Arthropoda Characteristics & Systems

• Below are updated study notes based on the provided text.

General Arthropoda Characteristics: Review

• Arthropods inhabit liquid and terrestrial environments.
• They can be herbivores, carnivores, omnivores, or detritivores
• Organ system level of organization.
• Triploblastic, coelomic animals displaying bilateral symmetry.
• Body shows segmentation, with metameric segments.
• Thoracic segments have paired appendages, hence the name Arthropoda.
• Segments may have 3-4 pairs of legs.
• Some appendages, like those in a cockroach, may not have a function other than protection.
• External segmentation is present, with a chitinous exoskeleton secreted by the epidermis.
• Exoskeleton is jointed by arthrodial membranes, allowing movement.
• Plates of the exoskeleton are called sclerites.
• Wings are present on some segments, with two pairs on the thoracic region.
• The first abdominal segment lacks wings.
• Arthropoda is a very large phylum.

Arthropod Digestive Systems

• Possess a complete digestive system with a mouth and anus.
• Mouth structures are greatly varied and a defining feature.

Arthropod Mouth Types

• Piercing and sucking mouthparts: used to puncture and extract fluids and found in sanguivorous arthropods.
• Sucking mouthparts: designed for passively absorbing liquids; observed in male mosquitoes, which feed on nectar.
• Siphoning: a structure is used to siphon up fluids from a distance; found in butterflies that feed on nectar from flowers.
• Sponging mouthparts: use a sponge-like structure to absorb liquids or liquefied food; present in houseflies, which secrete saliva to liquify food.
• Biting and chewing mouthparts: used to grasp and chew solid foods; seen in cockroaches that eat a wide range of food.

Arthropod Mouth Parts

• Maxillae and mandibles: function as jaws.
• Labrum and labium: equivalent to lips.
• Hypopharynx: a tongue-like structure.
• Saliva can moisten food and may contain enzymes.

Digestive System Breakdown

• Pharynx: involved in swallowing.
• Esophagus: transports food to the crop.
• Crop: a storage organ for food.
• Gizzard (proventriculus): grinds food particles.
• Intestine: divided into foregut, midgut, and hindgut.
• Midgut: site of most digestion and absorption.
• Hindgut: involved in water reabsorption and waste elimination.

Arthropod Excretory Systems

• Arthropoda includes three major classes: Crustacea, Insecta, and Arachnida.
• These classes have variations in excretory organs.

Crustacea

• Includes crabs
• Typically live in water.
• Possess book gills.
• Book gills = excretory organ.

Insecta

• Includes insects.
• Posses Malpighian tubules.
• Malpighian tubules: excretory organ.

Arachnida

• Includes spiders and scorpions.
• Possess book lungs.
• Book lungs: excretory organ.

Excretory System Details

• Malpighian tubules: 150-200 tubules in the digestive tract.
• Remove waste from the body and empty it into the rectum.
• Used for osmoregulation and excretion.

Gland specifics

• Coxal glands: found in the coxae (leg base) of some arthropods.
• Green glands (antennae glands): located near the antennae of crustaceans.
• Involved in excretion and osmoregulation in aquatic taxa.

Respiratory System Variations

• Gills (aquatic): include book gills (Crustacea).
• Book lungs (terrestrial): (Arachnida).

Tracheal System

• Insecta possess network of branching tubes throughout the body.
• Tracheoles: small, fluid-filled tubules end directly on tissues.
• Spiracles: external openings on the body surface.
• Oxygen diffuses directly to tissues.
• Carbon dioxide diffuses directly out.
• No need for blood to transport gases.