Fish

Question 1

Three main groups of fish

Answer 1

Class
Agnatha - Jawless fish
Chondrichthyes: cartilaginous fishes
Osteichthyes: bony fishes

Question 2

Agnatha: jawless fishes (5)

Answer 2

Oldest and most primitive class of vertebrates
Lack jaws and pelvic fins
Many lack pectoral fins
Order Cyclostomata
Lampreys and hagfishes

Question 3

Class Chondrichthyes (5)

Answer 3

Skeleton entirely cartilaginous
Placoid scales
Approximately 700 species of sharks, rays & related fishes Lack lungs and a swim bladder
Males have a clasper on the pelvic fin
Transfers sperm to female – fertilisation internal

Question 4

Class Osteichthyes (7) and the two sub classes

Answer 4

Skeleton contains a significant amount of bone
Various types of bony scales
Most species possess lungs or a swim bladder
Most species oviparous & fertilisation is external
Terrestrial vertebrates evolved from early members of this group (Crossopterygii) Subclass Actinopterygii: ray-finned fishes
e.g. trout
Subclass Sarcopterygii: fleshy-finned fishes
e.g. lungfishes

Question 5

Explain the considerations with fish body shape

Answer 5

pressure drag reduced by long and slender

Frictional frag is lowest by short and plump body

Therefore compromise between the two to be fastest

Question 6

Fish Skin (5)

Answer 6

besides agnathans there are armoured with scales of dermal origin

non-keratinised stratified squamous epithelium

Club cells produce mucous (covering fish for protection (physical or infection + clean + reduce drag)

Poison glands present in some

can have damage without bleeding

Question 7

Fish colour

Answer 7

colouring primarily = dermal pigments

Chromatophores

Question 8

The four Chromatophores

Answer 8

Melanophores- Black
Xanthophores - yellow
Erythrophores - Red
Iridophores - silver/iridescent

Question 9

Scales base 4 layers

Answer 9

base = 4 layers
1. enamel
2. dentine
3. vascular bone
4. lamellar bone

Question 10

placoid (plate) scales

Answer 10

Chondrichthyans
lack vascular and lamellar bone
scales have a pulp cavity

surface denticles projecting scales

development - placoid develops in dermis then it projects out when developed

teeth bones and spines are modification of placoid in these species

Question 11

bony fishes mostly have what type of scales

Answer 11

Teleost scales (which are then clarified as cycloid or ctenoid)

Question 12

Explain Teleost scales (3)

Answer 12

lack enamel, dentine and vascular bone = leaving only lamellar bone ( does not penetrate epidermis
concentric rings (circuli) these increase with age

Question 13

Explain the difference between cycloid or ctenoid scales

Answer 13

both made of concentric rings
ctenoid have series of projections on posterior margins

Question 14

Fish skull

Answer 14

two parts Neurocranium (top skull) and Branchiocranium (bottom and gills/operculum)

Question 15

fish axial skeleton, the two parts and their differences,

Answer 15

divided into two parts tank and caudal.
each vertebra = biconcave centrum develops around embryonic notochord.
Dorsal to each centrum is a neural arch where the spinal cord resides

Caudal vertebra have have haemal arch ventrally (protect major blood vessesls

Question 16

Explain the attachment of the pectoral fins

Answer 16

They are attached to the pectoral girdle which are then attached to the skull

Question 17

List how to divide the two types of fin

Answer 17

median and paired

Question 18

Which fins on the fish are median

Answer 18

find that are on the median axis: dorsal, caudal and anal fins

Question 19

Which fins are paired on a fish

Answer 19

Pectoral and pelvic fins

Question 20

what are fin rays and what are the two types

Answer 20

these support the fins, there are

spines which are hard part of the cranial dorsal fin

Soft rays - bilateral structure, generally show some segmentation and branching

Question 21

internal skeletal support of the dorsal and anal fins

Answer 21

Question 22

Pterygiophores

Answer 22

Supports the Doral fins

Pterygiophores consist of three basal bones and several radial bones, which lie in the median septum between adjacent vertebral spines and articulate with the fin rays.

Question 23

urostyle

Answer 23

The caudal fin is supported by a terminal urostyle, which is formed by the fusion of several caudal vertebrae.

Question 24

myosepta and myomeres

Answer 24

Starting from behind the head, the fish muscles are W shaped, myosepta divide them, myomere are the segments.

