WR Vision (13, 14, 15)

Question 1

Mariana trench snail fish

Answer 1

Wang, K., et al. (2019). Morphology and genome of a snailfish from the Mariana Trench provide insights into deep-sea adaptation, Nature Ecology & Evolution, 3, pp.823-833.

Question 2

Wang, K., et al. (2019). Morphology and genome of a snailfish from the Mariana Trench provide insights into deep-sea adaptation, Nature Ecology & Evolution, 3, pp.823-833.

The study

Answer 2

The study:

• Looks at snailfish Pseudoliparis swirei which resides in the Mariana trench below 6000m
• Describe the genome and morphology of the snailfish and provide insights in how they have evolved to survive and thrive in the hadal zone.
• They were able to distinguish this as a new species due to the morphological differences compared with other species, and through DNA barcoding.

Question 3

Wang, K., et al. (2019). Morphology and genome of a snailfish from the Mariana Trench provide insights into deep-sea adaptation, Nature Ecology & Evolution, 3, pp.823-833

Problems with living in the deep sea and snailfish adaptations

Answer 3

Problems with living in the deep sea:

• Darkness
• Limited food resources
• Low temperatures
• Hypoxia
• High hydrostatic pressure. Increases by 10atm per 100m of depth.

Snailfish adaptations

• Enlarged liver, stomach and eggs
• Thinner muscles
• Completely ossified skeleton

Results

Question 4

Snailfish study - results

Wang, K., et al. (2019). Morphology and genome of a snailfish from the Mariana Trench provide insights into deep-sea adaptation, Nature Ecology & Evolution, 3, pp.823-833.

Answer 4

Results

• The snailfish in question diverged from a similar species around 20.22million years ago.
• The snailfish has a low rate of mutation across the genome but has high protein evolution. This is advantageous as it can control metabolic rate and generation times easily. Female snailfish produce few eggs, but the ones they produce are large.
• They found that the snailfishes skull is not completely closed- to allow equalization of the pressure inside its head with the environmental pressure. This is due to a premature termination of an osteocalcin gene (bone building gene).
• The fish did not respond to any lights emitted by the deep-sea lander, meaning that the fish has lost important photoreceptor genes.
• Its skin is void of any colour and is completely transparent, due to the loss of the pigmentation gene, mc1r.

This study only sampled 5 snailfish across 3 sites in the marianas trench therefore some of the information on gene mutations etc may be hard to generalise for all individuals of the species.

Question 5

Lanternfish bioluminescence

Answer 5

de Busserolles, F. and Marshall, N.J., 2017. Seeing in the deep-sea: visual adaptations in lanternfishes. Philosophical Transactions of the Royal Society B: Biological Sciences, 372(1717), p.20160070.

Review paper

· It looks at the current knowledge of the vision of the lanternfish.

· Lanternfish produce bioluminescent light using the luciferin-luciferase reaction.

· They use bioluminescence for a multitude of things including mating, avoiding predators and communication.

Question 6

de Busserolles, F. and Marshall, N.J., 2017. Seeing in the deep-sea: visual adaptations in lanternfishes. Philosophical Transactions of the Royal Society B: Biological Sciences, 372(1717), p.20160070.

Review paper

visual adaptations

Answer 6

Vision adaptations

· Their adaptations maximise light collection and extend their visual field.

· They have large eyes but this is highly diverse within the family.

· They have a high density of rods in their eyes, the highest number of any vertebrate. This increases the vision in the mesopelagic zone where downwelling light is scarce.

· They have retinal pigments specifically tuned to pick up the blue-green lights which are characteristic of living in the mesopelagic zone. (34).

· Some species have a yellow pigment in their eye allowing thir to be an increased contrast between the green and yellow lights, therefore allowing them to detect bioluminescent light more easily.

Question 7

Flashlight fish paper

Answer 7

Hellinger, J., Jägers, P., Donner, M., Sutt, F., Mark, M.D., Senen, B., Tollrian, R. and Herlitze, S., 2017. The flashlight fish Anomalops katoptron uses bioluminescent light to detect prey in the dark. PloS one, 12(2), p.e0170489.

The study

· Explores how the flashlight fish utilises bioluminescence to hunt and detect planktonic prey.

· Their light organ increases and decreases depending on the ambient light.

· The light organ located under their eye contains symbiotic bacteria which allows the bioluminescence to occur.

Question 8

Flashlight fish key points

Answer 8

Key points

· The fish live in reefs and forage in the dark in schools of up to 200 individuals.

· There is a bioluminescent light produced that is reflected off the back of the light organ. This light is blue-green.

· The lights blink and the rate at which they blink changes depending on the time of day and whether the fish is foraging for zooplankton.

· The blink rate increased from 13 blinks/min during the day to 89 blinks/min at night.

