The Asian longhorned tick, Haemaphysalis longicornis, is an ectoparasite of domestic and wild animals, which transmit various pathogens including Severe Fever with Thrombocytopenia Syndrome Virus (SFTSV). They are the predominant hard tick species in Republic of Korea (ROK) and widely distributed throughout ROK. It is known that H. longicornis produce their offspring via two reproductive strategies, bisexual and parthenogenesis. It might affect their population maintenance and vectorial capacity. Parthenogenesis H. longicornis had the insertion of two thymine ‘T’ in mitochondrial 16s rDNA. In this study, we analyzed the proportion of bisexual and parthenogenesis H. longicornis in ROK including thirteen cities: Goseong[GS], Sokcho[SC], Chuncheon[CC], Ganghwa[GH], Samcheok[SCH], Sangju[SJ], Boryeong[BR], Ulsan[US], Gochang[GC], Jinju[JNJ], Jindo[JD], Jeju[JJ], and Seogwipo[SG]. Parthenogenesis individuals predominated from the northeastern are of ROK including Goseong, Sokcho, Chuncheon, Ganghwa, Samcheok, Sangju, Ulsan, and Jinju. Whereas bisexual individuals predominated from the southwestern area in ROK including Boryeong, Gochang, Jindo, Jeju, and Seogwipo. The analysis of haplotype diversity using concatenated sequences of mitochondrial Cytochrome c oxidase subunit I (COI) and Cytochrome B (CytB) revealed that H. longicornis were grouped into two major haplotypes. Two major haplotypes were correlated with bisexual and parthenogenesis, respectively. Likewise, H. longicornis individuals were divided into two clades and each clade were indicated by bisexual and parthenogenesis. The current study provides us an understanding of the genetic characteristics of two reproductive strategies for H. longicornis, which will be led to expand knowledge of the life cycle and population maintaining for H. longicornis.

The salivary glands of hard ticks consist of three types (type I, II, and III) of acini according to their functions and location. The type II and III acini play critical roles in tick salivation, which is likely controlled by a variety of neuropeptides or neurotransmitter via interaction with their receptor, G protein-coupled receptors (GPCRs). Orchestration of dopamine receptor (D1) and invertebrate specific D1-like dopamine receptor (InvD1L) located in type II and III acini precisely control tick salivary secretion via collection of primary saliva in the lumen and expulsion of collected saliva, respectively. The two dopamine receptors (D1 and InvD1L) in Haemaphysalis longicornis were identified as 1278 bp (426 aa) and 1362 bp (454 aa) in length, respectively. Both dopamine receptors were functionally analyzed through Ca2+ and cAMP assay using the heterologous expression system. The transcripts of D1 and InvD1L were profiled from synganglion and salivary glands of female ticks (unfed, 3/18/60/96 post blood meal and replete). D1 and InvD1L were significantly upregulated in the early phase of blood feeding from female H. longicornis. Salivary secretion induced by dopamine was significantly reduced by RNAi of D1 and InvD1L. Interestingly, RNAi of two dopamine receptors induced a significantly longer period of blood feeding in female ticks, which were significantly lighter after feeding than control. Taken together, it was suggested that D1 and InvD1L play critical roles in early and late phase of tick blood feeding for feeding capability.