Chapter 3: Early Chordates and Jawless Fish

What was a major innovation of vertebrates?

-Neural Crest/Tube (a bunch of cells that break away to make stuff like nerves, eyes, etc)

What was Garstang’s hypothesis on larval tunicates

-Larval tunicates never become adults

-Straight from larval tunicates to Cephalochordates and Vertebrates

Explain “calcichordates” and their characteristics

-Marine Organism (sand dollar)

-Calcium carbonate plates all over body

-No evidence of: Pharyngeal gill apparatus, notochord, nerve chord, or segmented musculature

Explain “paedomorphosis”

-Larval or juvenile traits in adults

-Adult retains juvenile characteristics from ancestors

Explain who the “conodonts” are and their characteristics

-Marine organism

-Segmented muscles

-large eyes with muscles

-mineralized exoskeleton

-Dentine and bone cell presence

-MISSING gill apparatus

Explain “ostracoderms” and their characteristics

-Extinct jawless fish

-Bony external cover

-Characterized by: body armor, lack of jaw, and paired fins

Explain where to find hagfish and lamprey

-Hagfish can be found only in Marine environments

-Lamprey can be found in both Marine and Freshwater environments

What characteristics do hagfish and lamprey both lack?

-Jaws

-Paired fins

-Ribs

-Vertebrae

-Thymus

-Lymphatic Vessels

-Genital ducts

What do Lamprey and Hagfish both have?

-Cartilaginous skeletons

What do Hagfish lack but are found in Lamprey?

-Well-developed eyes

-Extrinsic eyeball muscles

-Radial muscles associated with median fin

Describe the characteristics of the integumentary system of hagfish

-Smooth and scaleless

-Thin epidermis (coating mucus)

-Thick and complex dermis

-Hagfish use mucus from pores on side to coat the gills of an enemy and tie in knots

Describe the characteristics of the integumentary system of lamprey

-Smooth and Scaleless

-Thin epidermis (mucus)

-Thick and complex derma

What are the parts of Lamprey and Hagfish cardiovascular system

1)Sinus venosus

2)Atrium

3)Ventricle

4)Conus arteriosus

What are the 3 accessory hearts that hagfish have and their functions

1)Portal Heart (pumps blood from liver)

2)Cardinal Heart (Move blood from head)

3)Caudal Heart (push blood out from tail)

What are the mouth morphology of lamprey

-Mouth inside buccal funnel (tongue with horny epidermal teeth)

-Attaches to host via teeth

What are the feeding habits of lamprey

-Suck on blood and body fluids of other marine animals

-Can be considered parasitic

What is the mouth morphology of hagfish

-Lack oral disks

-Feed Apparatus (two dental plates with two curved rows of sharp horny cusps)

What is the feeding habits of hagfish

-Feed on dead carcass

-Tie itself into a knot to pull on tougher parts on carcass

Describe the digestive system of lamprey

-Food goes in order of pharyngeal region→ esophagus → straight intestine

-Has folds in intestine (Typhlosole) (Gives more surface area to ingest food/nutrients)

-No stomach

-No swim bladder

-Intestines open into cloaca

Describe the digestive system of hagfish

-Has feed apparatus (two dental plates with two curved rows of sharp horny cusps)

-Food goes in order Pharynx → esophagus → straight intestine → cloaca

-No swim bladder

-No stomach

Describe the sensory systems of lamprey

-Has a lateral line system

-Has two lateral eyes

-Both have well-developed olfactory organs, dorsal nostril, and nasophpophysial sac

Describe the sensory systems of hagfish

-Has rudimentary light-sensitive eyes

-Has barbels (helps sense the environment)

-Both have well-developed olfactory organs, dorsal nostril, and nasophpophysial sac

How do lamprey and hagfish differ in their dorsal fins?

-Hagfish doesn’t have dorsal fins

-Lamprey has 1-2 dorsal fins

How do lamprey and hagfish differ in their pre-anal fins?

-Hagfish has a pre-anal fin

-Lamprey doesn’t have a pre-anal fin

How do lamprey and hagfish differ in their eyes?

-Hagfish have rudimentary eyes (Not fully developed)

-Lamprey has well-developed eyes

How do lamprey and hagfish differ in their lateral-line system?

-Hagfish doesn’t have a lateral-line system

-Lamprey has a well-developed lateral-line system

How do lamprey and hagfish differ in their semicircular canals?

-Hagfish has 1 on each side

-Lamprey has 2 on each side

How do lamprey and hagfish differ in their barbels?

-Hagfish has 3 pairs of barbels

-Lamprey doesn’t have any barbels

How do lamprey and hagfish differ in their external gill openings?

-Hagfish has 1-14 on each side

-Lamprey has 7 on each side

How do lamprey and hagfish differ in their cranium?

-Hagfish has a poorly developed cranium

-Lamprey has a cartilaginous cranium

How do lamprey and hagfish differ in their branchial skeleton?

-Hagfish has a rudimentary branchial skeleton (not fully developed)

-Lamprey has a well-developed branchial skeleton

How do lamprey and hagfish differ in their vertebrae?

-Hagfish doesn’t have a vertebrae

-Lamprey has a present vertebrae

What kind of kidneys do hagfish have?

-Pronephric Kidney

What kind of kidneys do lamprey have?

-Opsithonephric kidney

Explain how hagfish reproduce?

-Little is known

-20-30 large yolky eggs with hooks to attach to seafloor

-Sex ratio skewed towards females

Explain how hagfish grow?

-Life history is unknown

-Young hagfish look like mini-adults

Explain how hagfish develop?

Explain how lamprey reproduce?

-Spawn in freshwater

-Eggs and sperms go directly into the body cavity and exit through abdominal pores

-Shallow gravel bottom streams

Explain how lamprey grow?

-Extended larval stage (ammocoetes)

-Marine or freshwater adulthood

-Dies after breeding

Explain how lamprey develop?