Capitella Teleta Research Articles

Molecular cloning and expression of TLR in the Eisenia andrei earthworm

Toll-like receptors (TLRs) play an important role in defense responses to pathogens in invertebrates. Here we characterize the first TLR isolated from an oligochaete annelid, namely, Eisenia andrei (EaTLR) and show its expression pattern. The full-length EaTLR cDNA consists of 2615bp encoding a putative protein of 675 amino acids. The predicted amino acid sequence comprises of an extracellular domain containing 31 amino acid signal peptide and seven leucine-rich repeats (LRR), capped with cysteine-rich N- and C-terminal LRRs followed by a transmembrane domain and cytoplasmic Toll/IL-1R domain (TIR). TIR domains of twenty individual earthworms were sequenced and the variability suggesting the presence of a high number of TLR genes in the genome of E. andrei was observed. Phylogenetic analysis revealed the highest similarity of EaTLR with polychaete annelid, Capitella teleta and TLRs of mollusks and echinoderms. Finally, the highest constitutive expression of EaTLR was observed in the digestive tract. Gene expression was significantly increased in coelomocytes of E. andrei after the challenge with Gram-positive bacteria.

Effects of the pharmaceutical fluoxetine in spiked-sediments on feeding activity and growth of the polychaete Capitella teleta

The marine–estuarine polychaete Capitella is an indicator of organic pollution and plays important roles in sewage waste cycling. The antidepressant fluoxetine can be accumulated in streams and sewage effluents and it could pose a hazard to infauna. Effects of fluoxetine on feeding and growth of Capitella teleta were investigated through the exposure to 0, 0.001, 0.03, 0.3 and 3.3 μg/g dry weight sediment-spiked fluoxetine during 18 days. No effects of fluoxetine concentrations were observed on egestion rates, body weight and size-specific egestion rates. Fluoxetine favoured the occurrence of males with abnormal genital spines. This suggests that fluoxetine can have important reproductive implications. Further studies are recommended to assess potential detrimental effects on benthic infauna inhabiting close to sewage treatment plants.

Expression pattern of Piwi-like genes in adult Myzostoma cirriferum (Annelida)

Piwi-like genes are a subgroup of Argonaute genes which participate as gene regulators by gene silencing. In most bilaterians, such as mouse, human, insects, and zebrafish, their expression is mostly limited to gonadal stem cells. But there are some striking exceptions to this pattern; flatworms and acoels also express Piwi-like genes in somatic stem cells, due to their unique replacement system. Annelid species like Capitella teleta and Platynereis dumerilii express these genes in cells of the posterior growth zone as well as in gonadal stem cells. To investigate the expression pattern of Piwi-like genes in another annelid, we established in situ hybridization for adult Myzostoma cirriferum. Piwi-like gene transcripts recovered in an mRNA-seq library of pooled adult stages of M. cirriferum were expanded using RACE PCR, cloned and sequenced. ML analysis confirmed the identity of both transcripts as part of the Piwi1-like or Piwi2-like subfamily of Argonaute proteins. The results of in situ hybridization studies show that the expression of both Piwi-like genes, Mc-Piwi1 and Mc-Piwi2, is clearly located only in gonadal stem cells, and as such we did not find any evidence for the existence of a posterior growth zone nor expression in somatic stem cells.

An organizing activity is required for head patterning and cell fate specification in the polychaete annelid Capitella teleta: New insights into cell–cell signaling in Lophotrochozoa

