Transcript Animalia III

Last day... surveying Animalia, were into the Ecdysozoa,
and started introducing the phylum Arthropoda
sun spider
Introduced the subphylum Cheliceriformes…
- named for chelicerae: claw-like feeding appendages, used
as pincers or fangs
- most of ~100,000 spp. are arachnids – spiders, ticks, mites,
scorpions, harvestmen & sun spiders
- cheliceriforms also include horseshoe crabs & perhaps
sea spiders
Cheliceriforms have body w. cephalothorax & abdomen
- no antennae, but most have simple eyes
- 6 pairs of appendages start w. pedipalps – sensory, feeding
& reproduction
- then chelicerae & 4 pairs of walking legs
- respiration
using book
lungs
Spiders spin silk (a protein) for webs, escape lines, egg
protection & transport using silk glands & spinnerets
Some webs awfully big…
- communal web at Texas park covered ~200 yards along trail
Horseshoe crabs common along Atlantic coast, but
over-exploited as bait, fertilizer & for hemolymph
(used in test for bacterial toxins)
- spawn en masse at high tides in May-June, eggs vital
for many birds
Sub-phylum Myriapoda - millipedes & centipedes
- both groups have antennae & 3 pairs of feeding appendages
Millipedes eat dead or live plants, 2 pairs of legs/segment
- may release toxins from pores along side for defense
Centipedes are predators, 1 pair of legs/segment
- have poison claws on first limbs for prey capture
Subphylum Hexapoda – insects, springtails, etc.
- formerly all considered insects, now those without wings
excluded
- 3 pairs of legs, body divided into head, thorax & abdomen,
antennae present
Springtails among most abundant terrestrial animals,
100,000/m3 soil?, but usually < 6mm
- mostly eat detritus & microbes
- forked ventral structure can snap down to propel them
into air
More species of insects (~1,000,000) described than all
other organisms together
- abundant in almost all terrestrial habitats, fresh water &
in air, though rare in marine habitats
- appear in Devonian, but evolution of flight in Carboniferous
& Permian apparently led to major radiation
Insects have many negative impacts in crop losses, disease
transmission, damage to buildings, etc., but also huge
benefits in pest control, food for wildlife (& people), etc.
Flight likely important to success of insects – can evade
predators, find food, disperse to new areas
- wings are extensions of cuticle (not true appendages)
- wings may have evolved from structures for heat gain or
swimming or gliding, or used as gills
Most insects have 2 pairs of wings, like dragonflies
Diptera have 1 welldeveloped pair
Wings of bees &
wasps hooked
together
Butterfly & moth
wings overlap,
so work as unit
Beetles have front
wings modified
as cover (elytra)
Insects have: compound eyes & antennae
- complex mouthparts, typically 7 parts
- spiracles & tracheal tubes for respiration
- malphigian tubules to remove wastes from body
Insect diversity overwhelming, but 4 orders very speciose:
Coleoptera – beetles
~350,000 spp.
- chewing mouthparts,
varied diets, but often
herbivores
Diptera – flies
~151,000 spp.
- mouthparts for
sucking or lapping
(nectar, blood, sap, etc.)
Hymenoptera – bees & wasps
~125,000 spp.
- chewing or sucking
mouthparts
- many parasitoids
Lepidoptera – butterflies
& moths - ~120,000 spp.
- sucking mouthparts,
usually feed on nectar
Subphylum Crustacea – the crustaceans, including crabs,
shrimp, isopods, copepods & krill
- dominant arthropods in marine systems, also in freshwater & (less numerous) in terrestrial habitats
mantis shrimp
Crustaceans have large numbers of specialized appendages
- 2 pair of antennae, 3 pair as mouthparts, appendages on
abdomen as well as thorax
- appendages typically biramous (2 branches)
- larger species have gills
Crustacean classification complex, but some important
groups:
Order Decapoda – includes crabs, shrimps, lobsters &
crayfish
- cuticle hardened by calcium carbonate, carapace over
cephalothorax
Order Isopoda – isopods, pill bugs
- generally small, though some large spp. in deep ocean
- many terrestrial spp. (pill bugs, wood lice, roly-polies…)
Order Copepoda – copepods
- small (1-2 mm) crustaceans in oceans & freshwater,
some in damp forests & puddles, about half are
parasites on or in aquatic animals
- most important component of global zooplankton, very
important in carbon cycle & food webs
Infraclass Cirripedia – the barnacles
- most fixed to substrate by cement glands at base of
forehead, secrete shell of (typically) 6 plates
- feet stick out, beat them to draw in water & food
- strictly marine, & mostly shallow water
Have polished off
arthropods & Ecdysozoa,
only 2 (major) phyla left…
What is an echinoderm?
