Molecular phylogeny of the New World bloodfeeding leeches of the genus Haementeria and reconsideration of the biannulate genus Oligobdella

Discovery of a novel symbiotic lineage associated with a hematophagous leech from the genus Haementeria

Similarly to other strict blood feeders, leeches from the Haementeria genus (Hirudinida: Glossiphoniidae) have established a symbiotic association with bacteria harbored intracellularly in esophageal bacteriomes. Previous genome sequence analyses of these endosymbionts revealed co-divergence with their hosts, a strong genome reduction, and a simplified metabolism largely dedicated to the production of B vitamins, which are nutrients lacking from a blood diet. 'Candidatus Providencia siddallii' has been identified as the obligate nutritional endosymbiont of a monophyletic clade of Mexican and South American Haementeria spp. However, the Haementeria genus includes a sister clade of congeners from Central and South America, where the presence or absence of the aforementioned symbiont taxon remains unknown. In this work, we report on a novel bacterial endosymbiont found in a representative from this Haementeria clade. We found that this symbiont lineage has evolved from within the Pluralibacter genus, known mainly from clinical but also environmental strains. Similarly to Ca. Providencia siddallii, the Haementeria-associated Pluralibacter symbiont displays clear signs of genome reduction, accompanied by an A+T-biased sequence composition. Genomic analysis of its metabolic potential revealed a retention of pathways related to B vitamin biosynthesis, supporting its role as a nutritional endosymbiont. Finally, comparative genomics of both Haementeria symbiont lineages suggests that an ancient Providencia symbiont was likely replaced by the novel Pluralibacter one, thus constituting the first reported case of nutritional symbiont replacement in a leech without morphological changes in the bacteriome.

IMPORTANCE

Obligate symbiotic associations with a nutritional base have likely evolved more than once in strict blood-feeding leeches. Unlike those symbioses found in hematophagous arthropods, the nature, identity, and evolutionary history of these remains poorly studied. In this work, we further explored obligate nutritional associations between Haementeria leeches and their microbial symbionts, which led to the unexpected discovery of a novel symbiosis with a member of the Pluralibacter genus. When compared to Providencia siddallii, an obligate nutritional symbiont of other Haementeria leeches, this novel bacterial symbiont shows convergent retention of the metabolic pathways involved in B vitamin biosynthesis. Moreover, the genomic characteristics of this Pluralibacter symbiont suggest a more recent association than that of Pr. siddallii and Haementeria. We conclude that the once-thought stable associations between blood-feeding Glossiphoniidae and their symbionts (i.e., one bacteriome structure, one symbiont lineage) can break down, mirroring symbiont turnover observed in various arthropod lineages.

Unoculubranchiobdella sp. (Hirudinea: Ozobranchidae) as a vector for Haemogregarina spp. in freshwater turtles from Brazil

Species of Haemogregarina are blood parasites known to parasitise vertebrate hosts, including fishes (Haemogregarina sensu lato) and freshwater turtles (Haemogregarina sensu stricto). Their vectors, include gnathiid isopods and leeches, respectively. In turtles, Haemogregarina balli has the best-characterized life cycle in the genus. However, no studies in Brazil have suggested a possible vector for any species of Haemogregarina from freshwater turtles. Therefore, in the present study, we provide insights into a leech vector based on specimens found feeding on two species of freshwater turtles, Podocnemis unifilis and Podocnemis expansa, using morphological and molecular data. In 2017 and 2019, freshwater turtles were collected in Goiás State, Brazil. Hosts were inspected for ectoparasites and leeches were collected from two specimens of P. expansa and nine specimens of P. unifilis. Leeches were subsequently identified as members of the genus Unoculubranchiobdella. Leech histological slides revealed haemogregarine-like structures, similar to post-sporogonic merogony, found near the gills and within the posterior sucker. Molecular analysis of the haemeogregarines resulted in the identification of three species of Haemogregarina: Haemogregarina embaubali, Haemogregarina goianensis, and Haemogregarina brasiliana. Therefore, our findings, based on morphology and DNA data suggest leeches of the genus Unoculubranchiondella as vectors for at least three species of Haemogregarina from Brazilian turtles.

