Subphylum Chelicerata

Subdecks (1)

Cards (93)

  • Named after the modification of chelicerae and the pedipalps
  • Chelicerae
    first pair of appendages; feeding structures
  • Pedipalps
    second pair of appendages; has various functions (e.g.) sensory, reproduction, etc.)
  • Body segments
    cephalothorax or prosoma abdomen or opisthosoma (fused)
  • Antennae absent
  • Four pairs of walking appendages
  • Class Merostomata
    • Aquatic chelicerates (sand burrowing horseshoe crabs)
    • Body segments: cephalothorax and abdomen
    • Dorsal side: prosoma covered by a carapace (hard shell); two lateral eyes, a caudal tail or telson
    • Ventral side: mout apparatus contain the chelicerae; attached to the cephalothorax are 4 pairs of appendages
    • Abdomen: two genital pores; six gill pairs
  • Horseshoe crab (Dorsal view) Parts
    A) Prosoma
    B) Two lateral eyes
    C) Cephalothorax
    D) Caudal tail
    E) Telson
  • Horseshoe crab (ventral view) parts
    A) Book Gills
    B) Genital Pores
    C) Chelicera
    D) Appendages
  • Phylum: Arthropoda
    Subphylum: Chelicerata
    Class: Merostomata
    Order: Xiphosura
    Family: Limulidae
    Genus: Limulus
  • Development of Merostomata
    Centrolecithal eggcleavagetrilobite larva → from 13-14 instars → adult
  • Habitat
    marine soft bottoms & shallow waters
  • Prosoma covered by large horseshoe-shaped carapace (convex dorsally)
  • 2 eye pairs: large dorsolateral pair; small dorsomedial pair; both on carapace
  • Mouth is posterior to labrum (upper lip), with trisegmented chelicerae pair on each side
  • 6pairs of cephalothoracic appendages
    First four pairs, fifth pair, chilaria
  • Opisthosoma: unsegmented containing 6 short mobile spines at the posterior end, has 6 pairs of appendages with first pair forming the genital operculum
  • Telson: long triangular spine-like tail or caudal spine (not a true telson for horseshoe crabs (lacks anal opening)
  • Digestion
    extracellular, intracellular within the hepatic caeca
  • Excretion & Osmoregulation
    4 pairs of coxal glands- Common saclike chambers, coiled tubules, bladder, and excretory pore (located at base of last pair of walking legs)
  • Reproduction
    Dioecious with external fertilization