Many lophotrochozoans (i.e., molluscs, annelids, nemerteans, and polyclad flatworms) display a well-conserved early developmental program called spiral cleavage that contrasts with the high diversity of adult body forms present in this group. Due to this stereotypical development, each cell can be uniquely identified and its lineage history known following intracellular injection of lineage tracers. Cell deletion experiments performed mainly in molluscs have demonstrated that one or two cells associated with the endomesodermal lineage represent an embryonic organizer of subsequent development and are causally involved in cell fate and body patterning. Utilizing the published fate map of the spiral-cleaving annelid Capitella teleta, we used infrared laser cell deletions to dissect the role of individual cells on the patterning of the larval body. Thirteen uniquely identifiable individual blastomeres and two double cell combination deletions were studied to assess larval phenotypes by scoring multiple morphological structures and cell type-specific molecular markers differentially expressed along the antero-posterior and dorso-ventral axes. Surprisingly, our results show that in C. teleta, the cellular identity of the “organizing cell” and the timing of the organizing activity are different from that of other spiralians. In C. teleta, the ectodermal primary somatoblast, 2d, is the key cell responsible for organizing activity during early embryonic development, and is necessary for bilateral symmetry and dorso-ventral axis organization of the head as well as neural, foregut and mesoderm tissue formation. Furthermore, we show that the ERK/MAPK signaling pathway does not appear to be involved in organizing activity in C. teleta. This contrasts with data from molluscs and the molecular mechanism suggested for another polychaete, Hydroides elegans, highlighting likely molecular level variation among spiralian embryos. These results reinforce the idea that an embryonic organizing activity is present across spiralians. Our data also emphasize the developmental variation within lophotrochozoans, and may ultimately provide insight into the role of developmental processes in the evolution of diverse body forms in metazoans.

Insights into bilaterian evolution from three spiralian genomes

Current genomic perspectives on animal diversity neglect two prominent phyla, the molluscs and annelids, that together account for nearly one-third of known marine species and are important both ecologically and as experimental systems in classical embryology1–3. Here we describe the draft genomes of the owl limpet (Lottia gigantea), a marine polychaete (Capitella teleta) and a freshwater leech (Helobdella robusta), and compare them with other animal genomes to investigate the origin and diversification of bilaterians from a genomic perspective. We find that the genome organization, gene structure and functional content of these species are more similar to those of some invertebrate deuterostome genomes (for example, amphioxus and sea urchin) than those of other protostomes that have been sequenced to date (flies, nematodes and flatworms). The conservation of these genomic features enables us to expand the inventory of genes present in the last common bilaterian ancestor, establish the tripartite diversification of bilaterians using multiple genomic characteristics and identify ancient conserved long- and short-range genetic linkages across metazoans. Superimposed on this broadly conserved pan-bilaterian background we find examples of lineage-specific genome evolution, including varying rates of rearrangement, intron gain and loss, expansions and contractions of gene families, and the evolution of clade-specific genes that produce the unique content of each genome.

Fate and effects of acetyl cedrene in sediments inhabited by different densities of the deposit feeder, Capitella teleta

Fragrance materials, such as acetyl cedrene (AC), are of environmental concern because they are continuously released to aquatic systems down the drain. In the present study, Capitella teleta (formerly Capitella capitata species I) was exposed to AC-amended sediment at two population densities corresponding to 44,000 and 88,000 worms/m(2). The fate of AC in systems with worms was compared to that in identical systems without worms. We examined the toxicity of AC on worm survival, growth, and feeding rate, and quantified the fate of AC in exposure systems by mass balance. Worm survival was close to 100% in all treatments. Acetyl cedrene had some positive effects on worm growth, but not feeding, whereas density had negative effects on both growth and feeding rates. After 14 d, the sediment concentration of AC was reduced by 88 to 99% in the presence of worms, whereas sediment AC concentration was reduced by 13 to 31% or less in the absence of worms. Acetyl cedrene was detected in fecal pellets, at low concentrations compared to the initial concentration in the sediment, but not in worm tissue, suggesting that ingested AC is bioavailable to Capitella teleta and that worms can biotransform sediment-associated AC effectively.

