Exoskeleton vs. Endoskeleton: biomechanical trade

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Exoskeleton vs. Endoskeleton: biomechanical trade-offs
Hercules beetle
(Dynastes hercules)
.
strength of skeleton
.
Ratio:
surface area (square)
volume (cube)
Shrew (Sorex sp.)
size of organism
a giant spider
Exoskeleton vs. Endoskeleton
The exception proves the rule, in aquatic arthropods.
…but this is not
possible)
1
Other advantages of the exoskeleton
The necessity of molting allows
complete metamorphosis
The cuticle includes
a lipid monolayer
The cuticle is impact resistant
What about six legs??
“Hexapoda” may not be monophyletic
Crustacea? Myriapoda?
Hexapoda (six legs)
Collembola
Protura
Diplura
Insecta
Dicondylia
Pterygota
Neoptera
Archaeognatha
Zygentoma
Ephemeroptera
Odonata
Plecoptera
Polyneoptera**
Paurometabola (orthopteroids)
Eumetabola
Endopterygota (Holometabola)
Paraneoptera (hemipteroids)**
(** ‘Exopterygota’)
2
Three classes of Entognathous hexapods:
Collembola, Protura, Diplura
Class Collembola (springtails):
Class Diplura:
oral cone
(collophore)
Class Protura:
12
Entognatha: Class Collembola (springtails, snow fleas)
6000 species
12-20 families
4 subclasses
(Lower Devonian)
Not a true insect:
• 6-segmented
abdomen
3
Entognatha: Class Protura (“proturans”)
730 species
3-8 families
2 subclasses
(Devonian)
Not an insect:
• no antennae
• anamorphosis
Entognatha: Class Diplura
(“diplurans”)
Not an insect:
• antennal flagellum w/
intrinsic muscles
• glandular cerci
800 species
5-9 families
2 subclasses
(Carboniferous)
4
The three major evolutionary innovations of the Class Insecta:
wings, wing-folding, & complete metamorphosis (≈ 27 orders, total)
Crustacea? Myriapoda?
Hexapoda
Collembola
Protura
Diplura
Insecta (Ectognatha)
Archaeognatha
Dicondylia
Zygentoma
1. Pterygota
Ephemeroptera
= aquatic immatures
Odonata
2. Neoptera
Plecoptera
Polyneoptera**
Paurometabola (orthopteroids)
complete metamorphosis
3. Endopterygota (Holometabola)
Eumetabola
Paraneoptera (hemipteroids)**
(** ‘Exopterygota’)
3 ocelli
order Archaeognatha (= Microcoryphia, Machiloidea)
compound eye
antenna
cercus
median caudal filament (MCF)
abdominal styli
labial
(seg. 2-9)
palp
(3-seg)
style on
maxillary palp
coxa
(7-segmented)
exsertile vescicle
ovipositor
incisor region
order Zygentoma
(Thysanura)
molar
region
maxillary palp
mandibles
(mono- vs dicondylic)
condyle
incisor region
molar region
condyle
condyle
style (8 & 9)
style
ovipositor
cercus
cercus
median
caudal
filament
‘subclass Apterygota’
median
caudal
filament
5
Apterygota:
Archaeognatha (bristletails)
350 species, 2 families; Devonian (?)
leg-like maxillary & labial palps
Monura?
median caudal filament
5 mm
Permian Dasyleptidae (Elmo fauna, Kansas)
Families: Meinertellidae & Machilidae
Apterygota: order Zygentoma (silverfish & firebrats)
370 species, 3-5 families
2 condyles
Thermobia sp.
Lepisma sp.
Tricholepidion gertschi
lives w/ w.NA. carpenter ants)
6
Apterygota are probably paraphyletic,
not monophyletic
(‘Apterygota’ (blue bar) is probably not a clade)
outgroup (monocondylic)
?
Monura (extinct; condyly uncertain)
Archaeognatha (=Microcoryphia)
dicondylic
mandible
Zygentoma (=Thysanura)
Pterygota (other insects)
Dicondylia
•
monophyletic: an ancestral species and all its descendants (a clade).
•
paraphyletic: a monophyletic group from which one or more
subsidiary clades (monophyletic groups) is excluded.
The origin of wings: Paleoptera
Crustacea? Myriapoda?
