Arthropods

Arthropods composed of the words arthro and poda, arthro means a segment, book, or segment; and poda / podos means feet. Thus, Arthropods are animals that have booky or segmented bodies and legs. Arthropods live in terrestrial, freshwater and sea water habitats.

Characteristics of Arthropods

The following are the characteristics of the phylum Arthropoda:

  1. Segmented body and legs.
  2. Including the triplobastic coelomate animal group, namely the true body cavity and has three body layers.
  3. The body is covered with an exoskeleton (made of protein and chitin compounds) which functions to protect and form the body’s skeleton.
  4. The body is divided into three parts, namely the head (caput), chest (thorax), and stomach (abdomen).
  5. Already have a nervous system, digestive system, excretory system, circulatory system and senses.
  6. Using gills, trachea, body surfaces, or book lungs as a means of respiration.
  7. Including animals with two houses means that the sex has been separated between male and female.
  8. Reproduction is done both sexually and asexually. Sexual, namely by internal fertilization (fertilization occurs in the body). Asexual, namely by parthenogenesis (males are not involved in the fertilization process) and pedogenesis (reproduction occurs in young individuals).

Classification & Examples of Arthropods

Based on their characteristics, Arthropods are divided into four classes, namely:

1. Class Arachnoidea

Arachnoidea’s body is divided into two parts, namely the cephalothorax (head that is united with the chest) and abdomen. In the cephalothorax there are four pairs of legs, a pair of poisonous stingers (calisera), and a pair of claws (pedicalpus). Arachnoidea does not have an antenna. Arachnoids use book lungs, trachea or both as their means of breathing.

Arachnoidea has 3 orders, namely Scorpionidae (scorpions), Arachnids (spiders), and Acarina (fleas, mites, ticks). Arachnoidea is a source of food for predators, but some Arachnoidea are pests to plants and parasites on livestock so that they are detrimental. Examples of species from the Arachnoidea class, namely Thelyphonus caudatus (scorpions), Heterometrus cyaneus (blue scorpions), Nephila (spiders), and Boophilus annulatus (parasites on cows).examples of the class arachnoidea arthropods

Examples of arachnoidea: Scorpions, Spiders, and Gepers
Image Source: Kistinnah I & ES Lestari. (2006)

2. Crustacean class

Crustaceans are shelled animals. The shell is a hard outer frame made of chitin and lime. Crustacean body is divided into 2 parts, namely cephalothorax and abdomen. There is a carapace which functions to protect the cephalothorax. In the cephalothorax, there are two pairs of antennae equipped with eye spots as a sensory tool and a statolith as a means of balancing the body. On each vertebra there is one or more pairs of legs.

Crustaceans have two orders, namely entomostraca and malacostraca. Crustaceans are widely processed as food by humans because they have high protein such as shrimp and lobster. However, some crustaceans such as crabs and yuyu are pests for certain crops. Examples of species from the Crustacean class are Penaeus (tiger prawn), Macrobium resenbergi (giant prawn), Cambarus virilis (freshwater shrimp), Parathelpusa tredenlata (crab), Portunus sexdentalus (crab), and Neptune pelagicus (crab).crustacean class arthropod body structure

Body structure in one crustacean
Image Source: Mader, S. (1995)

3. Myriapoda class

Myriapoda is an animal that has many legs on each segment of its body. Myriapoda does not have a chest so that the body part of Myriapoda is only divided into the head and abdomen. There are a pair of antennae and a canine mouth on the head of the Myriapoda. The body of the Myriapoda is long and segmented and each segment of the body contains one to two pairs of legs.

The Myriopoda class has two orders, namely Diplopoda and Chipolopoda. Diplopoda is an animal that has two pairs of legs on each segment of the abdomen, such as Julus teristris (keluwing) and Lulus sp. (Centipede). Whereas in Chipolopoda there are only a pair of legs on each segment of the abdomen, such as Scolopendra subspinipes (centipedes) and centipedes (Scutigera sp.). Myriapoda acts as an animal recycling or eating waste remains (detritivor).

4. Class Insect

Insects or insects dominate the number of animals that are found in nature. The body of the insect is divided into three parts, namely the head, chest and abdomen. On the head there is a mouth, chemical and mechanical receptors in the form of antennae, single eye, and compound eye. The body parts of the insects are protected by an exoskeleton. In general, insects have wings and breathe using the trachea.

Insects have four types of mouths, namely the dipteran type (lick and sucker), the lepidopteran type (sucker), the hemipteran type (prick and sucker), and the orthopteran type (biter). Insects are animals that undergo metamorphosis. Metamorphosis is a change in shape from egg to adult that occurs during the growth process. There are two kinds of Metamorphosis in Insects, namely:

Process:

Egg  longrightarrow

larva (caterpillar)  longrightarrowpupa (cocoon)  longrightarrowimago (adult animal).

Example: bees and butterflies.

  • Incomplete metamorphosis

Process:

Egg  longrightarrow

young animal (nymph)  longrightarrowimago (adult animal).

Example: grasshoppers and crickets.

Based on the existence of its wings, the Insect class is divided into two groups, namely:

  1. Pterygota, is a group of winged insects. Pterygota has 10 orders, namely: Odonata (dragonflies); Homoptera (ticks); Coleoptera (ladybugs, beetles): Orthoptera (praying mantis); Hemiptera (walang sangit); Isoptera (larons); Lepidoptera (butterfly); Diptera (mosquito); Siphonoptera (dog fleas); and Hymenoptera (bees).
  2. Apterygota, is a group of insects without wings, such as book lice (lepisma).

Insects play a role in helping pollinate plants, producing honey (bees), silk (silkworms), predators of pests, and helping to decompose waste. However, some insects are also pests (rice planthopper), parasites, and can become vectors of disease (Trypanosoma sp. Malaria vector.)

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