Lab 6. Early Vertebrates and the Gnathosome Fishes

Question 1

What class are Lampreys in?

Answer 1

Class Petromyzontida

Question 2

Class Petromyzontida jaws

Answer 2

Jawless

Question 3

Lampreys as larvae

Answer 3

Bottom-dwelling filter feeders

Question 4

Lampreys as adults

Answer 4

Parasites on other fish

Question 5

Lamprey skin

Answer 5

Thick with many glands
Glands:
- Secrete cuticle (protection)
- Secrete mucous (reduce friction when swimming)

Question 6

Lamprey rod-like support structure along dorsal midline

Answer 6

Notochord

Question 7

Lamprey teeth

Answer 7

Horny teeth - composed of keratin. Lining mouth (attach to prey) and on tongue (rasp away scales of prey)

Question 8

Lamprey: what pulls food/O2 into mouth

Answer 8

Buccal funnel

Question 9

Lamprey: what is the fleshy partition that keeps food and water required for gas exchange separate?

Answer 9

Velum

Question 10

Lamprey: what is photoreceptive, involved in circadian rhythms and thermoregulation?

Answer 10

Pineal eye

Question 11

3 Classes of superclass gnathostomata

Answer 11

1. Chondrichthyes
2. Actinopterygii
3. Sarcopterygii

Question 12

2 Subclasses of class chondrichthyes

Answer 12

1. Elasmobranchii (sharks, skates and rays)

2. Holocephali

Question 13

Common name of class chondrichthyes

Answer 13

Cartilginous fishes

Question 14

Common name of class actinopterygii

Answer 14

Ray-finned bony fishes

Question 15

Common name for class sarcopterygii

Answer 15

Lobe-finned bony fishes and tetrapods (lungfish)

Question 16

Type of tail and swim bladder for chondrichthyes

Answer 16

Heterocercal tail, lack swim bladder

Question 17

Type of tail and swim bladder for actinopterygii

Answer 17

Homocercal tail, contain swim bladder

Question 18

Fish integument mucous function

Answer 18

Reduces friction between fish and water while moving

Question 19

Chondrichthyes scales

Answer 19

Placoid scales (tooth-like structure containing pulp cavity surrounded by dentine and capped with enamel)

Question 20

Actinopterygii scales (in non-toleost)

Answer 20

Ganoid scales (lower bony layer topped by layer of enamel-like material called ganoine)
Interlock to form tough armour

Question 21

Actinopterygii scales (in toleost)

Answer 21

Cycloid and ctenoid
Thin layer of bone, light and flexible.
Cycloid: circular with smooth posterior margin
Ctenoid: spiny posterior margin - calcium based salts and collagen

Question 22

Adaptations enabling efficient movement through water (4)

Answer 22

1. Zig-zag pattern of muscle bundles
2. Caudal fin
3. Composition of skeleton
4. Streamlined body shape

Question 23

Why zig-zag pattern of muscle bundles?

Answer 23

Contraction of single bundle affects large region of body wall

Question 24

Heterocercal tail fin

Answer 24

Upper tail lobe larger than lower lobe

Question 25

Homocercal tail fin

Answer 25

Upper and lower lobes are equal

Question 26

Cartilage is important why

Answer 26

Only slightly heavier in water

Question 27

Bone in fish

Answer 27

Less dense than bone in terrestrial vertebrates

Question 28

Fusiform body shape

Answer 28

Fast swimming in ocean water

Question 29

Compressiform body shape

Answer 29

Quick speed for short distances

Question 30

Depressiform body shape

Answer 30

Swims like flying bird

Question 31

Filiform body shape

Answer 31

Slithers through water like a snake

Question 32

How did jaws develop

Answer 32

Probably from gill (branchial) arches. VERY important events in vertebrate evolution

Question 33

Countercurrent exchange

Answer 33

water moves across pharyngeal lamellae of gills in opposite direction of blood = efficient exchange

Question 34

Why do some fish keep their mouths open all the time and never stop swimming?

Answer 34

Most fish actively pump water taken in through mouth across gills. Some fish don’t do this: so they keep mouths open to maintain flow of water.

Question 35

Shark gills

Answer 35

Septal gills. Distal tips of interbranchial septa act as valves that can close external gill slits

Question 36

Bony fish gills

Answer 36

Aseptal gills. Covered by operculum extending from hyoid arch region of head laterally and caudally over gills. Large common opercular cavity for all gills. Primary gill lamellae extend freely into opercular gavity.

Question 37

Circulation (heart)

Answer 37

Blood goes through 1 time. 1 atrium and 1 ventricle. Also pumps with contraction of body muscles when swimming

Question 38

Freshwater fish

Answer 38

Hyperosmotic. Eliminate excess water. Cells in gills actively pump ions from surrounding water into blood. Highly dilute urine. Excrete ammonia

Question 39

Marine fish

Answer 39

Hypoosmotic. Drink water, transport ions out of gills, produce highly concentrated urine.

Question 40

Fish that can travel btween fresh and marine water

Answer 40

Diadromous

Question 41

Chondrichthyes (marine) fish

Answer 41

Convert ammonia to urea and retain urea in blood so blood is isoosmotic to water. High tolerance to urea. Excrete excess salts via special rectal gland.

Question 42

Lateral Line

Answer 42

Sense organ used to detect movement and vibration in surrounding water. Some are electroreceptors.

Question 43

Fish fertilization

Answer 43

Some external (actinopterygii) and some internal (chondrichthyes)

Question 44

Fish eggs

Answer 44

Sharks are sometimes viviparous but most are oviparous. Some are ovoviviparous