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Adeptus Mechanicus Data Files
Crossfile: Magos Biologis Data Files

Respiration Of Tyranids in Low Pressure and Oxygen Deficient Atmospheres

From a request by: Brigadier General Berdan, 15th Lavarikian Rifles

General Berdan,

Greetings once more General, I am pleased that our information helpful to you in this situation. Your subsequent Question about the respiration of tyranidic organisims requires a significant response. For in this the tyranids surpass any known creature in terms of scope and adaptablity. What follows in an excerpt from a classified file.

The need for all living things to respire is universal whether performed directly by the organisim or it's host repiration is required to maintain biological functions. However the modes of respiration employed are nearly endless. The tyranids, on the whole, exhibit a startling and disturbing variety of metabolic mechanisms to ensure respiration is affective and possible in nearly all known atmospheres. This indicates that throughout the eons of evolution the tyranids have absorbed and encountered creatures, which require vastly differing biological means by which to sustain life. Certain cells within the tyranid organism are critical to many biological adaptations. These Phage cells were originally thought to be an anti-toxin component, this was due to the affects they have on many compounds that are recognized toxins in other creatures. Subsequent and ongoing investigation into this shows that these cells have startling characteristics.

"Phage" cells, a misnomer attributed to our early studies, are the metabolic panacea of the tyranids. Intensive study has shown these cells are capable of surviving extremes of pressure [<0.01 to 10 ATM], extremes of temperature [-80 C to 165 C] sustained, and significant radiation dosing. At any one time only 12-18% of the cells receptors and chromosomes appear to be active. Conditions however change which portions of the cell functions allowing the cell itself (separate from cerebral control) to adapt to perform it's myriad of roles in vastly differing conditions.

Phage cells as catalysts of respiration

<Ref:D/BacillusInfernus/TerranDataArchive>
Tyranids are able to use a huge number of compounds as agents of respiration. Oxygen is often thought of to be an essential respirant for life, this represents a lack of knowledge on the part of those making these assumptions. (Or a mammalian centric view) Prior to photosynthesis within biospheres oxygen isn't plentiful enough to be used as a respirant. Anaerobic biologies are common in nearly all biomes though they are typically limited to microbe level development. The respiratory Agents employed by the tyranids allow them to alter metabolic function, moving from one respirant to another when adequate amounts are changed.

<SeeREF:MBf:/Tyranid/Biology/Physiology/respiration/mechanisms>
Iron Oxide, Sulfate, Nitrate, Carbon Dioxide, Manganese, Chromium, Cobalt and Oxygen all have been observed to be used by tyranid organisms as respiratory agents. While these agents are not unique to the tyranids the use of multiples in sequence and in such a large organism is unprecedented.

MB Lambshead has found evidence that the respiration of tyranids also includes  chemoautotrophic and photosynthetic qualities, meshed into the redundent biomechanisms. 

Unique metabolic Strategies which afford tyranids significant advantages in dealing with metabolic byproducts such as fatigue toxins: Excerpt: Tyranid Hard vacuum metabolic study.

Subject: Termagauntus Hormaguantii [hormagaunt]
Auspex reading diagnosis: While active the initial respirant levels of oxygen steadily dropped, while CO levels rose.  The creature maintained 99.7% of dissolved gasses even in hard vacuum.  Once free oxygen levels dropped below 30% effectiveness a remarkable metabolic change occurred. The creature immediately and with no signs of distress began metabolizing CO as the agent of respiration.  Operation only on the dissolved gases available at the time of decompression was 2 hours. At which point other trace elements were scavenged from the carapace and skeleton to facilitate receptor changes.  Based on the metabolic output of energy required and the lack of any source of replacement nutrients the creature could theoretically operate (minimally) for upwards of 2 weeks before chemical equilibrium's could not be manipulated sufficiently to provide adequate energy. [In open space?! astonishing Keplar]  At this point rather than expiring the creature will enter torpor of minimal metabolic activity and can remain so for an undetermined period of time.  Current Time stands at 407 days and counting.

Given other types of atmospheres (methane based/ammoina based) to breath the creature will adapt in similar ways switching acidity and receptors within the redundant biology to make use of the primary respirant and the byproduct alternately until the its energy reserves fail due to lack of caloric input.

Genestealer infestations upon drifting hulks must be making use of this mechanism to survive the hundreds of years between waking moments.

[This biological mechanism is similar to energy cells that cycle to prolong useful life Keplar]

I trust this information will be of some value in your efforts if nothing else to avoid wasted effort in futile tactics.

Master Apothicariate Curairus
Magos Biologis Salk
Draco Legion Biomedical Research station: New Hallefuss