PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Breaking the patrisharky: Scientists reexamine gender biases in shark, ray mating research

New study analyzes biological drivers of multiple paternity in sharks and rays, challenging decades of unbalanced research

Breaking the patrisharky: Scientists reexamine gender biases in shark, ray mating research
2021-03-04
(Press-News.org) Shark scientists at Georgia Aquarium, Scripps Institution of Oceanography at UC San Diego, and Dalhousie University are challenging the status quo in shark and ray mating research in a new study that looks at biological drivers of multiple paternity in these animals. The results were published March 4 in the journal Molecular Ecology.

Many species of sharks and rays exhibit multiple paternity, where females give birth to a litter of pups that have different fathers. While widely documented in scientific literature, the drivers of this phenomenon are not well understood. However, previous research has cited male aggression as the reason, claiming that the females are unable to avoid or submit to their advances during mating. This has led to the "convenience polyandry" theory, the assumption that there is a greater cost for females when refusing male mating attempts, as being the most widely credited explanation.

"If convenience polyandry is the only reason we talk about, it takes the agency away from females," said Kady Lyons, research scientist at Georgia Aquarium and lead author of the study. "If she's investing all this energy into making big babies, why doesn't she get a say in who will be the sire of her offspring?"

While multiple paternity has been documented in many elasmobranchs (sharks and rays), this is the first study to evaluate it starting from the female point-of-view. The researchers note that most studies on shark and ray reproduction were conducted by male scientists, and their biases could manifest in their research.

"No matter how objective we try to be as scientists, we're still human and our experiences are brought to the table," said Dovi Kacev, assistant teaching professor at Scripps Oceanography and a co-author of the study.

The researchers developed models based on shark and ray biology and physiology to test whether multiple paternity could be in the best interest of females or males, or a combination of both. They looked for patterns that they would expect to see if this phenomenon was pushed or pulled by one sex or the other, such as sperm competition or female selection for sperm genetic diversity, and compared it to data from past studies and their own research on these animals. By asking, "Would this benefit a male or a female?" they found no conclusive evidence that multiple paternity is primarily a male-driven advantage. In most instances, the benefits for females and males were the same, challenging previous ideas that male behavior and biology drives multiple paternity.

"Male or female drivers may sometimes produce the same multiple-paternity end result, but more often than not it is the male factors that get the lion's share of the credit," Lyons said. "This seemed odd to me considering how complex and energetically taxing female reproduction is."

The researchers stress that uncovering which sex (or both) may be responsible for the observed patterns is difficult as elasmobranchs have been evolving over many millions of years, and observing shark and ray mating is a rare occurrence. The scientists, however, found clues in what science does know about elasmobranch mating and reproduction.

Elasmobranch mating can be quite violent. In many cases, males bite the females to secure a hold, inflicting injury and leaving scars. This can even be seen in some of the more docile species like manta rays. Females have, however, developed advantages such as thicker skin in bite-prone areas in order to better recover from the mating injuries. In many species, the females are also often much larger than males.

While it does take energy for females to recover from wounds or avoid frisky males by swimming away, this only represents the beginning of their energetic investment into reproduction. The researchers point out that female elasmobranchs devote a lot of resources to the production of developed young, such as through ovulation of fat-rich eggs and providing nutrition to embryos in species that have internal gestation, which is the norm for most sharks and rays.

"One thing that is underappreciated, even by experts, is how diverse sharks and rays are," said Christopher Mull, postdoctoral fellow at Dalhousie University and a co-author of the study. "When it comes to reproduction, sharks and rays use every mode that has been described in vertebrates, from laying eggs to giving live birth with a placenta, similar to humans."

This diversity of sharks and rays makes them an interesting animal group to study multiple paternity, and for examining sex roles in the animal kingdom, said the researchers. The typical number of offspring can vary widely between species, from a single pup up to several hundred. The smallest of sharks can fit in the palm of a human hand, while the largest can grow to the size of a school bus. Despite these differences in biology and physiology, the phenomenon of multiple paternity appears to be a common trait across sharks and rays.

This evolutionary advantage, and the idea that it could be driven by the biology of the females, has been of keen interest to Lyons throughout her research. In a previous study, she found that round stingrays, native to the California coast, can exhibit different patterns of paternity. These rays have two uteri, and Lyons showed that in some females, one uterus held offspring with the same father while the other held offspring of a different father. In other individuals, offspring paternity was mixed between the two uteri. This was hypothesized as females ovulating in different patterns, which may give them some control over which males were able to fertilize their eggs.

Female elasmobranchs have other physiological abilities that suggest they might be behind multiple paternity. Some species have serial ovulation, in which one egg at a time is produced and fertilized. It has been shown that some can store sperm, thereby preventing the sperm from one male from fertilizing an egg, or using this ability to save sperm from another male that could be used in the future. Essentially, females have the anatomical tools that may allow them to control which sperm fertilize their eggs.

