Ciliary Field Research Articles

Dimorphilus gyrociliatus (Annelida: Dinophiliformia) Dwarf Male Nervous System Represents a Common Pattern for Lophotrochozoa.

Dinophiliformia is a newly revealed clade within Annelida that is a sister group to Pleistoannelida. Dimorphilus gyrociliatus is a representative of this clade that has fascinated scientists with its high degree of sexual dimorphism. Both males and females are small, worm-like creatures that have specific ciliary structures: anterior ventral, posterior ventral, and dorsal ciliary fields in males, and prototroch, metatroch, and ventral ciliary fields in females. There are data on the morphology and development of the nervous system in Oweniidae, Sipunculida, Pleistoannelida, and even Dinophiliformia. However, data on the neuromorphology and development of D. gyrociliatus dwarf males are limited. Here, we present data on the distribution of cilia, sensory neurons, and the 5-HT-like immunoreactive system in 3D reconstructions and cross-sections. Immunochemical labeling with anti-acetylated tubulin and anti-5-HT antibodies and confocal microscopy were used to visualize the ciliary structures and neurons. The male has three ciliary fields: anterior ventral, posterior ventral, and dorsal. These include frontal ganglia, five commissures, two ventral and two dorsal bundles, and penial nerves. A total of fifty-seven neurons and only five 5-HT-like immunoreactive cells were described. Although the sensory neurons were not 5-HT-like immunoreactive, they had 5-HT innervation, which may indicate the role of 5-HT in perception. There may be homology between male and female ciliary structures. The dwarf male of D. gyrociliatus may have a reduced apical organ consisting of two sensory neurons and a 5-HT-like immunoreactive cell.

Ciliated epithelia are key elements in the recruitment of bacterial partners in the squid-vibrio symbiosis.

The Hawaiian bobtail squid, Euprymna scolopes, harvests its luminous symbiont, Vibrio fischeri, from the surrounding seawater within hours of hatching. During embryogenesis, the host animal develops a nascent light organ with ciliated fields on each lateral surface. We hypothesized that these fields function to increase the efficiency of symbiont colonization of host tissues. Within minutes of hatching from the egg, the host's ciliated fields shed copious amounts of mucus in a non-specific response to bacterial surface molecules, specifically peptidoglycan (PGN), from the bacterioplankton in the surrounding seawater. Experimental manipulation of the system provided evidence that nitric oxide in the mucus drives an increase in ciliary beat frequency (CBF), and exposure to even small numbers of V. fischeri cells for short periods resulted in an additional increase in CBF. These results indicate that the light-organ ciliated fields respond specifically, sensitively, and rapidly, to the presence of nonspecific PGN as well as symbiont cells in the ambient seawater. Notably, the study provides the first evidence that this induction of an increase in CBF occurs as part of a thus far undiscovered initial phase in colonization of the squid host by its symbiont, i.e., host recognition of V. fischeri cues in the environment within minutes. Using a biophysics-based mathematical analysis, we showed that this rapid induction of increased CBF, while accelerating bacterial advection, is unlikely to be signaled by V. fischeri cells interacting directly with the organ surface. These overall changes in CBF were shown to significantly impact the efficiency of V. fischeri colonization of the host organ. Further, once V. fischeri has fully colonized the host tissues, i.e., about 12-24h after initial host-symbiont interactions, the symbionts drove an attenuation of mucus shedding from the ciliated fields, concomitant with an attenuation of the CBF. Taken together, these findings offer a window into the very first interactions of ciliated surfaces with their coevolved microbial partners.

A peptidoglycan-recognition protein orchestrates the first steps of symbiont recruitment in the squid-vibrio symbiosis.

In symbioses established through horizontal transmission, evolution has selected for mechanisms that promote the recruitment of symbionts from the environment. Using the binary association between the Hawaiian bobtail squid, Euprymna scolopes, and its symbiont, Vibrio fischeri, we explored the first step of symbiont enrichment around sites where V. fischeri cells will enter host tissues. Earlier studies of the system had shown that, within minutes of hatching in natural seawater, ciliated epithelia of the nascent symbiotic tissue secrete a layer of mucus in response to exposure to the cell-wall biomolecule peptidoglycan (PGN) from non-specific bacterioplankton. We hypothesized that a peptidoglycan recognition protein, EsPGRP4, is the receptor that mediates host mucus secretion by sensing the environmental PGN; earlier studies of this protein family had shown that this is the only member predicted to behave as a membrane receptor. Immunocytochemistry localized EsPGRP4 to the superficial ciliated fields of the juvenile organ. We found that production of EsPGRP4 increased over the first 48 h after hatching if the light organ remained uncolonized. When colonized by V. fischeri, the levels of the protein in light-organ tissue remained similar to that of hatchling organs. Pharmacologically curing the initially colonized light organ with antibiotics resulted in return of EsPGRP4 production to levels similar to light organs that had remained uncolonized since hatching. Furthermore, we found that preincubation of the tissues with an EsPGRP4 antibody decreased light organ mucus production and colonization. These findings provide evidence of an innate mechanism that underlies a crucial first step in the horizontal recruitment of bacterial symbionts.

