Bats, bats, bats and Bioenergetics

The Bat that flits at close of Eve
Has left the Brain that won’t Believe.”
–William Blake

 

haeckel_chiroptera

Ernst Haeckel: bats

Flying Freaks

Bats are the second most species rich and abundant mammals (rodents are the first). Bats are dispersed across every continent except Antarctica and make up 20% of all mammals, with over 12,000 species of bat worldwide.  Their order is labelled Chiroptera  (Hand-wing), and consists of two suborders Megachiroptera (mega bats) also known as Yinpterochiroptera and Microchiroptera (Microbats) or Yangochiroptera.
They are the only mammal capable of true flight. Their physiology has been tailored to flight , possessing highly flexible wings that can be folded so as to virtually disappear when not in use (Cheney et al. 2015).

bat-wing

Bat wing (Cheney et al. 2015).

These wings have thin muscle fibres running through them allowing the bat to fine tune wing shape for different situations, the underside of these wings is covered in fine hairs allowing the bat to sense air flow and respond appropriately. Different wing shapes occur in different species depending on their flight style, in general when compared to birds bats are better generalists, and demonstrate greater manoeuvrability than birds. Some species including Nectar feeding bats are capable of hovering flight though not quite with the extreme skill hummingbirds display.

Bats can even flip in flight “landing” to hang upside down, spend the day in torpor, and fall back into flight the next night.

Thundering Thoraxes

The demands of flight have lead to some developments in bat physiology,  most obvious (other than wings) is the extreme development of their cardiopulmonary system necessary to support the intense metabolic demands of flight, flying is no easy thing.

During flight heart rate can reach up to 1000 beats per minute. Bat hearts have amongst mammals the highest mitochondrial density, even the flight muscle (pectoralis) of bats has a greater mitochondrial density than the heart of other mammals, the muscle fibres are finer than other mammals and have an extensive capillary supply. Bats have the largest lungs and heart of all mammals relative to body mass. Amongst bats relative heart size decreases with increasing body size, lung size remains isometric (Canals et al.2005).

centurio-senex

Centurio senex wrinkle-faced bat

 

The fine structure of bat lungs has undergone  development when compared with other mammal lungs. The structure has complexified with an increase in capillary density and finer alveoli allowing for increased respiratory exchange (Figueroa et al. 2007).

The surfactant of the bat’s lung also appears to differ somewhat from other mammals though it fits a meaningful trajectory. With bats having a very low ratio of cholesterol to disaturated phospholipids (DSP).
Surfactant is a complex mixture of phospholipids, neutral lipid (especially cholesterol) and proteins.

The ability to lower and vary surface tension in response to varying surface area is attributed to interactions between the disaturated PLs (DSPs) and other lipids including cholesterol and unsaturated PLs.
Shifting volumes from inhalation to exhalation is essential to lung function this is affected by surfactant composition.

It seems likely that upon expiration compression of the Surfactant results in a squeezing out of unsaturated PLs and cholesterol. The disaturated PLs can be tightly compressed together as a result of the full saturation of their carbon chain and greater hydrophobicity. Unsaturated PLs cannot pack as tightly due to their unsaturation and resulting shape, and  they are less hydrophobic which interferes with tight packing.

For the Surfactant to spread over the alveolar surface on inspiration the surfactant must be in a liquid crystalline state. DPPC (dipalmitoylphosphophatidylcholine) the main disaturated PL found in surfactant has a phase transition temperature of 41°C . A pure DPPC film would require a higher body temperature to function but in combination with other components such as cholesterol surfactant can function at lower temperatures. In multiple animals the ratio of cholesterol to DSP rises during Torpor and Hibernation (when metabolism and body temperature decrease) showing how surfactant composition responds to changes in metabolism and body temperature.

Other organisms have lower body temperatures than mammals and tend to experience greater fluctuations in temperature. They also have simpler lung structures, amphibians have simple sac like lungs, reptiles slightly more developed lungs but both lack the alveolar structures and diaphragm of mammal lungs. Birds support high metabolic rates with a different solution they have a small pair of parabronchial lungs connected to a series of air sacs, which act like bellows moving air through the lungs in one direction. The lungs consist of a series of tubes (parabronchi) from which emanate the rigid air capillaries, alongside blood capillaries allowing gas exchange.

