EEBIOL-169 Biology of Bats First Midterm Review

Bats are the only mammals capable of powered flight

Bats use echolocation to navigate and hunt insects

Bats can have health and life spans longer than humans

Bats can harbor many viruses (eg. Ebola, SARS-CoV) but NOT get sick-> Inflammation processes, ecological and evolutionary perspective

1 out of 5 mammals is a bat, and bats live on every continent except Antartica-> abundant and diverse

Bats include the only mammalian species that feeds exclusively on blood

Key take aways from lecture 1

Mammalia

Class

Laurasiatheria

Superorder

Chiropetera

Order

Yinpterchiroptera

most non-echolocating bats, mostly larger bat species

Yangochiroptera

all echolocating bats

Forelimb anatomy indicates that the earliest known bats were capable of powered flight like other Eocene bats, but ear morphology suggests that they lacked their echolocation abilities

flight fight' hypothesis for chiropteran evolution.

"While there is consensus that powered flight evolvedonly once in the lineage, whether laryngealecholocation has a single origin in bats or evolved multiple times independently remains disputed."

Non-echolocating ancestor and independent gain in Yin and Yang-> because the cochlea of Yin and Yang develops different

Primitively echolocating ancestor, followed by convergent evolution of laryngeal echolocation in Yin and Yang and loss of echolocation in most pteropodids.

Embryonic evidence supports multiple origins of laryngeal echolocation in bats, and either:

wingspan/wing chord

higher-> narrow

lower-> spare

aspect ratio

body weight/wing area

wing loading

dactylopatagium is the retention of embryonic state

bats' arms are bigger

zones that control outgrowth (ZPA and AER) are bigger

fingers: Bmp→ cell death that lead to free digit, however, this gene is inhibited in bats by Gre & Fgfs

homologous divergence

Plagiopatagium and uropatagium

Evolutionary Novelty

1. Novel Outgrowth

2. Limb/patagial merging: Ripk4 gene is altered (kind of inhibited)-> plagiopatagial-limb fusion in bats

3. Diverge: plagiopatagial shape begins to diverge after merging

Hypotheses for the evolution of the plagiopatagium

-Early stages are highly conserved in novel outgrowth and merging

-the conservation might be caused by shared common ancestors

Conservation of plagiopatagial growth

rods and cones

vision cells

rods

black and white

L cones

greenish light; OPN1LW

S cones

UV light; OPN1SW; lost in some bats

part of the olfactory sensory system, whose role is to pass along smell sensations to the brain

Olfactory epithelium

receptors on the epithelium

Olfactory receptors

Bones that protrude into the nasal cavity- they increase surface area for filtering dust and dirt particles by the mucous membrane.

Bones on the skull

Turbinates

TRPC2 protein

relates to pheromone

VNOs appear to be largely conserved in the Phyllostomidae and Miniopteridae mainly fruit-eating bats

dice CT scans

multiple losses

Vomeronasal organ

fruit bats

which types of bats would you expect to have a well-developed olfactory epithelium/receptor complex?

Plant-visiting bat>animal feeding

relatively larger surface areas suggest greater reliance on olfactory detection

Iodine-stained microCT-scans were used to reconstruct olfactory epithelium of the turbinates

Non-echolocating ancestor and independent gain in Yin and Yang

Primitively echolocating ancestor, followed by convergent evolution of laryngeal echolocation in Yin and Yang and loss of echolocation in most pteropodids.

Embryonic evidence supports multiple origins of laryngeal echolocation in bats

Oral: emit calls from the mouth

Nasal: keep the mouth close; sometimes have nose-leave

Two Groups: Oral (mostly in Yang) vs Nasal emitters(mostly in Yin.)

physically thicker in this frequency

Doppler shift compensation: change the frequency emitting in order to make the echo on the same level

Constant frequency echolocation:

Mostly non except Rousettus sp

Click echolocation produce clicks in pairs (one of each lip) by raising the tongue from the floor of the mouth

Pteropodidae

Insects use ultrasound to prevent bats

Ecology and Species Interactions:Insects

disguise location by jamming the sonar bat will run away directly, just like ignoring it

tell the bats they are poisonous by ultrasound→ most in african bats species run away after Batesian Mimicry some are trying to bluff the bat

Ways of sound protection

Flight is costlier per unit time than any other mode of locomotion STRONG SELECTION!!!!! → tight association between the environment

Bats exchange fat reserves every 24 hours = daily risk of starvation

Energetic demands of flight select for minimal mass in bats

Bats stand on the edge of the "Selective envelope"

Bat skulls are likely more "optimized" to meet demands than other mammals

selection envelope

Sequenced the visual cone opsin genes in 33 species of bats with diverse sensory ecologies

While the long-wave opsin gene was conserved in all species, a functional short- wave opsin gene was lost many times. short-wave → UV light

Loss of a functional short-wave opsin gene directly coincided with the origin of high-duty-cycle echolocation and changes in roosting ecology in some lineages. cave→ lost UV light sight tree→ tend to be retain →these are CORRELATION!!!!!

