Nerve Ring Research Articles

Description of Aphelenchoides yixingensis n. sp. (Tylenchina: Aphelenchoididae) found in Pinus massoniana from China, and proposal for genus Ptychaphelenchus as a synonym of Aphelenchoides

Summary Aphelenchoides yixingensis n. sp. found in Chinese red pine (Pinus massoniana) in Yixing city, Jiangsu Province, P.R. China, is described. It is characterised by a very slim body (a = 50.8 (41.3-63.8) and 49.3 (42.3-55.1) for males and females, respectively), three (occasionally five) lateral lines in the lateral field, a short stylet (9-12 μm), the excretory pore located at the level of nerve ring, the vagina is not sclerotised and the vulva has slightly protruding lips and lacks a flap, the post-uterine sac is well developed and forms ca 29.0% (24.1-34.1%) of the vulva to anus distance. The spicules are smoothly arcuate, the apex and rostrum rounded and short, and the dorsal limb is 20.5 (16.9-22.2) μm long, the distal end bluntly rounded. Spicule sheath-like structure is present, triangular and outstretched when heat-killed in some individuals. The male tail bears three pairs (2 + 2 + 2) of caudal papillae. The tail of both sexes is sub-cylindrical, the terminus bearing a bluntly pointed mucron with tiny nodular protuberances, mainly at the distal part. The new species belongs to the Group 2 category of Aphelenchoides species sensu Shahina and is defined as A2-B1-C1-D1-E2-F2 according to the categorisation codes of OEPP/EPPO. Phylogenetic analysis based on 18S and 28S D2-D3 of rDNA, along with ITS and mtCOI, confirmed its status as a new species. A proposal for genus Ptychaphelenchus as a synonym of Aphelenchoides is also discussed.

Discovery and Characterization of Four Aphelenchid Species from Cultivated Regions of Southern Alberta, Canada.

The nematode family Aphelenchoididiae is considered fungal-feeding, predatory, or root hair feeders. Some members of this family are universally present in agricultural landscapes and are an integral part of soil health and conservation studies. In the present soil nematode biodiversity survey, we detected four species of the genera Aphelenchus, Aphelenchoides, and Robustodorus. Because fungal-feeding nematodes from southern Alberta have not previously been reported, we conducted a detailed morphological and molecular investigation, identifying these species as Aphelenchus avenae, Aphelenchoides limberi, Aphelenchoides prairiensis n. sp. and Robustodorus paramegadorus n. sp. The first two species we document as new records from southern Alberta, whereas A. prairiensis n. sp. and R. paramegadorus n. sp. we describe in detail as new taxa. Briefly, A. prairiensis n. sp. is an amphimictic species having 4 lateral lines; hemispherical anteriorly flattened lip region; delicate stylet and swelling-like stylet knobs; excretory pore at the posterior edge of nerve ring. Female tail conical, gradually tapering towards a truncated end with single mucro. Spicule 23.0 (20.0-25.0) µm long having elongated rounded condylus, small, blunt conical rostrum, and lamina that gradually tapers towards the rounded distal end; three pairs of caudal papillae were present on the male tail. Robustodorus paramegadorus n. sp., is a parthenogenetic species with 3 lines in the lateral fields; lip region rounded, anteriorly flattened; stylet robust, with knobs rounded to bean-shaped; excretory pore located posterior to nerve ring; reproductive components were quite indiscernible with a short 24.0 (18.0-27.0) µm post-vulval uterine sac; tail conical, ending with pointed to wedge-shaped tip. We performed molecular characterizations for each species and constructed phylogenetic trees to study the phylogenetic relationship of these aphelenchid species. The discovery of A. prairiensis n. sp. and R. paramegadorus n. sp. indicates that soil nematode diversity is relatively unexplored in southern Alberta. The findings of this study will significantly enhance the identification processes and may contribute towards future soil health and biodiversity efforts.

