Termite nest architecture:
extended superorganisms?
Paul Eggleton
Synopsis
Synopsis
• Review of mound structures and their functions
• Concentrate on Macrotermes
• What makes up a termite colony?
• How does the colony function?
• What sort of entity is it?
Termite architecture
• Most complex, non-anthropogenic, constructions
• Complex functions
• Integrated part of a colony
A few examples of colony structures
Definitions
• Almost all building material are constructed from faeces.
• The nest is where the colony lives, and is often made
from woody faeces, but may not be easy to delineate
• The mound covers the nest and has a protective
function. It is always made from soil – usally from faecal
soil but sometimes from subsoil transported by workers.
Functions of nests and mounds
Protection from rainfall
Protection
• Nests seem to be defended in four ways:
– Walls
– Strong point defence
– Counter-attack defence
– Labyrinth defence
Defending the interior: tunnels
Block tunnel and crush or concuss = “Strong Point”
Cryptotermes
Phragmotic crushing
Pericapritermes
Energy storing concussion
Defending the exterior: the nest
Recruit to the surface and
then kill, often using
chemical defences. “Counter
attack”
Acanthotermes
Nasutitermes
Slice
Squirt
Daubing brush
Rhinotermes
Defending nests: the labyrinth
Coptotermes
Queen and soldiers
Energy required to find the
Queen may be greater than
any energy acquisition.
Homeostasis
• Ventilation
• Gas exchange
• Moisture control
Macrotermes
• The most extreme example and the one that shows all
the elements of the ‘colony as organism’
• One of the most organisationally complex biological
system in the world
Evolution of fungus-growers – complexity and
serial mutualism
1
‘Blattid’
Gut flagellates
Termitomyces
Gut flagellates
Cryptocercus
2
Wood-feeding
termite
3
Fungus-growing
termite
1.
Wood-feeding, gut flagellates (in ancestor of Cryptocercus and
termites)
2.
Eusociality (sterile castes, permanent colonies)
3.
Externalisation of gut, gain of fungus, loss of flagellates,
Lamellar flow
Thermosiphon
Eastgate Centre, Harare, Zimbabwe
Better analogue: human lung
Tidal system, NOT circulatory
Not a ventilation system, as
thermal sink in soil acts as heat
buffer.
Thermal sink
What makes up a colony?
• Reproductives:
– Royal pair
– Alates
• Soldiers (2 morphs)
• Workers (2 morphs)
• Fungus
• Mound & nest
• 8-10 organ systems?
At what level can we recognise an ‘organism’?
• Organisms:
– Persist (protection, defence, feeding, movement etc…)
– Reproduce
• The ‘organismal’ level of organisation is therefore the lowest
hierarchical level which fulfils those requirements
• What is that level in, say, Homo, and Macrotermes?
• What is the lowest level of organisation that acts like an organism?
Organisational levels: Homo
• Entity
Persist Reproduce
• Mitochondria
X
X
• Nucleus
X
X
• Cell
X
X
• Ovary
X
()
• Heart
X
X
• Human body


• Therefore, trivially, ‘human body’ is the level of
organisation that acts like an organism
Organisational levels: Macrotermes
• Entity
Persist Reproduce
• Mound / nest

X
• Soldier
X
X
• Worker
X
X
• Reproductive
(X)

• Fungus
X
()
• Colony


• Therefore colony is the level of organisation that
acts like an organism
MOLECULES
Proto-Eukaryote
Eukaryote cell
α-Proteobacterium
‘Pre-cell’
‘Cell’
‘brain’
‘Organ’
‘mouse’
‘Body’
‘colony’
‘Colony’
POPULATIONS
Organisational levels of complexity
• Atoms
• Molecules
• Prokaryote cell
• Eukaryote cell
• Organ (somatic/ gametic)
• Body
• Colony
• Populations
• Metapopulations
• Communities
Biotic (?’Organismal’) level
‘Superorganism’ definition
•
Examined in this way we seem to have two definitions of
superorganism:
1.
An organism made up of many other entities, which are
themselves organisms
2.
An organism made up of many other entities, which are now,
or have been in the past, organisms
•
(1) limits us to, say, dictyostelid slime moulds
•
(2) includes almost everything
•
There seems to be no logical justification for the concept
‘superorganism’ as presently employed
A superorganism?
So – analogy among multicellular organisms?
•
Six multicellular origins:
1. Metazoa (animals)
2. Plantae (green plants)
3. Volvocaceae (green algae clade)
4. Phaeophyta (brown algae)
5. Rhodophyta (red algae)
6. Fungi
Which is a fair analogy?
This seems to me to present a fairer analogy than Metazoa
Somatic cells
(workers)
Extra Cellular Matrix
(nest)
Gonidia
(alates)
Value of somatic cells?
“ [we] concluded that by pumping nutrients into the Extra
Cellular Matrix to feed the gonidia, Volvox carteri somatic cells
elevate the reproductive performance of the organism more
than enough to provide a powerful selective advantage, despite
the fact that they themselves have no reproductive potential
whatsoever.”
Kirk (2003, Inter. Comp. Biol.)
- This sounds familiar!
Multiple origins of germ
and somatic lines
Origin of clade ~ 75 MYA
So…
• Difference between different permanent aggregations
are differences in organisational complexity, not
differences in kind
• Difficult to make comparisons between hierarchical
levels except as rough analogies
• Candidate superorganisms (or ‘metaorganisms’) do not
qualify as their constituents parts are not organisms
• Almost all are, considered globally, colonial organisms,
or more simply organisms