Host selection of hematophagous leeches (Haemadipsa japonica): Implications for iDNA studies

Abstract

The development of an efficient and cost‐effective method for monitoring animal populations or biodiversity is urgently needed, and invertebrate‐derived DNA (iDNA) may offer a promising tool for assessing the diversity and other ecological information of vertebrates. We studied the host species of a hematophagous leech (Haemadipsa japonica) in Yakushima by genetic barcoding and compared the results with those for mammal composition revealed by camera trapping. We analyzed 119 samples using two sets of primers by Sanger sequencing and one set of primer by next generation sequencing. The proportion of the samples that were successfully sequenced and identified to at least one species was 11.8–24.3%, depending on the three different methods. In all of these three methods, most of the samples were identified as sika deer (18/20, 6/15 and 16/29) or human (2/20, 7/15 and 21/29). The nonhuman mammal host species composition was significantly different from that estimated by camera trapping. Sika deer was the main host, which may be related with their high abundance, large body size and terrestriality. Ten samples included DNA derived from multiple species of vertebrates. This may be due to the contamination of human DNA, but we also found DNA from deer, Japanese macaque and a frog in the same samples, suggesting the mixture of the two meals in the gut of the leech. Using H. japonica‐derived iDNA would not be suitable to make an inventory of species, but it may be useful to collect genetic information on the targeted species, due to their high host selectivity.

The potential of aquatic haematophagous, liquidosomatophagous and macrophagous leeches as a tool for iDNA characterisation

“…As in Williams et al, (2020), we detected both aquatic and terrestrial vertebrate taxa in the analyzed aquatic bloodfeeding leeches (Table 2; Figure 1). Unsurprisingly, this is in contrast to the well-studied, terrestrial, bloodfeeding haemadipsid leeches, in which no aquatic vertebrates have so far been detected (Drinkwater et al, 2020(Drinkwater et al, , 2018Hanya et al, 2019;Schnell et al, 2018;Schnell et al, 2012). Among the terrestrial vertebrates that we detected in the aquatic bloodfeeding leech species, we identified a single bird species, the black-crowned night heron, N. nycticorax.…”

“…With the exception of Hanya et al, (2019) who extracted and PCR amplified the DNA of leeches individually, most studies using DNA metabarcoding to target iDNA from leech gut contents have processed the leeches in pools of several individuals (Abrams et al, 2019;Fahmy et al, 2019;Williams et al, 2020). In addition, except for Hanya et al, (2019), Schnell et al, (2012) and Schnell et al, (2018), all previous studies, have used several metabarcoding primer sets and, therefore, a direct comparison to our results is strenuous, as we processed the leeches individually and used only a single metabarcoding primer set. In addition, no other study has used metabarcoding to target iDNA from the gut contents of non-bloodfeeding leeches.…”

“…Moreover, the processing of the samples can also contribute to the paucity of diversity in any individual leech. Hanya et al, (2019) reported variations in the detection of mammal species when the DNA extract also contained leech DNA and when using different primer sets. This could be another reason for the higher detection rate in our study as we did not pool leech specimens.…”

“…Nevertheless, in some ways, it is possible to compare our results to those of previous studies. Studies pooling several leeches have found between 0.5 to 1.6 diet taxa per pool (Abrams et al, 2019;Axtner et al, 2019;Drinkwater et al, 2020;Schnell et al, 2018;Williams et al, 2020), whereas Hanya et al, (2019) and Schnell et al, (2012) detected 1-3 diet taxa (including human) in 24.3% of their individual leeches. In the current study, diet taxa were detected in more than 50% of the individually analyzed bloodfeeding and liquidosomatophagous leeches, whereas the detection rate in the macrophagous leeches was 36.7%.…”

Leech blood‐meal invertebrate‐derived DNA reveals differences in Bornean mammal diversity across habitats

“…Most iDNA studies to date have also treated leeches and other invertebrates as passive samplers, whereas these taxa may exhibit some degree of active prey choice. Evidence for prey selection was previously suggested for the Japanese blood feeding leech ( Haemadipsa japonica ), where mammals seen on camera traps differed from those detected by iDNA (Hanya et al., 2019 ). Here the authors concluded that, due to apparent nonpassive foraging, this leech species might be a poor choice of sampler for generating a comprehensive biodiversity inventory (Hanya et al., 2019 ).…”