Characteristics and Classes Characteristics and Classes of Arthropodsof Arthropods

By Jerit OwensBy Jerit Owens

General Characteristics of All General Characteristics of All ArthropodsArthropods

All have exoskeletons for support and protectionAll have exoskeletons for support and protection All have jointed appendagesAll have jointed appendages Body regions include: a head, thorax, and an Body regions include: a head, thorax, and an

abdomen. abdomen. Some have a cephalothorax (head and thorax Some have a cephalothorax (head and thorax

are fused together)are fused together) All arthropods molt (shed exoskeleton)All arthropods molt (shed exoskeleton)

General Characteristics Cont’dGeneral Characteristics Cont’d Arthropods use either gills, tracheal tubes, or book lungs Arthropods use either gills, tracheal tubes, or book lungs

for gas exchange.for gas exchange. Acute senses include simple and compound eyes, Acute senses include simple and compound eyes,

brains, and many ganglia.brains, and many ganglia. Arthropods use pheromones to communicate.Arthropods use pheromones to communicate. They have open circulatory systems, complete digestive They have open circulatory systems, complete digestive

system, and efficient means of wastes excretion.system, and efficient means of wastes excretion. Arthropods reproduce sexually, but some exhibit Arthropods reproduce sexually, but some exhibit

parthenogenesis.parthenogenesis.

Class ArachnidaClass Arachnida Spiders, scorpions and mites belong to this class.Spiders, scorpions and mites belong to this class. Spiders are the largest group of arachnids.Spiders are the largest group of arachnids. Most arachnids have only 2 body regions- a cephalothorax and the Most arachnids have only 2 body regions- a cephalothorax and the

abdomen.abdomen. Arachnids have 2 chelicerae for poisoning prey and 2 pedipalps for Arachnids have 2 chelicerae for poisoning prey and 2 pedipalps for

sensing and handling food.sensing and handling food. 4 remaining appendages aid in locomotion.4 remaining appendages aid in locomotion.

Arachnids Cont’dArachnids Cont’d Spiders have silk glands for spinning webs and for wrapping their Spiders have silk glands for spinning webs and for wrapping their

eggs in a cocoon.eggs in a cocoon. Ticks and mites have only one body segment.Ticks and mites have only one body segment. Ticks feed on mammalian blood and can expand up to 1 cm.Ticks feed on mammalian blood and can expand up to 1 cm. Mites are very small and cannot be seen by the naked eye. Mites are very small and cannot be seen by the naked eye.

However their bites, called chiggers, can be felt.However their bites, called chiggers, can be felt. Scorpions have many body segments and 2 pincers and have a Scorpions have many body segments and 2 pincers and have a

long tail with a venomous stinger at the end.long tail with a venomous stinger at the end.

Class CrustaceaClass Crustacea Most crustaceans are aquatic and use gills for gas exchange.Most crustaceans are aquatic and use gills for gas exchange. 2 pairs of antennae for sensing.2 pairs of antennae for sensing. Mandibles for crushing food that move side to side.Mandibles for crushing food that move side to side. Eyes are located on movable stalks.Eyes are located on movable stalks. Many have five pairs of walking legs used for seizing prey and Many have five pairs of walking legs used for seizing prey and

cleaning other appendages.cleaning other appendages. First pair is often modified into strong claws.First pair is often modified into strong claws.

Crustaceans Cont’dCrustaceans Cont’d

Crabs, lobsters, shrimp, crayfish, barnacles, Crabs, lobsters, shrimp, crayfish, barnacles, water fleas, and pill bugs are crustaceans.water fleas, and pill bugs are crustaceans.

Some have three body sections, and others Some have three body sections, and others have only two.have only two.

Land crustaceans like pill bugs must live in Land crustaceans like pill bugs must live in damp environments for efficient gas exchange.damp environments for efficient gas exchange.

Class Chilopoda and Diplopoda Class Chilopoda and Diplopoda Centipedes belong to class Chilopoda and millipedes belong to Centipedes belong to class Chilopoda and millipedes belong to

class Diplopoda.class Diplopoda. Centipedes are carnivorous and eat soil arthropods, snails, slugs, Centipedes are carnivorous and eat soil arthropods, snails, slugs,

and worms.and worms. Centipede bites are painful to humans.Centipede bites are painful to humans. Both have Malphigian tubes for waste excretion.Both have Malphigian tubes for waste excretion. Both have tracheal tubes for gas exchange.Both have tracheal tubes for gas exchange. Millipedes eat mostly plants and dead material.Millipedes eat mostly plants and dead material. Millipedes also have stink glands for scaring predators.Millipedes also have stink glands for scaring predators.

Class MerostomataClass Merostomata

Horseshoe crabs belong to this class.Horseshoe crabs belong to this class. Have remained unchanged since Cambrian period.Have remained unchanged since Cambrian period. Have exoskeletons similar to trilobitesHave exoskeletons similar to trilobites Feed on seaweed, mollusks, and worms on bottom of Feed on seaweed, mollusks, and worms on bottom of

oceans.oceans. Females lay eggs on land.Females lay eggs on land.

Class InsectaClass Insecta Insects are the largest group and most successful arthropods.Insects are the largest group and most successful arthropods. Insects may only mate once or twice in their lifetimes.Insects may only mate once or twice in their lifetimes. Internal fertilizationInternal fertilization Large number of eggs are produced to ensure a large number of Large number of eggs are produced to ensure a large number of

offspring.offspring. Females lay eggs in wood or the ground.Females lay eggs in wood or the ground. May go through complete or incomplete metamorphosis depending May go through complete or incomplete metamorphosis depending

on species.on species.

Insects Cont’dInsects Cont’d

Complete metamorphosis: egg, larva, pupa, and adult.Complete metamorphosis: egg, larva, pupa, and adult. Incomplete metamorphosis: egg, nymph, and adult.Incomplete metamorphosis: egg, nymph, and adult. Nymphs compete with adults for same resources and Nymphs compete with adults for same resources and

are not sexually mature.are not sexually mature.