Neuronal cell populations in circumoral nerve ring of sea cucumber Apostichopus japonicus: Ultrastructure and transcriptional profile

The echinoderm nervous system has been studied as a model for understanding the evolution of the chordate nervous system. Neuronal cells are essential groups that release a ‘cocktail’ of messenger molecules providing a spectrum of biological actions in the nervous system. Among echinoderms, most evidence on neuronal cell types has been obtained from starfish and sea urchin. In sea cucumbers, most research has focused on the location of neuronal cells, whereas their transcriptional features have rarely been investigated. Here, we observed the ultrastructure of neuronal cells in the sea cucumber, Apostichopus japonicus. The transcriptional profile of neuronal cells from the circumoral nerve ring (CNR) was investigated using single-cell RNA sequencing (scRNA-seq), and a total of six neuronal cell types were identified. 26 neuropeptide precursor genes (NPPs) and 28 G-protein-coupled receptors (GPCR) were expressed in the six neuronal cell types, comprising five NPP/NP-GPCR pairs. Unsupervised pseudotime analysis of neuronal cells showed their different differentiation status. We also located the neuronal cells in the CNR by immunofluorescence (IF) and identified the potential hub genes of key cell populations. This broad resource serves as a valuable support in the development of cell-specific markers for accurate cell-type identification in sea cucumbers. It also contributes to facilitating comparison across species, providing a deeper understanding of the evolutionary processes of neuronal cells.

Clarifying the Functional Role of Serotonin in Meloidogyne graminicola Host Plant Parasitism by Immunolocalization and RNA Interference.

Serotonin (5-hydroxytryptamine) is an essential neurotransmitter involved in regulating various behaviors in plant-parasitic nematodes, including locomotion, egg laying, feeding, and mating. However, the functional role of serotonin in root-knot nematode invasion of host plants and the molecular mechanisms underlying feeding behavior remain poorly understood. In this study, we tested the effects of exogenous serotonin and the pharmacological compounds fluoxetine and methiothepin on the feeding behaviors of Meloidogyne graminicola. Our results suggested that M. graminicola possesses an endogenous serotonin signaling pathway and that serotonin plays a crucial role in modulating feeding behaviors in M. graminicola second-stage juveniles. We also identified and cloned the serotonin synthesis enzyme tryptophan hydroxylase (Mg-tph-1) in M. graminicola and investigated the role of endogenous serotonin by generating RNA interference nematodes in Mg-tph-1. Silencing Mg-tph-1 substantially reduced nematode invasion, development, and reproduction. According to the immunostaining results, we speculated that these serotonin immunoreactive cells near the nerve ring in M. graminicola are likely homologous to Caenorhabditis elegans ADFs, NSMs, and RIH serotonergic neurons. Furthermore, we investigated the impact of phytoserotonin on nematode invasion and development in rice by overexpressing OsTDC-3 or supplementing rice plants with tryptamine and found that an increase in phytoserotonin increases nematode pathogenicity. Overall, our study provides insights into the essential role of serotonin in M. graminicola host plant parasitism and proposes that the serotonergic signaling pathway could be a potential target for controlling plant-parasitic nematodes.

Further studies on the diversity of Cylicospirura Vevers, 1922 (Nematoda: Spirocercidae) in African carnivores, with description of a new species.

Cylicospirura Vevers, 1922 is a genus of gastrointestinal spirurid nematodes parasitizing mainly felid but also canid, hyaenid and dasyurid hosts. Presently, 11 species are recognized worldwide, of which 4, Cylicospirura subaequalis, Cylicospirura felinea, Cylicospirura crocutae and Cylicospirura pardalis, have been recorded from African carnivores. In the present study, we describe Cylicospirura phiri n. sp. from hyaenas, namely Crocuta crocuta (type host) in Zimbabwe and Hyaena hyaena in Cameroon. The new species is the second species in the genus with bicuspid teeth. Furthermore, it can be distinguished from its congeners by a combination of characters, such as the absence of accessory teeth, the length and shape of the muscular oesophagus, position of the nerve ring, deirids and excretory pore in relation to the muscular oesophagus, the position of the vulva, spicule length and the shape of the female tail. Additionally, based on new material, detailed morphological descriptions are provided for C. crocutae and C. pardalis whose original descriptions were based on fragmented material. The material from Felis lybica, currently deposited as C. subaequalis, is described as C. felinea. First-time scanning electron micrographs are presented for the 4 species confirmed in African carnivores.

