Celebrity with a neglected taxonomy: molecular systematics of the medicinal leech (genus Hirudo)

Resistance to freezing conditions of endemic Antarctic polychaetes is enhanced by cryoprotective proteins produced by their microbiome

The microbiome plays a key role in the health of all metazoans. Whether and how the microbiome favors the adaptation processes of organisms to extreme conditions, such as those of Antarctica, which are incompatible with most metazoans, is still unknown. We investigated the microbiome of three endemic and widespread species of Antarctic polychaetes: Leitoscoloplos geminus, Aphelochaeta palmeri, and Aglaophamus trissophyllus. We report here that these invertebrates contain a stable bacterial core dominated by Meiothermus and Anoxybacillus, equipped with a versatile genetic makeup and a unique portfolio of proteins useful for coping with extremely cold conditions as revealed by pangenomic and metaproteomic analyses. The close phylosymbiosis between Meiothermus and Anoxybacillus and these Antarctic polychaetes indicates a connection with their hosts that started in the past to support holobiont adaptation to the Antarctic Ocean. The wide suite of bacterial cryoprotective proteins found in Antarctic polychaetes may be useful for the development of nature-based biotechnological applications.

A broad-taxa approach as an important concept in ecotoxicological studies and pollution monitoring

Aquatic invertebrates play a pivotal role in (eco)toxicological assessments because they offer ethical, cost-effective and repeatable testing options. Additionally, their significance in the food chain and their ability to represent diverse aquatic ecosystems make them valuable subjects for (eco)toxicological studies. To ensure consistency and comparability across studies, international (eco)toxicology guidelines have been used to establish standardised methods and protocols for data collection, analysis and interpretation. However, the current standardised protocols primarily focus on a limited number of aquatic invertebrate species, mainly from Arthropoda, Mollusca and Annelida. These protocols are suitable for basic toxicity screening, effectively assessing the immediate and severe effects of toxic substances on organisms. For more comprehensive and ecologically relevant assessments, particularly those addressing long-term effects and ecosystem-wide impacts, we recommended the use of a broader diversity of species, since the present choice of taxa exacerbates the limited scope of basic ecotoxicological studies. This review provides a comprehensive overview of (eco)toxicological studies, focusing on major aquatic invertebrate taxa and how they are used to assess the impact of chemicals in diverse aquatic environments. The present work supports the use of a broad-taxa approach in basic environmental assessments, as it better represents the natural populations inhabiting various ecosystems. Advances in omics and other biochemical and computational techniques make the broad-taxa approach more feasible, enabling mechanistic studies on non-model organisms. By combining these approaches with in vitro techniques together with the broad-taxa approach, researchers can gain insights into less-explored impacts of pollution, such as changes in population diversity, the development of tolerance and transgenerational inheritance of pollution responses, the impact on organism phenotypic plasticity, biological invasion outcomes, social behaviour changes, metabolome changes, regeneration phenomena, disease susceptibility and tissue pathologies. This review also emphasises the need for harmonised data-reporting standards and minimum annotation checklists to ensure that research results are findable, accessible, interoperable and reusable (FAIR), maximising the use and reusability of data. The ultimate goal is to encourage integrated and holistic problem-focused collaboration between diverse scientific disciplines, international standardisation organisations and decision-making bodies, with a focus on transdisciplinary knowledge co-production for the One-Health approach.

Rhodobacteraceae dominate the core microbiome of the sea star Odontaster validus (Koehler, 1906) in two opposite geographical sectors of the Antarctic Ocean

