Phylum Arthropoda: General Characters and Example

 

Defination

• Arthropods have segmented bodies, jointed appendages and chitinous exoskeleton.

• This is the largest phylum of Animalia which includes insects. Over two-thirds of all named species on earth are arthropods

General features

• They have organ-system level of organisation with bilaterally symmetrical, triploblastic, segmented and coelomate animals. 

• The body of arthropods is covered by chitinous exoskeleton. 

• The body consists of head, thorax and abdomen and in some head is joint with thorax called cephalothorax.

• They have jointed appendages. 

• Respiratory organs are gills, book gills, book lungs or tracheal system. 

• Circulatory system is of open type. Sensory organs like antennae and  eyes which can  be compound and simple.

• Statocysts or balancing organs are present in aquatic arthropods . 

• Excretion takes place through malpighian tubules. 

• They are mostly dioecious. Fertilisation is usually internal. They are mostly oviparous. Development may be direct or indirect.

• Economically important insects  are :

         Apis or Honey bee  

        Bombyx or  Silkworm               Laccifer or  Lac insect

• Some Arthropods are vector of diseases. Anopheles, Culex and Aedes are vectors of Malaria , Filaria and Dengue respectively.

Examples of Arthropoda  

1. Locusta

• Locusta is a Gregarious pest. It become more active and take unusual flight during high temperature.

• It is herbivores with large wing and body colour is yellow or brown.

• It has six jointed legs and Short antennae.

• It can change body color and shape when it move to gregarious phase.

• It follows various stages in its life cycle when it convert from larval to adult.

• It has well developed nervous system or brain when it attains the gregarious phase.

 2. Limulus 

• It is also called as king crab and it is a Living fossil.

• It is marine and body is divided into cephalothorax and abdomen.

• Cephalothorax is broad and covered by the horse shoe carpacae.

• Abdomen has sex segments and bear six pairs of appendages.

• First segment of abdomen bear genital pore and other five pairs have book gills for respiration.

• Coxal glands is present for Excretion.

• Development is indirect with Trilobite larva.

3. Paleomon 

• It is also called as Prawn. Body is divided into cephalothorax , abdomen and tail.

• Adult stage is dark red or orange red but it's young stage is green or brown.

• It has five pairs of walking leg in head and five pairs of swarming leg on abdomen .

• The body of Prawn is covered by chitinous exoskeleton.

• Carapace covers cephalothorax  completely.

• Telson is a tail fin that bear anus.

• Uropods are last segment that help in movements.