Abstract:
Ticks are monophyletic and composed of the hard (Ixodidae) and soft (Argasidae) tick families, as well as the Nuttalliellidae,
a family with a single species, Nuttalliella namaqua. Significant biological differences in lifestyle strategies for hard and soft
ticks suggest that various blood-feeding adaptations occurred after their divergence. The phylogenetic relationships
between the tick families have not yet been resolved due to the lack of molecular data for N. namaqua. This tick possesses a
pseudo-scutum and apical gnathostoma as observed for ixodids, has a leathery cuticle similar to argasids and has been
considered the evolutionary missing link between the two families. Little knowledge exists with regard to its feeding
biology or host preferences. Data on its biology and systematic relationship to the other tick families could therefore be
crucial in understanding the evolution of blood-feeding behaviour in ticks. Live specimens were collected and blood meal
analysis showed the presence of DNA for girdled lizards from the Cordylid family. Feeding of ticks on lizards showed that
engorgement occurred rapidly, similar to argasids, but that blood meal concentration occurs via malpighian excretion of
water. Phylogenetic analysis of the 18S nuclear and 16S mitochondrial genes indicate that N. namaqua grouped basal to the
main tick families. The data supports the monophyly of all tick families and suggests the evolution of argasid-like bloodfeeding
behaviour in the ancestral tick lineage. Based on the data and considerations from literature we propose an origin
for ticks in the Karoo basin of Gondwanaland during the late Permian. The nuttalliellid family almost became extinct during
the End Permian event, leaving N. namaqua as the closest living relative to the ancestral tick lineage and the evolutionary
missing link between the tick families.