Question 25

Explain the vertical division of muscles

Answer 25

Epaxial and hypaxial with a septum that divides the two

Question 26

Fish locomotion

Answer 26

alternative myomere contractions plus the vertebral column presentating contractions result in lateral undulations
Head as a fulcrum for the tail

Question 27

different fins for locomotion

Answer 27

caudal = propulsion
other fins for stability

Question 28

basic fish digestive system

Answer 28

mouths suction
ciliated oesophagus
intestine

Question 29

fish Oropharangeal Cavity

Answer 29

Teeth are thought to have evolved from the bony armour of primitive fishes. In sharks, teeth have clearly arisen from placoid scales.
In bony fish, teeth may be found on;
(a) the jaw margins.
(b) roof of the mouth. (c) tongue.
(d) pharynx (gill arches)
Fish are primarily homodont (all teeth the same)

Question 30

Alimentary Canal

Answer 30

very distensible oesophagus (big meals at once)

stomach of predatory fish is elongate while omnivorous species is sac shaped

Question 31

stomach of fish

Answer 31

predatory fish - HCL and pepsinogen

puffer fish stomach fills with air or water

Question 32

Intestine of fish

Answer 32

varies with diet
carnivores short
herbivores elongated with many folds

sharks = elaborate spiral fold known as spiral valve = slow passage of food + increase SA

have rugae and villi digestive glands and mucous

Question 33

pyloric caecae fish

Answer 33

In most species of bony fishes, pyloric caecae are present at the junction of the stomach and the duodenum. These can vary in number from one caecum to approximately 200 caecae in some species, and serve as additional areas for digestion and absorption.

Question 34

Liver in fish

Answer 34

Bile salts with gallbladder before being discharged into the intestine.

Question 35

Pancreas

Answer 35

endocrine and exocrine both present in lampreys and hagfishes the pancreas exocrine is dispersed across the liver and throughout the submucosal layer of the intestine. While the endocrine part is clumps of cells adjacent to bile duct.

In sharks and some species of bony fish, the pancreas is a single structure with clearly defined endocrine and exocrine components, while in other species of bony fish it is a diffuse structure scattered throughout the omentum and liver, and so is termed an hepatopancreas.

Question 36

Fish circulatory system

Answer 36

single circulatory system one circuit –> arteries to gills, then to rest of the body.

Question 37

Chondrichthyans and bony fish hearts

Answer 37

4 chambers, sinus venous, atrium , ventricle and bulbus arteriosus (conus arteriosus)

Question 38

Explain the flow of blood

Answer 38

returning blood –> thin-walled sinus venous –> opens medially–> atrium(auricle)- ( fairly thin walled with some muscle fibres) –> Atrioventricular opening (sphincter and semi values)–> ventricle (thick muscle) –> bulbus ateriosus (elastic)

Note that while the sinus venosus, atrium and ventricle consist of cardiac muscle, the bulbus arteriosus is composed of smooth muscle.

Question 39

blood flow parts the aortic arches

Answer 39

–> afferent branchial arteries –> gill arch–> efferent branchial –> carotid artery–> head–> branches segmentally off dorsal aorta to the rest of body

Question 40

xTail blood supply

Answer 40

dorsal aorta –> caudal aorta ( in heemal arches)–> caudal vein just below the dorsal aorta –> renal portal system –> kidney –> posterior cardinal vein –> anterior cardinal vein above the heart

Question 41

lung fish

Answer 41

partially divided by interatrial septum (left and right atrial chambers)

bulbus arteriosus has a spiral valve to keep oxygenated and deoxygenated blood separate

when they leave the bulbus arteriosus some go to gills while others do not

Question 42

parts of the Gills and Respiration

Answer 42

branchial bars are the support
gill filaments are attached on branchial bars
lamellae (primary and secondary) attach onto gill filaments.

lamellae are covered in thin epithelium and vast network of capillaries.

gill rakers strain the water before passing through gills to prevent damage ( some modify this for food harvesting)

Question 43

Shark and ray gills

Answer 43

divided into individual chambers by inter brachial septa

Question 44

bony fish gills

Answer 44

Septa of sharks is reduced to all gills lying in a common chamber called the operculum

operculum allows the dual pump system –> both negative and positive predation to draw water from the buccal then forced across the gills.

