Arthropods are different from all other animals because they are eucoelomates with a hard, segmented body. The phylum Arthropoda (jointed-foot) consists of most of the known animals and many are enormously abundant as individuals. The general characteristics of the arthropods include a hard exoskeleton called a cuticle made up of chitin and proteins. This hard exoskeleton gives the organism’s segmented body protection and a place for muscle attachment. Arthropods also have jointed appendages that allow for specialized functions. They have an organ system level or organization and they are triploblastic. There are five subphyla: Trilobita, Checlicerata, Crustacea, Myriapoda, and Hexapoda.

Subphylum: Trilobita

This subphylum (like other arthropods) have paired appendages.They are segmented without any specialization. This subphylum are all extinct (Permian era – 250 mya)

Subphylum: Cheliceriformes

Cheliceriformes all have 6 pairs of appendages. The first pair is modified into chelicerae. The next pair are modified into pedipalps. The last 4 pairs are walking legs. These animals have one or two body regions (cephalothorax and abdomen). These animals do not have a mandible or any antennae.

Class: Eurypterids

The Eurypterids or water scorpions are animals that are now extinct. They were normally marine and freshwater predators.

Class: Merostomata

These organisms (horseshoe crabs) are found in shallow coastal waters. The first pair of appendages are modified into chelicerae but the second pair is not modified into pedipalps like other cheliceriformes. The Horseshow crab’s larvae look similar to the extinct trilobites.

Class: Pycnogonida

These organisms (sea spiders) are usually found in shallow coastal waters and many polar oceans. These animals often have eight legs (like true spiders) but may have extra legs from their segments being duplicated.

These organisms include spiders, scorpions, ticks, and mites. Spiders contain modified chelicerae which are used as fangs to inject poison. They also have a special gland that can produce silk used for webs, eggs, escape, and courtship. Scorpions are the first terrestrial invertebrates. Their pedipalps are modified into pinchers and their tail is modified into a stinger. Ticks and mites are parasitic.

Class: Arachnida

Subphylum: Crustacea

Crustacea have two pair of antennae. Each appendage is biramous (two main branches). They have mandibles. These animals have two or three body regions (cephalothorax and abdomen or head, thorax, and abdomen). These animals are mostly marine.

Isopoda

The isopods are the most diverse crustaceans. These animals are found in terrestrial, freshwater, and saltwater habitats.

Decapoda

The decapods include many of the familiar crustaceans. They are mostly aquatic species.

Copepoda

The copepods are animals that are among the most numerous members of the marine and freshwater plankton community.

Cirrepedia

Barnicles are animals that are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings.

Subphylum: Myriapoda

Myriapods all have appendages that are uniramous (one main branch). The body is long with a distinct head. The have one pair of antennae. These animals also have a mandible.

Class: Chilopoda

These organisms are centipedes. They have one pair of jointed legs per segment. They have poison claws and are predators.

Class: Diplopoda

These organisms are millipedes. They have two pair or jointed legs per segment. (Two segments have fused together). They are herbivores.

Subphylum: Hexapoda

Hexapods all have 6 appendages, each pair are attached to a segment of the thorax. The body consists of a distinct head, thorax, and abdomen. They have one pair of antennae. These animals also have a mandible.

Class: Insecta

Insects are the most diverse of all arthropods. They may have been the cause of angiosperm diversity. Know the orders that are demonstrated here.

ArthropodaLevel of Organization Organ-system

Tissue Layers Triploblastic

Digestive System Alimentary Canal with modified mouth parts

Excretory System Nephridia

Circulatory System Open system with heart

Respiratory System Skin, gills, tracheae or book lungs

Nervous System Dorsal brain with ring connected to ventral cords

Body Cavity True

Asexual Reproduction Budding in some

Sexual Reproduction Usually Dioecious

Phylum: Echinodermata

The word Echinodermata means “spiny skin”. These animals demonstrate secondary radial symmetry as adults (evolved from bilateral symmetry back to radial symmetry) while the larvae stage still exhibits bilateral symmetry. They are probably more closely related to the vertebrates because of their deuterostome development. Unique to echinoderms is the water vascular system used for locomotion, feeding and food exchange.

Echinoderm Structures(P 126 Figure 7.100)

Oral Side: Side with mouthArboral Side: side without mouthMadreporite: opening into water vascular

systemAmbulacral Grooves: Radiating grooves that

contain tube feetPedicellariae: pincer-like organs on surface

(see compound microscope)Papillae: skin gills

Echinodermata ClassesClass Characteristics Examples

Asteroidea Pentaradial symmetry

Sea stars

Ophiuroidea Pentaradial symmetry

Brittle stars

Echinoidea Disk-shaped, no arms, spines

Sea urchin

Holothuroidea Cucumber-shaped, no arms, no spines

Sea cucumbers

Crinoidea Sessile, arms used for filter-feeding

Sea lillies

Class: Asteroidea

Sea stars have five arms that radiate from a central disc. They have an open ambulacral groove. The madreporite is on the aboral side. They contain both pedicellariae and dermal branchiae.