Taxonomy and Phylogeny of Two Tintinnid Ciliates of Leprotintinnus (Protista, Ciliophora, Choreotrichida) Combining the Loricae, Cytological, Ontogenetic Features, and Barcoding Genes

Tintinnid ciliates are a highly diverse and essential group in the marine planktonic microbial loop. However, most of the known tintinnids were recorded only by the lorica characters and very few of them had been studied on their cytological features. In this study, the morphological characters of the lorica, ciliary pattern, nuclear apparatus, ontogenesis, and the molecular phylogeny of two poorly known tintinnid ciliates,Leprotintinnus nordqvisti(Brandt, 1906)Kofoid and Campbell (1929)andL. simplexSchmidt (1902), isolated from coastal waters of southern China, were investigated based on living observation, silver staining, three nuclear ribosomal DNA markers (18S, ITS1-5.8S-ITS2, and 28S genes) and one mitochondrial DNA marker (CO1gene). For the first time, the somatic ciliary pattern of the genusLeprotintinnuswas disclosed,viz., comprising a ventral, a dorsal, and a posterior kinety as well as a right, a left, and a lateral ciliary field. The diagnoses of bothLeprotintinnusspecies were improved and the neotype was assigned. The ontogenesis ofL. nordqvistiwas in enantiotropic division mode with the new dorsal and posterior kineties generatedde novo. The molecular phylogeny confirmed thatLeprotintinnusspecies are closely related to some species ofTintinnopsis,Stylicauda,Rhizodomus, andClimacocylis. The anterior extending of the ventral kinety together with some of the lateral kinety is likely to be a distinguishing feature to determine their systematic relationships. This study also revealed that (i) the lorica ofL. nordqvistiis polymorphic or plastic; (ii)Leprotintinnus tubulosusRoxas (1941)might be a synonym ofL.nordqvisti; (iii)Leprotintinnus neriticussensuYoo et al. (1988)might be a misidentification ofL. simplex.

An extraordinary new fluvial bdelloid rotifer, Coronistomus impossibilis gen. nov., sp. nov., with adaptations for turbulent flow (Rotifera: Bdelloidea: Coronistomidae fam. nov.)

A new bdelloid rotifer, Coronistomus impossibilis gen. nov., sp. nov. is described from the Hawlings River in Maryland, USA. The new species is a non-swimming sediment dweller that exceeds 550 µm in body length. Its corona is a weakly bilobed ciliated field on the ventral side of the head with lateral borders continuing into mouth. The species has ramate trophi that have on each half three widely spaced major teeth with two interproximal teeth. The foot lacks spurs and ends with a pair of long, thick ventral toes and a medially positioned caudal appendage. The new species lives in microhabitats exposed to turbulent flow and its morphological idiosyncrasies are interpreted as adaptations to reduce the likelihood of getting dislodged by the water. Although the corona morphology and the caudal appendage of the new species are similar to the corresponding traits of some of the species in the family Philodinavidae, the structure of its nonprotrusible trophi and its possession of only two toes (as opposed to four) separate it from all other members of the Philodinavidae. Therefore, a new family, Coronistomidae fam. nov., is erected for the new genus Coronistomus.

