Guillermo Ponz Segrelles

◂Fig. 6 Scanning electronmicroscopy images of Ramisyllis kingghidorahi n. sp. A Anterior region up to first 17 segments, dorsal view. B Prostomium in detail, anterodorsal view (broken antennae on stub). C Prostomium and first segments in detail showing dorsal bands of cilia, dorsal view. D–F Pores on dorsal cirri. Scale bars: 1 mm A, 200 µm B, 300 µm C, 50 µm E, 30 µm D, F

Fig. 14 Sexual dimorphism in stolons. A–E Female stolons, dorsal view. F–I Male stolons; arrows in F point to the first three segments, the only ones that contain sperm. G–I Stolons attached to the stalk, detail of pygidium in regeneration on the ventral side before detachment of the stolon (arrow in G), ventral view. H Light microscope image showing region of stolon head and pygidium regeneration, ventral view. I Stolon attached, dorsal view. Scale bars: 500 µm A, D, E, F, 100 µm B, G, H, and 200 µm C, I

Fig. 12 Scanning microscopy images of Ramisyllis kingghidorahi n. sp, parapodium and chaetae details. A–F, H Midbody tomahawk shaped chaetae. G Ventral cirri, arrows point to pores. Scale bars: 5 µm A, C 4 µm B, 20 µm D, 10 µm E, G, and 50 µm F, H

◂Fig. 8 Light microscope images of living specimens of Ramisyllis kingghidorahi n. sp. A Branching point. B, E–G Posterior ends showing pygidia. C, D, H, I Midbody segments in regions of long dorsal cirri. Arrows point to the ventral blood vessel in H and the digestive tract in I.A, D, E, and I in dorsal view. B, C, F and H in ventral view. G In lateral view. Scale bars: 500 µm A, E, 200 µm B, C, D, 100 µm F, H, I, and 50 µm G

Fig. 11 Light microscope images of living specimens of Ramisyllis kingghidorahi n. sp., dorsal cirri, parapodium and segmental septa. A–F Dorsal cirri and spiral glands; arrow points to spiral gland in C. G Midbody parapodium, arrow points to pointed acicula, lateral view. H–I Three intersegmental septa forming a "Y shape," dorsal view. Scale bars: 200 µm A, B, 50 µm C, F, G, H, I, 20 µm E, and 10 µm D

◂Fig. 10 Scanning electron microscopy images of Ramisyllis kingghidorahi n. sp., posterior-most regions and epithelium details. A–D Posterior ends. Arrow in C and D points to heavily ciliated anus. E– G Minute crests on the dorsal surface of midbody segments. Arrows point to crests laterally located on the dorsal surface. H Dorsal surface of posterior segments. I Clumps of cilia on dorsal surface of proventricular segments. Arrows pointing to pores in H. Scale bars: 100 µm A, B, I, 50 um C, G, 5 µm D, E,4 µm F, and 3 µm H

Fig. 7 Stereomicroscopy images of living specimens of Ramisyllis kingghidorahi n. sp. (A, C-H) and Ramisyllismulticaudata (B) for comparison. A Ramisylliskingghidorahi n. sp. Holotype. B R. multicaudata anterior region, dorsal view; picture modified from Ponz-Segrelles et al. (2021), with permission. C Prostomium and first segments in detail, dorsal view. D Anterolateral view of prostomium with details of palps and pharynx everted. E and F. Pharynx everted in ventral view. G Branching asymmetries in dorsal cirri. H Branching asymmetries in body shape. Scale bars: 1 mm A, B, 200 µm C, D, 100 µm E, F, 2 mm G, H

◂Fig. 9 Scanning electron microscopy images of branches of Ramisyllis kingghidorahi n. sp. A–F Midbody branching regions with segments of different morphologies, as long as wide with long dorsal cirri in A–C, much longer with short dorsal cirri in D, E and F Details of cirri alternation in length. A, C, E–F In dorsal view; B and D in ventral view. Scale bars: 200 µm A, C, 100 µm B, F, 400 µm D, and 500 µm E

