Arthropods 2BIbDF09 10/11

What is an Arthropod?

Arthropods are eukaryotic multicellular heterotrophic organisms that obtain nutrients by ingestion. Arthropods are members of the most diverse phylum in the animal kingdom. They are named for their jointed appendages, which enable these animals to move despite their hard outer covering, the exoskeleton and have a segmented body.

See the Appendix Arthropods 1

you should describe the main architecture of Arthropods... Head-Thorax-Abdomen plus the fact that they do have segments....Pierre.brawand 6 février 2011 à 22:09 (CET)

What are Arthropod's jointed appendages?

Limbs are a prominent feature of species in many phyla. They are particularly important in two major lineages: the ecdysozoans and the vertebrates. Some members of the Ecdysozoa,which is "a clade of moulting animals that encompasses primarily the arthropods ans nematodes", such as arthropods, have more complex, jointed limbs, which make fast, precise walking, running, jumping movements possible and are a prominent limb type in vertebrates and arthropods. Arthropod's appendages of different segments are variously adapted for walking, feeding, sensory reception, reproduction, swimming and defense. Thanks to the evolutionary flexibility of their segments and appendages, it contributes to the great diversification of arthropods.

See the appendix Arthropods 2

you should explain the term Ecdysozoans...Pierre.brawand 6 février 2011 à 22:04 (CET)

PICTURE of appendages needed

What is the role of their exoskeleton?

• chitin
• protection
• allows the muscles to be attached to it involving movement
• problem with growth... because the exoskeleton doesn't grow... molting
• metamorphosis in insects(holometabols Endopterygota), heterometabols and ametabols) See 2.7: How Insects metamorphose?

Are Arthropods divided into several groups?

Arthropods are divided into five different classes:

• Arachnids usually have four pairs of walking legs and specialized pair of feeding appendages.

• Crustaceans are almost all marine organisms but some live in fresh water or in a terrestrial environment. They all have a crustacean hallmark of multiple pairs of specialized appendages.

• Millipedes eat decaying plant matter.

• Centipedes are carnivores are the only arthropods without antenna . They have a pair of poison claws and a single pair of long legs. Both (millipeds and centipedes)have segmented body and jointed legs.

• Insects have six legs and mostly have two pairs of wings.

The estimation about the total arthropod population numbers is a billion billion individuals(10¹⁸), but only a million species has identified, mostly insects. They must be regarded as the most successful animal phylum. The major groups of Phylum Arthropoda are Chelicerata, with some 57'000 species includes spiders or scorpions; Crustacea comprise some 35'000 species of largely marine organisms, like crabs or shrimps; Myriapoda includes Millipedes, with 3000 species are known or Centipedes, with more than 12'000 species; and Hexapoda, like Insects, which has been estimated that approximately a billion billion individual insects are alive at any time.

See the Appendix Arthropods 3

maybe having a number in percentage might help to realize that Arthropods amazingly present on Earth...Pierre.brawand 6 février 2011 à 22:06 (CET)

What are the main characteristics of Arthropods?

We use a table to represent the different characteristics of every groups of the Phylum Arthropoda:

Class	Characteristics	Members
Chelicerata	Mouthparts are chelicarae (pincers or fangs)	Spiders, Mites, Scorpions, Horseshoe crabs, Ticks, Daddy long-legs
Crustacea	Mouthparts are mandibles; appendages are biramous ("two-branched"); the head has two pairs of antennae	Crabs, Shrimps, Isopods , Barnacles, Lobsters
Hexapoda	Mouthparts are mandibles; the body consists of three regions: a head with one pair of antennae, a thorax. and an abdomen; appendages are uniramous ("single-branched")	Insects ( Beetles, Bees, Flies, Butterflies, True bugs, Crickets, Dragonflies, Fleas, Termites, Sucking lice), Springtails
Myriapoda	Mouthparts are mandibles; the body consists of a head with one pair of antennae, and numerous segments, each bearing paired uniramous appendages.	Centipedes, Millipedes

remove that question and focus on ArthorpodsPierre.brawand 6 février 2011 à 22:08 (CET)

Where do they live?

Arthropods can live almost everywhere: on earth, in water, at high height, in deep caves, in deserts and even in glaciers.

How do they feed?

Arthropods feed on different way: of alive or dead organic matter, sometimes live as a parasite on other dead animals. According to their way of food, the structure of the digestive tract changes.Only the central part of the digestive tract is used for the extreme digestion, the extreme parts are covered with cuticle.

