2 Defining Characteristics chelicerates have segmented bodies with jointed limbs, all covered in a cuticle made of chitin and proteinschelicerate bauplan consists of two tagmata, the cephalothorax and the abdomen, except that mites have lost a visible division between these sectionsChelicerate are the only appendages that appear before the mouth
3 Defining Characteristics 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 cavityMarine chelicerates have gills, while the air-breathing forms generally have both book lungs and tracheaAbsence of antennaeMarine species are horseshoe crabs, sea spiders , & mitess
4 SUBPHYLUM CHELICERATA Class MerostomataClass PycnogonidaClass Arachnida
5 Class Merostomata Defining 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 crabsThe cephalothorax & abdomen are covered by a hard non-jointed carapace.
9 REPRODUCTIONUnusual in arthropods, it has gonochoric and have true external fertizationIn male gonadal network is formed.- duct- testes being attached as small alveoli.In female- ovary forms all the branches.
11 Class PYCNOGONIDA Defining characteristics: - Body is not divided into distinct regions.- Unique proboscis at anterior end, with anopening at its tip.- Includes the sea spiders, several of whichare common in our area.- Feed on soft bodied invertebrates,hydroids, bryozoans colonies & sponges.
12 Sea SpidersHave a long proboscis for feeding & a digestive tract with gonads extending into walking legs.Difficult to discern the cephalothorax & abdomenAnterior appendages may bear cheliceras that group pieces food.Ovigers-structures used by makes to carry eggs on bodyWhen eggs are mature they are deposited in a hydroid colony
13 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, anda well-developed head.Their body consists of two main parts: afused head and thorax, and an abdomen
16 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, anda well-developed head.Their body consists of two main parts: afused head and thorax, and an abdomen
17 Most arachnids live on land They breathe by means ofbook 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.