Transcript Class Malacostraca

Class Malacostraca
Kate Atkinson, Ruby Berin, Niki Geller, Maddie Tanda
Characteristics
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Two chambered stomach
Centralized nervous system
Usually eight legs (first two sometimes pinchers)
Three part body (Head, thorax, and abdomen)
o Usually the head consists of 5 segments
o Thorax consists of 5-8
o Abdomen consists of 6
They usually have paired eyes and they are usually stalked
o A stalked eye means that the eye is held away from the body, giving them a
wider range of vision
Appendages hanging from the abdomen called pleopods, or swimmerets
o Used for swimming, brooding eggs, catching food, and (in isopods) gills
Some have a carapace
What makes them unique?
● The most numerous and most successful of the four major classes of
Crustacea
● Their members constitute more than two-thirds of all living crustacean
species
● They exhibit the greatest range of size (less than one millimetre, or 0.04
inch, to a limb spread of more than three metres, or 10 feet) and the
greatest diversity of body form
● They are abundant in all permanent waters of the world
● They have developed specialized organelles sensitive to odors, sounds,
vibrations, and physical contact and added more appendages to the
mouthpart
● This lead to the terrestrial malacostraca to make better use of the
environment around them
Body Plan: External
● Hard exoskeletons, composed of chitin and
calcareous material
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Carapace
Soft at the joints for movement
● Jointed appendages, which are specialized
in certain species for different functions
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Claws, pincers, etc.
Body Plan: Internal
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Hemocoel (blood-filled coelom)
Striated muscles (with flexors/extensors)
Gas exchange through thinner cuticle or gills
“Open” circulatory system (no separation of blood by vessels)
Excretory organs in antennae regulate composition of body fluid
Supraesophageal ganglia (control eyes/antennae) and
subesophageal ganglia (control mouth, appendages, etc) connect
● Molting (process of making a larger cuticle); more common in
juveniles
● Ecdysis (shedding of the cuticle)
Isopoda
● Can live in a wide variety of habitats, some being marine (and can live
on the ocean floor), others can be terrestrial (in moist environments)
● Vary in size, ranging from 0.3 mm to 50 cm in length
● Have two pairs of antennae with one pair feeling along the ground
● Female Isopods carry eggs in a pouch called a “marsupium”
● Isopods eat fungi, decaying plant matter, plant growth, and dead
animal matter
● Certain species roll into a ball to protect themselves from predators
like ants, spiders, toads, and frogs
● Over 10,000 species of isopods worldwide
Armadillidium vulgare: Pill bug
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They aren’t bugs, they are terrestrial
crustaceans related to shrimp
They molt 4 or 5 times in their
lifetime
On rare occasions you may find a
bright blue or purple roly poly
then it is known to be sick, but it
isn’t harmful to humans
Females can reproduce without a
male by a process called
parthenogenesis
Deto echinata: Horned Isopod
● Known as a horned isopod because of the
long curved 'horns’ that extend from the
rear of each thoracic segment, longer in
males
● Usually found with kelp and other drift
algae on rocky shores
● Feeds on washed-up algae, carrion or live
prey
● Eggs emerge from brood pouches as adults
● Can reach up to 30 mm in length
Bathynomus giganteus: Giant
Isopod
● Gigantism in the species
is the result of the pressure
from it’s deep sea habitat, on
the sea floor
● 7 ½ to 14 inches in length as
an adult
● Can survive for up to four
years without food
Amphipoda
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9,500 species
No carapace, laterally compressed bodies
Have different types of legs, unlike isopods
Are found in a wide variety of aquatic
environments (from freshwater to that with
twice the salinity of the ocean)
● No metamorphosis
Talitrus Saltator: Sandhopper
● Stay buried underneath the
sand during the daytime, and
emerge at night in order to
feed on vegetation
● Were given their name
because of their ability to hop
when disturbed
● One antenna is always much
longer and thicker than the
other
Pariambus typicus
● Require water of higher
salinity
● Can grow to a size of 7
mm
● Males exhibit a pair of
vestigial lobes (not shown)
● Found mainly in the North
Seas
Hyperia galba: Big-eye Amphipod
● They live in jellyfish, just
under the bell
● Live off of the jellyfish
eggs
● Found in the ocean’s
pelagic zone
Euphausiacea
● Scientists suspect that the total weight of all the
Antarctic Krill in the world is more than the total
weight of all humans on earth​
● The number of krill is declining, and this is due to
global warming and a large krill fishing industry​
● Can be found in water as deep as 2,000m​
● Filter feeders that eat diatoms
Euphausiacea (continued)
● Divided into two families: ​
1. Bentheuphausiidae: consists only of Bentheuphausia
amblyops, a deep-water krill
2. Euphausiidae: Other 89 known krill species.
Bioluminescent ​
● Range in length from 8-70mm, the largest at 14cm​
● Have a hard, calcified exoskeleton with three segments: the
cephalon, thorax, and abdomen​
● Head has 5 segments, thorax has 8, tail has 6 (each
segment with a pair of appendages)
Bentheuphausia Amblyops
● Found in the southern
part of the North
Atlantic Ocean
● Only species in its
family
● Are a deep red color
with white gills
● Live in the deep sea
Euphausia Superba: Antarctic Krill
● Probably the most
abundant animal species
on earth in terms of mass
● Can live up to 6 years
● Can gather in groups with
densities reaching 10,000
krill per cubic meter
● Bioluminescent
Euphausia Crystallorophias: Ice Krill
● Lives more south
than any other krill
species
● Have been found in
water as deep as
4,000 meters
● Food source for fish, whales, and penguins
Decapoda
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Typically have ten legs (five pairs of legs)
Most species have the first pair modified as claws
In front of the main pair of legs there are three appendages that are used in
handling food
On top of the head there are compound eyes that are located on eyestalks
Most are predators or scavengers but some feed on algae and the land crabs will
eat fruits and leaves
Most have gills that project upward from near the base of the thoracic appendages
and are enclosed within a protective gill chamber
Reproductive organs are found at the dorsal part of the thorax
o In males there is a single pair of testes and the sperm ducts open at the fifth
pair of legs (at the base)
o Females oviducts open to the exterior at the base of the third pair of legs
All decapods have the ability to regenerate
Stenorhynchus seticornis: Arrow Crab
● Prey on feather duster worms
and bristle worms and pick
through detritus but will also
catch slow-moving fish
● Three to six centimeters
● They shed their exoskeleton and
the new skin hardens with calcium
carbonate (obtained by the
water and by eating the old shell)
Procambarus alleni: Blue Crayfish
● They are pretty
aggressive towards each
other
● They range from seven
to eight inches
● They like to have lots of
hiding places around
them because they are
boring
Panulirus interruptus: California Spiny Lobster
● They do not have any claws
● To protect themselves they
use the spines along their
bodies
● They make loud sounds with
their antennae to scare off
predators
● They may shed 40 times
before they reach the harvest
size
Hymenocera picta: Harlequin Shrimp
● They go out to hunt
mainly at night because
they are shy
● Usually will stay in a
pair with a male and
a female
● Adults eat sea urchins