Arthropod Lab

Kiara Staton Vu PAP-BIO 2nd Period

Background Information

Kingdom Arthropoda has many different organisms. In this lab grasshoppers and crayfish are looked at. They are apart of the same phylum but have different classes. The grasshopper is a part of Insecta and the crayfish is a part of Crustacea. The phylum traits for these organisms, are legs, which both have present, jointed limbs, abdomen segmented, there are eyes present, and antennae. There are also mouth parts present. The location of the nerve cords are located on the ventral side and the heart is located on the dorsal side.There digestive systems are similar and their sexes are also the same. The circulatory system is open for both organisms as well.

External Anatomy

The crayfish is an organism with 5 pairs of legs, a body in regions, a segmented abdomen, appendages located on the abdomen and eyes present. The organism also has 6 antennae (including antennule), there are mouth parts present, and a telson present. The respiratory organ of the crayfish are gills. The ventral side is the location of the nerve cord, and the dorsal side is the location of the heart. The excretory organ of the organism is the green gland. The exoskeleton of the organism is present, and the circulatory system is open. The sexes of the crayfish are also separate.
The organism is hard, and the ligaments are pretty stiff. Important defining features are the cheeped, which are the claws of the organism, the uropod that is a part of the tail, and the telson that is the actual tail. The swimerettes help the organism to swim and its walking legs are present for when it goes onto the land. The abdomen is the base of the body, and is used to hold the body together, the antennae are also important, there are six of them in total.

External Anatomy of the Grasshopper

The grasshopper has legs present, 3 leg pairs, and there body is in regions. There are no appendages on the abdomen, and eyes are present, as well as antennae. There are 2 antennae present, and wings also present on the organism. The mouth part is present, but there is no telson. The respiratory organ are the spiracles, and the nerve cord is located on the ventral side while the heart is on the dorsal side. The name of the excretory organ is the malpighian tubule. The exoskeleton is present and the circulatory system is also open.
The organism is hard and has tarsus, on its tibia, which make a noise that can attract and deter organisms. There are two antennae, and the femur is located near the wing of the organism and by the labium. The forewing is the front of the wing, and the hind wing is near the back. The ovipositor is also located at the back of the organism.

Skin?!

Arthropods are invertebrates that have an exoskeleton. The exoskeleton is their integumentary system. The skin is hard, and made up of a tough polymer called Chitin. It acts like an armor, and protects them against predators. It also prevents their bodies from drying up, which helps them to survive in extreme dry conditions like the deserts. The exoskeleton has four layers, namely epicuticle, procuticle, epidermis and basement membrane. The topmost layer, or the epicuticle, serves to lock in water, while the procuticle is the layer that gives strength to the exoskeleton. The third layer, or the epidermis, is responsible in secreting the procuticle.The muscles of the arthropods are attached to the exoskeleton. The exoskeleton is divided into head, thorax and abdomen. In spiders, their head and thorax are fused and is called Cephalothorax, as the exoskeleton is divided into cephalothorax and abdomen. The exoskeleton has one disadvantage. It does not grow with the rest of the body. So, it has to molt or shed its skin when it gets too small for the body. Before the shedding process, the cuticle separates from the epidermis in the process called as Apolysis. Then the epidermis secretes a new cuticle, which is soft and takes time to harden. Hardening occurs with dehydration of the cuticle. The new skin will be pale, and it darkens as it becomes harder. In this molting stage, the arthropod has to be careful as it is vulnerable to attacks from predators.

Picture This...

  • Ancestral arthropods were the first land animals.
  • Arthropods are a highly successful group of animals—they account for over three quarters of all currently known living and fossil organisms.
  • During their life cycle, arthropods undergo a transformation called metamorphosis.
  • When arthropods grow, they must molt their exoskeleton.
  • The Subphylum Trilobitomorpha is an extinct subgroup of arthropods.