Search

Organisms have adapted to dynamic river flows as part of the natural flow regime. However, climate change and humans' use of fresh water are associated with decreases in the quality and quantity of surface waters. In addition, river impoundments and water withdrawals for human use regulate and dampen the dynamism of flow in many rivers. These changes to the natural flow regime can impact the spawning migrations of lampreys (Petromyzontiformes). Here, our goal is to review the ecology of lamprey spawning migrations associated with river flows, with considerations for controlling invasive sea lamprey (Petromyzon marinus) and conserving native lampreys (including native, anadromous sea lamprey). We identify five common themes: (1) natural flow regimes provide a competitive edge to native fishes over non‐native fishes; (2) high flows (up to a threshold) attract adult lamprey and large streams attract large numbers of lamprey; (3) larval lamprey pheromones attract adult lampreys; (4) behavioral responses by adult lamprey to flow (including localized hydraulics) can inform dam passage and trapping methods; and (5) changes to rivers induced by climate change have been implicated in changing the phenology of run timing and spawning location. Controlling invasive sea lamprey and conserving native lampreys can be done with pheromones and flow management. Pheromones may be of more use under focused management efforts to control invasive sea lamprey, whereas flow management can provide a foundation for conservation of native lampreys. [ABSTRACT FROM AUTHOR]

Although olfaction is well known to guide animal behavior, the neural circuits underlying the motor responses elicited by olfactory inputs are poorly understood. In the sea lamprey, anatomical evidence shows that olfactory inputs project to the posterior tuberculum (PT), a structure containing dopaminergic (DA) neurons homologous to the mammalian ventral tegmental area and the substantia nigra pars compacta. Olfactory inputs travel directly from the medial olfactory bulb (medOB) or indirectly through the main olfactory bulb and the lateral pallium (LPal). Here, we characterized the transmission of olfactory inputs to the PT in the sea lamprey, Petromyzon marinus. Abundant projections from the medOB were observed close to DA neurons of the PT. Moreover, electrophysiological experiments revealed that PT neurons are activated by both the medOB and LPal, and calcium imaging indicated that the olfactory signal is then relayed to the mesencephalic locomotor region to initiate locomotion. In semi-intact preparations, stimulation of the medOB and LPal induced locomotion that was tightly associated with neural activity in the PT. Moreover, PT neurons were active throughout spontaneously occurring locomotor bouts. Altogether, our observations suggest that the medOB and LPal convey olfactory inputs to DA neurons of the PT, which in turn activate the brainstem motor command system to elicit locomotion. [ABSTRACT FROM AUTHOR]

3-phosphoinositide-dependent protein kinase-1 (PDK-1) is a key kinase regulating the activity of the PI3K/AKT pathway and a major regulator of the AGC protein kinase family. It is essential in the physiological activities of cells, embryonic development, individual development and immune response. In this study, we have identified for the first time an analogue of PDK-1 in the most primitive vertebrate, lamprey, and named it PDK-1-like. The protein sequence similarity of lamprey PDK-1-like to human, mouse, chicken, African xenopus and zebrafish PDK-1 were 64.4 %, 64.5 %, 65.0 %, 61.3 % and 63.2 %, respectively. The phylogenetic tree showed that PDK-1-like of lamprey were located at the base of the vertebrate branch, in line with the trend of biological evolution. Meanwhile, homology analysis showed that PDK-1 proteins across species shared a conserved kinase structural domain and a Pleckstrin Homology (PH) domain. Genomic synteny analysis revealed that the large-scale duplication blocks were not found in lamprey genome and neighbor genes of lamprey PDK-1-like presented dramatic differences compared with jawed vertebrates. More importantly, qPCR analysis showed that PDK-1-like was widely expressed in lamprey. Its mRNA expression levels varied in response to different pathogenic stimuli, and its expression was generally up-regulated under Polyinosinic-Polycytidylic acid (Poly(I:C)) stimulation. Pearson's correlation analysis showed that PDK-1-like was involved in co-expressed with MyD88-independent TLR-3 pathway during the immune response of lamprey, instead of MyD88-dependent TLR-3 pathway. In summary, our composite results offer valuable clues to the origin and evolution of PDK-1, and imply that PDK-1 s are among the most ancestral immune regulators in vertebrates. [ABSTRACT FROM AUTHOR]

The metabotropic glutamate receptor (mGluR, GRM) family is involved in multiple signaling pathways and regulates neurotransmitter release. However, the evolutionary history, distribution, and function of the mGluRs family in lampreys have not been determined. Therefore, we identified the mGluRs gene family in the genome of Lethenteron reissneri, which has been conserved throughout vertebrate evolution. We confirmed that Lr-GRM3, Lr-GRM5, and Lr-GRM7 encode three types of mGluRs in lamprey. Additionally, we investigated the distribution of Lr-GRM3 within this species by qPCR and Western blotting. Furthermore, we conducted RNA sequencing to investigate the molecular function of Lr-GRM3 in lamprey. Our gene expression profile revealed that, similar to that in jawed vertebrates, Lr-GRM3 participates in multiple signal transduction pathways and influences synaptic excitability in lampreys. Moreover, it also affects intestinal motility and the inflammatory response in lampreys. This study not only enhances the understanding of mGluRs' gene evolution but also highlights the conservation of GRM3's role in signal transduction while expanding our knowledge of its functions specifically within lampreys. In summary, our experimental findings provide valuable insights for studying both the evolution and functionality of the mGluRs family. [ABSTRACT FROM AUTHOR]

The lamprey genus Geotria Gray, 1851 currently includes only two species: G. australis and G. macrostoma. However, taxonomic relationships within the genus have traditionally been ambiguous and difficult to establish due to the extreme changes in morphology, dentition, and coloration that lampreys undergo during their life cycles, particularly during upstream migration and sexual maturation. Consequently, several lamprey specimens held in museum collections have remained unidentified, especially those from Argentina. In this study, a series of morphometric characters were subjected to discriminant function analysis (DFA) to identify the lamprey species collected during 1867–2004 from the de la Plata River and Patagonia. These specimens are housed at the Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" in Buenos Aires, the Museo de Historia Natural de Montevideo, and the Naturhistoriska riksmuseet in Stockholm. Based on the proportions of the length of the oral disc, prebranchial, and pre‐caudal body regions, and the depth of the trunk, DFA provided conclusive evidence that the specimens corresponded to the recently revalidated G. macrostoma (Burmeister, 1868), which was originally incorrectly named as Petromyzon macrostomus Burmeister, 1868, Exomegas macrostomus (Berg, 1899), Geotria chilensis (Berg, 1895), and Geotria macrostoma f. gallegensis Smitt, 1901, as well as other nontype museum individuals of uncertain taxonomic status. The identifications of these long‐preserved museum specimens provided key information on the historical geographic range of Argentinian lampreys and suggest that the disappearance of the species reported from northern localities (the Pampean Region) can be attributed to the degradation of their critical habitats, primarily caused by anthropogenic impact and climate change. [ABSTRACT FROM AUTHOR]

AF4/FMR2 family member (AFF) proteins are a group of transcriptional regulators that can regulate gene transcription and play an important role in cellular physiological processes such as proliferation and differentiation. The transcriptome data of the lamprey spinal cord injury were analyzed in previous research. We then identified a hub gene, Lr-AFF3, from this dataset. Phylogenetic tree analysis determined the evolutionary relationships of the AFF gene family across different species. In addition, analysis of motifs, domains, and 3D structures further confirmed the conservatism of the AFF gene family. In particular, the gene structure of the AFF3 gene was not conserved, possibly because of intron insertion. It was also found that the neighboring genes of the Lr-AFF3 gene had a higher diversity than that in jawed vertebrates through synteny analysis. The results of the MTT and EdU experiments showed that the C-terminal homology domain (CHD) and N-terminal homology domain (NHD) of Lr-AFF3 promoted cell proliferation. In summary, our research will not only provide new insights into the origin and evolution of the AFF gene family in different species, but also provide new clues for the functions of Lr_AFF3. [ABSTRACT FROM AUTHOR]

