To avoid or eliminate: cestode infections in copepods.

Area of Science:

• Parasitology
• Ecology
• Host-Parasite Interactions

Background:

• The outcome of parasite infections is determined by complex interactions between host and parasite.
• Three critical stages influence infection outcome: parasite establishment, host avoidance, and host immune elimination.
• The copepod Macrocyclops albidus serves as the intermediate host for the cestode Schistocephalus solidus.

Purpose of the Study:

• To investigate the distinct phases of parasite infection in Macrocyclops albidus by Schistocephalus solidus.
• To differentiate the factors influencing parasite establishment versus parasite growth and survival within the host.
• To identify key interaction periods that dictate the overall success of the host-parasite relationship.

Main Methods:

• Studied the establishment and growth phases of Schistocephalus solidus infection in Macrocyclops albidus separately.
• Analyzed the influence of host characteristics (size, sex) and parasite characteristics (sib-groups) on infection establishment.
• Monitored parasite disappearance during the growth phase and correlated it with host and parasite factors.

Main Results:

• Host characteristics significantly impacted parasite establishment; smaller copepods and males were more susceptible and had lower survival rates.
• Parasite sib-groups exhibited varying infectivity, influencing establishment success.
• Parasite disappearance during the growth phase was not linked to host traits or parasite sib-group, suggesting intrinsic parasite mortality.

Conclusions:

• Parasite establishment is a critical phase influenced by host and parasite attributes.
• Host immune response during the parasite growth phase appears less critical than initial establishment.
• Crucial host-parasite interactions determining infection outcome occur during the brief period between parasite ingestion and gut penetration.