Evolution of an Alternative Genetic Code in the Providencia Symbiont of the Hematophagous Leech Haementeria acuecueyetzin

Strict blood-feeding animals are confronted with a strong B-vitamin deficiency. Blood-feeding leeches from the Glossiphoniidae family, similarly to hematophagous insects, have evolved specialized organs called bacteriomes to harbor symbiotic bacteria. Leeches of the Haementeria genus have two pairs of globular bacteriomes attached to the esophagus which house intracellular "Candidatus Providencia siddallii" bacteria. Previous work analyzing a draft genome of the Providencia symbiont of the Mexican leech Haementeria officinalis showed that, in this species, the bacteria hold a reduced genome capable of synthesizing B vitamins. In this work, we aimed to expand our knowledge on the diversity and evolution of Providencia symbionts of Haementeria. For this purpose, we sequenced the symbiont genomes of three selected leech species. We found that all genomes are highly syntenic and have kept a stable genetic repertoire, mirroring ancient insect endosymbionts. Additionally, we found B-vitamin pathways to be conserved among these symbionts, pointing to a conserved symbiotic role. Lastly and most notably, we found that the symbiont of H. acuecueyetzin has evolved an alternative genetic code, affecting a portion of its proteome and showing evidence of a lineage-specific and likely intermediate stage of genetic code reassignment.

The potential of aquatic bloodfeeding and nonbloodfeeding leeches as a tool for iDNA characterisation

Leeches play important roles in food webs due to their abundance, diversity and feeding habits. Studies using invertebrate‐derived DNA (iDNA) extracted from leech gut contents to target vertebrate DNA have focused on the Indo‐Pacific region and mainly leveraged the leech family Haemadipsidae, composed of bloodfeeding terrestrial leeches, while predatory, fluid/tissue‐feeding and aquatic bloodfeeding species have been largely disregarded. While there is some general knowledge regarding the taxonomic groups that leeches prefer to feed on, detailed taxonomic resolution is missing and, therefore, their potential use for monitoring animals is unknown. In this study, 116 leeches from 12 species (six families) and spanning the three feeding habits were collected in Mexico and Canada. We used DNA metabarcoding to investigate their diet and assess their potential use for biodiversity monitoring. We detected vertebrates from five orders including fish, turtles and birds in the diet of aquatic bloodfeeding leeches; eight invertebrate orders of annelids, arthropods and molluscs in leeches that feed on body fluids and tissues; and 10 orders of invertebrates belonging to Arthropoda and Annelida, as well as one vertebrate and one parasitic nematode, in predatory leeches. These results show the potential use of iDNA from aquatic bloodfeeding leeches for retrieving vertebrate taxa, and from predatory and fluid‐feeding leeches for invertebrates. Our study provides information about the dietary range of freshwater leeches and one terrestrial leech and contributes proof‐of‐concept for the use of these leeches for animal monitoring, expanding our knowledge of the use of iDNA from leech gut contents to North America.

Batracobdelloides bangkhenensis sp. n. (Hirudinea: Rhynchobdellida), a new leech species parasite on freshwater snails from Thailand

A new snail-eating leech, Batracobdelloides bangkhenensis sp. n., was discovered at Kasetsart University, Bangkhen Campus, Bangkok, Thailand. This species is found free living in the benthic zone of ponds; feeds on freshwater snails, including Bithynia siamensis siamensis, Indoplanorbis exustus, Radix rubiginosa, Physella acuta, and Pomacea canaliculata; and uses a shell as a shelter during the parental care period, with a colony of 7-15 juvenile individuals held on the venter inside the shell of host. Batracobdelloides bangkhenensis displays distinct morphological characters, including a rice-shaped body showing transparency, cephalization, two eye pairs merged on somite III, an anterior sucker twice as large as the cephalic region, a central mouth in the anterior sucker, seven light brown transverse rows in the neck region, absent dorsal papillae, rich green pigments on the dorsum, a male gonopore on XIIa2/XIIa3 (27-28), a female gonopore on XIIIa1/XIIIa2 (29-30), and diffuse aggregations of minute, spherical salivary glands in the neck region. Comparisons of the COI and COI-ND1 genes showed a monophyletic clade for Batracobdelloides, and the phylogenetic tree of the COI gene also indicated that B. bangkhenensis is distinct from other species in the genus, with strong support values.