The outer kinetochore components KNL-1 and Ndc80 complex regulate axon and neuronal cell body positioning in the C. elegans nervous system.

The KMN (Knl1/Mis12/Ndc80) network at the kinetochore, primarily known for its role in chromosome segregation, has been shown to be repurposed during neurodevelopment. Here, we investigate the underlying neuronal mechanism and show that the KMN network promotes the proper axonal organization within the C. elegans head nervous system. Postmitotic degradation of KNL-1, which acts as a scaffold for signaling and has microtubule-binding activities at the kinetochore, led to disorganized ganglia and aberrant placement and organization of axons in the nerve ring - an interconnected axonal network. Through gene-replacement approaches, we demonstrate that the signaling motifs within KNL-1, responsible for recruiting protein phosphatase 1, and activating the spindle assembly checkpoint are required for neurodevelopment. Interestingly, while the microtubule-binding activity is crucial to KMN's neuronal function, microtubule dynamics and organization were unaffected in the absence of KNL-1. Instead, the NDC-80 microtubule-binding mutant displayed notable defects in axon bundling during nerve ring formation, indicating its role in facilitating axon-axon contacts. Overall, these findings provide evidence for a noncanonical role for the KMN network in shaping the structure and connectivity of the nervous system in C. elegans during brain development.

Evaluation of schistosoma mansoni nervous system using confocal laser electron microscopy: nerve sensilla and FMRFamide while referring to F-actin abundance

ABSTRACT The chaetotaxy distribution pattern of surface nerve sensilla on the surface of both Schistosoma mansoni and S. haematobium was studied after exposure to silver nitrate treatment followed by light. This distribution pattern could not be achieved earlier due to namelessness, crowded nerve sensilla and twist of most parasites. In S. mansoni, silver impregnation technique displays nerves as ventral nerve cord, ventral sucker nerve that branches to three rings which innervate the ventral sucker. This technique shows the oral sucker ring, ring commissures and bipolar or multipolar nerve cells detected dorsally. In S. haematbium, nerves stained in S. mansoni were also stained in addition to the oral nerve and oral sucker ring. Furthermore, a number of crucial nerves were identified and their innervations to relevant organs were thoroughly examined. A confocal anti-FMRF amide technique was applied to whole-mount worms of both species. In addition to the general tegumental muscles stated previously and stated in this research specific nerves were also described and referred to a specific organ that assumed to innervate. In conclusion, the findings of the current study differentiate between S. mansoni and S. mansoni using chaetotaxy map as a step for spotlighting on FMRF amidergic components as antihelmintic target in future.

Comparison of the Efficacy Between Regional Nerve Block and Ring Block as Local Anesthetic Techniques for Platelet-Rich Plasma Treatment.

Introduction Platelet-rich plasma (PRP), a solution of concentrated platelets, has been widely used to promote wound repair and tissue regeneration. In the treatment of pattern hair loss, platelets in PRP secrete an abundance of growth factors, including platelet-derived growth factor (PDGF), fibroblast growth factor(FGF), and many more, which stimulate and increase signaling molecules and accelerate cell proliferation. In the PRP treatment for hair regrowth, the supratrochlear nerve (STN) block and supraorbital nerve (SON) block are given to anesthetize the scalp up to the vertex except for the temporal region. The ring block is the common local anesthetic technique usedby infiltrating local anesthetic agents around the target area. The primary objectives were to compare the pain and anesthetic success rates produced by regional nerve blocks and ring blocks. Materials and methods A sample size of 100 patients undergoing PRP treatment for hair regrowth were taken as the subjects for the study. Patients were allotted into two groups by randomization. Group 1 was given regional nerve blocks as the anesthetic technique used for local anesthesia, and group 2 was given ring blocks. In the study group, STN and SON blocks as the regional nerve blocks were given 2% lignocaine with 1:80000 adrenaline to anesthetize the area, and the PRP was injected from the anterior hairline up to the vertex of the scalp, not involving the occipital and temporal regions. In the control group, a ring block was given for the same procedure. Participants from both groups were assessed for the pain and analgesia caused by ring block and regional nerve blocks using the visual analog scale (VAS). Results A mean rank of 30.28 was observed for the regional nerve block technique, and a mean rank of 70.72 was observed for the ring block technique. A p-value of 0.00 that is <0.05 was observed, which shows there is a significant difference in the pain and the analgesia experienced by the subjects between the two groups, during and three hours after the procedure. Conclusion PRP is one of the most commonly used treatments for hair regrowth. The ring block is the common local anesthetic technique used for producing anesthesia, while regional nerve blocks are more effective in producing local anesthesia. This study proves that STN and SON blocks are better anesthetic techniques than the ring block technique for PRP treatment in hair growth.