• Chelicerata: In the class Chelicarata, the most are carnivorous, but mites are largely herbivorous. They paralyze them predators thanks to their poison and They can store the food in a cavity. They can ingest small particles but most can't consume solid food. They subsist on liquids, including solid food that they liquefy by injecting with digestive enzymes and then suck up with the muscular pharynx.

examples?Pierre.brawand 6 février 2011 à 22:08 (CET)

• Crustaceans: Crustaceans use their appendix to create a current which brings them the food to the mouth. They are filtreurs (zooplankton) or détritivores (crawfish, lobster).

• Insects: Insects are the most important herbivores in terrestrial ecosystem. Every kind of plants is eaten by one or more species.

to precise... not general enough... Pierre.brawand 6 février 2011 à 22:08 (CET)

• Centipedes: Centipedes are carnivorous, feeding mainly on insects. Their appendages of the first trunk segment are modified into a pair of poison fangs.

• Millipedes: In contrast to centipedes, most millipedes are herbivorous, feeding mainly on decaying vegetation such as leaves litter and rotting logs (which are typical habitats for the animals).

How do they reproduce?

• Arachnids: The male weaves a web on which it is going to deposit its sperm. It leaves then in search of a partner. After the coupling, the female eats generally its partner (source of food).

• Crustaceans: Females spawn. Larvas ( called nauplius ) moult several times before reaching the adult stage. This process occurs most of the times, but some crustaceans are however hermaphrodites.

• Millipedes, Centipedes, and Insects: Millipedes, Centipedes and Insects spawn, with extern fertilization. As crustaceans, insects pass by several embryonic stages before reaching the adult stage. In certain species, larvas look like the adults (ametaboles insects). Others undergo a metamorphosis. The metamorphosis is incomplete by hemimétaboles (3 stages: egg, larva, adult. The larva looks like the adult but has no wings) and complete by holometaboles (4 stages: egg, larva, nymph, adult. The larva is completely different from the adult).

How do they move?

Flight is obviously one key of mowing that an arthropod, more exactly an Insect, can make. An animal that can fly that can escape many predators, find food and mates, and disperse to new habitats much faster that an animal that must crawl about on the ground. Because their wings are extensions of the exoskeleton and not true appendages, insects can fly without sacrificing any walking legs. Unlike the flying vertebrates, like birds and bats, have one of their two pairs of walking legs modified for wings, which explains why these vertebrates aren't generally very swift on the ground.

Since their joints haven't exocuticule, Arthropods can move their members and fold a segment over the other one. Their movements are produced by the contraction and the slackening of the fibers of striated muscles. The majority of Arthropods use their members as locomotive means to move, for example the aquatic species use it as paddle and the species ground as legs, to settle, by means of hooks or of flattened lobes serving as suction cups and for "fouisser" (presence of peaks).

How do they breathe?

Arthropods living in two different environment, aquatic and ground, the means of breathings will not thus be the same: either the oxygen is levied in the water under dissolved shape, or in the air in gas form.

middles? This is translated french...Pierre.brawand 30 janvier 2011 à 15:17 (CET)

But there exists an inconvenience about these breathings: arthropods such as crabs, living in zones of balance of tides or still the larvae passing from an aquatic state to a ground state at the adulthood, what leads at a return in the middle aquatic on some of cycle of development, must be able to do in the face of these changes of breathing.

good point... but crabs did adapt to that... by keeping some water in their mouth so their gills are continuously in the water allowing gas exchanges...![ [Utilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:17 (CET)

- The aquatic strict arthropods: The oxygen, in the water, is present and dissolved shape. It stems from the production by autotrophes and of the distribution since the surface. The most effective structures to get the oxygen are gills. It exists three types of breathing: 1. The pallial breathing 2. The breathing appendicular 3. The branchial breathing: a) The gills b) The branchial cavity and the ventilation

This is French... don't translate.... find the information in English websites or books...[[ Utilisateur:Pierre.brawand|Pierre.brawand]] 30 janvier 2011 à 15:17 (CET)

- Zones of balance of tides: The fact that the water level varies according to the tide, that it is increasing or by decreasing, the aquatic arthropods are then subjected to two sorts of different breaths. For this either they resist the anoxia and take place anaerobe, or they develop specialized structures allowing them to consume the oxygen of the air. This last way is found at decapods, as the crab, present a respiratory system allowing the consumption of dissolved or gaseous oxygen. This respiratory system presents three evolutionary stages: breath branchiale, breath integumentary, pulmonary respiration.

- The ground arthropods: These ground arthropods find in the air some oxygen in unlimited quantity. The surfaces of exchange however have to remain wet what does not facilitate the gaseous exchanges. The respiratory system of integumentary origin and the trachea appliance are used to struggle against the desiccation.

- Return in a middle aquatic on some of cycle of development:

How is their internal anatomy?

• Nervous system
• Circulatory system

How Insects metamorphose?

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