Zhao et al, 2009, PNAS: The evolution of color vision in nocturnal mammals

Generally across all bats

Used modern phylogenetic tools and 3D geometric morphometric datasets to examine adaptive zone shifts in bat skull shape.

Bat skull shape evolution exhibits multiple adaptive zone shifts.

Compared shifts in shape to shifts in echolocation and diet; neither were a great fit

However, echolocation's fit was stronger

Arbour et al, 2019, Nature Comm: Signatures of echolocation and dietary ecology in the adaptive evolution of skull shape in bats

Also, phyllostomids are weird→ not significant in this study big evolution radiation in this group may be due to exposure to environment + plasticity in skulls

Phyllostomids

Focus on phyllostomids

Investigated relationship between the evolution of sensory structures and diet during the radiation of noctilionoid bats

Measured volumes of sensory tissues (CT scans) then construct phylogeny if there is tradeoffs

Hall et al, 2021, Nature Comm An omnivorous sensory morphotype predates biomechanical specificalization for plant based diets in phyllostomids(micro)

Frugivores have larger olfactory bulbs + orbits; Animalivores have smaller olfactory bulbs + orbits; Nectarivores have smaller cochlea

Different bats species

observe-expected

residual

Results suggest that enlargement of the visual and olfactory structures, perhaps associated with a foray into omnivory, preceded the clade's radiation

Does NOT seem to be an obvious trade-off in the size of sensory structures

Ancestral state reconstructions suggest that phyllostomids "found the food first"

Results from Hall et, al

Popliteal Pterygium Syndrome

fusion of skin from limb and flank Periderm is a non-stick layer that prevents the fusion

Ripk4 knockout mice then shows a phenotype of skin fusion Cellular behaviors during plagiopatagial-limb fusion in bats are largely consistent with those observed in Ripk4 KO mice

Ripk4 gene

higher-> narrow-> open air

low-> wider-> cluttered habitats

HOWEVER, due to the limited range change, this is not a good indicator of habits

Aspect Ratio

bats camber were larger-> more curvature

Low-speed flight was more difficult

increase in wing amplitude-> increase in horizontal force

Inject Botox to test the plagiopatagium

flapping frequency and amplitude

Generation of Lift

earliest known bat

capable of powered flight -> from wing proportion

not unable to echolocate-> from cochlea size

Onychonycteris

the first echolocating bats due to evidence from the skull property

Icaryonycteris

horseshoe bats

What type of bat is suspected to have been a major player in the origins of SARS-CoV2?

Goblet

According to the movie, the virus that causes COVID-19 enters the body through the same type of cells in bats and humans. What is the name of this type of cells?

interferon alpha

Which gene's permanently "on" status in cave nectar bats is thought to give these bats a proactive strategy of immune defense?

True

Scientist Emma Teeling believes there is a link between the bat's unique ability to fly and their ability to combat sickness.

Mexican free-tailed

The _____________ bat was clocked at to speeds of about 100 miles per hour, giving it the fastest horizontal flight of any animal ever recorded.

About 1000bpm

What is the maximum heart rate that is reached by some flying bats?

plagiopatagium

Drs. Sharon Swartz, Kenny Breuer, and Andrea Rummel have been studying the biomechanics of bat flight using Egyptian fruit bats. In their experiments, they read body temperature by attaching tiny thermometers to 3 different muscles while the bat's flight is monitored. Based on their findings, in which of the labeled muscles (A, B, or C) in the diagram would you expect them to observe a decline in temperature as the bat flies?

High metabolism

According to the video, what was a major challenge that ancient bats had to overcome when they developed the ability to fly?

No, human cells have an immune response while bat cells do not

In the NLRP3 study described in the video, do bat cells and human cells have the same inflammatory response when triggered by toxins?

myotis bats

Dr. Emma Teeling and her group found that telomeres of the longest-lived bat clade do not shorten with age as do the telomeres of some other bats and mammals. Which of the following is the clade of longest-lived bats to which Dr. Teeling was referring?

Retina

What is the name of the light-sensitive layer of tissue in the eyes of bats?

Bats have more L than S cones

Which of the following is a correct statement about bat photoreceptors?

Losses occur through disruptions in DNA sequence, transcription, and translation

Some bats appear to have lost their S cones. Through which of the following mechanisms does it appear that the S cones have been lost in bats?

Bats that eat fruit

Which of the following types of bats are most likely to retain their S cones?