Invertebrate & Vertebrate
Chordates
Exercise 17, 18
Goals for today
• Learn to recognized the different subphyla of
chordates from other animals
• Learn the main ‘diagnostic’ characteristics of
the group.
• Learn about some species biology
Today we will study the two invertebrate chordates:
Subphylum Urochordata & Subphylum Cephalochordata
and we will studying vertebrate chordates starting today with the
fishes: lampreys, sharks, and bony fishes
Phylym Chordata
Chordates show a remarkable diversity of form and function ranging from
protochordates (invertebrate chordates) to humans.
Hallmark characteristics of chordates:
1. Notochord-cartilage like connective tissue,
early endoskeleton.
2. Pharyngeal pouches and slits-water passes
through the gills
3. Dorsal tubular nerve cord-with
modifications (the brain) is hollow
contrasting that of invertebrates which is
ventral and solid
4. Endostyle or thyroid gland-secretes mucus
5. Postanal tail
Phylum Chordata
Subphylum Urochordata (tunicates)
Subphylum Cephalochordata (anfioxus)
Subphylum Vertebrata
Superclass Agnatha
Class Petromyzontida-lampreys
Class Myxini-hagfishes
Superclass Gnathostomata
Class Condrichthyes-sharks, rays, skates
chimaeras
Class Actinopterygii-bony fish
Class Amphibia (next week)
Class Reptilia (next week)
Subclass Aves (following week of lab)
Class Mammalia (following week of lab)
Invertebrate Chordates
Subphylum Urochordata — Tunicates
Characteristics
• Notochord, dorsal nerve
cord, and tail only
present in larval stage
• Adults usually softbodied sac-like, sessile
filter feeders
Subphylum Urochordata
Exercise 17A:
– Phylum: ChordataSubphylum
Urochordata
• Common name: tunicates
Can you tell what hallmark
structures of chordates are Not
present in the tunicate adult?
What is the tunic?
Exercise 17A:
– Phylum: Chordata
– Subphylum Urochordata
• Common name: tunicates
Find in your box a slide of a larvae tunicate and identify the labeled
structures.
The tunicate larvae has all the 5 hallmark characters of chordates
Subphylum Cephalochordata —
Lancelets
Characteristics
• Elongate, laterally flattened,
fish-like animals
• Tail and notochord persist
throughout life
• Presence of tail (caudal) fin
• Notochord extends anteriorly
past nerve cord
• Muscles segmented into
myomeres
• Burrow in marine sediments
Subphylum Cephalochordata —
Lancelets
Exercise 17B:
– Phylum: Chordata
– Subphylum Cephalochordata
• Common name: lancelets or Amphioxus
Find in your box a slide of a amphioxus and identify the following
parts:
Exercise 17B:
– Phylum: Chordata
– Subphylum Cephalochordata
• Common name: lancelets or Amphioxus
You probably have a transverse cut of
the amphioxus, try to identify the
following parts of their body
What is the wheel organ?
Subphylum Vertebrata — Vertebrates
Characteristics
• Brain enclosed in cartilaginous or bony
cranium
• Fewer pharyngeal gill slits (used for
respiration instead of feeding)
• Notochord supplemented by or replaced
with segmented vertebrae in most
• Larger, more complex brain and sense
organs
• More complex visceral organs
• Includes fishes (jawless, cartilaginous,
and bony), amphibians, reptiles, birds,
and mammals
Superclass Agnatha (jawless fish)
Class Petromyzontida
Common name-lampreys
Characteristics
• Elongated, jawless, scaleless,
lacking paired fins
• Incomplete cartilaginous
vertebrae along sides of
notochord
• Dorsal fin
• 2 semicircular canals
• External parasites of other
vertebrates
Lampreys
• Distributed worldwide
• Most are anadromous: marine
that ascend rivers and streams
to spawn
• Ammocoete larvae live
freshwater habitats 3-5 years
then metamorphose into adult
and become parasites of fishes,
in marine species they go to
the sea
• They suck out blood and body
fluids of their host
Exercise 18A:
– Phylum: Chordata
– Subphylum Vertebrata
• Superclass Agnatha (jawless fish)
• Class Petromyzontida
• Common name-lampreys
Petromyzon
External Anatomy
Exercise 18A:
– Phylum: Chordata
– Subphylum Vertebrata
• Superclass Agnatha (jawless fish)
• Class Petromyzontida
• Common name-lampreys
Internal Anatomy
Many species of lampreys are
parasitic, using their suctorial mouths
(3) to attach to other fishes and a set
of horny teeth (2) on their tongues (4)
and lining the buccal cavity (1) to
bore through the skin to feed on body
fluids. These attacks often prove
fatal, and sea lampreys are blamed
for the extensive damage they have
caused to game fish populations in
the Great Lakes and many other lakes
in North America. Note the dorsal
hollow nerve cord (7) that terminates
anteriorly as a small brain (6) and the
persistent notochord (8) that takes
the place of vertebrae as the principal
axial support.
