For dance flies, size does matter

UTM study shines light on sexual differences in animal mating behaviour

For dance flies, size does matter

For female North American dance flies, size definitely matters.

A recent UTM study discovered that, for North American male dance flies, sexual attraction is highest when female mates display large inflatable abdominal sacs. 

The study was published in Proceedings of the Royal Society B by UTM postdoctoral fellow Rosalind Murray, UTM biology professor Darryl Gwynne, U of T biology lecturer Jill Wheeler, and University of Stirling biologist Luc Bussiere.

To attract male dance flies for fertilization, the researchers found that female flies display signs of sexual ornamentation. The female flies use valuable energy reservoirs to expand their abdominal sacs, which is appealing to their male counterparts. 

In cases where female dance flies have smaller abdominal sacs, they attract males flies through larger leg scales.  

When discussing the reasoning behind her study, Murray said she “wanted to do an experiment to see if these ornaments were actually attracting the males and if they were working in the same way we typically see male ornaments — so, bigger is better.”

Why are the female flies using large amounts of energy to attract their male counterparts? 

According to Murray, the male flies provide them with a “food gift,” because the female flies have lost their ability to hunt, “so the males go hunting and they bring, usually another fly or insect. They kill it and they present it to the female in exchange for mating.”

The research took place over a 10-day period on an island in Credit River last June. North American dance flies are peculiar creatures that only appear for one hour at dawn and another hour at dusk.

As such, to complete the field research, Murray would wake up before sunrise to study the flies for an hour when they came out.  

During the day, Murray would analyze the data collected from the morning, and then she would venture out again at 8:30 pm to study the flies until sundown.

To test her theory, Murray created models that imitate female shapes and examined the impact of the two ornament types.

The research is particularly significant because it demonstrates a stark shift in our understanding of the animal kingdom. 

Typically, research has suggested that male animals use their energy to attract female counterparts. Much of Charles Darwin’s research, for example, focused on this phenomenon of sexual selection between mates.

However, Murray and Gwynne’s research turns this idea on its head.

“There are certain ways across animal kingdoms that males and females behave… It’s rare that you do find the vice versa, whereas in these flies, the subject of the paper, females are displaying very male-like traits,” Gwynne said. “They have reversed roles.”

Within the field of evolutionary biology, Murray’s study is the first that demonstrates this kind of female sexual ornamentation. “It’s such a bizarre system,” Murray said. 

“We’re looking at similar questions among many species of dance flies, thinking about how different species have evolved these ornaments.” 

With files from Srivindhya Kolluru

Researchers identify a Neanderthal-Denisovan hybrid

The discovery sheds light on our human ancestors

Researchers identify a Neanderthal-Denisovan hybrid

A single bone fragment can reveal thousands of years of human history.

In a study published in Nature, a team of researchers, including U of T Professor Bence Viola, identified a hybrid between two extinct lineages of hominids — Neanderthals and Denisovans — in a bone fragment.

Neanderthals lived on earth about 40,000 years ago, and, along with modern humans, they evolved from Homo erectus. Denisovans diverged from Neanderthals, but little is known about them other than bits of information recovered from bone fragments of their extremities, found in a Denisova Cave in Siberia’s Altai Mountains.

This is why, when researchers found a bone fragment in the Denisova Cave in 2012, they didn’t give much thought to the finding; it looked like all the others, an ordinary and tiny piece of what was thought to be part of a bear or lion.

After all, when a site is being excavated, many items are found, including pieces from animals and insects.

“There are 100,000 bone fragments found at a time and this particular one had a length of only 2.5 centimetres long, roughly the size of a toe bone,” said Viola.

A few years following the discovery, the fragments were analyzed for collagen. Finding a long bone fragment gave researchers an advantage for conducting DNA extraction techniques because of its morphology; it preserves better and allows for further manipulation.

“The bone was also discovered to have an acid coating which suggested it was digested by hyenas,” added Viola. The fact that DNA evidence survived this process makes this discovery even more extraordinary.

The bone was determined to belong to a female around age 13. This teenager died 90,000 years ago and was the offspring of a Neanderthal mother and Denisovan father.

Viola couldn’t believe it.

Based on previous studies, it was assumed that Neanderthals and Denisovans occasionally interacted, but interbreeding between the two hominins was thought to be rare.

This breakthrough informs researchers that interbreeding could have contributed to the gene flow, or transfer of genetic information, and it is now evident in the bone fragment.

The fragment is also evidence that the two species were in the same region at the same time.

Interbreeding is a result of various factors, such as an attempt to colonize certain areas. The discovery could help shape our understanding of hominin interactions and forms the basis to determine further benefits to interbreeding.

As such, this finding allows researchers to try and understand the lives of our closest ancient human relatives.

Dude, what’s that smell?

U of T study explains link between smell and memory

Dude, what’s that smell?

I am sitting at my maternal grandmother’s house in New Delhi, India. Masi, my aunt, has prepared a dish for me that she promises I will love. I don’t particularly like surprises, but I wait outside the kitchen.

I catch a whiff of something sweet. I can’t place it but it’s familiar. I close my eyes and I know it’s a smell from my childhood. Then it hits me. My Masi is making an Indian confection called almond halwa using my grandmother’s recipe.

This connection that I made — that we all make — between odour and memories, is explained in a study published in Nature Communications. The study, led by Afif J. Aqrabawi, a PhD candidate in the Department of Cell & Systems Biology at U of T, sheds light on this connection and how it could help develop new diagnostic tests for Alzheimer’s disease.

The hippocampus (HPC) is essential to episodic memory. It organizes memories of sensory events, including smell, in terms of space and time. The HPC stores the condition of the brain when said events take place, and then retrieves and recreates cerebral cortex activity of the original memory’s context when we encounter the sensation again.