New deep-sea species of Aborjinia (Nematoda, Leptosomatidae) from the North-Western Pacific: an integrative taxonomy and phylogeny.

Marimermithid nematodes parasitising invertebrates are mainly found in the deep-sea environments. Several adult and juvenile specimens marimermithids of the genus Aborjinia have been found in bottom sediments and inside Polychaeta during recent cruises to the Kuril-Kamchatka trench and the Kuril Basin (the Sea of Okhotsk). New species are described based on integrative study. Aborjiniaprofundasp. nov. differs from A.eulagiscae by the location of the ventral gland cell bodies (posterior to the nerve ring vs posterior to the cardia), by the smaller body size (23-28 mm vs 103-132 mm) and shorter tail (193-263 µm vs 500-850 µm). BI and ML phylogenetic analyses based on 18S and 28S rDNA suggest that genus Aborjinia belongs to the family Leptosomatidae. Based on molecular and morphological characters the new genus Paraborjiniagen. nov. is proposed for A.corallicola. Within the family Leptosomatidae the new genus differs from all genera except Aborjinia by its endoparasitic lifestyle and hologonic ovaries. Paraborjiniagen. nov. differs from Aborjinia by the position of cephalic sensitive organs (outer labial and cephalic papillae in two separate circles vs outer labial and cephalic papillae in one circle) and by the parasitic adult (vs free-living in Aborjinia).

New record of Philometra species from the marine edible fish Terapon jarbua collected from the Sindh, Arabian Sea, Pakistan.

Diseases in fish due to helminth parasites, especially Philometra species, are the primary worry in aquaculture. Philometra are responsible for health problem in fishes they directly affect fish growth and population parameters. A comprehensive survey was conducted involving the examination of the marine fish species Terapon jarbua, gathered from the coastal waters of Sindh, Pakistan In this research different Philometra species from marine fish Terapon jarbua during 2021 and 2022. Philometra nematodes, belonging to the family Philometridae, are common parasitic organisms inhabiting both marine and freshwater environments. Their prevalence, particularly when existing in high numbers within host organisms, can lead to severe and potentially lethal consequences. Employing light microscopy techniques, diverse species of Philometra were identified, including Philometra teraponi, P. jarbuai, P. arabiai, P. karachii, and P. awarii, localized primarily within the ovaries of the host fish. A total of 140 fish samples were examined and 76 were infected. The intensity of infected fish was 54.28%. The identification process encompassed meticulous analysis of crucial parameters, such as body size, esophagus length, positioning of the nerve ring, dimensions of the ventriculus, and ligament size. Intriguingly, the parasites were found in varying contexts; while some were free within the ovaries, others were embedded within tissues, inducing severe muscular dystrophy. This research presents novel findings of Philometra nematodes in the marine waters of Pakistan, extending their host and geographical distribution records. Future studies are needed to better evaluate and describe the dynamics and the epidemiology of Philometra infection in wild and cultured fish species.