◂Fig. 5 Ramisyllis kingghidorahi n. sp. and host sponge Petrosia sp. A Anterior region in dorsal view, prostomium faces down. B Fragment of one specimen. C-F–f Host sponges in their natural habitat. Scale bars: 2 mm A, B, 1 cm C, D and 5 mm E, F

◂Fig. 2 Maximum likelihood trees. A Tree obtained when analysing 18S data set. B Tree obtained when analysing 28S data set. C Tree obtained when analysing COI data set. D Tree obtained when analysing 16S data set. Bootstrap support values below nodes. Syllis and Typosyllis species as they were originally described

Additional file 3 Results obtained in the last day of observation (35 dpa). a–d, anterior regeneration. a'–d', posterior regeneration. Thicker dashed lines indicate the bisection point. Thinner dashed lines circumscribe the proventricle. Abbreviations: pr proventricle, ri rectal intestine. Scale bars: 200 μm.

Additional file 4 S-phase cell distribution and live observations and in regenerates, cutting level L2 + L3, end fragments. a'–h'. Edu (pulse-chase) BrdU (pulse) stainings. a–h. Anterior regeneration. a'–h'. Posterior regeneration. i'–r'. Light microscopy images of living specimens. i–r. Anterior regeneration. I′–R'. Posterior regeneration; arrowheads in Q' and R' point to the region with urinary concretions in the rectal intestine. Dashed lines circumscribe the shape of the animals. Scale bars: 100 μm (e, i–m, c', e'–g'), 200 μm (a–d, f–h, n–r, a', b', d', h'–r').

Additional file 2 EdU pulse cross-sections of posterior end in uncut specimen of S. malaquini. a. Total Z-projection of posterior end. b. Ventral section. c. Dorsal section. Abbreviations: vmc ventral midline S-phase cells, cic cirri S-phase cell. Scale bars: 100 μm.

Additional file 1 EdU pulse cross section and Z-projections of midbody in uncut specimens of S. malaquini. a. Ventral projection of pharynx region. B. Dorsal projection of pharynx region. c. Total projection of pharynx region. d. Ventral projection of proventricle region E. Dorsal projection of proventricle region F. Total projection of proventricle region. Abbreviations: vmc ventral midline S-phase cells, fc foregut S-phase cells. Scale bars: 100 μm.

Additional file 1. Results of functional annotation of the transcriptomes of Sphaerosyllis hystrix and Syllis gracilis. a Results against all metazoan database. b Results within Annelida. c Gene ontology distribution of the annotated genes grouped in the three main functional categories (cellular component, molecular function, and biological process). GO terms with percentage of genes > 4% were plotted.

Among over 20,000 species of Annelida, only two branching species with a highly modified body-pattern are known until now: the Syllidae Syllis ramosa McIntosh, 1879, and Ramisyllis multicaudata Glasby et al. (Zoological Journal of the Linnean Society, 164, 481–497, 2012). Both have unusual ramified bodies with one head and multiple branches and live inside the canals of host sponges. Using an integrative approach (combining morphology, internal anatomy, ecology, phylogeny, genetic divergence, and the complete mitochondrial genome), we describe a new branching species from Japan, Ramisyllis kingghidorahi n. sp., inhabiting an undescribed species of Petrosia (Porifera: Demospongiae) from shallow waters. We compare the new species with its closest relative, R. multicaudata; emend the diagnosis of Ramisyllis; and discuss previous reports of S. ramosa. This study suggests a much higher diversity of branching syllids than currently known. Finally, we discuss possible explanations for the ...

Background In syllids (Annelida, Syllidae), the regenerative blastema was subject of many studies in the mid and late XXth century. This work on syllid regeneration showed that the blastema is developed by a process of dedifferentiation of cells near the wound, followed by their proliferation and redifferentiation (cells differentiate to the original cell type) or, in some specific cases, transdifferentiation (cells differentiate to a cell type different from the original). Up to date, participation of stem cells or pre-existing proliferative cells in the blastema development has never been observed in syllids. This study provides the first comprehensive description of Syllis malaquini’s regenerative capacity, including data on the cellular proliferation dynamics by using an EdU/BrdU labelling approach, in order to trace proliferative cells (S-phase cells) present before and after operation. Results Syllis malaquini can restore the anterior and posterior body from different cutting ...

