Host-Specificity of Monoxenous Trypanosomatids: Statistical
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Protist, Vol. 166, 551–568, November 2015 http://www.elsevier.de/protis Published online date xxx ORIGINAL PAPER Host-specificity of Monoxenous Trypanosomatids: Statistical Analysis of the Distribution and Transmission Patterns of the Parasites from Neotropical Heteroptera a b b c,1 Eugene Kozminsky , Natalya Kraeva , Aygul Ishemgulova , Eva Dobáková , c,d,e f b,d Julius Lukesˇ , Petr Kment , Vyacheslav Yurchenko , d,g h,2 Jan Votypka´ , and Dmitri A. Maslov a Zoological Institute, Russian Academy of Sciences, St.-Petersburg, 199034, Russia b Life Science Research Centre, University of Ostrava, 70200 Ostrava, Czech Republic c ˇ Institute of Parasitology, Biology Centre, Czech Academy of Sciences, 37005 Ceské Budejoviceˇ (Budweis), Czech Republic d ˇ Faculty of Science, University of South Bohemia, 37005 Ceské Budejoviceˇ (Budweis), Czech Republic e Canadian Institute for Advanced Research, Toronto, ON M5G 1Z8, Canada f Department of Entomology, National Museum, 19300 Prague, Czech Republic g Department of Parasitology, Faculty of Science, Charles University, 12843 Prague, Czech Republic h Department of Biology, University of California - Riverside, Riverside, CA 91521, USA Submitted May 28, 2015; Accepted August 18, 2015 Monitoring Editor: Michael Melkonian Host-parasite relationships and parasite biodiversity have been the center of attention for many years; however the primary data obtained from large-scale studies remain scarce. Our long term investigations of trypanosomatid (Euglenozoa: Kinetoplastea) biodiversity from Neotropical Heteroptera have yielded almost one hundred typing units (TU) of trypanosomatids from one hundred twenty host species. Half of the parasites’ TUs were documented in a single host species only but the rest were found parasitizing two to nine species of hosts, with logarithmic distribution best describing the observed distribution of parasites among hosts. Different host superfamilies did not show significant differences in numbers of trypanosomatid TUs they carry, with exception of Pyrrhocoroidea which showed higher parasite richness than any other group tested. Predatory reduviids shared significantly larger numbers of parasite TUs with phytophagous mirids and coreids than the numbers shared between any other 1 Permanent address: Faculty of Natural Sciences, Comenius University, Bratislava, Slovakia 2 Corresponding author; fax +1 951 827 4286 e-mail [email protected] (D.A. Maslov). http://dx.doi.org/10.1016/j.protis.2015.08.004 1434-4610/© 2015 Elsevier GmbH. All rights reserved. 552 E. Kozminsky et al. groups. These results show that the specificity of trypanosomatid-heteropteran associations is not very strict: parasites seem to be transmissible between different host groups within the same niche and predatory hosts may acquire parasites from their prey. © 2015 Elsevier GmbH. All rights reserved. Key words: Trypanosomatids; Heteroptera; host-parasite specificity; biodiversity; Spliced Leader RNA. Introduction epithelium and hindgut walls of its host, Triatoma infestans, and in the hindgut it is preferentially found For nearly a century the “one host – one parasite” attached in the areas different from those used by paradigm has been the main criterion used to define Trypanosoma cruzi (Schaub et al. 1992; Schaub species of insect trypanosomatids (Podlipaev 1990; and Boker 1986). In other cases, e.g. Leptomonas Vickerman 1976; Wallace 1966). Historically, the wallacei infecting Oncopeltus fasciatus, the pro- notion of a strict specificity of the parasite–host tists are found in the gut lumen in association with systems has its roots in investigations of mul- perimicrovillar membranes as well as attached to ticellular parasites which undergo complex life the hindgut walls. Noticeably, the progression from cycles and, therefore, have evolved intricate adap- one gut section to another was accompanied by tations to particular host species. In trypanosomatid a change of the parasite’s morphology, as well protists (Euglenozoa: Kinetoplastea), strict host as the surface carbohydrates suggesting specific specificity is supported by data from dixenous and dynamic interactions on the molecular level insect-transmitted parasites of vertebrates (Hoare (Romeiro et al. 2003a, b). Surface carbohydrates 1972; Lainson and Shaw 1987). Thus, in Leish- have also been implicated in the process of coloniz- mania, a narrow range of competent vectors is ing salivary glands of the mosquito Aedes aegypti defined by the specific and complex interactions by a monoxenous trypanosomatid Blastocrithidia between the parasite and the sand fly accom- culicis (Nascimento et al. 2010). These interactions plished by the parasite’s surface lipophosphoglycan resemble those which