THE ARTHROPODS BLUEPRINT OF SUCCESS
Diversity among copepods: The species of copepods have greatest number of individuals. The size of copepod is 1 to 2 mm. These are crustaceans. Copepods are very sucessful marine animals. They feed on the photosynthetic production (panktonic algae) in the open oceans. If plankton net is thrown behind a moving boat in the ocean, three million copepods are collect after 20 minutes. It can fill 2 gallon pail.
Copepods are food for fish, whale, sharks. blue whale and its relatives. Humans eat these fishes. Therefore, human also directly benefited from it. Unfortunately. we do not get this food directly. We use them as a feed of poultry. Therefore, we lose 90% of the original energy present in the copepods.
Copepods are belonged to phylum Arthropoda. Crayfish, Lobsters, Spiders. mites, scorpions. and insects are also arthropods. Zoologists have described about one million species arthropods. It is estimated that 30 to 50 million species are still unsubscribed.
CHARACTERISTICS OF PHYLUM ARTHROPODA
Characteristics of the phylum Arthropoda include:
- They show metamerism. Metamerism is modified by the specialization of body regions for specific functions (tagmatization)
- Chitinous exoskeleton provides support and protection. It is modified to form sensory structures.
- They have paired jointed appendages.
- Ecdysis or molting takes place during growth.
- They have ventral nervous system.
- Coelom reduced to cavities. These cavities are reduced to gonads and sometimes excretory organs.
- They have open circulatory system. Blood is released into tissue spaces (haemocoel derived from the blastocoel.
- They have complete digestive tract
- Metamorphosis is often present. It reduces competition between immature and adult stages.
CLASSIFICATIONS AND RELATIONSHIPS TO OTHER ANIMALS
The arthropods andannelids are closely related. They share many protosome characteristics. These are;
1. Both have schizocoelous coelom formation.
2. Their mouth is developed from blastopore.
3. Paired ventral nerve cords are present in them.
4. Both have meta metamerism.
These characteristics show that the arthropods and annelids have common ancestor. But zoologists disagree about the evolutionary relationships among the arthropods. Many zoologists believe that it is not one phylum. but three.Living arthropods are divided into
three sub- phyla:
4. Tribitomorpha: All members or this subphylum are extinct.