Evolution of selenoproteins in the metazoan

BackgroundThe selenocysteine (Sec) containing proteins, selenoproteins, are an important group of proteins present throughout all 3 kingdoms of life. With the rapid progression of selenoprotein research in the post-genomic era, application of bioinformatics methods to the identification of selenoproteins in newly sequenced species has become increasingly important. Although selenoproteins in human and other vertebrates have been investigated, studies of primitive invertebrate selenoproteomes are rarely reported outside of insects and nematodes.ResultA more integrated view of selenoprotein evolution was constructed using several representative species from different evolutionary eras. Using a SelGenAmic-based selenoprotein identification method, 178 selenoprotein genes were identified in 6 invertebrates: Amphimedon queenslandica, Trichoplax adhaerens, Nematostella vectensis, Lottia gigantean, Capitella teleta, and Branchiostoma floridae. Amphioxus was found to have the most abundant and variant selenoproteins of any animal currently characterized, including a special selenoprotein P (SelP) possessing 3 repeated Trx-like domains and Sec residues in the N-terminal and 2 Sec residues in the C-terminal. This gene structure suggests the existence of two different strategies for extension of Sec numbers in SelP for the preservation and transportation of selenium. In addition, novel eukaryotic AphC-like selenoproteins were identified in sponges.ConclusionComparison of various animal species suggests that even the most primitive animals possess a selenoproteome range and variety similar to humans. During evolutionary history, only a few new selenoproteins have emerged and few were lost. Furthermore, the massive loss of selenoproteins in nematodes and insects likely occurred independently in isolated partial evolutionary branches.

Effects of maternal investment on larvae and juveniles of the annelidCapitella teletadetermined by experimental reduction of embryo energy content

AbstractExperimental manipulations of the energy content of marine invertebrate embryos have been useful in testing key assumptions of life history theory, especially those concerning relationships between egg size, length of the planktonic period, and juvenile size and quality. However, methods for such “allometric engineering” experiments have been available for only a limited set of taxa (those with regulative early development, e.g., cnidarians and echinoderms). Here, we describe a method for the reduction of embryo energy content in the spirally cleaving embryos of a marine annelid,Capitella teleta, by targeted deletion of endodermal precursor cells. Embryos ofC. teletain which up to three cells (the macromeres 3A, 3B, and 3C) were deleted formed morphologically normal lecithotrophic larvae that were much smaller than larvae developing from control embryos. Experimental larvae metamorphosed at high rates, forming juveniles that were smaller than control juveniles. Juveniles derived from treated embryos had functional midguts, ingested and digested food, and grew into sexually mature adults. These results are consistent with those from previous allometric engineering studies of echinoid echinoderms, which suggest that in facultatively planktotrophic or lecithotrophic species, little maternally derived energy is used for construction of the larval body; instead, the majority is allocated to the formation of a large, high‐quality juvenile. Cleavage programs are highly conserved among divergent spiralian taxa (e.g., molluscs, nemerteans, and platyhelminths), so this method will likely be applicable to a diverse set of embryos. Similar experiments carried out in these diverse taxa will be extremely useful for evaluating inferences on relationships between egg size, length of the planktonic period, and juvenile size and quality previously based only on experiments on echinoid echinoderms.

Inhibitors of nitric oxide synthase induce larval settlement and metamorphosis of the polychaete annelid Capitella teleta