The above image shows some of the
organs and structures that can be
seen in a cross section of a lamprey
taken from the anterior region of
the animal. Note once again the
dorsal hollow nerve cord (1) and
persistent notochord (2). Also seen
in the cross section are many eggs
within the ovary, the heart and the
liver.
Exercise 18A:
– Phylum: Chordata
– Subphylum Vertebrata
• Superclass Agnatha (jawless fish)
• Class Petromyzontida
• Common name-lampreys
Lamprey, ammocoete larvae
Find in your box a slide of an ammocoete larvae and identify the
following parts:
Superclass Gnathostomata (vertebrates with jaws)
Class Chondrichthyes
Characteristics
• Jaws (with calcified teeth in
extant groups)
• Serially arranged vertebrae
• Pectoral and pelvic girdles
support paired fins
• Skeleton composed of cartilage
(no bone)
• Heterocercal tail
• Placoid scales
• Claspers on male pelvic fins
Subclass Holocephali — Chimaeras
Characteristics
• Enlarged head with beak-like
teeth
• Mostly scale-less body
• All but one pair of gill slits
covered
• 2 dorsal fins
• Marine; mostly deep water
Chamaeras are consider living fossils
Subclass Elasmobranchi — Sharks &
Rays
Characteristics
• Retain many primitive
gnathostome characteristics
• Body covered in scales
• 5-7 externally visible gill slits
• Ampullae of Lorenzini
Subclass Elasmobranchi — Sharks &
Rays
Order Rajiformes
• Skates and rays (539 species)
• Body flattened with enlarged
pectoral fin fused to head
• Gill slits on ventral surface
• Eyes located dorsally
• Lack anal fin
• Most are bottom dwellers; some
occur in fresh water
• This order is sometimes split into
several separate orders
Some are dangerously electric!
Subclass Elasmobranchi — Sharks &
Rays
Order Carcharhiniformes
• Ground sharks (217 species)
• Most species-rich order of
sharks
• Contains most of the familiar
species (such as sand sharks,
leopard sharks and
hammerheads)
Subclass Elasmobranchi — Sharks &
Rays
Order Orectolobiformes
• Carpet sharks (32 species)
• Mouth is located anterior to
eyes
• Nasoral grooves with barbels
• Most are slow moving bottom
dwellers
Subclass Elasmobranchi — Sharks &
Rays
Order Squaliformes
Dogfish sharks (98 species)
2 dorsal fins, each with a spine
Lack anal fin
Tend to be bottom-dwelling
All are ovoviviparous
See also
Exercise 18B:
– Phylum: Chordata
– Subphylum Vertebrata
• Superclass Gnathostomata (vertebrates with jaws)
• Class Chondrichthyes
• Common name-dogfish shark
Genus Squalus
male
claspers
Female
Exercise 18B:
– Phylum: Chordata
– Subphylum Vertebrata
• Superclass Gnathostomata (vertebrates with jaws)
• Class Chondrichthyes
• Common name-dogfish shark
Genus Squalus
External Anatomy
http://www.cumberland.k12.il.us/schools/chs/Starwalt%20Projects/Shark%20Web%2
0Pages/vertebrate_biology_shark_dissect.htm
Exercise 18B:
– Phylum: Chordata
– Subphylum Vertebrata
• Superclass Gnathostomata (vertebrates with jaws)
• Class Chondrichthyes
• Common name-dogfish shark
Genus Squalus
External Anatomy
Touch the shark skin: dermal denticles or placoid
scales
Why sharks are dark dorsally and light
ventrally?
