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Marine Arthropods
Invertebrates
 Arthropods
 Characteristics of Phylum:
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About 1 million species known, mostly marine
Most marine species are in a group of arthropods called crustaceans
About 75% of all animals on earth are arthropods
Chitin exoskeleton- hard, but light and moderately flexible
Since the skeleton is external, an arthropod must shed the shell to be
able to grow – this process is called molting. There is a soft new shell
underneath.
Jointed appendages
Many divided into sections called head, thorax and abdomen
Specialized segmentation- segments combined for specific functions
Specialized eye & sensory organs- wide angle of vision
Invertebrates
 Arthropods
 Characteristics of phylum:
– Specialized respiratory structures, gills, used for gas
exchange
– Some are filter feeders, some scavengers, others
carnivores
Invertebrates
 Types of Marine Arthropods:
 Crustaceans
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68,000 species
2 pairs antennae
Gills for respiration
Head and thorax fused into a single unit called a
cephalothorax; entire external body is called the carapace
 Large array of appendages specialized for different
functions; ex: pinchers on crabs, swimmerettes on the
underside of shrimp hold developing eggs, etc.
 Types of crustaceans – copepods, barnacles, amphipods,
isopods, crabs, shrimp, lobsters, etc.
Characteristics of Crustacea
 External
 a. Appendages
 2 prs of antennae: 1st homologous to antennae of insects &
myriapods, 2nd homologous to chelicerae
 3rd pair of head appendages are mandibles
 Biramous - terminal segment with endopod and exopod
 b. Tagmata
 Head and trunk (often divided into thorax and abdomen)
 A carapace may cover dorsal and lateral surfaces
 c. Exoskeleton
 chitin may be calcified in larger species
Characteristics of Crustacea
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Feeding and Digestion
a. Nearly all are suspension filter-feeders
b. Larger species predator/scavengers
c. Appendages specialized for cutting, tearing, collecting
d. Foregut enlarged into cardiac and pyloric stomach
e. Midgut bears two digestive glands (hepatopancreas)
comprised of highly branched, blind canals
secrete enzymes
absorb nutrients
store glycogen and fat
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Gas Exchange, Circulation, and Excretion
a. Respiration
All Crustaceans have gills
May be within thoracic cavity or on appendages
b. Circulatory System
Heart --> dorsal vessel --> sinuses --> gills -->pericardial sinus -->
ostia in heart
 Respiratory proteins (hemocyanin) in blood of larger species
 c. Excretion
 Excretory organs near antennae (antennal glands) or maxillae
(maxillary glands)
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Nervous and Sensory Structures
a. CNS is typical for arthropods:
dorsal brain, paired ventral nerve cord, ganglia
b. Eyes of two types
median simple eye (naupliar - from nauplius larvae)
compound eyes - ommatidia (25 to 14,000)
c. Prioprioceptors and statocysts
in soft tissues between segments
single pair at base of 1st antennae
d. Sensory hairs for mechano- and chemoreception
Phylum Arthropoda
 Class Crustacea
 Subclass Malacostraca
 Order Decapoda
 Order Amphipoda
 Order Isopoda
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Subclass Branchiopoda
Subclass Ostracoda
Subclass Copepoda
Subclass Cirripedia
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Subclass Malacostraca
"Soft Shell"
Over half (>22,000 spp.) of Crustacea
Typically 14 segments: 8 thorax, 6 abdomen
First 1-3 thoracic are forward - maxillipeds
Abdominal appendages called pleopods
 1st pair often used in mating
 6th pair is turned backward for swimming (uropods)
Guess which crustcean we’re talking
about first????
 http://www.youtube.com/watch?v=4rT5fYMfEUc
 That’s right! SHRIMP!
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Subclass Malacostraca: Order Decapoda ("Ten Legs")
10,000 species - crabs, shrimp, lobster, crayfish
Commercially and ecologically important
Mostly marine, crayfish common freshwater, some
intertidal crabs are "semi-terrestrial"
 3 prs maxillipeds, 5 prs legs (1st pr often chelate)
 Gills in branchial chamber enclosed by carapace
 Carry eggs on pleopods (swimmerets) beneath body
photo
Shrimp
Brine shrimp
 Who knows an interesting fact about these?
Ever heard of
“Sea Monkeys”?
SEA MONKEYS!!!!
No, really…….
