Chelicerata Flashcards
1
Q
What animals does Chelicerata contain?
A
It is a subdivision of Arthropoda
Horseshoe crabs
Sea spiders
Arachnids
2
Q
Chelicerata anatomy
A
- Two main tagmata: prosoma and opisthosoma
- Prosoma: formed by tagmosis of 6 embryonic segments, many have a carapace
- Opisthosoma: formed by tagmosis of up to 12 embryonic segments plus post-anal telson (last segment of abdomen), may be undivided (spiders) or segmented (scorpions)
3
Q
Appendages of the Chelicerata prosoma
A
- No antennae or true mandibles
- 1 pair of chelicerae (jointed feeding or mouth-parts known as pincers or fangs)
- 1 pair of pedipalps (usually sensory, can be pincers)
- 4 pairs of walking legs
4
Q
Appendages of the opisthosoma (reduced but still present)
A
- Book-gills (for locomotion and respiration) in horse-shoe crabs
- Spinnerets (for silk manipulation) in spiders
5
Q
What is the scientific name for sea spiders?
A
Pycnogonids
6
Q
Features of pychnogonids (sea spiders)
A
- Marine arthropods
- 1300 species
- 4 pairs of very long legs
- Commensals or ectoparasites of invertebrates
- Small body
- Digestive system that extends into their legs
7
Q
What is the scientific name for horseshoe crab?
A
Xiphosura
8
Q
Features of xiphosura (horseshoe crab)
A
- 4 living species
- Large carapace protects the prosoma
- The opisthosoma is fused
- At the base of each walking leg is a structure called a gnathobase (jaws)
- 480 Ma fossils found that are ancestors
9
Q
What is the scientific name for sea scorpions?
A
Eurypterids
10
Q
Features of Eurypterids (sea scorpions)
A
- Extinct, found in the Ordovician to Permian periods (460-248 Ma)
- Prosoma had a head shield
- Unfused opisthosoma
11
Q
Scorpions
A
- Widespread arachnids
- Venomous telson
- 1730 species
- All tropical and warm environments
- 4 pairs of walking legs
- 2 chelicerae
- 2 pedipalp
12
Q
Spiders
A
- 45,700 species
- Very disparate ecologies
- Spin silk
- Take down prey with venom
- Loss of visible external segmentation of opisthosoma
- 4 pairs of walking legs
- Pedipalp for sensation and sperm transfer
- Orientation of chelicerae: plesiomorphic (forward-facing) or apomorphine (derived, lateral formation)
- Basal part of chelicerae has poison gland
- Book lung with trachea for respiration
- Haemocoel containing harmocyanin carries oxygen
- Spinnerets - opisthosomal appendages for spinning silk
- 8 eyes in 4 pairs
- Main eyes and secondary eyes
13
Q
Features of spinnerets
A
- Silk comes out of spigots
- Spools used to manipulate the silk
- Multiple silk types produced by different glands for different purposes
14
Q
Features of a web
A
Huh (middle)
Frame (edge)
Catching spiral
15
Q
Purpose of secondary eyes in spiders
A
Have a reflective tapetum lucidum, which makes them good in low light level vision and for movement detection
