DEEP-SEA PAGES:
MESOPELAGIC (MIDWATER) and BATHYPELAGIC ANIMALS

By Paul H. Yancey
Whitman College
Updated APR. 2017 from Mar. 2017 DEEP-C cruise
(Evergreen College-MBARI expedition south of Hawai'ian Islands, NSF funding).

Return to my MAIN DEEP-SEA PAGE for details on animal collection; and for TOPIC CONTENTS (or use pull-down menu, below).

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Most of these photos are mine, others are ones I took from the ROV Oceanic Explorer's or Alvin's cameras.

OTHER TOPICS
These are species that we caught off Oregon, California and Hawai'i either as a deep-sea bottom otter trawl rose, or by midwater/pelagic trawls (picture, right). One, the MOCNESS type net, can be opened and closed at specific depths. Some species are MESOPELAGIC (about 200-1000m), while others are from the deeper BATHYPELAGIC zone (below 1000m). Some migrate down into the ABYSSOPELAGIC (below about 3000m, but poorly defined).
  • Pelagic animals are those that live in the open water, not closely associated with the seafloor. [Benthic and benthopelagic (bottom-associated) animals are found on most of my other animal webpages (use the menu, upper right)]. Animals in the deep pelagic--fishes, jellies, shrimp, etc.--must adapt to low food supplies. They eat each other, and/or the detritus falling down from above. Some species are vertical migrators--they migrate to the upper waters at night to eat where there is more food. Animals often have gelatinous tissues and overall very low protein contents, with relatively weak muscles*.
  • Many camouflage their bodies by being transparent, black or red. Red light from the sun does not exist in the midwater twilight as red wavelengths are absorbed (removed) strongly by water (and blue the least, hence the ocean's color). Consequently, most deep-sea animals have lost the ability to see red.
  • Many have have special adaptations to cope with low light levels, such as large eyes and photophores (light-producing organs) to produce bioluminescence for headlights, lures, mating signals, camouflage (counterillumination; see below), confusing prey, confusing predators, and/or "burglar alarm" (light up your predator to attract a higher-level predator to the one after you). About 75% of mesopelagic organisms are bioluminescent. Most bioluminescence is blue, or less commonly green, since blue wavelengths of light, followed by green, travel farthest in water (red light, in contrast, travels the least, its energy being absorbed by water most easily).
See the UCSB Bioluminescence or the KrillOil bioluminescence page for kids for more information on biological light production.
Below: MOCNESS pelagic trawl
mocness
Below: Rare TELESCOPEFISH with forward-focused eyes and bloated stomach (more below)
telescopefish
A. DEEP PELAGIC FISHES -- Oregon/California/Hawai'i
Click here for SQUIDS/OCTOPODS; here for OTHER INVERTEBRATES

Many deep-sea fish have elaborate mechanisms for catching food presumably because it is so infrequent: devices such as those noted above--light lures, large eyes (some focused forward or upward for silhouette detection)--but also huge teeth, and expandable jaws and stomachs that allow them to swallow prey larger than themselves (see examples above and below). The telescopefish is a prime example (see above right and far right-->). To see how it uses its forward-facing tubular eyes, see the MBARI video here.

*Our Fish Research: In the 1980s we found that some midwater fish have buoyant gelatinous layers (see below: gel layer just under skin in the blacksmelt cross-section). They also have very low protein content in muscles. These are probably adaptations to an energy-poor environment, and/or the lack of light, which may make it a waste of energy to have robust muscles for long pursuits or escapes. It also means these are not very good for human consumption.

Our publications
on midwater fish anatomy and biochemistry:
--Siebenaller, J.F., P.H. Yancey (1984). The protein composition of white skeletal muscle from mesopelagic fishes having different water and protein contents. Mar. Biol. 78: 129-137
--Yancey, P.H., R. Lawrence-Berrey, M. D. Douglas (1989). Adaptations in mesopelagic fishes. I. Buoyant glycosaminoglycan layers in species without diel vertical migrations. Mar. Biol. 103: 453-459
--Yancey, P.H., T. Kulongoski, M.D. Usibelli, R. Lawrence-Berrey, A. Pedersen (1992). Adaptations in mesopelagic fishes. II. Protein contents of various muscles and actomyosin contents and structure of swimming muscle. Comp. Biochem. Physiol. 103B: 691-697

TO FIND almost any FISH SPECIES in the world, go to FISHBASE.
MORE DETAILS on DEEP SEA FISH can be found at Jeff Drazen's U. Hawai'i site

Thanks to Ruben Pohl for the FISH depth ranges listed first as peak abundance, followed by record depths. Other fish depths from FISHBASE (above).

