Chordata

Phylum Chordata Subphylum Urochordata Subphylum Cephalochordata Vertebrata tunicates lancets Agnathans Fish Sharks tetrapods

Characteristics of Chordates

Possible evolution of 1st fish lancelet Proto-vertebrate Tunicate larvae Adult tunicate

Early Chordate ancestor may have given rise to 1st vertebrate Pikaia Burgess Shale Fauna Cambrian 540-500 mya

General Features Shared by Chordates: Eukaryote Multicellular Bilateral- deuterstomes Heterotrophic

Phylum Chordata Subphylum Urochordata - Tunicates Class Ascidiacea - Sea Squirts Solitary e.g. Styela montereyensis Colonial - in groups but with own tunic Compound Colonial - colonial with shared tunic Class Thaliacea - Salps (free swimming), planktonic Class Larvacea - Gelatinous house, planktonic

Subphylum Urochordata tunicate

Subphylum Urochordata = tunicate Tunicate - also called 'sea squirt' notochord is confined to the tail notochord is lost during metamorphosis into sessile adult possess pharyngeal slits Repro- sexual (hermaphroditic) & asexual (budding)

Tunicate Adult Anatomy

Tunicates: Free swimming larva: notochord present only in free-swimming  larvum notochord does not extend into head larvum is free-swimming but non-feeding adult is sessile filter feeder Settled larva: Settle after brief free-swimming larvum existence.  Attaches at anterior end.  Metamorphosis begins.  Body turns 1800.  Tail, notochord, dorsal nerve cord, disappear.

Class Larvacea - planktonic Oikopleura

Class Larvacea - Gelatinous house, planktonic Jelly-like house Oikopleura Marine snow

Class Thaliacea - Salps (free swimming), planktonic Pyrosoma- bioluminescent Colonial salp

Class Ascidiacea - Sea Squirts

Subphylum Cephalochordata lancet Strictly marine Live buried in sand with head sticking out Filter feeders

Lancet Anatomy