Exploring an immortal Turritopsis sp. as a less conventional natural system for study of aging

AimGiven its excellent capability of escaping from unavoidable harm and death, Turritopsissp. (T. sp.) has captured the attention and fascination of scientists as a less conventional tool for aging research. The current study introduces a method for establishment of a research model and comprehensive transcriptomic analysis to reveal the structural and functional diversity of T. sp. MethodsT. sp. medusae collected from the Pacific Ocean near Japan were reared using a common laboratory setting. Tissues of the gastrovascular cavity part (GP) and nerve ring part (NP) were collected, and total RNA was extracted. Bulk RNA-seq was performed to compare the different transcriptome landscapes between GP and NP. ResultsThe GP fragment could be utilized for studies related to stress response and systemic senescence, while the NP fragment could be used to explore system rejuvenation, self-repair and regeneration. ConclusionsAs a less conventional system for aging research, by employing the most recently developed tools and techniques in the genomic revolution, comprehensive elucidation of the composition, development, and functions of T. sp. enabled us to explore the underlying mechanisms of the response to environmental stress and rejuvenation.

Circadian rhythm regulation in the sea cucumber Apostichopus japonicus: Insights into clock gene expression, photoperiod susceptibility, and neurohormone signaling

Sea cucumber Apostichopus japonicus displays the typical circadian rhythms. This present study investigated the molecular regulation of clock genes, as well as monoamines and melatonin, in multiple tissues of A. japonicus, responding to the photoperiod. In order to determine their pivotal role in circadian rhythms, the crucial clock genes, namely AjClock, AjArnt1, AjCry1, and AjTimeless, were identified and a comprehensive analysis of their expressions across various tissues in adult A. japonicus was conducted, revealing the potential existence of central and peripheral oscillators. Results demonstrated that the tissues of polian vesicle and nerve ring exhibited significant clock gene expression associated with the orchestration of circadian regulation, and that environmental light fluctuations exerted influence on the expression of these clock genes. However, a number of genes, such as AjArnt1 and AjCry1, maintained their circadian rhythmicity even under continuous light conditions. Moreover, we further investigated the circadian patterns of melatonin (MT), serotonin (5-HT), and dopamine (DA) secretion in A. japonicus, data that underscored the tissue-specific regulatory differences and the inherent adaptability to dynamic light environments. Collectively, these findings will provide the molecular mechanisms controlling the circadian rhythm in echinoderms and the candidate tissues playing the role of central oscillators in sea cucumbers.

Morphological and molecular characterization of Geraldius galapagoensis (Nematoda: Chambersiellidae) associated with lichens in Argentina

Lichens are symbiotic organisms, usually composed of a fungal partner, the mycobiont, and one or more photosynthetic partners, the photobiont, which is most often either a green alga or a cyanobacterium, that harbor a diverse community of invertebrates such as rotifers, tardigrades, mites, springtails, crustaceans, and nematodes. In this work, we isolated the nematode Geraldius galapagoensis (Chambersiellidae) associated with the lichen Hyperphyscia syncolla (Physciaceae) in a region of Buenos Aires Province, Argentina. This species was discovered in a tropical forest of Ecuador and is characterized mainly by a head offset by a constriction from the rest of the body, a esophagus with a cylindrical pharyngeal corpus without a median bulb, a narrow isthmus and an oval basal pharyngeal bulb with strong transverse/butterfly valve apparatus, a tail curved ventrally, ending in dorsally hooked end; the male with seven pairs of latero-ventral pre-anal papillae and three pairs of post-anal in the following positions: one pair latero-ventral and two pairs dorso-lateral and two slightly curved spicules with asymmetric manubrium with an anterior extension. The comparison of the morphometrics of our G. galapagoensis male with that of the original description shows that the body length is shorter, as are the distance of the excretory pore to the anterior end and the tail. On the other hand, the distance from the anterior end to the nerve ring and the esophagus length are greater. The head width, body diameter and spicule length are quite similar. We provide a morphological and morphometrical characterization of a G. galapagoensis second isolate and the first world report of molecular sequences belonging to this species.

