Phylum Arthropoda arthro joint poda foot Habitat arthropods

Phylum Arthropoda

• arthro = joint; poda = foot

• Habitat: arthropods are found in all environments. • Numbers: Arthropods are the most successful of any animal group. This is mainly due to the success of insects, which has more than a million different species.

Body Plan • Arthropods have a segmented body with paired jointed appendages that provide excellent movement for walking, swimming, flying, grabbing, fighting, digging and biting just to name a few.

• In most arthropods the body is divided into a head, abdomen and thorax.

• Exoskeleton: The outside skeleton of arthropods is made of chitin which protects the soft body of this animal and prevents water loss allowing them to live successfully on land. • Arthropods must molt because their exoskeletons don’t grow with them • Symmetry: Bilateral

Classes • • Class Merostomata Class Arachnida Class Insecta Class Chilopoda and Diplopoda

Class Merostomata

Horseshoe Crab • are an ancient group, but only 5 species exist today. • They are called Horseshoe crabs because the dorsal plate which covers their body bears some resemblance to a horseshoe

• Horseshoe crabs live mostly partly buried in the mud of the sea floor where they hunt for small animals, worms, crustaceans and even fish which they eat. • As well as pushing through the mud they can walk on their legs and even swim

• A distinctive part of a Horseshoe crabs morphology is the long stiff caudal spine. • While this may look dangerous it is not a weapon and serve only to help the animal in forward movement and to right it if it gets turned on its back, an important function as none of its limbs reach beyond the edge of the carapace

Structure • The whole body of the animal is covered, and protected by two dorsal plates called a carapace. The carapace is said to bear two simple eyes • Beneath the horseshoe shaped part of the carapace is the cephalothorax which bears the animals walking and feeding legs

• There are five pairs of walking legs the first of which are sometimes called the pedipalps (feeding legs), the first four pairs of walking legs have pincers

• The abdomen consists of 9 fused segments and is protected by the abdominal dorsal plate which hinges with the cephalothoracic plate.

• the legs consist of coxa, trochanter, femur, tibia and two tarsal segments. The first pair (of 6) of abdominal legs have the openings of the reproductive organ in them.

• The last five of the abdominal legs have gills on them. These gills are called book gills because each one consists of a series 150 to 200 flat plates laid one over the other like the pages of a book, these are the animals organs of gaseous exchange

Reproduction • They migrate to certain shallow coastal waters • Males select a female and cling onto her back. The female then digs a hole about 15 cms deep in the sand in the tidal zone. • She lays up 1, 000 eggs in this hole and the male releases his sperm onto them so that they can be fertilized. • The female then covers the eggs with sand which protects them from the action of the waves while allowing them to be warmed by the sun.

Class Arachnida

Body plan • All adult arachnids have 8 legs • two further appendages are the chelicerae (for feeding or defense), and the pedipalps (for feeding, locomotion, and/or reproduction) • Their body is organized into two tagmata called the prosoma or cephalothorax , and the opisthosoma or abdomen

• have an exoskeleton, and they also have an internal structure of cartilage like tissue called the endosternite, to which certain muscle groups are attached • Ticks and mites have 1 body part all fused together

• No antennae, simple eyes (usually 8) • Use book gills for respiration

Spiders • All spiders produce silk, a thin strong protein strand extruded by the spider from spinners most commonly found on the end of the abdomen

Scorpions

Scorpion Anatomy 1 = Cephalothorax or Prosoma; 2 = Abdomen or Mesosoma; 3 = Tail or Metasoma; 4 = Claws or Pedipalps 5 = Legs; 6 = Mouth parts or Chelicerae; 7 = pincers or Chelae; 8 = Moveable claw or Tarsus; 9 = Fixed claw or Manus; 10 = Sting or Aculeus ; 11 = Telson

• Scorpions are opportunistic predators of small arthropods, although the larger kinds have been known to kill small lizards and mice.

• The large pincers are studded with highly sensitive tactile hairs, and the moment an insect touches these, they use their chelae (pincers) to catch the prey. • Depending on the toxicity of their venom and size of their claws, they will then either crush the prey or inject it with neurotoxic venom

Reproduction • Most scorpions reproduce sexually • After they are born they are carried on its mother's back until the young have undergone at least one moult. • Before the first moult, they cannot survive naturally without the mother, since they depend on her for protection and to regulate their moisture levels

Ticks

• Feed on blood • Are external parasites • Cause diseases such as: Lyme disease, Colorado tick fever, Rocky Mountain spotted fever, African tick bite fever

Class Insecta

• They are the most diverse group on the planet. • Found all over the world in all types of environments

Body plan • chitinous exoskeleton • a three-part body (head, thorax, and abdomen) • three pairs of jointed legs • compound eyes • one pair of antennae

Growth • growth is an especially important characteristic of insects. • In some, hatching eggs produce miniature adults, which to grow must shed their exoskeleton in a process called ecdyisis. • In almost 90% of insect species, however, newly hatched young are completely different in appearance from adults.

• All insects must go through metamorphosis, a biological process of development • 2 types of metamorphosis – Incomplete – complete

Incomplete • change gradually by undergoing a series of molts. • An insect molts when it outgrows its exoskeleton, which does not stretch and would otherwise restrict the insect's growth.

Complete • the insect changes in four stages, an egg or embryo , a larva , a pupa, and the adult • Ex: a butterfly

Class Chilopoda and Diplopoda

• Class Chilopoda is centipedes • Name comes from Latin prefix centi, "hundred", and pes, pedere, “foot”

• Despite the name, centipedes can have a varying number of legs from under 20 to over 300. • Centipedes have an odd number of pairs of legs, e. g. 15 or 17 pairs of legs (30 or 34 legs)

• Class Diplopoda is millipedes • The name "millipede" is a compound word formed from the Latin roots mille ("thousand") and pes ("foot").

• Despite their name, no known millipede has 1, 000 legs • Common species have between 36 and 400 legs