As a result organisms with less intense metabolism have a higher cholesterol to DSP ratio. The more complex structure of mammalian lungs require greater flexibility in the surfactant.  The increased surface area means more efficient reduction in volume must occur during exhalation and the surfactant must spread easily over alveolar surface on inhalation.

Among mammals bats with their incredibly intense metabolism have the lowest cholesterol to DSP ratio, in some cases up to 15 times less than other mammals (Daniels and Orgeig 2003).

Polyunsaturated fats (both omega 6 and 3) cause lung edema and alveolar thickening (Wolfe et al. 2002). Their unsaturation makes them more prone to spontaneous oxidation and breakdown into various toxic byproducts, in organisms with intense oxidative metabolisms their presence may be a real problem. Dietary PUFAs  (polyunsaturated fatty acids) are capable of altering lung surfactant composition lowering saturated phospholipids and increasing polyunsaturated phospholipids. Impaired surfactant function is involved in acute respiratory distress syndrome and severe pneumonia both of which show lowered levels of saturated phospholipids and increased unsaturated PLs (Schmidt et al. 2001).

Polyunsaturated fats interfere with respiration at every level from the lung to the cell. At least if you are warm blooded and wish to remain so it might be wise to avoid polyunsaturated oils.

Bats coordinate respiration with wing beat frequency, generally inhalation occurs on the downstroke,  exhalation on the up stroke (Suthers et al. 1972).  Yogis take note bats practice vinyasa, movement coordinated with the breath.

Fuel and Fire

Bats have  a great variety of dietary habits, including insectivores,  carnivores, frugivores, nectatavores, and of course the blood drinking sanguivore vampires. This would seem to indicate that a wide variety of diets can support intense metabolisms however amongst bats those who have the highest metabolism and the most energy demanding flight style are the nectatavores who like hummingbirds are capable of energetically demanding hovering flight though the bat may be capable of a slightly more energy efficient hovering style. The nectatavores don’t have the highest cephalisation of bats that appears to be found amongst some fruit eating species, carnivores, and the Vampires (maybe being a little monstrous benefits the brain).

If you compare the structure of fats and sugars you will see that fat is basically a chain of carbon and hydrogen however sugar comes premixed with oxygen. The chemical formula of glucose (and fructose) is C6H12O6. Each carbon from fat requires additional oxygen from the air to be oxidised to carbon dioxide and water. This could be thought of as being like the difference between a flame where combustion occurs when the fuel is not already mixed with oxygen from the air and when the fuel is already mixed with oxygen producing a shorter hotter more intense flame.

bunsen_burner_flame_types

various bunsen burner flames:

Left most flame relatively oxygen poor and Fuel rich, reducing flame. Right most flame oxygen rich, oxidising flame.

 

It seems the most pristine plasma may come from things that are sweet like a child’s blood.

Infernal Immortality

Could this creature cursed contribute to cancer’s cure,
Or teach us how to evermore endure?

The Rate of living theory is still believed by many despite an abundance of evidence that more Life results in more Life. The belief is that an increase in metabolism must inevitably mean increased production of ROS (reactive oxygen species), and a resulting increase in wear and tear on the organism. Bats have intense metabolisms and live remarkably long for animals of their size, generally larger species of animal live longer than smaller,  although smaller animals of a given species often live longer than their larger relatives for example small dogs live longer than big dogs. When corrected for body size bats are the longest living order of mammals.

The longest living bat on record is a 41 year old Brandt’s bat (Myotis brandti) from Siberia  (Podlutsky et al. 2005).

bat-life

correlation between body mass and lifespan

Correlation between body mass and maximum lifespan in mammals. Myotis bats are shown as blue diamonds, and other mammals as dark circles. The Brandt’s bat is indicated by a red diamond (Seim et al. 2013).

