Host-parasite immune dynamics in the range-expanding invasive cane toads (Rhinella marina)

• Grant number: 23/06734-8
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate (Direct)
• Effective date (Start): September 25, 2023
• Effective date (End): September 24, 2024
• Field of knowledge: Biological Sciences - Physiology - Compared Physiology
• Principal Investigator: Fernando Ribeiro Gomes
• Grantee: Felipe Rangel Floreste
• Supervisor: Lee Ann Rollins
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Research place: University of New South Wales (UNSW), Australia
• Associated to the scholarship: 21/14134-5 - Modulation of immune system gene expression in Rhinella toads submitted to an immunological challenge with lipopolysaccharide (LPS) and heat-killed bacteria (Aeromonas hydrophila), BP.DD

Abstract

Biological invasions can unfold a new layer of complexity when parasites are introduced along with their hosts. Cane toads (Rhinella marina) are native to Central and South America but were introduced in Australia as an attempt to control crop pests. However, the situation got out of control. The invasive cane toads have been expanding westward, carrying along the South American lungworm Rhabdias pseudosphaerocephala and posing a dangerous threat to native Australian herpetological fauna. Interestingly, the cane toad populations in Australia show a spatial differentiation in aspects of their immune function and susceptibility to lungworms: toads in the invasion front (Western populations) show lower metabolic rates during an immune challenge and higher susceptibility to lungworm infection than their core range counterparts (Eastern populations). Still, the mechanisms underlying these differences are underexplored. Our proposal aims to investigate the genetic-driven differences in the immune response along the expansion and core range of cane toads in Australia. For that, we will infect R. marina offspring from three families in the toads' distribution (Eastern, Central, and Western) with R. pseudosphaerocephala larvae and track helminth-elicited cytokine mRNA levels (IFN-y, IL-4, IL-5, IL-9, IL-10, IL-13, IL-25, and IL-33), the plasma bacterial killing ability (BKA), and neutrophil to lymphocyte ratio (NLR) in four time-points post-infection within a 30-days timeframe. We expect to see lower intensity in immune response in infected Western toads, while we expect that infected Eastern toads will exhibit the highest intensity in those features. In addition, we expect that parasitized Western toads will down-regulate the cytokine gene expression and return to baseline values faster than intermediate and Eastern toads. (AU)