Highly Concentrated Linear Guanidine Amides from the Marine Sipunculid Phascolosoma granulatum.

The chemical diversity of annelids, particularly those belonging to the class Sipuncula, remains largely unexplored. However, as part of a Marine Biodiscovery program in Ireland, the peanut worm Phascolosoma granulatum emerged as a promising source of unique metabolites. The purification of the MeOH/CH2Cl2 extract of this species led to the isolation of six new linear guanidine amides, named phascolosomines A-F (1-6). NMR analysis allowed for the elucidation of their structures, all of which feature a terminal guanidine, central amide linkage, and a terminal isobutyl group. Notably, these guanidine amides were present in unusually high concentrations, comprising ∼3% of the dry mass of the organism. The primary concentration of the phascolosomines in the viscera is similar to that previously identified in linear amides from sipunculid worms and marine fireworms. The compounds from sipunculid worms have been hypothesized to be toxins, while those from fireworms are reported to be defensive irritants. However, screening of the newly isolated compounds for inhibitory bioactivity showed no significant inhibition in any of the assays conducted.

Annelid Coelomic Fluid Proteins.

The coelomic cavity is part of the main body plan of annelids. This fluid filled space takes up a considerable volume of the body and serves as an important site of exchange of both metabolites and proteins. In addition to low molecular substances such as amino acids and glucose and lactate, the coelomic fluid contains different proteins that can arise through release from adjacent tissues (intestine) or from secretion by coelomic cells. In this chapter, we will review the current knowledge about the proteins in the annelid coelomic fluid. Given the number of more than 20,000 extant annelid species, existing studies are confined to a relatively few species. Most studies on the oligochaetes are confined to the earthworms-clearly because of their important role in soil biology. In the polychaetes (which might represent a paraphyletic group) on the other hand, studies have focused on a few species of the Nereidid family. The proteins present in the coelomic fluid serve different functions and these have been studied in different taxonomic groups. In oligochaetes, proteins involved antibacterial defense such as lysenin and fetidin have received much attention in past and ongoing studies. In polychaetes, in contrast, proteins involved in vitellogenesis and reproduction, and the vitellogenic function of coelomic cells have been investigated in more detail. The metal binding metallothioneins as well as antimicrobial peptides, have been investigated in both oligochaetes and polychaetes. In the light of the literature available, this review will focus on lipoproteins, especially vitellogenin, and proteins involved in defense reactions. Other annelid groups such as the Pogonophora, Echiura, and Sipuncula (now considered polychaetes), have not received much attention and therefore, this overview is far from being complete.

First Discovery of Pogonophora (Annelida, Siboglinidae) in the Kara Sea Coincide with the Area of High Methane Concentration.

Here we report the first finding of a frenulate pogonophoran (Annelida, Siboglinidae) in the southern part of the Kara Sea. This finding was made in the Yenisei Gulf in the region of the highest methane concentrations, resulting from the degradation of permafrost under the influence of river flow. It has been suggested that pogonophorans are indicators of hydrocarbon manifestations of various genesis.

Bioluminescence properties of Thelepus japonicus (Annelida: Terebelliformia).

Terebelliformia is a benthic group of marine annelid worms. The bioluminescence of several species has been reported in taxonomical and histological literature, but very little information is known about the biochemical aspects of this phenomenon. In this study, we examined the basic properties of the luminescence system using an extract of the Japanese terebelliform worm, Thelepus japonicus. The bioluminescence extract was soluble in water, and emitted blue-green light at λmax 508 nm following the addition of divalent cations. This triggering action was highly specific to Fe2+ and addition of ATP, H2 O2 or coelenterazine did not enhance activity. The bioluminescence was inactivated by heat treatment and organic solvents, indicating the involvement of a protein component. These results suggested that Thelepus worm produces light using a novel system that differs from that in other known luminescent annelids.

First biochemical and crystallographic characterization of a fast-performing ferritin from a marine invertebrate.