Microbiota plays essential roles in the health, physiology, and in adaptation of marine multi-cellular organisms to their environment. In Antarctica, marine organisms have a wide range of unique physiological functions and adaptive strategies, useful for coping with extremely cold conditions. However, the role of microbiota associated with Antarctic organisms in such adaptive strategies is underexplored. In the present study, we investigated the diversity and putative functions of the microbiome of the sea star Odontaster validus, one of the main keystone species of the Antarctic benthic ecosystems. We compared the whole-body bacterial microbiome of sea stars from different sites of the Antarctic Peninsula and Ross Sea, two areas located in two opposite geographical sectors of the Antarctic continent. The taxonomic composition of O. validus microbiomes changed both between and within the two Antarctic sectors, suggesting that environmental and biological factors acting both at large and local scales may influence microbiome diversity. Despite this, one bacterial family (Rhodobacteraceae) was shared among all sea star individuals from the two geographical sectors, representing up to 95% of the microbial core, and suggesting a key functional role of this taxon in holobiont metabolism and well-being. In addition, the genus Roseobacter belonging to this family was also present in the surrounding sediment, implying a potential horizontal acquisition of dominant bacterial core taxa via host-selection processes from the environment.

The Tribe Hyrtanellini Allen, 1980 (Ephemeroptera: Ephemerellidae) of Western and Central Asia with Description of a New Species

A new species, Serratella leonidi Martynov & Palatov, sp. nov., is described from Tajikistan based on immature stage. Based on larval material from Iran including the topotypes, Serratella elissa Jacobus, Zhou & McCafferty, 2009 is complementary described, and its generic placement is clarified. The delimitation of three genera that are members of the tribe Hyrtanellini Allen, 1980, namely Serratella Edmunds, 1959, Torleya Lestage, 1917 and Quatica Jacobus & McCafferty, 2008 is briefly discussed. The phylogenetic reconstruction of Hyrtanellini based on the COI gene showed the relations of representatives of these genera on the one hand, and distinct delimitation of Serratella leonidi sp. nov. and S. elissa on the other. A list of species from Western and Central Asia attributed to Hyrtanellini, their currently known distribution and a key for the determination of the larvae are proposed.

Life without blood: Molecular and functional analysis of hirudins and hirudin-like factors of the Asian non-hematophagous leech Whitmania pigra

BACKGROUND

Several leech species of the genera Hirudo, Hirudinaria, and Whitmania are widely used in traditional Chinese medicine (TCM) for the oral treatment of disorders associated with blood stasis. Among them, the non-hematophagous leech Whitmania pigra expresses a variety of components that have the potential to act on the vertebrate blood coagulation system.

OBJECTIVE

Whether the thrombin inhibitor hirudin, probably the most prominent leech-derived anticoagulant, is actually present in Whitmania pigra, is still a matter of debate. To answer that open question was the aim of the study.

METHODS

We identified several putative hirudin-encoding sequences in transcriptome data of Whitmania pigra. Upon gene synthesis and molecular cloning the respective recombinant proteins were expressed in Escherichia coli, purified, processed, and eventually functionally characterized for thrombin-inhibitory potencies in coagulation assays.

RESULTS

We were successful in the identification and functional characterization of several putative hirudins in Whitmania pigra. Some, but not all, of these factors are indeed thrombin inhibitors. Whitmania pigra hence expresses both hirudins (factors that inhibit thrombin) and hirudin-like factors (that do not or only very weakly inhibit thrombin). Furthermore, we revealed the exon/intron structures of the corresponding genes. Coding sequences of some putative hirudins of Whitmania pigra were present also in transcriptome datasets of Hirudo nipponia, a hematophagous leech that is likewise used in TCM.

CONCLUSIONS

Based on both structural and functional data we provide very strong evidence for the expression of hirudins in Whitmania pigra. This is the first description of hirudins in a non-hematophagous leech.

A new species of medicinal leech in the genus Hirudo Linnaeus, 1758 (Hirudiniformes, Hirudinidae) from Tianjin City, China

Medicinal leeches in the genus Hirudo have been utilized for therapeutic procedures for thousands of years. To date, six known species of Hirudo are widely distributed in different regions of the Eurasian continent. In this study, a new medicinal leech species Hirudotianjinensis Liu, sp. nov. is described based upon specimens collected from Tianjin City, China. The new species can be distinguished from its congeners by a combination of characters: blackish green dorsum with five continuous yellow longitudinal stripes; six sensillae on dorsal annulus a2 of segments VIII–XXV; greyish green ventrum with irregular bilateral dark brown spots; dorsum and abdomen separated by a pair of pale yellow stripes; front half atrium wrapped by white prostate; apparent albumen gland; epididymis massive in relation to ejaculatory bulb. The phylogenetic tree based upon COI implies a sister relationship to H.nipponia Whitman, 1886. A key to the known species is provided.

