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Visually guided swimming in box jellyfish: A study of swimming behaviour in response to visual stimuli

Petie, Ronald LU (2012)
Abstract (Swedish)
Popular Abstract in Swedish

Att förstå mekanismen som bestämmer djurs beteende är inte lätt. Genom att studera beteendet hos enklare djur kan man göra det mer förståeligt. Om man vill studera ljusstyrt beteende är det enklaste djuret att använda en manet från karibiska området vid namn Tripedalia cystophora. Denna manet har ögon som liknar människans ögon. De lever i vattnet i mangroveskogar och äter små kräftdjur som samlas i stora mängder mellan mangroveträdens rötter. Maneterna använder sina ögon för att undvika krockar med trädrötterna, för att hitta tillbaka till mangroveträden och för att hitta de ställen där bytesdjuren samlas. Maneterna simmar med en slags jetdrift. Varje gång en manet tömmer sin simklocka (kropp)... (More)
Popular Abstract in Swedish

Att förstå mekanismen som bestämmer djurs beteende är inte lätt. Genom att studera beteendet hos enklare djur kan man göra det mer förståeligt. Om man vill studera ljusstyrt beteende är det enklaste djuret att använda en manet från karibiska området vid namn Tripedalia cystophora. Denna manet har ögon som liknar människans ögon. De lever i vattnet i mangroveskogar och äter små kräftdjur som samlas i stora mängder mellan mangroveträdens rötter. Maneterna använder sina ögon för att undvika krockar med trädrötterna, för att hitta tillbaka till mangroveträden och för att hitta de ställen där bytesdjuren samlas. Maneterna simmar med en slags jetdrift. Varje gång en manet tömmer sin simklocka (kropp) orsakar detta en vattenstråle som driver maneten framåt.

I den här avhandlingen har jag utforskat hur maneten Tripedalia cystophora använder sina ögon för att styra sitt simbeteende. För att hitta svaret placerades maneterna i ett litet akvarium där väggarna kunde tändas och släckas. Då ljuset tändes och släcktes i olika kombinationer observerades hur simklockan drog ihop sig. Jag undersökte också riktningen av simklockans öppning vid ihopdragningen av klockan, där öpningens riktning bestämmer simriktningen hos maneten.

Jag fann att då ljusintensiteten sänktes i ett begränsat område svarade maneterna genom att rikta klockans öppning mot mitten av det mörka området. Det gjorde att de simmade iväg från mörkret. Om ljusintensiteten runtom maneten sänktes var öppningen centrerad, vilket gjorde att maneten simmade rakt fram. Beteendet blev starkare när den mörka delen blev mörkare och då ljusintensiteten sänktes snabbt. Maneterna ökade också simhastigheten genom att öka simpulsfrekvensen av simklockan. Det innebar att deras kropp pulserade snabbare. Pulsfrekvensen av simklockan bestäms av fyra rytmgeneratorer som genom att samarbeta bestämmer simrytmen hos maneten.

Mekanismen beskriven ovan representerar troligen grunden till förmågan hos maneterna att undvika föremål i vattnet. (Less)
Abstract
Most animals use eyes to guide their behaviour. Analysing, and understanding, visually guided behaviours gets more complicated the more advanced the animal gets. Box jellyfish provide a relatively simple system for understanding visually guided behaviours. They have a limited nervous system, but they also possess a visual system that is quite impressive for a jellyfish. Box jellyfish have 24 eyes of four different eye types. For directional swimming the animals need to set swim speed and direction. In our investigations we measured how visual stimulation affected factors controlling swim speed and swim direction. As a model species we used the well studied box jellyfish species Tripedalia cystophora.

In paper I we measured the... (More)
Most animals use eyes to guide their behaviour. Analysing, and understanding, visually guided behaviours gets more complicated the more advanced the animal gets. Box jellyfish provide a relatively simple system for understanding visually guided behaviours. They have a limited nervous system, but they also possess a visual system that is quite impressive for a jellyfish. Box jellyfish have 24 eyes of four different eye types. For directional swimming the animals need to set swim speed and direction. In our investigations we measured how visual stimulation affected factors controlling swim speed and swim direction. As a model species we used the well studied box jellyfish species Tripedalia cystophora.