The neurotransmitter nitric oxide (NO) has been implicated in the inhibitory control of metamorphosis of some marine gastropods, echinoderms, and ascidians. We have explored whether or not metamorphosis of metatrochophore larvae of the polychaete annelid Capitella teleta is also regulated by NO. Immunohistochemical analysis revealed a bilateral group of three large nitric oxide synthase (NOS) immunoreactive cells that lie dorsal to the pharynx and extend ventral processes toward the pharynx in the region of the dorsal pharyngeal pad. Smaller NOS-immunoreactive cells were distributed widely throughout the body but concentrated in the prostomium and pygidium. Histological analysis for NO, using the NO detector diaminofluorescein-FM, showed that NO concentration was high in the larval midgut, although diffuse amounts of NO were detected throughout the body. Inhibitors of NOS, including s-methylisothiourea sulfate, aminoguanidine hemisulfate, 7-nitroindazole, and N-methyl-L-arginine all induced settlement and metamorphosis of the Capitella larvae in a concentration-dependent manner. The NO donor nitroprusside prevented the induction of settlement and metamorphosis induced by the NOS inhibitor N-methyl-L-arginine, but did not prevent settlement and metamorphosis induced by a marine sediment extract, exogenous serotonin, or by the serotonin reuptake inhibitor fluoxetine. Pre-incubating larvae with the serotonin receptor antagonist ketanserin also inhibited settlement and metamorphosis in response to NOS inhibitors. These results suggest that endogenous production of NO maintains the larval state in C. teleta, and that endogenous serotonin stimulates metamorphosis in a way similar to that described previously for larvae from other major invertebrate phyla.

Expression of the pair-rule gene homologs runt, Pax3/7, even-skipped-1 and even-skipped-2 during larval and juvenile development of the polychaete annelid Capitella teleta does not support a role in segmentation

BackgroundAnnelids and arthropods each possess a segmented body. Whether this similarity represents an evolutionary convergence or inheritance from a common segmented ancestor is the subject of ongoing investigation.MethodsTo investigate whether annelids and arthropods share molecular components that control segmentation, we isolated orthologs of the Drosophila melanogaster pair-rule genes, runt, paired (Pax3/7) and eve, from the polychaete annelid Capitella teleta and used whole mount in situ hybridization to characterize their expression patterns.ResultsWhen segments first appear, expression of the single C. teleta runt ortholog is only detected in the brain. Later, Ct-runt is expressed in the ventral nerve cord, foregut and hindgut. Analysis of Pax genes in the C. teleta genome reveals the presence of a single Pax3/7 ortholog. Ct-Pax3/7 is initially detected in the mid-body prior to segmentation, but is restricted to two longitudinal bands in the ventral ectoderm. Each of the two C. teleta eve orthologs has a unique and complex expression pattern, although there is partial overlap in several tissues. Prior to and during segment formation, Ct-eve1 and Ct-eve2 are both expressed in the bilaterial pair of mesoteloblasts, while Ct-eve1 is expressed in the descendant mesodermal band cells. At later stages, Ct-eve2 is expressed in the central and peripheral nervous system, and in mesoderm along the dorsal midline. In late stage larvae and adults, Ct-eve1 and Ct-eve2 are expressed in the posterior growth zone.ConclusionsC. teleta eve, Pax3/7 and runt homologs all have distinct expression patterns and share expression domains with homologs from other bilaterians. None of the pair-rule orthologs examined in C. teleta exhibit segmental or pair-rule stripes of expression in the ectoderm or mesoderm, consistent with an independent origin of segmentation between annelids and arthropods.

Somatic and germline expression of piwi during development and regeneration in the marine polychaete annelid Capitella teleta

BackgroundStem cells have a critical role during adult growth and regeneration. Germline stem cells are specialized stem cells that produce gametes during sexual reproduction. Capitella teleta (formerly Capitella sp. I) is a polychaete annelid that reproduces sexually, exhibits adult growth and regeneration, and thus, is a good model to study the relationship between somatic and germline stem cells.ResultsWe characterize expression of the two C. teleta orthologs of piwi, genes with roles in germline development in diverse organisms. Ct-piwi1 and Ct-piwi2 are expressed throughout the life cycle in a dynamic pattern that includes both somatic and germline cells, and show nearly identical expression patterns at all stages examined. Both genes are broadly expressed during embryonic and larval development, gradually becoming restricted to putative primordial germ cells (PGCs) and the posterior growth zone. In juveniles, Ct-piwi1 is expressed in the presumptive gonads, and in reproductive adults, it is detected in gonads and the posterior growth zone. In addition, Ct-piwi1 is expressed in a population of putative PGCs that persist in sexually mature adults, likely in a stem cell niche. Ct-piwi1 is expressed in regenerating tissue, and once segments differentiate, it becomes most prominent in the posterior growth zone and immature oocytes in regenerating ovaries of regenerating segments.ConclusionsIn C. teleta, piwi genes may have retained an ancestral role as genetic regulators of both somatic and germline stem cells. It is likely that piwi genes, and associated stem cell co-regulators, became restricted to the germline in some taxa during the course of evolution.