are observed between dixe- molecules (Sacks 2001; Turco and Sacks 2003). On nous parasites and their vectors. However, while the contrary, monoxenous trypanosomatids appear the development of dixenous trypanosomatids in to have a relaxed stringency of associations with a vector results in producing an infective (e.g. their hosts increasing the frequency of non-specific metacyclic) stage, in monoxenous species its main infections. These speculations are supported by purpose may be to maintain a life-long infection of the apparent lack of parasite-host co-evolutionary the host which would also increase the chance of patterns in the analyses of flagellates in several transmission. host taxa (Bulat et al. 1999; Merzlyak et al. 2001; Demonstration of the complex and specific inter- Votypka´ et al. 2010). In the latter cases, the investi- actions of monoxenous parasites and their hosts gated hosts were found to bear rather diverse sets has been supplemented by the recent biodiver- of parasites (Chandler and James 2013; Maslov sity surveys which revealed associations of certain et al. 2007; Westenberger et al. 2004; Wilfert et al. large groups (orders) of hosts with respective major 2011). Such observations led to the departure from clades of parasites (Maslov et al. 2013; Teixeira the venerable and easy-to-grasp “one host – one et al. 2011; Ty´cˇ et al. 2013; Votypka´ et al. 2012a, monoxenous parasite” philosophy replaced with the 2013). The smaller groups of trypanosomatids with concept of the flexible “broad” specificity of these apparent host specificity at the family or genus organisms (Kostygov et al. 2014; Podlipaev 2003). levels have also been discovered (Maslov et al. Nonetheless, there is evidence in favor of strong 2007; Votypka´ et al. 2012b). At the same time, and specific interactions of at least some monoxe- there is a growing number of examples suggesting nous trypanosomatids and their hosts. In some non-specific or transient infections, e.g. in insec- of such cases, the parasites are found lining the tivorous insects which can acquire parasites from host’s intestinal walls as a dense carpet, or can be prey or in dipterans which feed on nutrient-rich found in just one particular compartment, e.g in the substrates and can sustain a long-term survival of midgut, hindgut, Malpighian tubules or hemolymph parasites in their gut lumen (Carvalho and Deane (J.V, D.A.M and J.L., unpubl. data) (Schwarz et al. 1974; Chandler and James 2013; Maslov et al. 2015). The flagellates’ attachment is not random: 2007; Ty´cˇ et al. 2013; Yurchenko et al. 2006b). thus, Blastocrithidia triatomae colonizes the midgut Therefore, the emerging view is that neither the Host Specificity of Insect Trypanosomatids 553 broad nor the strict specificity paradigms are appli- Heteroptera. Our current Neotropical SL repeat cable to the entire group which turned out to be database includes ∼450 entries including 193 SL more diverse than was anticipated even a few years RNA repeat sequences determined in this work ago (Maslov et al. 2013). This diversity includes (Table 2; see also table 1 of Maslov et al. 2007, not only genetic make-ups of the organisms but and table 1 of Westenberger et al. 2004). also various specificity levels which in turn are defined by the differences in interactions between General Characterization of Host-parasite hosts and parasites. The current study aims at Associations further testing the variable specificity hypothesis and at estimating the relative occurrence of para- Considering the multitude of parasites and hosts, sites with the narrow and/or broad host range. The we began asking questions about patterns in host- multi-year study presented herein concentrates on parasite associations. As a pre-requisite to this parasites in Neotropical Heteroptera, so far the analysis, the SL sequences were used to derive most extensively sampled host order and biogeo- a neighbor-joining dendrogram which reflects phy- graphic region. logenetic relationships among trypanosomatids (Fig. 2). The repeat’s most conserved regions (encompassing ∼150 bp from the -100 position in Results relation to the transcription start to the transcrip- tion termination sites by the oligo(T)-block at the 3 end of the SL RNA gene) are alignable across Current Status of the Survey the entire family and were used for this purpose. The recent survey of trypanosomatid parasites in The dendrogram is consistent with the known phy- two Neotropical regions is summarized in Table 1. logeny of the group that was established earlier Out of 1,210 insects that were dissected and ana- and shows that the Trypanosomatidae family is lyzed for trypanosomatids using light microscopy, subdivided into several major clades (summarized 250 insects were found to contain parasites in Maslov et al. 2013). In accordance with previ- in the