Putative hybrids between two Anisakis cryptic species: molecular genotyping using High Resolution Melting

Area of Science:

• Marine biology
• Parasitology
• Molecular genetics

Background:

• The genus Anisakis includes species linked to human anisakiasis.
• Hybridization between Anisakis simplex sensu stricto and Anisakis pegreffii has been debated, with limited evidence of adult hybrids.

Purpose of the Study:

• To identify anisakid nematodes in Stenella coeruleoalba.
• To investigate hybrid Anisakis forms using molecular techniques.
• To re-evaluate the existence and evolutionary role of Anisakis hybrids.

Main Methods:

• PCR-restriction fragment length polymorphism (PCR-RFLP) of nuclear ribosomal ITS.
• High-resolution melting (HRM) analysis.
• Direct sequencing.

Main Results:

• Anisakis simplex s.s., Anisakis pegreffii, heterozygous genotypes, and Anisakis physeteris were identified.
• HRM analysis confirmed the presence of A. simplex s.s., A. pegreffii, and hybrid individuals.
• A new record of adult Anisakis hybrids was documented in definitive hosts.

Conclusions:

• The documentation of adult hybrids supports their existence and prompts further debate on their evolutionary significance.
• The assumption of reproductive isolation between A. simplex s.s. and A. pegreffii is challenged.
• Further population genetic studies and alternative molecular markers are recommended for adult anisakids.