Like numerous octopuses, the California two-spot octopus (Octopus bimaculoides) decreases and dies quickly after reproducing. Credit: Tom Kleindinst, Marine Biological Laboratory
Modifications in cholesterol production cause a tragic octopus death spiral.
New research finds exceptional parallels in steroid hormone biology throughout cephalopods, mice, and people that can have dire effects when interrupted.
Despite their astonishing intelligence and relatively supernatural capabilities to change color and restore limbs, octopuses typically suffer a tragic death. After laying a clutch of eggs, a mother octopus stops consuming and wastes away; by the time the eggs hatch, she is dead. Some women in captivity even appear to speed up this process deliberately, mutilating themselves and twisting their arms into a tangled mess.
The source of this strange maternal habits seems to be the optic gland, which is an organ similar to the pituitary gland in mammals. Just how this gland activated the gruesome death spiral has been uncertain for many years, however a new study by researchers from the University of Chicago, the University of Washington, and the University of Illinois Chicago (UIC) reveals that the optic gland in maternal octopuses undergoes an enormous shift in cholesterol metabolic process, leading to significant modifications in the steroid hormones produced.
Changes in cholesterol metabolic process in other animals, consisting of humans, can have major repercussions on longevity and behavior, and the research studys authors think this exposes important resemblances in the functions of these steroids throughout the animal kingdom, in soft-bodied cephalopods and vertebrates alike.
” We understand cholesterol is essential from a dietary point of view, and within various signaling systems in the body too,” said Z. Yan Wang, PhD, Assistant Professor of Psychology and Biology at the University of Washington and lead author of the research study. “Its involved in whatever from the versatility of cell membranes to production of stress hormonal agents, however it was a big surprise to see it play a part in this life process as well.”
Self-destruct hormones
In 1977, Brandeis University psychologist Jerome Wodinsky showed that if he eliminated the optic gland from Caribbean two-spot octopus (Octopus hummelincki) mothers, they abandoned their clutch of eggs, resumed feeding, and lived for months longer. At the time, cephalopod biologists concluded that the optic gland should secrete some kind of “self-destruct” hormone, but just what it was and how it worked was unclear.
In 2018, Wang, then a college student at the University of Chicago, and Clifton Ragsdale, PhD, Professor of Neurobiology at UChicago, sequenced the RNA transcriptome of the optic gland from a number of California two-spot octopuses (Octopus bimaculoides) at different stages of their maternal decline. RNA brings guidelines from DNA about how to produce proteins, so sequencing it is a great way to understand the activity of genes and whats going on within cells at an offered time. As the animals started to quick and decline, there were greater levels of activity in genes that metabolize cholesterol and produce steroids, the very first time the optic gland had actually been linked to something besides reproduction.
The optic gland of mom octopuses undergoes an enormous increase in cholesterol production, which might activate its unusual reproductive habits. Credit: Kathryn Knight, UChicago
In the new paper, released on May 12, 2022, in the journal Current Biology, Wang and Ragsdale took their research studies a step even more and analyzed the chemicals produced by the maternal octopus optic gland. They worked with Stephanie Cologna, PhD, Associate Professor of Chemistry at UIC, and Melissa Pergande, a previous college student at UIC, who focuses on mass spectometry, a strategy that analyzes the chemical composition of biological samples. Because Wangs previous research study pointed to increased activity in the genes that produce steroids, they focused on cholesterol and related molecules in the optic gland tissue.
They discovered 3 various pathways associated with increasing steroid hormonal agents after reproduction. One of them produces pregnenolone and progesterone, 2 steroids frequently connected with pregnancy. Another produces maternal cholestanoids or intermediate elements for bile acids, and the 3rd produces increased levels of 7-dehydrocholesterol (7-DHC), a precursor to cholesterol.
The brand-new research study shows that the maternal optic gland goes through remarkable changes to produce more pregnenolone and progesterone, maternal cholestanoids, and 7-DHC during the stages of decline. While the pregnancy hormonal agents are to be expected, this is the very first time anything like the parts for bile acids or cholesterol have actually been linked to the maternal octopus death spiral.
Some of these exact same paths are utilized for producing cholesterol in mice and other mammals. “There are 2 major paths for developing cholesterol that are understood from studies in rodents, and now theres evidence from our study that those pathways are probably present in octopuses also,” Wang stated. “It was actually amazing to see the resemblance throughout such various animals.”
Elevated levels of 7-DHC are toxic in people; Its the trademark of a hereditary disorder called Smith-Lemli-Opitz syndrome (SLOS), which is triggered by a mutation in the enzyme that converts 7-DHC to cholesterol. Children with the disorder suffer from serious developmental and behavioral consequences, including repetitive self-injury similar to octopus end-of-life behaviors.
Tiny and underappreciated
The findings recommend that disturbance of the cholesterol production procedure in octopuses has serious repercussions, just as it carries out in other animals. Far, what Wang and her team have found is another action in the octopus self-destruct series, signifying more modifications downstream that ultimately lead to the mothers odd behavior and demise.
” Whats striking is that they go through this development of modifications where they seem to go insane right prior to they die,” Ragsdale said. “Maybe thats two processes, possibly its three or 4. Now, we have at least 3 apparently independent pathways to steroid hormonal agents that could represent the multiplicity of effects that these animals reveal.”
Unlike numerous octopus species, the lower striped octopus types numerous times. Credit: Tim Briggs, Marine Biological Laboratory
This summer season, Wang will be studying at the UChicago associated Marine Biological Laboratory (MBL) as part of the Grass Fellowship, before she joins the faculty at the University of Washington. A significant draw of MBL is their extensive cephalopod research program, in specific a brand-new model animal, the lesser Pacific removed octopus (Ocotopus chierchiae). To name a few useful functions like its small, manageable size, the striped octopus doesnt self-destruct after reproducing like the animals Wang and Ragsdale have been studying so far. Wang prepares to examine the striped octopuss optic glands and compare them to her new outcomes to look for ideas regarding how it avoids the tragic octopus death spiral.
” The optic gland exists in all other soft-bodied cephalopods, and they have such divergent reproductive methods,” she stated. “Its such a tiny gland and its underappreciated, and I think its going to be exciting to check out how it contributes to such a terrific diversity of biography trajectories in cephalopods.”
Referral: “Steroid hormones of the octopus self-destruct system” by Z. Yan Wang, Melissa R. Pergande, Clifton W. Ragsdale and Stephanie M. Cologna, 12 May 2022, Current Biology.DOI: 10.1016/ j.cub.2022.04.043.
The research study, “Steroid hormonal agents of the octopus self-destruct system,” was supported by the National Science Foundation, the University of Illinois Chicago, the Illinois Board of Higher Education, and the Marine Biological Laboratory.
In 2018, Wang, then a graduate trainee at the University of Chicago, and Clifton Ragsdale, PhD, Professor of Neurobiology at UChicago, sequenced the RNA transcriptome of the optic gland from a number of California two-spot octopuses (Octopus bimaculoides) at different phases of their maternal decline. In the new paper, published on May 12, 2022, in the journal Current Biology, Wang and Ragsdale took their studies an action even more and analyzed the chemicals produced by the maternal octopus optic gland. “There are 2 major pathways for producing cholesterol that are understood from studies in rodents, and now theres proof from our study that those pathways are most likely present in octopuses as well,” Wang said. Among other helpful functions like its small, manageable size, the striped octopus does not self-destruct after reproducing like the animals Wang and Ragsdale have actually been studying so far. Wang plans to take a look at the striped octopuss optic glands and compare them to her brand-new outcomes to look for hints as to how it avoids the terrible octopus death spiral.
