Internal Anatomy Hydrostatic Equilibrium

• Tissues are fairly dense

• Freshwater 1.0, Sea water 1.025

• Fish components:

– Muscle: 1.05

– cartilage: 1.1

– bone/bony scales: 2.0

– Fats: 0.9

• Average fish – 1.06-1.09 meaning they sink

• Solutions

• Note – more bone = much more weight!

Shark Liver Oils

• Specific gravity of oils significantly less than water

– Specific gravity of 0.86

– Expensive - up to 20% of body mass

– Works at any depth

Ex: 10 kg fish: 80% @ 1.09120% @ 0.860 mean: 1.045

1.025/1.045=0.98

Air bladder anatomy

-Physostomus

-Phsyclistic

Problems with air Bladders

• Pressure problems

– Boyles law – P1V1 = P2V2

– Slows speed at which you can change depths

• Accessibility to atmosphere

• Increase size of fish

• Secondary losses

Bohr and Root Effects

Bohr effect –Root effect –

Other causes of shift:-Increased temperature-Salting out

Rete Mirabile – counter current exchanger

Physoclistic Air Bladder Physiology

Rete

Blo

od

su

pp

ly

Ga

s G

lan

d

O2 CO2 release regulated by metabolic activity in gas gland

Gasses in bladder at high pressure, exposure to capillary bed will result in absorption

Vein

Sphincter controls gas exposure to oval gland.

Active secretionRequires energy

Passive secretionRegulated by exposure to gland

Bladder lined with guanine crystals, impermeable to gas

Physostome Air Bladder Physiology

Atmosphere

Gas is pumped into bladder directly from atmosphere or through gas gland

Gasses in bladder at high pressure, exposure to capillary bed will result in absorption

Vein

Sphincter controls gas exposure to oval gland.

Pneumatic duct

Capillary bed

Artery

Stomach

Ga

s G

lan

d

Other uses for air bladders

• Light reflection\

• Sound production

• Sound reception

Respiration

• Respiratory Surface

– Gills

– Stomach

– Lungs

– Cutaneous

• Body

• Buccal cavity

• Moving water

– Buccal pump

– Ram ventilators

Dorsal View

Water

Gill anatomy

• Arch

• Rakers

• Filament

• Primary Lamellae

• Secondary lamellae

Primary lamellae

RakersArchFilament

Secondary lamellae

Gill anatomy

Gill Surface area to body weight

• Problems with too much surface area

• Problems with too little surface area

100000

Polypteriformes

Cutaneous Respiration

• In water:

– aerial uptake (lungs) 40%

– skin 30%

– gills 30%

• In air:

– lungs 63%

– skin 37%

– gills (opercula closed) 0%

Air breathing fishes

• Reduced gill surface area

• Most freshwater – primarily swamps

– low pH and oxygen

• Few marine

– Gobiidae

– Bleniidae

– Cottidae

• 374 species, 125 genera, 49 families, 17 orders

Air breathing anatomy

Obligate vs. facultative air breathers• Obligate vs. Facultative air breather

• Environmental adaptations to

– low oxygen conditions

– Predator refugia (swamps or deep water)

05

1015

2025

3035 0 9

000

18000

27000

36000

4

5

6

7

8

9

10

11

12

13

14

15

Dis

solv

ed

Oxy

ge

n (

mg

/L)

Temperature (C)

Salin

ity (p

pt)

14-15

13-14

12-13

11-12

10-11

9-10

8-9

7-8

6-7

5-6

4-5

High BOD in some habitats adds to problems…

Gill Raker Function

• Raker spacing and size indicate feeding mode

• Large, widely spaced rakers

• Small, fine rakers

Skulls and Jaws

• External representations of major bones.