Subphyllum uniramia/Myriapoda; Class Chilopoda: centipedes; Class Diplopoda: Millipedes; Class Pauropoda: pauropods; Class Symphyla: garden centipedes; mandibulates A summary of Subphylum Myriapoda with illustrations. Each class is described as well as the general characteristics of the subphylum.

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Subphylum Myriapoda
Diversity of animals II
- Include
• Chilopoda, centipedes
• Diplopoda, millipedes
• Pauropoda, pauropods
• Symphyla, symphylans
- unbranched appendages
- Myriapod - Gr. Myrias, a myriad + podos, foot
- two tagmata (head and trunk) with paired appendages on most or all trunk
somites
- Insects - 3 tagmata - head, thorax, abdomen; appendages on the head and
thorax; greatly reduced or absent from the abdomen
- head of myriapods and insects resemble the crustaceans but has only one pair of
antennae instead of two.
- Mandibles
- 2 pairs of maxillae in millipedes
- legs are all uniramous
- respiratory exchange by body surface and tracheal system; if aquatic may have
gills
- excrete through malpighian tubules
Class Chilopoda: centipedes
- active predators
- moist places - under logs or stones
- feed on earthworms, insects
- bodies somewhat flattened dorsoventrally
- may contain a few to 177 somites
- each somite, except the one behind the head and the last two, bears one pair of
appendages
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- somites of the first body segments are modified to form poison claws - used to
kill prey; poison often toxic to human beings; bites extremely painful, sometimes
dangerous
- most species harmless to humans
- 15-193 leg-bearing body segments
- long legs extending laterally ; last pair of legs extend backwards and not used for
locomotion
- heads bears a pair of eyes, each consisting of a group of ocelli (simple eyes)
- simple antennae with varying degree of segmentation
- both pairs of maxillae may be medially coalesced
- cuticle stiff ; uncalcified
- gonopores on last true body segment
- spiracles lateral or mid-dorsal (but on the pleural side wall)
- Respiration by tracheal tubes with a pair of spiracles in each somite.
- separate sexes
- all species oviparous
- fertilization internal
- young similar to adults
- Common genera
• Common house centipedes Scutigera, with 15 pairs of legs, and
• Scolopendra with 21 pairs of legs,
Class Diplopoda: Millipedes
- Diplopods or “double footed”
- cylindrical bodies
- 20 -25 segments
- 4 thoracic segments with one pair of legs each + abdominal segments with 2
pairs called diplosegments
- 2 pairs of spiracles on each abdominal somite - each opening into an air chamber
- tracheal tubes
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- In each segment of their body, most millipedes have a pair of complex glands that
produces a bad-smelling fluid. This fluid is exuded for defensive purposes
through openings along the sides of the body. Some produce cyanide gas from
segments near their head end.
- lateral repugnatorial glands on the trunk segments that secrete noxious chemicals
that can irritate the skin and eyes
- less active than centipedes
- Many millipedes can roll their bodies into a flat coil or sphere because the dorsal
area of each of their body segments is much longer than the ventral one
- herbivorous; few carnivorous
- live on decayed plant and animal matter and sometimes living plants
- Habitat: dark moist places
- lay eggs in nest
- larval forms have only one pair of legs per somite; Young millipedes usually hatch
with three pairs of legs
- fertilization internal
Class Pauropoda: pauropods
- (Gr. pauros, small, + pous, podos, foot)
- minute ( 1-1.5 mm)
- not common
- cylindrical body with double segments
- 9-10 pairs of legs
- no eyes
- some trunk segments partly fused
- free telson
- no limbs on first true segment
- mouthpart poorly developed
- first maxillae fused into a gnathochilarium; second maxillae absent
- branched antennae
- most without tracheal or circulatory systems
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- gonopores on third trunk segment
- terga often large and extended over two segments
- soft cuticle, uncalcified
- occur mainly in moist soils and woodland litter
Class Symphyla: garden centipedes
- not common
- slender ( 1-8 mm)
- long threadlike antennae
- 15-23 segments with 10-12 pairs of legs
- first 12 trunk segments each with a pair of legs
- penultimate segment with spinnerets and a pair of long sensory hairs
- dorsal surface with 15-22 tergal plates
- soft uncalcified cuticle
- last segment fused to telson
- no eyes
- first maxillae completely fused as complex labium
- one pair of spiracles on head
- trachea supply first 3 trunk segments
- gonopores open on third trunk segment
- occur in soil and rotting vegetation
Characteristics of the subphylum Myriapoda
1. body of two tagmata; head and multisegment true
2. All appendages multi articulate and uniramous
3. Head appendages, from anterior to posterior, are antennae, mandibles, first
maxillae and second maxillae; second maxillae may be fused into a single
flaplike structure called a “labium” ( not homologous to the crustacean
labium). or they may be absent; first and second maxillae often bear palps.
4. Without carapace
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5. With an aerial gas exchange system composed of trachea and spiracles
( probably convergent with those in the Hexapoda)
6. With one or two pairs of ectodermally derived (proctodeal) Malpighian tubules
(probably convergent with those in the Hexapoda)
7. Most with simple ocelli, at least in some stage of the life cycle; true ommatidia
apparently absent
8. Gut simple, without digestive ceca
9. Dieocious; with direct development
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Fig 4. Pauropoda, Fig 5, Symphylan, Fig 6. Centipede

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one pair of appendages. Those of
modified to form poison claws,
prey. Most species are harmless to
of eyes,each consisting of a group
iration is by tracheal tubes with a
omite. Sexes are separate, and all
g are similar to adultS. Common
with 15 pairs of legs,and Scolopen-
airs of legs,are familiar genera.
Millipedes
”arthropods,are commonly called
eans “thousand feet”(figure 12.33).
thousand legs,they do have a great
es are made up of 25 to 100 seg-
ments. The four thoracic segments bear only one pair of legs
each,but abdominal segments each have two pairs,a condition
that may have evolved from fusion of somites.Two pairs of spi-
racles occur on each abdominal somite, each opening into an
air chamber that gives rise to tracheal tubes.
Millipedes are less active than centipedes and are gener-
ally herbivorous,living on decayed plant and animal matter and
sometimes living plants. They prefer dark moist places under
stones and logs.Females lay eggs in a nest and guard them care-
fully.Larval forms have only one pair of legs per somite.
Class Insecta: Insects
Insects are the most numerous and diverse of all groups of
arthropods (figure 12.34). There are more species of insects
than species in all the other classes of animals combined. The
number of insect species named has been estimated at close to
e
s Chilopoda) from the Amazon Basin, Peru. Most segments have one pair of appendages each. First segment bears a
me species can inflict serious wounds. Centipedes are carnivorous. B, Head of centipede.
Antenna Eye
Second maxilla
First maxilla
Maxilliped with
poison fang
First leg Second leg
Second tergumFirst tergum
B
Antenna
Eyes
Mandible
Second segmentFirst segment