Nick Roberts Flashcards
Enright et al 2015
spectral sensitivity of zebrafish shifted when treated with TH, more red shifted as A2 produced.
HPLC and transcriptome analysis showed Difference between TH and WT fish was enzyme cyp27c1. TH needed for switch on enzyme.
Porter et al, 2012
Reconstructed phylogenetic relationships among 889 opesin sequences.
4 major groups - R type, C type, Cnidops and Group 4 (neuropsins, peropsins and photoisomerases)
R type most closely related to Group 4. C type close to Cnidops.
Opsins cannot be classified based on G protein binding.
Temple et al, 2010
Archer fish Toxotes chatareus
measures absorbance of cell types in different areas of retina using microspectrophotometry.
Samples taken from different locations on retina, baseline measurement from tissues w/o photoreceptors next to retina. Absorbance measures of 303 photoreceptors.
dissection in formaldehyde and mounted for cell counts.
Dorsal - average 16000 cells/mm, peak sensitivith 454-570nm.
Ventronasal - average 22500 cells/mm. 502-620nm. aligned with projection of snells window onto retina.
Rennison et al 2011
guppy retina
Guppys have 9 opsins:
4 LWS genes, expressed in dorsal retina,
2 middle WS - RH2-1, RH2-2 - ventral retina and 2 SWS1 UV sensitive - expressed throughout retina.
- All expressed simultaneously
- also many ‘key sites’, where AA substitutions affect spectral sensitivity.
- Females inspect males from elevated position in water column.
- Population variation in which colours are most attractive, as in cichlids.
- Sampled from lab population descended from venezuelan pop. removed all RNA from retina –> cDNA. clones 2 sense and 8 antisense opsin probes. cryosectioned eyes.
- beauty may be in the eye of the beholder, as ‘brightness’ depends on the spectral sensitivity of the females cones matching the WL of male spots.
Cuthill et al, 2005
2 predictions: patterns on outline are effective in promoting concealment; highly contrasting colours enhance this effect.
- 10 replicte block each of 75-84 targets. used spectrophotometry and modelling of blue tits cone photoreceptors to match colour of bark.
- in order to have a role in predation, must meet 2 conditions. Distribution of colour patterns matches that predicted by theory; distributions reduce detectability of prey to predators.
- found all bicoloured treatment survived better than monochrome, and inward patterns enhanced camouflage
variability in visual pigments in UW species
There is most data on vision in species in aphotic zone and least in epipelagic.
Cone complements/set may change upon migration to different environments, eg fish in dark conditions may just have rods but shallower add on number of cones. Unsure of depths where each one becomes useless. 10-50m, fish tend to have 2 cones, one with porphyropsin.
89species deep sea fish investigated, most have purely rod retinas w rhodopsins.
fish which use counter lighting and mirror camouflage mainly have 1 retinal rod, whereas deep sea fish have 2 rod classes w diff pigments.
deep sea crustacean Rimicaris exoculata - 350 degree volcanic vents, use rhodopsin in cephalothorax to detect black body radiation from hot water. water is hot enough to give light at 600nm.
migrating fish - pollack 420 peak to 460 when fully grown.
variability in visual pigments in UW species
Lythgoe and Partridge 1989
There is most data on vision in species in aphotic zone and least in epipelagic.
Cone complements/set may change upon migration to different environments, eg fish in dark conditions may just have rods but shallower add on number of cones. Unsure of depths where each one becomes useless. 10-50m, fish tend to have 2 cones, one with porphyropsin.
89species deep sea fish investigated, most have purely rod retinas w rhodopsins.
fish which use counter lighting and mirror camouflage mainly have 1 retinal rod, whereas deep sea fish have 2 rod classes w diff pigments.
deep sea crustacean Rimicaris exoculata - 350 degree volcanic vents, use rhodopsin in cephalothorax to detect black body radiation from hot water. water is hot enough to give light at 600nm.
migrating fish - pollack 420 peak to 460 when fully grown. Eels blue shift when reach breeding grounds.
Labhart and Meyer
DRA
DRA in field crickets, honeybees, desert ants and house flies.
to be pol sensitive ommatidia must have: 2sets of homochroatic (G, B or UV, to avoid interference with other visual signals such as colour) strongly pol sensitive orthoganally arranged photoreceptors; anatomical characteristic changes in ommatidial structure, seen by histological sections.
prehaps anatomy arose polyphyletically as differences among insects.
pol sensitive photoreceptors have rhabdoms shorter - reduces self screening, and wider - widens sensitivity. microvilli oriented at 90 degrees btw rhabdomeres. microvilli misaligned in non pol sens photoreceptors.
Parkyn and Hawryshya 1992
measured spike activity of axons from optic nerve, when pol filter rotated, and tested whether size/dev stage affected pol sensitivity in rainbow trout.
Only pol sens if UV present. upon smoltification , change in photoreceptor mosaic occurs and decreases no. of UV cones.
Rods - no pol sensitivity
White light - bimodal response, max 90 and 180 degrees, minima at 30 and 60.
MWS and LWS cones unimodal response.
UV - 3 peaked response
Sashar and Hanlon, 1998
In pol light, squid detect zooplankton at a distance of 70% greater than non-polarised.
Tested pol active tissues in 20 zooplankton species using standard linear polarisation microscopy and retardance measuring pol light microscope. strong retardance up to 25% in rhabdomeric photoreceptors and muscle fibres.
Loligo pealei, squid, preferred transparent and pol active targets, when tank lit from behind with linear polarising filter.
Sweeny et al 2003
what may have contributed to radiation of heliconius into deep forest habitats?
Blue iridescence of H. cydno is 90% polarised
mate choice experiments to see if involved in mate selection.
displayed female wings under filters for 10mins and counted males flight to them.
1. optically anisotropic - colourless depolarising screen (removes pol)
2. pol neutral, isotropic.
Sig less male approached to depolarised wings than control.
Also repeated with H. melpomene, which had no sig differnce btw filter groups.
