Arthropods are animals that have features of broad legs, bristles, or segments
Definition of Arthropods
Arthropods (in Latin, Arthra = segments, books, segments; podos = legs) are animals that have features of broad, knuckled, or segmented legs. These segments are also present in their bodies. Arthropod bodies are bilateral symmetrical and belong to tripoblastic selomata.
Body size and shape
Arthropod body sizes are very diverse, some of which have a length of more than 60 cm., But most are small. Likewise with the various forms of Arthropods.
Body structure
Arthropod body segmented with a number of segments that vary. In each segment of the body there is a pair of legs that segmented. Segments combine to form parts of the body, namely Kaput (head), thorax (chest), and abdomen (stomach).
Another characteristic of Arthropods is the presence of hard cuticles that form the outer skeleton (exoskeleton). The exoskeleton is composed of chitin secreted by skin cells. The exoskeleton is attached to the skin to form strong body protection.
The exoskeleton consists of plates which are connected by flexible and soft ligaments. The exoskeleton cannot enlarge following the growth of the body. Therefore, the stage of Arthropod growth is always followed by exfoliation of the old exoskeleton and the formation of new exoskeleton.
The release stage of the exoskeleton is called molting or ekdisis. Animals that usually carry out ecdysis are crabs, shrimp and spiders.
Arthropod nervous system in the form of a rope ladder nervous system totaling a pair that is along the ventral side of the body.
At various places in the body segment, there is an enlarged nerve of the rope ladder called the ganglia. Ganglia functions as a reflex center and controls various activities. The larger anterior ganglia functions as the brain.
Arthropod's digestive system consists of the mouth, esophagus, stomach, intestine, and anus. The mouth is filled with a variety of additional tools, such as the mandible and maxilla in grasshoppers.
Arthropods breathe with gills, trachea, or book lungs. The metabolic residue in the form of fluid is excreted by the excretory organs called the Malpighi ducts, excretion glands, or both.
The Arthropod circulation system is open. The circulatory system consists of the heart, short blood vessels, and the space around the body's organs called sinuses or hemosols. Arthropod blood is also called hemolymph.
Way of life and habitat
Arthropod way of life is very diverse, there are free living, parasitic, commensal, or symbiotic. In our environment, these animal groups are often found, such as mosquitoes, flies, ants, butterflies, dragonflies, grasshoppers, and bees.
Arthropod habitat is very widespread. There are at sea, freshwater, desert, and grassland.
Reproduction
Arthropod reproductive system generally occurs sexually. But there are also those that are asexual, namely parthenogenesis.
Parthenogenesis is the formation of new individuals without going through fertilization (fertilization). The resulting individuals are sterile. Male and female reproductive organs in separate Arthropods, each producing gametes in different individuals so that they are dioseous (two houses). The results of fertilization in the form of eggs.
Arthropod Classification
Arthropods are classified into 20 classes based on body and foot structure. The following four classes will be described which are the most common, namely Arachnoidea, Myriapoda, Crustacean, and Insecta Classes
Arachnida
Arachnoidea (in Greek, arachno = spider) is also called the spider group, although its members are not spiders. Scorpions are one example of the Arachnoidea class of 32 species. Arachnoidean body sizes vary, some of which have smaller lengths. from 0.5 mm to 9 cm. Arachnoidea is a terrestrial animal (land) that lives freely or parasitically. Arachnoidea that lives freely are carnivorous.
Arachnoidea is divided into three orders, namely Scorpionida, Arachnida, and Acarina. Scorpionida has a poisonous stinger in the last abdominal segment, examples of these animals are the scorpion (Uroctonus mordax) and the ketunggeng (Buthus after).
In Arachnida, the abdomen is not segmented and has a poisonous gland in its calorie (stinging device), for example this animal is a wolf spider (Pardosa amenata), a sloping spider (Nephila maculata). Carina has a very small body, for example is a tick or spider mites (Acarina sp.).
The following are the characteristics of one of the Arachnoidea animals that we often encounter, namely the spider. Its body consists of two parts, namely cephalothorax (head-chest) on the anterior and abdomen in the posterior part. Spalothorax is the union of the body of the cephal or head (head) and thoracic (chest) section.
In the cephalothorax there is a pair of calisera (stinging devices), a pair of pedipalpus (claws), and six pairs of legs for walking. Calcium and pedipalpus are additional tools in the mouth.
In the abdomen (opistosoma) spider consists of mesosomes and metasomas. In the posterior abdomen there are spinerets which are cone-shaped organs and can rotate freely.
Inside the spineret there are many spigots which are holes in the release of fine glands or abdominal glands. Fine thread glands secrete fluids containing elastic proteins. The elastic protein will harden in the air to form fine threads that are used to trap prey.
The spider breathes with the book lungs or trachea. The lungs of the book are many layered respiration organs like books and are located in the abdomen. Excretion of spiders is carried out with the Malpighi (single = tubule) tubules.
Malpighi Tubules are long, clogged tubes and these organs are located within the hemosol which empties into the intestine. Besides the Malpighi Tubules, other excretions are carried out with the coccal gland. The coccal gland is a dead-end excretory gland that empties into the cocsa region (a segment of the insecta leg).
Myriapoda
Myriapoda (in Greek, myria = many, podos = legs) is a multi-legged animal. Animal millipede is one of which we sometimes see in the environment around us. Myriapoda lives on land in damp places, for example under leaves, rocks, or pile of wood. Myriapoda's body parts are difficult to distinguish between the thorax and the abdomen. The body is elongated like a worm.
On the head there are antennas, mouths, and one pair of mandible (lower jaw), two pairs of maxilla (upper jaw), and oseli-shaped eyes (single eye). Its body is segmented with one to two pairs of limbs in each segment.
Each segment has a respiration hole called a spiracle leading to the trachea. Its excretion is with the malpighi tubule. Myriapods are diocese and internally carry out sexual reproduction. Myriapods are divided into two orders, namely Chilopoda and Diplopoda.