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A ATHROPODA. SUBPHYLUM CHELICERATA. Defining Characteristics. chelicerates have segmented bodies with jointed limbs, all covered in a cuticle made of chitin and proteins
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AATHROPODA SUBPHYLUM CHELICERATA
Defining Characteristics • chelicerates have segmented bodies with jointed limbs, all covered in a cuticle made of chitin and proteins • cheliceratebauplan 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 • 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 s
SUBPHYLUM CHELICERATA • Class Merostomata • Class Pycnogonida • Class Arachnida
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 crabs • The cephalothorax & abdomen are covered by a hard non-jointed carapace.
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 Defining 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 • ( exomeans "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 • They have paired, jointed appendages • (parts that are attached to the main body) • Present of hardened exoskeleton • ( exomeans "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.