Ferritin, a multimeric cage-like enzyme, is integral to iron metabolism across all phyla through the sequestration and storage of iron through efficient ferroxidase activity. While ferritin sequences from ∼900 species have been identified, crystal structures from only 50 species have been reported, the majority from bacterial origin. We recently isolated a secreted ferritin from the marine invertebrate Chaetopterus sp. (parchment tube worm), which resides in muddy coastal seafloors. Here, we present the first ferritin from a marine invertebrate to be crystallized and its biochemical characterization. The initial ferroxidase reaction rate of recombinant Chaetopterus ferritin (ChF) is 8-fold faster than that of recombinant human heavy-chain ferritin (HuHF). To our knowledge, this protein exhibits the fastest catalytic performance ever described for a ferritin variant. In addition to the high-velocity ferroxidase activity, ChF is unique in that it is secreted by Chaetopterus in a bioluminescent mucus. Previous work has linked the availability of Fe2+ to this long-lived bioluminescence, suggesting a potential function for the secreted ferritin. Comparative biochemical analyses indicated that both ChF and HuHF showed similar behavior toward changes in pH, temperature, and salt concentration. Comparison of their crystal structures shows no significant differences in the catalytic sites. Notable differences were found in the residues that line both 3-fold and 4-fold pores, potentially leading to increased flexibility, reduced steric hindrance, or a more efficient pathway for Fe2+ transportation to the ferroxidase site. These suggested residues could contribute to the understanding of iron translocation through the ferritin shell to the ferroxidase site.

Phylogenomic analyses unravel annelid evolution.

Annelida, the ringed worms, is a highly diverse animal phylum that includes more than 15,000 described species and constitutes the dominant benthic macrofauna from the intertidal zone down to the deep sea. A robust annelid phylogeny would shape our understanding of animal body-plan evolution and shed light on the bilaterian ground pattern. Traditionally, Annelida has been split into two major groups: Clitellata (earthworms and leeches) and polychaetes (bristle worms), but recent evidence suggests that other taxa that were once considered to be separate phyla (Sipuncula, Echiura and Siboglinidae (also known as Pogonophora)) should be included in Annelida. However, the deep-level evolutionary relationships of Annelida are still poorly understood, and a robust reconstruction of annelid evolutionary history is needed. Here we show that phylogenomic analyses of 34 annelid taxa, using 47,953 amino acid positions, recovered a well-supported phylogeny with strong support for major splits. Our results recover chaetopterids, myzostomids and sipunculids in the basal part of the tree, although the position of Myzostomida remains uncertain owing to its long branch. The remaining taxa are split into two clades: Errantia (which includes the model annelid Platynereis), and Sedentaria (which includes Clitellata). Ancestral character trait reconstructions indicate that these clades show adaptation to either an errant or a sedentary lifestyle, with alteration of accompanying morphological traits such as peristaltic movement, parapodia and sensory perception. Finally, life history characters in Annelida seem to be phylogenetically informative.

Improvement of erectile dysfunction by the active pepide from Urechis unicinctus by high temperature/pressure and ultra - wave assisted lysis in Streptozotocin Induced Diabetic Rats.

INTRODUCTION: We investigate the effect of active peptide from Urechis unicinctus (UU) by high temperature/pressure and ultra-wave assisted lysis on erectile dysfunction in streptozotocin-induced diabetic rats. MATERIALS AND METHODS: Forty 12-week-old Sprague-Dawley rats were used in this study. Diabetes was induced by a one-time intraperitoneal injection of streptozotocin (50mg/kg). One week later, the diabetic rats were randomly divided into four groups: normal control, untreated diabetes control, and groups treated with 100 or 500mg/kg/d UU peptide. Rats were fed with UU peptide by intragastric administration for 8 weeks. After 8 weeks, penile hemodynamic function was evaluated in all groups by measuring the intracavernosal pressure after electrostimulating the cavernous nerve. Nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) activities were measured and endothelial nitric oxide synthase (eNOS) and neuronal NOS (nNOS) protein expression. was determined by Western blot. RESULTS: Maximum intracavernosal pressure in diabetic control rats decreased significantly compared to normal control rats, and was increased significantly compared to untreated diabetic rats after UU peptide supplementation. Treatment with the higher dose of UU peptide significantly increased the NO and cGMP levels compared with the diabetic control group. Decreased activity and expression eNOS and nNOS were found in the diabetic rats compared with the normal control group. Decreased eNOS and nNOS in diabetic rats were improved by UU peptide administration. CONCLUSIONS: Active peptide from UU ameliorates erectile function in a streptozotocin induced diabetic rat model of erectile dysfunction.

Complete feminization of catfish by feeding Limnodilus, an annelid worm collected in contaminated streams.

