Arthropods

What is Entomology? The study of insects (and their near relatives). What are insects (and near relatives)? Insects and their relatives are ARTHROPODS.

Review of Zoological Nomenclature (classifying & naming) Taxonomic Categories Phylum Class Order Family Genus Genus & species

Review of Zoological Nomenclature Taxonomic Categories Kingdom - Animalae Phylum - Arthropoda Class - Insecta Order - Coleoptera Family - Scarabaeidae Genus - Popillia Genus & species Popillia japonica Newman

What are some other Animal Phyla? Porifera & Cnidaria – sponges & corals. Platyhelminthes - flatworms, tapeworms Nematoda - roundworms Mollusca - clams, snails & slugs, squids Echinodermata - starfish, sea urchins Annelida - segmented worms (earthworms) Chordata - fish, amphibians, reptiles, birds, mammals

Characteristics of the Phylum Arthropoda The segmented bodies are arranged into regions, called tagmata (e.g., head, thorax, abdomen). The paired appendages (e.g., legs, antennae) are jointed. They posses a chitinous exoskeletion that must be shed during growth. They have bilateral symmetry. The nervous system is dorsal (belly) and the circulatory system is open and ventral (back).

Arthropod Groups (taxa) The arthropods are divided into two large groups that exist today: Chelicerates and Mandibulates

Chelicerate Arthropod Characters: Pincher-like mouthparts - chelicerae - and pedipalps NO antennae Two body regions, usually - cephalothorax & abdomen Four pairs of legs Horseshoe crabs and arachnids are only living groups

 Divided into 3 classes; Arachnida, Merostomata & Pycnogonida  Body divided into 2 regions  Abdomen  Cephalothorax (fused head & thorax)  Lack jaws  Have 6 appendages & no antennae  First appendages form chilicerae (frequently fangs)

Mandibulate Arthropod Characters: Mouthparts are mandibles - normally chewing sideways One or two pairs of antennae Various body region arrangements - cephalothorax & abdomen / head & trunk / head, thorax & abdomen Variable leg numbers Insects, crustaceans & myriapods

 The three main classes of arthropods are: insects (cockroaches, ants, flies, bees, beetles and butterflies), crustaceans (crabs, lobsters, shrimp and barnacles) and arachnids (scorpions, spiders and mites).  Other classes are onychophorans (velvet worms), diplopods (millipedes) and chilopods (centipedes).

 Morphology is a branch of biology dealing with the study of the form and structure of organisms and their specific structural features.  Arthropods present three distinguishing features: they are metameric organisms (segmented body), they have an exoskeleton made of chitin and they have articulated limbs.

 Germ layers :each of the three layers of cells (ectoderm, mesoderm, and endoderm) that are formed in the early embryo.  Gastrulation is a phase early in the embryonic development of most animals during which the single-layered blastula is reorganized into a trilaminar ("three-layered") structure known as the gastrula. These three germ layers are known as the ectoderm, mesoderm, and endoderm.

 A blastula is an animal embryo at the early stage of development when it is a hollow ball of cells

 Arthropods are triploblastic (they have three germ layers) and are coelomate organisms.

 Given their metameric structure, arthropods are evolutionarily closer to annelids, as they also have segmented bodies. In the embryonic development of some arthropods the fusion of metameres takes place, forming structures such as the cephalothorax of arachnids, for example.

 The external shell of arthropods is called the exoskeleton. The exoskeleton of an arthropod is made of chitin, a nitrogen-containing polysaccharide.

 Due to the presence of the exoskeleton, the growth of arthropods is periodical. During the growth period, the animal loses the exoskeleton, grows and develops a new exoskeleton. This process is called ecdysis or molting.

 arthropod video arthropod video

 Since they have an exoskeleton and periodic ecdysis, the growth of arthropods is limited to lessen the organisms' vulnerability to environmental harm. However, some arthropod species contain relatively large-sized species, such as “giant” cockroaches, crabs and spiders.

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 In the exoskeleton of arthropods, there is a layer of waterproof wax. This feature was fundamental in allowing primitive arthropods from the sea to survive on dry land without losing excessive water to the environment.

 The digestive tract of arthropods is complete, containing a mouth and an anus. Arthropods are protostome animals, meaning that the blastopore produces the mouth, during their embryonic development.

 As typical aquatic animals, crustaceans contain highly vascularized gills that are in contact with water and permit gas exchange. In terrestrial insects, respiration is tracheal and gases flow inside small tubes that connect the animal's external surface with tissues and cells without the participation of blood. In arachnids, in addition to tracheal respiration, book lungs (thin folds resembling the pages of a book) may also exist.

 In arthropods, the respiratory system is open (lacunar). Blood, also known as hemolymph, is pumped by the heart and enters into cavities (lacunas), irrigating and draining tissues.  All arthropods have a heart. Crustaceans and arachnids have respiratory pigments. Most insects do not have respiratory pigments, since their blood does not carry gases (in insects, gases reach tissues and cells through tracheal structures). However, some insects do have the respiratory pigment hemoglobin

 Respiratory pigments are molecules able to carry oxygen and other respiratory gases present in circulatory fluids.  In crustaceans and in arachnids, hemocyanin is the respiratory pigment. In humans, the equivalent pigment is hemoglobin.

