Spiders Flashcards
(24 cards)
Araneae is an order the class what..?
Class Arachnida
Subphylum chelicerate and phylum arthropoda
What are araneae?
Spiders, scorpions, mites+ticks, horse shoe crabs, sea spider
Spiders constitute 40000 out of 85000 chelicerates
Chelicerates have
Two body segments, chephalothorax and abdomen, chelicerae, compound eyes
Arachnids have
Fused cephalothorax with carapace, pedipalps, book lungs, four pairs of legs, carnivorous with liquid diet
Spiders have
Silk, pedicel, poison glands, sperm transfer via pedipalp
What are chelicerae
Mouthparts for feeding
Spiders cannot digest solid food
Often associated with venom
Hardening of tips with zinc ions
Feeding:venom
Many produce venom
Diversity in chemical composition and effect
30 species have venom known to kill humans
Venoms can contain e.g. lytic peptides, enzymes, neurotoxins
About the book lung
A feature of arachnids
Basal spiders have two pairs of book lungs
More derived spiders replace 1 pair of book lungs with separate trachea
Silk
Biopolymers - like rubber, keratin, etc
Fibrous proteins
Primary sequence forms polymer chains held together by amide bonds
H bonds form between chains
Primary sequences generally contain high proportions of what amino acids
Glycine and alanine
Long proteins are folded during silk spending and protein structure controlled by primary sequence and folding during spinning
What is silk spinning
Pulling of silk strand begins the spinning process, and loss of water during spinning causes protein to change shape and H-bond to itself = protein denaturation
Silk is stored as what
Stored as a liquid in the gland and forms a dry fibre during spinning
Silk and feeding
Radial threads are strong and tough, to absorb prey impact energy without breaking
Capture spiral is stretchy and sticky for prey retention
Orb webs function to catch and retain prey - sit and wait predatory strategy
Silk and sensory system
Spiders are vibration specialists and can control vibration propagation in orb webs
Spiders have
Air borne vibration sensors - trichobothria
Substrate-borne vibration sensors - slit sensilla
Both are abundantly present on 8 legs
Slit sensilla sensitive to substrate vibration
Silk and reproduction
Used by females to wrap up eggs
Used by males to make a sperm web - sperm is deposited onto web then transferred to pedipalps with a sperm reservoir
Pedipalp inseminates female
Silk and locomotion
Spiders lay down silk as safety dragline
Araneomorph dragline silk and take spider’s own weight
Jumping spiders use silk to stabilise jumps
Silk and dispersal
Spiderlings can use silk to balloon, silk line acts as a sail to allow spiders to fly
Enables dispersal away from egg laying site
Spider diversity
Widely distributed (except Antarctica) Numerous - one hectare of UK meadowland contains 5 million spiders
Sexual dimorphism
Sexually dimorphic in appearance e.g. peacock spiders and golden orb weavers
Differences in silk production and behaviour
Similarites
Body form does not vary much
What are the spider suborders
Mesothelae, Mygalomorphae, Araneomorphae
What is the difference between Mygalomorph and Araneomorph
Mygalomorph have parallel fangs and araneomorph have opposed fangs (and have piriform silk), possess a silk comb and undergo ballooning
Araneopmorph evolution
RTA clade inc. jumping, crab, and wolf spider families
Orbiculariae incl. orb weavers, money and cobweb spider families