Three redescriptions in Tintinnopsis (Protista: Ciliophora: Tintinnina) from coastal waters of China, with cytology and phylogenetic analyses based on ribosomal RNA genes

BackgroundThe taxonomy of tintinnine ciliates is vastly unresolved because it has traditionally been based on the lorica (a secreted shell) and it has only recently incorporated cytological and molecular information. Tintinnopsis, the most speciose tintinnine genus, is also the most problematic: it is known to be non-monophyletic, but it cannot be revised until more of its species are studied with modern methods.ResultsHere, T. hemispiralis Yin, 1956, T. kiaochowensis Yin, 1956, and T. uruguayensis Balech, 1948, from coastal waters of China, were studied. Lorica and cell features were morphometrically investigated in living and protargol-stained specimens, and sequences of three ribosomal RNA (rRNA) loci were phylogenetically analyzed. The three species show a complex ciliary pattern (with ventral, dorsal, and posterior kineties and right, left, and lateral ciliary fields), but differ in lorica morphology, details of the somatic ciliature and rRNA gene sequences. Tintinnopsis hemispiralis is further distinguished by a ciliary tuft (a ribbon of very long cilia originated from the middle portion of the ventral kinety and extending out of the lorica) and multiple macronuclear nodules. Both T. kiaochowensis and T. uruguayensis have two macronuclear nodules, but differ in the number of somatic kineties and the position of the posterior kinety. Two neotypes are fixed for T. hemispiralis and T. kiaochowensis to stabilize the species names objectively, mainly because of the previous unavailability of type materials. By phylogenetic analysis and comparison with closely-related species, we infer that the ciliary tuft and details such as the commencement of the rightmost kinety in the lateral ciliary field are synapomorphies that may help clarify the systematics of Tintinnopsis-like taxa.ConclusionThe redescriptions of three poorly known Tintinnopsis species, namely T. hemispiralis, T. kiaochowensis, and T. uruguayensis firstly revealed their ciliary patterns and rRNA sequences. This study expands knowledge and database of tintinnines and helps in identifying potential synapomorphies for future taxonomic rearrangements.

The type species of Amphorellopsis and Tintinnopsis (Protozoa:Ciliophora): A new ciliary pattern and some comments in Tintinnina

BackgroundAs dominant components of planktonic microeukaryotes, the tintinnine ciliates act as a trophic link between microbial food web and traditional planktonic food chain in aquatic ecosystems. However, traditionally the taxonomy and systematics of tintinnines have been based on the lorica. It is now accepted that lorica features alone are insufficient and that cytological and molecular information are also needed. The systematics of the genera Tintinnopsis and Amphorellopsis is ambiguous, mainly due to the lack of ciliary and molecular information on their type species, T. beroidea and A. acuta. ResultIn the present study, specimens of both species were collected from coastal waters of Qingdao, China. The morphology of each was investigated based on observations of live and protargol-stained specimens, and their SSU rDNA- and LSU rDNA-based phylogenies were analyzed. Tintinnopsis beroidea presents the genus-typical ciliature. The somatic kineties in Amphorellopsis acuta were found to be evenly distributed without differentiation into distinct ciliary fields. The phylogenetic analyses revealed that Tintinnopsis is non-monophyletic, and that T. beroidea has a close relationship with T. nana and T. baltica. The monophyly of Amphorellopsis is also not supported by SSU rDNA analysis. ConclusionThis study first reveals the ciliary pattern and two nuclear rRNA gene sequences of two tintinnine type species, and thus expands knowledge and database of tintinnines. Amphorellopsis represents an intermediate lineage between tintinnines (loricate form) and aloricate choreotrichids.

Genes with evidence of positive selection as potentially related to coloniality and the evolution of morphological features among the lophophorates and entoprocts.

Evolutionary mechanisms that underlie the origins of coloniality among organisms are diverse. Some animal colonies may be comprised strictly of clonal individuals formed from asexual budding or comprised of a chimera of clonal and sexually produced individuals that fuse secondarily. This investigation focuses on select members of the lophophorates and entoprocts whose evolutionary relationships remain enigmatic even in the age of genomics. Using transcriptomic data sets, two coloniality-based hypotheses are tested in a phylogenetic context to find candidate genes showing evidence of positive selection and potentially convergent molecular signatures among solitary species and taxa-forming colonies from aggregate groups or clonal budding. Approximately 22% of the 387 orthogroups tested showed evidence of positive selection in at least one of the three branch-site tests (CODEML, BUSTED, and aBSREL). Only 12 genes could be reliably associated with a developmental function related to traits linked with coloniality, neuroanatomy, or ciliary fields. Genes testing for both positive selection and convergent molecular characters include orthologues of Radial spoke head, Elongation translation initiation factors, SEC13, and Immediate early response gene5. Maximum likelihood analyses included here resulted in tree topologies typical of other phylogenetic investigations based on wider genomic information. Further genomic and experimental evidence will be needed to resolve whether a solitary ancestor with multiciliated cells that formed aggregate groups gave rise to colonial forms in bryozoans (and perhaps the entoprocts) or that the morphological differences exhibited by phoronids and brachiopods represent trait modifications from a colonial ancestor.

