Quiz 19: Trilobites, Chelicerates, and Myriapods


Organs such as compound eyes and others help to sense touch, smell, hearing, chemicals and to keep balance. These organs keep arthropods alert in their surroundings. • Complex behavior patterns: Arthropods show complexity and organization in most of their activities.

The subphyla of Arthropods with examples are - 1) Subphylum Trilobita Examples - Isotellus, Harpes, Walliserops, Phacops 2) Subphylum Chelicerata Examples - Limulus, Pycnogonum, Latrodectus 3) Subphylum Myriapoda Examples - Julus, Scutigera, Pauropus, Scutigerella 4) Subphylum Crustacea Examples - Branchinecta, Daphnia, Caligus, Balanus, Cancer 5) Subphylum Hexapoda Examples - Gerris, Halobates, Drosophila, Danaus

Cuticle forms a highly protective exoskeleton for arthropods. The cuticle has two layers-inner procuticle and the outer epicuticle. The procuticle is thick while the epicuticle is thin. The procuticle is highly flexible and light weight. It provides protection against dehydration and other biological and physical stress without interfering with the mobility of the animal. The cuticle is thin and flexible between the segments of the appendage and between body segments. This creates movable joints and permits free movement. Cuticle may provide support to the tracheal system and may also line the foregut and the hindgut. In this way, the cuticle contributes to the success of arthropods. The other factors that contribute to their success are- (1) Tracheal system- Because of highly effective tracheal system, arthropods can maintain high metabolic rate during the periods of intense activity. (2) Metamorphosis - Arthropods pass through different metamorphic stages which reduce intraspecific competition. (3) Highly developed sensory organs such as compound eyes and other organs for sensing touch, smell, hearing and chemicals keep the arthropods alert in their environment. (4) The presence of jointed appendages and segmentation helps the animal in locomotion.

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