The Na (+)-taurocholate cotransporting polypeptide (NTCP) is a member of the solute carrier family 10 (SLC10), which consists of 7 members (SLC10a1-SLC10a7). NTCP is a transporter localized to the basolateral membrane of hepatocytes and is primarily responsible for the absorption of bile acids. Although mammalian NTCP has been extensively studied, little is known about the lamprey NTCP (L-NTCP). Here we show that L-NTCP follows the biological evolutionary history of vertebrates, with conserved domain, motif, and similar tertiary structure to higher vertebrates. L-NTCP is localized to the cell surface of lamprey primary hepatocytes by immunofluorescence analysis. HepG2 cells overexpressing L-NTCP also showed the distribution of L-NTCP on the cell surface. The expression profile of L-NTCP showed that the expression of NTCP is highest in lamprey liver tissue. L-NTCP also has the ability to transport bile acids, consistent with its higher vertebrate orthologs. Finally, using a farnesoid X receptor (FXR) antagonist, RT-qPCR and flow cytometry results showed that L-NTCP is negatively regulated by the nuclear receptor FXR. This study is important for understanding the adaptive mechanisms of bile acid metabolism after lamprey biliary atresia based on understanding the origin, evolution, expression profile, biological function, and expression regulation of L-NTCP. [ABSTRACT FROM AUTHOR]

Jamoytius kerwoodi, is a primitive, eel-like jawless vertebrate found uniquely in an Early Silurian (Llandovery epoch; 444–433 Ma) horizon near Lesmahagow, Scotland. This species is a rare component of a low-diversity dominantly nektonic detritus-feeding and herbivorous fauna living over an anoxic bottom and is found at the transition from a marine-influenced, probably brackish-water, deep-water basin to a shallower-water, less saline and likely freshwater basin. In the absence of true teeth, Jamoytius was probably a detritivore or herbivore feeding on Dictyocaris. Jamoytius may have a common ancestor with living lampreys, especially as their ectoparasitic mode of life might have evolved from ancestral detritivores or herbivores. [ABSTRACT FROM AUTHOR]

During early development, sea lamprey embryos undergo programmatic elimination of DNA from somatic progenitor cells in a process termed programmed genome rearrangement (PGR). Eliminated DNA eventually becomes condensed into micronuclei, which are then physically degraded and permanently lost from the cell. Previous studies indicated that many of the genes eliminated during PGR have mammalian homologs that are bound by polycomb repressive complex (PRC) in embryonic stem cells. To test whether PRC components play a role in the faithful elimination of germline‐specific sequences, we used a combination of CRISPR/Cas9 and lightsheet microscopy to investigate the impact of gene knockouts on early development and the progression through stages of DNA elimination. Analysis of knockout embryos for the core PRC2 subunits EZH, SUZ12, and EED show that disruption of all three genes results in an increase in micronucleus number, altered distribution of micronuclei within embryos, and an increase in micronucleus volume in mutant embryos. While the upstream events of DNA elimination are not strongly impacted by loss of PRC2 components, this study suggests that PRC2 plays a role in the later stages of elimination related to micronucleus condensation and degradation. These findings also suggest that other genes/epigenetic pathways may work in parallel during DNA elimination to mediate chromatin structure, accessibility, and the ultimate loss of germline‐specific DNA. Research Highlights: Cas9 was used efficiently mutate core PRC2 genes EZH, SUZ12, and EED.Whole embryo imaging revealed impacts on micronucleus distribution and compaction during later stages of DNA loss.Initial targeting of DNA for elimination is likely upstream of PRC2. [ABSTRACT FROM AUTHOR]

California (USA) is home to a diverse lamprey fauna that historically occupied streams throughout the state and into Baja California (México). Recent range fluctuations by anadromous Pacific Lamprey, Entosphenus tridentatus, in its southern range have caused concern with regard to anticipated climatic changes and warming of stream habitats. Examination of temperature tolerances in lampreys has generally been conducted in the laboratory. Here we associate modeled mean August water temperatures (AugTw) of stream reaches currently occupied by lampreys in California for periods 2002–2011, 2040, 2080, and + 3 °C scenarios. The nine lamprey taxa in California occupy a considerable range in temperatures, reflecting their broad elevational and latitudinal ranges, with 2002–2011 AugTw of 7.9–25.9 °C. This includes the current distribution of the anadromous Pacific Lamprey (10.3–25.9 °C). Under a projected relatively extreme + 3 °C increase, only eight streams state-wide are projected to have reaches exceeding AugTw of 28.0 °C, accounting for 2.6% of currently occupied habitat. Actual 2021 August water temperatures surveyed at selected sites with high modeled 2002–2011 temperatures and currently occupied by Pacific Lamprey ranged from 18.5 to 32.6 °C (mean, 27.9 °C). Projected temperature increases suggest that future conditions may be within the range currently encountered and tolerated by Pacific Lamprey. Empirical observations of multiple-year classes of ammocoetes (lamprey larvae) in warmer stream reaches suggest that lampreys are successfully rearing in streams that reach temperatures close to the upper lethal limits suggested by laboratory studies. How they do this is not clear, but may involve both physiological tolerances and behavioral responses to high-temperature conditions. Our results also suggest that rising stream temperatures are not likely to restrict the distribution of western lampreys in the foreseeable future, and therefore, conservation strategies should focus on other issues, such as restoring access to historical habitats, avoiding stream desiccation, and restoring natural flow regimes. [ABSTRACT FROM AUTHOR]

Background: Although vertebrae are the defining character of vertebrates, they are found only in rudimentary form in extant agnathans. In addition, the vertebrae of agnathans possess several unique features, such as elastin‐like molecules as the main matrix component and late (post‐metamorphosis) differentiation of lamprey vertebrae. In this study, by tracing the developmental process of vertebrae in lamprey, we examined the homology of vertebrae between lampreys and gnathostomes. Results: We found that the lamprey somite is first subdivided mediolaterally, with myotome cells differentiating medially and non‐myotome cells emerging laterally. Subsequently, collagen‐positive non‐myotome cells surround the myotome. This pattern of somitogenesis is rather similar to that in amphioxi and sheds doubt on the presence of a sclerotome, in terms of mesenchyme cells induced by a signal from the notochord, in lamprey. Further tracing of non‐myotome cell development revealed that fin cartilage develops in ammocoete larvae approximately 35 mm in body length. The development of the fin cartilage occurs much earlier than that of the vertebra whose development proceeds during metamorphosis. Conclusion: We propose that the homology of vertebrae between agnathans and gnathostomes should be discussed carefully, because the developmental process of the lamprey vertebra is different from that of gnathostomes. Key Findings: Lamprey somite is first subdivided medio‐laterally, and myotome emerge medially.Subsequently, collagen‐positive non‐myotome cells surround the myotome.Fin cartilage develops in ammocoete larvae well before metamorphosis.Vertebra develop in adaxial region during metamorphosis. [ABSTRACT FROM AUTHOR]

Climate change is occurring worldwide, affecting everyday life and cultural traditions cherished for centuries. Intangible cultural heritage is vulnerable to climate change, as it depends on local resources and on the skills and knowledge of living in a certain environment. By studying the example of the lamprey fishing tradition in the village of Carnikava, Latvia, the article explores connections between climate change and intangible cultural heritage from the point of view of tradition-bearers, local community, local government, scientists and state institutions. This example shows that, when climate change equally affects both biological species and centuries-old fishing traditions specialised in harvesting these species, sustainable solutions are necessary to preserve both. [ABSTRACT FROM AUTHOR]

It is difficult to perform multiplication with digital devices and required to the more practical implementation methods. Thus, a well-known simpler transfer function adaptation to a swimming pattern generator is suggested for the digital implementation easiness in here. However, the direct adaptation of this function to this neural circuit is insufficient, so a control parameter is included in the laterally inhibitor neurons. Its fittest value is determined by a bifurcation diagram for getting a neural circuit that produces rhythmic patterns. Then, a four-segmented neural swimming pattern generator is constructed by using this simpler function and the anti-phase firings of neuron groups on the opposite sides is observed by the numerical simulations. Additionally, it is aimed to obtain an adjustable time delay between the neural segments, so the ‘reciprocal inhibition’ synaptic connections are adapted to this four-segmented structure. The effect of the reciprocal inhibition on time delays is observed by the standard deviation and numerical simulations. The final aim is to get the electrical signals with the digital device-based implementation for emulating the swimming rhythmic pattern generator of a lamprey and a Field Programmable Gate Array-based realization is carried out by using the simpler transfer function. To see the achievement of this implementation, the anti-phase firings of neuron groups on the opposite sides and getting an adjustable time delay between neural segments are verified by the electrical signals. Moreover, the swimming pattern generator of a lamprey is realized with FPGA without using any multiplier blocks thanks to the simplification process.