Morphological and molecular phylogeny of the polycytopharyngeal ciliate Pycnothrix monocystoides Schubotz, 1908

We reinvestigated Pycnothrix monocystoides Schubotz, 1908 from the intestine of the African Rock Hyrax (Procavia capensis) collected from Saudi Arabia, using protargol impregnation and electron microscopy. Pycnothrix is a unique, up to 5 mm long intestinal ciliate with about two million cilia and many cytostomes (i.e. actual cytostome plus cytopharynx; polycytopharyngy) in the oral furrow (∼vestibulum) that extends on both sides of the cell. Both walls of the furrow are covered by adoral membranelle-like ciliary polymerizations. To the right of the furrow and the cytostomes there are small ciliary fields, very likely homologous to the “dorsal brush” found in free-living litostomateans. The molecular investigations show Pycnothrix as sister to Balantidium and endemic Australian intestinal ciliates, e.g. the genus Bandia. We propose that the common ancestor had both an oral furrow and a special ciliary field both similar to that found in Balantidium. The unique morphology (polycytopharyngy) and the rather distinct molecular separation suggest maintenance of the family status given by Poche (1913).

Neuronal coordination of motile cilia in locomotion and feeding.

Efficient ciliary locomotion and transport require the coordination of motile cilia. Short-range coordination of ciliary beats can occur by biophysical mechanisms. Long-range coordination across large or disjointed ciliated fields often requires nervous system control and innervation of ciliated cells by ciliomotor neurons. The neuronal control of cilia is best understood in invertebrate ciliated microswimmers, but similar mechanisms may operate in the vertebrate body. Here, we review how the study of aquatic invertebrates contributed to our understanding of the neuronal control of cilia. We summarize the anatomy of ciliomotor systems and the physiological mechanisms that can alter ciliary activity. We also discuss the most well-characterized ciliomotor system, that of the larval annelid Platynereis. Here, pacemaker neurons drive the rhythmic activation of cholinergic and serotonergic ciliomotor neurons to induce ciliary arrests and beating. The Platynereis ciliomotor neurons form a distinct part of the larval nervous system. Similar ciliomotor systems likely operate in other ciliated larvae, such as mollusc veligers. We discuss the possible ancestry and conservation of ciliomotor circuits and highlight how comparative experimental approaches could contribute to a better understanding of the evolution and function of ciliary systems.This article is part of the Theo Murphy meeting issue ‘Unity and diversity of cilia in locomotion and transport’.

Redescriptions of three tintinnine ciliates (Ciliophora: Tintinnina) from coastal waters in China based on lorica features, cell morphology, and rDNA sequence data

Three species of tintinnines, namely Tintinnopsis tentaculata Nie and Cheng, 1947, Tintinnopsis orientalis Kofoid and Campbell, 1929, and Eutintinnus lususundae (Entz, 1885) Kofoid and Campbell, 1939, were isolated from coastal waters of China. The morphology of each was investigated based on observations of live and protargol-stained specimens, and their SSU rDNA- and LSU rDNA-based phylogenetic relationships were analyzed. The ciliary patterns of these species are revealed for the first time. Based on the original descriptions and data from the present study, an improved diagnosis is given for each species. Unlike its congeners, the second dorsal kinety of Eutintinnus lususundae is displaced below the left ciliary field, which may suggest that the second dorsal kinety is evolving into a posterior kinety by a migration process. The ventral kinety in Eutintinnus is redefined. A neotype is fixed for T. tentaculata to stabilize the species name objectively, mainly because of the unavailability of type material.

