"Walnut-Size" Male Octopus Seen Alive for First Time

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The male octopus, which approached them from the depths, weighed in at no more than a quarter of a gram (0.08 ounce) and was only 2.4 centimeters (0.9 inch) long. Norman, an octopus identification expert, knew he'd found something unusual because he didn't immediately recognize the species, said Tregenza.

Later comparison with museum specimens revealed the unusual nature of the find.

A female specimen also examined in the Museum Victoria was 80 centimeters (2.6 feet) long and weighed in at nearly three kilograms (8 pounds), or more than 10,000 times heavier than the tiny male.

The largest females of the species are almost twice as long and are likely to weigh as much as 10 kilograms (27 pounds), almost 40,000 times as heavy.

Lucky Break

Some of the most extreme examples of size differences between the sexes come from marine and parasitic animals, where males find it difficult to locate females.

The male octopuses' chances of finding a mate "are in the hands of fate," said Tregenza. Greater size, therefore, doesn't offer males any significant advantage in tracking down a female mate. Instead of wasting time growing to maturity, the best strategy is to start searching for mates as early as possible, Tregenza said.

Contrary to males, however, female blanket octopuses may benefit from being large. "The amount and size of offspring produced is determined by the size and condition of the female," commented James B. Wood, an octopus biologist at the University of Texas Medical Branch in Galveston.

"Many generations of small males can be produced in the amount of time it would take to produce a larger male," said Wood. In essence, the males appear to be using a "live fast and die young" strategy, he said.

If a male does chance across a female, it uses all its resources in an attempt to mate, "as he's unlikely to encounter another one," said Tregenza. A male blanket octopus fills a modified tentacle with sperm, tears it off, presents it to its prospective mates, and then drifts off to certain death.

Females store the tentacles inside large internal body cavities until they are ready to lay their eggs. At that time, the female pulls the tentacle out and "squeez[es it] like a tube of toothpaste," over the eggs, said Tregenza.

The sole reason scientists know that the mismatched sexes are the same species, is because females have often been found with male tentacles inside them.

Finding a live male is an intriguing discovery, commented Wood, who added that the scientific community knows very little about the open-ocean, deep-sea animals.

"The continued search for an alive adult giant squid in its natural habitat illustrates this point well," said Wood. "If we haven't been able to observe a 60-foot [18-meter] squid in its natural habitat, think of how many smaller species are waiting to be discovered."

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