Insights into gut microbiota communities of Poecilobdella manillensis, a prevalent Asian medicinal leech

AIMS

Medicinal leeches (Annelida: Hirudinea) are fresh water ectoparasitic species which have been applied as traditional therapy. However, gut microbiota could bring high risks of opportunistic infections after leeching, and arouses great interests. Here gut bacterial and fungal communities of an Asian prevalent leech Poecilobdella manillensis, were characterized and analyzed through culture-independent sequencing.

METHODS AND RESULTS

With high coverage in 18 samples (>0.999), a more complicated community was apparent after comparing with previous leech studies. A total of 779/939 OTUs of bacteria and fungi were detected from leech guts. The bacterial community was dominated by phylum Bacteroidetes and Synergistetes. Genera Mucinivorans and Fretibacterium accounted mostly at the genus level. And genus Aeromonas showed an extremely low abundance (2.02%) on average. The fungal community was dominated by phylum Ascomycota and Basidiomycota. At the genus level, the dominant OTUs included Mortierella, Geminibasidium and Fusarium. The analysis of core taxa included those above dominant genera and some low-abundance genera (>1%). The functional annotation of bacterial community showed a close correlation with metabolism (34.8 ± 0.6%). Some fungal species were predicted as opportunistic human pathogens including Fusarium and Chaetomiaceae.

CONCLUSIONS

The present study provides fundamental rationales for further studies of such issues as bacteria-fungi-host interactions, host fitness, potential pathogens and infecting risks after leeching. It shall facilitate in-depth explorations on a safe utilization of leech therapy.

SIGNIFICANCE AND IMPACT OF STUDY

Present paper is the first-ever exploration on microbiota of a prevalent Asian medicinal leech based on culture-independent technical. And it is also the first report of gut fungi community of medicinal leech. The diversity and composition of bacteria in P. manillensis was far different from that of the European leech. The main components and core OTUs indicate a particular gut environment of medicinal leech. Unknown bacterial and fungal species were also recovered from leech gut.

New records of leeches of the genus Limnatis (Hirudinea, Praobdellidae) from the South Caucasus and Central Asia: phylogenetic relationships of Eurasian and African populations

Leeches of the genus Limnatis Moquin–Tandon, 1827 infest mucous membranes of various mammals, including humans and domestic ungulates. The type species of the genus L. nilotica (Savigny, 1822) was initially thought to occur throughout the Western Palaearctic, from North Africa to the Middle East and Central Asia. It was later found that L. paluda (Tennent, 1859) is a widespread Western Asian species. However, the South Caucasus and vast areas of Central Asia have not been explored sufficiently in terms of leeches of the genus Limnatis. We recorded L. paluda from Azerbaijan and Uzbekistan for the first time. We also carried out the first molecular characterisation of L. nilotica herein. We found a deep genetic differentiation (8 %) between the Western Asian L. paluda and North African (Moroccan) L. nilotica based on their COI sequences. This finding corroborates a previous morphology–based hypothesis on their separate species assignments. The low genetic diversity of L. paluda is explained by the recent colonisation of arid landscapes of Western Asia.

An annotated checklist of the eukaryotic parasites of humans, exclusive of fungi and algae

The classification of "parasites" in the medical field is a challenging notion, a group which historically has included all eukaryotes exclusive of fungi that invade and derive resources from the human host. Since antiquity, humans have been identifying and documenting parasitic infections, and this collective catalog of parasitic agents has expanded considerably with technology. As our understanding of species boundaries and the use of molecular tools has evolved, so has our concept of the taxonomy of human parasites. Consequently, new species have been recognized while others have been relegated to synonyms. On the other hand, the decline of expertise in classical parasitology and limited curricula have led to a loss of awareness of many rarely encountered species. Here, we provide a comprehensive checklist of all reported eukaryotic organisms (excluding fungi and allied taxa) parasitizing humans resulting in 274 genus-group taxa and 848 species-group taxa. For each species, or genus where indicated, a concise summary of geographic distribution, natural hosts, route of transmission and site within human host, and vectored pathogens are presented. Ubiquitous, human-adapted species as well as very rare, incidental zoonotic organisms are discussed in this annotated checklist. We also provide a list of 79 excluded genera and species that have been previously reported as human parasites but are not believed to be true human parasites or represent misidentifications or taxonomic changes.

