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Retinal transcriptome analysis of four owl species: Longeared owl (Asio otus), Short-eared owl (Asio flammeus), Tawny owl (Strix aluco) and Boreal owl (Aegolius funereus)

Höglund, Julia (2017) BINP30 20171
Degree Projects in Bioinformatics
Abstract
Owls (Strigiformes) are birds that typically have crepuscular or nocturnal activity patterns. Even though birds are known to have an exceptional visual system, less is known about specific adaptations to vision in dim conditions. Here, by using retinal transcriptome sequencing, the visual gene pathway has been analyzed in four owl species: Long-eared owl (Asio otus), Short-eared owl (Asio flammeus), Tawny owl (Strix aluco) and Boreal owl (Aegolius funereus). Most birds studied to date have the four cone opsin pigments LWS, RH2, SWS2 and SWS1. For the examined owl species the ultraviolet-/violet-sensitive opsin (SWS1) could not be found in any of the species, the greensensitive opsin (RH2) had a low expression. In addition to this,... (More)
Owls (Strigiformes) are birds that typically have crepuscular or nocturnal activity patterns. Even though birds are known to have an exceptional visual system, less is known about specific adaptations to vision in dim conditions. Here, by using retinal transcriptome sequencing, the visual gene pathway has been analyzed in four owl species: Long-eared owl (Asio otus), Short-eared owl (Asio flammeus), Tawny owl (Strix aluco) and Boreal owl (Aegolius funereus). Most birds studied to date have the four cone opsin pigments LWS, RH2, SWS2 and SWS1. For the examined owl species the ultraviolet-/violet-sensitive opsin (SWS1) could not be found in any of the species, the greensensitive opsin (RH2) had a low expression. In addition to this, positively selected sites was found in genes involved in dim light vision as well as a high expression of phototransduction-activating genes in A. flammeus and A. funereus. The results conform with previous findings of positively selected sites in vision genes as well as loss of the SWS1 gene in owls, which suggest adaptation of the retinal genes to crepuscular and nocturnal activity patterns. (Less)
Popular Abstract
Owl’s ability to see – with or without UV

When we think of owls we often think of majestic creatures that flies without a sound during night looking for prey. They have exceptional hearing and exceptional vision. But what is good vision? What are the best mechanisms for vision in the dark? And can an animal have great color vision and dark vision at the same time?

Most owls are active under dim light conditions such as twilight and even night. A vertebrate eye normally has two types of photoreceptors – rods and cones. When it is bright light, the cones are used, and they are also responsible for color vision. When it is dark, the rods are used and they are practically color blind. Owls, that are active during twilight and night need... (More)
Owl’s ability to see – with or without UV

When we think of owls we often think of majestic creatures that flies without a sound during night looking for prey. They have exceptional hearing and exceptional vision. But what is good vision? What are the best mechanisms for vision in the dark? And can an animal have great color vision and dark vision at the same time?

Most owls are active under dim light conditions such as twilight and even night. A vertebrate eye normally has two types of photoreceptors – rods and cones. When it is bright light, the cones are used, and they are also responsible for color vision. When it is dark, the rods are used and they are practically color blind. Owls, that are active during twilight and night need to have extra sensitive eyes to be able to see as good as possible – even when it is dark.

In this project, I analyzed genes from the retina of four different owls: Long-eared owl (Asio otus), Short-eared owl (Asio flammeus), Tawny owl (Strix aluco) and Boreal owl (Aegolius funereus). Depending on how important a gene is it can be copied (transcribed) in different amounts and by creating a library of these copies (transcripts) in a specific area – in this case the retina – I could find out which genes are expressed the most. Birds normally have four different cone pigments, which means that they can discriminate between more colors than a human, that normally have three. Up until now, nobody has found the gene coding for vision in the UV/violet spectrum in owls, which means that they might not be able to see as many colors as their relatives.

To be able to find out which genes that was expressed I assembled the transcripts to whole genes and then ran them through a database. After I knew which genes I had I estimated the abundance of each gene that is involved in vision. As in previous studies I failed to find the gene coding for the UV/violet cone pigment. I also found very few of the green cone pigment gene. However, I found signs of selection in genes that are active when the rods are used. I also found a quite high expression of genes that activate the visual pathway.

An animal cannot be the best there is at everything they do – there is always a trade-off. To be better at something, it must give up resources from something else. This study suggests that owls have given up parts of their color vision for a better vision in twilight and the dark. It also gives a better understanding for what mechanisms that can be used to adapt to a different life style, such as different activity patterns.

Master’s Degree Project in Bioinformatics 30 credits 2017
Department of Biology, Lund University

Supervisors: Maria Strandh & Almut Kelber
Department of Biology (Less)
Please use this url to cite or link to this publication:
author
Höglund, Julia
supervisor
organization
course
BINP30 20171
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
8925092
date added to LUP
2017-09-08 14:13:28
date last changed
2017-09-08 14:13:28
@misc{8925092,
  abstract     = {Owls (Strigiformes) are birds that typically have crepuscular or nocturnal activity patterns. Even though birds are known to have an exceptional visual system, less is known about specific adaptations to vision in dim conditions. Here, by using retinal transcriptome sequencing, the visual gene pathway has been analyzed in four owl species: Long-eared owl (Asio otus), Short-eared owl (Asio flammeus), Tawny owl (Strix aluco) and Boreal owl (Aegolius funereus). Most birds studied to date have the four cone opsin pigments LWS, RH2, SWS2 and SWS1. For the examined owl species the ultraviolet-/violet-sensitive opsin (SWS1) could not be found in any of the species, the greensensitive opsin (RH2) had a low expression. In addition to this, positively selected sites was found in genes involved in dim light vision as well as a high expression of phototransduction-activating genes in A. flammeus and A. funereus. The results conform with previous findings of positively selected sites in vision genes as well as loss of the SWS1 gene in owls, which suggest adaptation of the retinal genes to crepuscular and nocturnal activity patterns.},
  author       = {Höglund, Julia},
  language     = {eng},
  note         = {Student Paper},
  title        = {Retinal transcriptome analysis of four owl species: Longeared owl (Asio otus), Short-eared owl (Asio flammeus), Tawny owl (Strix aluco) and Boreal owl (Aegolius funereus)},
  year         = {2017},
}