber with the dry animals will be removed, stored at -20?C, and replaced by a new one after a desiccation cycle.
The culture chamber is the environment where animals grow and breed. There are three cultivation chambers per EC, and each cultivation chamber is connected to one de-hydration chamber each. Rotifers are interstitial animals and subsequently they can try to hide themselves in the fibers of substrate, laying eggs inside it. The de-hydration chamber permits the detachment of animals from the substrate during the hydration process performed at the beginning of the experiment.
In the culture chamber the animals grow and lay eggs. In each EC are present two arrays in which two cultivation chambers are accommodated. Each CC is connected to a desiccation chamber. Rotifers are interstitial animals and, when water is removed, adhere to the filter that will be present in the desiccation chamber. A dry filter, prepared in the lab before the flight, will be used to initiate the experiment, as the dry rotifers can be removed from the filter by flowing water.

Rotifer EUE 3D-model
Nematodes: There are some basic differences between Rotifers and Nematodes, and because of these differences the EUE for the two parts of the WOSP experiment are different from each other. The concept baseline is the same as for Rotifer. Major differences concern the presenceof a support (semirigid grid), of a substrate for dehydration (filter) and the absence of a stirrer in the Culture Chambers. The support is necessary for the nematodes to move in absence of gravity and to feed. The stirrer is not required because the nematodes do not adhere to the substrate but rather tend to crawl by coiling. As eggs have the same diameter as adults, the juveniles will be transferred to the next Culture Chamber. The transfer will be accomplished by medium flow. Other relevant differences concern the absence of a desiccation Chamber and the replacement of one chamber at each generation. The nematodes, after the transfer of the juveniles to the next Chamber, will be dried in the same Cultivation Chamber, where a filter is present. This Chamber will be removed and replaced by a new one, where the juveniles of the next generation will be transferred. The figure below shows the Nematode Culture Chamber.

Rigid support inside Culture Chamber
The Nematode experiment will use a back and forth concept design, but the Chambers will be replaced at each generation, and the removed Chamber will be stored for returning to ground. Download WOSP experiment flyer