A new dracunculus species (Nematoda: Dracunculoidea) in neotropical otters (Lontra longicaudis) from Argentina: morphological and molecular characterization

A new species of Dracunculus is described in wild neotropical otters, Lontra longicaudis, occurring in Corrientes, Argentina, based on morphological and molecular characteristics. Worms were located in the subcutaneous tissue from two of five investigated otters. Dracunculus jaguape n. sp. is differentiated from the 14 species of Dracunculus described from mammals and reptiles by the prominent dorsal and ventral papillae on the head; deirids posterior to nerve ring; male with long needlelike spicules and presence of gubernaculum; and long first stage larva. Phylogenetic analysis using the 18S rRNA positioned Dracunculus jaguape n. sp. in an anterior position to the rest of Dracunculus sequences available and COI positioned it in a separated clade sister to Dracunculus lutrae sequences. This is the first report on the presence of this nematode in Lontra longicaudis in Argentina.

Three new free-living marine nematode species of the family Comesomatidae from Mangrove wetlands in Jinmen County, Taiwan.

Three new free-living marine nematodes, belonging to the genera Dorylaimopsis, Comesoma and Paracomesoma are described from the mangrove wetlands of western Taiwan Island. Dorylaimopsis jinmendaoica sp. nov. is characterized by having a cuticle with lateral differentiation of longitudinal rows of two rows of larger dots in the middle of the body, a spiral amphideal fovea with 2.52.75 turns, excretory pore anterior to nerve ring and 1721 fibriform precloacal supplements. Comesoma quattuordecimsupplementata sp. nov. is characterized by having a spiral amphideal fovea with 2.52.75 turns and 14 fibriform precloacal supplements. Paracomesoma paralissum sp. nov. is characterized by having a spiral amphideal fovea with 3.0 turns and 40 fibriform precloacal supplements. Differentiating characteristics of all known male Dorylaimopsis, Comesoma and Paracomesoma species are also given.

Taxonomic and molecular characterization of a new entomopathogenic nematode species, Heterorhabditis casmirica n. sp., and whole genome sequencing of its associated bacterial symbiont

BackgroundNematodes of the genus Heterorhabditis are important biocontrol agents as they form a lethal combination with their symbiotic Photorhabdus bacteria against agricultural insect pests. This study describes a new species of Heterorhabditis.MethodsSix Heterorhabditis nematode populations were recovered from agricultural soils in Jammu and Kashmir, India. An initial examination using mitochondrial and nuclear genes showed that they belong to a new species. To describe this new species, a variety of analyses were conducted, including reconstructing phylogenetic relationships based on multiple genes, characterizing the nematodes at the morphological and morphometric levels, performing self-crossing and cross-hybridization experiments, and isolating and characterizing their symbiotic bacteria.ResultsThe newly discovered species, Heterorhabditis casmirica n. sp., shares 94% mitochondrial cytochrome C oxidase subunit I gene (COI) sequence identity with Heterorhabditis bacteriophora and Heterorhabditis ruandica, and 93% with Heterorhabditis zacatecana. Morphologically, it differs from H. bacteriophora in its infective juvenile phasmids (present vs. inconspicuous) and bacterial pouch visibility in the ventricular portion of the intestine (invisible vs. visible); genital papilla 1 (GP1) position (at manubrium level vs. more anterior), and in its b ratio (body length/neck length), c ratio (tail length/bulb width), and D% [(excretory pore/neck length) × 100]. Other morphological differences include anterior end to the nerve ring distance (77–100 vs. 121–130 μm), V% [(anterior end of vulva/body length) × 100] (46–57 vs. 41–47) in hermaphroditic females; rectum size (slightly longer than the anal body diameter vs. about three times longer), phasmids (smaller vs. inconspicuous), body length (0.13–2.0 vs. 0.32–0.39 mm), body diameter (73–150 vs. 160–220 μm), anterior end to the excretory pore distance (135–157 vs. 174–214 μm), and demanian ratios in amphimictic females. Morphological differences with H. ruandica and H. zacatecana were also observed. Furthermore, H. casmirica n. sp. did not mate or produce fertile progeny with other Heterorhabditis nematodes reported from India. It was also discovered that H. casmirica n. sp. is associated with 'Photorhabdus laumondii subsp. clarkei symbiotic bacteria.ConclusionsThe discovery of H. casmirica n. sp. provides novel insights into the diversity and evolution of Heterorhabditis nematodes and their symbiotic bacteria. This new species adds to the catalog of entomopathogenic nematodes in India.Graphical