First phylum of the Deuterostomia: Phylum Echinodermata
- the echinoderms include sea stars (starfish), sea urchins
& relatives
- ‘spine skin’ – have thin epidermis over calcareous plates,
which often have bumps & spines
Genetic evidence confirms position as deuterostomes (radial
cleavage, anus from blastopore, etc.) as well as Bilateria
- adults (mostly) radial, but larvae bilateral
- have a water vascular system
w. water-filled canals
connected to tube feet
- feet for locomotion,
feeding, & gas
exchange
- water enters &
exits through
madreporite
Echinoderms divided into 6 classes (5 major)…
Class Asteroidea – Sea stars - ~2,000 spp.
- slow moving predators of bivalves, etc.
- use adhesive tube feet to hold & open shells, then partly
evert stomach & release digestive enzymes
- able to regenerate
lost arms, or even
body from a single
arm
Class Ophiuroidea – Brittle stars – 1,500 spp.
- long flexible arms, & relatively fast
- mostly in deeper water
- some are suspension feeders, others are predators or
scavengers
Class Echinoidea – Sea urchins & sand dollars
- urchins are round & spiny, but have tube feet arranged in
5 pairs of rows (like sea stars)
- feed mostly on algae, but also other inverts
- muscles move spines, so can walk on them
- sand dollars are disk shaped & without spines
Class Crinoidea – Sea lilies & feather stars - a few hundred
living spp., but more diverse in past
- some in shallow waters, but some to 6,000 m deep
- sea lilies attached by stalk, feather stars crawl around but
mouth points upward
- many arms, used in filter-feeding
Class Holothuroidea – Sea cucumbers
- look very different: elongated body, endoskeletal plates
greatly reduced
- but, 5 rows of tube feet extend from mouth back
- mostly scavengers, may be abundant in deeper waters
- can eject certain organs & a toxin from anus as a defense
Phylum Chordata – the Chordates
Arthropoda
Nematoda
Rotifera
Annelida
Mollusca
Nemertea
Platyhelminthes
Ectoprocta
Phoronida
Brachiopoda
Chordata
Echinodermata
Cnidaria
Ctenophora
Silicarea
Calcarea
“Radiata”
“Porifera”
Deuterostomia
Lophotrochozoa
Ecdysozoa
Bilateria
Eumetazoa
Metazoa
Ancestral colonial
flagellate
About 52,000 spp. of chordates, but just one small branch in
phylogeny of animals
A Chordate Phylogenetic Tree
Characteristics of Chordates
• Notochord – flexible rod
between digestive tract
& nerve cord
- Dorsal hollow nerve cord
- Pharyngeal gill slits
– in embryos if not adult
- Muscular post-anal tail
Subphylum Cephalochordata - Lancelets
Small (to 5 cm) suspension
feeders, bury posterior end
in sand
Swim with chevron-shaped
muscles flexing body
Adults have notochord, dorsal hollow nerve cord,
pharyngeal slits, post-anal tail
Muscle segments develop from serial blocks of
mesoderm, called somites
Subphylum Urochordata – Tunicates or Sea Squirts
- marine animals, most
sessile suspension feeders
- quite diverse (~2,000 spp.)
- our relatives???
Incurrent
siphon
to mouth
Notochord
Excurrent
siphon
Dorsal, hollow
nerve cord
Excurrent
siphon
Tail
Excurrent
siphon
Atrium
Pharynx
with
numerous
slits
Tunic
Incurrent
siphon
Intestine
Stomach
Atrium
Anus
Intestine
Esophagus
Pharynx with slits
Stomach
(a) An adult tunicate, or
sea squirt, is a sessile
animal (photo is
approximately life-sized).
Muscle
segments
(b) In the adult, prominent
pharyngeal slits function
in suspension feeding,
but other chordate
characters are not obvious.
(c) A tunicate larva is a freeswimming but nonfeeding
“tadpole” in which all four
chief characters of chordates
are evident.
Chordate characters seen mostly in larvae
- metamorphosis: tail & notochord resorbed,
nervous system degenerates, organs rotate 90˚
Chordate Phylogeny
Craniates
– have a
‘head’
The Craniates
Derived characters include:
- two clusters of Hox genes (only one in lancelets
& tunicates)
- other families of genes that produce signaling
molecules & transcription factors also duplicated
- neural crest cells form near dorsal margins of
closing neural tube of embryo
- pharyngeal clefts evolve into gill slits
- skull of cartilage or bone
Dorsal edges
of neural plate
Neural
crest
Neural
tube
Ectoderm
Ectoderm
Notochord
(a) The neural crest consists of
bilateral bands of cells near
the margins of the embryonic
folds that form the neural tube.
Migrating neural
crest cells
(b) Neural crest cells migrate to
distant sites in the embryo.
(c) The cells give rise to some
of the anatomical structures
unique to vertebrates, including
some of the bones and cartilage
of the skull.
Neural crest cells – from ectoderm near neural tube
- form certain bones, neurons, smooth muscle
& hormone producing cells