Transcript Spirula

Chapter 18
Life in the Ocean’s Depths
© 2006 Thomson-Brooks Cole
Key Concepts
• Several thousand species have
adaptations that allow them to survive
in the deep-sea environment.
• The lack of light has had the most
impact in shaping the organisms of the
deep sea.
• Many deep-sea animals exhibit
bioluminescence, which helps them
find mates and prey in their dark
environment.
© 2006 Thomson-Brooks Cole
Key Concepts
• Deep-sea fishes display a variety of
adaptations such as sharp teeth, large
mouths, and huge stomachs that help
them survive in a habitat with limited
food.
• The environmental conditions of the
deep sea have been relatively stable
for more than 100 million years, and
as a result, several organisms have
changed very little from when they
first evolved.
© 2006 Thomson-Brooks Cole
Key Concepts
• Benthic communities consist of sparse
populations that survive on the
minimal food available in their
environment.
• Thriving marine communities that
depend on chemosynthetic bacteria for
primary production exist on the ocean
floor around hydrothermal vents.
© 2006 Thomson-Brooks Cole
Survival in the Deep Sea
• The deep sea is an inhospitable place
– frigid temperatures throughout the year
– tremendous pressure
– total darkness
• Conditions have remained stable over
many years
• Some creatures have evolved to
survive in this harsh environment
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Survival in the Deep Sea
• Adaptations to pressure
– fluid pressure within the animal’s tissues
matches the pressure of the seawater
• Adaptations to cold
– nearly all have body temperatures close to
that of the surrounding water
– slow metabolism – slow movement,
growth; less reproduction, longer life
– high density of cold water matches that of
animal’s bodies – they don’t sink
© 2006 Thomson-Brooks Cole
Life in the Dark
• Color in deep-sea organisms
– countershading employed in the disphotic
zone—region of dim light (twilight)
• photophores (light-producing organs) may be
used to make the ventral surface lighter
– many species are bright red or orange
• appear black or gray in dim light
– many are bioluminescent
© 2006 Thomson-Brooks Cole
Life in the Dark
• Roles of bioluminescence
– how bioluminescence works
• a protein called luciferin is combined with
oxygen in the presence of an enzyme called
luciferase and adenosine triphosphate (ATP)
• chemical energy of ATP converted to light
– camouflage
• bioluminescence matches the intensity of
sunlight, and thus contributes to
countershading, in the twilight zone
© 2006 Thomson-Brooks Cole
Life in the Dark
• Roles of bioluminescence (continued)
– mating and species recognition
• identifies the sex of an individual
• allows for identification of species
– attracting prey
• anglerfish and stomiatoids attract prey with
bioluminescent lures
• light may be used to locate prey in the dark
– defense
• deepwater squid and shrimp release clouds of
bioluminescent materials to confuse predators
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Life in the Dark
• Seeing in the dark
– many deep-sea fishes have tubular eyes
containing 2 retinas instead of 1
• 1 retina views distant objects, while the other
views closer objects
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Life in the Dark
• Seeing in the dark
– deep-sea squid have barrel-shaped,
stalked or unequally-sized eyes
– some animals have slightly-functional
eyes or are totally blind, relying on
chemical stimuli instead
© 2006 Thomson-Brooks Cole
Life in the Dark
• Finding mates in the dark
– male becomes a parasite on the female in
some species of anglerfish
• Finding food in the dark
– benthic organisms and scavengers eat
detritus which drifts down from above
– many small fishes and invertebrates
migrate upward at night to feed
– adaptations include large mouths and
expandable stomachs
© 2006 Thomson-Brooks Cole
Life in the Dark
• Finding food in the dark (continued)
– some can eat prey larger than themselves
– stomiatoids have barbels (fleshy
projections) that may be used as lures,
probes or for species recognition
– anglerfishes have a spine used as a fishing
pole, tipped with a luminous lure
© 2006 Thomson-Brooks Cole
Giants of the Deep
• Giant squids
• New species of deepwater squid
– large, unnamed species discovered 1988
– have longer arms than other squid, bent
downward at sharp angles
– exhibit different behaviors
• hide in their ink clouds instead of fleeing
• pairs have been observed attached, towing
each other through the water
© 2006 Thomson-Brooks Cole
Relicts from the Deep
• Spirula
– small molluscs resembling squid and
octopuses with spiral-shaped internal
shells
– similar to belemnites common in the sea
100-50 million years ago
• Vampire squid
– dark-colored, webbing between its arms
– thought to be descendents of an
intermediate organism between squids
and octopuses
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Relicts from the Deep
• Coelacanth
– fish with large, thick scales and fleshy
bundles between its body and fins
– thought to be extinct for 70 million years
until 1 was caught alive in 1938
• Neopilina
– limpet-like mollusc
– thought to be extinct for 350 million years
until 1 was found in 1952
© 2006 Thomson-Brooks Cole
Life on the Sea Bottom
• Benthic communities
– sources of food for benthic organisms
• organic matter rains down from surface waters
and accumulates on the ocean floor
• a large carcass will occasionally drift down
– food chains
• bacteria are consumed by meiofauna (e.g.
foraminiferans and nematodes)
• infauna (e.g. worms, bivalves) eat meiofauna
• deposit feeders and suspension feeders
• predators include fishes, squids, sea stars
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Life on the Sea Bottom
• Benthic communities (communities)
– diversity of benthic organisms of the deep
• low numbers, but high diversity
• ineffective dispersion of young may lead to
isolation, which contributes to speciation
• stable conditions may prevent extinction of
species, so species proliferate
© 2006 Thomson-Brooks Cole
Life on the Sea Bottom
• Vent communities
– self-contained communities that are some
of the most productive in the sea
– formation of vents
• vents form at spreading centers
• seawater seeps down to where it contacts
magma
• water is superheated, and loses some minerals
while it picks up others, such as sulfur, iron,
copper and zinc
© 2006 Thomson-Brooks Cole
Life on the Sea Bottom
• Vent communities (continued)
– types of vents
• white smokers—produce a stream of milky
fluid rich in zinc sulfide; water temperature is
normally less than 300o C
• black smokers—narrow chimneys that emit a
clear water with temperatures of 300o to 450o
C that is rich in copper sulfides (which
precipitate with contact with cold seawater, to
produce the black color)
© 2006 Thomson-Brooks Cole
Life on the Sea Bottom
• Vent communities (continued)
– vent communities
• residents include large clams, mussels,
anemones, barnacles, limpets, crabs, worms
and fishes
• primary producers are chemosynthetic bacteria
• primary consumers filter-feed or graze bacteria
from the water
• clams (Calyptogena), mussels (Bathymodiolus)
and vestimentiferan worms (Riftia) host
symbiotic chemosynthetic bacteria
© 2006 Thomson-Brooks Cole
Life on the Sea Bottom
• Vent communities (continued)
– rise and fall of vent communities
• vents are colonized by organisms shortly after
they are formed
• when geological changes inactivate the vent
(an estimated 20 years later), these organisms
all die
• vent inhabitants are thought to produce large
numbers of larvae which drift to other vent
sites
© 2006 Thomson-Brooks Cole