Lec 7 Jawless fishes

Question 1

Jawless Fish: Hagfish characteristics

Answer 1

represented today by seven genera and about 75 species all contained within a single family, the Myxinidae. restricted to marine habitats throughout the temperate and tropical zones of the world. scavengers that burrow into the flesh of dead, the mouth contains a rasping tongue-like structure, is surrounded by a series of short tentacles (a sucking disk is absent

Question 2

Jawless Fish: Lampreys characteristics

Answer 2

Petromyzontidae.
anadromous and freshwater. filter-feeders as young but ectoparasitic bloodsuckers as adults; the mouth consists of a circular adhesive disk and a rasping tongue-like structure by which the fish attaches to other fishes and sucks their blood

Question 3

SIMILARITIES BETWEEN HAGFISHES AND LAMPREYS

Answer 3

soft-bodied, eel-like animals that are similar to each other but differ from all other vertebrates in a number of ways, particularly in the structure of the mouth and gills

Question 4

Other similarities between lampreys and hagfish

Answer 4

They lack gill arches
Both have a single median nostril
lack paired fins
lack bone
characterized most strikingly by a thick armor of dermal plates, all remnants of bone have been lost—nothing in these fishes is ossified.
They have a cartilaginous internal skeleton

Question 5

Myxini

Answer 5

Hagfishes

Question 6

Cephaluspidomorph

Answer 6

Lampreys

Question 7

Chondrichthyes

Answer 7

Cartilaginous fishes

Question 8

Actinopterygii

Answer 8

Bony, ray finned fishes

Question 9

Sarcopterygii

Answer 9

Lobe finned fishes

Question 10

Hagfishes are characterized

Answer 10

1. A single semicircular canal 2. They lack vertebrae (even embryonic traces are absent) 3. They lack neuromast cells 4. They lack extrinsic eye muscles 5. They are incapable of nervous regulation of the heart 6. They are incapable of hyperosmoregulation (an inability to control salt and water balance to meet changing environmental conditions

Question 11

Lampreys, on the other hand, share the following features with all other vertebrates

Answer 11

1. Two or three semicircular canals 2. Well-developed neural and haemal arches (the beginnings of a vertebral column) 3. True neuromast organs distributed along a lateral line 4. Extrinsic eye muscles 5. Capable of providing nervous regulation of the heart 6. Capable of hyperosmoregulation

Question 12

cartilaginous fishes consist of three primary groups

Answer 12

Sharks, rays, chimeras

Question 13

Cartilaginous fishes share the characteristics

Answer 13

1. Cartilaginous skeleton (parts of the skeleton may become calcified)
2. Scales in the form of dermal denticles (with a unique threelayered structure consisting of an enamel-like substance called vitrodentine, an inner layer of dentine, and underlying basal tissue and pulp cavity
3. Gasbladder absent 4.Spiral valve in the intestine 5. Internal fertilization (males of all living taxa are equipped with claspers, although there are some well-preserved sharks from the Upper Devonian that lack claspers) 6.Osmoregulation by retention of urea.

Question 14

Rays characteristics

Answer 14

1. Pectoral fins are fused to the head over the gill openings
2. Attachment or articulation of the pectoral girdle to the vertebral column

rays include about 57% of all living elasmobranchs

Question 15

RAJIIFORMES: skates

Answer 15

The trunk or disc is formed by the broad connection between the head and the greatly expanded pectoral fins.
paired electric organs along the sides of the tail and by claw-like spines along the lateral extremes of the disc.
most widespread of the rays,
Skates are oviparous

Question 16

PRISTIFORMES: sawfishes

Answer 16

long toothed rostrum is used to dislodge small benthic invertebrates from the bottom and for immobilizing small schooling fishes. Their striking similarity to sawsharks is one of the best examples of convergent evolution among fishes.
Viviparous

Question 17

TORPEDINIFORMES: torpedo or electric rays

Answer 17

torpedo rays are primitive in a number of respects and very specialized in others.
distinguished by the presence of huge electric organs along the lateral margin of the disc, which are used both to stun prey and to defend against attack by predators.
Viviparous

Question 18

RHINOBATIFORMES: guitarfishes

Answer 18

guitarfishes are primitive in their body shape but specialized in their gill arches.
They range in body shape from shark-like, with relatively small pectoral fins, to truly ray-like forms, with widely expanded pectorals.
All are benthic and generally associated with muddy to sandy bottoms in all major tropical seas of the world,
viviparous

Question 19

DASYATIFORMES: stingrays

Answer 19

stingrays resemble the skates in body shape, except that the tail is more slender and generally whip-like.
possess one or more serrated spines near the base of the tail. viviparous

Question 20

MYLIOBATIFORMES: eagle, cownose, manta rays

Answer 20

highly specialized for active swimming
pectoral fins, firmly attached to the vertebral column by a ball and socket arrangement, resemble bird wings, and are moved through the water in a manner similar to birds flapping their wings
most species are rather wide ranging in tropical seas.
viviparous

Question 21

Chimeras class

Answer 21

Holocephalans,
: 1. They have large, permanent, slow-growing tooth plates, rather than the separate replaceable teeth of sharks
2. Their upper jaw (palatoquadrate) is fused to the cranium, not suspended from the cranium as in elasmobranchs

Question 22

Order CHIMAERIFORMES Family Callorhynchidae: plownose chimaeras

Answer 22

long flexible, hooklike process on the snout, and a shark-like heterocercal tail.

Question 23

Family Rhinochimaeridae: longnose chimaeras; Atlantic and Pacific oceans (3 genera, 8 species)

Answer 23

The longnose chimaeras are similar to the shortnose chimaeras in the structure of the tail,
snout is long and pointed.
Atlantic and Pacific oceans

Question 24

Family Chimaeridae: shortnose chimaeras or ratfishes

Answer 24

The snout short and rounded;
the tail is long, thin, and tapering;
a poison gland is associated with the dorsal-fin spine
found throughout the Atlantic and Pacific oceans