Above, below: Telescopefish Gigantura spp.
telescopefish whole.telescopefish eyes
Above: stomach bloated with prey; tubular forward-facing eyes
Below: contents of the bloated stomach!
telescopefish stomach

Stomiidae: Dragonfish, Viperfish
viperfish
Pacific Viperfish
Chauliodus macouni
( mainly 250-950m; max 4231m?). Note slot in upper jaw for large lower teeth!
dragonfish
Longfin Dragonfish
Tactostoma macropus
( 50-200m at night; 300-1600m during day; max 2000m?). Note light organ below eye
dragonfish1
Stoplight Loosejaw Dragonfish
Malacosteus spp.(niger?)
Note the red and blue --> headlights
, also loose jaw, hinged skull-->.
See below for details
(500 - 3886 m)
dragonfishlight
dragonfishgape
dragonfish2
Barbeled Dragonfish

above and -->
Note ventral photophores for counterillumination
and light lure on chin barble
dragonteeth
dragonfishlure2
dragonlure3
Dragon- and viperfish typically have no scales; some have jaws that open wide, due to a hinged skull, and a large expandable stomach, all for swallowing large prey.  Most have a line of ventral (belly) light organs (photophores) for counterillumination (light is emitted that matches the faint blue sunlight from above, making the body hard to see from below). Some have a photophore on a long fin-ray (dorsal or ventral) that serves as a lure.
Most have a blue headlight, but some dragonfish also have have headlights below their eyes that make red light, which they use to illuminate prey! In 1998, R. H. Douglas et al. reported (Nature 4-June-98, p423; and New Scientist 6-June-98, p16) that these dragonfish have chlorophyll in their retinas that allow them to see red light. Recall (above) that there is no red sunlight in the deep, and most animals cannot see red. Chlorophyll allows the dragonfish's red light to be virtually invisible to all but itself (a "sniperscope").

Viperfish often have teeth so big, they need a slot in their jaw/skull (see Chauliodis photo) so they don't cause self-injury! From submersibles they have been seen hanging motionless with their lure over their mouths, waiting for prey (see Randall and Farrell book below ).


Lophiiformes: Anglerfish
huge angler
Black Seadevil Anglerfish
Melanocetus
(
100 - 4500 m?)
.
More views of Black seadevil

Small live angler making blue light (seen here reflected in glass dish in ship's lab)!
male angler
Male anglerfish

Anglerfish with lure mimicking a small fish

Anglerfish (females only in the family Ceratiidae) have a glowing lure (often shaped like an animal) dangling on a fin ray over their huge jaws. The lure contains symbiotic bacteria, whose blue light is thought to be controlled by the fish's blood supply.
Deep-sea males in the Ceratiidae family are somewhat like parasites. They are tiny, and use nasal organs to find a female in the dark. He will attach with his teeth to the female's flank, merging his blood vessels into a permanent union. Most of his organs atrophy except the (enlarged) testes.
There are other non-deep groups and also deep-sea families besides Ceratiidae, including the Seadevils (Melanocetidae) which do not reproduce this way.

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Myctophidae: Lanternfish
DiaphusDiaphus2
Headlightfish-- Diaphus (theta?)
( 0-200 at night; 300-1000 in day; max 1687m?)
Note ventral photophores (signaling/counterillumination)
Also note large parasitic copepod on top!
Diaphus lights
Face view: high and low-beam headlight organs between eyes
flashlight
Headlight or flashlight myctophid with massive headlights. See right-->
Diaphus (effulgens?)
flashlight2 lampfish
Northern Lampfish
Stenobrachius leucopsarus
(mainly 31-1189m;
max 3400m?)
Lanternfish: Headlightfish, Lampfish (mostly Myctophidae family) are found in all oceans, and have photophores all along their ventral (belly) sides, and some have headlight ones on their heads. Many migrate up to the surface at night then down during the day.

