SHRIMP-2; Effects of cosmic radiation and space vacuum on the viability and development of the primitive crustacean Artemia franciscana (part 2)
A. Hernandorena (1), R. Marco (2), G. Reitz (3), R. Facius (3)
CERS Plateau de Latalaye
Universidad Autonoma de Madrid
Facultad de Medicina
Departamento de Bioquimica de la UAM e Instituto
C/Arzobispo Morcillo 4
Institut für Flugmedizin
In the experiment SHRIMP 2 the biological effects of HZE radiation and space vacuum on cysts of the brine shrimp Artemia franciscana were tested.
Several experiments, comparable in design, using Artemia
dormant gastrulae exposed to space radiation, have been performed in the past (Biosatellite II, Apollo 16, Apollo 17, Bion-3 (=Cosmos 782) and Bion-5 (=Cosmos 1129). The experiments were carried out by two independent research groups, one from Marburg (Germany), the other from Toulouse (France). Although the flight duration and the radiation levels in these experiments were comparable, deviating results were obtained by the two groups. While the Marburg group concluded that their studies on Artemia
yielded significant results, the Toulouse team only found very small and/or contradictory effects. Another objective of the SHRIMP 2 experiment was to test which of the reported results could be reproduced - those from Marburg or those from Toulouse.
Following the Biostack concept, Artemia cysts were sandwiched between plastic HZE detectors foils. Four stacks were prepared:
C. ground control-vacuum
D. ground control-pressurized
Stack B was kept in a hermetically-sealed compartment of the Biopan experiment tray during flight. Stacks C and D were kept in the reference experiment tray in a vacuum chamber at ESTEC at 19.5 °C throughout the mission.
After flight, the cysts were separated in different classes: a) directly hit, b) immediately adjacent to a particle track, c) at one square distance from a track, d) at two squares distance from a track, etc. The cysts were then grown under axenic conditions and the development of the groups a, b, c and d was compared. In addition, the life span of the animals was measured. Cysts hit by HZE under space vacuum were compared with cysts hit under 1 atmosphere.
More than 10,000 animals (nauplii and adults) were examined which emerged from the cysts after the flight.
A significant reduction in the hatching rate was found in the flight samples. Remarkably, the hatching rate of cysts that had been maintained at normal atmosphere during flight was significantly lower than cysts had been subjected to space vacuum. The reduced percentages of hatching were in the range of what should be expected from the probability that a cyst had been hit by a primary cosmic particle.
Most of the nauplii that developed from the cysts were normal and were capable of completing a normal post-embryonic development. In a small percentage of the adults anomalies were displayed. This percentage was higher in the pressurized than in the vacuum-exposed flight series. The anomalies were predominantly found in de abdominal portion. In a minor portion anomalies were spotted in the head, and even less in the thorax region. The localized nature of anomalies could be interpreted by assuming that in the cyst, a specific group of cells, determined to develop into a specific part of the body, had been damaged by a cosmic particle.
The reduction in hatching rate and the higher percentage of anomalies in the pressurized flight samples (as compared to the vacuum-exposed flight samples) may have been caused by a higher metabolic activity and oxygen content, leading to a higher radiosensitivity.
The SHRIMP experiments on Biopan-1 and -2 were not the first ones whereby cysts of Artemia were exposed to space vacuum. That claim should go to the CNES experiments on Bion-6 and -8 (Y. Gaubin et al. 1990). An innovative aspect of SHRIMP however was that two identical experiment packages, one hermetically contained, the other open to space vacuum, were flown side-by-side on the same carrier under exactly the same environmental conditions except for pressure, enabling the investigators to draw a straight conclusion about the contribution of space vacuum to the final outcome of the experiment.
A. Hernandorena, K. Scherer, A. Villa, C. Diaz, J. Mateos, G. Reitz, R. Marco, (1999), "A crustacean, another useful anthropod model system for space biology: Artemia dormant gastrulae, a system for studying the effects of the direct exposure of complex organisms to the space environment", Proceedings of the 2nd European Symposium on Utilisation of the International Space Station, ESA SP-433, pp. 521-525.
click on items to display
Reference 1: A. Hernandorena et al., (1999), ESA-SP-433, pp 521-525.