Posts Tagged ‘Molly’


An Amazon molly, Poecilia formosa, an asexual fish species native to Texas that is entirely female.

By Shana Hutchin

Highlights

The Amazon molly has flourished by defying nature’s odds to reproduce asexually, cloning themselves by duping the male fish of another species to waste their germplasm

Females steal the entire genome of their host males, keep it for one generation and then throw it out again

The existence of Amazon mollies back anywhere from 100,000 to 200,000 years ago to a sexual reproduction event involving two different species of fish

Faculty Fellow Dr. Manfred Schartl led the international team that recently sequenced the first Amazon molly fish genome

No species is immune from the suffering of unrequited love, but scientists expect to learn volumes about the biological basis of sex from the newly sequenced genome of an all-female, asexual Texas native – the Amazon molly fish – that has thrived as a master of male manipulation over millennia.

The fresh waters along the Texas-Mexico border serve as home to this evolutionary anomaly – a fish that has flourished by defying nature’s odds to reproduce asexually through a natural form known as parthenogenesis in which growth and development of embryos occurs without fertilization, resulting only in daughters that are true clones of their mothers.

Texas A&M University Hagler Institute for Advanced Study (HIAS) Faculty Fellow Dr. Manfred Schartl led the international team that recently sequenced the first Amazon molly genome and the genomes of the original parental species that created this unique fish in an effort to better understand how its reproduction deviates from the male-female sexual norm and why the Amazon molly as a species has fared so well in the process.

The evolution of sex

The findings from their National Institutes of Health-funded research are published online today (Feb. 12) in the Nature research journal Nature Ecology & Evolution.

“The existence of two sexes, male and female, is one of the oldest and most widespread phenomena in biology,” says Schartl, a world leader in cellular and molecular biology of Xiphophorus model systems including platyfish and swordtails. “Studies on the exceptional case of asexuality helps us to better understand the biological meaning and evolution of sex.”

Animals that reproduce asexually are rare, compared to the overwhelming majority of species that exist as males and females and reproduce sexually. Because it was long thought that vertebrates would not be able to exist in such a way, Schartl says it was a sensation when the Amazon molly was the first asexual vertebrate discovered in 1932.

But even the most independent females occasionally need a male – in the Amazon molly’s case, to kick-start the parthenogenensis process. They seduce males from related sexual species for this service, which Schartl notes lacks the regular benefit for these males, which do not contribute their genes to the next generation.


An Amazon molly (right), caught in action while seducing a male Sailfin molly to steal sperm.

Thriving by cloning

“In essence, mollies repeatedly clone themselves by duping the male fish of another species to waste their germplasm,” Schartl says. “This reminds one of the tribe of female warriors in the Greek mythology, from which their name is derived.”

The team’s research traces the existence of Amazon mollies back anywhere from 100,000 to 200,000 years ago to a sexual reproduction event involving two different species of fish, an Atlantic molly and a Sailfin molly.

“That’s about 500,000 generations if you calculate it out to the present day, which makes them genetically older than humans,” Schartl says. “This is unexpected because asexuals are expected to be at disadvantage compared to their sexual counterparts.”

Schartl notes that one of the theories as to why asexual reproduction is incompatible with a species’ sustainability is the idea that if no new DNA is introduced during reproduction, then harmful gene mutations can accumulate over successive generations, leading to eventual extinction. Another hypothesis states that asexual reproduction is not like sexual reproduction, where the different genomes of the two parents are newly combined and create new genomes with every offspring. Because the absence of recombination in asexuals limits genetic diversity within a species, he says it gets more and more difficult to adapt to changes in the environment.

“Unexpectedly, we did not find the signs of genomic decay as predicted,” Schartl adds. “Our findings suggest that the molly’s thriving existence can be explained by the fact that the fish has a hardy genetic makeup that is often rare in nature and gives the animals some survival benefits.”

Schartl says the hybridization of the Atlantic and Sailfin mollies’ two different species genomes into a new one created a situation well known in the animal and plant breeding world — an artificial hybrid that is bigger, more colorful and capable of generating more and better products than the purebred parents, a phenomenon known as hybrid vigor.

https://today.tamu.edu/2018/02/12/texas-am-biologist-leads-international-team-that-sequences-first-amazon-molly-fish-genome/

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Psychedelics were highly popular hallucinogenic substances used for recreational purposes back in the 1950s and 1960s. They were also widely used for medical research looking into their beneficial impact on several psychiatric disorders, including anxiety and depression. In 1967, however, they were classified as a Class A, Schedule I substance and considered to be among the most dangerous drugs with no recognized clinical importance. The use of psychedelics has since been prohibited.