From past data, the researchers found many examples of pregnant female sharks with "failed ova" (those that were in the process of being resorbed) alongside normally developing embryos. If reproduction was driven by males, the scientists asked, why would the female miss the opportunity to pass on her genes as well? These examples bolster their idea that the reasons for multiple paternity cannot be attributed to only one sex.

"Female elasmobranchs have these incredible physiology mechanisms that give them a reproductive advantage, but these are largely ignored in the literature," Lyons said.

"I think a key takeaway from our work is challenging the dog(fish)ma that female sharks and rays are passive players in the mating process," said Mull. "But demonstrating these mechanisms at work can be really challenging, so we focused on developing a series of testable hypotheses that other researchers can apply to their own work."

The researchers note that while this study is on sharks and rays, it has implications for the larger animal kingdom, and for diversity in science.

"Diversifying perspectives at the table will enrich scientific studies," said Kacev. "We're not saying the male perspective is wrong, or that male sharks aren't at all responsible for multiple paternity, but it takes two to tango."

"Perspective is completely shaped by background," said Lyons. "If you don't have a diverse background, your perspective will be limited."

INFORMATION:

This study was funded by the Shark Conservation Fund and Georgia Aquarium.


[Attachments] See images for this press release:
Breaking the patrisharky: Scientists reexamine gender biases in shark, ray mating research

ELSE PRESS RELEASES FROM THIS DATE:

In professional athletes, heart risk after mild COVID-19 is very low, finds study

2021-03-04
NEW YORK, NY (March 4, 2021)--Inflammatory heart disease is a rare finding among professional athletes with mild or asymptomatic COVID-19 infection, a large-scale study has found. The study, led by Columbia University Vagelos College of Physicians and Surgeons in collaboration with the major North American sports leagues and their respective players' associations, was published online today in JAMA Cardiology. Athletes and COVID-19 Studies suggest that approximately 20% of patients hospitalized with severe COVID-19 develop some type of heart damage, but the impact of mild or asymptomatic ...

Demand for public health graduates remains high through the COVID-19 pandemic

2021-03-04
March 4, 2021 -- COVID?19 has altered the labor market for millions of people, including public health graduates, yet an analysis of job postings for Master's level public health graduates showed that job postings remained at the same levels as before the pandemic, according to a new study at Columbia University Mailman School of Public Health. The findings are published in the International Journal of Health Planning and Management. "Due to the crucial role of disease prevention in responding to and recovering from the COVID?19 pandemic, assessing the public health workforce remains critically important," said Heather Krasna, MS, EdM, assistant dean of career services at Columbia Mailman School, and lead author of the study. "Fortunately, the job market for master's ...

Equitably allocating COVID-19 vaccine

2021-03-04
PHILADELPHIA (March 4, 2021) - Equitable implementation of COVID?19 vaccine delivery is a national and global priority, with a strong focus on reducing existing disparities and not creating new disparities. But while a framework has been recognized for equitable allocation of COVID?19 vaccine that acknowledges the rights and interests of sexual and gender minorities (SGM), it fails to identify strategies or data to achieve that goal. A new study with support from researchers at the University of Pennsylvania School of Nursing (Penn Nursing) examined the prevalence ...

Original error

2021-03-04
There is no stronger risk factor for cancer than age. At the time of diagnosis, the median age of patients across all cancers is 66. That moment, however, is the culmination of years of clandestine tumor growth, and the answer to an important question has thus far remained elusive: When does a cancer first arise? At least in some cases, the original cancer-causing mutation could have appeared as long as 40 years ago, according to a new study by researchers at Harvard Medical School and the Dana-Farber Cancer Institute. Reconstructing the lineage history of cancer cells in two individuals with a rare blood cancer, the team calculated when the genetic mutation that ...

Extreme-scale computing and AI forecast a promising future for fusion power

Extreme-scale computing and AI forecast a promising future for fusion power
2021-03-04
Efforts to duplicate on Earth the fusion reactions that power the sun and stars for unlimited energy must contend with extreme heat-load density that can damage the doughnut-shaped fusion facilities called tokamaks, the most widely used laboratory facilities that house fusion reactions, and shut them down. These loads flow against the walls of what are called divertor plates that extract waste heat from the tokamaks. Far larger forecast But using high-performance computers and artificial intelligence (AI), researchers at the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) have predicted a far larger and less damaging heat-load width for the full-power operation of ITER, the international tokamak under construction in France, than previous estimates ...