Abstract The evolutionary origin of the jaw remains one of the most enigmatic events in vertebrate evolution. The trigeminal nerve is a key component for understanding jaw evolution, as it plays a crucial role as a sensorimotor interface for the effective manipulation of the jaw. This nerve is also found in the lamprey, an extant jawless vertebrate. The trigeminal nerve has three major branches in both the lamprey and jawed vertebrates. Although each of these branches was classically thought to be homologous between these two taxa, this homology is now in doubt. In the present study, we compared expression patterns of Hmx, a candidate genetic marker of the mandibular nerve (rV3, the third branch of the trigeminal nerve in jawed vertebrates), and the distribution of neuronal somata of trigeminal nerve branches in the trigeminal ganglion in lamprey and shark. We first confirmed the conserved expression pattern of Hmx1 in the shark rV3 neuronal somata, which are distributed in the caudal part of the trigeminal ganglion. By contrast, lamprey Hmx genes showed peculiar expression patterns, with expression in the ventrocaudal part of the trigeminal ganglion similar to Hmx1 expression in jawed vertebrates, which labeled the neuronal somata of the second branch. Based on these results, we propose two alternative hypotheses regarding the homology of the trigeminal nerve branches, providing new insights into the evolutionary origin of the vertebrate jaw.

Lamprey homologues of the classic embryonic inducer Noggin are similar in expression pattern and functional properties to Noggin homologues of jawed vertebrates. All noggin genes of vertebrates apparently originated from a single ancestral gene as a result of genome duplications. nogginA, nogginB and nogginC of lampreys, like noggin1 and noggin2 of gnathostomes, demonstrate the ability to induce complete secondary axes with forebrain and eye structures when overexpressed in Xenopus laevis embryos. According to current views, this finding indicates the ability of lamprey Noggin proteins to suppress the activity of the BMP, Nodal/Activin and Wnt/beta-catenin signaling pathways, as shown for Noggin proteins of gnathostomes. In this work, by analogy with experiments in Xenopus embryos, we attempted to induce secondary axes in the European river lamprey Lampetra fluviatilis by injecting noggin mRNAs into lamprey eggs in vivo. Surprisingly, unlike what occurs in amphibians, secondary axis induction in the lampreys either by noggin mRNAs or by chordin and cerberus mRNAs, the inductive properties of which have been described, was not observed. Only wnt8a mRNA demonstrated the ability to induce secondary axes in the lampreys. Such results may indicate that the mechanism of axial specification in lampreys, which represent jawless vertebrates, may differ in detail from that in the jawed clade. [ABSTRACT FROM AUTHOR]

The mammalian testis and ovary possess special immunocompetence, which is central to provide protection against pathogens. However, the innate immune responses to immune challenges in lamprey gonads are poorly understood. In this study, we extracted RNA from testis and ovary tissues of lampreys at 0 hour, 8 hours and 17 days after lipopolysaccharides (LPS) stimulation and performed transcriptome sequencing. While the transcriptome profiles of the two tissues were different for the most part, genes LIP, LECT2, LAL2, GRN, ITLN, and C1q were found to be the most significantly up-regulated genes in both. Quantitative Real-time PCR (qRT-PCR) analysis confirmed that these genes were upregulated after stimulation. Furthermore, immunohistochemical staining showed that these genes in lamprey gonads are expressed in high quantities and have a specific distribution. Taken together, our results suggest that these genes could play an essential role in response of the gonads to LPS induction. This research establishes a basis for investigating the immune mechanism of vertebrate gonads and presents a fresh concept for gaining insight into the evolutionary development of jawless vertebrates. [ABSTRACT FROM AUTHOR]

In lampreys, respiration consists of a fast and a slow rhythm. This study was aimed at characterizing both anatomically and physiologically the brainstem regions involved in generating the two rhythms. The fast rhythm generator has been located by us and others in the rostral hindbrain, rostro-lateral to the trigeminal motor nucleus. More recently, this was challenged by researchers reporting that the fast rhythm generator was located more rostrally and dorsomedially, in a region corresponding to the mesencephalic locomotor region. These contradictory observations made us re-examine the location of the fast rhythm generator using anatomical lesions and physiological recordings. We now confirm that the fast respiratory rhythm generator is in the rostrolateral hindbrain as originally described. The slow rhythm generator has received less attention. Previous studies suggested that it was composed of bilateral, interconnected rhythm generating regions located in the caudal hindbrain, with ascending projections to the fast rhythm generator. We used anatomical and physiological approaches to locate neurons that could be part of this slow rhythm generator. Combinations of unilateral injections of anatomical tracers, one in the fast rhythm generator area and another in the lateral tegmentum of the caudal hindbrain, were performed to label candidate neurons on the non-injected side of the lateral tegmentum. We found a population of neurons extending from the facial to the caudal vagal motor nuclei, with no clear clustering in the cell distribution. We examined the effects of stimulating different portions of the labeled population on the respiratory activity. The rostro-caudal extent of the population was arbitrarily divided in three portions that were each stimulated electrically or chemically. Stimulation of either of the three sites triggered bursts of discharge characteristic of the slow rhythm, whereas inactivating any of them stopped the slow rhythm. Substance P injected locally in the lateral tegmentum accelerated the slow respiratory rhythm in a caudal hindbrain preparation. Our results show that the fast respiratory rhythm generator consists mostly of a population of neurons rostro-lateral to the trigeminal motor nucleus, whereas the slow rhythm generator is distributed in the lateral tegmentum of the caudal hindbrain. [ABSTRACT FROM AUTHOR]

A new fossil species of lamprey, Caeruleum gracilis sp. nov. is described from the Early Cretaceous Jiufotang Formation in China Hebei province, North China. Caeruleum gracilis sp. nov. is characterised by a slender body shape and a dorsal fin originating above the second branchial pouch. Given the intricate life history of lampreys, their presence in saltwater and freshwater, and their convoluted and ambiguous evolutionary trajectory, it is imperative to investigate whether the living environment of fossil lamprey species encompassed varying levels of salinity. This inquiry will facilitate our understanding and tracing of the earliest adaptations of lampreys to freshwater and saltwater environments. Based on salinity analysis, the environment of the Jiufotang Formation may be attributed to brackish conditions. Therefore, the lampreys Caeruleum gracilis sp. nov. and Caeruleum miraculum from the Jiufotang Formation may represent the one of earliest lampreys records that acquired adaptations to freshwater environments. [ABSTRACT FROM AUTHOR]

Foxg1 is a key regulator of the early development of the vertebrate forebrain and sensory organs. In this study, we describe for the first time three foxg1 paralogues in lamprey, representative of one of two basally diverged lineages of vertebrates—the agnathans. We also first describe three foxg1 genes in sterlet—representative of one of the evolutionarily ancient clades of gnathostomes. According to the analysis of local genomic synteny, three foxg1 genes of agnathans and gnathostomes have a common origin as a result of two rounds of genomic duplications in the early evolution of vertebrates. At the same time, it is difficult to reliably establish pairwise orthology between foxg1 genes of agnathans and gnathostomes based on the analysis of phylogeny and local genomic synteny, as well as our studies of the spatiotemporal expression of foxg1 genes in the river lamprey Lampetra fluviatilis and the sterlet Acipenser ruthenus. Thus, the appearance of three foxg1 paralogues in agnathans and gnathostomes could have occurred either as a result of two rounds of duplication of the vertebrate common ancestor genome (2R hypothesis) or as a result of the first common round followed by subsequent independent polyploidizations in two evolutionary lineages (1R hypothesis). [ABSTRACT FROM AUTHOR]