Other Deep Pelagic Fish with Special Eyes
barreleye
Barreleye
Macropinna microstoma
( mainly 500-1000m)
barreleye2
Barreleye,
top view
barreleye new
barreleyebottom
Different species
with flat belly (Hawai'i)
tubeeye new
tubeeye closetubeeye front
Tube-eye fish
Stylephorus chordatus
(300 - 800 m)
sabertooth new
evermanella closeevernanella teeth
Sabertooth fish
Evermanella, possibly indica
(500 - 800 m)
pearleye
Northern
Pearleye
Benthalbella dentata
98-3400 m
Barreleyes (Opisthoproctidae) are some of the few fish known to eat gelatinous midwater animals such as salps (below). Barreleyes have their huge eyes focused to look straight up for silhouttes, but can also rotate them to look forward! In 2009, MBARI [Monterey Bay Aquarium Research Inst.] obtained the first-ever video of these, revealing that they have a bizarre-looking clear dome over their eyes! [Usually lost in trawl nets.] Following that, Steven Colbert of Comedy Central TV did a hilarious R-rated news story on this weird fish. Tube-Eye or Thread-tail fish (Stylephoridae) have a very long tail fin-ray, forward focused eyes, are (sub)tropical deep, but migrate up at night. They are thought to expand their mouths to suck in copepods. Sabertooth fish (Evermanellidae) have upward-focusing eyes as well,  large teeth and expandable stomachs (note swollen belly above in top picture). Pearleyes (Scopelarchidae) have tubular eyes with "pearl" bulge that may allow sideways vision also.
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Miscellaneous Other Deep Pelagic Fish
fangtooth.JPG
Fangtooth
Anoplogaster
cornuta

(mainly 300-2000m; larvae 0-200m)
bigscale
bigscale2
Crested Bigscale
Poromitra crassiceps
(Primary depth 300-3200m)
bigscale3
bigscale head
Another Bigscale
(Hawai'i)
daggertooth
Daggertooth
Anotopterus nikparini
( 500-2700m; young rise to 20m ?)
snipe-eel2
snipe-eel3
Snipe Eels from Hawai'i
witcheel
Witch eel
Facciolella sp.
(935m?)
Calif.
snipe eel
Snipe eel
Nemichthys scolopaceus
(mainly 50-1500m)
Oregon
Fangtooths are unable to close their mouths due to their teeth. They tend to have more robust muscles than other deep-sea fish.
Melamphaidae--Bigscale fish or ridgeheads have large scales often lost during capture. Eaten by diving mammals and larger fish. Daggertooths lack dorsal fins and are known to eat salmon. Snipe Eels, Witch eels use their elongated jaws to catch shrimp, perhaps by entangling shrimp antennae.
gonato2
gonato3
gonato1
Gonatostomids from Hawai'i
cyclothone2
cyclothone3
Cyclothone Bristlemouths
 from Hawai'i (worldwide, Earth's most common vertebrate!)

Gulper Eel

Photo: Pelican eel By Alexei Orlov - [1], CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=4862914
whalefish
Whalefish
Note enlarged lateral line (pits in picture) for detecting movement in the dark (down to 3500m)
blacksmelt.fish gel
Stout Blacksmelt and "gel" layer we discovered
Pseudobathylagus (Bathylagus) milleri
(200-1400m; max. 6600m?)
blacksmelt
Slender Blacksmelt
Bathylagus pacificus
(0-7700 m! usually 600-800m)
Gonatostomid fish include bristlemouths, with those in the Cyclothone genus being the most common verterbrates on earth (in the trillions!). They have wide mouths, and may swim with them open to engulf prey
Gulper Eels (Saccopharyngiformes) have huge mouths, jaws and stomachs to swallow almost anything Cetomimidae or whalefishes: in addition to large lateral lines, 1 species can exhibit forms so different (male, female, age) that different body types were once classified as separate species. Blacksmelts (Bathylagidae): eat gelatinous animals. We found that much of their bodies are  quite gelatinous as well (see cross-section picture above). One report places the stout blacksmelt down to 6600m, in the abyssopelagic.
hatchetfish1 hatchetfish2
Hatchetfish
Argyropelecus?
Sternoptyx? (50 to 1,500)
hatchetfishbabyhatchetfishlarva
Hatchetfish baby, juvenile
hatchetfish1
Hatchetfish's large mouth
hatchetfish1
Hatchetfish's ventral (belly) light organs
lepto1
lepto1
Leptocephali (leptocepthalus, singular) from Hawai'i mesopelagic
Hatchetfish: have ventral (belly) light organs to provide counterillumination. They are also very narrow (laterally compressed) like a knife blade, which also makes them hard to see by a predator looking up into the light. Their large eyes are pointed up to look for silhouettes of prey above them. See more here. Leptocephali are migratory larval stages of various eels, which often dive into the deep sea. They look so different from adults that they were once classed as separate species

