Evolutionary Trade-Offs in Mammalian Sensory Perceptions: Visual Pathways of Bats By Adam Proctor Mentor: Dr. Emma Teeling
Visual Pathways of Bats Purpose Background on mammalian vision Tradeoffs and bats My project: Methods Species Results
Mammalian Vision Vision is an incredibly complex sense controlled by many proteins and the genes that code for them These include the opsins and IRBP Interphotoreceptor retinoid-binding protein is responsible for retina development and signal transduction Opsins (cones) are responsible for colour vision Most mammals have two distinct types: Short-wave sensitive (SWS) for blue light Medium or long-wave sensitive (M/LWS) for red/green
Monkey See, Monkey Do Blind Humans, apes, Old World monkeys, and howler monkeys underwent a duplication and diversification of Red/Green to Red and Green The result is full trichromatic vision: the ability to discriminate between blue, green, and red light Most other primates and mammals maintain dichromatic vision (red/green colourblindness) with only two opsin types Most marine and nocturnal mammals have lost blue opsin: monochromatic vision Blind mole rats have lost all three isoforms: total colour blindness Mole Don t
I ll Give You Vision for Hearing Deal! Some mammals appear to have reduced capabilities in other senses (i.e. hearing or smell) when they have specialized in another (i.e. vision) Is it possible that such trade-offs are common in mammalian evolution, and does it occur with other systems? And can we find genetic evidence for it?
Previous Genetic Studies on Sensory Trade-offs Gilad et al. (2004) found that trichromatic primates have proportionally more nonfunctional (pseudo) olfactory receptor genes than do dichromatic primates Trichromatic vision = loss of olfactory (smelling) capabilities Wang et al. (2004) sequenced S and M/LWS opsins from 2 megabats and 1 microbat Blue opsins shifted towards UV light
This project aimed to explore the genetic basis for vision in bats and further explore visual evolutionary trade-offs Why bats? Excellent example of evolutionary trade-off Ancestral bats probably relied mostly on echolocation (Teeling et al., 2005) 2 classes: Mega and micro Micro echolocate and have poor vision Megabats have lost their elcholocating ability (with one exception) and now rely mostly on vision and/or smell A Little Batty
Purpose See if bat opsins/irbp can be amplified Determine genetic components of vision for several species Blue and Red/Green opsin and IRBP Determine functionality and patterns of evolution Compare with echolocation abilities to look for evidence of an evolutionary trade-off
Methods for Madness Amplify and sequence opsin and IRBP genes Analyse functionality Compare with known species Create phylogenetic trees Reconstruct relationships between genes
PCR and Electrophoresis 2.5 L 10X buffer, 0.5 L dntps, 0.5 L primers, 0.2 L of Taq polymerase, 0.75 L MgCl 2, 18.05 L water, 2 L DNA 55-65 annealing Agarose gel electrophoresis
Study Species 1 Marmoset (for reference) 2 Megabats 8 Microbats
Goeldi's marmoset Callimico goeldii
Rousettus lanosus Long-haired Rousette Megabat Rousettus amplexicaudatus
Nyctimene albiventer Tube-nosed fruit bat Megabat
Tonatia silvicola D'Orbigny's roundeared bat or Whitethroated round-eared bat Microbat
Rhinolophus creaghi Creagh s horseshoe bat Microbat
Ok, What Did You Find? Opsins: S and M/L S1-4 S4-5 M/L2-4 M/L4-6 S1-4 S4-5 M/L2-4 M/L4-6
Ok, What Did You Find? Opsins: S and M/L S1-4 S4-5 M/L2-4 M/L4-6 S1-4 S4-5 M/L2-4 M/L4-6
Ok, What Did You Find? Opsins: S and M/L S1-4 S4-5 M/L2-4 M/L4-6 S1-4 S4-5 M/L2-4 M/L4-6
Sequencing Blue opsin exons 4-5: Goeldi's marmoset Long-haired Rousette Black Bonneted bat Interphotoreceptor Retinoid-Binding Protein: Black Bonneted bat
Example Sequence
BLAST Off Results were compared with NCBI s database of known gene sequences This helps to confirm gene identity and, through similarity, allows relationships to be inferred
Goeldi s Marmoset
Black Bonneted Bat
Long-haired Rousette
Black Bonneted Bat IRBP Brazilian Free- Tailed Bat
Bolivian Squirrel Monkey Goeldi's marmoset Maximum Likelihood Tree HKY85 Model of Evolution -ln 3948.87513 With ambiguous regions 100 Black Bonneted Bat Long-Haired Rousette 100 Crab-Eating Macaque 98 100 Chimpanzee Gorilla 0.05 substitutions/site
Bolivian Squirrel Monkey Goeldi's marmoset Maximum Likelihood Tree HKY85 Model of Evolution -ln 3736.964 Without ambiguous regions 100 Black Bonneted Bat Long-Haired Rousette 100 Crab-Eating Macaque 100 Chimpanzee 100 0.05 substitutions/site Gorilla
Maximum Parsimony Tree 100 Replicates Bootstrap Values With Ambiguous Regions 100 100 Goeldi's marmoset Weeper Capuchin Mantled Howler Squirrel monkey Bolivian Squirrel Monkey 100 80 Human 51 Chimpanzee 67 Pygmy Chimpanzee 97 88 Gorilla Crab-eating Macaque Orangutan 98 Black Bonneted Bat 69 Long-Haired Rousette 100 Humpback Whale Pilot Whale Harp Seal
Maximum Likelihood Tree HKY85 Model of Evolution -ln 5108.33452 With ambiguous regions Goeldi's marmoset Squirrel Monkey Bolivian Squirrel Monkey Weeper Capuchin Mantled Howler Human Chimpanzee Pygmy Chimpanzee Gorilla Crab-eating Macaque Orangutan Black Bonneted Bat Long-Haired Rousette Humpback Whale Pilot Whale 0.05 substitutions/site Harp Seal
Conclusions Bat sequences attained are opsins and IRBP IRBP is functional, opsins are not High similarity to pseudogenes, large divergence Expected for microbats, but not mega Needs to be investigated further High divergence due to loss of function, nocturnal life or distant relationships More individuals, species, and genes need to be tested with more stringent primers
Acknowledgements UREKA program with funding from SFI Dr. Emma Teeling, the bat queen Alisha Goodbla, PCR Master John and Allan Dr. Stefano Mariani and his scanner Gareth Dyke and Julia Sigwart Fellow UREKA students and their mentors