It was believed that hibernation might explain the longevity but even non-hibernating species show great longevity.
Mitochondria from bats show reduced rates of reactive oxygen species (ROS) generation with some species producing half the amount of non-flying mammals with lower metabolism (Bruet-Rossinni 2004).

Bats appear to be highly disease resistant, being infamous viral reservoirs, including Rabies and Ebola. Viral persistence in the absence of disease or pathology characterises the relationship between bats and viruses. And bats carry a lot of viruses, they positively pulse with pestilence.

This disease resistance is likely linked to their ability to fly or more precisely the metabolism that supports this. During flight bats metabolism increases enormously when compared to non-flying but otherwise active bats, this can be an up to 16 fold increase in metabolism, in rodents running to exhaustion metabolism increases 7 fold (O’Shea et al. 2014). Strains of mice bred for high metabolism show stronger immune responses, the intense metabolism required for flight will lead to increased circulation and increased activity of white blood cells, replicating some aspects of fever. The cyclical nature of the metabolic multiplication that occurs during flight and it’s decrease during daily dreaming may mean that pathogens are controlled and eliminated during activity while some survive during the bat’s torpor to persist to the next night. The lowered temperature of hibernation should inhibit replication of most mammalian pathogens.

The intense cardiovascular activity required to support this metabolism should be resulting in large amounts of circulating natriuretic peptides  (heart hormones) released when the heart is stretched. The natriuretic peptides increase phagocyte activity, phagocytosis (the process by which cells, usually immune cells, engulf and digest foreign material) decreases with aging (Boran et al. 2008). The natriuretic peptides also have significant anti-cancer activity (Vesely et al. 2007),  bats seem to be resistant to cancer, although it does sometimes occur, the metabolism that a bat must maintain to sustain flight likely makes the metabolic derangement characteristic of cancer highly unlikely to occur.

But the bat must fly fast, or plummet from the sky, and slowly sicken and die.
These observations that an intense metabolism supports a strong “immune system” seem to support an alternative way of thinking about immune function, where immunity to disease is a secondary result of processes whose primary function is in morphogenesis, the maintenance of the organism’s functioning and form, if the organism is engaged in such intense activity that all of its substance is actively metabolising then no space will be available for any parasites to take root.

Vampire Venom

This beast with Black banners was sliced and diced it’s glands were gouged and chemicals computed.
Now this beast has Red references so as not to be refuted.

Vampire bat saliva is a complex cocktail of chemicals composed of over 8000 different molecules (proteins and glycoproteins) many of theses are some form of anti-coagulant,  some are anti-microbial and some have other effects (Francischetti et al. 2013). Their purpose is to ensure blood flows from victim to vampire.

vamp-skull

Desmodus rotundus: common vampire bat skull

Some of the constituents include Desmoteplase (DSPA), Draculin, and desmolaris, I have seen some articles that treat Desmoteplase and Draculin as alternate names for the same chemical but they are separate molecules both have anti-coagulant effects (Low et al. 2013).

Desmoteplase is a protease plasminogen activator and causes fibrinolysis, breaking down blood clots. Desmoteplase appears a more effective anticoagulant than tpa (tissue Plasminogen Activator) and is thought to be promising in preventing and treating ischemic strokes.

Draculin is a glycoprotein and anticoagulant which inhibits some activated coagulation factors.

Desmolaris is an anticoagulant that binds kallikrein and reduces bradykinin inhibiting thrombus formation. It also has anti-inflammatory actions preventing increases in vascular permeability (Ma et al. 2013).
As a result of these properties various extracts of Vampire saliva have undergone trials for treatment of stroke.

However they might also have relevance in other conditions; including cancer where disordered clotting appears involved. Tissue factor (TF) is a glycoprotein that activates the clotting cascade, fibrinogen is cleaved into fibrin which polymerizes forming clots. Tissue factor is expressed by tumour cells it causes fibrin to deposit on circulating tumour cells trapping them in microvascular structures and promotes thrombosis, metastases and tumour growth (Kasthuri  et al. 2009).

