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 Air bladder anatomy

• 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% @ 1.091 20% @ 0.860 mean: 1.045 -Phsyclistic

1.025/1.045=0.98

-Physostomus Problems with air Bladders Bohr and Root Effects

• Pressure problems

– Boyles law – P1V1 = P2V2 Bohr effect – Root effect – – Slows speed at which you can change depths

• Accessibility to atmosphere

• Increase size of fish Other causes of shift: -Increased temperature -Salting out • Secondary losses

Rete Mirabile – counter current exchanger Physoclistic Air Bladder Physiology Physostome Air Bladder Physiology

Gasses in bladder at high Gasses in bladder at high pressure, exposure to capillary pressure, exposure to capillary Bladder lined with guanine bed will result in absorption bed will result in absorption crystals, impermeable to gas Atmosphere Vein Vein

Sphincter controls Artery Sphincter controls gas exposure to oval gas exposure to oval

Capillary bed Gas Gland Gas is pumped O2 CO2 release gland. gland. Rete regulated by into bladder metabolic activity in directly from Pneumatic gas gland atmosphere or Gas Gland duct

Blood Blood supply through gas gland

Passive secretion Regulated by exposure Active secretion to gland Stomach Requires energy

Other uses for air bladders Respiration Dorsal View • Light reflection\ • Respiratory Surface Water – Gills – Stomach • Sound production – Lungs – Cutaneous • Body • Sound reception • Buccal cavity • Moving water – Buccal pump – Ram ventilators Gill anatomy Gill anatomy Filament Arch Rakers • Arch • Rakers • Filament • Primary Lamellae

• Secondary lamellae Secondary lamellae

Primary lamellae

Gill Surface area to body weight Cutaneous Respiration • In water: • Problems with too much – aerial uptake (lungs) 40% surface area – skin 30% – gills 30% • In air: • Problems with too little surface area – lungs 63% – skin 37% – gills (opercula closed) 0%

1000 00

Polypteriformes Air breathing fishes Air breathing anatomy

• 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

Obligate vs. facultative air breathers Gill Raker Function • Obligate vs. Facultative air breather • Environmental adaptations to • Raker spacing and size indicate feeding – low oxygen conditions mode – Predator refugia (swamps or deep water) • Large, widely spaced rakers

15 14-15 14 13-14 High BOD in 12-13 13 some habitats 11-12 12 10-11 adds to 9-10 11 • Small, fine rakers problems… 8-9 10 7-8 6-7 9 5-6 4-5 8

Dissolved Oxygen (mg/L) Oxygen Dissolved 7 6 5 4 0 5 10 15 Temperature (C) 20 t) 36000 p 25 p ( y 27000 it 30 n li a 35 18000 S 0 9000 Skulls and Jaws

• External representations of major bones.