How to hide in the sea ) Transparency Mirroring Cryptic coloration Counter-illumination

Transparency (jellies, etc.) Light passing through is about the same as the downwelling ambient Reflection and refraction from animal exceeds upwelling light

Cryptic coloration and mirrored surfaces mirrored fish White ventral surface is best under all situations Dorsal surface never perfectly cryptic

Diagram showing how a keel on the ventral surface of an animal eliminates he dark shadow normally cast downward by an unkeeled animal. The presence of the shadow means that an animal living deeper and looking upward would see the unkeeled nektonic animal due to the shadow, but would not see the keeled animal, which would blend into the lighted background. (Modified from Y. G. Aleyev, Nekton, Dr. W. Junk BV., Reproduced by permission of Kluwer Academic Publishers.)

Fast swimming fishes with warm bodies have streamlined bodies and heavily muscled tails with crescent shaped caudal fins. The ones illustrated here are three tunas: the bluefin (a), the skipjack (b), and the wahoo (c), and a mackerel shark, the mako (d).

Typical adaptations of epipelagic fishes.

Three views of a tuna showing the adaptations necessary for fast movement. (A) Front view. (B) Side view. (C) Top view.

Life in the mesopelagic and deep sea is linked to plankton and light intensity in the water.

Animal Adaptations in the Mesopelagic Mid-water Realm Vertical Migrations of Animals Diel (daily) vertical migrations: cycle is coupled to downwelling light (the ‘Zeitgeber’ or ‘time-giver’)

Three kinds of migrations... DAY NIGHT Z (m) New moon Full moon Nocturnal migrations

DAY NIGHT Z (m) Twilight migrations Three kinds of migrations...

DAY NIGHT Z (m) Reverse migrations

Why vertically migrate?  Reduce light-dependent mortality  Metabolic advantage Light damage avoidance Minimize horizontal advection (use deep counter-currents) Prevent over-grazing Maximize genetic exchange Minimize competition

Adaptations of Vertical migrators like the Lanternfish on left and non-migrators like dragonfish on right. 1.Well developed muscles and bones 2.Swim bladder of air or fat 3.Withstand extreme temperature changes

O 2 Minimum Layer

Torres et al. Reduced with depth

Measured at 10 C Tuna Vent fish Fish activity decreases with depth

Theusen and Childress Only visual predators show this decrease in activity

Oxygen binding capacity of OMZ animals

Summary of Low oxygen adaptations Reduced oxygen consumption with depth Results in reduced athleticism Oxygen binding high

Mesopelagic Crustaceans

Photophores Specialized light structures that make “living light” or bioluminescence.

Typical Mesopelagic Fish

Rectangular midwater trawls used to collect mesopelagic organisms. Net has remote control to open only at certain depths.

As more shallow fish are over fished other deeper fish like this black scabbord fish are being caught. This is one way that we have learned more about fish from deeper depths.

Large hinged jaw that can accommodate large prey Viperfish

33 Viperfish Chauliodus macouni (depth m)

Many non-migrators like this Rattrap Fish eat the more muscular migrators because they have more protein!

Tubular eyes like this midwater bristlemouth fish, with acute (great) upward vision.

Midwater predators rely on sight. Midwater prey cannot afford energy cost of swimming fast, spines, or scales so they… Camouflage with countershading (dark on top, light bottom or sides) Transparency = see through them (in upper mesopelagic – jellies, shrimp, etc) Reduce the silhouette (bioluminescence on bottom) With blue-green light they control! Coloration and Body Shape

Photophores on lower or ventral surface makes the silhouettes hard to see when they are viewed through water. Value of Photophores

Living light is used for… 1)Counterillumination to mask silhouette 2)Escape from Predators with confusing light 3)Attract or see prey 4)Communication and Courtship Bioluminescence

Summary

Typical Characteristics of deep-sea pelagic fish

Tremendous pressure of 1,000 atmospheres or 14,700 psi 1.Tough to visit and bring fish back alive 2.Metabolism affected by pressure 3.Molecular adaptations to allow enzymes to work under extreme pressures.