Lampreys were considered a delicacy among most royal families and the nobility in medieval Britain. The tradition was for the people to present the monarch with a lamprey pie once a year. King Henry I (1068–1135) of England was known for his lust for eating lampreys and is reported to have died from a “surfeit of lampreys,” as the chronicle said. The information concerning this event is scarce, confined to only two sources, the chronicle of Henry of Huntingdon and the history of Roger of Wendover. Both write about Henry’s death, but only the former mentions its cause, albeit without many details. It remains a mystery then whether the king died from gluttony, or maybe from food poisoning or some other reason. The author of the article describes the circumstances of Henry’s death and presents the arguments to justify the probable cause of it. Medieval dietetics has been used as a springboard to writing about the importance of fish in the diet despite its unfavorable opinion in the light of the theory of humors. Fish were believed to predominate in cold and moist humors, which, in terms of humoral theory, is particularly dangerous to anyone in cold and moist seasons. [ABSTRACT FROM AUTHOR]

The evolutionary origin of the jaw remains one of the most enigmatic events in vertebrate evolution. The trigeminal nerve is a key component for understanding jaw evolution, as it plays a crucial role as a sensorimotor interface for the effective manipulation of the jaw. This nerve is also found in the lamprey, an extant jawless vertebrate. The trigeminal nerve has three major branches in both the lamprey and jawed vertebrates. Although each of these branches was classically thought to be homologous between these two taxa, this homology is now in doubt. In the present study, we compared expression patterns of Hmx, a candidate genetic marker of the mandibular nerve (rV3, the third branch of the trigeminal nerve in jawed vertebrates), and the distribution of neuronal somata of trigeminal nerve branches in the trigeminal ganglion in lamprey and shark. We first confirmed the conserved expression pattern of Hmx1 in the shark rV3 neuronal somata, which are distributed in the caudal part of the trigeminal ganglion. By contrast, lamprey Hmx genes showed peculiar expression patterns, with expression in the ventrocaudal part of the trigeminal ganglion similar to Hmx1 expression in jawed vertebrates, which labeled the neuronal somata of the second branch. Based on these results, we propose two alternative hypotheses regarding the homology of the trigeminal nerve branches, providing new insights into the evolutionary origin of the vertebrate jaw. [ABSTRACT FROM AUTHOR]

Objective: Protecting biodiversity is important for preserving ecosystem functions and services, and understanding the diversity present in a system is necessary for effective conservation. Lampreys display extensive diversity in morphology and life history strategy. The extent of this diversity and the underlying genetic patterns have not yet been fully characterized. Uncertainty about species boundaries and operational taxonomic units hinders lamprey management and conservation. Limited data have been collected on California lampreys (Lampetra spp. and Entosphenus spp.), but evidence suggests widespread population decline across the west coast of North America. Study objectives were to identify which nominal species are present at study sites across northern and central California, determine whether current taxonomic classifications accurately and sufficiently describe lamprey diversity in California, and characterize the biogeographic distribution of genetically distinct lamprey lineages across the study area. Methods: To achieve these objectives, this study utilized DNA barcoding, phylogenetic analysis, and species delimitation analysis. Lamprey individuals (N = 87) from 19 sites in the Sacramento–San Joaquin River basin, San Francisco Bay, and Klamath River basin were sequenced for the mitochondrial cytochrome b (cyt b) gene, and the data were combined with publicly available lamprey cyt b sequences for analysis. Result: Results showed relatively deep phylogenetic divergence between Lampetra and Entosphenus. Distinct and genetically divergent lineages were observed within Lampetra, while distinct but genetically similar lineages were observed within Entosphenus. This study revealed novel Lampetra lineages in the Napa River and Alameda Creek, and results suggest that the biogeographic distribution of lamprey diversity may follow patterns observed in other native fishes. Species delimitation results indicated that at least seven separate candidate species of Lampetra can be found in California, suggesting that California holds more species‐level diversity than the expected three nominal Lampetra species known to occur in the state. Conclusion: These results highlight the underestimated diversity of lampreys in California and the need for further assessment of taxonomic classifications and operational taxonomic unit designations of California lampreys. Impact statementLampreys are ecologically and culturally significant. Populations are thought to be declining across the west coast of North America, but a lack of research impedes monitoring and conservation of lampreys in California. This study investigated lampreys in California using DNA sequences and found more diversity than expected. By determining how many genetically different types of lampreys are present and where these various lampreys are found across the study area, this research paves the way for conservation and protection of lampreys and the numerous benefits they contribute. [ABSTRACT FROM AUTHOR]

Objective: Dewatering of fine sediments in rivers and streams can kill many thousands of larval lampreys (order Petromyzontiformes) that are burrowed in these habitats. The larval life stage for lampreys lasts 3–10 years, and because larvae often aggregate in large numbers, negative impacts from dewatering could potentially deplete local populations and affect multiple year‐classes. Larval lampreys have not traditionally been considered during instream projects, but recent efforts to increase awareness of lamprey habitats have resulted in guidance on dewatering approaches to limit impacts to lampreys. Salvage efforts to rescue and relocate lampreys aim to mitigate losses, but a lack of understanding of lamprey responses limits the optimization of dewatering and salvage procedures. Methods: We summarize the state of the science for nine factors that influence larval lamprey (Entosphenus and Lampetra spp.) responses to dewatering, including burrowing depth, the prevalence and timing of emergence, movements, survival, shoreline slope, dewatering rate, light, and lamprey size. Result: Research suggests that (1) shoreline slope influences movement capability, (2) hot and sunny conditions increase the risk of mortality, (3) salvage activities cause minimal direct mortality, and (4) smaller larvae are especially vulnerable to negative impacts from dewatering because they are more likely to emerge and are less capable of movement. Critical uncertainties associated with dewatering include cues that drive emergence, the influence of sediment composition and stratigraphy, vertical distribution of larvae in natural settings, use of the hyporheic zone, the scale of predation losses, and the effectiveness and impacts of salvage activities. Conclusion: Balancing investments in salvage operations and lamprey exclusion efforts (e.g., screening) and developing field survey approaches to evaluate lamprey use of the hyporheic zone are identified management implications and research needs. Addressing the critical uncertainties discussed here and providing updated, science‐based guidance on dewatering and salvage practices are suggested management actions to support lamprey conservation. Impact statementLarval lampreys live burrowed in fine sediments and are often not considered during instream projects that dewater these habitats. This paper synthesizes what is known about lamprey responses to dewatering to provide updated, science‐based guidance on dewatering approaches to minimize negative impacts to lamprey and support conservation efforts. [ABSTRACT FROM AUTHOR]

Foxg1 is a key regulator of the early development of the vertebrate forebrain and sensory organs. In this study, we describe for the first time three foxg1 paralogues in lamprey, representative of one of two basally diverged lineages of vertebrates—the agnathans. We also first describe three foxg1 genes in sterlet—representative of one of the evolutionarily ancient clades of gnathostomes. According to the analysis of local genomic synteny, three foxg1 genes of agnathans and gnathostomes have a common origin as a result of two rounds of genomic duplications in the early evolution of vertebrates. At the same time, it is difficult to reliably establish pairwise orthology between foxg1 genes of agnathans and gnathostomes based on the analysis of phylogeny and local genomic synteny, as well as our studies of the spatiotemporal expression of foxg1 genes in the river lamprey Lampetra fluviatilis and the sterlet Acipenser ruthenus. Thus, the appearance of three foxg1 paralogues in agnathans and gnathostomes could have occurred either as a result of two rounds of duplication of the vertebrate common ancestor genome (2R hypothesis) or as a result of the first common round followed by subsequent independent polyploidizations in two evolutionary lineages (1R hypothesis).

