Physiology

Goliath Groupers

Goliath grouper, or Epinephelus itajara, are the subject of strong opinions and divided emotions. Divers love to see these mammoth fish; underwater hunters denounce them as competitors, or covet them as outsized trophies; fishermen are just itching for a policy change that allows harvest; and regulatory bodies seem constantly poised to rescind long-term protection in favor of short-term exploitation.

Beneath the White Sea

We gathered in the frigid pre-dawn hours, our gear and luggage piled in front of the snowmobiles and our noses freezing in the -30ºC (-22ºF) temperatures. It was time to be saying good bye to our Russian hosts after a week of diving the frozen White Sea but we were tempted to linger just a little bit longer.

Thermal stress

A rapid chilling of superficial skeletal muscles (conductive cooling) creates a crippling weakening.

Thermal issues affect the comfort, performance and decompression stress experienced by divers. The impact varies with the timing, direction and magnitude of the thermal stress. Thermal protection can be provided by a variety of passive and active systems. Active systems should be used with particular care since they can markedly alter inert gas exchange and decompression risk.

California Sea Lion (Zalophus californianus) seen in Santa Cruz, California

How seals avoid the bends

Documentation of lung collapse and estimation of the depth at which collapse occurs has been difficult and only obtained in a few species.

Researchers led by Birgitte McDonald at the Scripps Institution of Oceanography netted a female adult California sea lion (Zalophus californianus), anaesthetised the animal and fitted it with loggers to record oxygen pressure in its main artery and the time and depths to which it dived.

Dusky dolphin

Dolphins have the unique ability to turn off and on diabetes

Scientists found that the mammal can induce the condition when there is little food around and turn it off when food is abundant.

Scientists from the US National Marine Mammal Foundation said that bottlenose dolphins are resistant to insulin - just like people with diabetes only in dolphins, this resistance is switched on and off.

They believe it is a unique ability in the animal kingdom and results from the mammal’s need to maintain high blood sugar levels to feed its big brain.