Sea Monkey Video
 http://www.youtube.com/watch?v=Vc85AjH3zWA
How do they do that?????
 http://www.seamonkeysrule.info/amazingfacts.htm
Pistol Shrimp
 500 species
 All pistol shrimp have one (Or sometimes two) oversized
claw that create a cavitation bubble as it snaps shut. This
bubble, very briefly reaches temperatures approaching
that of the sun, about 4700 degrees Celsius. A loud
"popping" noise is created as well.
 Despite being less than an inch long, the creatures can
emit an astonishing 218 decibels - louder than a gunshot.
BBC Pistol Shrimp
 http://www.youtube.com/watch?v=XC6I8iPiHT8
 Goby and shrimp
 http://www.youtube.com/watch?v=FEslHsv-HF4
Peppermint shrimp
Shrimp life cycle
Shrimp eggs
 Shrimp eggs are tiny, almost invisible particles
released deep in Gulf waters to float in the water
column, providing food for zooplankton and
incidental nutrition primarily for filter feeders ranging
from rays and sharks to mollusks.
Nauplius Larva and Protozoea Larva
 Larvae develop from floating fertilized eggs, growing and
molting through many of each of these stages over a twoor three-week period.
 They cannot swim or control their movements.
 They feed on nanoplankton, zooplankton and
phytoplankton (green algae, copepods and diatoms) as
well as suspended detritus, while small fishes and filter
feeders consume some of them.
Mysis Larva
 Maturing larvae in the mysis stage are carried towards
shore by flood tides and wind-driven currents, continuing
to feed on zooplankton and phytoplankton. A shrimp larva
at this life stage is large enough in size for some juvenile
fish to see and hunt. Its niche is more noticeable and it is
more aware of its environment. Mysis larvae seem to
respond to light by moving away from it — that is down in
the water column to avoid predators – although they do
not yet have swimming appendages.
Postlarva
 Currents and incoming tides carry the maturing
crustacean into brackish (mixture of salt and fresh
water) estuarine waters. Over a 4-6 week period, the
individuals begin to look like shrimp and to forage or
graze like shrimp, clinging to the bottom most of the
time. They develop swimming and walking legs.
Juveniles
 Small juveniles prefer shallow salty water along the
edges of marshes, where plants provide both cover
and detritus, and where microorganisms thrive in the
soft bottom. Small juvenile shrimp are food for
juvenile fishes also living in the estuary such as
southern flounder, spotted seatrout, red drum,
inshore lizard fish, Atlantic croaker and pinfish.
Adult
 Move back to the sea. Out in the Gulf once more, the
adult shrimp continues to grow in size on the sea’s
bottom as an opportunistic omnivore, and its niche at
this stage is primarily as food for many. It lives in deep
water, 60-500 feet below the sea’s surface. when
there is a sharp increase in the water column’s
temperature the females will spawn, producing
thousands of eggs to begin the cycle again.
Shrimp anatomy
Shrimp or Crayfish observation
 Uropod- The sixth and last pair of abdominal appendages of
lobsters and related crustaceans, forming part of the tail fan.
 Telson- the terminal segment of the body of an arthropod
 Rostrum- the often spinelike anterior median prolongation of
the carapace of a crustacean
 Pleopod- an abdominal limb of a crustacean
 Maxillipeds- any of the crustacean appendages that comprise
the first pair or first three pairs situated next behind the maxillae
 Carapace- a bony or chitinous case or shield covering the back or
part of the back of an animal
 Antennae-
Crayfish
Crayfish life cycle
How are lobster and crayfish
different
 http://animals.howstuffworks.com/marinelife/crayfish-info.htm
Decapod video 3 min
 http://www.youtube.com/watch?v=0_HGZESgbjs
Lobster
B 52’s Rock Lobster!!!!!
 http://www.youtube.com/watch?v=Oh5J33KAaqw
 Lobsters are carnivores (meat-eaters). Most lobsters are
nocturnal (most active at night). They are predators that
eat crabs, clams, worms, snails, mussels, flounder, and
other lobsters
 Many animals eat lobsters, including fish (especially cod),
octopi, other lobsters, and people.
 Lobsters continue to grow throughout their lives. The
biggest lobster caught weighed over 44 pounds (20 kg).
Lobsters may live to be 100 years old
Largest Lobster
 The largest American lobster was caught off of Nova
Scotia, and weighed 44 pounds, 6 ounces and was 3
feet, 6 inches long.