Class: Ophiuroidea

They have five thin arms radiating from a central disc. They have a closed ambulacral groove. The madreporite is on the oral side. They do not have pedicellariae or dermal branchiae.

The Sea urchins have no arms but have five rows of tube feet. They contain moveable spines. They have closed ambulacral grooves. They madreporite is on the aboral side. They contain pedicellariae and dermal branchiae. They have specialized jaw-like structures called an Aristotle’s lantern.

Class: Echinoidea

Class: Holothuroidea

Sea cucumbers are soft bodied animals with ambulacral areas with tube feet. They have an internal madreporite. They have no pedicellariae or dermal branchiae.

The sea lilies are attached to the substrate with many branched arms. They have open ambulacral grooves. They have no madreporite, pedicellariae or dermal branchiae.

Class: Crinoidea

Bipinnaria Larvae

The larvae form is evidence that this phyla has evolved radial symmetry from a bilateral ancestor. The larvae form is used for dispersal.

EchinodermataLevel of Organization Organ-system

Tissue Layers Triploblastic

Digestive System Alimentary canal

Excretory System Absent

Circulatory System Reduced if at all

Respiratory System Dermal branchiae, tube feet, respiratory tree

Nervous System No brain, nerve ring with radial nerves

Body Cavity True

Asexual Reproduction Regeneration

Sexual Reproduction Dioecious

Phylum: Chordata

The Phylum Chordatainclude animals that sometime in their life cycle have a notochord (for muscle attachment), a hollow dorsal nerve cord (to send nervous signals), pharyngeal slits (various functions) and a post-anal tail (movement). The three subphyla are Urochordata, Cephalochordata, and Vertebrata.

29

Subphylum: Urochordata

The Tunicates or Sea Squirts contain only the pharyngeal slits as an adult. They are usually sessile and use the pharynx for filter feeding.

30

Subphylum: Cephalochordata

The Lancelets contain all four chordate characteristics as an adult. They are usually found buried in the sand off our coast. They are considered to be the closest relative to vertebrates.

31

Subphylum: Vertebrata

The Vertebrates are animals with backbones. They contain all four chordate characteristics as an adult with some modifications. They are free-living.

32

What is a Fish?

Fish are aquatic vertebrates that are not a mammal, bird, or reptile (It isn’t a monophyletic group).There are the five major living groups of fish:

Hagfish (jawless)Lamprey (jawless)Cartilaginous FishLobe-finned FishRay-finned Fish

33

Superclass: Agnatha

The agnatha are animals without jaws and most lack paired appendages. Hagfishes may also lack eyes and a stomach. They are scavengers that enter natural openings on living and dead fish and mammals. Hagfish find their prey by a sense of smell. Hagfish can secrete large quantities of slime or mucus and can tie themselves into a knot which can also help release the slime.

34

Superclass: AgnathaThe agnatha are animals without jaws and most lack paired appendages. The adult lamprey feeds by attaching its mouth to a fish, secreting an anticoagulant into the host, and feeding on the blood and tissues of the host.

Lamprey swim upstream to spawn. They are called ammocoetes as larva and are found in burrows. The larva must go through a metamorphosis to become adults where the entire digestive system must be restructured.

35

Superclass: Gnathostomata

This superclass contains jaws which evolved from skeletal supports of the pharyngeal slits.

36

Class: Chondrichthyes

The class chondrichthyes all lack true bone and have a skeleton made of cartilage which is not a primitive characteristic. Their tough skin is covered with placoid scales. Males have a structure called claspers which aren’t seen in females.The two subclasses in this class are Elasmobranchii (the sharks, skates, and rays) and the Holocehphali (the ratfish)

37

Shark Reproduction

Male and female sharks can easily be told apart. Male sharks have claspers which are extensions of the pelvic fins used to transfer sperm. There is also three different types of shark egg development. They are:

Viviparity: the mother feeds the “babies” by a placenta

Oviparity: the mother deposits eggs in the ocean

Ovoviviparity: the eggs are retained in mom but without any nourishment from the

mother.

38

Order: SelachiformesGreat White Sharks

The Great White Shark measures up to 20 feet and can weigh up to 4200 lbs. They usually eat large bony fish, smaller sharks, dolphins, seals, and sea lions. They are found in almost all coastal and offshore waters between 54 to 75 degrees F. The Great White has been labeled a “man eater” but in the last 100 years more people have been killed by dogs in the U.S. than this shark. 39

Order: Selachiformes Leopard Sharks

The Leopard Shark measures up to 6.5 feet and can weigh up to 40 lbs. They usually eat bony fish, crustaceans, worms, and clams. They are found along the coast from Oregon to Baja California. The leopard shark is spotted as a juvenile in the shallows but usually lose their spots as they get larger and move to deeper water.

