LSDA - Experiment

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EXPERIMENT INFORMATION

Web Formation (ED52)

Principal Investigator

+ Miles, Judith S.

Bioastronautics Roadmap

+ Sensory-Motor Adaptation

Species Studied

Araneus diadematus (Spider)

Experiment Description

OBJECTIVES:
A spider is not an insect, although it is commonly mistaken to be an insect. Spiders, along with ticks, mites, harvestmen and scorpions, belong to the class arachnida. A spider has eight legs with no visible antennae and a two-piece body. A spider has silk-spinning organs, called spinnerets, at the back end of its abdomen, and usually eight eyes of various sizes and shapes. In addition, a spider's mouth parts are different from an insect's. Instead of mandibles capable of chewing, spiders have fang-tipped jaws called chelicerae used to inject digestive enzymes into it’s prey.

Araneus diadematus, the garden spider, is a very common resident of homes and gardens. It has a distinctive white "cross" mark on the abdomen which has given rise to the alternative aliases “cross spider” and “diadem spider.” It produces the traditional orb web, characterized by a pattern of concentric circles of silk threads that are small in the center of the web and get larger towards the outer area of the web. Since the spider senses its own weight when constructing the web to determine the required amount of silk to make the web, gravity plays an important role in the construction of the web. Therefore, the objectives of this experiment were to observe how microgravity affects the weight sensing mechanism for web construction in the common cross spider.

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APPROACH:
Three days before the launch of the Skylab 3 command module, two female cross spiders, Arabella and Anita, were each fed a single house fly and installed in a launch vial and provided with a water-saturated sponge. Spiders were maintained with food and water during the mission. The cross spider can live up to three weeks without food if an adequate water supply is available. Thus, the food requirements were very low during the mission. A special cage was designed to contain the spiders from the Skylab environment and provide a structure on which the spiders could build a web. The experiment was initiated by persuading the spiders from their holding vials into the observation cage. In addition, crewmembers took photographs and video of the spiders during the course of the mission.

RESULTS:
One day following the deployment of Arabella, a rudimentary web was constructed in the corners of the cage which was thought to be the web frame. A day later, a complete web was observed. These results prompted crewmembers to extend the original protocol by feeding the spiders rare filet mignon, providing an additional water supply, and deploying Anita at mid mission. On August 13, the Science Pilot removed half of Arabella’s existing web to initiate the construction of a new web. Arabella ingested the remaining half and refused to rebuild another web. Subsequently, water was provided where upon she proceeded to build a new web. The new web was better than the previous web indicating that Arabella had started to adapt to the microgravity environment. Arabella was returned to her launch vial and Anita was established in the cage. Anita’s reaction to the openness of the cage was recorded on video and described as being similar to Arabella's reaction, characterized as an erratic swimming motion. Both spiders died during the mission and both showed signs of dehydration which was thought to have caused their death. Examination of the returned web samples indicated that the thread spun in flight was significantly finer than that spun preflight, giving evidence that the spider utilized a weight sensing mechanism to size the thread.

Experiment Publications

MSFC Skylab Student Project Report. NASA TM X-64866, 1974.

Summerlin, LB editor. Skylab, Classroom in Space. Marshall Space Flight Center. NASA SP 401, 1977.

Skylab Student Project Summary Description. MSFC-SL-73-3, 1973.

Newkirk, RW, Ertel ID, Brooks CG. Skylab: A Chronology. NASA SP-4011, 1977.

Keyword:
Spiders

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