Protostomes (L15+16)

Protostome synapomorphies

schizocoely

Protostomes

Ecdysozoa and Lophotrochozoa

Ecdysozoa

Arthropoda, Nematoda, Nematomorpha, Priapulida

Ecdysis

moulting of cuticle; homologous character that defines Ecdysozoa

Many molecular synapomorphies

between Ecdysozoa and Lophotrochozoa

Segementation in Ecdysozoa may be

a shared character that was lost in some classes

(In Ecdysozoa) Dense mass of

mesoderm forming near the archenteron

Panarthropods

Onycophorans (velvet worms), Tardigrades, Euarthropods

Arthropods are

the biggest group of animals

Euarthropods

Chelicerates, Crustaceans, Insects (Hexapods), Myriapods

Chelicerates

sea spiders, horseshoe crabs, arachnids, sea scorpion (extinct)

Sea spider

(Chelicerate) Pycnogonid

Horseshoe crabs

(Chelicerate) Xiphosuran

Crustaceans

Copepods, Barnacles, Maxillopod crustacea

Barnacles

Cirripedes

Myriapods

Chilopoda, Diplopoda, Symphylan, Pauropoda

Chilopoda

centipedes, one pair of legs per segment

Diplopoda

millipedes, two pairs of legs per segment

Onycophorans

velvet worms

Pancrustacea

group consisting of insects and crustacea

Insects and crustaceans are closely related shown by

changes in mitochondrial gene order

Velvet worms have

poisonous, gluey spit used to catch prey

Tardigrades/Water bears

segmented (1 pair of legs per segment), extremophile

Panarthropod synapomorphies

jointed legs with claws, legs in parasegmental register

Euarthropod and Onycophoran synapomorphies

dorsal ostiate heart, haemocoel

Haemocoel

haemolymph-containing cavity

Haemolymph

blood-like fluid in arthropods

Insect segmentation

head, abdomen, thorax

Chelicerate segmentation

prosoma (head), opisthosoma (legless end)

Tagmatization

segment specialization

Prosoma

head end in Chelicerates

Opisthosoma

legless end in Chelicerates

Introvertan worms

Nematodes, Nematomorphs, Priapulids, Kinorhynchs, Loriciferans

Introvert

spiny retractable proboscis that utilises fluid-filled cavities for motion

Proboscis

elongated sucking mouthpart

Introvert movement

• compresses and forces fluid to front (extension)

• muscles in introvert pull it back into body

• body propelled forward

Properties of Priapulids

radial cleavage, deuterostomy, signs of segmentation (in some groups)

Priapulid larvae

have a tunic/carapace (found in Loriciferan and Kinorhynchs)

Lophotrochozoa

Spiralia and Gnatifera

Bootlace worm

Nemertea (Ribbon worm), Lineus longissimus, longest known animal

Lophophore

extension of the front of the body with ciliated fingers of tissue that catch particles

Trochophore larvae

prototroch around the equator of the body in the larval stage (molluscs and annelids)

Prototroch

wheel of cilia

Lophotrochozoa (Fundamental characters)

Spiral cleavage, Larval stages, Molecular characters

Lophotrochozoa - larval stage

ciliated larva that look similar across species

In Lophotrochozoa larvae the prototroch is

used for motility coordinated by apical organ

Lophotrochozoa larvae have a ciliary tuft

used to sense environment

Spatial colinearity

(Hox genes) order on the chromosome reflects the order of expression

Genes only found in Lophotrochozoa

Lox5 Lox8 Lox4

Spiralia

Molluscs, Annelids, Platyhelminthes, Nemertea

Gnatifera

Chaetognaths, Rotifers, Micrognathozoa, Gnathostomulida

Molluscs

cephalopods, bivalves, snails, gastropods

Mollusc synapomorphies

radula, mantle, anus and genitalia opening in mantle cavity

Radula

chitinous band with rows of teeth

Radula is used

to scrape food off rocks

Radula is located

on top of odontophore

Radula is moved by

radula muscles

Radula is renewed

continuously

Mantle

dorsal layer, responsible for secreting the shell/plate

Shell field cells

evolve rapidly in molluscs

Annelid synapomorphies

closed blood vessel system (only protostome to have one), fundamental metamerism

Metamerism

linear series of body segments fundamentally similar in structure

Annelid metamerism

anatomical units contain nephridium, ganglion of ventral nerve chord, muscles around gut

Nephridium

excretory organ (in Annelid metamer)

Platyhelminthes

flatworms; complex digestive system, single intestinal opening, lack coelom, regenerative abilities

Only group of flatworm to have spiral cleavage and larval stage

Polycladida

Polycladida

only group of flatworm to have spiral cleavage and larval stage

Majority of flatworms are

parasitic

Nemertean synapomorphies

reversible proboscis, rhynchocoel, multiple sensory organs (catch prey)

Reversible proboscis in Nemertea is used to

catch prey

Rhynchocoel

fluid-filled cavity which houses the proboscis

Lophophorata

subgroup of Spiralia containing Brachiozoa and Bryozoa

Lophophorata lack

spiral cleavage

Brachiopods

(Brachiozoa) similar shell to bivalves, deuterostomy

Gnatifera synapomorphies

lack larval stage, pharyngeal hard parts (jaws), may have spiral cleavage

Chaetognaths

tripartite body, grasping spines (jaws), coelomates, hermaphrodites, deuterostomy

Chaetognaths linked to Rotifers in Gnathifera by

MedPost Hox gene

Chaetognaths tripartite body organisation

head, trunk, tail