Leech Infestation Patterns between Native and Invasive Freshwater Turtles: Implications for Invasion Success

Area of Science:

• Ecology
• Invasive Species Biology
• Parasitology

Background:

• Alien species introductions are increasing globally, necessitating understanding of establishment drivers.
• Parasites are often absent in invasive species, potentially facilitating their success (enemy release hypothesis).
• Freshwater turtle-leech interactions are crucial for understanding invasion dynamics.

Purpose of the Study:

• Investigate leech parasitism in native and invasive freshwater turtles in southern Brazil.
• Assess how host species, sex, body size, and body region influence leech prevalence and intensity.
• Evaluate the role of enemy release in the invasion success of Trachemys sliders.

Main Methods:

• Captured 62 freshwater turtles using traps over a period of co-occurrence.
• Identified native (Phrynops geoffroanus, Hydromedusa tectifera) and invasive (Trachemys dorbigni, Trachemys scripta elegans) species.
• Assessed leech prevalence and infestation intensity across host characteristics and body regions.

Main Results:

• Native turtles had an 18-fold higher prevalence of leech infestation compared to invasive sliders.
• Trachemys dorbigni showed no leech infestation; Trachemys scripta elegans had very low prevalence.
• Leech infestation probability increased with turtle body size, with hind limbs being most affected.

Conclusions:

• Reduced ectoparasitism on invasive Trachemys species supports the enemy release hypothesis.
• Lack of natural enemies may be a key factor enabling slider invasions.
• Findings provide baseline data for future research on slider invasion ecology.