Unravelling the Extent of Diversity within the Iberian Medicinal Leeches (Hirudinea: Hirudo) Using Molecules and Morphology

Until the beginning of the 21st century, the famous medicinal leech was thought to be represented by only one species, Hirudo medicinalis. However, recent publications have demonstrated that under that name, at least five different species of medicinal leeches were hidden. During the last decade, the biogeography of Western-Palaearctic leeches has begun to unravel, untangling their diversity in practically all of Europe, except for its westernmost peninsula, Iberia. Hirudo medicinalis has been repeatedly reported from Iberia, but those records were considered questionable. We discovered H. verbana in northern Spain, constituting its first record in Iberia. Using an integrative approach (combining morpho-anatomical data and molecular analyses using three genes, COI,12S rRNA, and ITS2), two endemic and geographically separated Iberian lineages have been found. One of them is easily distinguished by its distinctive colour-pattern and is described as H. verbana bilineata ssp. nov. We characterized the new subspecies morphologically, ecologically, and genetically. We also established its phylogenetic relationships with other European Hirudo spp. and confirm the presence of H. troctina in Iberia, occurring as far as 43° lat. N. Iberian H. verbana records constitute its westernmost known distribution to date. The provided distribution pattern of H. verbana contributes to a better understanding of the complexity of Iberia as a glacial refugium/cradle for endemisms, harbouring populations with a high degree of genetic structure that began to settle throughout the Pleistocene. Iberian Hirudo populations are declining in recent decades and there is an urgent need to assess their conservation status and to initiate conservation measures to reverse their decline.

Cryptic Clitellata: Molecular Species Delimitation of Clitellate Worms (Annelida): An Overview

Methods for species delimitation using molecular data have developed greatly and have become a staple in systematic studies of clitellate worms. Here we give a historical overview of the data and methods used to delimit clitellates from the mid-1970s to today. We also discuss the taxonomical treatment of the cryptic species, including the recommendation that cryptic species, as far as possible, should be described and named. Finally, we discuss the prospects and further development of the field.

Population genetic structure of the highly endangered butterfly Coenonympha oedippus (Nymphalidae: Satyrinae) at its southern edge of distribution

The Slovenian False Ringlet Coenonympha oedippus populations are under serious threat, as in the last two decades have witnessed a sharp decline in population distribution and size due to destruction, fragmentation and/or habitat quality degradation through intensive agriculture, abandonment of use and urbanization. We investigated the genetic diversity and structure of C. oedippus from the entire range of the species in Slovenia. Our results showed that the genetic variation in the Slovenian C. oedippus populations agrees with the geographical structure and the ecotypes previously determined by morphological and ecological data. We confirmed the existence of four genetically divergent and spatially non-overlapping geographical groups (Istria, Karst, Gorica, Ljubljansko barje) and two ecotypes ("wet" and "dry"). Despite small sample sizes due to critically threatened species, the results indicated significant nuclear and mitochondrial genetic diversity within the spatial groups. By gaining new insights into the evolutionary history of the C. oedippus population, we have recommended to consider the Slovenian population as one Evolutionary Significant Unit, and four spatial populations as Management Units for conservation purposes.

