Lec 6/7 Part c

Question 1

Cyclostomata

Answer 1

Jawless fish

Question 2

Petromyzontiforms

Answer 2

‘Stone sucker’

Slender scaleless up to 1m long

Anguilliform swimmer

Several species in Canadian waters

Question 3

Sea lamprey

Answer 3

An invasive pest in the Great Lakes

Question 4

Petromyzontiforms species

Answer 4

40 extant species in two genera: Petromyzon and Lampetra

Question 5

Petromyzontiformes inhabit

Answer 5

Temperate fresh or salt waters, mostly northern hemisphere

Question 6

Petromyzontiformes diagnostic features

Answer 6

Absence of paired fins

Seven pairs of gill pouches

Single median nostril (lead into blind olfactory pouch)

Adenohypophysis and pineal eye

Well developed eye

Presence of a velum in the pharynx

Keratinized “teeth” on the tongue

Piston cartilage to support the tongue

Question 7

Petromyzontiformes feeding behaviors of larvae

Answer 7

Ammocoetes are amphioxus-like filter feeders

Question 8

Petromyzontiformes adult feeding behavior

Answer 8

Have a non-feeding adult stage

About half of all species are parasitic drinking blood of other fish

Question 9

Petromyzontiformes respiration

Answer 9

Flow through ventilation

Tidal style ventilation in adults during parasitic feeding or when mouth attached to stones

Question 10

Flow through ventilation

Answer 10

Water drawn into mouth and pumped out through seven gill openings

Question 11

Tidal style ventilation

Answer 11

Water drawn in and out through seven gill openings

Question 12

Osmoregulation

Answer 12

Gill and kidney regulate concentrations of ions, water, nitrogenous wastes, and overall balance of the body fluid, as in jawed fishes

Question 13

Petromyzontiformes reproductive migration

Answer 13

Anadromy- Adults live in oceans then migrate to freshwater rivers to breed

Question 13

Petromyzontiformes fossil lampreys earliest record comes from

Answer 13

The Late Devonian

Question 13

Myxiniformes

Answer 13

Slender, scaleless, pink in color

0.5 M long

Anguilliform swimmer

Difficult to breed in captivity

Many aspects are yet to explore

Question 13

Huge gap of fossil lampreys record until

Answer 13

The Early Cretaceous

Question 14

Growth series found for fossil lamprey known as

Answer 14

Proscomyzon

Question 14

Myxiniformes species

Answer 14

75 extant species in two genera- Eptatretus and myxine

Number of gill pouch varies between species, up to 15

All known species are deep ocean dwellers, mostly near the sea floor

Found worldwide except in polar regions

Question 15

Myxiniformes diagnostic features

Answer 15

Absence of paired fin

Absence of image forming eye

Single median nostril connected to pharynx

Three pairs of barbels as chemosensory organs

Presence of a velum in the pharynx

Tongue with keratinized “teeth”

90-200 pores for slime glands along both sides of the body

Question 16

Myxiniformes: Slime

Answer 16

3-4 % of the hagfish’s body mass

Long proteinaceous threads that uncoil to form a network of intertangled protein strings. Water slowly passes through the string network

Can be released actively and passively

Primarily if not exclusively used for defense

Question 17

Myxiniformes feeding behavior

Answer 17

Rely exclusively on olfactory cues

Scavenger and predator

Question 18

Myxiniformes- Knotting

Answer 18

Hagfishes twist themselves into knots for

Predation: Increased pulling force when tearing fresh from carcasses/prey

Escape when seized by predators

Clean themselves of their own slimes

Question 19

Myxiniformes reproduction

Answer 19

Female to male ratio is ~100-1

Some species are hermaphroditic

Eggs are anchored to seafloor by hooks

Absence of a larval stage

Question 20

Hermaphroditic

Answer 20

Same individual carries gonads of both sexes

Question 21

Myxiniformes respiration

Answer 21

Flow-through ventilation

Mouth may contribute to ventilation during swimming

Question 22

Flow-through ventilation

Answer 22

Water is drawn into nostril and pumped out through seven gill openings

Question 23

Myxiniformes
Osmoregulation

Answer 23

Low metabolic rate contributing to feeding in a hypoxic condition during scavenging

Isosmotic

Organs such as kidney still regulate ionic balance

Slime glands may help with controlling ionic balance

Question 24

Isosmotic

Answer 24

Body fluids having the same osmotic pressure as seawater

Question 25

Myxiniformes- fossil hagfish earliest record

Answer 25

Later Carboniferous

Question 26

Myxiniformes- fossil hagfish huge gap in fossil record until

Answer 26

Cretaceous

Question 27

Shared diagnostic features of petromyzontiforms and myxiniforms

Answer 27

A single median nostril

Gill arches lack joint

Presence of velum in the pharynx

A tongue with keratinized teeth

Two semi-circular canals in the inner ear

Question 28

Phylogenetic hypotheses of similarities petromyzontiforms and myxiniforms

Craniate theory

Answer 28

Hagfish as an outgroup

Absence of true vertebrae in hagfish

Development of neural crest differ in hagfish

Question 29

Phylogenetic hypotheses of similarities petromyzontiforms and myxiniforms

Cyclostome theory

Answer 29

Hagfish and lamprey as a monophyletic group

Poorly developed, irregular vertebrae lamprey

Presence of keratinized teeth on tongues

Question 29

Fossil jawless fishes (agathans)

Answer 29

Present as early as Cambrian

All went extinct

Phylogenetically between cyclostomes and jawed vertebrates

Question 30

Fossil agnathans: Conodontia

Answer 30

Widespread, found mostly in the form of tooth-like microfossils

Cambrian to Triassic

Composed of hydroxyapatite, the same mineral constituting vertebrate bones and teeth

Elements of conodont can form in a somewhat “symmetrical apparatus”