The distribution, relative abundance, and rearing habitat of larvae of the Patagonian lamprey (Geotria macrostoma) were investigated in the Santa Cruz River basin, Patagonia, Argentina, using electrofishing and bile acid (petromyzonol sulfate) concentration. Both techniques revealed that larvae are widely distributed along the basin, aggregated at habitats of fine substrates and slow waters. Both, density and pheromone concentrations were consistent in detecting the presence of larvae and for gauging their abundance. Throughout the basin, length distribution of larvae ranged from 10 to 122 mm; larvae of the smaller length classes were present at both, upper sections and at the lower course of the main stem river, suggesting that these sites contained 0 + recruits from the previous spawning season. Currently construction of two hydroelectric dams in the main course of the Santa Cruz River will interrupt the migratory corridor of adult lamprey in search of their spawning grounds and will flood critical habitats for larvae rearing. The information generated in this study may be used as guidance for developing sampling surveys for the purpose of monitoring changes in populations trends for Patagonian lamprey in this river and other Patagonian drainages altered by human activities. [ABSTRACT FROM AUTHOR]

A subclass of Mesozoic lamprey from Chengde, Hebei, China, Caeruleum miraculum gen. et sp. nov. is described. This new species has typical characteristics of another subclass of lamprey including an eel-like slender body, no paired appendages, absent jaws, round at anterior and laterally flat at posterior, and seven gill foramina, with anterior dorsal fin, posterior dorsal fin, and caudal fin. In addition, the total length of this species is between 240 mm (Table 1)-462 mm (Figure 4), which is 16.47 times the body depth, 4.01 times the head length, and 4.24 times the caudal length. Its body size is huge and very close to modern lampreys. This article briefly compared this species with the known Mesomyzon mengae. The discovery of these new fossils provides new evidence to study the evolution of Chinese lampreys during the Mesozoic and to explore the origin of modern lampreys. [ABSTRACT FROM AUTHOR]

High-purity total RNA extraction from animal embryos is essential for transcriptome analyses. lampreys, together with hagfish, are the only extant jawless vertebrates or cyclostomes and are thus key organisms for EvoDevo studies. However, extracting uncontaminated RNA from early-stage embryos remains challenging. RNA does not bind to the silica membrane in filter-based extractions, significantly reducing yields; and ethanol/isopropanol precipitation methods lead to contaminants, bringing down the optical density (OD) 260/280 ratio. The RNA extraction protocol was modified using precentrifugation and adding salts before isopropanol precipitation. This modification significantly increased RNA yield, removed contaminants and improved RNA integrity. Egg membrane sources were suspected to cause RNA purification problems because low-quality extraction does not occur in posthatching embryos.

Abstract Background Little is known about the transformer stage of the parasitic lampreys, a brief but critical period that encompasses juvenile out-migration from rivers to lakes or oceans to begin parasitic feeding. Information about this life stage could have significant conservation implications for both imperiled and invasive lampreys. We investigated tag retention, survival, wound healing, and swim performance of newly transformed sea lamprey (Petromyzon marinus) implanted with a new micro-acoustic transmitter, the eel–lamprey acoustic transmitter (ELAT), in a controlled laboratory environment. Results The 61-day survival of our tagged subjects was 71%, within the range reported in similar studies of juvenile lampreys. However, survival was significantly lower in the tagged animals (vs control), with no effect statistically attributable to measures of animal length, mass, condition, or population of origin (Great Lakes vs. Atlantic drainage). Mortality in tagged fish was concentrated in the first four days post-surgery, suggesting injury from the surgical process. An unusually long recovery time from anesthesia may have contributed to the increased mortality. In a simple burst swim assay, tagged animals swam significantly slower (− 22.5%) than untagged animals, but were not significantly different in endurance swim tests. A composite wound healing score at day four was a significant predictor of maximum burst swim speed at day 20, and wound condition was related to animal mass, but not length, at the time of tagging. Conclusions Impairments to survival and swim performance of juvenile sea lamprey implanted with the ELAT transmitter were within currently reported ranges for telemetry studies with small, difficult to observe fishes. Our results could be improved with more refined anesthesia and surgical techniques. The ability to track migratory movements of imperiled and pest populations of parasitic lampreys will improve our ability to estimate vital rates that underlie recruitment to the adult population (growth, survival) and to investigate the environmental factors that regulate the timing and rates of movement, in wild populations.

Various proteins with antibacterial, anticoagulant, and anti-inflammatory properties have been identified in the buccal glands of jawless blood-sucking vertebrate lampreys. However, studies on endogenous peptides in the buccal gland of lampreys are limited. In this study, 4528 endogenous peptides were identified from 1224 precursor proteins using peptidomics and screened for bioactivity in the buccal glands of the lamprey, Lethenteron camtschaticum. We synthesized four candidate bioactive peptides (VSLNLPYSVVRGEQFVVQA, DIPVPEVPILE, VVQLPPVVLGTFG, and VPPPPLVLPPASVK), calculated their secondary structures, and validated their bioactivity. The results showed that the peptide VSLNLPYSVVRGEQFVVQA possessed anti-inflammatory activity, which significantly increased the expression of anti-inflammatory factors and decreased the expression of inflammatory factors in THP-1 cells. The peptide VVQLPPVVLGTFG showed antibacterial activity against some gram-positive bacteria. The peptide VSLNLPYSVVRGEQFVQA possessed good ACE inhibitory activity at low concentrations, but no dose-related correlation was observed. Our study revealed that the buccal glands of the jawless vertebrate lamprey are a source of multiple bioactive peptides, which will provide new insights into the blood-sucking mechanism of lamprey. [ABSTRACT FROM AUTHOR]

This review serves as a guide to improve multi-species fish passage. Human development along waterways in California during the last 160 years has adversely affected fish populations in many watersheds. Conflicts in water usage will only intensify with modern developments and population growth. Since most past fish-passage improvement efforts in California have focused on salmonids, I summarize the published studies and considerations that affect multi-species fish passage. To be effective, conditions in fishways need to meet the specific hydraulic requirements, as well as abilities, behavior, and size consideration for all fish species being considered. Turbulence, water depth, velocity, passage location, and design of a passage facility are essential elements to successful fish passage. Because of a lack of research on most of the native species, species-specific passage criteria are not fully defined, and it may be helpful to use data for physically similar, surrogate species found in similar habitats.

Key points A novel serum spherical lectin from lamprey was identified which have agglutination activity against bacteria dependent on calcium. The crystal structure of LSSL was determined, and adhered to both microbial and mammalian glycans with high binding capacity. The role of LSSL was associated with MASP-1 and recruited C3 deposition for pathogen elimination.

Toll-like receptors (TLRs) play an important role in innate immunity of defense against bacterial or viral pathogens. To study the biological characteristics and functions of the TLR genes, TLR14d was identified from Northeast Chinese lamprey (Lethenteron morii) and named LmTLR14d. LmTLR14d coding sequence (cds) is 3285 bp in length and encodes 1094 amino acids (aa). The results showed that LmTLR14d has the typical structure of TLR molecule, which contains the extracellular domain of leucine-rich repeats (LRR), transmembrane domain, and intracellular domain of Toll/interleukin-1 receptor (TIR). The phylogenetic tree showed that LmTLR14d is a homologous gene of TLR14/18 in bony fish. Quantitative real-time PCR (qPCR) revealed that LmTLR14d was expressed in various healthy tissues, including immune and non-immune tissues. Pseudomonas aeruginosa infection up-regulated LmTLR14d in the supraneural body (SB), gill, and kidney tissues of infected Northeast Chinese lamprey. Immunofluorescence results showed that LmTLR14d was located in the cytoplasm of HEK 293T cells in clusters, and its subcellular localization was determined by the TIR domain. The immunoprecipitation results showed that LmTLR14d could recruit L.morii MyD88 (LmMyD88) but not L.morii TRIF (LmTRIF). Dual luciferase reporter results showed that LmTLR14d significantly enhanced the activity of L.morii NF-κβ (LmNF-κβ) promoter. Furthermore, co-transfection of LmTLR14d with MyD88 significantly enhanced the L.morii NF-κβ (LmNF-κβ) promoter activity. LmTLR14d can induce the expression of inflammatory cytokine genes il-6 and tnf-a downstream of NF-κB signal. This study suggested that LmTLR14d might play an important role in the innate immune signal transduction process of lamprey and revealed the origin and function of teleost-specific TLR14. [ABSTRACT FROM AUTHOR]