Draft genome of the European medicinal leech Hirudo medicinalis (Annelida, Clitellata, Hirudiniformes) with emphasis on anticoagulants

The European medicinal leech has been used for medicinal purposes for millennia, and continues to be used today in modern hospital settings. Its utility is granted by the extremely potent anticoagulation factors that the leech secretes into the incision wound during feeding and, although a handful of studies have targeted certain anticoagulants, the full range of anticoagulation factors expressed by this species remains unknown. Here, we present the first draft genome of the European medicinal leech, Hirudo medicinalis, and estimate that we have sequenced between 79–94% of the full genome. Leveraging these data, we searched for anticoagulation factors across the genome of H. medicinalis. Following orthology determination through a series of BLAST searches, as well as phylogenetic analyses, we estimate that fully 15 different known anticoagulation factors are utilized by the species, and that 17 other proteins that have been linked to antihemostasis are also present in the genome. We underscore the utility of the draft genome for comparative studies of leeches and discuss our results in an evolutionary context.

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.

Entrapped by the uneven central and Middle Eastern terrains: Genetic status of populations of Hirudo orientalis (Annelida, Clitellata, Hirudinida) with a phylogenetic review of the genus Hirudo

Phylogenetic relationships between species of the genus Hirudo plus genetic variation in the entire distribution range of Hirudo orientalis were investigated based on mitochondrial (COI and 12S rDNA) and nuclear (ITS1+5.8S+ITS2) genome regions. The sister relationship of Hirudo orientalis and H. medicinalis was revealed with a high posterior probability. A broad and patchy distribution with minor genetic differences was observed in populations of H. orientalis along the central and Middle Eastern parts of Asia. The known distribution range occurred in topographically heterogeneous landscapes around the Caspian Sea. The demographic analysis suggests the selection of the COI locus under unfavourable respiratory conditions, but population size expansion cannot be fully rejected. The genetic variation trend indicated northward dispersal. Higher haplotype diversity in the South Caspian region potentially suggests the area as a historical refugium for the species. The vast dispersal is assumed to occur after the Pleistocene glaciations via vertebrate hosts.

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.

Hirudins and hirudin-like factors in Hirudinidae: implications for function and phylogenetic relationships

Haematophagous leeches express a broad variety of bioactive factors that are released from the salivary gland cells into the wound of a host during feeding. Among these, hirudin is probably the best studied factor and, moreover, the only one that has successfully made the transition from nature to clinical use. Many components of the leech saliva still remain either poorly characterized or yet completely unknown. Only recently, a new class of leech-derived factors has been discovered in Hirudo medicinalis, the hirudin-like factors (HLFs). HLFs comprise typical structural features of hirudin but lack others. We were able to verify the expression of HLFs not only in two additional species of the genus Hirudo, but also in Hirudinaria manillensis. Various phylogenetic analyses based on gene and protein sequences support a sister group relationship between hirudins and HLFs. Although potential molecular targets of HLFs remain unknown, the presence of multiple isoforms in individual leeches of different genera points to key functions in the regulation of several processes associated with the blood-sucking life style of leeches.

More than just one: multiplicity of Hirudins and Hirudin-like Factors in the Medicinal Leech, Hirudo medicinalis

Blood-sucking leeches like the medicinal leech, Hirudo medicinalis, have been used for medical purposes since ancient times. During feeding, medicinal leeches transfer a broad range of bioactive substances into the host's wound to prevent premature hemostasis and blood coagulation. Hirudin is probably the best known of these substances. Despite its long history of investigation, recombinant production and clinical use, there still exist conflicting data regarding the primary structure of hirudin. Entirely unclear is the potential biological significance of three different subtypes and many isoforms of hirudins that have been characterized so far. Furthermore, there is only incomplete information on their cDNA sequences and no information at all on gene structures and DNA sequences are available in the databases. Our efforts to fill these gaps revealed the presence of multiple hirudin-encoding genes in the genome of Hirudo medicinalis. We have strong evidence for the expression of all three subtypes of hirudin within individual leeches and for the expression of additional hirudins or hirudin-like factors that may have different biological functions and may be promising candidates for new drugs.

