AMPHIOXUS

Question 1

All chordates have at some time during their life a _____________, _____________< and __________________.

Answer 1

notochord, dorsal nerve cord, and gill slits

Question 2

4 Subphyla of Phylum Chordata

Answer 2

Hemichordates (acorn worms)
Urochordata (tunicates)
Cephalochordates (amphioxus)
Vertebrata

Question 3

2 genera of Cephalochordates

Answer 3

Branchiostoma
Asymmetron

Question 4

it means sharp at both ends

Answer 4

Amphioxus

Question 5

genus of Amphioxus

Answer 5

Branchiostoma

Question 5

it is transparent and has an elongated but laterally compressed body

Answer 5

Amphioxus

Question 6

What do amphioxus lacks?

Answer 6

paired appendages; skull; vertebrae; kidney; heart; brain

Question 7

What makes amphioxus differ from fishes?

Answer 7

it lacks skull, vertebrae, brain, heart and kidneys

Question 8

Why is the body of amphioxus semitransparent?

Answer 8

single cell epithelium and gelatinous connective tissue

Question 9

angularly shaped muscle masses

Answer 9

myomeres

Question 10

feeding position of amphioxus

Answer 10

burrowing into the sand with its head exposed

Question 11

how do amphioxus obtains its food?

Answer 11

getting food from the seawater that flows over its head at regular intervals

Question 12

water-filtering mechanism of Amphioxus

Answer 12

Wheel Organ

Question 13

extends the entire length of the body

Answer 13

Median dorsal fin

Question 14

An expanded continuation of the median dorsal fin at the posterior end of the body

Answer 14

Caudal fin

Question 15

An anterior continuation of the caudal fin extending to the atriopore.

Answer 15

Ventral fin

Question 16

Opening of an internal cavity, the atrium, located just in front of the ventral fin.

Answer 16

Atriopore

Question 17

snout-like anterior end of the body that projects over the oral hood

Answer 17

Rostrum

Question 18

Twenty-two stiff tentacle-like structures projecting from the free edge of the oral hood. used for taste

Answer 18

Buccal cirri

Question 19

sixty angularly shaped muscle segments, also known as myotomes

Answer 19

Myomeres

Question 20

connective tissue partitions separating the myomeres

Answer 20

Myosepta

Question 21

row of rectangular bulging masses located beneath the ventral ends of the myomeres

Answer 21

Gonads

Question 22

A pair of integumentary folds that extend along the ventrolateral surfaces from the anterior pharyngeal region almost to the atriopore.

Answer 22

Metapleural folds

Question 23

Funnel-shaped membrane located at the ventral part of the anterior end of the body. Helps direct the water vortex, created by the wheel organ

Answer 23

Oral hood

Question 24

Funnel-shaped cavity enclosed by the oral hood

Answer 24

Vestibule

Question 25

Internal connective tissue rods that are present as supporting elements in both the dorsal and ventral fins; absent in caudal fin

Answer 25

Fin rays

Question 26

supporting rod that extends almost the entire length of the body

Answer 26

Notochord

Question 27

elongated cylindrical mass of nervous tissue that lies above the notochord

Answer 27

nerve cord

Question 28

linear series of pigment cells lying along the ventral wall of the nerve cord; serve as photoreceptors

Answer 28

Ocelli

Question 29

A mass of pigment cells located at the anterior end of the nerve cord.

Answer 29

Eye spot

Question 30

A series of finger-like projections, lined with cilia, that lies on the inner lateral and dorsal walls of the oral hood.

Answer 30

Wheel Organ

Question 31

vertical membrane located just behind the base of the wheel organ; regulate the amount of water entering the pharynx

Answer 31

Velum

Question 32

opening in the velum

Answer 32

Mouth

Question 33

short tender projections extending from the margin of the velum that rings the mouth; prevent sand particles from passing into it

Answer 33

velar tentacles

Question 34

the chamber, interrupted by gill slits, that extends from the mouth to the intestine

Answer 34

pharynx

Question 35

slender parallel oblique bars, supported by branchial rods, that make up the side wall of the pahrynx

Answer 35

Gill bars

Question 36

Large cavity surrounding the pharynx; its ventral boundary is visible as a line extending below the pharynx to the atriopore.

Answer 36

Atrium

Question 37

digestive tube that extends from the pharynx to the anus

Answer 37

Intestine

Question 38

pouch that projects forward as an outpocketing of the intestine

Answer 38

Hepatic diverticulum

Question 39

outer cellular layer of the body; composed of single layer columnar cells; covered by an acellular cuticle

Answer 39

Epidermis

Question 40

short projection from the dorsal midline region that is supported by the gelatinous fin rays

Answer 40

Dorsal fin

Question 41

masses of muscle under the skin, separated by connective tissue partitions, the myosepta

Answer 41

Myomeres

Question 42

triangular structure located in the midline, slightly ventral to the dorsal fin

Answer 42

Nerve cord

Question 43

very narrow cavity of the nerve cord

Answer 43

Neurocoel

Question 44

central cavity of the oral hood

Answer 44

Vestibule

Question 45

The thickened ciliated epithelial masses of the __________ are found on the inner oral hood wall.

Answer 45

Wheel Organ

Question 46

These project down from the ventrolateral corners of the body.

Answer 46

Metapleural folds

Question 47

lies in the wrinkled body wall between the metapleural folds; when it contracts, it compresses the atrial cavity dorsal to it from the side, thus expelling its water

Answer 47

transverse muscle

Question 48

narrow cavity limited laterally by gill bars extend between the notochord and transverse muscle

Answer 48

pharynx

Question 49

2 types of gill bars

Answer 49

Primary and Secondary Gill Bars

Question 50

Smaller gill bars and do not contain a coelomic cavity near their lateral end

Answer 50

Secondary or tongue bars

Question 51

the gill bars are separated by small bridges called

Answer 51

synapticulae

Question 52

deeply grooved structure in the floor of the pharynx

Answer 52

endostyle

Question 53

thyroid gland in amphioxus

Answer 53

endostyle

Question 54

located on the roof of the pharynx

Answer 54

epipharyngeal groove

Question 55

they protrude into the atrium from the body wall, still bounded by the atrial lining.

Answer 55

Gonads

Question 56

large, nucleated cells

Answer 56

Ovary

Question 57

smaller germ cells, which appear as a mass of small dark dots

Answer 57

Testis

Question 58

hollow oval-shaped structure seen on the right side of the pharynx

Answer 58

Hepatic diverticulum

Question 59

Present in the cross-section as three sacs

Answer 59

Coelom

Question 60

located on both sides of the epipharyngeal groove

Answer 60

Coelomic cavities

Question 61

paired dorsal aortae may be seen between the notochord and the dorsal end of each of the paired coelomic cavities

Answer 61

Blood vessels

Question 62

enclosed within the ventral coelomic cavity

Answer 62

Ventral aorta

Question 63

present close to the midpoint of the medical borders of the gonads

Answer 63

Cardinal Veins

Question 64

large hollow oval structure lying ventral to the unpaired dorsal aorta

Answer 64

Intestine

Question 65

Beneath the intestine

Answer 65

Subintestinal Vein

Question 66

seen at levels posterior to the atriopore; at levels anterior to the atriopore, metapleural folds will be seen in its place

Answer 66

Central fin

Question 67

rather than dorsal or ventral fins, it is present. It is narrower and higher than either.

Answer 67

Caudal fin