The mouth is opened and water flows into the buccal and gill chambers, forcing the buccal chamber to expand (Figure 14). The mouth then closes, the pharyngeal floor is raised and the buccal chamber contracts, opening the opercular valve and forcing water out. In sharks, gill flap valves (gill septa) replace the role of the operculum seen in bony fishes

Question 45

Ram ventilation

Answer 45

shark and other fast swimmers open their mouths

Many sharks do not have well-developed respiratory movements and can only take in sufficient water when swimming using ram ventilation - they suffocate when immobilised.

Question 46

Counter current

Answer 46

Water high in oxygen is taken into the buccal chamber and driven across the gill filaments which contain capillaries carrying deoxygenated blood in the opposite direction to that of the entering water. Because the water and blood are flowing in opposite directions, gas exchange is optimised with some fish able to extract as much as 85% of the oxygen from the water (Figure 15).

Question 47

Air breathing fish

Answer 47

and have a highly folded and well vascularised inner wall of the operculum and gill chamber which enables them to extract oxygen from the air

Question 48

Lung fish adaptation

Answer 48

lungs developed from gas bladder, however not sure if this evolutions I homologous with other species lungs

In the Australian lungfish (Neoceratodus forteri), there is a single lung (the other species have paired lungs) which is connected to the oesophagus via a trachea. Thus, swallowed air passes from the oesophagus to the lung which is divided into many small compartments (faveoli) that are highly vascularised for gas exchange.

Question 49

Gas Bladder list the four fx

Answer 49

characteristic of boney fish, has variety of fx among fish

Respiration
sound conduction
sound production
Hydrostatic control

Question 50

Gas bladder respiration

Answer 50

In fishes where the gas bladder is joined to the alimentary canal (physostomous gas bladder), it is used as a supplementary organ of respiration. Air is swallowed and passed to the gas bladder, via the pneumatic duct, where oxygen is absorbed into the blood – this is a similar situation to that seen in the lungfishes except that these air-breathing fishes utilise a gas bladder for gas exchange rather than lungs.

Question 51

Gas bladder Sound Conduction

Answer 51

The gas bladder may also act as a sound conductor, or resonator. In some fishes, extensions of the gas bladder make direct contact with the inner ear, while in others a series of small bones (Weberian ossicles) connect the gas bladder to the inner ear. Because the gas bladder is filled with gas (!) it can also act as a resonator to enhance sound detection.

Question 52

Sound Production

Answer 52

The gas bladder may be used to generate sound by abruptly releasing air from the bladder (akin to burping!), grinding teeth, or strumming the bladder via specialised muscles which originate from the dorsal body wall and insert onto the bladder making its walls vibrate. Sounds play an important role in breeding behaviour, the defence of territories, and as warning sounds.

Question 53

Hydrostatic control with gas bladder

Answer 53

One of the most universally important functions of the gas bladder amongst the bony fishes is as a hydrostatic organ, regulating buoyancy. In fish in which the gas bladder serves primarily as a hydrostatic organ, rather than a respiratory organ, it is known as a swim bladder. Fishes which have a physostomous gas bladder (see above) regulate air volume in the bladder by gulping or releasing air via the pneumatic duct (Figure 16).

Question 54

Hydrostatic control with gas bladder

Answer 54

One of the most universally important functions of the gas bladder amongst the bony fishes is as a hydrostatic organ, regulating buoyancy. In fish in which the gas bladder serves primarily as a hydrostatic organ, rather than a respiratory organ, it is known as a swim bladder. Fishes which have a physostomous gas bladder (see above) regulate air volume in the bladder by gulping or releasing air via the pneumatic duct (Figure 16).

Fishes in which the pneumatic duct has been lost (physoclistous swim bladder) adjust gas volume in the bladder entirely by exchanging gases with the blood. The transfer of gas into the bladder occurs at a highly vascularised portion of the bladder wall called the gas gland with its associated rete mirabile; gas is removed from the bladder at the oval, a pocket at one end of the swim bladder in which gas diffuses from the bladder into the surrounding capillaries (Figure 16).

Question 55

Excretion freshwater

Answer 55

ammonia

body fluids are hyper osmotic compared to surrounding water
- so there is an influx of water through the gills, oral membranes and intestine, and a loss of salts to the environment. This is countered by the kidneys which produce a large volume of very dilute urine to remove excess water from the body – freshwater fish excrete approximately 10x the volume of urine produced by marine fish. The kidneys have large, well-developed glomeruli to facilitate the production of dilute urine. The gills and oral surfaces also provide a site for the active absorption of salts.

