Structural and biomechanical adaptations of arthropod parasites to the life on marine mammals
Arthropods are the most successful animal phylum, representing over 80% of known species. Their evolutionary success is shown in their wide range of forms and ecological strategies, enabling them to inhabit nearly all environments. The marine realm poses major challenges – high salinity, strong currents, low oxygen, high pressure, and temperature shifts – yet arthropods have successfully colonized it, often through parasitism. This study examines the biomechanical and structural adaptations of three phylogenetically distinct marine arthropod parasites: seal lice (Echinophthirius horridus), nasal mites (Halarachne halichoeri, Orthohalarachne attenuata), and whale lice (Isocyamus deltobranchium). All live on diving marine mammals that reach depths of up to 1,500 m, exposing the parasites to extreme conditions that demand specialized adaptations. Using multiple methods, we identify key adaptations in five morpho-functional domains: (i) Morphology – niche-specific body forms and material properties, including flattening, miniaturization, sclerotization, mineralization, and resilin-rich areas. (ii) Attachment – anchoring systems such as snap-hooks, friction pads, proteinaceous adhesives, piercing claws, hooking structures, and controlled adhesive pads. (iii) Locomotion – movement suited to host surfaces and moisture levels. (iv) Respiration – cuticular gas exchange, with some taxa showing sealable tracheae or gill-like features. (v) Drag reduction – streamlined shapes and vortex-generating setae that reduce drag in dynamic flow. These results highlight the ecological plasticity of marine parasitic arthropods and offer a functional basis for understanding host–parasite co-evolution, as well as inspiration for applications in materials science and engineering.
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