Interpreting toxicity data in a DEB framework: A case study for nonylphenol in the marine polychaete Capitella teleta

Dynamic Energy Budget (DEB) theory provides a powerful framework for interpreting toxicity data, but is not broadly applied in ecotoxicology yet. One of the reasons is the fact that estimation of DEB parameters from experimental data is certainly not a trivial affair. Almost every data analysis raises new questions, which require the formulation of specific mechanistic hypotheses. These hypotheses should be translated into model adaptations, which can subsequently be tested on the data set. In this paper, we demonstrate this procedure by analyzing a case study for ecotoxicity within the DEB framework. The case study we selected is a previously published data set for 4-n-nonylphenol in the polychaete worm Capitella teleta (formerly Capitella sp. I). Particular aspects of interest in this study are an apparent slow initial growth, and low-dose stimulation (hormesis) of growth and reproduction. In this publication, we explicitly discuss our deviations from the standard DEB model in terms of the underlying hypotheses, the existence of alternative hypotheses to explain the data, and how limited additional experiments can be designed to decide between alternative explanations.

Neuropeptide evolution: Neurohormones and neuropeptides predicted from the genomes of Capitella teleta and Helobdella robusta

Genes encoding neurohormones and neuropeptide precursors were identified in the genomes of two annelids, the leech Helobdella robusta and the polychaete worm Capitella teleta. Although no neuropeptides have been identified from these two species and relatively few neuropeptides from annelids in general, 43 and 35 such genes were found in Capitella and Helobdella, respectively. The predicted peptidomes of these two species are similar to one another and also similar to those of mollusks, particular in the case of Capitella. Helobdella seems to have less neuropeptide genes than Capitella and it lacks the glycoprotein hormones bursicon and GPA2/GPB5; in both cases the genes coding the two subunits as well as the genes coding their receptors are absent from its genome. In Helobdella several neuropeptide genes are duplicated, thus it has five NPY genes, including one pseudogene, as well as four genes coding Wwamides (allatostatin B). Genes coding achatin, allatotropin, allatostatin C, conopressin, FFamide, FLamide, FMRFamide, GGRFamide, GnRH, myomodulin, NPY, pedal peptides, RGWamide (a likely APGWamide homolog), RXDLamide, VR(F/I)amide, WWamide were found in both species, while genes coding cerebrin, elevenin, GGNG, LFRWamide, LRFYamide, luqin, lymnokinin and tachykinin were only found in Capitella.

Flanking genes of an essential gene give information about the evolution of metazoa

We collected as much information as possible on new lamin genes and their flanking genes. The number of lamin genes varies from 1 to 4 depending more or less on the phylogenetic position of the species. Strong genome drift is recognised by fewer and unusually placed introns and a change in flanking genes. This applies to the nematode Caenorhabditis elegans, the insect Drosophila melanogaster, the urochordate Ciona intestinalis, the annelid Capitella teleta and the planaria Schmidtea mediterranea. In contrast stable genomes show astonishing conservation of the flanking genes. These are identical in the sea anemone Nematostella vectensis and the cephalochordate Branchiostoma floridae lamin B1 gene. Even in the lamin B1 genes from Xenopus tropicalis and man one of the flanking genes is conserved. Finally our analysis forms the basis for a molecular analysis of metazoan phylogeny.

