1. Subphylum Chelicerata
Class Merostomata
Class Pycnogonida
Subphylum Chelicerata

2. Subphylum Chelicerata
Defining characteristics
Absence of antennae
Contains three classes, most of the animals are terrestrial and freshwater
Marine species are horseshoe crabs, sea spiders, and mites
Subphylum Chelicerata

3. Chelicerate Segmentation
Cephalothorax –usually has 6 pairs of appendages
First pair – chelicerae
Second pair – pedipalps
Both function as mouthparts
The rest are walking legs
Subphylum Chelicerata

4. Subphylum Chelicerata
Taxonomic Summary
Phylum Arthropoda
Subphylum Chelicerata
Class Merostomata
Class Pycnogonida
Subphylum Chelicerata

5. Subphylum Chelicerata
Class Merostomata
Defining characteristics
Appendages on the abdomen are flattened and modified for gas exchange as “book gills”
Terminal portion of body drawn out into an elongated spike
Only 4 living species; the horseshoe crabs
Subphylum Chelicerata

6. Subphylum Chelicerata
Horseshoe Crab Habits
The cephalothorax and abdomen are covered by a hard non-jointed carapace
Subphylum Chelicerata

7. Merostomata Appendages
Possess an anterior chelicerae and 5 pairs of walking legs
In males the first pair of walking appendages are modified for grasping the female during reproduction
All the legs (except the last pair) bear pinchers for manipulating food
Walking legs bear gnathobases on basal part of legs, which aid in food manipulation
Subphylum Chelicerata

9. Subphylum Chelicerata
Respiration
The abdomen bears the book gills and is endowed with blood
The blood or components of it are used in pharmaceutical research
Subphylum Chelicerata

10. Subphylum Chelicerata
Reproduction
Subphylum Chelicerata

11. Subphylum Chelicerata
Class Pycnogonida
Defining characteristics
Body is not divided into distinct regions
Unique proboscis at the 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, bryozoan colonies, and sponges
Subphylum Chelicerata

12. Subphylum Chelicerata
Sea Spiders
Have a long proboscis for feeding and a digestive tract with gonads extending into the walking legs
Difficult to discern the cephalothorax, and abdomen
Anterior appendages may bear cheliceras that grasp pieces food
Subphylum Chelicerata

13. Subphylum Chelicerata
Sea Spiders
Ovigers – structures used by males to carry eggs on the body
When eggs are mature they are deposited in a hydroid colony
Subphylum Chelicerata