Monogenean anchor morphometry: systematic value, phylogenetic signal, and evolution

Area of Science:

• Parasitology
• Evolutionary Biology
• Systematics

Background:

• Monogenean parasite anchors are crucial attachment appendages.
• Anchor morphometry provides insights into parasite evolution and systematics.
• Geometric morphometrics combined with molecular data can address biological questions.

Purpose of the Study:

• To analyze anchor morphometry in 13 Ligophorus species infecting two marine fish hosts.
• To investigate phylogenetic signals and evolutionary constraints in anchor shape and size.
• To test the Rohde-Hobbs hypothesis regarding anchor morphology and male copulatory organs.

Main Methods:

• Geometric morphometrics applied to 530 anchor specimens.
• Phylogenetic analysis using 28S, 18S rRNA, and ITS1 sequences.
• Statistical analyses including principal component analysis, cluster analysis, and phylogenetic regression.
• Development of the monogeneaGM R package for integrated data analysis.

Main Results:

• 12 of 13 Ligophorus species were discriminated by anchor shape.
• Significant phylogenetic signal detected in anchor shape, revealing new morphological characters.
• Anchor size and shape correlated significantly, indicating evolutionary constraints.
• Anchors function as integrated modules, with male copulatory organ morphology correlating with anchor traits.

Conclusions:

• Monogenean anchors are tightly integrated structures with shape variation strongly correlated with phylogeny.
• Anchor morphometry is a valuable tool for systematic and evolutionary studies of monogenean parasites.
• The monogeneaGM R package facilitates research on monogenean geometric morphometric data.