Mitogenome of the blood feeding leech Haementeria acuecueyetzin (Hirudinida: Glossiphoniidae) from Tabasco, Mexico

Here, we present the mitogenome of the blood feeding leech Haementeria acuecueyetzin (Hirudinida: Glossiphoniidae) based on specimens collected in Tabasco, Mexico. The circular genome is 14,985 bp in length, and consists of 13 protein-coding genes, 22 tRNA genes, two rRNA genes, and an AT-rich control region. Phylogenetic analysis based on the 13 protein-coding genes and two rRNA genes places H. acuecueyetzin sister to H. officinalis within the family Glossiphoniidae. Mitochondrial gene order in H. acuecueyetzin is consistent with other members of Clitellata with no evidence of gene gain/loss, duplication, or rearrangement.

Leeches in the extreme: Morphological, physiological, and behavioral adaptations to inhospitable habitats

With more than 700 described species, leeches include morphological, physiological, and behavioral diversity and occur in terrestrial and aquatic habitats, including freshwater, estuarine, and marine ecosystems. Leeches inhabit a number of extreme environments, including extremes in temperature, moisture, salinity, pressure, light, and pollution. In some cases, leeches in extreme environments have specialized morphological, physiological, or behavioral adaptations to survive these conditions, yet unique adaptations are not apparent in some species. Leeches that inhabit inhospitable habitats occur in more than one branch or family of leech phylogeny suggesting that there have been independent invasions of environments with extreme conditions. Herein, we review examples of leeches that live in extreme conditions and the exceptional biology that has contributed to leeches being the most extreme annelids.

Leeches from Mexico City, remnants of the ancient lake

Genetic barcodes (partial sequences of the mitochondrial cytochrome c oxidase subunit I) were generated for freshwater leeches that inhabit the Mexico Basin, upon which Mexico City and its metropolitan area have developed. Once a continuous lake, the basin has passed through continuous events of artificial desiccation in the last 500 years so that it is currently conformed by a few and highly modified and polluted isolated freshwater bodies. Six species of leeches from three families were collected in five localities. Current sequence databases were able to determine five of the six species collected for this study with the only exception of Haemopis caballeroi, for which no sequence data are available in public repositories. Taxonomic assignment of cocoons was possible via comparison of barcode sequences. We discuss the presence of a population of Erpobdella ochoterenai in Tecocomulco Lake that bares high genetic divergence from its conspecifics, which may indicate it is an undescribed species.

Reproductive differences among species, and between individuals and cohorts, in the leech genus Helobdella (Lophotrochozoa; Annelida; Clitellata; Hirudinida; Glossiphoniidae), with implications for reproductive resource allocation in hermaphrodites

Leeches and oligochaetes comprise a monophyletic group of annelids, the Clitellata, whose reproduction is characterized by simultaneous hermaphroditism. While most clitellate species reproduce by cross-fertilization, self-fertilization has been described within the speciose genus Helobdella. Here we document the reproductive life histories and reproductive capacities for three other Helobdella species. Under laboratory conditions, both H. robusta and H. octatestisaca exhibit uniparental reproduction, apparently reflecting self-fertility, and suggesting that this trait is ancestral for the genus. However, the third species, H. austinensis, seems incapable of reproduction by self-fertilization, so we inferred its reproductive life history by analyzing reproduction in breeding cohorts. Comparing the reproductive parameters for H. robusta reproducing in isolation and in cohorts revealed that reproduction in cohorts is dramatically delayed with respect to that of isolated individuals, and that cohorts of leeches coordinate their cocoon deposition in a manner that is not predicted from the reproductive parameters of individuals reproducing in isolation. Finally, our comparisons of reproductive capacity for individuals versus cohorts for H. robusta, and between different sizes of cohorts for H. austinensis, reveal differences in resource allocation between male and female reproductive roles that are consistent with evolutionary theory.

