Swimbladder

Swimbladders can be used as drums in a number of ways (3):

1. beating the pectoral fins against the side of the body 2. beating the opercular apparatus against the body wall where it covers the swim bladder 3. use of sonic muscles

Swim bladder sound producing mechanisms generally fall into two categories:

1. indirectly the swim bladder acts as a resonator to change the quality of the sound emitted by some other organ 2. directly the swim bladder is used to produce underwater sounds either by pushing gas from the bladder out through the mouth or by contraction of either the muscular wall of the bladder itself or of specialized muscles that cause the bladder to resonate (drumming)

The hydrostatic function of the swim bladder depends on its ability to:

1. maintain a gas-filled space inside the body cavity of the fish 2. Vary the volume of gas in response to changing hydrostatic demands The ability of the swim bladder to concentrate gases some 500 times in the case of oxygen and 25 times in the case of nitrogen is a unique property of this organ.

A swim bladder serving as a hydrostatic organ provides neutral buoyancy, thus enabling the fish to save energy in two ways:

1. the fish is able to remain motionless in mid-water 2. A fish with neutral buoyancy requires much less power (less energy) to swim horizontally at a given speed than does a similar fish with negative or positive buoyancy

Living _____ fishes and ______ do not have a gas-filled organ in their trunk region.

Living jawless fishes (hagfishes and lampreys) and chondrichthyans (sharks and their allies)

Although homologous (of the same evolutionary origin), they perform different functions: ____ are used for respiration while ______ function primarily to provide buoyancy.

Lungs --> respiration Swimbladders --> buoyancy

The most significant anatomical differences between lungs and swim bladders is that lungs are ____ and arise from the ventral margin of the foregut, while swim bladders are ____ and emerge from the dorsal margin.

Lungs are paired Swim bladders are single

Evidence supports the notion that _____ evolved earlier than _____.

Lungs evolved earlier than swim bladders. Most evidence indicates a teleostome origin.

Although hydrostasis is the primary function of gas-filled organs in the vast majority of modern-day bony fishes, in some species gas bladders have retained or secondarily acquired a _______ function.

Respiratory function They use their gas bladders as a lung

_______ swim bladders are completely closed, separated from the gut through loss of the pneumatic duct. The volume of gas inside the bladder is increased and decreased entirely through secretion or resorption of gases from or to the blood.

Physoclistous swim bladders This type of swim bladder is found only in derived teleosts. Species that have this kind of swim bladder are called physoclists.

Belches are produced by gas expulsion from the swim bladder by way of the pneumatic duct. Obviously this ability is limited to _______ fishes.

Physostomous fishes

_______ swim bladders are connected to the foregut by a duct called the pneumatic duct. Inflation usually requires swallowing air at the surface and forcing it back into the bladder by way of the pneumatic duct. Deflation usually requires a release of air directly into the water by way of the mouth (belching).

Physostomous swim bladders Characteristic of sturgeons and primitive teleosts. Species that have this kind of swim bladder are called physostomes.

_______ sounds are produced by friction of teeth, fin spines, or various bones rubbing or grinding against each other or similar hard parts of the head or body.

Stridulatory sounds

Gasbladders likely evolved within an ancestor that gave rise to the ______.

Teleostomi

Both lungs and swim bladders arise developmentally from the same embryonic tissue, the _____.

The foregut

The ______ condition is more derived. The ______ condition is more primitive.

The physoclistous condition is derived. The physostomous condition is more primitive.

_____ is the most effective mechanism for long-range communication under water

hearing

The notion that swim bladders evolved independently in sturgeons and teleosts is based in part on anatomical differences: the swim bladder of sturgeons originates from the _____, while in primitive teleosts, the swim bladder develops from the _____.

stomach, esophagus