BACKGROUND: Feminization of animals derived from areas polluted by endocrine disrupting chemicals (EDCs) has been observed in all classes of vertebrates. However, feminization of artificially reared offspring by feeding of specific living organisms has never been reported. METHODS: Different food (including Limnodilus spp collected from the wild) and time treatment were applied to southern catfish. In addition, EDCs in Limnodilus spp., an annelid worm collected from wild contaminated small streams, was detected by LC-MS (Liquid chromatography-mass spectrometry). Serum estradiol-17ß and vitellogenin (VTG) levels and gonadal Sf1, Dmrt1, Foxl2, Cyp19a1a expression levels in the catfish were measured through Estradiol/VTG EIA Kit and real-time PCR. RESULTS: Here we report that feeding of Limnodilus spp. resulted in complete feminization of southern catfish, which has a 1:1 sex ratio in wild conditions. Furthermore, HPLC analysis showed that the extraction of Limnodilus spp. contained EDCs, including bisphenol A (BPA), diethylstilbestrol (DES), 4-tert-octylphenol (4-t-OP) and 4-nonylphenol (4-NP), which were further confirmed by LC-MS. Feeding southern catfish using commercial diets sprayed with EDCs cocktail also resulted in 100% female, whereas the control fish displayed approximate 1:1 sex ratio. Limnodilus spp. fed fish displayed similar serum estradiol-17ß and VTG levels and gonadal Sf1, Dmrt1, Foxl2, Cyp19a1a expression levels to those of female control. CONCLUSION: These results demonstrated that EDCs in Limnodilus spp. cause southern catfish feminization by affecting aromatase expression and endogenous estrogen level. This is the first report showing that feeding of any living organism resulted in complete feminization of a vertebrate.

Unravelling the ultrastructure and mineralogical composition of fireworm stinging bristles.

Amphinomid fireworms are notorious for their stinging dorsal bristles (notochaetae), but it is still unclear whether the irritation they cause is merely mechanical or if the notochaetae contain toxins. Furthermore, although fireworm chaetae have always been described as calcareous, their composition has never been investigated to date and strong debates are ongoing on their internal structure. Unravelling the native ultrastructure and composition of fireworm chaetae is the first crucial step to assess whether the hypothesis of toxin vehiculation could be fully considered. We examined for the first time the chemical and mineralogical composition, the ultrastructure and the external structure of the dorsal and ventral chaetae of the large species Hermodice carunculata. All the measurements were carried out on samples prepared without the use of chemical reagents, except for those targeted to investigate if decalcification altered the ultrastructure of the chaetae. A crystal-chemical strategy, combining chemical, diffraction and thermal analyses clearly showed the occurrence of crystalline calcium carbonate and clusters of phosphatic amorphous material. Scanning electron micrographs and energy dispersive X-ray measurements showed that the dorsal chaetae have an extremely shallow insertion point in the body respect to the ventral chaetae, that could facilitate the release of the notochaetae in the environment. Their proximal part is characterized by canals with a hexagonal pattern rich in Ca and P, followed by a large cavity upwards. The harpoon-shaped ends and the central canals of the notochaetae completely disappeared after exposure to EDTA. The notochaetae are hollow and may be able to vehicle toxins. The absence of the honeycomb pattern in the distal part of the notochaetae and their slenderness probably contribute to their brittleness and high sensitivity to breakage on contact. These observations constitute keystone understandings to shed light on fireworm defensive and offensive capacities and their ecological success.

Raman spectroscopic study of the mineral composition of cirratulid tubes (Annelida, Polychaeta).

Raman spectroscopy was used to determine the mineralogical composition of the calcareous tubes of three species belonging to the family Cirratulidae. In all three cases, the tubes were found to be aragonitic, confirming previous inferences based on EDX and thin section studies, and corroborated by new EDX analyses revealing the presence of Sr but no Mg. Biomineralization in cirratulids is first recorded in the Oligocene epoch, at a time of aragonite seas. Similarly, the mineralogies of the earliest skeletons matched seawater chemistry in three other polychaete groups that independently evolved calcareous skeletons.

Structural characterization of hemoglobins from Monilifera and Frenulata tubeworms (Siboglinids): first discovery of giant hexagonal-bilayer hemoglobin in the former "Pogonophora" group.

