Parasitoids

Amanda ActonBiology 4800

What is a Parasitoid?

• A type of parasite that is attached or lives within its host for a significant portion of its life-cycle

• A parasite that kills and often consumes its host

• Parasitoid is usually similar in size to host• Adult stage is free living• Typically causes alterations in host behaviour

Types of Parasitoids

• Idiobiont• Koinobiont

• These can be further divided into – Endoparasitoids– Ectoparasitoids

Parasitoid Example

• Hymenoepimecis argyraphaga - wasp• Plesiometa argyra - spider

• System has been studied in Costa Rica by William G. Eberhard

Webs of Infected Spiders

• Create cocoon webs on the night that they are to be killed

• Central portion is full• Frame lines shorter and

closer to hub• Smaller diameter with

shorter and fewer anchor lines

How the Behaviour Changes

• Spiders normally break, reel up and replace lines or break and re-attach lines

• Spiral and sticky spiral lines are not produced• The central hub portion was always intact• The initial construction changes in the way the

web is framed.• Construction occurs in bursts

Why Do These Changes Occur?

• Adaption to increase parasite reproduction/survival

Can These Changes be Reversed?

• Yes and No• Of 22 spiders that have had larvae removed:

• 4 did not make webs that night• 3 made cocoon webs• 1 was a cocoon web with extra hubs• 13 made simple webs full of loose fluff• 1 orb web, but the hub was not removed

• No spiders died that night, and as night progress, webs become more orb-like

What Causes Behavioural Changes?

• The adult female wasp injecting a product when she oviposits?

• The maturing process of the larva on the spider?

Questions?