Development and morphology of ciliary urns in the sea cucumber Synaptula hydriformis (Echinodermata: Holothuroidea)

AbstractSea cucumbers (holothuroids) lack the only known echinoderm immune organ, the axial organ. Holothuroids of the families Synaptidae and Chiridotidae have coelomic organs, known as ciliary urns, that gather and excrete waste and, therefore, might function in immunity. Although ciliary urns are widely reported and illustrated in the literature, the process and histology of urn development remain unknown. Development and structure of ciliary urns were examined in Synaptula hydriformis using scanning electron, brightfield, and scanning laser confocal microscopy. Mature urns occurred on all three mesenteries in 10‐tentacled young and later growth stages, and developing urns were found in post‐pentactulae, 10‐tentacled young, and released juveniles. Developing urns were circular clusters of ciliated collar cells protruding from the mesentery. The cells increased in number to form the sessile cushion stage with a shallow lumen. The subsequent spoon‐shaped stage had a stalk and a deepened lumen with an extensive ciliary field where coelomocytes began to accumulate. Mature urns had a thin stalk and cornucopia‐shaped body with an abluminal epithelium of squamous cells and an adluminal epithelium of densely packed ciliated collar cells. Cell boundaries of the rim of mature urns and of the stalk and body of developing urns were outlined on one or both sides by microvilli and an elevated cell membrane. Ciliary urns resembling the cushion‐stage urns of S. hydriformis have been described in the sea star Archaster typicus. If urns in these groups are homologous, it is likely that cushion urns are plesiomorphic and that they are present and have been overlooked in other echinoderms.

The neuroanatomy of the siboglinid Riftia pachyptila highlights sedentarian annelid nervous system evolution.

Tracing the evolution of the siboglinid group, peculiar group of marine gutless annelids, requires the detailed study of the fragmentarily explored central nervous system of vestimentiferans and other siboglinids. 3D reconstructions of the neuroanatomy of Riftia revealed that the “brain” of adult vestimentiferans is a fusion product of the supraesophageal and subesophageal ganglia. The supraesophageal ganglion-like area contains the following neural structures that are homologous to the annelid elements: the peripheral perikarya of the brain lobes, two main transverse commissures, mushroom-like structures, commissural cell cluster, and the circumesophageal connectives with two roots which give rise to the palp neurites. Three pairs of giant perikarya are located in the supraesophageal ganglion, giving rise to the paired giant axons. The circumesophageal connectives run to the VNC. The subesophageal ganglion-like area contains a tripartite ventral aggregation of perikarya (= the postoral ganglion of the VNC) interconnected by the subenteral commissure. The paired VNC is intraepidermal, not ganglionated over most of its length, associated with the ciliary field, and comprises the giant axons. The pairs of VNC and the giant axons fuse posteriorly. Within siboglinids, the vestimentiferans are distinguished by a large and considerably differentiated brain. This reflects the derived development of the tentacle crown. The tentacles of vestimentiferans are homologous to the annelid palps based on their innervation from the dorsal and ventral roots of the circumesophageal connectives. Neuroanatomy of the vestimentiferan brains is close to the brains of Cirratuliiformia and Spionida/Sabellida, which have several transverse commissures, specific position of the giant somata (if any), and palp nerve roots (if any). The palps and palp neurite roots originally developed in all main annelid clades (basally branching, errantian and sedentarian annelids), show the greatest diversity in their number in sedentarian species. Over the course of evolution of Sedentaria, the number of palps and their nerve roots either dramatically increased (as in vestimentiferan siboglinids) or were lost.

Redescription of Tintinnopsis everta Kofoid and Campbell 1929 (Alveolata, Ciliophora, Tintinnina) Based on Taxonomic and Genetic Analyses-Discovery of a New Complex Ciliary Pattern.

The about 1,000 species of tintinnid ciliates are identified and classified almost exclusively based on their lorica features, although the shortcomings of this structure are well‐known, e.g. causing uncertain species limitations and nonmonophyletic taxa. Hence, the present redescription of Tintinnopsis everta Kofoid and Campbell, 1929 considers not only the lorica characteristics, but focuses on cell and genetic features. The species is redescribed from the North Atlantic and adjacent sea areas, namely the east coast of the USA, using live observation, protargol‐stained material, scanning electron microscopy, and genetic analyses. The main stages of cell division are described, and the species’ phylogenetic relationships are inferred from morphological data and the small subunit ribosomal RNA gene sequence. The estimates of its biogeographical distribution and autecology are based on a literature survey. The species is characterised by a complex somatic ciliary pattern with a unique position of the posterior kinety and a conspicuously large distance between the somatic ciliary fields and the collar membranelles. The phylogenetic relationships of Tintinnopsis everta vary in the molecular trees depending on the algorithms used and are, therefore, regarded as unresolved. Nevertheless, the new kind of complex somatic ciliary pattern distinctly contributes to a better understanding of the tintinnid biodiversity and evolution and provides features for a future split of the nonmonophyletic genus Tintinnopsis.

