Zoology Ch. 21 Arthropods 3

Characteristics of Subphylum Hexapoda

Six legs which are all uriamous; Have three tagmata the head thorax and abdomen;; Appendages attached to head and thorax, Abdominal appendages may be reduced or totally absent

Body plan of Subphylum Hexapoda

Head thorax and abdomen; Thorax has three segments: prothorax, mesothorax, and metathorax, each has a pair of legs, meso and meta often have wings; legs and wings, highly variable and modified

What are the benefits of having highly variable and modified legs and wings?

This gives subphylum hexapoda access to every possible niche and all types of habitats

What are the different types of leg modifications?

Hind legs of grasshoppers and crickets enlarged for jumping

Mole crickets have front legs adapted for burrowing

Water bugs and beetles have paddle shaped legs for swimming

Forelegs of praying mantis are long and strong for grasping

Honeybees have leg adaptations for collecting pollen

Wings of Subphylum Hexapoda

Made of cuticle; Most insects have two pairs of wing but some have only one or reduced hind/forewings called halters(true flies)

Flight in Subphylum Hexapoda

Controlled by a complex of muscles in the thorax with specific muscles for direct and indirect flight

Direct flight muscles

Attached directly to the wing, when these muscles contract, the wing is pulled down

Indirect flight muscles

Attached to thorax, moves wing by altering shape of the thorax elevating the wings

Head of Subphylum Hexapoda

Equipped with a pair of large compound eyes, three ocelli, one pair of antennae, variable mouthparts

Functions of antennae

Touch, taste, hearing

Digestive system of Subphylum Hexapoda

Made up of the foregut, midgut, hindgut

Foregut

Mouth, salivary, glands, esophagus, crop, gizzard

Midgut

Stomach and gastric ceca, main site for digestion and absorption

Hindgut

Intestines, rectum, anus; major area for reabsorption of water, and some ions

Feeding habits of Subphylum Hexapoda

Phytophagous: feed on plants juices and tissues

Saprophagous: feed on dead animals

Predaceous: catching and eating organisms

Parasitic: feed on a living host

Parasitoids: parasites that kill their host

Mouthparts of subphylum Hexapoda

Highly specialized for different feeding strategies:

Strong mandibles with toothed plates for biting and chewing; sucking mouthparts very greatly informed and function

Circulatory system of Subphylum Hexapoda

An open circulatory system with a tubular heart, accessory pulmonary organs, use body movements increase the flow of Hemolymph

Hemolymph

Contains plasma and amebocysts, does not function in oxygen transport in most insects, some immature aquatic insects have hemoglobin for oxygen transport

Tracheal System of Subphylum Hexapoda

Made up of tracheae that branch out into smaller fluid filled tracheoles that branch into fine network that covers cells. Has spiracles open to the outside that usually have valves to reduce water loss And a filtering device. Two pairs of the spiracles are found on the thorax and 7 to 8 pairs on the abdomen. Gas exchange occurs via diffusion between tracheoles and cells.

Excretion & H2O balance in Subphylum Hexapoda

Occurs in Thin and elastic Malpighian tubules attached to the juncture between midgut and hindgut, Free end live in hemocoel and our bathed and hemolymph

How does excretion work in Subphylum Hexapoda

Uric acid and ions(Potassium and sodium) are pumped into tubules via active transport, water follows by osmosis, moves to gut where water and ions are reabsorbed and uric acid is excreted with feces

Mechanoreception in Subphylum Hexapoda

Touch, pressure, and vibrations are detected by sensilla(Single leg setae or complex organ with sensory cells)

Auditory reception in Subphylum Hexapoda

Tympanic organs and sensilla

Chemoreception in Subphylum Hexapoda

Sensilla in pits sense taste and smell. Found in mouth, parts, antenna, and legs, their function is for feeding, mating, habitat, selection, and finding a host

Vision in Subphylum Hexapoda

Three ocelli on head or compound eyes which enable vision from almost any direction in fuzzy images

Reproduction in Subphylum Hexapoda

They attract mates with pheromones, sounds, flashes of lights, color, signals, etc; Internal fertilization- sperm releases directly or in spermatophores, can be stored in females seminal receptacles

Complete Metamorphosis

88% of insects, separate stages for growth(larvae), differentiation(pupa), and reproduction(adult), minimize this competition among life stages for same species

Incomplete metamorphosis

Developed into winged adults through successful molts and growth(nymphs), Adults often use different environments than nymphs

What controls metamorphosis?

PTTH hormone(precursor to molten hormone, Initiates molting) and juvenile hormone (Triggers larval molting)

Types of Dormancy

Hibernation(winter), Estivation(summer), Diapause

Diapause

A seasonal period of dormancy to avoid adverse environmental conditions(arrested development), triggered by changes in photoperiod(daylight), Occurring at the end of a growth period(ready to molt)

Types of Defense used in Subphylum Hexapoda

Exoskeleton, repulsive odors, aggressive offense, quickly moving to cover, chemical warfare, aposematic coloration, Crypsis(blend in), Mimicry

How does subphylum hexapoda use pheromones to communicate?

Attract maids, send an alarm, initiate group behaviors, mark trails, define territories, identification, cast level

How does some phylum hexapoda use sound to communicate?

Warning devices, advertised territory, courtship songs

How does subphylum hexapod use tactile communication?

Tapping, stroking, grasping, and antenna touching, can all be used for recognition, alarm, recruitment

How does subphylum Hexapoda use visual communication?

Bioluminescence is used in fireflies to attract to mate or trick males of different species(prey)