countershading
Lorenzini ampullae
• The ampullae of Lorenzini
are special sensing organs
called electroreceptors,
forming a network of jellyfilled pores. They are mostly
discussed as being found in
cartilaginous fishes (sharks,
rays, and chimaeras);
however, they are also
reported to be found in
Chondrostei such as Reedfish
and sturgeon. Lungfish have
also been reported to have
them.[
wikipedia
Sharks Dissection
Internal Anatomy
ventricle
Gallbladder
Right Testis
liver
stomach
duodenum
Liver
Ilium
spleen
pancreas
liver
liver
Conus Arteriousus
Gills
Ventricle
Atrium
Sinus venosus
Transverse septum
Ilium
Spiral valve
Colon
Sperm sac
Rectal gland
spleen
stomach
Sperm duct-ducto deferente
kidney
Dorsal aorta
Portions of the reproductive tract from
female specimens. A. nidamental glands,
B. uteri © FLMNH
Shark Conservation: Finning
•
•
•
Shark finning
Shark finning refers to the removal and retention
of shark fins and the discarding of the rest of the
fish. Shark finning takes place at sea so the fishers
only have to transport the fins.
Shark finning is widespread, and largely
unmanaged and unmonitored. Shark finning has
increased over the past decade largely due to the
increasing demand for shark fins for shark fin soup
and traditional cures particularly in China and its
territories, and as a result of improved fishing
technology and market economics.
Some researchers believe that from 1996 to 2000,
26 to 73 million sharks were traded yearly. The
annual median for the period was 38 million,
nearly four times more than the UN estimates but
considerably lower than those of many
conservationists.[1] Shark fins are a billion dollar
industry
http://www.youtube.com/watch?v=jA5sjkdHrY&feature=related
Wikipedia
Class Osteichthyes — Bony Fishes
Characteristics
• Endochondral (from cartilage)
bone
• Operculum covers gill openings
• Complex skull structure
• Fin rays (lepidotrichia)
• Air sac functions as lung or swim
bladder
• Ganoid, cycloid, or ctenoid scales
• Most have homocercal tail
Subclass Sarcopterygii: Actinistia —
Coelacanths
Characteristics
• Large size (~2m)
• Distinctive caudal fin with 3
divisions
• Fins muscular, limb-like ("lobed")
• Skeleton mostly cartilagenous
• Modern species are marine, in
deep water
• 2 extant species (first one
discovered in 1938)
Subclass Sarcopterygii: Dipnoi —
Lungfishes
Characteristics
• Elongated bodies
• Dorsal, caudal, anal fins fused
into single rear fin
• Fins flipper-like or reduced to
long filaments
• Paired lungs
• Live in tropical rivers or swamps
prone to drying
• 6 living species
Subclass Actinopterygii — Ray-finned
fishes
Characteristics
• Very diverse: 42 Orders, 431
Families, over 27,000 species
• Fins supported entirely by fin
rays
• Single dorsal fin (though it may
be subdivided)
• Ganoid (primitive) or cycloid
(derived) scales
• 4 primitive Orders (<50 species
total); rest belong to clade
"Teleostei"
http://www.savalli.us/BIO370/Diversity/04
eichthyes.html
Exercise 18B:
– Phylum: Chordata
– Subphylum Vertebrata
• Superclass Gnathostomata (vertebrates with jaws)
• Class Actinopterygii-bony fishes
• Common name-yellow perch
Genus Perca
Exercise 18B:
– Phylum: Chordata
– Subphylum Vertebrata
• Superclass Gnathostomata (vertebrates with jaws)
• Class Actinopterygii-bony fishes
• Common name-yellow perch
Genus Perca
Exercise 18B:
– Phylum: Chordata
– Subphylum Vertebrata
• Superclass Gnathostomata (vertebrates with jaws)
• Class Actinopterygii-bony fishes
• Common name-yellow perch
Genus Perca
Non-paired fins include the first dorsal fin (1) and the second dorsal fin and ventral anal fin seen
the next page. Of the two sets of paired fins, only the pelvic fin (2) is shown; the pectoral fins an
operculum (a bony flap that covers and protect the gills) have been removed to facilitate the
dissection. Internal structures that can be seen on the dissection mount include the gills (3), hea
(4), brain (5), dorsal nerve cord (6), liver (7), stomach (8), gonad (9) and intestine (10). The posit
Bony Fish scales
Shark for comparison
Bony Fish skeleton