 1977
Lobster facts
 Lobsters and other crustaceans inhabit all the world’s
major oceans. Although lobsters can be found
worldwide, different types of lobster choose different
areas in which to live. Many lobsters live in shallow
water in the coastal areas around islands. One group
of lobsters, called deep-sea lobsters, lives in the cold,
deep sea.
 On its antennae, legs, carapace, and tail, a lobster has
tiny, hairlike receptors that can detect specific
chemical molecules in the environment, which help
the lobster to identify and locate food. The lobster
crawls over the bottom of the sea, eating dead and
living fish, starfish, clams, and other animals and
seaweed. It grinds its food with six pairs of jaws. The
food is then further ground and mixed with digestive
juices in the stomach, which contains toothlike
grinding organs.
 Much of the information a lobster gets about its
surroundings is gathered by millions of tiny hairlike sensors
on its antennae, mouthparts, legs, and shell. Some of these
sensors “sniff” chemicals that help lobsters locate and
taste food.
 Others warn lobsters of predators or alert them to
potential mates.A lobster also has special organs located
at the base of its antennules, as the shorter pair of
antennae are called. These organs are pits that are lined
with tiny bristles. As a lobster moves, particles that are
floating within the pits bend the tiny bristles in different
directions. Signals that are sent from these bristles
through the lobster’s nervous system help the lobster
determine its position in its surroundings and keep its
balance.
molting
 The lobster molts, or sheds its shell, frequently while young, less
frequently as it grows. After molting it is helpless against
predators and must hide until the new shell hardens. If it loses a
claw or a leg, the lobster grows a new one.
 To molt, the lobster shrinks the muscles and other tissues in its
limbs by releasing fluid out of the tissues. This lets the lobster
withdraw its appendages from the surrounding shell. Once the
shell cracks, the lobster is able to withdraw its entire body from
its old shell.
 After it is out of its shell, the lobster takes in water to swell its
body to a larger size. The new soft shell can withstand the
pressure from the lobster’s swollen body without cracking. It
takes several weeks for the new shell to harden around the
swollen lobster. Once the new shell is hard, the lobster pushes
the excess water out from its body. It now has a new, roomier
shell to grow into.
 A typical American lobster is 12 inches (30 cm) long
and weighs about 2 pounds (0.9 kg). Some grow to
more than 3 feet (90 cm) long and weigh more than
40 pounds (18 kg). Spiny lobsters are about the same
size as American lobsters. Lobsters can live as long as
100 years
Types of lobster
 There are two kinds of lobsters, and these are
commonly referred to as "clawed" lobsters and
"spiny" lobsters, or rock lobsters. Clawed lobsters
include the American lobster, a well-known marine
species. Clawed lobsters are generally found in cold
waters.
 Spiny lobsters do not have claws, but instead have
long, strong antennae. These lobsters are generally
found in warm water.
American Lobster “clawed”
Spiny Lobster- NO CLAWS
 American lobsters thrive in the cool waters of the
North Atlantic Ocean. These lobsters inhabit sandy,
muddy, and rocky areas of the ocean floor from
Virginia in the United States to Newfoundland and
Labrador in Canada. Spiny and slipper lobsters are
found in warm waters throughout the world. Spiny
lobsters live in coral reefs, on rock ledges, and in
crevices. Slipper lobsters are usually found in muddy
or sandy places.
Lobster reproduction
 The female American lobster carries fertilized eggs on the
underside of its abdomen until the eggs are ready to hatch.
The eggs are covered by a sticky cement that hardens and
holds them in place. Eggs of the spiny lobster are released
to float in the ocean shortly after they have been fertilized.
The newly hatched lobsters do not resemble the adults for
several weeks, during which time they go through various
stages of development.
 Lobsters mature at four or five years of age. Females,
depending on their size, produce 3,000 to 100,000 eggs at
one time.
Lobster life cycle
Male or female???
 How do you tell the difference between a male and
female lobster? Look under its tail. On the underside
of its tail, a lobster has swimmerets, which are used
to help the lobster swim and in mating. The male has
a modified pair of swimmerets
 http://www.youtube.com/watch?v=eJY-IDyrFXs
Male or female????
Lobster reproduction video 1:09
 http://www.youtube.com/watch?v=Y3nkJMaWaB4
 http://www.youtube.com/watch?v=h6nhOChpMck
What is a lobster “MARCH”
 To protect themselves from predators, fish swim in schools.
