The purpose of the experiment was to examine spider prey capture, web building, and silk characteristics in a microgravity environment. The project was also intended to foster interest in space exploration and scientific research for the Australian students. In addition to looking at gravitational biology in spiders, the examination of a spider's solution for producing a web with minimal gravity could have practical applications. On Earth, spiders can use gravity (their body weight) and/or manipulation of their spinnerettes to extrude several different types of silk. Even when the chemical composition of the silk is unchanged, the rate and mechanism used to pull the silk determines its mechanical properties. Similarly, altering methods of producing manmade fibers can result in materials that are more elastic, stronger, etc. Understanding the way a spider builds its web in space may help engineers build web-like structures for space stations and other aerospace architecture.
The golden orb weaver (Eriophora biapicata), a large non-toxic spider that produces a highly regular orb web, was selected as the species for the experiment. The students learned that spiders that were too young could not produce regular orbs, while spiders that were too old were both too large for SpaceHab's habitat and in danger of dying from old age by the time a shuttle launch occurred (the natural lifespan of the spiders is one year). Two-month-old spiders were selected for the study. Also, the students discovered that the spiders needed to be hungry (6 days between meals) to be stimulated to destroy an old web and build a new one.
Ultimately, young spiders were raised at the Royal Melbourne Zoo (below: Patrick Honan, Invertebrate Keeper at the zoo, and a spider). Thirty of them were transported to Florida for the mission, and eight of the most lively spiders were selected to become 'spidernauts' for the 16-day shuttle mission.
The habitat (175mm x 110mm) included fruit fly larvae, at various levels of maturity, to provide an ongoing food supply for the spiders. The spiders were intended to be kept separated, in order to prevent them from killing and eating each other (photographic data indicates two spiders were present in the habitat at one point). Data taken on the ground and during flight were available for anyone with an Internet connection to access at the STARS website. Temperature, humidity, and light were recorded. Every hour, a low resolution photo of the spider box was taken. There were also some movies of the habitat, to show the motions of the spiders.
Although the silk from the webs cannot be examined, the photographic and video data could be used to draw tentative conclusions about the activities of the spiders during the mission. If the spider in the habitat did eat its old web (which it normally would, although spiders have been known not to ingest intact webs or behave normally under stress), then a video showing a spider moving in a roughly circular pattern would indicate it was building an orb web during orbit. Personally, I was unable to see the orb itself. I did see irregular silk near the light source (fruit flies are attracted to light), but was unable to determine whether the web was the same as that built on the ground or a new web. The spider was seen in the center of its habitat, as would occur in an orb, and it did move off to the side of the enclosure during 'daylight' hours. Keep an eye of the Glen Waverley Secondary College site, to see future developments and to see the researchers' analysis of the data.