Siboglinids are symbiotic polychete annelids having hemoglobins as essential oxygen- and sulfide-carriers for their endosymbiotic bacteria. We analyzed the structure of the hemoglobins from two species of siboglinids: the monilifera Sclerolinum contortum and the frenulata Oligobrachia webbi (i.e. haakonmosbiensis) from Norwegian cold seeps. Measured by Multi-Angle Laser Light Scattering (MALLS), Sclerolinum shows a 3190+/-50 kDa hexagonal bilayer hemoglobin (HBL-Hb) and a 461+/-46 kDa ring-Hb, just as vestimentifera, whereas Oligobrachia has a 409+/-3.7 kDa ring-Hb only. Electrospray Ionization-Mass Spectrometry (ESI-MS) showed Sclerolinum HBL-Hb composed of seven monomeric globins (15-16 kDa), three disulfide-bonded globin heterodimers and three linkers. The heterodimers always contain globin-b (15814.4+/-1.5 Da). Sclerolinum ring-Hb is composed of globins and dimers with identical masses as its HBL-Hb, but lacks linkers. Oligobrachia ring-Hb has three globin monomers (14-15 kDa) only, with no disulfide-bonded dimers. Comparison of Sclerolinum hemoglobins between Storegga and Haakon Mosby Mud Volcano, using the normalized height of deconvoluted ESI-MS peaks, shows differences in globin monomers abundances that could reflect genetic differences or differential gene expression between distinct seep populations. The discovery of HBL-Hb in Sclerolinum is a new element supporting the hypothesis of monilifera being phylogenetically more closely related to vestimentifera, than to frenulata.

Cloning and expression of cDNA encoding a cysteine protease inhibitor from clamworm and its possible use in managing Anoplophora glabripennis Motschulsky (Coleoptera: Cerambycidae).

A cDNA encoding cysteine protease inhibitor (CPI) was isolated from the cDNA library of clamworm Perinereis aibuhitensis Grube. The deduced amino acid sequence analysis showed that the protein had 51%, 48%, and 48% identity with Zgc:153129 from Danio rerio, cystatin B from Theromyzon tessulatum and ChainA, stefin B tetramer from Homo sapiens, respectively. The gene was cloned into the intracellular expression vector pET-15b and expressed in Escherichia coli. The recombinant CPI (PA-CPI) was purified by affinity chromatography on Ni-charged resin and ion-exchange chromatography on DEAE-Sepharose FF. The relative molecular mass of PA-CPI was 16 KDa deduced by SDS-PAGE. Activity analysis showed that the recombinant protein could inhibit the proteolytic activity of papain. A constitutive and secretive expression vector was also constructed, and the cDNA encoding CPI was subcloned into the vector for extracellular expression. Western blotting analysis results showed that the PA-CPI was secreted into the medium. Bioassay demonstrated that E. coli DH5alpha harboring pUC18ompAcat-CPI showed a significant difference in mortality to the Asian longhorned beetle Anoplophora glabripennis compared with untransformed E. coli DH5alpha and control.

Evolutionary History of the Globin Gene Family in Annelids.

Animals depend on the sequential oxidation of organic molecules to survive; thus, oxygen-carrying/transporting proteins play a fundamental role in aerobic metabolism. Globins are the most common and widespread group of respiratory proteins. They can be divided into three types: circulating intracellular, noncirculating intracellular, and extracellular, all of which have been reported in annelids. The diversity of oxygen transport proteins has been underestimated across metazoans. We probed 250 annelid transcriptomes in search of globin diversity in order to elucidate the evolutionary history of this gene family within this phylum. We report two new globin types in annelids, namely androglobins and cytoglobins. Although cytoglobins and myoglobins from vertebrates and from invertebrates are referred to by the same name, our data show they are not genuine orthologs. Our phylogenetic analyses show that extracellular globins from annelids are more closely related to extracellular globins from other metazoans than to the intracellular globins of annelids. Broadly, our findings indicate that multiple gene duplication and neo-functionalization events shaped the evolutionary history of the globin family.

The origin identification method for crude drugs derived from arthropods and annelids using molecular biological techniques.

We evaluated whether the origins of crude drugs derived from arthropods and annelids could be identified using molecular biological techniques. DNA was extracted from 20 crude drugs prepared from different animals using a commercial kit with added phenol treatment. The target regions used to identify origin were the mitochondrial 16S ribosomal RNA (rRNA), 12S rRNA, and cytochrome oxidase subunit I (COI) gene regions. Extracted DNA was amplified by polymerase chain reaction, and then sequenced by the Sanger method. The aligned sequences were compared with all available sequences using BLAST to estimate the origins of the crude drugs. The origin of crude drugs used in this study could be estimated using this method. The COI region was the best for identifying origin among three regions examined, based on the success rate of PCR amplification and analysis. Moreover, the 12S rRNA region was also useful for origin identification, with the exception of the earthworm. However, the origin of some crude drugs could not be strictly identified due to matches to various species in all three regions. One likely cause was that the species of origin of a crude drug has not been registered in DNA databases. We found that even the same crude drug from the same pharmaceutical company had different origins by production lot or import source country. Therefore, this method is useful not only for DNA-based origin identification but also quality control of production lots.

