Chapter 23 Phylum Chordata Sub-phyla: Urochordata, Cephalochordata & Vertebrata Superclasses: Agnatha & Gnathostomata

Five Chordate Hallmarks A. Notochord B. Dorsal Tubular Nerve Cord C. Pharyngeal Slits D. Endostyle or Thyroid E. Post Anal Tail

Five Chordate Hallmarks Notochord Longitudinal flexible rod extending the length of the body It is present throughout the life of jawless vertebrates In most adult vertebrates, it is replaced by cartilage or bone vertebrae although it may remain between or within the vertebrae

Lamprey

Five Chordate Hallmarks Dorsal Tubular Nerve Cord Nerve cord lies dorsal to the alimentary canal The anterior end becomes enlarged to form the brain and the remainder becomes the spinal cord

Five Chordate Hallmarks Pharyngeal Slits or Pouches Opening that lead from the pharyngeal cavity to the outside In tetrapods, the pharyngeal pouches give rise to a variety of structures including the Eustachian tubes, parathyroid glands, tonsils and middle ear cavity In fish, the structures become fully functioning gills used in respiration and filter feeding in some

Pharyngeal Slits in Sharks & Lamprey

Five Chordate Hallmarks Endostyle or Thyroid Gland The endostyle or thyroid gland is a recent addition as a chordate characteristic In primitive chordates, the endostyle functions to secrete mucous and aids the pharynx in filter feeding In higher vertebrates, the thyroid secretes iodinated hormones that regulate metabolism Typically located in the pharyngeal area of the body

Five Chordate Hallmarks Post Anal Tail Skeletal & muscular elements that extend past the anus In most vertebrates, it remains as a waggable tail which is useful in balance, propulsion, mobility, etc In humans and some apes, it has become reduced to a few bones at the bottom of the sacrum called the coccyx

Phylum Chordata Sub-PhylumUrochordata (means “tail cord”) About 3000 species commonly called sea squirts Adults are sessile and produce a tough outer layer called a tunic Only sea squirt tadpole larva are motile and exhibit all the chordate hallmarks

Phylum Chordata Sub-Phylum Cephalochordata (means “head-cord”) Lancets are slender, flattened, translucent animals about 5-7 cm long About 25 species are found on sandy bottoms of coastal waters around the world Commonly called amphioxus, it shows all the hallmark characteristics in simple form They are considered a sister form and not an ancestor of the vertebrates

Lancet

Phylum Chordata Sub-Phylum Vertebrata (means “back bone”) divided into two Superclasses Superclass Agnatha (means “without jaws”) Superclass Gnathostomata (means “jawed mouth”)

Phylum Chordata Subphylum Vertebrata Superclass Agnatha – 2 classes Class Myxini (means “slime”) There are 65 species of hagfish They are scavengers &/or predators that feed on annelids, mollusks, crustaceans, and dead or dying fish They have sensory tentacles called barbels used to locate food Sense organs of touch, taste, and smell, but no eyes so they are virtually blind Two keratinized plates rasp away flesh from its prey Can secrete enormous amounts of slime when disturbed thus making them impossible to hold

Phylum Chordata Class Myxini – 65 species of hagfish

Phylum Chordata Subphylum Vertebrata Superclass Agnatha – 2 classes Class Cephalaspidomorphi (means “head shield / body”) There are 22 species of lampreys Their larval form are called ammocoetes and resembles amphioxus Amphioxus

Phylum Chordata Superclass/Sub-phylum Agnatha – 2 classes Class Cephalaspidomorphi (means “head shield / body”) (con’t) They remain in freshwater, filter-feeding stage for 3-7 years Adults can be 15 cm to 60 cm in length They may be parasitic or non-parasitic depending upon the individual species They have 7 pairs of gills that are non-ventilated with water from the mouth Sense organs for touch, taste, smell and well developed eyes Parasitic adults attach to prey with sucker-like mouth and bore a hole in the flesh with their sharp keratinized teeth Non-parasitic adults do not feed as adults, thus they spawn and die within a few months.

Phylum Chordata Superclass Gnathostomata – seven classes Class Chondrichthyes (means “cartilage fish”) Example Sharks

Phylum Chordata Superclass Gnathostomata – seven classes Class Actinopterygii (means “modern bony fish”) Example - Tuna

Phylum Chordata Superclass Gnathostomata – seven classes Class Sarcopterygii (means “lobe-finned”) Example Coelacanth and lungfish

Phylum Chordata Superclass Gnathostomata – seven classes Class Amphibia -(means “double life”) Example - Frogs

Phylum Chordata Superclass Gnathostomata – seven classes Class Reptilia means (“to creep”) Example – Snakes, Turtles, Lizards

Phylum Chordata Superclass Gnathostomata – seven classes Class Aves means (“to fly”) Example - Birds

Phylum Chordata Superclass Gnathostomata – seven classes Class Mammalia means “(breast animal”) Example – humans, horses, dogs, dolphin

Phylum Chordata Class Vertebrata General Characteristics: Highly specialized tripartite brain which is encases in a protective skull with 12 pairs of cranial nerves Backbone which is encloses a nerve cord The vertebrae are grouped into five regions-33 total vertebra Cervical (neck)-7 vertebra Thoracic (chest) -12 vertebra Lumbar (back)-5 vertebra Sacral (pelvic)- 5 fused vertebra Caudal (tail)-4 partially fused vertebra

Phylum Chordata Class Vertebrata General Characteristics: (con’t) Endoskeleton composed of bone or cartilage or a combination of both Axial skeleton includes the bones of the skull, ribs and backbone Appendicular skeleton includes the bones of the arms and legs Pectoral Girdle located anteriorly and attached to the forelimbs Pelvic Girdle located posteriorly and attached to the hind limbs

Axial Skeleton

Appendicular Skeleton

Pectoral Girdle

Phylum Chordata Class Vertebrata General Characteristics: (con’t) Paired sense organs specialized for sensing vibrations in water called a “lateral line” Well developed and complex nervous system CNS – Central Nervous System – made up of the brain & spinal cord PNS – Peripheral Nervous System – made up of the nerves that connect to the organs, muscles, and epidermis

Phylum Chordata Class Vertebrata General Characteristics: (con’t) 4-legged = tetrapod 5-digits = pentadactyl