Developmental expression of COE across the Metazoa supports a conserved role in neuronal cell-type specification and mesodermal development

The transcription factor COE (collier/olfactory-1/early B cell factor) is an unusual basic helix–loop–helix transcription factor as it lacks a basic domain and is maintained as a single copy gene in the genomes of all currently analysed non-vertebrate Metazoan genomes. Given the unique features of the COE gene, its proposed ancestral role in the specification of chemosensory neurons and the wealth of functional data from vertebrates and Drosophila, the evolutionary history of the COE gene can be readily investigated. We have examined the ways in which COE expression has diversified among the Metazoa by analysing its expression from representatives of four disparate invertebrate phyla: Ctenophora (Mnemiopsis leidyi); Mollusca (Haliotis asinina); Annelida (Capitella teleta and Chaetopterus) and Echinodermata (Strongylocentrotus purpuratus). In addition, we have studied COE function with knockdown experiments in S. purpuratus, which indicate that COE is likely to be involved in repressing serotonergic cell fate in the apical ganglion of dipleurula larvae. These analyses suggest that COE has played an important role in the evolution of ectodermally derived tissues (likely primarily nervous tissues) and mesodermally derived tissues. Our results provide a broad evolutionary foundation from which further studies aimed at the functional characterisation and evolution of COE can be investigated.Electronic supplementary materialThe online version of this article (doi:10.1007/s00427-010-0343-3) contains supplementary material, which is available to authorized users.

Expression and phylogenetic analysis of the zic gene family in the evolution and development of metazoans

Backgroundzic genes are members of the gli/glis/nkl/zic super-family of C2H2 zinc finger (ZF) transcription factors. Homologs of the zic family have been implicated in patterning neural and mesodermal tissues in bilaterians. Prior to this study, the origin of the metazoan zic gene family was unknown and expression of zic gene homologs during the development of early branching metazoans had not been investigated.ResultsPhylogenetic analyses of novel zic candidate genes identified a definitive zic homolog in the placozoan Trichoplax adhaerens, two gli/glis/nkl-like genes in the ctenophore Mnemiopsis leidyi, confirmed the presence of three gli/glis/nkl-like genes in Porifera, and confirmed the five previously identified zic genes in the cnidarian Nematostella vectensis. In the cnidarian N. vectensis, zic homologs are expressed in ectoderm and the gastrodermis (a bifunctional endomesoderm), in presumptive and developing tentacles, and in oral and sensory apical tuft ectoderm. The Capitella teleta zic homolog (Ct-zic) is detectable in a subset of the developing nervous system, the foregut, and the mesoderm associated with the segmentally repeated chaetae. Lastly, expression of gli and glis homologs in Mnemiopsis. leidyi is detected exclusively in neural cells in floor of the apical organ.ConclusionsBased on our analyses, we propose that the zic gene family arose in the common ancestor of the Placozoa, Cnidaria and Bilateria from a gli/glis/nkl-like gene and that both ZOC and ZF-NC domains evolved prior to cnidarian-bilaterian divergence. We also conclude that zic expression in neural ectoderm and developing neurons is pervasive throughout the Metazoa and likely evolved from neural expression of an ancestral gli/glis/nkl/zic gene. zic expression in bilaterian mesoderm may be related to the expression in the gastrodermis of a cnidarian-bilaterian common ancestor.

Ecdysone receptor homologs from mollusks, leeches and a polychaete worm

The genomes of the mollusk Lottia gigantea, the leech Helobdella robusta and the polychaete worm Capitella teleta each have a gene encoding an ecdysone receptor homolog. Publicly available genomic and EST sequences also contain evidence for ecdysone receptors in the seahare Aplysia californica, the bobtail squid Euprymna scolopes and the medicinal leech Hirudo medicinalis. Three-dimensional models of the ligand binding domains of these predicted ecdysone receptor homologs suggest that each of them could potentially bind an ecdysone-related steroid. Thus, ecdysone receptors are not limited to arthropods and nematodes.