The structural analysis of large noncovalent oxygen binding proteins by MALLS and ESI-MS: a review on annelid hexagonal bilayer hemoglobin and crustacean hemocyanin.

Understanding the function of macromolecular complexes is related to a precise knowledge of their structure. These large complexes are often fragile high molecular mass noncovalent multimeric proteins. Classical biochemical methods for determination of their native mass and subunit composition were used to resolve their quaternary structure, sometimes leading to different models. Recently, the development of mass spectrometry and multi-angle laser light scattering (MALLS) has enabled absolute determination of native masses and subunit masses. Electrospray ionization mass spectrometry (ESI-MS) was used in denaturing and native conditions to probe subunit composition and noncovalent assemblies masses up to 2.25 MDa. In a complementary way, MALLS provides mass and size estimation in various aqueous solvents. ESI-MS method can also give insights into post-translational modifications (glycosylation, disulfide bridges ). By combining native mass and subunit composition data, structural models can be proposed for large edifices such as annelid extracellular hexagonal bilayer hemoglobins (HBL Hb) and crustacean hemocyanins (Hc). Association/dissociation mechanisms, protein-protein interactions, structural diversity among species and environmental adaptations can also be addressed with these methods. With their absolute mass determination, the very high precision of spectrometry and the versatile nature of light scattering, ESI-MS and MALLS have provided a wealth of data helping to resolve parts of controversies for HBL-Hb models and opening access to new fields of investigation in structural diversity and molecular adaptation. In this review we will focus on annelid HBL-Hb and on crustacean Hc and on the original contributions of ESI-MS and MALLS in this field.

Interaction of giant extracellular Glossoscolex paulistus hemoglobin (HbGp) with zwitterionic surfactant N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS): effects of oligomeric dissociation.

The present work focuses on the interaction between the zwitterionic surfactant N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS) and the giant extracellular hemoglobin of Glossoscolex paulistus (HbGp). Electronic optical absorption, fluorescence emission and circular dichroism spectroscopy techniques, together with Gel-filtration chromatography, were used in order to evaluate the oligomeric dissociation as well as the autoxidation of HbGp as a function of the interaction with HPS. A peculiar behavior was observed for the HPS-HbGp interaction: a complex ferric species formation equilibrium was promoted, as a consequence of the autoxidation and oligomeric dissociation processes. At pH 7.0, HPS is more effective up to 1mM while at pH 9.0 the surfactant effect is more intense above 1mM. Furthermore, the interaction of HPS with HbGp was clearly less intense than the interaction of this hemoglobin with cationic (CTAC) and anionic (SDS) surfactants. Probably, this lower interaction with HPS is due to two factors: (i) the lower electrostatic attraction between the HPS surfactant and the protein surface ionic sites when compared to the electrostatic interaction between HbGp and cationic and anionic surfactants, and (ii) the low cmc of HPS, which probably reduces the interaction of the surfactant in the monomeric form with the protein. The present work emphasizes the importance of the electrostatic contribution in the interaction between ionic surfactants and HbGp. Furthermore, in the whole HPS concentration range used in this study, no folding and autoxidation decrease induced by this surfactant were observed. This is quite different from the literature data on the interaction between surfactants and tetrameric hemoglobins, that supports the occurrence of this behavior for the intracellular hemoglobins at low surfactant concentration range. Spectroscopic data are discussed and compared with the literature in order to improve the understanding of hemoglobin-surfactant interaction as well as the acid isoelectric point (pI) influence of the giant extracellular hemoglobins on their structure-activity relationship.

Immunolocalization of serotonin in Onychophora argues against segmental ganglia being an ancestral feature of arthropods.

