AATHROPODA

SUBPHYLUMCHELICERATA

Defining Characteristics

• chelicerates have segmented bodies with jointed limbs, all covered in a cuticle made of chitin and proteins

• chelicerate bauplan consists of two tagmata, the cephalothorax and the abdomen, except that mites have lost a visible division between these sections

• Chelicerate are the only appendages that appear before the mouth

Defining Characteristics

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•has the open circulatory system typical of the arthropods, in which a tube-like heart pumps blood through the hemocoel, which is the major bod cavity

•Marine chelicerates have gills, while the air-breathing forms generally have both book lungs and trachea

•Absence of antennae

•Marine species are horseshoe crabs, sea spiders , & mites

SUBPHYLUM CHELICERATA

Class Merostomata

Class Pycnogonida

Class Arachnida

Class MerostomataDefining characteristics:

-Appendages on the abdomen are flatted and modified for gas exchange as “book gills”. -Terminal portion of body drawn out into an elongated site.•Only four living species: the horseshoe crabs•The cephalothorax & abdomen are covered by a hard non-jointed carapace.

Class Merostomata

REPRODUCTION

Unusual in arthropods, it has gonochoric and have true external fertization

In male gonadal network is formed. - duct - testes being attached as small alveoli. In female - ovary forms all the branches.

CLASS PYCNOGONIDA

Class PYCNOGONIDADefining characteristics:

- Body is not divided into distinct regions. - Unique proboscis at anterior end, with an opening at its tip. - Includes the sea spiders, several of which are common in our area. - Feed on soft bodied invertebrates, hydroids, bryozoans colonies & sponges.

Sea Spiders

Have a long proboscis for feeding & a digestive tract with gonads extending into walking legs.

Difficult to discern the cephalothorax & abdomen Anterior appendages may bear cheliceras that

group pieces food.Ovigers-structures used by makes to carry eggs on

body When eggs are mature they are deposited in a

hydroid colony

CLASS ARACHNIDA

•They have paired, jointed appendages (parts that are attached to the main body)• Present of hardened exoskeleton ( exo means "outer")• Segmented (divided into parts) body, and a well-developed head. • Their body consists of two main parts: a fused head and thorax, and an abdomen

CLASS ARACHNIDA

CLASS ARACHNIDA

• They have paired, jointed appendages • (parts that are attached to the main body)• Present of hardened exoskeleton • ( exo means "outer")• Segmented (divided into parts) body, and • a well-developed head. • Their body consists of two main parts: a • fused head and thorax, and an abdomen

Most arachnids live on land

They breathe by means of book lungs (so called because their thin membranes are arranged like the pages of a book)

by tracheae (small tubes that distribute air from the outside throughout the body)or both.