Researchers elucidate why octopus mothers die themselves after mating

Octopus is intelligent and has a survival strategy to protect itself from foreign enemies while changing its body color and regenerating its limbs. However, octopus females are also known to stop eating after laying eggs and become debilitated, dying by the time the eggs hatch. A research team at the University of Chicago, the University of Washington, and the University of Illinois at Chicago has elucidated why female self-defense octopus dies after laying eggs.

Steroid hormones of the octopus self-destruct system: Current Biology

Changes in cholesterol production lead to tra | Eurek Alert!

According to the research team, the octopus's maternal behavior of 'debilitating after laying eggs' is caused by an organ called the 'optic gland,' which resembles the pituitary gland of mammals. The optic gland causes major changes in cholesterol metabolism, resulting in major changes in the steroid hormones produced.

In 1977, Brandeis University psychologist Jerome Wodensky removed the optic nerve gland from a Caribbean-spotted mother of Tsuchidako, abandoned egg protection and resumed feeding behavior for several more months. It was revealed that he would live long. From this, it was argued that the mother's octopus would die debilitatingly due to the effects of hormones secreted by the optic nerve glands, but it is unclear what the hormones are and how they work. bottom.

The lead author of this paper, Assistant Professor Jan Wang of Washington University Biology, was a graduate student with Professor Clifton Rag'sdale, who studies neurobiology at the University of Chicago, on the optic nerve gland of

Octopus bimaculoides (California two-spot octopus) . The sequence of the RNA transcriptome was decoded. Analyzing the RNA transcriptome sequence makes it possible to elucidate all of the gene transcripts in the optic nerve gland and to understand gene expression in cells. And when the octopus started fasting, it turned out that the activity of genes that metabolize cholesterol and produce steroids increased.

In this study, Assistant Professor Wang discovered three pathways involved in the increase in steroid hormones in the body of octopus after reproduction. One of them produces two pregnancy-related steroid hormones, progesterone and pregnenolone , the second is a pathway that produces intermediates of maternal hormones and bile acids , and the third is a cholesterol precursor. It produced some 7-dehydrocholesterol . It was found that the female octopus that laid eggs changed the optic nerve gland significantly and produced more progesterone, pregnenolone, 7-dehydrocholesterol, etc. than usual.

Smith-Remli-Opitz syndrome, one of the genetic diseases of humans, is a syndrome caused by a decrease in cholesterol production due to a mutation in the gene of an enzyme that reduces 7-dehydrocholesterol to cholesterol. One of the symptoms of this Smith-Remli-Opitz syndrome is 'repeating self-harm,' the research team said, reminiscent of the behavior of female octopuses that laid eggs.

In other animals, including humans, changes in cholesterol metabolism have a significant impact on longevity and behavior, so the research team found that inhibition of the cholesterol-producing process in females that laid eggs, as in other animals. It suggests that it may have a great influence on the behavior of octopus.

Assistant Professor Wang said, 'We knew that cholesterol was important both in terms of diet and in various signal transduction systems in the body. Cholesterol is involved in everything from the flexibility of cell membranes to the production of stress hormones. However, it was a big surprise to be involved in the life cycle process of octopus. '

in Science,   Creature, Posted by log1i_yk