BACKGROUND: Onychophora (velvet worms) represent the most basal arthropod group and play a pivotal role in the current discussion on the evolution of nervous systems and segmentation in arthropods. Although there is a wealth of information on the immunolocalization of serotonin (5-hydroxytryptamine, 5-HT) in various euarthropods, as yet no comparable localization data are available for Onychophora. In order to understand how the onychophoran nervous system compares to that of other arthropods, we studied the distribution of serotonin-like immunoreactive neurons and histological characteristics of ventral nerve cords in Metaperipatus blainvillei (Onychophora, Peripatopsidae) and Epiperipatus biolleyi (Onychophora, Peripatidae). RESULTS: We demonstrate that paired leg nerves are the only segmental structures associated with the onychophoran nerve cord. Although the median commissures and peripheral nerves show a repeated pattern, their arrangement is independent from body segments characterized by the position of legs and associated structures. Moreover, the somata of serotonin-like immunoreactive neurons do not show any ordered arrangement in both species studied but are instead scattered throughout the entire length of each nerve cord. We observed neither a serially iterated nor a bilaterally symmetric pattern, which is in contrast to the strictly segmental arrangement of serotonergic neurons in other arthropods. CONCLUSION: Our histological findings and immunolocalization experiments highlight the medullary organization of the onychophoran nerve cord and argue against segmental ganglia of the typical euarthropodan type being an ancestral feature of Onychophora. These results contradict a priori assumptions of segmental ganglia being an ancestral feature of arthropods and, thus, weaken the traditional Articulata hypothesis, which proposes a sistergroup relationship of Annelida and Arthropoda.

Partial characterization of giant extracellular hemoglobin of Glossoscolex paulistus: a MALDI-TOF-MS study.

In this work, MALDI-TOF-MS analysis was performed to obtain information on the molecular mass of the different subunits from the giant extracellular hemoglobin of Glossoscolex paulistus (HbGp) in the oxy-form. Experiments were performed for the whole protein at pH 7.0, for the partially dissociated protein at pH 9.0, and for the fraction obtained from gel filtration in Sephadex G-200, at pH 9.0, corresponding to the isolated monomer d. Besides that, experiments were performed for the whole protein treated with 2-mercaptoethanol in order to monitor the effects of reduction of the disulfide bonds, which are expected to maintain the trimer (abc) in the native molecule. The results are compared to those reported for the homologous hemoglobin of Lumbricus terrestris (HbLt) and some tentative assignments are made for the observed polypeptides. The monomer d is found to exist in, at least, two major forms of identical proportions with masses of 16,355+/-25 and 16,428+/-24 Da, respectively. Two minor forms were also observed around 16 kDa for the monomers. Upon disulfide bonds reduction the peak associated to the trimer is absent in the mass spectrum, and new peaks assigned tentatively to the monomers a, b and c on the basis of comparison with Lumbricus terrestris hemoglobin literature data are observed. Their molecular masses were 18,258+/-30, 16,492+/-24 and 17,363+/-17 Da, respectively. Two linker chains for HbGp were also observed at 25,817+/-50 and 26,761+/-16 Da, and this result is different from HbLt, where four linker chains were reported in the range 24-32 kDa. Finally, trimers (abc) were observed at 51-52 kDa. This partial characterization, performed for the first time, is an important step in the characterization of subunits of this giant extracellular hemoglobin.

Glowing Worms: Biological, Chemical, and Functional Diversity of Bioluminescent Annelids.

Bioluminescence, the ability to produce light by living organisms, has evolved independently in numerous lineages across the tree of life. Luminous forms are found in a wide range of taxonomic groups from bacteria to vertebrates, although the great majority of bioluminescent organisms are marine taxa. Within the phylum Annelida, bioluminescence is widespread, present in at least 98 terrestrial and marine species that represent 45 genera distributed in thirteen lineages of clitellates and polychaetes. The ecological diversity of luminous annelids is unparalleled, with species occupying a great variety of habitats including both terrestrial and marine ecosystems, from coastal waters to the deep-sea, in benthic and pelagic habitats from polar to tropical regions. This great taxonomic and ecological diversity is matched by the wide array of bioluminescent colors-including yellow light, which is very rare among marine taxa-different emission wavelengths even between species of the same genus, and varying patterns, chemical reactions and kinetics. This diversity of bioluminescence colors and patterns suggests that light production in annelids might be involved in a variety of different functions, including defensive mechanisms like sacrificial lures or aposematic signals, and intraspecific communication systems. In this review, we explore the world of luminous annelids, particularly focusing on the current knowledge regarding their taxonomic and ecological diversity and discussing the putative functions and chemistries of their bioluminescent systems.