Psychiatrist and honorary lecturer at the Institute of Psychiatry, Psychology and Neuroscience, at Psychiatrist and honorary lecturer at the Institute of Psychiatry, Psychology and Neuroscience, at King’s College London, James Rucker, MRCPsych, is proposing to reclassify and improve access to psychedelics in order to conduct more research on their therapeutic benefits. He believes in the potential of psychedelics so much that late last month he took to the pages of the prestigious journal the BMJ to make his case. He wrote that psychedelics should instead be considered Schedule II substances which would allow a “comprehensive, evidence based assessment of their therapeutic potential.”

“The Western world is facing an epidemic of mental health problems with few novel therapeutic prospects on the horizon,” Rucker told Psychiatry Advisor, justifying why studying psychedelics for treating psychiatric illnesses is so important.

Rucker recognizes that the illicit substance may be harmful to some people, especially when used in a recreational and uncontrolled context. He cited anecdotal reports of the substance’s disabling symptoms, such as long-term emotionally charged flashbacks. However, he also believes that psychedelic drugs can have positive outcomes in other respects.

“The problem at the moment,” he argued, “is that we don’t know who would benefit and who wouldn’t. The law does a good job of preventing us from finding out.”

From a biological perspective, psychedelics act as an agonist, a substance that combines with a receptor and initiates a physiological response to a subtype of serotonin known as 5HT2a. According to Rucker, this process influences the balance between inhibitory and excitatory neurotransmitters.

“The psychedelics may invoke a temporary state of neural plasticity within the brain, as a result of which the person may experience changes in sensory perception, thought processing and self-awareness,” Rucker speculated. He added that psychedelic drugs can act as a catalyst that stirs up the mind to elicit insights into unwanted cycles of feelings, thoughts and behaviors.

“These cycles can then be faced, expressed, explored, interpreted, accepted and finally integrated back into the person’s psyche with the therapist’s help,” he explained. Reclassifying psychedelics could mean that the mechanism by which these substances can help with anxiety, depression and psychiatric symptoms could be studied and understood better.

Several experts in the field of drug misuse have disagreed strongly with Rucker’s proposals in this area, and are quick to refute his findings and recommendations. Nora Volkow, MD, director of the National Institute on Drug Abuse (NIDA), emphasized the fact that psychedelics can distort a person’s perception of time, motion, colors, sounds and self. “These drugs can disrupt a person’s ability to think and communicate rationally, or even to recognize reality, sometimes resulting in bizarre or dangerous behavior,” she wrote on a NIDA webpage dealing with hallucinogens and dissociative drugs.

“Hallucinogenic drugs are associated with psychotic-like episodes that can occur long after a person has taken the drug,” she added. Volkow also says that, despite being classified as a Schedule I substance, the development of new hallucinogens for recreational purposes remains of particular concern.

Rucker has several suggestions to help mediate the therapeutic action of the drug during medical trials, and thereby sets out to rebut the concerns of experts such as Volkow. When a person is administered a hallucinogen, they experience a changed mental state. During that changed state, Rucker points out, it is possible to control what he describes as a “context,” and thereby make use of the drug more safe.

According to Rucker, the term “context” is divided into the “set” and the “setting” of the drug experience. “By ‘set,’ I mean the mindset of the individual and by ‘setting’ I mean the environment surrounding the individual,” he explained.

To prepare the mindset of the person, Rucker said that a high level of trust between patient and therapist is essential. “A good therapeutic relationship should be established beforehand, and the patient should be prepared for the nature of the psychedelic experience,” he suggested. The ‘setting’ of the drug experience should also be kept closely controlled — safe, comfortable and low in stress.

It is also necessary to screen participants who undergo the drug experience in order to minimize the risk of adverse effects. Rucker suggested screening patients with an established history of severe mental illness, as well as those at high risk of such problems developing. It is also important to screen the medical and drug history of participants.

“The action of psychedelics is changed by many antidepressant and antipsychotic drugs and some medications that are available over the counter, so a full medical assessment prior to their use is essential,” he said.

In order to avoid the danger of addiction, psychedelics should be given at most on a weekly basis. Indeed, for many patients, very few treatments should be required. “The patient may need only one or two sessions to experience lasting benefits, so the course should always be tailored to the individual,” Rucker advised.

If there are any adverse effects during the psychedelic experience, a pharmacological antagonist or antidote to the drug can be administered to immediately terminate the experience. “This underlines the importance of medical supervision being available at all times,” Rucker noted.

Psychedelics are heavily influenced by the environment surrounding the drug experience. Rucker is proposing they be administered under a controlled setting and with a trusted therapist’s supervision. Together with a reclassification of the drug, medical research could generate a better understanding and application of the benefits of psychedelics to mental health.

1.Rucker JJH. Psychedelic drugs should be legally reclassified so that researchers can investigate their therapeutic potential. BMJ. 2015; 350:h2902.

http://www.bmj.com/content/350/bmj.h2902/related