Finding mates is a problem in the dark So animals use… 1.Bioluminescence 2.Chemical signals 3.Hermaphroditism 4.Male Parasitism Sex in the Deep Sea

Benthic Fish

Reduced eyes or are completely blind (Live in complete darkness) Huge mouths to eat prey larger than themselves (Scarce food -less than 5% from higher waters) No vertical migrations to richer surface waters (small to reduce metabolic demands; flabby muscles, weak skeletons, no scales, and poorly developed respiratory, circulatory, and nervous systems) Nature of Life in the Deep Sea Benthos

Slow Pace (Save Energy) Low Temp and High Pressure (slow pace) Live Long and Large (up to 100 years) Produce fewer larger eggs (a lot of food for larva) Dominated by Deposit Feeders (eat marine snow) Nature of Life in the Deep Sea Benthos

Marine Snow Particles

Discarded feeding houses

Marine Snow Particles ‘Comets’

Aggregates

Contribution of Marine Snow to Vertical Flux Narrow window of particle sizes which are large enough to sink but numerous enough to be widely distributed ,000 (um) Snow Bodies Cells

cellchain plankton feces aggregates Willie X 1-10 m 50 m 100 m 2000 m Available to water column processes

Reduction in Vertical Flux over Depth 1 23 The Martin Curve Martin and Knauer % losses by 300 m 75% losses by 500 m 90% losses by 1500 m

Explanations for the Shape of the Martin Curve Bacterial decomposition = remineralization of Carbon Cryptic swimmer distribution Smaller, slower sinking particles at depth

Composition of Marine Snow Once living material (detrital) that is large enough to be seen by the unaided eye. Described first by Suzuki and Kato (1955) High C:N makes for poor food quality. Senescent phytoplankton Feeding webs (e.g., pteropods, larvaceans) Fecal pellets Zooplankton molts

Formation of Marine Snow Type A: Mucous feeding webs are discarded individually. Type B: Smaller particles aggregate into larger, faster sinking particles. Aggregates

Extreme Deposition: Food Falls Rare events (not recorded in traps) Deposit large amounts of high quality organic materials to sea floor (low C:N) Rapid sinking, reach 1000s of meters in few days Large bodies that remain intact (whales, fish, macroalgae, etc)

Amount of nutrients at different depths is controlled by photosynthesis, respiration, and the sinking of organic particles. Nutrients are recycled but sink!

Deep water originates at the cold surface at the poles. Cold water sinks and spreads out along the bottom.

63 Sound Scatterers Who are they? Fishes (e.g., myctophids or lanternfish) Crustaceans (copepods, krill) Jellies (siphonophores, medusae)

64 Animal Adaptations in the Mesopelagic Food Oxygen Light

65 Mesopelagic

66 Animal Adaptations in the Mesopelagic Mid-water Realm Bioluminescence Production of light by organisms through chemical reaction (kind of chemiluminescence). (Know the difference between bioluminescence and fluorescence and phosphorescence) ALL PHYLA of animals have luminescent members

67 Adaptations for Bioluminescence Decoys: Long duration, broad wavelength, intense False sense of size: Peripherally located, broad wavelength Blind/confuse predator: Bright flash, broad wavelength Blink and Run: Bright flash or luminescent cloud Lure Prey: located near or in mouth Burglar alarm: bright, long duration How does duration, intensity and wavelength serve an adaptation?

68 Barreleye Macropinna microstoma (Depth m)

69 Headlightfish Diaphus theta (depth 0-800m) Northern Pearleye Benthalbella dentata (depth m)

70 Robust Blacksmelt Bathylagus milleri (depth m)

71

72 Animal Adaptations in the Bathypelagic Mid-water Realm Conservation of Energy Blob sculpin(b) Psychrolutes phrictus Loss of muscularity and skeletal mass Low protein content in muscle Reduced eyesight

73 Eelpout

74 Giant grenadier Albatrossia pectoralis Gigantism