First record of Limnatispaluda (Hirudinida, Arhynchobdellida, Praobdellidae) from Kazakhstan, with comments on genetic diversity of Limnatis leeches

Background

Sawyer (1986) included three species in the nasal leech genus LimnatisMoquin-Tandon 1827: Limnatisnilotica (Savigny 1822), LimnatisbacescuiManoleli 1972 and Limnatispaluda (Tennent 1859). The first and last species have mainly been identified in Middle Eastern countries (e.g. Kinzelbach and Rückert 1985). The second species has been identified only in Romania Dobruja (Manoleli 1972). Although Limnatis leeches are well known species of endoparasitic leeches, Limnatisnilotica was recorded only once in Kazakhstan (Lukin 1976).

New information

Specimens of the genus Limnatis from Almaty Province, Kazakhstan are identified as Limnatispaluda. This is the first record of Limnatispaluda from Kazakhstan. Mitochondrial COI and 12S data demonstrated that the present specimens are genetically close to an Israeli specimen identified as Limnatisnilotica. In addition, molecular data suggest that some Limnatis specimens whose DNA sequences have been reported were misidentified. According to the observed phylogenetic relationships, the taxonomic status of the known Limnatis species should be revisited.

Ultrastructural study of spermatogenesis and sperm in the African medicinal leech Hirudo troctina Johnson, 1816 (Annelida, Hirudinida)

This paper presents the process of spermatogenesis in the leech Hirudo troctina Johnson, 1816 using light, fluorescent and transmission electron microscopy. At the onset of spermatogenesis in testes, the pear-shaped spermatogonia divide mitotically without full cytokinesis and as a result isogenic groups are formed (clusters, clones) with 2, 4, 8, 16, 32, 64, 128 spermatogonia and, finally, 256 primary spermatocytes occur. The final meiotic divisions of spermatocytes give rise to clones with 1024 spermatids. There are hundreds of developing germ-line clones in each testis. In each clone, the male germ cells divide in full synchrony and they are in the same phase of spermatogenesis. During complex spermiogenesis each spermatid becomes a filiform spermatozoon with a helicoid nucleus, which is characterized by the presence of a long acrosome with two regions - anterior and posterior, which are followed by a helicoid nucleus, a midpiece with only one mitochondrion and a long flagellum. Our results were compared to those on other clitellate annelids that have been studied to date, especially to sperm formation in Hirudo medicinalis Linnaeus, 1785. Only minor differences were found in the length and the diameter of different organelles and the number of spermatids in germ-line clones.

Fauna Europaea: Annelida - Hirudinea, incl. Acanthobdellea and Branchiobdellea

Fauna Europaea provides a public web-service with an index of scientific names (including important synonyms) of all living European land and freshwater animals, their geographical distribution at country level (up to the Urals, excluding the Caucasus region), and some additional information. The Fauna Europaea project covers about 230,000 taxonomic names, including 130,000 accepted species and 14,000 accepted subspecies, which is much more than the originally projected number of 100,000 species. This represents a huge effort by more than 400 contributing specialists throughout Europe and is a unique (standard) reference suitable for many users in science, government, industry, nature conservation and education.

Hirudinea is a fairly small group of Annelida, with about 680 described species, most of which live in freshwater habitats, but several species are (sub)terrestrial or marine. In the Fauna Europaea database the taxon is represented by 87 species in 6 families. Two closely related groups, currently treated as distinct lineages within the Annelida, are the Acanthobdellea (2 species worldwide, of which 1 in Europe) and the Branchiobdellea (about 140 species worldwide, of which 10 in Europe). This paper includes a complete list of European taxa belonging to the Hirudinea, Acanthobdellea and Branchiobdellea. Recent research on a limited number of taxa suggests that our current appreciation of species diversity of Hirudinea in Europe is still provisional: on the one hand, cryptic, unrecognised taxa are expected to emerge; on the other, the status of some taxa currently treated as distinct species deserves revisiting.