Spatio-temporal variation and the use of host body surface by ectoparasites of the chelonians Phrynops geoffroanus and Mesoclemmys tuberculata in areas of the Caatinga and Atlantic Forest in northeast Brazil

Ectoparasites such as hematophagous leeches and monogeneans are common in chelonians, occupying different parts of the body. Thus, the present study aimed to identify and describe the fauna of ectoparasites that infest Phrynops geoffroanus and Mesoclemmys tuberculata to evaluate the effect of host conditions and seasonality (dry and rainy season) on the abundance and composition of ectoparasites. We verified the presence of ectoparasites in 73.2% of the examined turtles, with four species of leeches belonging to Glossiphoniidae, Haementeria brasiliensis sensu Cordero, 1937, Helobdella cf. adiastola, Haementeria sp1., and Haementeria sp2., and one monogenean Polystomatidae, Polystomoides brasiliensis. For both chelonians, we observed a significant difference in the abundance of ectoparasites in relation to sex, biome, and season, which was unrelated to length and mass. Leeches were more frequent in the cavities of the hind limbs in P. geoffroanus, and the anterior limbs of M. tuberculata. The general spatial niche overlap of ectoparasites was high, except for that of the monogenean P. brasiliensis, which did not overlap with those of other leech species. The present study is the first report of the presence of H. brasiliensis and P. brasiliensis parasitizing M. tuberculata, and Helobdella cf. adiastola in a phoretic relationship with P. geoffroanus and M. tuberculata. Finally, the differences in infestation levels may reflect ecological factors, differences in behavioral patterns of the hosts, and different anthropic alterations suffered in the Caatinga and Atlantic Forest biomes.

New specific primers for amplification of the Internal Transcribed Spacer region in Clitellata (Annelida)

Nuclear molecular evidence, for example, the rapidly evolving Internal Transcribed Spacer region (ITS), integrated with maternally inherited (mitochondrial) COI barcodes, has provided new insights into the diversity of clitellate annelids. PCR amplification and sequencing of ITS, however, are often hampered by poor specificity of primers used. Therefore, new clitellate‐specific primers for amplifying the whole ITS region (ITS: 29F/1084R) and a part of it (ITS2: 606F/1082R) were developed on the basis of a collection of previously published ITS sequences with flanking rDNA coding regions. The specificity of these and other ITS primers used for clitellates were then tested in silico by evaluating their mismatches with all assembled and annotated sequences (STD, version r127) from EMBL, and the new primers were also tested in vitro for a taxonomically broad sample of clitellate species (71 specimens representing 11 families). The in silico analyses showed that the newly designed primers have a better performance than the universal ones when amplifying clitellate ITS sequences. In vitro PCR and sequencing using the new primers were successful, in particular, for the 606F/1082R pair, which worked well for 65 of the 71 specimens. Thus, using this pair for amplifying the ITS2 will facilitate further molecular systematic investigation of various clitellates. The other pair (29F/1084R), will be a useful complement to existing ITS primers, when amplifying ITS as a whole.

