Myriapods Flashcards
Myriapoda
Myriapods are the members of subphylum Myriapoda
Myriapods
(translates as ‘ten-thousand
feet’):
● ~18,000 species
● All extant species are terrestrial
● Body separated into head & trunk
● No pedipalps
● Single pair of antennae
● Mandibles for feeding (modified in centipedes as fangs)
● Thoraxic segments with 1 or 2 pairs of legs
Conquest of Land
Myriapods are thought to have been the first
group to invade land
Mandibulata
Arthropods with mandibles
The anterior most mouthpart, possibly derived from gnathobase or limb-tip
Cryptozoa
Are animals in “Cryptic” or hidden habitats- detritus; decaying wood; leaf litter
Why are cryptozoa in cryptic habitats
● Habitats have had little change for hundreds of millions of
years, benefiting unspecialised animals
↳ Dessication & gas exchange
↳ Slow moving
↳ Comparatively poor senses
● Evolutionarily outpaced by other groups, and the other niches are now filled
Myriapod gas exchange
● Gas exchange is accomplished with
simple diffusion through Trachea
● One pair of spiracles per segment in
Myriapods
● Tracheoles feed O2 directly into
tissues
● Haemolymph is not used to
distribute O2
● Heart is a simple dorsal tube
Chilopoda
(Centipedes, translates as “hundred feet”)
● ~3,600 species
● Contrary to their name, none can have 100
legs; legs are always in odd numbers of pairs
from 15 to 191 pairs
● Worldwide distribution, but particularly N.
America, Europe & Australia
● Scolopendromorphs often coloured red,
green, yellow, blue etc; most other species
brown/black
● Tropical species sometimes large (30cm)
Forcipules
Covering the mandibles are a pair of
forcipules (AKA poison claws) that are
derived from legs
Chilopoda feeding & nutrition:
● Typically generalist predators – many eat
small inverts, but some also eat amphibians, snakes, birds, bats, mice
Chilopoda defences
● Cryptic habitats & burrows
● Pinching anal legs in some species
● Anal legs sometimes have as many sensory hairs as main antennae
(able to sense attacks)
● Anal legs also visually mimic antennae to trick predators
● Anal legs can be autotomised in some species
Most centipedes are adapted to run and have long legs
↳ Legs get longer from anterior to posterior (to reduce interference)
↳ Pushing force is provided by expansion & contraction of the trunk (like earthworm), creating a metachronal wave (like a Mexican wave) and by bending the body
● Some are adapted for burrowing through soil and humus and have short legs that anchor the body (soil centipedes)
Chilopoda Mating
● Females have a single ovary males have one or more testes
● Females and males have a gonopod (penultimate pair of legs before anal legs) which aids in handling of the spermatophore
● Sperm transfer is indirect - via a spermatophore
↳ Spermatophores are place on web of silk (like Arachnids)
↳ Female picks up spermatophore with her gonopods and places it in her genital tract
Diplopoda
Diplopoda (Millipedes, translates as “thousand feet”)
● ~13,900 species
● Worldwide distribution, but particularly in tropics
● Range in size from 2mm to 28cm
Defence mechanism in diplopoda
Repugnatorial glands produce cocktail of secretions to deter predators, including alkaloids, aldehydes, phenols and hydrogen cyanide
Signalling Diplopoda
Warning colours to signal their chemical defences
to predators (aposematism)
Bioluminescence thought to be aposematic (warning) signal, given they can generate and discharge hydrogen cyanide through repugnatorial glands