A comprehensive fate map by intracellular injection of identified blastomeres in the marine polychaete Capitella teleta

BackgroundThe polychaete annelid Capitella teleta (formerly Capitella sp. I) develops by spiral cleavage and has been the focus of several recent developmental studies aided by a fully sequenced genome. Fate mapping in polychaetes has lagged behind other spiralian taxa, because of technical limitations.ResultsTo generate a modern fate map for C. teleta, we injected 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate (DiI) into individual identified blastomeres through fourth-quartet micromere formation. Confocal laser scanning microscopy at single-cell resolution was used to characterize blastomere fates during larval stages. Our results corroborate previous observations from classic studies, and show a number of similarities with other spiralian fate maps, including unique and stereotypic fates for individual blastomeres, presence of four discrete body domains arising from the A, B, C and D cell quadrants, generation of anterior ectoderm from first quartet micromeres, and contributions to trunk ectoderm and ventral nerve cord by the 2d somatoblast. Of particular interest are several instances in which the C. teleta fate map deviates from other spiralian fate maps. For example, we identified four to seven distinct origins of mesoderm, all ectomesodermal. In addition, the left and right mesodermal bands arise from 3d and 3c, respectively, whereas 4d generates a small number of trunk muscle cells, the primordial germ cells and the anus. We identified a complex set of blastomere contributions to the posterior gut in C. teleta, which establishes the most complete map of posterior gut territories to date.ConclusionsOur detailed cellular descriptions reveal previously underappreciated complexity in the ontogenetic contributions to several spiralian larval tissues, including the mesoderm, nervous system and gut. The formation of the mesodermal bands by 3c and 3d is in stark contrast to other spiralians, in which 4d generates the mesodermal bands. The results of this study provide a framework for future phylogenetic comparisons and functional analyses of cell-fate specification.

Cell Lineage and Fate Map of the Primary Somatoblast of the Polychaete Annelid Capitella teleta

Like most polychaete annelids, Capitella teleta (formerly Capitella sp. I) exhibits a highly stereotypic program of early development known as spiral cleavage. Animals with spiral cleavage have diverse body plans, and homologous embryonic cells can be readily identified among distantly related animals. Spiralian embryos are particularly amenable to studies of fate-mapping, and larval fates of identified cells are conserved among diverse taxa. One cell of particular importance in spiralian development is 2d, or the primary somatoblast, which generates ectoderm of the body posterior to the prototroch. We are interested in the evolution of the primary somatoblast, and thus far, the 2d sublineage has only been analyzed in a few species. In Capitella teleta, 2d generates ectoderm of the segmented trunk and post-segmental pygidium. In this study, development of the 2d lineage was characterized in detail through intracellular injections of DiI, and time-lapse as well as confocal microscopy to analyze cleavage patterns and the fates of larval cells. Analysis of cleavage patterns reveals that the first bilateral division in the 2d sublineage occurs with the division of 2d¹¹², the same 2d daughter cell that first divides bilaterally in the polychaete Platynereis dumerilii. Larval fates of blastomeres 2d¹, 2d², 2d¹¹, 2d¹², 2d¹¹², 2d¹¹²¹, and 2d¹¹²² were determined. All cells show stereotypic descendant clones that are consistent with segregation within sublineages. In the first few divisions of the 2d sublineage, larval-specific structures (neurotroch and telotroch) and pygidial ectoderm are segregated from segmental ectoderm and ventral nerve cord. The daughters of the first bilateral division, 2d¹¹²¹ and 2d¹¹²², generate the right and left halves of the segmental ectoderm and ventral nerve cord respectively, although the clones are consistently asymmetric across the dorsal midline. The pattern of cleavage divisions and the fates of the 2d daughters in Capitella teleta are compared to those in other spiralians with special attention to annelids.

Lineage analysis of ectoderm and nervous system in the polychaete annelid Capitella teleta

Lineage analysis of ectoderm and nervous system in the polychaete annelid Capitella teleta