Lampreys are an ancient lineage of jawless fish for which the relationships among some lineages are uncertain. We addressed these information gaps for Lampetra species with a focus on western North America. Phylogenetic analysis using all publicly available sequences of two mitochondrial genes—cyt b and COI—supported designation of western North American Lampetra as a distinct genus from Lampetra in Europe, Asia, and eastern North America. Species delimitation analysis of cyt b sequences identified seven species, only three of which are currently recognized. Lampetra ayresii and L. richardsoni, regarded as separate under the "paired species concept," were not genetically distinct; we recommend synonymizing L. richardsoni with L. ayresii because the latter has precedence, yet continuing to recognize each ecotype using its current common name. Other than the widespread L. ayresii clade, all other species exhibited limited ranges often restricted to one or two locations. Within headwaters of the Willamette River, L. ayresii demonstrated strong genetic structure and lack of gene flow among subbasins, indicating that the subbasin scale may represent an appropriate management unit. However, the appropriate management scale in other areas may differ based on evolutionary histories and gene flow. Subsequent work is needed across western North America to better delineate the ranges of the aforementioned species and to evaluate whether other unrecognized taxa in this lineage may be present. [ABSTRACT FROM AUTHOR]

The ADAMs (a disintegrin and metalloproteinase) play regulatory roles in cell adhesion, migration and proteolysis. To explore the origin and evolution of ADAMs, this study identified the homologs of adam10 and adam17 in Lampetra morii and Lampetra japonica. Sequence analysis revealed that they share the same genomic structures with their counterparts in jawed vertebrates. The putative proteins possess conserved motifs, including a furin cut site (RXXR) for precursor processing, an enzyme catalytic motif (HEXGEHXXGXXH) for hydrolysis, and a Ca2+-binding motif (CGNXXXEXGEXCD) for stabilizing protein structure. In addition, a substrate recognition domain is present at the membrane-proximal region of lamprey ADAM17. The cytoplasmic region of lamprey ADAM10 contains a potential threonine phosphorylation site which has been shown to be activated by protein kinase C (PKC) in mammals. Both the adam10 and adam17 genes were constitutively expressed in the brain, kidney, and gills and were differentially regulated in the primary blood leukocytes by lipopolysaccharide (LPS) and pokeweed mitogen (PWM). Adam10 was induced by LPS but not PWM; conversely, adam17 was induced by PWM but not LPS. Taken together, our results suggest that the activation pathways and functions of ADAM10 and ADAM17 are conserved in agnathans. [ABSTRACT FROM AUTHOR]

Background: Little is known about the transformer stage of the parasitic lampreys, a brief but critical period that encompasses juvenile out-migration from rivers to lakes or oceans to begin parasitic feeding. Information about this life stage could have significant conservation implications for both imperiled and invasive lampreys. We investigated tag retention, survival, wound healing, and swim performance of newly transformed sea lamprey (Petromyzon marinus) implanted with a new micro-acoustic transmitter, the eel–lamprey acoustic transmitter (ELAT), in a controlled laboratory environment. Results: The 61-day survival of our tagged subjects was 71%, within the range reported in similar studies of juvenile lampreys. However, survival was significantly lower in the tagged animals (vs control), with no effect statistically attributable to measures of animal length, mass, condition, or population of origin (Great Lakes vs. Atlantic drainage). Mortality in tagged fish was concentrated in the first four days post-surgery, suggesting injury from the surgical process. An unusually long recovery time from anesthesia may have contributed to the increased mortality. In a simple burst swim assay, tagged animals swam significantly slower (− 22.5%) than untagged animals, but were not significantly different in endurance swim tests. A composite wound healing score at day four was a significant predictor of maximum burst swim speed at day 20, and wound condition was related to animal mass, but not length, at the time of tagging. Conclusions: Impairments to survival and swim performance of juvenile sea lamprey implanted with the ELAT transmitter were within currently reported ranges for telemetry studies with small, difficult to observe fishes. Our results could be improved with more refined anesthesia and surgical techniques. The ability to track migratory movements of imperiled and pest populations of parasitic lampreys will improve our ability to estimate vital rates that underlie recruitment to the adult population (growth, survival) and to investigate the environmental factors that regulate the timing and rates of movement, in wild populations. [ABSTRACT FROM AUTHOR]

Ontogeny is of paramount importance to understand evolutionary relationships of organisms. However, in the fossil record, early developmental stages are rarely preserved because of their unmineralized skeleton. Here, we describe the ontogeny of the Devonian jawless fish, Euphanerops longaevus, based on observations from more than 3500 specimens. The ontogeny of Euphanerops is compared with the development of the median fins of the extant jawless fish, the sea lamprey (Petromyzon marinus). From a subsample of 216 specimens of Euphanerops, we define three ontogenetic stages: larvae (2–38 mm total length (TL), mostly composed of "Scaumenella mesacanthi"), juveniles (28–98 mm TL), and adults (≥90 mm TL) based on the degree of skeletal development, chemical and microscopic compositions. Larvae display three cranial plates, a simple branchial apparatus, notochordal elements, and caudal fin supports. In juveniles, we document the development of paired anteroventral, anal, and median dorsal fins. Given how little information is generally available on ostracoderm ontogeny, the growth series of Euphanerops provides an unparalleled opportunity to understand the development of early vertebrate characters. [ABSTRACT FROM AUTHOR]

Lamprey underwent biliary atresia (BA) at its metamorphosis stage. In contrast to patients with BA who develop progressive disease, lamprey can grow and develop normally, suggesting that lamprey has several adaptations for BA. Here we show that adaptive changes in bile acid and cholesterol metabolism are produced after lamprey BA. Among 1102 differentially expressed genes (DGEs) after BA in lamprey, many are enriched in gene ontology (GO) terms and pathways related to steroid metabolism. We find that among the DGEs related to bile acids and cholesterol metabolism, the expression of cytochrome P450 family 7 subfamily A member 1 (CYP7A1), sodium-dependent taurine cotransport polypeptide (NTCP) are significantly downregulated, whereas nuclear receptor farnesoid X receptor (FXR), multidrug resistance-associated protein 3 (MRP3), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), sterol O-acyltransferase 1 (SOAT1), and ATP binding cassette subfamily A member 1 (ABCA1) are remarkably upregulated. The changes in expression level are also validated by RT-qPCR. Furthermore, the level of high-density lipoprotein-cholesterol (HDL-C) and low-density lipoprotein-cholesterol (LDL-C) in juvenile serum is higher compared to larvae. Taken together, the findings collectively indicate that after BA, lamprey may maintain bile acids and cholesterol homeostasis in liver tissue by inhibiting bile acids synthesis and uptake, promoting its efflux back to circulation, and enhancing cholesterol esterification for storage as lipid droplets and its egress to form nascent HDL (nHDL). Understanding the possible molecular mechanisms of lamprey metabolic adaptation sheds new light on the understanding of the development and treatment of diseases caused by abnormal bile acid and cholesterol metabolism in humans.

Lamprey homologues of the classic embryonic inducer Noggin are similar in expression pattern and functional properties to Noggin homologues of jawed vertebrates. All noggin genes of vertebrates apparently originated from a single ancestral gene as a result of genome duplications. nogginA, nogginB and nogginC of lampreys, like noggin1 and noggin2 of gnathostomes, demonstrate the ability to induce complete secondary axes with forebrain and eye structures when overexpressed in Xenopus laevis embryos. According to current views, this finding indicates the ability of lamprey Noggin proteins to suppress the activity of the BMP, Nodal/Activin and Wnt/beta-catenin signaling pathways, as shown for Noggin proteins of gnathostomes. In this work, by analogy with experiments in Xenopus embryos, we attempted to induce secondary axes in the European river lamprey Lampetra fluviatilis by injecting noggin mRNAs into lamprey eggs in vivo. Surprisingly, unlike what occurs in amphibians, secondary axis induction in the lampreys either by noggin mRNAs or by chordin and cerberus mRNAs, the inductive properties of which have been described, was not observed. Only wnt8a mRNA demonstrated the ability to induce secondary axes in the lampreys. Such results may indicate that the mechanism of axial specification in lampreys, which represent jawless vertebrates, may differ in detail from that in the jawed clade.