Birds fly in flocks. And lobsters “march.” Predators often have a
difficult time capturing prey traveling in such groups.
 During a lobster march, dozens of spiny lobsters walk together
in long rows, like ants or soldiers. The lobsters walk so close
together that the antennae of one lobster may touch the tail of
the lobster in front of it.
 In the Caribbean Sea, lobster marches are often observed after a
storm. At these times, the lobsters are usually marching out to
deeper water. Some people believe that storms trigger lobster
marches. Scientists, however, are not sure why spiny lobsters
march to other locations. Are they moving to deeper waters to
protect themselves from winter storms? Are they looking for
new breeding grounds? New feeding grounds? The answer
remains a mystery.
Lobster march video
Lobster Video
 Man vs Wild “Lobster Brains” 2:16
 http://www.youtube.com/watch?v=fIIr_Bh4yNs
 Loggerhead vs Lobster
 http://www.youtube.com/watch?v=IIjk84-hxE0
crab
facts
 Abdomen small tucked under compact and typically
broad cephalothorax
 Walk sideways
 Scavengers, predators, some have specialized diets of
seaweeds, organic matter in mud, or coral mucus
Male or female?
 V-shaped abdomen is male
 U-shaped is female
Male or female??
Reproduction
 When male and female crabs reproduce, they assume the
doubler position, which is when the male carries the female.
Mating lasts about five-and-a-half hours, but the crabs may stay
in this position for up to three days afterward. The female stores
the male's sperm on the underside of her abdomen, where it will
be used for two more spawnings that occur within her threeyear lifespan. The females migrate to slightly saltier waters after
mating and attach between 100,000 to two million eggs to the
sperm stored under the abdomen. The incubation period lasts
about two weeks, until the crab larvae hatch and are released
into the ocean to fend for themselves. For the next 40 days, the
crab larvae continue to grow until they reach the adult crab
stage.
Anatomy
Crab examination
 Dungeness Crab
habitat
 Live along rocky shores or sandy beaches
 Marine crabs can live on land for 4-5 days by using the
water they store in their gills
 OR on the ocean floor
 Depends on whether they are crustcean crabs or in
another subclass as we will discuss later
 Marine crabs and terrestrial crabs are NOT the same
Snow crab
Snow Crab
 named for their sweet, delicate, snow-white meat
 Commercial size males are usually older than 8 years
and weigh between 1 and 2 pounds.
King crab
King crab
 most common are Red, Blue, and Golden King crabs
which are generally found in Alaskan waters
 Fishing for king crabs is largely carried out in Alaska
 The king crab usually feeds off of starfish and smaller
crabs, but if they are not available, the king crab will
eat dead animals that may fall into the water
“crabbin”
 http://www.youtube.com/watch?v=Yct7za_P4lA
 http://www.youtube.com/watch?v=roc9VSnoMLM
 http://www.youtube.com/watch?v=deXE2bgzeo4
“crabbin”….
 The most lucrative Alaskan crab fisheries occur in the
fall and winter; the seasons are often short, lasting
less than four weeks. In the Bering Sea specifically,
the two most active months are October and January.
 Each season, approximately 250 crab fishing boats
converge on Dutch Harbor, Alaska, in search of
Alaskan king crab.
 Crab vessels cost several million dollars to build, and
tens of thousands of dollars to operate annually.
 The boats range in size from 40 to 200 feet; each
crew typically consists of one captain and three to
nine deckhands.
“crabbin”……
 Because the sonar used on most fishing boats is downwardpointing, it doesn't detect crabs that are right against or buried
in the ocean floor. Furthermore, since it is impossible to predict
where adult male crabs will be (unless it's spring, which is
mating season), captains must rely on intuition to find the best
crabbing location.
 To catch the crabs, fishermen use 700-pound steel traps ("pots")
baited with ground herring, squid, sardines and cod, which are
dropped 400 feet below the ocean's surface.
 On average, the pots measure 7 feet by 7 feet by 3 feet, and soak
anywhere from five to 24 hours before being hauled back on
deck.
Crab pots- how they work
 http://www.youtube.com/watch?v=UXjmNtldnAI
“crabbin”……..
