Jaw anatomy of the blood‐sucking leeches, Hirudinea Limnatis nilotica and Hirudo medicinalis , and its relationship to their feeding habits

Unraveling the structure, chemical composition, and conserved signaling in leech teeth

Unlike vertebrates, the number of toothed taxa in invertebrates is very few, with leeches being the only tooth-bearing organisms in the phylum Annelida. Copious studies have been conducted regarding vertebrate teeth; however, studies regarding the structure and function of invertebrate teeth are limited. In this study, the tooth structure of leeches, specifically Hirudo nipponia and Haemadipsa rjukjuana, was revealed, which showed sharp and pointed teeth along the apex of three jaws. Understanding conserved signaling regulations among analogous organs is crucial for uncovering the underlying mechanisms during organogenesis. Therefore, to shed light on the evolutionary perspective of odontogenesis to some extent, we conducted de novo transcriptome analyses using embryonic mouse tooth germs, Hirudo teeth, and Helobdella proboscises to identify conserved signaling molecules involved in tooth development. The selection criteria were particularly based on the presence of tooth-related genes in mice, Hirudo teeth, and Helobdella proboscis, wherein 4113 genes were commonly expressed in all three specimens. Furthermore, the chemical nature of leech teeth was also examined via TEM-EDS to compare the chemical composition with vertebrate teeth. The examination of tissue-specific genetic information and chemical nature between leeches and mice revealed chemical similarities between leech and mice teeth, as well as conserved signaling molecules involved in tooth formation, including Ptpro, Prickle2, and Wnt16. Based on our findings, we propose that leech teeth express signaling molecules conserved in mice and these conserved tooth-specific signaling for dental hard tissue formation in mice would corresponds to the structural formation of the toothed jaw in leeches.

A Bioinspired and Cost-Effective Device for Minimally Invasive Blood Sampling

Conventional venipuncture is invasive and challenging in low and middle-income countries. Conversely, point-of-care devices paired with fingersticks, although less invasive, suffer from high variability and low blood volume collection. Recently approved microsampling devices address some of these issues but remain cost-prohibitive for resource-limited settings. In this work, a cost-effective microsampling device is described for the collection of liquid blood with minimal invasiveness and sufficient volume retrieval for laboratory analyses or immediate point-of-care testing. Inspired by the anatomy of sanguivorous leeches, the single-use device features a storage compartment for blood collection and a microneedle patch hidden within a suction cup. Finite Element Method simulations, corroborated by mechanical analyses, guide the material selection for device fabrication and design optimization. In piglets, the device successfully collects ≈195 µL of blood with minimal invasiveness. Additionally, a tailor-made lid and adapter enable safe fluid transportation and integration with commercially available point-of-care systems for on-site analyses, respectively. Taken together, the proposed platform holds significant promise for enhancing healthcare in the pediatric population by improving patient compliance and reducing the risk of needlestick injuries through concealed microneedles. Most importantly, given its cost-effective fabrication, the open-source microsampling device may have a meaningful impact in resource-limited healthcare settings.

Functional morphology of the suckers and teeth of the medicinal leech Hirudo verbana Carena, 1820 (Annelida; Clitellata; Hirudinida): A scanning electron microscope study

In this study, the triple jaws and suckers of the leeches belonging to the Hirudo verbana Carena, 1820 (Annelida; Clitellata; Hirudinida) were examined using the stereomicroscopy and scanning electron microscopy. In H. verbana, suckers are seen on the first annulus and last annulus of the body. The mouth opens in the center of the front suction cup, and behind this opening is a movable triple jaw apparatus with many teeth. The posterior sucker disc consists of the last seven body segments and lacks an opening. The shape of the jaw is trignatous. The pharynx is equally located around of the three muscular jaws. The jaws are muscular covered with cuticle and carry a row of teeth arranged at the tip. In this study, it was determined that secretory canal holes were identified between the teeth. The results show that the size of teeth determines long-term bleeding so revealing the structure and working mechanism of the teeth has importance for medicinal leeches. At the same time, the difference of teeth and jaw structures of leeches may be a criterion in the classification of medicinal leeches.