 In crustaceans, a pair of excretory organs called green glands exists. The green glands collect waste from the blood and other parts of the body. They are connected to excretory pores located under the base of the antennae via ducts. These pores excrete this waste outside the animal.

 In insects, small structures called malpighian tubules remove waste from the blood. moving it into excretory ducts that open into the intestine. In these animals, excretions are eliminated together with feces.  In arachnids, in addition to malpighian tubules, there are coxal glands located in the cephalothorax near the limbs that are also involved in excretion.

 In arthropods, the nervous system has more sophisticated sensory receptors with advanced cephalization. In the anterior region of the body, there is a group of ganglia which form a brain connected to two ventral ganglial cords that contain motor and sensory nerves.  The increased development of the sensory system of arthropods provides more possibilities for these animals to adapt and, as a result, a greater ability for them to explore many different environments.

 Arthropods have compound eyes made of several visual units called ommatidia. Each ommatidium transmits visual information through the optic nerve to the brain, which interprets the image. These ommatidia are round and numerous, and their external surfaces point in different directions creating independent images.

 This causes arthropod eyes have a visual field larger than that of vertebrates. Some insect have one or more simple eye in addition to their pair of compound eyes.

 Reproduction in animals of the phylum Arthropoda is sexual, with a larval stage in some insects and crustaceans (arachnids only go through direct development).

 Nymphs are the larvae of hemimetabolous insects (such as grasshoppers). They are very similar to the adult insect, although smaller. In holometabolous insects (such as butterflies), the larva makes a cocoon (chrysalis, pupa) where it lives until transforming into the adult form. Imago is the name given to the adult form of insects with indirect development.

 having no pupal stage in the transition from larva to adult.

 characterized by complete metamorphosis

 Crustaceans and arachnids do not have wings. Most insects have wings.

 Crustaceans have two pairs of antennae; insects have one pair; arachnids do not have antennae.

 In crustaceans and arachnids, the head is fused with the thorax to form the cephalothorax. Their body is therefore divided into cephalothorax and abdomen.  Insects have a head, thorax and abdomen.

 Insects are the animal group with the greatest diversity of species. Almost 750,000 insect species are known, making up approximately 55% of the total already recorded species of living organisms (compare this with mammals, with no more than 4,000 known species). However, scientists estimate that the number of unknown species of insects may be over 2 million.

 The insect population on the planet is estimated to be more than 10 quintillion (10,000,000,000,000,000,000).  The evolutionary success of insects is due to factors such as their: small size and diversity of foods, which make it possible for them to explore many different ecological environments; wings, which provided them with a greater area to spread across; tracheal respiration, which makes them highly agile; high reproductive rates, which produces a large number of offspring.

 Insects such as some species of bees, wasps, ants and termites form societies that contain hierarchies and the division of jobs among their members. Spiders build sophisticated external structures, their webs, mainly to serve as a trap for capturing prey. Another example is the communication mechanism in some bees known as the bee dance, through which one bee tells others information about the location of flower fields and other sources of nectar.

Orders of Arachnids Scorpions Pseudoscorpions Daddy Long-Legs Mites & Ticks Spiders

 Very diverse class  Most species parasitic or predatory  Many possess book lungs for gas exchange  Spiders are able to produce a strong polymer - silk  Chilicera in form of fangs

Tarantula Black Widow

The brown recluse and its bite wounds

Dust Mite Common Mite

 Ancient group of species  Changed little over 350 million years  Aquatic, mostly found on Atlantic & gulf coasts of United States

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Scorpion Tick (a mite) Pseudoscorpion Daddy-long-legs Wolf Spider

Scorpion Anatomy

chelicerae eyespedipalp

Pseudoscorpion

pedipalps & chelicerae cephalothorax abdomen Mite and Tick Body Regions

American dog tick male Blacklegged (deer) tick female

American dog tick female laying egg mass ( eggs!).

Clover mites Twospotted spider mites Predatory mite

daddy long-legs cephalothoraxabdomen

pedipalp chelicera (fang) cephalothorax abdomen narrow waist Spider Anatomy

Abdomen Pedipalp Chelicera (fang) Cephalothorax Jumping Spider

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Wolf spider with egg caseSpitting spider Tarantula Orb-weaving spider

Black widow with egg case Brown recluse

Classes of Myriapods (many legged arthropods) (all have one pair of antennae, a head region, and trunk with many pairs of legs, use trachea) Diplopoda - millipedes Chilopoda - centipedes

Myriapods Millipede (Diplopoda) Two pair of legs per visible segment, attached under body. Centipede (Chilopoda) Pair of fangs under head, one pair legs per visible segment - attached to side of body. No fangs, no eyes, legs attached to side of body. [one pair of antennae, head & trunk regions, trunk with many pairs of legs]

Millipede (Diplopoda) Centipede (Chilopoda) Garden centipede

Classes of Crustacea mostly marine, fresh water, a few terrestrial all have two pair of antennae five or more pairs of legs segmented abdominal appendages head & trunk or cephalothorax & abdomen body arrangement have gills Sowbugs or pillbugs Sand fleas Barnacles Crabs, lobster, shrimp

Crayfish cephalothorax (Decapoda) Sowbug (Isopoda), a terrestrial crustacean