Research in Stickleback Fish. benthic limnetic MALESFEMALES What’s different between the species?
Stickleback Poster
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Introduction Marine threespine sticklebacks, Gasterosteus aculeatus, colonized multiple freshwater lakes in British Columbia post glaciation only 12,000 years ago and subsequently adapted into benthic and limnetic ecological niches, in the process becoming reproductively isolated 1 . This group of recently evolved species offers a natural model to study cognitive evolution in response to selection pressures, as opposed to taxonomic groups that have long complicated evolutionary histories 1 . We investigated the ways in which selection pressures associated with benthic and limnetic environments shaped neuroanatomical evolution. To do this, benthic and limnetic species were sampled from three lakes — Paxton, Priest, and Enos (Fig. 1). We subsequently employed magnetic resonance imaging (MRI) to generate 3D images of intact brains, allowing accurate volumetric measurement of brain regions 2 . Previous studies have established significant cognitive differences between benthic and limnetic sticklebacks, including visual 3 and olfactory perception 4 , spatial learning 5 , and social learning 6 . Results and Discussion • Wild-caught fish from Paxton, Priest, and Enos lakes euthanized with an overdose of MS-222 • Fish fixed in a 10% neutral buffered formalin solution for 72 hours • Fish immersed in a 2% Magnevist (Bayer HealthCare) phosphate- buffered solution for 1 week at 4°C • (Before scanning) Fish suspended in Fluorinert Electronic Liquid FC-43 (3M) • Fish scanned at the Penn State University MRI facility in a vertical 14.1 tesla Agilent imaging system; scan time between 4-8 hours for a resolution of at least 20μm • Images segmented using Avizo® (VSG3D, Burlington, MA, USA, Fig. 2) Figure 1. Marine populations of sticklebacks have invaded multiple postglacial lakes in British Columbia and independently speciated. Because of these historical events we can make comparisons across species. Acknowledgements Selection pressures cause adaptive divergence in brain regions of threespine sticklebacks (Gasterosteus aculeatus) Katelyn Doolittle 1 , Jason Keagy 2 , and Janette W. Boughman 2 1 Baker University and 2 Michigan State University USA Canada Enos Lake Benthic Limnetic Paxton Lake Benthic Limnetic Priest Lake Benthic Limnetic • Benthics, which forage in visually-obscured habitats, will have larger olfactory bulbs and smaller optic tecti than limnetics • The telencephalon, known to be involved in spatial, social, and associative learning, will be larger in benthics which are better at spatial and social learning Figure 2. Anterior side to the right and dorsal side to the top of photograph. (a) Limnetic fish, sagittal section. (b) Benthic fish, sagittal section. (c) Brain region segmentation in Avizo®. Future Directions This research was supported by funding from the Integrative Biology of Social Behavior REU Program (NSF DBI-1153888) as well as an NSF CAREER grant (NSF DEB-0952659) and a grant from the BEACON Center for Evolution in Action (NSF DBI-0939454) to JWB and an EDEN research exchange grant to JK for visiting Penn State’s MRI facility. Special thank to Victoria Braithwaite, Thomas Neuberger, and Cairsty Grassie at Penn State, and Heather Eisthen at MSU. References 1 McKinnon JS, Rundle HD. 2002. Trends Ecol. Evol. 17:480–488. 2 Ullmann JFP, G Cowin, SP Collin. 2010. J. Morphol. 271:1446-1456 3 JW Boughman. 2001. Nature. 411:944-948 4 Rafferty NE, JW Boughman. 2006. Behav. Ecol.17:965-970 5 Odling-Smee LC, JW Boughman, VA Braithewaite. 2008. Behav. Ecol. & Sociobiol. 62: 1935-1945 6 Keagy J, W Lehto, R Minter, S LoPresto, JW Boughman, J. in prep. • There was a significant interaction between lake and species in olfactory bulb (OB) size (F 2,9 =8.13, p=0.010). • In Enos, no difference between species (t 2 =- 0.607, p=0.605) in OB • In Paxton and Priest, benthics had significantly larger OB than limnetics (t 9 =6.08, p0.001) (See Fig. 3) • No significant divergence in telencephalon (t 2 =2.75, p=0.111) or optic tectum (t 2 =0.251, p=0.825) volumes between benthic and limnetic species (See Fig. 4) • Similar results when controlling for body length Olfactory bulb results suggest that selection pressures associated with the environment can play a role in brain evolution. However, not all brain regions appear to be constrained by environmental selection pressures, since we saw no significant divergence in the telencephalon or optic tectum. Figure 3. Comparison of volumes of olfactory bulbs in limnetic and benthic fish between three lakes. Figure 4. Comparison of volumes of the telencephalon and optic tectum between benthic and limnetic species in Paxton Lake. c In addition to the brain regions discussed here, we will continue our study by mapping the cerebellum and whole brain region in benthic and limnetic sticklebacks. Predictions Methods
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Transcript of Stickleback Poster
Introduction
Marine threespine sticklebacks, Gasterosteus aculeatus, colonized multiple freshwater lakes in British Columbia post glaciation only 12,000 years ago and subsequently adapted into benthic and limnetic ecological niches, in the process becoming reproductively isolated1. This group of recently evolved species offers a natural model to study cognitive evolution in response to selection pressures, as opposed to taxonomic groups that have long complicated evolutionary histories1. We investigated the ways in which selection pressures associated with benthic and limnetic environments shaped neuroanatomical evolution. To do this, benthic and limnetic species were sampled from three lakes — Paxton, Priest, and Enos (Fig. 1). We subsequently employed magnetic resonance imaging (MRI) to generate 3D images of intact brains, allowing accurate volumetric measurement of brain regions2. Previous studies have established significant cognitive differences between benthic and limnetic sticklebacks, including visual3 and olfactory perception4, spatial learning5, and social learning6.