Hexapoda
Collembola
Protura
Diplura
Insecta
Dicondylia
Pterygota
= aquatic immatures
Neoptera
Archaeognatha
Zygentoma
Ephemeroptera
Odonata
Plecoptera
Polyneoptera**
Paurometabola (orthopteroids)
complete metamorphosis
Eumetabola
Endopterygota (Holometabola)
Paraneoptera (hemipteroids)**
(** ‘Exopterygota’)
7
The origin of wings: Paleoptera
Ancestral groups all have aquatic immatures:
Holometabola
Paleoptera
Ephemeroptera
Neoptera
Odonata
Plecoptera
Megaloptera
Pterygota, Paleoptera:
Ephemeroptera (mayflies)
> 3000 species, 25 families; suborders & superfamilies uncertain
adult
Adult
naiad
(nymph)
Naiad
(immature)
Ancestral features:
• 11-segmented abdomen
• cerci & median caudal
filament
• 3 ocelli
• post-adult molt
• paired genitalia (!)
(as in Archaeognatha & Zygentoma)
8
Mayflies – aquatic immatures
Nymph/naiad:
•
•
•
•
subaquatic
long-lived (vs. adult)
tracheal gills
morphologically
diverse
Permian mayflies: Protereisma sp. (Protereismatidae)
long antennae
Naiad (immature)
(after Kukalova)
5-segmented
tarsus
nearly full
wing venation
subequal
wings
Adult
(after Carpenter)
9 pairs
of gills
10th
MCF
9
Pterygota, Paleoptera:
Odonata (dragonflies & damselflies)
Two (or three) suborders, 27 families, 600 genera, 6500 extant species
‘s.o.’ Anisoptera
(dragonflies)
‘s.o.’ Zygoptera
(damselflies)
caudal
gills
Thoracic tilt
s.o. Anisoptera
(dragonflies)
s.o. Zygoptera
(damselflies)
10
Tracheal gills and nymphal “mask”
Anisoptera naiad (rectal gills)
“mask”
Zygoptera (caudal gills)
“mask”
Damselflies
11
Dragonflies
Libelluloidea
Aeshnoidea
Dragonfly progenitors: order Protodonata
(Carboniferous, approx 350 mya)
28 inches (70 cm)
Meganeuridae: Meganeura
Meganeuridae: Megatypus
12
Phylogenetic hypotheses for Paleoptera
I. Paleoptera are monophyletic (Hennig)
Outgroup
Neoptera (all other winged insects)
Odonata
Paleoptera
Ephemeroptera
II. Paleoptera are paraphyletic
(Kristensen)
(Boudreaux)
Outgroup
Outgroup
Ephemeroptera
Paleoptera
Odonata
Odonata
Neoptera (all other winged insects)
Neoptera (all others)
Paleoptera
Ephemeroptera
The Origin of Wing-Folding: Neoptera
Crustacea? Myriapoda?
Hexapoda
Collembola
Protura
Diplura
Insecta
Dicondylia
Pterygota
= aquatic immatures
Neoptera
Archaeognatha
Zygentoma
Ephemeroptera
Odonata
Plecoptera
Polyneoptera**
Paurometabola (orthopteroids)
complete metamorphosis
Eumetabola
Endopterygota (Holometabola)
Paraneoptera (hemipteroids)**
(** ‘Exopterygota’)
13
The morphological basis of wing-folding (neoptery): Axillary sclerites
PALEOPTERA
wing-folding)
Paleoptera
(no(no
wing-folding)
C+
ScR+
RsMA+
MPCuA+
CuP-
NEOPTERA
(wing folding)
Neoptera
(wing-folding)
2A+ 1A+
3A+
Odonata
C+
ScR+
RsMA+
MPCuA+
posterior notal process
1A+
2A+
3A+
Plecoptera
Pterygota, Neoptera, Polyneoptera: order Plecoptera (stoneflies)
3500 species, 2 ‘suborders’, 16 families
adult:
adult:
naiad:
naiad
(nymph)
(immature)
14
Pterygota, Neoptera, Polyneoptera:
Order Grylloblattodea (ice or rock crawlers)
> 33 species, 5 genera, 1 family (Grylloblattidae)
Discovered in 1913
(Walker 1914) as a
“living fossil”)
ovipositor
cercus
Pterygota, Neoptera, Polyneoptera:
Order Mantophasmatodea (gladiators, heelwalkers)
~24 living species, 3 families, ≥ 8 genera
(first recognized
in 2002!)