Generally the intense metabolism of the bat promotes circulation and inhibits clotting through a variety of paths, carbon dioxide production from the intense metabolism may be one of the more elegant things to think about in this respect. Carbon dioxide acts as a vasodilator and promotes mast cell and platelet stability inhibiting the release of histamine and serotonin. Histamine and serotonin increase vascular permeability decreasing blood volume thickening the blood and promoting clotting.

Vampire saliva also contains CNP a natriuretic peptide (heart hormone) which increases heart rate and heart conductivity  (Springer et al. 2012), as well as increasing the strength of contraction (Beaulieu et al. 1997).

CNP is thought to be the ancestral natriuretic peptide with the other natriuretic peptides (including ANP and BNP) being generated from CNP in fishes far back in Creation’s Coil, although similar peptides occur in simpler organisms (Takei et al. 2011 and Inoue et al. 2003).

CNP also plays a morphogenic role specifically regulating bone growth (Mericq 2000).
Among higher vertebrates obligate blood feeding occurs in only three New World vampire bat species. These three vampires all diverged from a common insectivorous ancestor in a short evolutionary time, representing an enormous genetic development and required multiple coherent physiological changes including sensory, renal, secretory and of course dental (vampire bats have razor teeth).

To believe this occurred randomly is ridiculous.  Thankfully there appear to be scientists thinking about evolution in more coherent ways. Phillips and Baker (2015), suggest that vampire physiology developed by recruiting existing genes from other biological functions. One of these involves Entpd1, usually expressed in vascular endothelial cells and having anti-haemostatic properties. Two main processes appear to be involved exon  microdeletions, the removal of small sequences of a gene and alternative splicing, in which parts of a gene are put together differently, it occurs during gene expression and results in a single “gene” coding for multiple proteins as a result of different exons being included or excluded from the messenger RNA. It is thought that around 60% of human disease mutations involve splicing rather than mutations of the “coding” sequence (Bigas et al. 2005).

This suggests that evolution is an exploratory art that involves creativity and improvisation directed by the organism in responses to both changes in the environment and changes in the organism’s perception of itself and the environment.

Sinister Senses

The Bat blitzes through dark night,
Cares not for black or white,
So only does the Devil’s delight.

Bats have developed super senses that most other mammals lack, most famously the ability to see with their ears. By emitting a rapidly repeating ultrasonic series of squeals and squeaks and listening to the echos these creatures can fly in total darkness, even the wise Owl can’t do that let alone a silly Swan.

 

big-eared-townsend-fledermaus

Townsend’s big-eared bat, Corynorhinus townsendii

 

There is evidence that parallel genetic changes have occured in echolocating bats and dolphins again suggesting that something more meaningful than random chance is involved in genetic adaptation (Liu et al. 2010).

FoxP2 is a transcription factor implicated in development and neural control of oro facial coordination. Equivalents show almost no variation across vertebrates.  Humans and chimpanzees differ by two amino acids. In echolocating bats however FoxP2 appears to have undergone intense selection and demonstrates extreme diversity (Li et al. 2007).

Variations in FoxP2 in bats appear to be related to variations in bat species sonar. It’s seems possible that given its role in oro facial coordination  FoxP2  may play a role in the diversity these dwellers in darkness display in their faces. Interestingly FoxP2 is one of the genes that appears to diverge significantly from human in the Starchild skull.

FoxP2 seems to be involved in vocal learning in humans and seems to play a similar role in song birds, it might also be so in bats.Mutations in FoxP2 have been linked to developmental verbal dyspraxia (difficulty coordinating the muscle movements required for speech). FoxP2 is expressed in the brain and involved in neurogenesis and cortical development. FoxP2 is expressed in the heart and lung, in the lung it appears to be involved in alveolar development.