Question 56

Marine fish excretion

Answer 56

owever, live in an environment in which they are hypo-osmotic and so they tend to lose water and gain salts, putting them at risk of dehydration. In this case the kidneys produce a very concentrated urine so as to maximise the excretion of excess salts and to minimise the loss of water. In contrast to the kidney of freshwater fishes, that of marine fishes lacks glomeruli and so produces very little fluid that would need to be resorbed via the renal tubules. The kidneys of marine fishes also lack a distal tubule – normally the distal tubule resorbs salt but also allows for water to be excreted, and so by losing the distal tubule the potential for water loss is eliminated. Thus, the urine of marine fishes is produced by the selective secretion of solutes into the renal tubules to produce a very concentrated urine.

Question 57

Shark excretion

Answer 57

solve their osmotic problems rather differently by retaining high levels of urea in the blood plasma (ureotelism) so that blood osmolarity approximates that of sea water; hence, large losses of water to the environment do not occur. Excess salts are eliminated via a special gland called the rectal gland which passes salts into the faeces.

Question 58

Reproduction of fish

Answer 58

Testes are internal usually paired and elongate
lx above the swim bladder
Sperm leaving the testis may move down the meonephric (archinephric) ducts of the kidney or, in the higher bony fish, a true sperm duct may develop.

Ovaries- he ovaries are also internal, longitudinal and suspended from the dorsal body wall in a similar manner to the testes. Most bony fishes have paired ovaries, while cyclostomes have only one ovary. In many species of sharks, two ovaries initially develop but only one (usually the left) persists and is functional. The size of the ovaries varies considerably with the stage of sexual maturity. In most bony fishes, the eggs pass from the ovary directly into an oviduct. However, in trout, salmon and spotted barramundi, the eggs rupture directly into the body cavity and pass to the exterior through pores in the body wall near the anus.

Question 59

Fish feertilisation

Answer 59

usually external
Fertilisation is usually external, in which case there are behavioural mechanisms to bring the two sexes into close proximity. However, in some species, fertilisation is internal and is associated with the development of special intromittant organs. In male sharks, the
~ 20 ~
pelvic fins are specialised to form claspers which are inserted into the female‟s cloaca. During copulation, sperm exits the male cloaca and enters a groove in the clasper where it is then flushed into the female cloaca via water squirted from siphon sacs in the male‟s body wall. Male top-minnows have elongated rays in their anal fin which forms a gonopodium. During mating the gonopodium transfers a package of sperm (spermatophore) to the cloaca of the female to facilitate internal fertilisation.

Once the eggs are laid, there may be some incubation behaviour by the adults or the eggs may be left attached to vegetation or floating in the water. The spotted barramundi incubates the eggs in its buccal cavity until they hatch. The male kurtus, a north Australian fish, broods the eggs on his forehead until hatching. Fish which bear live young may mature the eggs in the oviduct (e.g. sharks) or while still in the ovary (species of bony fish).

Question 60

Fish nervous system

Answer 60

The fish brain is an enlargement of the anterior end of the spinal cord. The olfactory (cerebral) lobes, optic lobes and cerebellum are particularly prominent. The sense of smell is quite important to fish. Scents are detected through the olfactory epithelium of the nasal sac, below the external nares, which has nerves running directly to the olfactory bulbs of the brain.

Question 61

lateral line

Answer 61

The lateral line system is present in many fish species. It consists of long grooves, called lateral line canals, in the skin particularly in the region of the head and extending along the sides of the body and tail. Within the lateral line canals are sensory organs called neuromasts, which are associated with afferent nerve pathways. Neuromasts consist of an area of sensory tissue made up of receptor cells (hair cells) which send hair-like extensions into a gelatinous cupula. Neuromasts communicate with the environment through pores in the epidermis. The main function of the lateral line system is to provide information about the direction of travel and of localised disturbances in the water caused by small currents or vibrations. Cave-dwelling or deep sea fishes that lack vision are able to accurately navigate around obstacles via information relayed through the lateral line system. In surface-feeding fish the lateral line system detects the oscillations of insects on the water‟s surface. There is also some evidence to suggest that the lateral line system can detect low frequency sounds; however, this is still controversial.