Ecdysozoans and Vertebrates Overview

Ecdysozoans

Sister clade to Lophotrochozoa, covered with a cuticle, undergo ecdysis

Ecdysis

Process of molting in ecdysozoans

Nematodes

Unitary, pseudocoelomate, complete gut, plant and animal parasites

Arthropods

Unitary, coelomate, segmented, with jointed appendages

Chelicarates

Group with chelicerae for grabbing food and pedipalps for sensing

Pycnogonids

Sea spiders

Myriapods

Terrestrial arthropods with many legs

Crustaceans

Pancrustaceans with nauplius larval stage

Insects

Tracheae for gas exchange, undergo metamorphosis, important pollinators and pests

Deuterostomes

Embryos undergo radial cleavage, blastopore forms anus, mesoderm develops from archenteron

Echinoderms

Adults have pentaradial symmetry, water vascular system

Chordates

Notochord, nerve cord, pharyngeal slits, post-anal tail

Cephalochordates

Marine chordates

Urochordates

Marine chordates including ascidians, thaliaceans, larvaceans

Vertebrates

Animals with vertebral column and cranium

Cyclostomes

Clade of vertebrates including hagfish and lampreys

Hagfish

No bone, no jaws, filter feeders, mostly parasites of fishes

Lampreys

Cartilaginous skeleton, filter feeders, parasites of fishes

Ecdysis Purpose

Ecdysozoans molt to grow

Insects have diversified tremendously in the past 350 million years. Why?

Insect flight evolved ~350 mya, and was associated with a burst of diversification

Echinoderm & Hemichordate Biology

Echinoderms have pentaradial symmetry, water vascular system; Hemichordates have pharyngeal slits

5. What is the sister taxon to the vertebrates?

Cephalochordata