Slide 1
Phylum Arthropoda
HabitatBy: Vishal.N.Rao IX D 9448 Red Group
Arthropods have diversified to live in every habitat imaginable,
from the tropics to the poles, from the bottom of the oceans to the
top of the mountains, both underground and inside other animals and
plants. They are one of only two major animal groups that have
adapted to life in dry environments.
The arthropod subgroup insects is the most species-rich member
of all ecological guilds in land and fresh water environments.
EXTERNAL FEATURESofARTHROPODSBy:-Mayur.S.K 9D 4FEATURES FEATURES
EXOSKELETON Epidermis secretes an external skeleton called the
exoskeleton. Advantages of possessing an exoskeleton:- provides
strong support. provides rigid levers that muscles can attach to
and pull against. offers protection. serves as a barrier to prevent
internal tissues from drying out; important because many arthropods
live on land. serves as a barrier to prevent infection.
STRUCTUREComposed of the polysaccharide chitin and protein
glycoprotein. Outer surface called the epicuticle; contains waxes .
The thicker portion is called the procuticle which is divided
into:- exocuticle . endocuticle. In the exocuticle, the
glycoprotein chains are cross linked; process is called
tanning.
DIAGRAM
Epicuticle Exocuticle Endocuticle ProcuticleEpidermisMOULTING In
arthropods , such asinsects,arachnids andcrustaceans, moulting is
the shedding of theexoskeleton(which is often called itsshell),
typically to let the organism grow. This process is calledecdysis.
It is commonly said thatecdysisis necessary because the exoskeleton
is rigid and cannot grow like skin, but this is simplistic,
ignoring the fact mostArthropodawith soft, flexible skins also
undergo ecdysis. The new exoskeleton is initially soft but hardens
after the moulting of the old exoskeleton.STAGES
EXAMPLE
JOINTED APPENDAGES Exoskeleton divided into a number of plates
andcylinders.
At the junction point between plates and cylinders, the
exoskeleton remains thin and flexible; these are the joints.
Jointed appendages allows arthropods to move efficiently and
quickly. Muscles are integral to arthropod movement; they attach to
the inner side of the exoskeleton; they often function as a lever
system.
Vertebrate jointArthropod joint The evolution of the arthropods
witnessed a reduction in metamerism. The arthropods evolved
modified groups of segments (e.g., segments became lost, some fused
together .The fusion of groups of segments into functional groups
is called tagmatization. In so doing, various appendages on
segments became specialized for functions other than locomotion,
e.g. prey capture, filter feeding, sensing various kinds of
stimuli, gas exchange, copulation, etc.
Arthropod Segmentation: Reduction in Metamerism
SEGMENTATION
RESPIRATORY SYSTEM
17
Arthropods have a wide variety of respiratory systems. Small
species often do not have any, since their high ratio of surface
area to volume enables simple diffusion through the body surface to
supply enough oxygen. Crustacea usually have gills that are
modified appendages (e..g., prawn). Many arachnids have book lungs
(e.g., king crab). Tracheae, systems of branching tunnels that run
from the openings in the body walls, deliver oxygen directly to
individual cells in many insects, myriapods and arachnids (e.g.,
cockroach).17RESPIRATORY SYSTEM (contd.)
Digestive SystemBy: R.C.Vikram Nag IX D 9448 Red Group
Arthropods exhibit every type of feeding mode. They include
carnivores, herbivores, detritus feeders, filter feeders, and
parasites. Typically, paired appendages around the mouth are used
for collecting and handling food and are usually specialized in
accordance with the particular diet of the animal.
In Arthropods, the digestive system is well developed with
distinct organs. Each arthropod has a differentdigestive
systemaccording to their method of feeding and body structure.
Though the digestive tract varies somewhat based on diet of the
animal, typically it has three main regions: a foregut, midgut and
hindgut. Salivary glands are also present.
Both the fore and hindgut are lined with cuticle. Malpighian
tubules empty into the digestive system. Their product is uric
acid. In general, however, the midgut region is the principal site
ofenzymeproduction and absorption of digested food. The enzymes may
pass forward into the front part of the gut and even outside into
the body of the prey, in the case of spiders.
Digestive System of PrawnDigestive System of SpiderCIRCULATORY
SYSTEM Arthropods have open circulatory systems, although most have
a few short, open-ended arteries. Capillaries absent, arteries
directly open into the sinuses, which together form a haemocoel
which is filled with haemolymph. The blood is colourless due to
absence of haemoglobin pigment but the most common respiratory
pigment in arthropods is copper-based hemocyanin; this is used by
many crustaceans and a few centipedes. Heart is tubular and lies on
the dorsal side.
Excretion By Gaurav S Athreya
In Crustaceans Crustaceans have green glands, which is a pair of
excretory organs. Green glands collect waste leftover in different
parts of the body, including the bloodstream. These are connected
by ducts that lead to pores located under antennae where it is
released into the outside environment.
In Insects Insects have malpighian tubules which gathers waste
from blood and puts them into an excretory duct that leads to
intensine. Excretion is eliminated in feces.As well as malpighian
tubules, arachnids have coxal glands that also participate in
excretion
By Pragun JREPRODUCTION IN ARTHROPODS
A few arthropods arehermaphroditic, that is, each can have the
organs of bothsexes. However, individuals of most species remain of
one sex their entire lives. Most arthropods reproduce bysexual
reproduction.Aquaticarthropods may breed by external fertilization
or byinternal fertilization where fertilization takes place inside
the body . All known terrestrial arthropods use internal
fertilization.Most arthropods are oviparous: they lay eggs, but
scorpions areviviparous: they produce live young after the eggs
have hatched inside the mother.
Economic Importance
Crustaceans such as crabs, lobster, crayfish, shrimp and prawns
have been a part of human cuisine and are now farmed on a large
commercial scale.
Cooked tarantulas are considered a delicacy in Cambodia.
The red dye cochineal produced from a Central American species
insect became Mexicos second most lucrative export when the region
was under Spanish rule.
The blood of horseshoe crabs contains a clotting agent Limulus
Amoebocyte Lysate which is now used to test that antibiotics and
kidney machines are free of dangerous bacteria and to detect some
cancers.
Bees produce honey which is the basis of the rapidly growing
industry and international trade.Recently insects have also gained
attention as potential sources of drugs and other medicinal
substancesThe greatest contribution of Arthropods to human food
supply is by pollination. Lately they are also used in animal
husbandryPictures of arthropods
Palaemon
Lobster
Cancer
Cockroach
Grasshopper
Prawn
Praying Mantis
TarantulaCrabScorpion
Mosquito
Millipede