40

Order: Selachiformes Whale Sharks

The Whale Shark is the largest fish in the ocean and measures up to 66 feet and can weigh up to 7500 lbs. They usually are filter feeders eating enormous amounts of plankton. They are found in along the coast from Oregon to Baja California. The Whale shark can filter 6000 liters of water an hour.

41

Order: Selachiformes Hammerhead Shark

The Hammerhead shark measures up to 18 feet and can weigh up to 1000 lbs. They usually eat fish, rays, other sharks, cephalopods and crustaceans. They are found in tropical and subtropical waters along the shorelines. The shape of the head is thought to spread their receptors across a larger area making them 10 times more likely to detect prey.

42

Order: BatiformesSkates and Rays

Both skates and rays are flat bottom-dwelling organisms.Skates have a tiny caudal fin with no stinging spines, each pelvic fin is divided into two lobes and lay egg cases. Rays have a slender whip-like tail with stinging spines, each pelvic fin contains one lobe and give live birth.

43

Broad Skate

The broad skate is known to grow to be just under a meter in length. It is a deep-water skate found in the central and northern Pacific ocean. They feed on mollusks, crustaceans and fishes.

44

Manta Ray

The manta ray is the largest of the rays, with the largest known specimen having been about 7.6 m (about 25 ft) across. It ranges throughout all tropical waters of the world, typically around coral reefs. Manta rays are believed by some to have evolved from bottom-feeding ancestry, but have adapted to become filter feeders in the open ocean

45

Guitarfish

The guitarfish are mainly found in tropical and temperate waters, traveling in large schools. Most adult guitarfishes reach five or six feet in length. These fish are bottom feeders, preferring small crustaceans.

46

Order: ChimaeriformesChimaeras

Chimaeras differ from sharks in that their upper jaws are fused with their skulls; they have separate anal and urogenital openings; and they lack the many sharp and replaceable teeth of sharks, having instead a few large permanent grinding tooth plates. They are often called ratfish or rabbit fish. They are found in cold water often at great depths. The diet consists primarily of benthic invertebrates. The tooth plates are used to crush hard-bodied prey such as crabs, clams, and echinoderms.

47

OsteichthyesThe “Osteichthyes” all have a skeleton made of true bone. Their skin is covered with ctenoid scales. They also have an operculum (a hard covering over the gills), which helps them breathe without having to swim. They also have a swim bladder which helps the body create a neutral balance between sinking and floating. There are two classes in this group: the Class: Sarcopterygii, the Lobe-finned fish and the Class: Actinopterygii the Ray-finned Fish

48

Sarcopterygii – Lobe-finned FishSubclass: CoelacanthimorphaCoelocanths are lobe-finned fish with the pectoral and anal fins on fleshy stalks supported by bones, and the tail is divided into three lobes. Coelacanths also have a special electroreceptive device called a rostral organ in the front of the skull, which probably helps in prey detection.

Coelacanth populations have been found near Indonesia and South Africa. Coelacanths are opportunistic feeders, hunting cuttlefish, squid, snipe eels, small sharks, and other fish.

49

Sarcopterygii – Lobe-finned FishSubclass: Dipnoi

Lungfish are fresh water lobe-finned fish. Lungfish are best-known for retaining primitive characteristics, including the ability to breathe air, Today, they live only in Africa, South America, and Australia. African and South American lungfish are capable of surviving seasonal desiccation of habitats by burrowing into mud and estivating throughout the dry season. They have a diet of fish, insects, mollusks, worms, crustaceans, and plant material.

50

Infraclass: Holosteri

In this infraclass, all of the fish are considered to be primitive fish. They are found in brackish conditions. They can use their swim bladders to obtain extra oxygen

51

Infraclass: HolosteriOrder: Lepisoteriformes

Gars inhabit fresh, brackish, and occasionally marine, waters of eastern North America, Central America, and the Caribbean islands. They have a swim bladder that opens to the pharynx that can function as a lung and most gars surface periodically to take a gulp of air, doing so more frequently in stagnant or warm water when the concentration of oxygen in the water is low

52

Infraclass: HolosteriOrder: Amiiformes

Amia's are also called Bowfin or Dog fish. Amia’s distribution is restricted to eastern North America. Amia's swim bladder functions much like a lung, allowing this fish to gulp air when dissolved oxygen levels become dangerously low in the weed beds where it lives. They are primarily fish eaters, although crayfish can make up a substantial proportion of the diet, and frogs are also consumed.

53