Abstract Progranulin (PGRN) is an autocrine growth factor that regulates cell proliferation, migration, wound healing, and tissue repair in mammals. Lamprey is the most primitive of the extant vertebrates and is regarded as the survivor of a once flourishing group of paleozoic vertebrates, with a history of more than 500 million years. To date, the evolutionary dynamics and the underlying function of the PGRNs remain largely unclear in lamprey. Here, we screened four genes encoding PGRNs from the genomes of Lethenteron reissneri and Petromyzon marinus, including one long form (named Lr-PGRN-L) and three short forms (named Lr-PGRN-S1, Lr-PGRN-S2, and Lr-PGRN-S3), and performed phylogenetic tree, functional domain, and synteny analyses to identify the evolutionary history of the four Lr-PGRNs. In addition, the expressions of the four Lr-pgrn family genes and the immune response against various pathogenic challenges were also investigated. We found that these genes were widely distributed in various tissues of lamprey and performed a variety of functions. Moreover, our results suggest that Lr-PGRN-S1 induces cell migration and proliferation, and is involved in repair after skin and spinal cord injury under appropriate conditions. Our findings are valuable because they improve the understanding of the evolutionary relationship of vertebrate pgrn genes, as well as providing new insights into the diverse and important roles of Lr-PGRNs.

Skin is a natural barrier between the body and the external environment, and this important multifunctional organ plays roles in body temperature regulation, sensory stimulation, mucus secretion, metabolite excretion and immune defense. Lampreys, as ancient vertebrates, rarely experience infection of damaged skin during farming and efficiently promote skin wound healing. However, the mechanism underlying these wound healing and regenerative effects is unclear. Our histology and transcriptomics results demonstrate that lampreys regenerate a nearly complete skin structure in damaged epidermis, including the secretory glands, and will almost not be infected, even if experiencing full-thickness damage. In addition, ATGL, DGL and MGL participate in the lipolysis process to provide space for infiltrating cells. A large number of red blood cells migrate to the site of injury and exert proinflammatory effects, upregulating the expression of proinflammatory factors such as IL-8 and IL-17. Based on a lamprey skin damage healing model, adipocytes and red blood cells in the subcutaneous fat layer can promote wound healing, which provides a new approach for the study of skin healing mechanisms. Transcriptome data reveal that mechanical signal transduction pathways are mainly regulated by focal adhesion kinase and that the actin cytoskeleton plays an important role in the healing of lamprey skin injuries. We identified RAC1 as a key regulatory gene that is necessary and partially sufficient for wound regeneration. Insights into the mechanisms of lamprey skin injury and healing will provide a theoretical basis for overcoming the challenges associated with chronic healing and scar healing in the clinic. [ABSTRACT FROM AUTHOR]

Transcription is known to be substage-specific in meiotic prophase I. If transcription is reactivated in the mid pachytene stage in mammals when synapsis is completed, then this process is observed in the zygotene stage in insects. The process of transcriptional reactivation has been studied in a small number of different taxa of invertebrates and vertebrates. Here, for the first time, we investigate synapsis and transcription in prophase I in the European river lamprey Lampetra fluviatilis (Petromyzontiformes, Cyclostomata), which is representative of jawless vertebrates that diverged from the main branch of vertebrates between 535 and 462 million years ago. We found that not all chromosomes complete synapsis in telomeric regions. Rounded structures were detected in chromatin and in some synaptonemal complexes, but their nature could not be determined conclusively. An analysis of RNA polymerase II distribution led to the conclusion that transcriptional reactivation in lamprey prophase I is not associated with the completion of chromosome synapsis. Monomethylated histone H3K4 is localized in meiotic chromatin throughout prophase I, and this pattern has not been previously detected in animals. Thus, the findings made it possible to identify synaptic and epigenetic patterns specific to this group and to expand knowledge about chromatin epigenetics in prophase I. [ABSTRACT FROM AUTHOR]

The expression of the corticotropin‐releasing hormone (PmCRH) and the CRH‐binding protein (PmCRHBP) mRNAs was studied by in situ hybridization in the brain of prolarvae, larvae, and adults of the sea lamprey Petromyzon marinus. We also generated an antibody against the PmCRH mature peptide to study the distribution of PmCRH‐immunoreactive cells and fibers. PmCRH immunohistochemistry was combined with antityrosine hydroxylase immunohistochemistry, PmCRHBP in situ hybridization, or neurobiotin transport from the spinal cord. The most numerous PmCRH‐expressing cells were observed in the magnocellular preoptic nucleus‐paraventricular nucleus and in the superior and medial rhombencephalic reticular formation. PmCRH expression was more extended in adults than in larvae, and some cell populations were mainly (olfactory bulb) or only (striatum, ventral hypothalamus, prethalamus) observed in adults. The preopto‐paraventricular fibers form conspicuous tracts coursing toward the neurohypophysis, but many immunoreactive fibers were also observed coursing in many other brain regions. Brain descending fibers in the spinal cord mainly come from cells located in the isthmus and in the medial rhombencephalic reticular nucleus. The distribution of PmCRHBP‐expressing neurons was different from that of PmCRH cells, with cells mainly present in the septum, striatum, preoptic region, tuberal hypothalamus, pretectum, pineal complex, isthmus, reticular formation, and spinal cord. Again, expression in adults was more extended than in larvae. PmCRH‐ and PmCRHBP‐expressing cells are different, excluding colocalization of these substances in the same neuron. Present findings reveal a complex CRH/CRHBP system in the brain of the oldest extant vertebrate group, the agnathans, which shows similarities but important divergences with that of mammals. [ABSTRACT FROM AUTHOR]

Bone morphogenic protein/retinoic acid inducible neural-specific proteins (BRINPs) and astrotactins (ASTNs) are two members of membrane attack complex/perforin-like (MACPF) superfamily proteins that present high expression in the growing and mature vertebrate neurons. Lamprey has a unique evolutionary status as a representative of the oldest jawless vertebrates, making it an ideal animal model for understanding vertebrate evolution. The evolutionary origins of BRINPs and ASTNs genes in vertebrates, however, have not been shown in lampreys. Here, BRINP and ASTN genes were found in lamprey genomes and the evolutionary relationships of them were investigated by phylogenetic analysis. Protein domains, motifs, genetic structure, and crystal structure analysis revealed that the features of BRINP and ASTN appear to be conserved in vertebrates. Genomic synteny analysis indicated that lamprey BRINP and ASTN neighbor genes differed dramatically from jawed vertebrate. Real-time quantitative results illustrated that the BRINP and ASTN genes family might take part in immune defence and spinal cord injury repair. This study not only enriches a better understanding of the evolution of the BRINP and ASTN genes but also offers a foundation for exploring their roles in the development of the vertebrate central nervous system (CNS). • ASTN and BRINP genes identified and cloned firstly from Lethenteron reissneri. • The evolutionary relationship of ASTN and BRINP genes among different species is indicated. • BRINP and ASTN genes family might take part in immune defence and spinal cord injury repair. [ABSTRACT FROM AUTHOR]

Abstract Background The endostyle is an epithelial exocrine gland found in non-vertebrate chordates (amphioxi and tunicates) and the larvae of modern lampreys. It is generally considered to be an evolutionary precursor of the thyroid gland of vertebrates. Transformation of the endostyle into the thyroid gland during the metamorphosis of lampreys is thus deemed to be a recapitulation of a past event in vertebrate evolution. In 1906, Stockard reported that the thyroid gland in hagfish, the sister cyclostome group of lampreys, develops through an endostyle-like primordium, strongly supporting the plesiomorphy of the lamprey endostyle. However, the findings in hagfish thyroid development were solely based on this single study, and these have not been confirmed by modern molecular, genetic, and morphological data pertaining to hagfish thyroid development over the last century. Results Here, we showed that the thyroid gland of hagfish undergoes direct development from the ventrorostral pharyngeal endoderm, where the previously described endostyle-like primordium was not found. The developmental pattern of the hagfish thyroid, including histological features and regulatory gene expression profiles, closely resembles that found in modern jawed vertebrates (gnathostomes). Meanwhile, as opposed to gnathostomes but similar to non-vertebrate chordates, lamprey and hagfish share a broad expression domain of Nkx2-1/2-4, a key regulatory gene, in the pharyngeal epithelium during early developmental stages. Conclusions Based on the direct development of the thyroid gland both in hagfish and gnathostomes, and the shared expression profile of thyroid-related transcription factors in the cyclostomes, we challenge the plesiomorphic status of the lamprey endostyle and propose an alternative hypothesis where the lamprey endostyle could be obtained secondarily in crown lampreys.