The anterior olfactory nucleus (AON) is the largest source of feedback projections in the olfactory cortex, and the anatomical junction where the connection between olfactory and contextual information is made. HPC projections into the AON can alter the way smells are perceived and what behaviours are associated with specific odours.

Aqrabawi and Department of Psychology Professor Jun Chul Kim had determined that inputs from the HPC to the AON are necessary for the retrieval of odour memory based on spatial and temporal contexts. They knew the AON played a role in connecting spatial and olfactory events, but they did not know the exact function of the AON-HPC junction.

Thereafter, Aqrabawi and Kim found a neural pathway between the HPC and AON and they were able to define its role in memory retrieval. This pathway is responsible for contextual retrieval of odours and is affected in patients with Alzheimer’s.

In the study, mice whose AON-HPC junction was blocked kept returning to investigate the same scent even after being exposed to it several times prior. This was an indication that the AON plays a significant role in memory retrieval.

On the other hand, mice whose junctions were left to function normally spent less time smelling familiar odours because of the episodic memories associated with them. Inhibition of the HPC-AON pathway results in a loss of the odour memory linked to a given context in space and time.

This is the first study that demonstrates that inputs from the HPC to the olfactory cortex are necessary for forming and retrieving episodic odour memories. Findings from the study also show that the anatomical location of AON behind the olfactory bulb is an ideal bridge between olfactory and contextual information.

Multiple studies have reported a loss of olfactory function in Alzheimer’s patients. In fact, diagnostic smell tests are currently used to detect the earliest symptoms of the disease. This olfactory dysfunction is due to the neurodegeneration of the AON, which stores episodic odour engrams, during the early stages of Alzheimer’s disease.

Future research involving these findings will likely aim to better understand the connection between smell and memory, and particularly the neural circuits involved in this association.

Blind as a bat

Visual constraints were necessary for the evolution of echolocation in bats

Blind as a bat

 

Believe it or not, Batman was not the first winged creature to use echolocation to hunt down his prey — ancestors of the modern bat began using echolocation, the process in which objects are located by reflected sound, between 65 million and 85 million years ago.

John Ratcliffe, an Assistant Professor of Biology at UTM, and his team used molecular phylogeny techniques to decode the evolution of echolocation in bats, reconstructing our perspective on how and why these creatures came to be sonar crusaders of the night.

Their study, recently published in Nature Communications, has built on an existing phylogenetic study to reveal that bats evolved advanced biosonar capabilities through ancient tradeoffs between vision and echolocation.

Bats are the second largest order of mammals in the world, with more than 1,300 species. The bulk of these species are carnivorous and nocturnal, hunting small insects in the night using echolocation.

The researchers used phylogenetic comparative methods to understand evolutionary relationships between sensory systems, neuroanatomy, and morphology in bats. The results of the study indicate that ancestral bats possessed insufficient visual capabilities to hunt small prey at night but had the neuroanatomical potential to echolocate. This proved that there was a pre-existing opportunity for echolocation to flourish into an advanced sensory system in future descendants.

Evolutionarily, bats have continuously exhibited processes of behavioural tradeoff: species with poor echolocation abilities tend to have better visual resolution, and vice versa.

They further found that modern bats that use echolocation of the weakest frequency had the best vision out of those in all other sensory frequency groups, demonstrating that this tradeoff can function in either direction. The non-echolocating pteropodid is an example of a family with this tradeoff.

Surprisingly, the pteropodids have auditory brain regions the same size as echolocators. This vestige confirmed that bats from this family were once capable of echolocating but have since lost the trait. This is in contrast to the alternative scenario that proposes they evolved independently of echolocators — instead they are descendants of the same group.

This study not only answers questions about the evolution of a key trait of one of the most diverse mammals in the world, but it also cements the importance of phylogenetic research.

“It’s like replaying the video of evolution under different scenarios,” said Jeneni Thiagavel, the primary author of the paper, who has been working in this area of research for the past four years. “That essentially gives users [of these comparative methods] the power to reconstruct what that was like.”

Love makes scents

UTSC professor’s study finds ring-tail lemurs use ‘stink-flirting’ to attract mates

Love makes scents

If you think the smell of Axe is bad, be glad you’re not a lemur. In a study led by Amber D. Walker-Bolton, a UTSC professor in the Department of Anthropology, researchers found that male ring-tailed lemurs use their ‘stink’ to impress potential mates.

This unique behaviour allows lemurs to display their rank among other males and attract suitable mates, albeit at a cost.

Lemurs belong to the Strepsirrhine sub order and live in male groups that have a core female lineage. Each of these groups have dominant central males and periphery males, where rank is correlated with age.

‘Stink-flirting’ refers to male display of tail anointing and wafting, which is considered “a submissive display prior to a close approach.” The study found these displays are associated with male dominance and that they are reciprocated by females. Females preferred the exaggerated displays and are said to set the male apart from the rest of the population.

Additionally, the study found females showed a preference for dominant resident males as opposed to lower-ranking immigrant males. Immigrants are rarely found mating with females of the group.

Surprisingly, male lemurs are more frequently faced with aggression from both females and other males when they perform stink-flirting displays compared to other mating rituals. Only when females in estrus were receiving the olfactory display would they then mate.

Some of the females are also mate-guarded by a male. These guarded females were found to receive a higher rate of displays than non-guarded females. Although mate-guarding doesn’t completely eliminate displays from other males, it hinders approach to guarded females.

While the majority of females chose the most dominant mate, the opposite was not the case. According to the study, male ring-tailed lemurs did not “preferentially target high-ranked females for olfactory displays.”

In the future, Walker-Bolton’s team hopes to study the correlation between ‘stink-flirting’ and reproductive success.