A new species of Raricirrus (Polychaeta, Ctenodrilidae) from the continental slope of the Laptev Sea near the Gakkel Ridge

Raricirrus arcticus sp. nov. is described with specimens collected near the Gakkel Ridge, Laptev Sea, from one station in the hydrothermal area, at nearly 2000 m. The new species differs from the other species of the genus in the presence of long serrate chaetae with thin straight tips in neuropodia of the middle part of the body, and in the position of the heart body, which first appears much more anteriorly than in all previously described species of both genera comprising the subfamily Raphidrilinae Hartmann-Schroder, 1971. Raricirrus arcticus sp. nov. is likely most closely related to the geographically nearest R. beryli Petersen et George, 1991 sharing the absence of a modified region with enlarged spines and the presence of distinct ventral ciliary fields in the area of the mouth and the neural ciliary band on a few anterior segments. Asexual and sexual reproduction is noted for the new species. The hypothesis of Petersen and George (1991) about the role of the heart body in the head regeneration process is supported by revealed correlation of the anteriormost occurrence of the heart body with the number of segments in anterior regenerates in R. arcticus sp. nov., as in other Raricirrus species. Systematic position of the family Ctenodrilidae and taxonomic differences between the genera Raricirrus Hartman, 1961 and Raphidrilus Monticelli, 1910 are discussed. Morphological characters useful in distinguishing species within the genus Raricirrus are defined. A key to identify the known species of Raricirrus is given.

Dartintinnus alderae n. g., n. sp., a Brackish Water Tintinnid (Ciliophora, Spirotrichea) with Dual-ended Lorica Collapsibility.

A tintinnid ciliate isolated from waters of the Thames River (Connecticut, USA) is described through combined invivo observation, protargol impregnation, and phylogenetic analysis. The novel genus Dartintinnus and its type species, D.alderae are distinct from established tintinnid taxa by a lorica that collapses on both anterior and posterior ends. Dartintinnus is placed in the family Eutintinnidae based on a hyaline, elongated lorica opened at both ends, a ciliary pattern including a ventral kinety, at least one dorsal kinety, and right, left and lateral fields, and a sister relationship with Eutintinnus in gene trees. Main differences between D.alderae and Eutintinnus species include a 5.5-6.5% divergence in the small subunit rRNA gene, the geometry of the lorica (resembling an isosceles tetrahedron when collapsed vs. a cylinder, respectively), the number of macronuclear nodules (two vs. four), and the number of dorsal kineties (one vs. usually two). Considering the features of the new genus, we improve the diagnosis of the family Eutintinnidae, including the presence of a lateral ciliary field that had been overlooked in some Eutintinnus species. This work exemplifies the potential for novel diversity, even in these relatively well-studied protists, and the importance of an integrated approach for the description of tintinnid taxa.

Developmental studies of the enigmatic wormCaobangia billetiGiard, 1893 (Annelida; Sabellidae), a symbiont of freshwater snails

Caobangiids are an aberrant group of annelids with an unusual phoronid-like body plan. The most perceptible anatomical characteristic of caobangiids is the anal trunk, which is recurved outside the body and ends with an anal opening located near the head. So far neither the larval development nor the metamorphosis of these worms have been investigated thoroughly. This study describes the larval development and metamorphosis ofCaobangia billeti, and focuses mainly on the formation of the alimentary tract. The trochophore has eight chaetigers. Embryogenesis includes the development of segmentally arranged bands of cilia and ventral ciliary fields, the development of chaetae and the early formation of anterior radioles. Upon exiting the larval duct, larvae have eyes with lenses, two pairs of rudimentary radioles on the prostomium, a pair of nephridia on the peristomium, and two capillary chaetae in each parapodium of segments 3–9; parapodia of the 10th segment also bear a row of palmate hooks. Metamorphosis takes about 20 h and involves dorso-ventral folding of the body and enlargement of the pygidium along the dorsal side of segments 5–8. Thus, the anus develops on the dorsal side of the 5th segment, the anal trunk forms from the projection of pygidium whereas the prepygidial growth zone appears posterior to the 8th body segment. After the completion of metamorphosis, the prostomial and peristomial segments are fused and reduced, eight full thoracic chaetigers derive from the larva's body. Abdominal chaetigers grow posteriorly from the prepygidial growth zone.

The anatomy of the blood vascular system of the giant vestimentiferan tubeworm Riftia pachyptila (Siboglinidae, Annelida).

