Cut and Taste: Functional Morphology of the Feeding Apparatus of the Longhorn Tick Haemaphysalis longicornis (Arachnida: Ixodida)

ABSTRACT With specialized piercing and sucking mouthparts, hard ticks (Ixodidae) are able to penetrate, anchor and suck blood from their vertebrate hosts. In the process, some species vector diseases that threaten human health and livestock. Historically, much work has been done to characterize their mouthpart anatomy primarily through dissections and histology. Advances in imaging techniques have led to more recent work exploring stages of the tick feeding process including salivation, suction, as well as penetration. However, a comprehensive overview of the internal and external anatomy of the mouthparts, not just in females but also in males, is still lacking. These mouthparts relate to a tick's ability to vector parasites. In this study, we focus on a medically and agriculturally important tick, Haemaphysalis longicornis, native to East Asia, which has spread beyond its original range. Using 3D modeling and confocal laser scanning microscopy, we document mouthpart and head anatomy, with particular focus on components related to penetration. Our results show that: (i) tick mouthparts are composed of different materials with the hypostome and chelicerae showing resilin-dominated regions, whereas the palps are especially strongly sclerotised; and (ii) ticks have musculature that might be capable of generating hydraulic pressure to drive cheliceral protrusion. Together, these findings highlight how a morphological perspective is crucial to understanding tick mouthparts and their function in blood feeding.