Morphological and genetic variations of the freshwater leech, Hirudinaria spp., in Peninsular Malaysia

In this study the genetic diversity of local freshwater leeches (Hirudinaria spp.) was inferred using mtDNA COI gene analysis and compared with the gross external variations of 26 freshwater leech specimens obtained from the wild and leech farms. Based on a neighbor-joining tree generated from 516 COI base sequences, four distinct clades of Hirudinaria were seen with interspecific genetic divergence in the range of 7.6-14.5%. The external morphological variations based on the presence of stripes, location of gonopores, and anus separated the samples into four morphologically distinct groups matching the four clades obtained from the molecular data. Two black stripes at the ventral region were observed only in specimens found clustered with clades that contained the GenBank-reported H. manillensis, whereas the brown or dark green coloration without stripes on the ventral region was seen in samples that clustered with H. javanica and H. bpling clades.

Regional and segmental differences in the embryonic expression of a putative leech Hox gene, Lox2, by central neurons immunoreactive to FMRFamide-like neuropeptides

We performed immunofluorescence experiments using a rat polyclonal antibody on formaldehyde-fixed whole-mount embryos to characterize the expression of a putative leech Hox gene, Lox2, during embryonic development. The main goal was to determine whether the differentiation of subsets of FMRFamide-like immunoreactive (FLI) neurons coincide with the expression domain of Lox2. The earliest expression of Lox2 was detected in relatively large, prominent nuclei in the posterior region at embryonic day 4, a very early stage. Lox2 expression was also detected in subsets of central neurons (neurons located in the CNS) located in midbody ganglia 6 (M6)-M21. In addition, Lox2 was expressed by a number of segment-specific and segmentally repeated central FLI neurons. Lox2-positive FLI neurons of interest included some of those previously identified: the rostral most ventral (RMV) neurons, the circular ventral (CV) neurons, and cell 261. The paired RMVs, which are located in all midbody ganglia, expressed Lox2 only in M7-M19. The CV neurons, specialized motor neurons that innervate the circular ventral muscles of the body wall, expressed Lox2 in M7-M19. The putative cell 261 expressed Lox2 in M7-M12, where Lox1 is also expressed. FMRFamide staining in putative segmental homologs of cell 261 was not detected in other segmental ganglia. Our results suggest a role for Lox2 in very early embryonic development (before the formation of the CNS), and in the differentiation of segmentally repeated and region-specific FLI neurons.

Three species of land leeches from Taiwan, Haemadipsa rjukjuana comb. n., a new record for Haemadipsa picta Moore, and an updated description of Tritetrabdella taiwana (Oka)

Three species of land leeches, including a new combination Haemadipsa rjukjuanacomb. n., a new record for Haemadipsa picta Moore, as well as an updated description for Tritetrabdella taiwana (Oka), are reported in this study. Morphological characters and DNA barcode analysis were used to identify these species. In addition, since Haemadipsa rjukjuana had been regarded as a variety of the Japanese land leech Haemadipsa japonica for a century, morphological differences between these two species were also compared.

Unsuspected diversity of Niphargus amphipods in the chemoautotrophic cave ecosystem of Frasassi, central Italy

Background

The sulfide-rich Frasassi caves in central Italy contain a rare example of a freshwater ecosystem supported entirely by chemoautotrophy. Niphargus ictus, the sole amphipod species previously reported from this locality, was recently shown to host the first known case of a freshwater chemoautotrophic symbiosis. Since the habitat of N. ictus is highly fragmented and is comprised of streams and lakes with various sulfide concentrations, we conducted a detailed study to examine the potential genetic diversity of this species within Frasassi.

Results

By sequencing one nuclear (ITS) and two mitochondrial (COI and 12S) regions, we show that four partially sympatric Niphargus clades are present in Frasassi. Morphological and behavioral data obtained for three of these clades are perfectly congruent with this molecular delineation and make it possible to distinguish them in the field. Phylogenetic analyses of 28S ribosomal DNA sequences reveal that, among the four clades, only two are closely related to each other. Moreover, these four clades occupy distinct niches that seem to be related to the chemical properties and flow regimes of the various water bodies within Frasassi.

Conclusions

Our results suggest that four distinct Niphargus species are present in Frasassi and that they originated from three or four independent invasions of the cave system. At least two among the four species harbor Thiothrix epibionts, which paves the way for further studies of the specificity and evolutionary history of this symbiosis.