Two Species of the Family Cyatholaimidae (Nematoda: Chromadorida) from Korea

During a survey of the Wando-gun rockpool area in Korea, two species belonging to the family Cyatholaimidae were discovered within a sponge, Hymeniacidon sinapium, and are hereby reported. Despite the monophyletic nature of the family Cyatholaimidae, it has been a topic of discussion among nematologists due to its lack of synapomorphic characteristics and overlapping generic diagnoses. Many genus-defining features consist of a combination of non-unique characters, which may not hold significant taxonomic importance. Consequently, most genera within the family are non-monophyletic according to phylogenetic findings. The absence of molecular data complicates the identification of taxonomically important characteristics that may have been previously overlooked. While the pore complex and the lateral pore-like structure have been suggested as potentially important traits, these insights are lacking in most recorded species, along with molecular data to confirm their significance in topology. Given the considerable amount of work required from the ground up, this study provides both morphological information (including taxonomic description, morphometric measurements, tabular key comparing key features to all valid congeners, illustration, and microscope photographs) and molecular data (partial sequences of three molecular regions, K2P distance comparison, and phylogenetic trees) for the two species discovered in Korea. The study also offers insights on potentially significant traits, such as the pore complex and other pore structures. The Korean specimen of Acanthonchus (Seuratiella) tridentatus resembles the original description regarding aspects such as the number and type of precloacal supplements, as well as the shape of the spicules and gubernaculum. However, variations are observed in the following characteristics: body ratio, nerve ring location, pharynx length, and the presence or absence of the oscelli. Our partial molecular sequences of the specimens also match identically with a single existing entry on NCBI identified as A. (S.) tridentatus. The new species, Paracanthonchus spongius sp. nov., is most similar to P. kamui in terms of the general shape of the body and gubernaculum but can be distinguished by differences in the number of precloacal supplements, amphid position, and gubernaculum ratio. The phylogenetic tree constructed based on the 28S rRNA region shows both species grouped within the monophyletic clade of Cyatholaimidae with high bootstrap support. However, achieving generic resolution of these species will require more molecular sequences of congeners to accumulate in the future.

A potential feeding regulation strategy during aestivation: Relaxation of intestine mediated by pedal peptide/orcokinin-type neuropeptides in sea cucumber Apostichopus japonicus

Aestivation is an important survival strategy that is used by a wide variety of organisms to cope with high environmental temperatures and/or arid conditions. Summer aestivation also occurs among marine animals living in shallow inshore waters. Sea cucumbers, Apostichopus japonicus, are an economically important species that are farmed extensively in shallow in-shore waters across Asia. In recent years, this species has also been developed as an important model for studying temperature-induced aestivation in the marine environment. Over about 100 days of summer aestivation A. japonicus stops feeding, experiences severe degeneration of the intestine and substantial body mass reduction, which seriously impacts production efficiency of sea cucumbers in aquaculture. Our previous studies of A. japonicus applied LC-MS/MS to reveal changes in neuropeptide expression during aestivation and identified pedal peptide/orcokinin (PP/OK)-type neuropeptides, an evolutionarily ancient regulator of muscle relaxation/contraction, as significantly up-regulated in the circumoral nerve ring (CNR) during A. japonicus aestivation. Based on this, we proposed that PP/OK-type neuropeptides are potentially key to regulate feeding and intestinal integrity during aestivation by regulating the mechanical behavior of intestine. The present study investigated PP/OK-type neuropeptides in A. japonicus tissues via histological, functional and ecological analyses. A widespread expression pattern, especially in the CNR, radial nerve cord (RNC) and intestine was revealed using real-time quantitative PCR and immunohistochemistry. Our findings show a key role for the expression of the neuropeptide, A. japonicus pedal peptide-type precursor 2 (AjPPLNP2), during the early stage of aestivation that increased significantly in the CNR and intestine as compared with the non-aestivating condition. Furthermore, in vitro pharmacological tests showed that three PP/OK-type neuropeptides confirmed by MS displayed relaxing effects on intestine, suggesting that PP/OK-type neuropeptides have a key involvement in A. japonicus aestivation by regulating relaxation of the intestine that halts normal peristalsis and inhibits feeding. In conclusion, our results suggest a mechanism for feeding inhibition controlled by neuropeptides and provide a potential regulatory strategy for counteracting intestine atrophy and body mass reduction in sea cucumber aquaculture by controlling the action of neuropeptides.

