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Dive Dry with Dr. Bill

#692: Don't Take My Breath Away

I'm sure some of you remember my spellbinding cable TV show "Munching and Mating in the Macrocystis." None of you? Oh, my. Well for those too young to remember, it was all about the two most important functions of a species in our giant kelp (Macrocystis pyrifera) forests: munching and mating.

Munching is critical for the survival of the individual and mating (or at least reproduction) for the survival of the species. Wise individuals have pointed out that respiration or breathing is also pretty critical. Try holding your breath for longer than an hour some time. I've replied that creating a TV show about marine life that focused on breathing would probably be taken off the air after a single boring episode.

However, respiration is worthy of at least one column in my "Dive Dry" series, so here goes. You're all aware of human respiration. You see chests rise and fall every day (and I'm referring to the lungs with that... shame on you). Only the best yoga practitioners and meditators can slow their breathing down to the point it is nearly undetectable. But let's look at marine critters rather than Homo sapiens.

Marine mammals are extremely popular with the general public. I've had friends with dolphin and whale memorabilia cluttering their homes. Others adore furry seals and sea lions. As far as I'm concerned none of these are true marine animals. Like us, they breathe at the surface taking in air directly from the atmosphere and expelling nasty vapors before descending again.

No, as far as this biologist is concerned, real marine critters take their oxygen from the water! And if you've ever mistakenly taken a breath underwater, you probably realize that H2O is far denser than air. That makes it a far more difficult source of oxygen, but marine life has adapted many ways to solve that.

Single-celled protists and other less complex critters may absorb oxygen directly from the surrounding water. More complex animals require more elaborate systems to extract oxygen and distribute it throughout their bodies. Many use gills which are often very fine structures that allow water to pass directly over them and extract oxygen from it. Snails such as nudibranchs, crabs and fish are familiar examples.

Other critters develop pumping mechanisms to draw water into their body cavities to extract oxygen. Simple sponges often do this as do the far more advanced tunicates and salps. I've recently written about bivalve molluscs like clams, mussels and oysters that create currents using their paired siphons. I've often observed octopus "breathing" water through their incurrent (intake) siphons and expelling it through their excurrent (exhaust) siphons.

Many are aware that some species of sharks (as well as other fish) have to swim continuously to ensure water passes over their gills. Biologists refer to this as ram ventilation. Highly active fish like bonita and tuna also do this. Others are capable of what is known as buccal pumping. This involves using the cheek or buccal muscles to pump water into the mouth and pass it over the gills. Sharks such as horn, swell whitetip reef and nurse sharks are capable of this and can rest on the bottom. Bottom dwelling halibut and scorpionfish are examples of bony fish that use this method.

Yes, respiration is very important to the survival of the individual... and thus to the survival of the species itself. Despite this, I really wonder how many of you would sit still in your easy chair, munching your popcorn and drinking your favorite adult beverage to watch a half hour show of breathing? Any takers? Yet 30 minutes of fish porn and I have you glued to your seat. Oh, my... such priorities!

© 2016 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. You can also watch these episodes in iPod format on YouTube through my channel there (drbillbushing). Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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Shaggy external gills of nudibranch and breathing siphon of octopus; gill slits on horn shark
and kelp bass backflushing its gills (or very bored by this column?)

This document maintained by Dr. Bill Bushing.
Material and images © 2016 Star Thrower Educational Multimedia