Comparative Mitogenomics of Leeches (Annelida: Clitellata): Genome Conservation and Placobdella-Specific trnD Gene Duplication

Mitochondrial DNA sequences, often in combination with nuclear markers and morphological data, are frequently used to unravel the phylogenetic relationships, population dynamics and biogeographic histories of a plethora of organisms. The information provided by examining complete mitochondrial genomes also enables investigation of other evolutionary events such as gene rearrangements, gene duplication and gene loss. Despite efforts to generate information to represent most of the currently recognized groups, some taxa are underrepresented in mitochondrial genomic databases. One such group is leeches (Annelida: Hirudinea: Clitellata). Herein, we expand our knowledge concerning leech mitochondrial makeup including gene arrangement, gene duplication and the evolution of mitochondrial genomes by adding newly sequenced mitochondrial genomes for three bloodfeeding species: Haementeria officinalis, Placobdella lamothei and Placobdella parasitica. With the inclusion of three new mitochondrial genomes of leeches, a better understanding of evolution for this organelle within the group is emerging. We found that gene order and genomic arrangement in the three new mitochondrial genomes is identical to previously sequenced members of Clitellata. Interestingly, within Placobdella, we recovered a genus-specific duplication of the trnD gene located between cox2 and atp8. We performed phylogenetic analyses using 12 protein-coding genes and expanded our taxon sampling by including GenBank sequences for 39 taxa; the analyses confirm the monophyletic status of Clitellata, yet disagree in several respects with other phylogenetic hypotheses based on morphology and analyses of non-mitochondrial data.

Phylogenetic and morphological characterization of trypanosomes from Brazilian armoured catfishes and leeches reveal high species diversity, mixed infections and a new fish trypanosome species

Background

Several Trypanosoma species transmitted by leeches infect marine and freshwater fish worldwide. To date, all South American fish trypanosome species identified have been based on unreliable morphological parameters. We recently isolated and cultured trypanosomes from the Brazilian armoured catfishes Hypostomus luetkeni and H. affinis. Here, we report the first phylogenetic analyses of South American (Brazilian) trypanosomes isolated from fish, and from leeches removed from these fish. We also analysed morphologically and morphometrically the different forms of fish, leech and cultured trypanosomes.

Methods

V7V8 SSU rRNA and gGAPDH sequences were used for phylogenetic analysis of Brazilian fish and leech trypanosomes. Trypanosomes from cultures, fish blood and leech samples were also characterized morphologically and morphometrically by light and electron microscopy.

Results

In blood smears from fish high trypanosome prevalence (90–100 %) and parasitemia (0.9-1.0x10²) were observed. Phylogenetic relationships using SSU rRNA and gGAPDH showed that, despite relevant sequence divergence, all Brazilian fish (and derived cultures) and leech trypanosomes clustered together into a single clade. The Brazilian clade clustered with European, North American and African fish trypanosomes. Based on sequence analysis, we uncovered a new species of Brazilian fish trypanosome, Trypanosoma abeli n. sp. Trypanosoma abeli cultures contained pleomorphic epimastigotes, small trypomastigotes and rare sphaeromastigotes. Ultrastructural features of T. abeli included a cytostome-cytopharynx complex in epi- and trypomastigotes, a compact rod-like kinetoplast, lysosome-related organelles (LROs) and multivesicular bodies. Trypanosomes found in fish blood smears and leech samples were highly pleomorphic, in agreement with sequence data suggesting that catfishes and leeches often have mixed trypanosome infections.

Conclusions

Trypanosoma abeli n. sp. is the first trypanosome from South American fishes isolated in culture, positioned in phylogenetic trees and characterized at the ultrastructural level. Trypanosoma abeli n. sp. is highly prevalent in H. luetkeni and H. affinis armoured catfish from the Atlantic Forest biome, and in other catfish species from the Amazon and the Pantanal. Sequencing data suggested that Brazilian catfish often have mixed trypanosome infections, highlighting the importance of molecular characterization to identify trypanosome species in fishes and leeches.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-1193-7) contains supplementary material, which is available to authorized users.