In paper I we measured the pattern of bell movement of a tethered jellyfish in response to a simple visual stimulus. We found that animals responded to a darkening of a quarter of the underwater scene by increasing swim pulse frequency, producing off-centred openings in the bell and delaying contraction in one of the four sides of the bell. The increase in swim pulse frequency would make the animal swim faster, while the off-centred opening in the bell made the animal turn.

In paper II we investigated how the four pacemakers that regulate the swim pulse frequency interact. We compared experimental data with the outcome of several different models and found a good fit to experimental data with a model where the pacemakers fully reset each other, in combination with a hyper-polarising pacemaker. All models underestimated the proportion of long inter-pulse intervals, implying the existence of an additional control mechanism.

In paper III we measured the shape of the opening of the bell in response to different patterns of visual stimulation. We showed that the direction of the opening in the bell matches the pattern of stimulation. The opening of the bell was directed towards the middle of the dark area. When light intensity decreased all around the animal, centred openings in the bell where found.

In paper IV we measured bell contraction patterns in response to increases in contrast or rate of light intensity decrease of the stimulus. Upon stimulation animals increased their swim pulse frequency. They slightly increased bell contraction, while the duration of the contraction phase of the swim pulse was not altered. Swim pulses where also more consistently directed at higher contrasts and higher rates of light-intensity decrease. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Michael, Dickinson, University of Washington, Department of Biology
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Vision, steering, swimming, behaviour, box jellyfish, Cubozoa, Tripedalia cystophora, biomechanics
pages
91 pages
publisher
Department of Biology, Lund University
defense location
Blå Hallen, Sölvegatan 37, Lund.
defense date
2012-09-14 10:00
ISBN
978-91-7473-358-7
language
English
LU publication?
yes
id
94db4e7f-eb0f-45dd-947d-d7ce767f850d (old id 3021626)
date added to LUP
2012-08-23 09:41:35
date last changed
2016-09-19 08:45:10
@misc{94db4e7f-eb0f-45dd-947d-d7ce767f850d,
  abstract     = {Most animals use eyes to guide their behaviour. Analysing, and understanding, visually guided behaviours gets more complicated the more advanced the animal gets. Box jellyfish provide a relatively simple system for understanding visually guided behaviours. They have a limited nervous system, but they also possess a visual system that is quite impressive for a jellyfish. Box jellyfish have 24 eyes of four different eye types. For directional swimming the animals need to set swim speed and direction. In our investigations we measured how visual stimulation affected factors controlling swim speed and swim direction. As a model species we used the well studied box jellyfish species Tripedalia cystophora.<br/><br>
In paper I we measured the pattern of bell movement of a tethered jellyfish in response to a simple visual stimulus. We found that animals responded to a darkening of a quarter of the underwater scene by increasing swim pulse frequency, producing off-centred openings in the bell and delaying contraction in one of the four sides of the bell. The increase in swim pulse frequency would make the animal swim faster, while the off-centred opening in the bell made the animal turn.<br/><br>
In paper II we investigated how the four pacemakers that regulate the swim pulse frequency interact. We compared experimental data with the outcome of several different models and found a good fit to experimental data with a model where the pacemakers fully reset each other, in combination with a hyper-polarising pacemaker. All models underestimated the proportion of long inter-pulse intervals, implying the existence of an additional control mechanism.<br/><br>
In paper III we measured the shape of the opening of the bell in response to different patterns of visual stimulation. We showed that the direction of the opening in the bell matches the pattern of stimulation. The opening of the bell was directed towards the middle of the dark area. When light intensity decreased all around the animal, centred openings in the bell where found. <br/><br>
In paper IV we measured bell contraction patterns in response to increases in contrast or rate of light intensity decrease of the stimulus. Upon stimulation animals increased their swim pulse frequency. They slightly increased bell contraction, while the duration of the contraction phase of the swim pulse was not altered. Swim pulses where also more consistently directed at higher contrasts and higher rates of light-intensity decrease.},
  author       = {Petie, Ronald},
  isbn         = {978-91-7473-358-7},
  keyword      = {Vision,steering,swimming,behaviour,box jellyfish,Cubozoa,Tripedalia cystophora,biomechanics},
  language     = {eng},
  pages        = {91},
  publisher    = {ARRAY(0x91e0ce8)},
  title        = {Visually guided swimming in box jellyfish: A study of swimming behaviour in response to visual stimuli},
  year         = {2012},
}