Animal aggression depends on rank within social hierarchies

Animal aggression depends on rank within social hierarchies
2021-03-04
Humans and animals alike constantly size up one another. In the workplace, a new employee quickly learns which coworkers are the most respected -- and therefore hold more power. Big brothers boss around little brothers. In nature, a dominant male chimpanzee fights off would-be intruders. Even fish and octopi interact within social hierarchies. These pecking orders have been studied within the behavioral ecology world for almost 100 years. How individuals interact can affect access to food and mates -- even survival -- and insights into those behaviors can lead to better management of threatened and endangered populations. But few studies have explored what the animals ...

Cancer 'guardian' breaks bad with one switch

Cancer guardian breaks bad with one switch
2021-03-04
HOUSTON - (March 4, 2021) - A mutation that replaces a single amino acid in a potent tumor-suppressing protein turns it from saint to sinister. A new study by a coalition of Texas institutions shows why that is more damaging than previously known. The ubiquitous p53 protein in its natural state, sometimes called "the guardian of the genome," is a front-line protector against cancer. But the mutant form appears in 50% or more of human cancers and actively blocks cancer suppressors. Researchers led by Peter Vekilov at the University of Houston (UH) and Anatoly Kolomeisky at Rice University have discovered the same mutant protein can aggregate into clusters. These in turn nucleate the formation of amyloid fibrils, a ...

Recommended for you: Role, impact of tools behind automated product picks explored

Recommended for you: Role, impact of tools behind automated product picks explored
2021-03-04
As you scroll through Amazon looking for the perfect product, or flip through titles on Netflix searching for a movie to fit your mood, auto-generated recommendations can help you find exactly what you're looking for among extensive offerings. These recommender systems are used in retail, entertainment, social networking and more. In a recently published study, two researchers from The University of Texas at Dallas investigated the informative role of these systems and the economic impacts on competing sellers and consumers. "Recommender systems have become ubiquitous in e-commerce platforms and ...

Woolly mammoths may have shared the landscape with first humans in New England

Woolly mammoths may have shared the landscape with first humans in New England
2021-03-04
Woolly mammoths may have walked the landscape at the same time as the earliest humans in what is now New England, according to a Dartmouth study published in END ...

Thin explosive films provide snapshot of how detonations start

2021-03-04
ALBUQUERQUE, N.M. -- Using thin films -- no more than a few pieces of notebook paper thick -- of a common explosive chemical, researchers from Sandia National Laboratories studied how small-scale explosions start and grow. Sandia is the only lab in the U.S. that can make such detonatable thin films. These experiments advanced fundamental knowledge of detonations. The data were also used to improve a Sandia-developed computer-modeling program used by universities, private companies and the Department of Defense to simulate how large-scale detonations initiate and propagate. "It's neat, we're really pushing the limits on the ...

LAST 30 PRESS RELEASES:

From camera to lab: Dr. Etienne Sibille transforms brain aging and depression research

Depression rates in LGBTQIA+ students are three times higher than their peers, new research suggests

Most parents don’t ask about firearms in the homes their kids visit

Beer-only drinkers’ diets are worse than wine drinkers

Eco-friendly biomass pretreatment method yields efficient biofuels and adsorbents

How graph convolutions amplify popularity bias for recommendation?

New lignin-based hydrogel breakthrough for wound healing and controlled drug release

Enhancing compatibility and biodegradability of PLA/biomass composites via forest residue torrefaction

Time alone heightens ‘threat alert’ in teenagers – even when connecting on social media

Study challenges long-held theories on how migratory birds navigate 

Unlocking the secrets of ketosis

AI analysis of PET/CT images can predict side effects of immunotherapy in lung cancer

Making an impact. Research studies a new side of helmet safety: faceguard failures

Specific long term condition combinations have major role in NHS ‘winter pressures’

Men often struggle with transition to fatherhood amid lack of targeted information and support

More green space linked to fewer preventable deaths in most deprived areas of UK

Immunotherapy drug pembrolizumab improves outcomes for patients with soft tissue sarcoma

A formula for life? New model calculates chances of intelligent beings in our Universe and beyond

Could a genetic flaw be the key to stopping people craving sugary treats?

Experts urge complex systems approach to assess A.I. risks

Fossil fuel CO2 emissions increase again in 2024

Winners of Applied Microbiology International Horizon Awards 2024 announced

A toolkit for unraveling the links between intimate partner violence, trauma and substance misuse

Can everyday physical activity improve cognitive health in middle age?

Updated guidance reaffirms CPR with breaths essential for cardiac arrest following drowning

Study reveals medical boards rarely discipline physician misinformation

New treatment helps children with rare spinal condition regain ability to walk

'Grow Your Own' teacher prep pipeline at the University of Louisiana at Lafayette funded by US Department of Education

Lab-grown human immune system uncovers weakened response in cancer patients

More than 5 million Americans would be eligible for psychedelic therapy, study finds

[Press-News.org] Breaking the patrisharky: Scientists reexamine gender biases in shark, ray mating research
New study analyzes biological drivers of multiple paternity in sharks and rays, challenging decades of unbalanced research