 In 1980, at the peak of the king crab industry, Alaskan
fisheries produced up to 200,000,000 lb (91,000,000
kg) of crab. However, by 1983, the total size of the
catch had dropped by up to 90% in some places
 At $4.50 per pound (up from $3.90 last year),
fishermen can make between $27 and $45 for each
red king crab they catch. At about $1.70 per pound
(up from $1.50 last year), an average opilio crab can
fetch $1.70 to $5.10.
“crabbin”…….
 Fishermen are allowed to harvest only adult male
crab. All females and juveniles must be thrown back
 If a crab dies in the boat’s holding tank, it emits toxins
that can poison the other crabs; one dead crab has
the potential to wipe out the entire catch
Blue crab
Blue crab
 The blue crab is so named because of its sapphiretinted claws
 Prized by humans for their sweet, tender meat
 Weight: 1 to 2 lbs
 Blue crabs are found in brackish coastal lagoons and
estuaries from Nova Scotia, through the Gulf of
Mexico
 Did you know? Female blue crabs mate only once in
their lives.
Emerald crab
Fiddler Crab
Fiddler crab
 Fiddler crabs are found along sea beaches and brackish
inter-tidal mud flats, lagoons and swamps
 they joust with each other with their huge claw.
 change color be altering the size of cells that contain
pigments, becoming darker in the day and pale again at
night.
 If they have lost legs or claws during their present growth
cycle a new one will be present when they molt. If the
large claw is lost, males will develop one on the opposite
side after their next molt.
Crab Lab
What about hermit crabs???
Hermit crabs
 Hermit crabs are not really classed as crabs due to the
fact that they do not own their own shell
 600 species
 can live as long as 15 years
Coconut crab (interesting but not
marine)
 Largest terrestrial arthropod in the world
 Known for its ability to crack coconuts with its strong
pincers in order to eat the contents
 Also called the robber crab
 FOUR pairs of legs instead of FIVE
 Mostly in Australia and Madagascar
Hermit crab
Other types of Arthropods
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Order Amphipoda
Order Isopoda
Subclass Copepoda
Class Merostomata- Horseshoe Crabs
Class Pycnogonida- sea spiders
 Subclass Malacostraca: Order Amphipoda ("Double
Legs")
 6000 species
 Mostly marine or freshwater, damp terrestrial
 Laterally compressed body, mostly small (< 2 cm)
 Abdomen is not clearly demarcated from thorax
 Large thoracic coxae on legs
 Appear "hunchback"
photo
Beach Hopper
 Common in shore debris. Strong jumpers that spring
about by briskly stretching their curved bodies
Whale lice
 Burrows in skin of whales
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Subclass Malacostraca: Order Isopoda ("Same Legs")
4000 species
Mostly marine benthic, some freshwater
Wood lice are largest group of terrestrial crustaceans
Most are < 2 cm; some quite large (> 40 cm)
Dorso-ventrally flattened
Head is "shield-shaped"
Abdomen same width as thorax
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Subclass Copepoda
"Oar-Footed"
Largest Class of microscopic crustacea
> 8,500 species, marine and freshwater
May be very important in aquatic food webs
Feed mostly on bacteria and phytoplankton
Bulbous head, tapered posteriorly
Trunk segmentation well-developed
Paddle-like appendages
A pair of caudal cerci are distinctive
Compound eyes absent, median naupliar eye
photo
Invertebrates
 Types of Marine Arthropods:
 Horseshoe crabs (only surviving members)- class
Merostomata
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Not true crabs
5 pairs of legs, first pair modified in males for reproduction
Females larger than males
Mating pairs come onto beaches each spring to breed and lay
their eggs in wet sand
 Among the oldest creatures on earth – they have remained
virtually unchanged for millions of years
 They live and borrow in soft sediments, normally near shore
where they feed on other invertebrates and scavenge. Atlantic
and gulf of North America and Southeast Asia
Horseshoe Crab Video
 http://www.youtube.com/watch?v=y6RvgwrzK9c
Invertebrates
 Types of Marine Arthropods
 Sea Spiders:
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Superficially resemble spiders
Four of more pairs of jointed legs
Not insects or true spiders
Possess a mouth and proboscis for feeding
Mainly feed on sea anemones and hydrozoans (they are
voracious predators!)
 More common in cold waters, but can be found worldwide
Arthropod Reproduction
– Male transfers sperm directly to female to ensure
reproductive success
– In some species, female will house eggs for a time
until they are further developed
– Females can store sperm for fertilization at a later
time
– Many arthropods have complex behaviors including
mating rituals