The giant dimensions of vestimentiferan Riftia pachyptila (Jones, ) are achieved thanks to the well-developed vascular system. In the vestimentum, there is a complicated net of lacunae, including the brain blood supply and the ventral lacuna underlying the ciliary field. The trunk region has an extensive network of blood vessels feeding the gonads («rete mirabile»). The thick muscular lining of the mesenterial vessels in the trunk and the dorsal vessel in the opisthosome serves as an additional pump, pushing blood into numerous vessels in the segments. It was hypothesized that the blood envelope of the ventral blood vessel in the trunk provides the blood supply to the trophosome. The 3D reconstruction has revealed that there are two vascular systems of the tentacular crown of R. pachyptila. Blood runs into the tentacles via axial afferent vessels, as described earlier only for Riftia, and also via basal ones, as described for other vestimentiferans except Riftia. The basal ones are poorly developed, and the number of lamellar blood vessels is small, indicating a lack of demand for these within huge R. pachyptila. It appears that the presence of these vessels is the preserved ancestral state of Vestimentifera. In different portions of the dorsal vessel, the morphology of the intravasal body varies, depending on function.

Characterization of the cell polarity gene crumbs during the early development and maintenance of the squid-vibrio light organ symbiosis.

The protein Crumbs is a determinant of apical-basal cell polarity and plays a role in apoptosis of epithelial cells and their protection against photodamage. Using the squid-vibrio system, a model for development of symbiotic partnerships, we examined the modulation of the crumbs gene in host epithelial tissues during initiation and maintenance of the association. The extracellular luminous symbiont Vibrio fischeri colonizes the apical surfaces of polarized epithelia in deep crypts of the Euprymna scolopes light organ. During initial colonization each generation, symbiont harvesting is potentiated by the biochemical and biophysical activity of superficial ciliated epithelia, which are several cell layers from the crypt epithelia where the symbionts reside. Within hours of crypt colonization, the symbionts induce the cell death mediated regression of the remote superficial ciliated fields. However, the crypt cells directly interacting with the symbiont are protected from death. In the squid host, we characterized the gene and encoded protein during light organ morphogenesis and in response to symbiosis. Features of the protein sequence and structure, phylogenetic relationships, and localization patterns in the eye supported assignment of the squid protein to the Crumbs family. In situ hybridization revealed that the crumbs transcript shows opposite expression at the onset of symbiosis in the two different regions of the light organ: elevated levels in the superficial epithelia were attenuated whereas low levels in the crypt epithelia were turned up. Although a rhythmic association in which the host controls the symbiont population over the day-night cycle begins in the juvenile upon colonization, cycling of crumbs was evident only in the adult organ with peak expression coincident with maximum symbiont population and luminescence. Our results provide evidence that crumbs responds to symbiont cues that induce developmental apoptosis and to symbiont population dynamics correlating with luminescence-based stress throughout the duration of the host-microbe association.

New contributions to the biodiversity of ciliates (Protozoa, Ciliophora) from Antarctica, including a description of Gastronauta multistriata nov. spec.

Antarctica is a remote and isolated biotope which makes it an ideal location for studying new and endemic species. Since there is little literature available on the diversity of ciliates in this area, a taxonomic survey of ciliates from melt-water of Collins glacier, King George Island, was carried out from January to March 2006. As a result, the morphology and infraciliature of five ciliates, including one new species, are described using live observations and silver staining: Gastronauta multistriata nov. spec., Neokeronopsis asiatica Foissner et al., 2010, Paraholosticha muscicola Kahl, 1932, Oxytricha sp., and Cyclidium glaucoma Muller, 1786. Gastronauta multistriata nov. spec. is distinguished from its congeners by the following combination of characters: cell size in vivo on average 80 × 40 μm; 5–9 kineties in left ciliary field; 18–23 kineties in right ciliary field, including 10–12 postoral kineties; 7–10 preoral kineties; dorsal brush along anterior dorsal margin, consisting of 5–8 groups of basal bodies. The only minor differences between the current population of N. asiatica and a previously described Antarctic population are the numbers of caudal cirri (6–10 vs. 8–15) and dorsal kineties (11–13 vs. 12–18). Paraholosticha sterkii is synonymised with P. muscicola. The Antarctic population of C. glaucoma corresponds well with a former population from China, the only difference being the number of kinetids in SK n (11–17 vs. 9–11). This work will contribute to the understanding of ciliate diversity in this little studied area.