A Putative Role of Vasopressin/Oxytocin-Type Neuropeptide in Osmoregulation and Feeding Inhibition of Apostichopus japonicus.

Vasopressin/oxytocin (VP/OT)-type neuropeptide is an ancient neurophysin-associated neuropeptide and has been intensively studied to be involved in multiple physiological processes in protostomian and deuterostome vertebrates. However, little is known about the functions of VP/OT-type neuropeptide in deuterostome invertebrates especially in echinoderms. Here, we firstly report VP/OT-type neuropeptide signaling in an important economic species, Apostichopus japonicus, which is widely cultured in Asia, with high nutritional and medicinal values. Molecular characterization analysis of holotocin and its precursor revealed the highly conserved features of VP/OT family. The candidate receptor for holotocin (AjHOR) was confirmed to be able to activate the signaling via cAMP-PKA and possible Ca2+-PKC pathway, and further activated the downstream ERK1/2 cascade. Holotocin precursor expression profile showed that they were mainly concentrated in circumoral nerve ring. Furthermore, in vitro pharmacological experiments demonstrated that holotocin caused contractile responses in preparations from A. japonicus. And in vivo functional studies indicated that short-term injection of holotocin resulted in body bloat and long-term injection resulted in reduced body mass, suggesting potential roles of holotocin in osmoregulation and feeding co-inhibition with holotocin-CCK. Our findings provided a comprehensive description of AjHOR-holotocin signaling, revealed ancient roles of holotocin in osmoregulation and feeding inhibition by controlling muscle contractions.

Distribution of large lungworms (Nematoda: Dictyocaulidae) in free-roaming populations of red deer Cervus elaphus (L.) with the description of Dictyocaulus skrjabini n. sp.

Lungworms of the genus Dictyocaulus are causative agents of parasitic bronchitis in domestic and wild ungulates. This study investigates the distribution, morphology and genetic diversity of D. cervi and a new lungworm species, Dictyocaulus skrjabini n. sp. infecting red deer Cervus elaphus, fallow deer Dama dama and moose Alces alces in Poland and Sweden. The study was conducted on 167 red deer from Poland and on the DNA of lungworms derived from 7 fallow deer, 4 red deer and 2 moose collected in Sweden. The prevalence of D. cervi and D. skrjabini n. sp. in dissected red deer in Poland was 31.1% and 7.2%, respectively. Moreover, D. skrjabini n. sp. was confirmed molecularly in 7 isolates of fallow deer lungworms and 1 isolate of red deer lungworms from Sweden. Dictyocaulus skrjabini n. sp. was established based on combination of their distinct molecular and morphological features; these included the length of cephalic vesicle, buccal capsule (BC), buccal capsule wall (BCW), distance from anterior extremity to the nerve ring, the width of head, oesophagus, cephalic vesicle, BC and BCW, as well as the dimensions of reproductive organs of male and female. Additionally, molecular analyses revealed 0.9% nucleotide sequence divergence for 1,605 bp SSU rDNA, and 16.5–17.3% nucleotide sequence divergence for 642 bp mitochondrial cytB between D. skrjabini n. sp. and D. cervi, respectively, and 18.7–19% between D. skrjabini n. sp. and D. eckerti, which translates into 18.2–18.7% amino acid sequence divergence between D. skrjabini n. sp. and both lungworms.