Stratified bacterial community in the bladder of the medicinal leech, Hirudo verbana

Most animals harbour symbiotic microorganisms inside their body, where intimate interactions occur between the partners. The medicinal leech, Hirudo verbana, possesses 17 pairs of excretory bladders that harbour a large number of intracellular and extracellular symbiotic bacteria. In this study, we characterized the bladder symbionts using molecular phylogenetic analyses, transmission electron microscopy (TEM) and fluorescence in situ hybridization (FISH). Restriction fragment length polymorphism (RFLP) and sequence analyses of 16S rRNA gene clone libraries suggested that six bacterial species co-colonize the leech bladders. Phylogenetic analyses revealed that these species belong to the alpha-Proteobacteria (Ochrobactrum symbiont), beta-Proteobacteria (Beta-1 and Beta-2 symbionts), delta-Proteobacteria (Bdellovibrio symbiont) and Bacteroidetes (Niabella and Sphingobacterium symbionts). Species-specific PCR detection and FISH confirmed the localization of the symbiotic bacteria in the bladders. The Ochrobactrum, Beta-1, Bdellovibrio and Sphingobacterium symbionts were consistently detected in 13 leeches from two populations, while infection rate of the other symbionts ranged between 20% and 100% in the two leech populations. Transmission electron microscopy observations of the bladders revealed epithelial cells harbouring a number of intracellular bacilli and an additional type of extracellular, rod-shaped bacteria in the luminal region. Fluorescence in situ hybridization with group-specific oligonucleotide probes revealed the spatial organization of the bacterial species in the bladder: the Ochrobactrum symbiont was located intracellularly inside epithelial cells; the Bacteroidetes were localized close to the epithelium in the lumen of the bladder; and the Bacteroidetes layer was covered with dense beta-proteobacterial cells. These results clearly demonstrate that a simple but organized microbial community exists in the bladder of the medicinal leech.

Application of the comet assay and detection of DNA damage in haemocytes of medicinal leech affected by aluminium pollution: a case study

This report describes an investigation of genotoxic effects in medicinal leech (Hirudo verbana) exposed to water and sediment of Lake Njivice (Krk Island, Croatia) contaminated by aluminium compounds. The levels of primary DNA damage in leech haemocytes and loss of DNA integrity caused by acute and chronic exposure to contaminated water and sediment were investigated using the alkaline comet assay. Genotoxic effects induced by acute exposure to contaminants were evaluated on leech haemocytes and blood cells of fish and mouse treated ex vivo. The effects of chronic exposure were assessed on haemocytes sampled from an animal kept under laboratory conditions on contaminated water and sediment for 180 days. The results indicate the DNA damaging potential of aluminium compounds present in an excess amount in tested samples.

Genetic variation in the popular lab worm Lumbriculus variegatus (Annelida: Clitellata: Lumbriculidae) reveals cryptic speciation

Genetic variation in the freshwater oligochaete Lumbriculus variegatus from Europe, North America and Japan was studied by sequencing and analysing the mitochondrial 16S and COI genes, and the nuclear ITS region. What hitherto has been regarded as L. variegatus was found to consist of at least two distinct clades (I and II), both of which occur in Europe as well as North America (clade I also in Japan). Specimens from a single locality in Sierra Nevada, California, also morphologically identified as L. variegatus, represent a third clade, which appears to be more closely related to clade II than to clade I, based on 16S data only. Average COI genetic distances were 17.7% between clades I and II, 0.6% within clade I, and 1.3% within clade II. Further, for these two clades, the mitochondrial (16S and COI) gene trees, which consider only the maternal lineages, are congruent with the ITS gene tree, which is the result of recombinations of paternal as well as maternal genomes. Finally, chromosome counts revealed clade I specimens to be highly polyploid, and clade II specimens to be diploid. We therefore conclude that clades I-II are separately evolving lineages, and that they should be regarded as separate species. This will have to be taken into account in the continued use of L. variegatus as a model organism in biological sciences.