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B. DEEP PELAGIC INVERTEBRATES--Oregon, California, Hawai'i
  Range of capture ~200 - 3000m. Note terms: PLANKTON refers to organisms at the mercy of currents, even if they can swim; NEKTON refers to strong swimmers that can outdo most currents (mainly vertebrates and cephalopods). * = unidentified. Zooplankton here are from Hawai'i.
Depths from Wikipedia or SEALIFEBASE.
Zooplankton: Cnidarian Jellies, Ctenophores (Comb Jellies), Salps, Worms, Crustaceans 
oddjelly
misc jelliesmisc jellies2
hat jellieshat jellies2
bathyctena1bathyctena2
Golf-tee jelly
Aegina citrea?
(Hydromedusa)
(3 - 2800 m)
Helmet jelly Periphylla -- note dome.
(Scyphozoan)
(down to 7000m!)
Atolla wagon-wheel
jellies
(Scyphozoan), noted
for burglar alarm bioluminescence
(~500-4000m)
Miscellaneous
jellies
"Mexican hat"
jelly
Bathyctena ctenophore
(comb jelly)

(1000 - 3500 m)

Salps: Urochordates related to sea squirts and in the same phylum as vertebrates (Chordata). A jet-engine body which pumps water in one end, extracts food, and blows wastes out the opposite end. Colonies can be large.
Pyrosomes ('fire bodies'): close relatives of salps, intensely bioluminescent colonies, often gigantic!
I don't know
what this is!
Polychaete (segmented worm) with red eyes --unidentified*
Nemertean
(ribbon worm) --unidentified*
Chaetognaths
(arrow worms)*
ammonia shrimp
 
phronima1phronima2
smallamphredoddamphipodredamphipod
larvalcrustacean
Notostomus Shrimp with sac of ammonium ions for flotation.
Purple shrimp*
Transparent giant-eyed Cystisoma amphipod. Right picture is close-up of red retina. It's oriented up to look for silhouettes (124 m to 1320m)
Phronima amphipod. Did it inspire the Alien of the Alien movies? She is inside a salp that she hollowed out as a nursery for her eggs.
Miscellaneous amphipods
Unidentified larval crustacean. Note eyestalks.
*=unidentified
Nektonic CEPHALOPODS; see Mollusc Page for Benthic, Benthopelagic Species (e.g., Dumbo Octopods)
vampire squid

walkingsquidwalkingsquid2
eyelightsquideyelightsquid2
VAMPIRE SQUID Vampyroteuthis infernalis
These squid-like animals (actually their own category of cephalopod, not quite a true squid) have 2 photophores (light organs) on their back ends, and more on their arm tips; soft hooks instead of suckers; and they "cloak" themselves by folding their black umbrella-like tentacles over their bodies leaving only the glowing back end visible. (Monterey)
(600 - 900m?)
Chiroteuthis calyx Squid with intact feeding arms.
These mesopelagic squid have 2 long feeding arms with photophores (light organs) on their tips. (Monterey)
Teuthowenia-type "cockatoo" Cranchiid squid = Glass Squids (seen by us from Alvin sub at 880m; Oregon)
More Glass Squids
with close-up of eye for one (Hawai'i)

Odd glass squid swimming and "walking" in ship's lab tank (Hawai'i)
Squid with light organs along eye
(Hawai'i)
radiolaria-covered ceph


Tiny transparent cephalopod covered in radiolaria!
Bolitaenid - type tiny transparent octopod grasping prey. Bolitaenids can rapidly modulate their transparency
Another tiny transparent octopod with yellow chromatophores (probably Bolitaenid).
Another small transparent octopod 

 


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FOR MORE DETAILS, see these WEB SITES and REFERENCES

A nice overview of common and interesting deepsea animals (with some of my pictures) can be found at Sea and Sky.
For more information and pictures of deepsea fishes beyond the internet, see
-- Scientific American
, July 1995, and
-- TIME
magazine Aug. 14, 1995;
-- Deep-Sea Fishes by D.J. Randall & A.P. Farrell, Academic Press, 1997
--For an article on countries that have been catching midwater fish for food, see New Scientist, Nov. 8, 1997
The Monterey Bay Aquarium Deepsea page has excellent pictures and descriptions of deep-sea animals