Fish 1 Flashcards
What 3 phylum did the Chordata split into?
Vertebrata - notochord has been replaced by a backbone
Cephalochordata - ‘head chordates’
Urochordata - ‘tail chordates’
(The last two are invertebrates, but more closely related to vertebrates)
What 5 anatomic structures to Chordates share at some point in their lifecycle?
Notochord Tubular dorsal neve tube Pharyngeal slits Endostyle or thyroid glands Postanal tail (in many species it is lost during embryonic development)
What is a Notochord?
A rod-like flexible structure along the longitudinal axis of the body. It is located between the digestive tube and the nerve cord
Describe the structure of the Notochord
It is composed of a core of large, fluid-filled cells encased in fairly stiff fibrous connective tissue sheath. This enables it to provide support whilst remaining flexible. Allows fast swimming via lateral pressure against the surrounding substrate.
What is the Endostyle?
Occuring in only chordata, the endostyle is a groove in the pharyngeal floor of protochordates. It is a mucus-secreting gland that traps small food, (it is homologous with the thyroid gland.
Discuss the subphylum; Urochordata
Marine dwelling tunicates, seq squirts, salps or larvaceans. Common rock pool animals. They show the 5 chordate characteristics during larval stage. Motile as juveniles, sessile as adults, they undergo a dramatic metamorphosis. They draw water in through a siphon, filtering food particles.
Discuss the subphylum; Cephalochordata
‘Lancelets’ exclusively marine, 25 species. They are capable of swimming but usually buried in the sand with only their anterior end exposed. They are named for their blade like shape, they filter feed. All 5 chordate characteristics are present throughout their entire lives.
What is the neural crest?
Collection of cells that appears near the dorsal margins of the closing neural tube in an embryo. It gives rise to a variety of structures, including some bones and skull cartilage
What did the formation of a head allow? That caused Crainates to thrive?
Opened up a new way of feeding for chordates; active predation. Sensory organs clustered for heightened responses. Increases space for brain development
What are Craniates?
Hagfishes are the only remaining craniates that are not vertebrates. They have a brain case of cartilage or bone, paired eyes and other sensory structures on the head
What is the name given to the first true fish, and name their main characteristics
Agnathans Non-bony (cartilaginous) Fed on algae on the sea floor Armoured Lateral projections Developed fins
