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 well- developed 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 fresh- water & (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, veryimportant 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 hundredliving 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

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“Radiata”

“Porifera” Deuterostomia Lophotrochozoa Ecdysozoa

Bilateria

Eumetazoa

Metazoa

Ancestral colonialflagellate

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???

(a) An adult tunicate, or sea squirt, is a sessile animal (photo is approximately life-sized).

(b) In the adult, prominent pharyngeal slits function in suspension feeding, but other chordate characters are not obvious.

(c) A tunicate larva is a free-swimming but nonfeeding“tadpole” in which all four chief characters of chordates are evident.

Tunic

Pharynxwith

numerousslits

Atrium

Excurrentsiphon

Incurrentsiphonto mouth

Stomach

Esophagus

IntestineAnus

Excurrent siphon

Pharynx with slits

Notochord

Tail

Dorsal, hollownerve cord

AtriumStomach

Intestine

Excurrent siphon

Incurrentsiphon

Musclesegments

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

Notochord

(a) The neural crest consists of bilateral bands of cells near the margins of the embryonic folds that form the neural tube.

(b) Neural crest cells migrate todistant sites in the embryo.

(c) The cells give rise to some of the anatomical structuresunique to vertebrates, including some of the bones and cartilage of the skull.

Migrating neuralcrest cells

Ectoderm

Ectoderm

Dorsal edgesof neural plate

Neuralcrest

Neuraltube

Neural crest cells – from ectoderm near neural tube- form certain bones, neurons, smooth muscle & hormone producing cells