15
Pterygota, Neoptera, Polyneoptera:
order Dictyoptera, s.o. Blattodea (cockroaches)
4500 species, 6–9 families
Blattella germanica
Cockroaches, past & present:
Periplaneta sp.
Sc
R
C
“Blattoptera:”
Archimylacridae
(Carboniferous)
M
Sc
C
Sc CuP
R
CuA
R1
Rs
M
CuA
CuP
anal fan
M
1A
CuA
CuP
300 my-old fossil, 4” long
Carboniferous (central Asia)
16
Pterygota, Neoptera, Polyneoptera: order Dictyoptera, s.o. Isoptera (termites)
3100 species, 7 families (all eusocial)
“isopterous” wings
workers
nests (colonies)
Mastotermes darwiniensis (Mastotermitidae)
Termites:
“Social cockroaches”
imago
eggs in ootheca
anal lobe
Indotermes soldier
(Termitidae)
Synapomorphies:
1. Eusociality
2. True castes
Amitermes hastatus
(primitiveTermitidae)
worker
tertiary queen 2ndary queen
primary queen
17
Pterygota, Neoptera, Polyneoptera:
order Dictyoptera, s.o. Mantodea (mantises)
2400 species, 15 families
ootheca
Pterygota, Neoptera, Polyneoptera:
order Phasmatodea (stick & leaf insects)
3000 species, 2 suborders, several (?) families
order Dermaptera (earwigs)
2200 species, 3 ‘suborders,’ 11 families
s.o. Hemimerina
s.o. Forficulina
order Embioptera (webspinners)
s.o. Arixenina
360 species, 2 suborders, 8 families
Timema sp.
18
Pterygota, Neoptera, Polyneoptera:
Order Orthoptera (grasshoppers, crickets & katydids)
22,000 species, 2 suborders, many families
suborder Caelifera (11,000 spp):
Acrididae (short-horned grasshopper)
suborder Ensifera (11,000 spp):
crickets, katydids, long-horned grasshoppers
ear
ear
Specialized Neoptera without complete metamorphosis:
the Paraneoptera
Crustacea? Myriapoda?
Hexapoda
Collembola
Protura
Diplura
Insecta
Dicondylia
Pterygota
= aquatic immatures
Neoptera
Archaeognatha
Zygentoma
Ephemeroptera
Odonata
Plecoptera
Polyneoptera**
Paurometabola (orthopteroids)
complete metamorphosis
Eumetabola
Endopterygota (Holometabola)
Paraneoptera (hemipteroids)**
(** ‘Exopterygota’)
19
Pterygota, Neoptera, [Eumetabola], Paraneoptera:
the smaller “hemipteroid” orders
(orthopteroid) order
Zoraptera
(39 spp)
order Thysanoptera: thrips
‘Psocoptera:’ book lice (5500 spp)
(6000 spp)
order
Psocodea:
lice
(11,000 spp)
‘Phthiraptera:’
‘s.o.’ Mallophaga,
‘s.o.’ Anoplura,
biting lice (4450 spp) sucking lice (550 spp)
Pterygota, Neoptera, [Eumetabola], Paraneoptera:
more thrips (Thysanoptera)
soldier caste, Carcinothrips leai
(Australia)
20
Pterygota, Neoptera, Paraneoptera: Order Hemiptera (bugs)
3 (or 4) suborders, >133 families, >2000 genera, 100,000 species
(size: 1mm - 110mm!)
s.o. Auchenorrhyncha (40,000 spp): cicadas and hoppers
Membracidae:
tree hoppers
Cicadellidae:
leaf hoppers
Cicadidae: cicadas
s.o. Sternorrhyncha (25,000 spp):
aphids, scales, whiteflies, other plant lice
Fulgoroidea: plant hoppers
s.o. (?) Coleorrhyncha
(34 spp) Peloridiidae –
Gondwanan distrib.
s.o. Heteroptera (30,000 spp): “true bugs”
Lygaeidae (seed bugs)
Coreidae (squash bugs)
Pentatomidae (stink bugs)
Miridae (plant bugs)
(heteropterous wing)
Nepidae (water bugs)
21

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