Experimental Investigation on the Morphology and Adhesion Mechanism of Leech Posterior Suckers

The posterior sucker of a leech represents a fascinating natural system that allows the leech to adhere to different terrains and substrates. However, the mechanism of adhesion and desorption has not yet to be elucidated. In order to better understand how the adhesion is performed, we analyzed the surface structure, adsorption movements, the muscles’ distribution, physical characteristics, and the adsorption force of the leech posterior suckers by experimental investigation. Three conclusions can be drawn based on the obtained experimental results. First, the adhesion by the posterior sucker is wet adhesion, because the surface of the posterior sucker is smooth and the sealing can only be achieved on wet surfaces. Second, the deformation texture, consisting of soft collagen tissues and highly ductile epidermal tissues, plays a key role in adhering to rough surfaces. Finally, the adhesion and desorption is achieved by the synergetic operation of six muscle fibers working in different directions. Concrete saying, directional deformation of the collagen/epithermal interface driven by spatially-distributed muscle fibers facilitates the excretion of fluids in the sucker venter, thus allowing liquid sealing. Furthermore, we found that the adhesion strength is directly related to the size of the contact surface which is generated and affected by the sucker deformation. Such an underlying physical mechanism offers potential cues for developing innovative bio-inspired artificial adhesion systems.

Quo vadis venomics? A roadmap to neglected venomous invertebrates

Venomics research is being revolutionized by the increased use of sensitive -omics techniques to identify venom toxins and their transcripts in both well studied and neglected venomous taxa. The study of neglected venomous taxa is necessary both for understanding the full diversity of venom systems that have evolved in the animal kingdom, and to robustly answer fundamental questions about the biology and evolution of venoms without the distorting effect that can result from the current bias introduced by some heavily studied taxa. In this review we draw the outlines of a roadmap into the diversity of poorly studied and understood venomous and putatively venomous invertebrates, which together represent tens of thousands of unique venoms. The main groups we discuss are crustaceans, flies, centipedes, non-spider and non-scorpion arachnids, annelids, molluscs, platyhelminths, nemerteans, and echinoderms. We review what is known about the morphology of the venom systems in these groups, the composition of their venoms, and the bioactivities of the venoms to provide researchers with an entry into a large and scattered literature. We conclude with a short discussion of some important methodological aspects that have come to light with the recent use of new -omics techniques in the study of venoms.

Avulsion of the auricle in an anticoagulated patient: is leeching contraindicated? A review and a case

Amputation of the auricle is a periodic occurrence leading to disfigurement if not treated properly. Venous stasis is a common complication in reattachments and requires decongestant and anticoagulant treatment. Today, leech therapy is the treatment of choice. Common problems are that it is not available everywhere and that it is usually contraindicated in anticoagulated patients. The peculiarities of leech therapy and the various aspects of surgical management are reviewed. A case of a partial amputation of the auricle in a patient under concomitant anticoagulation therapy with warfarin is presented. The amputated part was reattached in another hospital without microvascular anastomosis. The patient presented to our department with early signs of venous congestion. Leech therapy was started 35 hours after trauma, and the patient continued his anticoagulation therapy. With this treatment, 90% of the amputated part was rescued. The anticoagulation therapy of the patient may have played an important role in the first hours after reattachment, preventing capillary thrombosis and in consequence facilitating the minimal oxygenation necessary. The claim that anticoagulation therapy is a contraindication to leeching should be questioned in cases of reattachments in well-controllable locations without arterial anastomosis.

Phylogenetic placement of a new species of Asian buffalo leech (Arhynchobdellida:Hirudinidae), and confirmation of human-mediated dispersal of a congener to the Caribbean

A new species of the genus Hirudinaria from Thailand is distinguished from its congeners by the dorsal colour pattern and reproductive structures. Scanning electron microscopy provided novel information on the jaw morphology of Hirudinaria bpling, sp. nov. and also of the previously described Hirudinaria manillensis. During the study, the genus name Hirudinaria in reference to leeches was found to be a homonym and, in this case, precedence is reversed. Phylogenetic analyses based on the nuclear genes 18S rDNA and 28S rDNA as well as the mitochondrial genes 12S rDNA and cytochrome c oxidase I, supported the new species as nested within the monophyletic genus Hirudinaria. Two individuals from the Caribbean, nominally identified as H. manillensis, included in the phylogenetic analyses were strongly supported as members of that species.