From whom did the ticks originate? - briefly
Ticks evolved from ancient chelicerate ancestors that diverged during the Paleozoic era, branching off from early predatory mites. Their lineage traces back to primitive arachnids that gave rise to modern parasitic species.
From whom did the ticks originate? - in detail
Ticks belong to the subclass Acari, order Ixodida, which diverged from other arachnids during the early Paleozoic era. Molecular clock analyses place the split between ticks and their closest mite relatives at approximately 300–350 million years ago, in the Carboniferous period. Fossil evidence, including the 99 million‑year‑old Cornupalpatum specimen from Burmese amber, confirms the presence of hard‑shell ticks (Ixodidae) by the mid‑Cretaceous. Soft‑shell ticks (Argasidae) appear in the fossil record slightly later, around 120 million years ago.
The ancestral lineage likely originated from predatory, soil‑dwelling mites that gradually adapted to parasitism. Key evolutionary steps include:
- Development of a specialized capitulum for blood‑feeding.
- Evolution of a scutum (hard dorsal shield) in hard ticks, providing protection during prolonged attachment.
- Acquisition of host‑seeking behavior mediated by sensory organs sensitive to carbon dioxide, heat, and host odors.
Host association shifted from early terrestrial vertebrates (early amphibians and reptiles) to the diverse array of mammals, birds, and reptiles observed today. Phylogenetic studies indicate that the earliest tick ancestors parasitized primitive amniotes, with subsequent radiation aligning with the diversification of dinosaurs and early mammals.
In summary, ticks emerged from ancient mite ancestors in the Carboniferous, acquired hematophagy through morphological innovations, and diversified alongside vertebrate hosts throughout the Mesozoic era.