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HEMICHORDATA & INVERTEBRATE CHORDATES Chordata Characteristics found sometime during their lifecycle • dorsal tubular nerve • • • cord notochord pharyngeal slits or pouches post anal tail Phylum Hemichordata • • Hemi – half Chorda – cord • Characteristics – live in or on marine sediments – marine, animal divided into 3 regions 1) proboscis – mucus and feeding 2) collar 3) trunk – ciliated pharyngeal slits – help with feeding – open circulatory system – complete digestive tract – simple tube – dorsal, sometimes tubular nerve cord Class Enteropneusta Pterobranchia Definition Entero – intestines Pneustikos – for breathing Acorn worms Marine worms Pteron – wing or feather Branchia - gills Examples Habitat pterobranchs Most occupy UDeep oceanic shaped burrows waters in sandy and muddy substrates between high and low tides Size 10 – 40 cm, some 2m .1 – 5 mm Feeding Hepatic sacs – where food is digested Casting – fecal material No major ganglia Gather food by cilia on arms and tentacles to filter feed Respiration Metabolic waste and gases - diffusion Metabolic waste and gases – diffusion Reproduction Dioecious, external fertilization Most dioecious, external fertilization Nervous system Colony No major ganglia Asexual budding for colony formation Acorn worms Pterobranchia Phylum Chordata – (chorda – cord), • successful adapting to aquatic and terrestrial environments – Characteristics • Bilaterally symmetrical, deuterostomate • 4 characteristics at some stage in development – – – – notochord pharyngeal slits or pouches dorsal tubular nerve cord Postanal tail Presence of endostyle (fold in endoderm, which projects into the blood cavity, or thyroid gland, used to regulate metabolism) Complete digestive tract Ventral, contractile blood vessel (heart) Phylum is named after notochord – Noton – the back, chorda – cord supportive rod that extends most of the length of the animal dorsal to the body cavity and into the tail in most adult vertebrates cartiledge or bone partly or entirely replaces the notochord Pharyngeal slits/pouches series of openings in the pharyngeal region between the digestive tract and the outside of the body can break through to form open passageways to the outside – slits don’t break through pouches – used for – filter feeding, feeding, gills for gas exchange. In some terrestrial – maybe incomplete Tubular nerve cord – largely responsible for chordates success. Runs along the longitudinal axis of the body, just dorsal to the notochord and usually expands anteriorly as a brain. – central nervous system – sensory reception, integration, motor response Postanal tail – extends posteriorly beyond the anal opening Subphylum Urochordata • – uro – tail, chorda – cord – – Examples – tunicates & sea squirts Largest class of tunicates – – Examples – tunicates & sea squirts Largest class of tunicates Sessile as adults; either solitary or colonial attach their saclike bodies to rocks, solid substrates unattached end has 2 siphones oral siphon – inlet for water (mouth opening) atrial siphon – excurrent water Tunicates – body covered with a firm external tunic, made of cellulose, proteins, salts, 2 openings, one for entrance one for exit of water. Stolons – rootlike extensions to anchor tunicate to substrate Urochordata Maintenance Functions • Single ganglion • Endostyle - a ciliated tract in the pharynx • • is used in forming mucus for filter feeding Pharynx – used for feeding and gas exchange Heart can pump blood in one direction and then another, we do not know why? Reproduction • Monoecious • Self fertilization in some species, cross fertilization is the rule • Larva, tadpole – metamorphism – sessile adult Cephachordata • – kephalo – head, chorda – cord – – Example – lancelt Throughout worlds oceans in shallow water’s in clean sand substrate Small up to 5cm longs – • • • • • • • Elongated, laterally flattened and nearly transparent Spends most time in filter feeding position Oral hood Cilated fingerlike projections called cirri, used in feeding from oral hood Numerous pairs of pharyngeal slits perforated the pharynx Larger food particles caught by cirri where smaller pieces are caught by the endostyle. Do not posses true heart – muscles in major walls of vessels propel blood. Reproduction • Dioecious, external fertilization metamorphosing into adults.
