Arthropod CharacteristicsCopyright © McGraw-Hill Education

Arthropod Features• Arthropods are segmented

invertebrates with bilateral symmetry, coelomate body cavities, and protostome development.

• Arthropods have exoskeletons with jointed appendages.

• Between 70-85% of all named animal species are arthropods.

Arthropod CharacteristicsCopyright © McGraw-Hill Education

Arthropod FeaturesSegmentation• Segments can be fused into three main body regions: a head,

thorax, and abdomen.• The head has mouthparts, eyes, and often antennae.• The thorax is the middle body region to which legs and wings are

attached.• The abdomen is the posterior end of the arthropod and bears

additional legs, contains digestive structures and the reproductive organs.

Arthropod CharacteristicsCopyright © McGraw-Hill Education

Arthropod FeaturesExoskeleton• Provides a framework for support• Protects soft body tissues and slows water loss • Provides a place for muscle attachment• Made of chitin

Arthropod CharacteristicsCopyright © McGraw-Hill Education

Arthropod FeaturesExoskeleton• Arthropods have paired, jointed appendages, which are

structures that extend from an animal’s body. • Adapted for a variety of functions, such as feeding, mating,

sensing, walking, and swimming.• Exoskeleton is made of nonliving material and cannot grow, so

arthropods must shed their old exoskeletons through molting.

Arthropod CharacteristicsCopyright © McGraw-Hill Education

Body Structures of Arthropods Feeding and digestion• Arthropods have diverse feeding habitats and structures.• Many arthropods have a pair of appendages called mandibles

that are adapted for biting and chewing. • Arthropods can be herbivores, carnivores, filter feeders,

omnivores, or parasites.

Arthropod CharacteristicsCopyright © McGraw-Hill Education

Body Structures of ArthropodsRespiration• Arthropods obtain oxygen by using one of three structures :

• Gills- found in most aquatic arthropods• Tracheal tubes – system of branching tubes that carry oxygen

through the body • Book lungs – saclike pockets with highly folded walls,

increasing surface area for gas exchange• Both tracheal tubes and book lungs open to the outside through

openings called spiracles.

Arthropod CharacteristicsCopyright © McGraw-Hill Education

Body Structures of ArthropodsCirculation• Most arthropods do not rely on their

circulatory system to carry oxygen• Transports nutrients and removes

wastesExcretion• In most arthropods, cellular wastes

are removed via Malpighian tubules, which connect to and empty into the gut.

• Crustaceans and some other arthropods do not have Malpighian tubules and instead have modified nephridia.

Arthropod CharacteristicsCopyright © McGraw-Hill Education

Response to stimuli• Vision:

• A compound eye has many facets, which are hexagonal in shape.

• Each facet sees part of an image.• The brain combines the images into a mosaic.

Arthropod CharacteristicsCopyright © McGraw-Hill Education

Response to stimuli• Hearing:

• Many arthropods have a sense organ called a tympanum, which is a flat membrane used for hearing.

• Arthropod tympanums can be located on the forelegs, on the abdomen, or on the thorax.

Arthropod CharacteristicsCopyright © McGraw-Hill Education

Response to stimuli• Chemicals

• Many insects communicate with pheromones – chemicals secreted by many animal species that influence the behavior of other animals of the same species.

• Give off signals related to feeding and mating

Arthropod CharacteristicsCopyright © McGraw-Hill Education

Movement• The muscles are attached to the inner surface of the exoskeleton

on both sides of the joint.• The strength of muscle contraction depends on the rate at which

nerve impulses stimulate muscles.

Arthropod CharacteristicsCopyright © McGraw-Hill Education

Reproduction• Most arthropods reproduce sexually.• Most arthropods brood or incubate their eggs, but do not care for

their offspring once they hatch.