The first naked-eye-visible animals in exovivaria will almost certainly be insects. This may limit the appeal of early exovivaria -- insects hardly qualify as "charismatic megafauna", i.e., animals that naturally evoke wonder, admiration and respect.
On a more practical level, insects can be a problem in trying to balance artificial closed ecosystems, as the experience of Biosphere 2 showed: ants and cockroaches proliferated and overproduced CO2.1
If properly controlled, however, insect production of CO2 can be a good thing: plants might otherwise be starved of it, as their photosynthesis turns CO2 into oxygen. Insects wouldn't be a new solution to this problem: Victorian Era vivaria survived in part because of the (serendipitous2) discovery that plants in closed atmospheres transported over long distances needed the CO2 produced by the insects inside the containers.
Insects can also form multiple links in a food chain, with some insects eating others, and with any insect possibly becoming a meal itself or (through excretion while living and decomposition after death) a source of nutrients for plants and bacteria. Insects have even been proposed as a food source for human beings in space.3
Insects might do useful work and produce useful byproducts. Harvesting power from insect motion using piezoelectric devices has been demonstrated.4 (The piezoelectric devices might themselves be biologically derived.5,6) Producing silk on orbit might be possible: Abandoned cocoons, if matted and soaked, then frozen, could form a strong and renewable ice-composite shield against orbital debris strikes.7,8 "Cyborg insects" have been controlled by direct muscle stimulation and optical input.9,10
Bioplastics (possibly electroactive, yielding biomimetic muscles for telebots and power-generation components),11,12 dyes (e.g., carmine) and sealants might be derived from scale insects living parasitically on plants that have other uses in the exovivarial ecosystem.
A research question of particular interest: what are the minimum requirements for a permanent population of honeybees? Bees can pollinate, to help plants in the exovivarium reproduce. They also produce wax, which might have value as a sealant, as a lubricant, as a fuel,13 as a strengthener/preservative for strands of fiber derived from exovivarial plants, and as a base for casting. Honey might be used to feed other animals, and even be fermented to produce a burnable fuel (alcohol). Honey could be an export product for exovivaria, a prized item in the larders of (inter)national space stations, space hotels, and expeditionary spacecraft.
1 "Human terrarium, Biosphere 2, looking good at 20", Science on MSBNC, 4/26/2011 ⇑
2 David Hershey, "Doctor Ward's Accidental Terrarium". The American Biology Teacher Vol. 58, No. 5 (May, 1996), pp. 276-281. ⇑
3 "Insects as a Food Source in Space Agriculture", Naomi Katayama?, Yoji Ishikawa?, Muneo Takaoki?, Masamichi Yamashita?, Robert Kok?, Hidenori Wada?, Jun Mitsuhashi?, and Space Agriculture Task Force? ⇑
4 "Insect cyborgs may become first responders, search and monitor hazardous environs",Nov 22, 2011, Matt Nixon, University of Michigan News Service ⇑
5 BY Lee, et al., "Virus-based piezoelectric energy generation", Nature Nanotechnology 7, 351–356 (2012) doi:10.1038/nnano.2012.69 ⇑
6 Dan Krotz, "Berkeley Lab Scientists Generate Electricity From Viruses", Berkeley Lab News Center, May 13, 2012 ⇑
7 Powerful artificial muscles based on silk, and driven by humidity cycles, have also been proposed, see e.g., "Spider silk as a novel high performance biomimetic muscle driven by humidity, Ingi Agnarsson1, Ali Dhinojwala, Vasav Sahni and Todd A. Blackledge, The Journal of Experimental Biology, 2009. The temperature gradient between an ice-composite pressure vessel and a solar-thermal dish used for power generation and general industrial heat might provide an excellent basis for a supply of dry and wet air. ⇑
8 Silk might be further strengthened using silkworms engineered to produce spider silk, see e.g., "Silkworms transformed with chimeric silkworm/spider silk genes spin composite silk fibers with improved mechanical properties", Florence Teulé, et al., PNAS, Nov 28, 2011 doi:10.1073/pnas.1109420109 ⇑
9 "Cockroach Controlled Mobile Robot: Control and Communication in the Animal and the Machine", Garnet Hertz, 23 Dec 2008 ⇑
10 "Cyborg Insects Off The Drawing Board, Into The Air", Evan Ackerman, 8 April 2008 ⇑
11 Chitin is a source of polymers that have been considered for use in Mars rover electroactive bioplastics, see e.g., "Electroactive Bioplastics Flex Their Industrial Muscle", USDA Agricultural Research Service, 2005 ⇑
12 Electroactive polymers are under active investigation as components in Stirling engines, see e.g., "Electroactive Polymers for Free Piston Stirling Engine Power Generation", Benjamin Mattes (PI), Jan 9, 2012, NASA SBIR/SSTR 2011 Phase 1 Awards List, Proposal No. 11-1 S3.03-8593 ⇑
13 Beeswax candles might provide illumination and heat while an exovivarium is in earthshadow ⇑
Further reading
- Creating and Evaluating Artificial Domiciles for Bumble Bees (PDF). Douglas A. Golick, Marion D. Ellis, Brady Beecham. American Biology Teacher. 2006.
This page may have a more recent version on pmwiki.org: PmWiki:Insects, and a talk page: PmWiki:Insects-Talk.