The sponge‐dwelling Syllidae Ramisyllis multicaudata and Syllis ramosa are the only annelid species for which a branched body with one head and multiple posterior ends is known. In these species, the head is located deep within the sponge, and the branches extend through the canal system of their host. The morphology of these creatures has captivated annelid biologists since they were first discovered in the late XIXth century, and their external characteristics have been well documented. However, how their branched bodies fit within their symbiotic host sponges and how branches translate into internal anatomy has not been documented before. These features are crucially relevant for understanding the body of these animals, and therefore, the aim of this study was to investigate these aspects. In order to assess these questions, live observation, as wells as histology, immunohistochemistry, micro‐computed tomography, and transmission electron microscopy techniques were used on specim...

A new species of Syllis Grube, 1850 (Syllidae, Annelida) from marine aquaria is described in this study, including information about its life cycle, laboratory cultures, transcriptomic data, and an updated phylogeny of the group. Syllis malaquini sp. nov. is diagnosed by a slender body with a colour pattern consisting of dorsal dark lines on each segment and a dark stain on the anterior region of the prostomium, blades of falciger compound chaetae bidentate, with proximal and distal teeth of similar length, short dorsal cirri with alternation in length in the anterior body, one bidentate ventral simple chaeta and one dorsal simple chaeta with a distal notch in posterior parapodia, and thin pointed aciculae. Additionally, we present an updated molecular phylogeny of Syllinae, which indicates that Syllis malaquini sp. nov. clusters with specimens of Typosyllis gerundensis (Alós & Campoy, 1981), Syllis hyalina Grube, 1863, and Syllis armillaris (Müller, 1776) from the Mediterranean Sea. The new species is maintained in aquaria and petri dish cultures in the laboratory, and its life cycle was observed and documented. Syllis malaquini sp. nov. reproduces sexually by schizogamy and asexually by fission. Furthermore, transcriptomic data of the new species is provided as a useful tool for further studies and comparative approaches. Syllis malaquini sp. nov. is an interesting organism to study reproduction and regeneration in syllids.

BackgroundAnnelids exhibit remarkable postembryonic developmental abilities. Most annelids grow during their whole life by adding segments through the action of a segment addition zone (SAZ) located in front of the pygidium. In addition, they show an outstanding ability to regenerate their bodies. Experimental evidence and field observations show that many annelids are able to regenerate their posterior bodies, while anterior regeneration is often limited or absent. Syllidae, for instance, usually show high abilities of posterior regeneration, although anterior regeneration varies across species. Some syllids are able to partially restore the anterior end, while others regenerate all lost anterior body after bisection. Here, we used comparative transcriptomics to detect changes in the gene expression profiles during anterior regeneration, posterior regeneration and regular growth of two syllid species:Sphaerosyllis hystrixandSyllis gracilis; which exhibit limited and complete anteri...

Although model species have proven to be crucial for developmental biology, the evo-devo approach requires a broader picture across phylogeny. Herein, we try to expand the range of studied annelids by presenting a transcriptome of Typosyllis antoni as a tool for the study of developmental and evolutionary processes in Syllidae. Moreover, we provide homologs of the stem-cell markers vasa, piwi, and nanos, and investigate their expression patterns in gamete-producing individuals for the first time in this group. We found no expression in females, while there is a distinct expression pattern in males. Based on this data, we argue that spermatogenesis starts in the gonads and finishes in the coelomic cavity, and it occurs simultaneously in a large number of segments. Surprisingly, no expression of the stem-cell markers was found in the segment addition zone of these reproducing animals (stolonizing). Preliminary explanations like a lack of growth during stolonization, or the absence of ...