Results and Discussion
• Wild-caught fish from Paxton, Priest, and Enos lakes euthanized with an overdose of MS-222
• Fish fixed in a 10% neutral buffered formalin solution for 72 hours
• Fish immersed in a 2% Magnevist (Bayer HealthCare) phosphate-buffered solution for 1 week at 4°C
• (Before scanning) Fish suspended in Fluorinert Electronic Liquid FC-43 (3M)
• Fish scanned at the Penn State University MRI facility in a vertical 14.1 tesla Agilent imaging system; scan time between 4-8 hours for a resolution of at least 20μm
• Images segmented using Avizo® (VSG3D, Burlington, MA, USA, Fig. 2)
Figure 1. Marine populations of sticklebacks have invaded multiple postglacial lakes in British Columbia and independently speciated. Because of these historical events we can make comparisons across species.
Acknowledgements
Selection pressures cause adaptive divergence in brain regions of threespine sticklebacks (Gasterosteus aculeatus)
Katelyn Doolittle1, Jason Keagy2, and Janette W. Boughman2 1Baker University and 2Michigan State University
USA
Canada
Enos LakeBenthic
Limnetic
Paxton Lake
Benthic
Limnetic
Priest LakeBenthic
Limnetic
• Benthics, which forage in visually-obscured habitats, will have larger olfactory bulbs and smaller optic tecti than limnetics
• The telencephalon, known to be involved in spatial, social, and associative learning, will be larger in benthics which are better at spatial and social learning
Figure 2. Anterior side to the right and dorsal side to the top of photograph. (a) Limnetic fish, sagittal section. (b) Benthic fish, sagittal section. (c) Brain region segmentation in Avizo®.
Future Directions
This research was supported by funding from the Integrative Biology of Social Behavior REU Program (NSF DBI-1153888) as well as an NSF CAREER grant (NSF DEB-0952659) and a grant from the BEACON Center for Evolution in Action (NSF DBI-0939454) to JWB and an EDEN research exchange grant to JK for visiting Penn State’s MRI facility. Special thank to Victoria Braithwaite, Thomas Neuberger, and Cairsty Grassie at Penn State, and Heather Eisthen at MSU.
References1McKinnon JS, Rundle HD. 2002. Trends Ecol. Evol. 17:480–488.2Ullmann JFP, G Cowin, SP Collin. 2010. J. Morphol. 271:1446-14563JW Boughman. 2001. Nature. 411:944-9484Rafferty NE, JW Boughman. 2006. Behav. Ecol.17:965-9705Odling-Smee LC, JW Boughman, VA Braithewaite. 2008. Behav. Ecol. & Sociobiol. 62: 1935-1945 6Keagy J, W Lehto, R Minter, S LoPresto, JW Boughman, J. in prep.
• There was a significant interaction between lake and species in olfactory bulb (OB) size (F2,9=8.13, p=0.010).
• In Enos, no difference between species (t2=-0.607, p=0.605) in OB
• In Paxton and Priest, benthics had significantly larger OB than limnetics (t9=6.08, p0.001) (See Fig. 3)
• No significant divergence in telencephalon (t2=2.75, p=0.111) or optic tectum (t2=0.251, p=0.825) volumes between benthic and limnetic species (See Fig. 4)
• Similar results when controlling for body length
Olfactory bulb results suggest that selection pressures associated with the environment can play a role in brain evolution. However, not all brain regions appear to be constrained by environmental selection pressures, since we saw no significant divergence in the telencephalon or optic tectum.
Figure 3. Comparison of volumes of olfactory bulbs in limnetic and benthic fish between three lakes.
Figure 4. Comparison of volumes of the telencephalon and optic tectum between benthic and limnetic species in Paxton Lake.c
In addition to the brain regions discussed here, we will continue our study by mapping the cerebellum and whole brain region in benthic and limnetic sticklebacks.
Predictions
Methods