Comparative Transcriptomic Analyses of Three Species of Placobdella (Rhynchobdellida: Glossiphoniidae) Confirms a Single Origin of Blood Feeding in Leeches

One of the recalcitrant questions regarding the evolutionary history of clitellate annelids involves the feeding preference of the common ancestor of extant rhynchobdellid (proboscis bearing) and arhynchobdellid (jaw bearing) leeches. Whereas early evidence, based on morphological data, pointed towards independent acquisitions of blood feeding in the 2 orders, molecular-based phylogenetic data suggest that the ancestor of modern leeches was a sanguivore. Here, we use a comparative transcriptomic approach in order to increase our understanding of the diversity of anticoagulation factors for 3 species of the genus Placobdella, for which comparative data have been lacking, and inspect these in light of archetypal anticoagulant data for both arhynchobdellid and other rhynchobdellid species. Notwithstanding the varying levels of host specificity displayed by the 3 different species of Placobdella, transcriptomic profiles with respect to anticoagulation factors were largely similar -this despite the fact that Placobdella kwetlumye only retains a single pair of salivary glands, as opposed to the 2 pairs more common in the genus. Results show that 9 different anticoagulant proteins and an additional 5 putative antihemostasis proteins are expressed in salivary secretions of the 3 species. In particular, an ortholog of the archetypal, single-copy, anticoagulant hirudin (not previously available as comparative data for rhynchobdellids) is present in at least 2 of 3 species examined, corroborating the notion of a single origin of blood feeding in the ancestral leech.

Solving a Bloody Mess: B-Vitamin Independent Metabolic Convergence among Gammaproteobacterial Obligate Endosymbionts from Blood-Feeding Arthropods and the Leech Haementeria officinalis

Endosymbiosis is a common phenomenon in nature, especially between bacteria and insects, whose typically unbalanced diets are usually complemented by their obligate endosymbionts. While much interest and focus has been directed toward phloem-feeders like aphids and mealybugs, blood-feeders such as the Lone star tick (Amblyomma americanum), Glossina flies, and the human body louse (Pediculus humanus corporis) depend on obligate endosymbionts which complement their B-vitamin-deficient diets, and thus are required for growth and survival. Glossiphoniid leeches have also been found to harbor distinct endosymbionts housed in specialized organs. Here, we present the genome of the bacterial endosymbiont from Haementeria officinalis, first of a glossiphoniid leech. This as-yet-unnamed endosymbiont belongs to the Gammaproteobacteria, has a pleomorphic shape and is restricted to bacteriocytes. For this bacterial endosymbiont, we propose the name Candidatus Providencia siddallii. This symbiont possesses a highly reduced genome with high A+T content and a reduced set of metabolic capabilities, all of which are common characteristics of ancient obligate endosymbionts of arthropods. Its genome has retained many pathways related to the biosynthesis of B-vitamins, pointing toward a role in supplementing the blood-restricted diet of its host. Through comparative genomics against the endosymbionts of A. americanum, Glossina flies, and P. humanus corporis, we were able to detect a high degree of metabolic convergence among these four very distantly related endosymbiotic bacteria.

Transcripts involved in hemostasis: Exploring salivary complexes from Haementeria vizottoi leeches through transcriptomics, phylogenetic studies and structural features

Throughout evolution, parasites have adapted in order to successfully intervene in the host defense, producing specific peptides and proteins. Interestingly, these peptides and proteins have been exploited as potential drug candidates against several diseases. Furthermore, biotechnology studies and cDNA libraries have remarkably contributed to identify potentially bioactive molecules. In this regard, herein, a cDNA library of salivary complexes from Haementeria vizottoi leeches was constructed, the transcriptome was characterized and a phylogenetic analysis was performed considering antistasin-like and antiplatelet-like proteins. Hundred twenty three transcripts were identified coding for putative proteins involved in animal feeding (representing about 10% of the expression level). These sequences showed similarities with myohemerythrins, carbonic anhydrases, anticoagulants, antimicrobials, proteases and protease inhibitors. The phylogenetic analysis, regarding antistasin-like and antiplatetlet-like proteins, revealed two main clades in the Rhynchobdellida leeches. As expected, the sequences from H. vizottoi have presented high similarities with those types of proteins. Thus, our findings could be helpful not only to identify new coagulation inhibitors, but also to better understand the biological composition of the salivary complexes.