Odorant transport is of fundamental and applied importance. Using computational simulations, we studied odorant transport in an anatomically accurate model of the nasal passage of a hagfish (probably Eptatretus stoutii). We found that ambient water is sampled widely, with a significant ventral element. Additionally, there is a bilateral element to olfactory flow, which enters the single nostril in two narrow, laminar streams that are then split prior to the nasal chamber by the anterior edge of the central olfactory lamella. An appendage on this lamella directs a small portion (10–14%) of the overall nasal flow to the olfactory sensory channels. Much of the remaining flow is diverted away from the sensory channels by two peripheral channels. The anterior edge of the central olfactory lamella, together with a jet-impingement mechanism, disperses flow over the olfactory surfaces. Diffusion of odorant from bulk water to the olfactory surfaces is facilitated by the large surface area:volume ratio of the sensory channels, and by a resistance-based hydrodynamic mechanism that leads to long residence times (up to 4.5 s) in the sensory channels. With increasing volumetric flow rate, the rate of odorant transfer to the olfactory surfaces increases, but the efficiency of odorant uptake decreases, falling in the range 2–6%. Odorant flux decreases caudally across the olfactory surfaces, suggesting in vivo a preponderance of olfactory sensory neurons on the anterior part of each olfactory surface. We conclude that the hagfish has a subtle anatomy for locating and capturing odorant molecules. [Display omitted] • The monorhinal hagfish can smell in stereo. • Jet impaction disperses olfactory flow. • Resistance-based hydrodynamic mechanism aids odorant capture. • Only about 10% nasal flow sampled for olfactory purposes. • Odorant capture efficiency comparable to lower range of dog. [ABSTRACT FROM AUTHOR]

Sea lampreys are a vertebrate model of interest for the study of spontaneous axon regeneration after spinal cord injury (SCI). Axon regeneration research in lampreys has focused on the study of giant descending neurons, but less so on neurochemically-distinct descending neuronal populations with small caliber axons. Corticotropin-releasing hormone (CRH) is a neuropeptide that regulates the stress response or locomotion. CRH is also a neuropeptide of interest in the SCI context because descending CRHergic projections from the Barrington’s nucleus control micturition behavior in mammals. Recent work from our group revealed that in sea lampreys the CRHergic innervation of the spinal cord is only of descending origin. Thus, the lack of intrinsic CRH spinal cord neurons provides the opportunity to analyze the regeneration of this descending system by using immunofluorescence methods. Here, we used an antibody against the sea lamprey mature CRH peptide, confocal microscopy, lightning adaptive deconvolution, and ImageJ to analyze the regenerative capacity of the descending CRH-immunoreactive (-ir) axons of larval sea lampreys after a complete SCI at the level of the fifth gill. At 10 weeks post-lesion, when behavioral analyses showed that injured animals had recovered normal appearing locomotion, our results revealed a full recovery of the number of CRH-ir profiles (axons) at the level of the sixth gill. Thus, the CRH descending axons of lampreys fully regenerate after a complete SCI. Our study provides a new model to study spontaneous and successful axonal regeneration in a specific neuronal type with small caliber axons by using simple immunohistochemical methods.

While the anatomical properties of regenerated axons across spinal cord lesion sites have been studied extensively, little is known of how the functional properties of regenerated synapses compared to those in unlesioned animals. This study aims to compare the properties of synapses made by regenerated axons with unlesioned axons using the lamprey, a model system for spinal injury research, in which functional locomotor recovery after spinal cord lesions is associated with axonal regeneration across the lesion site. Regenerated synapses below the lesion site did not differ from synapses from unlesioned axons with respect to the amplitude and duration of single excitatory postsynaptic potentials. They also showed the same activity-dependent depression over spike trains. However, regenerated synapses did differ from unlesioned synapses as the estimated number of synaptic vesicles was greater and there was evidence for increased postsynaptic quantal amplitude. For axons above the lesion site, the amplitude and duration of single synaptic inputs also did not differ significantly from unlesioned animals. However, in this case, there was evidence of a reduction in release probability and inputs facilitated rather than depressed over spike trains. Synaptic inputs from single regenerated axons below the lesion site thus do not increase in amplitude to compensate for the reduced number of descending axons after functional recovery. However, the postsynaptic input was maintained at the unlesioned level using different synaptic properties. Conversely, the facilitation from the same initial amplitude above the lesion site made the synaptic input over spike trains functionally stronger. This may help to increase propriospinal activity across the lesion site to compensate for the lesion-induced reduction in supraspinal inputs. The animal experiments were approved by the Animal Ethics Committee of Cambridge University.

The innate immune system is the body's first line of defense against pathogens and involves antibody and complement system-mediated antigen removal. Immune-response-related complement molecules have been identified in lamprey, and the occurrence of innate immune response via the mannose-binding lectin-associated serine proteases of the lectin cascade has been reported. We have previously shown that lamprey (Lampetra japonica) serum can efficiently and specifically eliminate foreign pathogens. Therefore, we aimed to understand the immune mechanism of lamprey serum in this study. We identified and purified a novel spherical lectin (LSSL) from lamprey serum. LSSL had two structural calcium ions coordinated with conserved amino acids, as determined through cryogenic electron microscopy. LSSL showed high binding capacity with microbial and mammalian glycans and demonstrated agglutination activity against bacteria. Phylogenetic analysis revealed that LSSL was transferred from phage transposons to the lamprey genome via horizontal gene transfer. Furthermore, LSSL was associated with mannose-binding lectin-associated serine protease 1 and promoted the deposition of the C3 fragment on the surface of target cells upon binding. These results led us to conclude that LSSL initiates and regulates agglutination, resulting in exogenous pathogen and tumor cell eradication. Our observations will give a greater understanding of the origin and evolution of the complement system in higher vertebrates and lead to the identification of novel immune molecules and pathways for defense against pathogens and tumor cells. Key points: A novel serum spherical lectin from lamprey was identified which have agglutination activity against bacteria dependent on calcium. The crystal structure of LSSL was determined, and adhered to both microbial and mammalian glycans with high binding capacity. The role of LSSL was associated with MASP-1 and recruited C3 deposition for pathogen elimination. [ABSTRACT FROM AUTHOR]

Abstract Background Pineal-related organs in cyclostomes, teleosts, amphibians, and reptiles exhibit color opponency, generating antagonistic neural responses to different wavelengths of light and thereby sensory information about its “color”. Our previous studies suggested that in zebrafish and iguana pineal-related organs, a single photoreceptor cell expressing both UV-sensitive parapinopsin and green-sensitive parietopsin generates color opponency in a “one-cell system.” However, it remains unknown to what degree these opsins and the single cell-based mechanism in the pineal color opponency are conserved throughout non-mammalian vertebrates. Results We found that in the lamprey pineal organ, the two opsins are conserved but that, in contrast to the situation in other vertebrate pineal-related organs, they are expressed in separate photoreceptor cells. Intracellular electrophysiological recordings demonstrated that the parietopsin-expressing photoreceptor cells with Go-type G protein evoke a depolarizing response to visible light. Additionally, spectroscopic analyses revealed that parietopsin with 11-cis 3-dehydroretinal has an absorption maximum at ~570 nm, which is in approximate agreement with the wavelength (~560 nm) that produces the maximum rate of neural firing in pineal ganglion cells exposed to visible light. The vesicular glutamate transporter is localized at both the parietopsin- and parapinopsin-expressing photoreceptor terminals, suggesting that both types of photoreceptor cells use glutamate as a transmitter. Retrograde tracing of the pineal ganglion cells revealed that the terminal of the parietopsin-expressing cells is located close enough to form a neural connection with the ganglion cells, which is similar to our previous observation for the parapinopsin-expressing photoreceptor cells and the ganglion cells. In sum, our observations point to a “two-cell system” in which parietopsin and parapinopsin, expressed separately in two different types of photoreceptor cells, contribute to the generation of color opponency in the pineal ganglion cells. Conclusion Our results indicate that the jawless vertebrate, lamprey, employs a system for color opponency that differes from that described previously in jawed vertebrates. From a physiological viewpoint, we propose an evolutionary insight, the emergence of pineal “one-cell system” from the ancestral “multiple (two)-cell system,” showing the opposite evolutionary direction to that of the ocular color opponency.