Bats also seem to be capable of magneto-reception (Wang et al.  2007), and make use of it to orient themselves, mole rats are also capable of magneto-reception, and like the bat they are unusually long-lived though different adaptations are likely involved in the mole-rat, high carbon dioxide levels seems like a possible connection, bats generate huge quantities as a result of their intense night life, Mole-rats likely maintain high carbon dioxide levels as a consequence of living in burrows. Bats that roost in caves may also be benefiting from increased carbon dioxide levels, depending on ventilation some cavernous ecosystems used by bats can contain 200 times the atmospheric concentration of carbon dioxide (Howarth and Stone 1990). I think based on  Ray Peat’s work that carbon dioxide might be a bio-electric doping agent increasing the conductivity of proteins and coherence of the organism, so playing a role in increasing subtle sensitivity.

Energy and Ecology

Obviously a creature like the bat with an intense metabolism requires a fecund environment to provide for it. Increasingly it is being realised that bat numbers and diversity are indicators of ecosystem health, bats also contribute to maintaining complex ecosystems they pollinate flowers, spread seeds from fruit, and control insect numbers ensuring vegetation is not overwhelmed. Their ability to fly, while energetically demanding  also allows them to participate in more intense flows of energy transformation.  Bats depend on complex ecosystems and in turn enrich them, and in many areas their numbers are declining.

Wicked Waves

In this Dread Dark what is this thing?
Weaving winds with webbed wing.
It’s thorax Thunders a Gigas Gongs,
This Lich’s lantern is ultrasonic songs.
Merrily murders moonstruck moths,
This Ghoul’s Ghost is gay as Goths.
Infernally inverted in cryptic caverns cursed it conspires,
Time twisting Heart harnesses Hell’s fires.
Now know this terror to be true,
Vampire Venom flows through You.

References

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Bigas NL, Audit B, Ouzounis C, Parra G, Guido R, (2005), Are splicing mutations the most frequent cause of hereditary disease, FEBS Letters, 579 (9), pp.1900-1903.

Borán MS, Baltrons MA, García A, (2008), The ANP‐cGMP‐protein kinase G pathway induces a phagocytic phenotype but decreases inflammatory gene expression in microglial cells, Glia, 56(4), pp. 394-411.

Brunet-Rossinni AK  (2004), Reduced free-radical production and extreme longevity in the little brown bat (Myotis lucifugus) versus two non-flying mammals, Mechanisms of ageing and development, 125(1), pp.11-20.

Canals M, Atala C, Grossi B, Iriarte-Díaz J, (2005), Relative size of hearts and lungs of small bats. Acta Chiropterologica. 7(1), pp.65-72.

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Francischetti IM, Assumpção TC, Ma D, Li Y, Vicente EC, Uieda W, Ribeiro JM, (2013), The “Vampirome”: transcriptome and proteome analysis of the principal and accessory submaxillary glands of the vampire bat Desmodus rotundus, a vector of human rabies, Journal of proteomics, 82, pp. 288-319.

Howarth FG, and Stone FD, (1990), Elevated carbon dioxide levels in Bayliss Cave, Australia: Implications for the evolution of obligate cave species, Pacific Science, 44(3), pp. 207-218.

Inoue K, Naruse K, Yamagami S, Mitani H,  Suzuki N,  Takei Y, (2003), Four functionally distinct C-type natriuretic peptides found in fish reveal evolutionary history of the natriuretic peptide system, Proceedings of the National Academy of Sciences, 100 (17), pp. 10079-10084.

Kasthuri RS, Taubman MB, and Mackman N,  (2009), Role of tissue factor in cancer, J Clin Oncol, 27 (29), pp. 4834-4838.

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Ma D, Mizurini DM, Assumpção TC, Li Y, Qi Y, Kotsyfakis M, Ribeiro JM, Monteiro RQ, Francischetti IM, (2013), Desmolaris, a novel factor XIa anticoagulant from the salivary gland of the vampire bat (Desmodus rotundus) inhibits inflammation and thrombosis in vivo, Blood, 122(25) pp.4094-4106.

Mericq V, Uyeda JA, Barnes KM, de Luca F, and Baron J,  (2000), Regulation of fetal rat bone growth by C-type natriuretic peptide and cGMP, Pediatric Research, 47(2), pp. 189-189.
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RK, Wood JL, (2014), Bat flight and zoonotic viruses, Emerg Infect Dis, 20(5), pp.741-745.

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