· An increase in light emission by decreasing blink frequency and increasing the time which the light organ was being used was successfully used to detect and catch prey. This is because the immediate area around them is illuminated therefore allowing them to see the prey.

Question 9

Red and black importance in the deep sea - study and paper

Answer 9

• In the deep sea colour is relatively similar across most species found there, and most of them are either red or black.
• The colours of deep sea organisms serve more for crypsis, with bioluminescence allowing communication and signalling.
• Deep-sea organisms need to be cryptic when viewed under ambient light and bioluminescent light.
• For a benthic species their ideal colour is something that matches the substrate which they are settled upon. For pelagic species their ideal colour differs depending on if it wants to be cryptic under ambient light or cryptic under bioluminescent light.
• This study used the reflectance of several deep sea species and then used this value to calculate the contrast of the animals colour against a spacelight or against its substrate.
• · Found that the guts of pelagic cnidarians and ctenophores were minimal at blue-green wavelengths of light. This is important as it reduces their chance of detection by bioluminescent light in the water column.
• · Reflectance of the pelagic species was so low that they would all appear as silhouettes.

Question 10

Lecture 14 Vision and Light

Warrant and Locket 2003- Vision in the deep sea (review)

Answer 10

Greatest variation in eye design is found in the mesopelagic zone, where dim down-welling daylight and bio- luminescent point sources may be visible simultaneously’.

· ‘Some mesopelagic eyes rely on spatial and temporal summation to increase sensitivity to a dim extended scene, while others sacrifice this sensitivity to localise pinpoints of bright bioluminescence’

· Other eyes have retinal regions separately specialised for each type of light.

· In fishes, the retinal ganglion cells are also frequently arranged in a horizontal visual streak, an adaptation for viewing the wide flat horizon of the sea floor, and all animals living there.

· Silvering

· Opaque mesopelagic animals can make themselves appear transparent by having bodies covered in silvery mirrors. hatchetfishes, have vertically flattened silvery sides – created by multiple stacks of guanine crystal sheets – reflect almost 100% of the incident light. have dark. chromatophores that disperse pigment over the mirrors at night

· ‘To be perfectly transparent, an animal must have the same transmission and reflection characteristics as the surrounding water (i.e. the same refractive index).’

· Transparency

· Pelagic amphipod Phronima sedentaria reduces opaque area by having a tiny pigmented retina (retina not transparency).

· Hatchetfish

· matching transparency-Two small displaced photophores, one pointing into each eye of the hatchetfish, ensure that the counterillumination has the same intensity as the daylight. By adjusting the intensity of bioluminescence produced by the ventral photophores so that it matches the intensity of down-welling daylight…. Adjusts with depth

· Tubular eyes-searching for illuminated downwelling silhouettes of prey, have dorsally positioned tubular eyesto catch remnants of light from above….Whereas telescope fish Gigantura chuni, that chase prey swimming directly ahead, have their tubular eyes directed frontally.

Question 11

Haygood and Distel 1988 -Bioluminescent symbionts of flashlight fishes and deep-sea anglerfishes form unique lineages related to the genus Vibrio

Answer 11

· Anomalopidae (flashlight fishes are tropical reef fishes that have large suborbital light organs)

· Suborder Ceratioidei (deep-sea anglerfishes) contains 11 families. In nine of these, females have a bioluminescent lure- that contains bacterial symbionts that belong to photobacterium species

· Non symbiotic luminous bacteria belong to Vibrio species

· Anomalopssymbiont differs greatly from the Photoblepharon palpebratus symbionts- both species of flashlight fish- even though the fish were collected in the same location. Differences in symbiont between species- indicates specific association where symbiont has diverged in parallel with host.

Question 12

Denton et al 1985- The roles of filters in the photophores of oceanic animals and their relation to vision in the oceanic environment

Answer 12

· Study on ventral photophores of 3 deep sea fishes

· Light filters within pigments lie between light generating tissue and the external

· Hatchetfish Argyropelecus aculeatus and the mirrorbelly Opisthoproctus grimaldi have photophores that generate light that is a relatively poor spectral match for the ambient submarine daylight while the light emitted into the sea, after passing through the filters, is a good match. Use filters to get a good colour match

· Lanternfish (Diaphus rafinesquii) also shows a good ‘colour match’ is brought about not by passing the light through a filter containing pigments but by reflecting the light into the sea by a blue mirror.

· Malacosteus niger has two light emitting organs, one emits blue luminescence and one emits red light from a suborbital (below/behind the eye) photophore.

· The red light generated inside the photophore is largely absorbed by a coloured which transmits only a band of light of wavelengths around 700 nm.

· Organisms cannot see this produced light but Malacosteus can detect prey illuminated by this red light over short distances.