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Loriano Ballarin - One of the best experts on this subject based on the ideXlab platform.
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natural apoptosis during the blastogenetic cycle of the colonial ascidian botryllus schlosseri a morphological analysis
Zoological Science, 2010Co-Authors: Loriano Ballarin, Filippo Schiavon, Lucia ManniAbstract:Colonies of the compound ascidian Botryllus schlosseri undergo regular generation changes, during which adult Zooids are progressively resorbed and replaced by growing buds. The generation change, or take-over, is characterized by massive cell death by apoptosis, as indicated by nuclear condensation, activation of caspases, overexpression of molecules recognized by antibodies against mammalian Bax, Fas, and FasL, changes in the expression of surface molecules by senescent cells of Zooid tissues, and recruitment of circulating phagocytes in Zooid tissues which ensure the complete clearing of dying cells. The entire process lasts 24–36 h at 20 o C and has been subdivided, on the basis of the degree of contraction of old Zooids, into four substages. In the present work, we carried out a detailed morphological analysis of the events occurring in Zooid tissues during the take-over substages. Results indicate that traces of apoptosis can be found in the epidermis, peribranchial epithelium, and heart in the late substage but are easily found in the branchial basket 2– 4 h after the beginning of the generation change, thus confirming the antero-posterior progression of cell death, at least in the alimentary system.
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apoptosis and pattern of bcl 2 and bax expression in the alimentary tract during the colonial blastogenetic cycle of botryllus schlosseri urochordata ascidiacea
Italian Journal of Zoology, 2009Co-Authors: Francesca Cima, Loriano BallarinAbstract:Botryllus schlosseri is a colonial ascidian representing a suitable subject for studies on cyclical involution and resorption of tissues. At 19°C, adult Zooids remain active for one week, then they are gradually resorbed, being replaced by a new generation of adult Zooids, represented by buds which reach functional maturity. This stage, known as regression or take‐over, is characterised by diffuse programmed cell death by apoptosis in Zooid tissues, as shown by annexin V labelling for detection of exposed phosphatidylserine and the TUNEL reaction for chromatin fragmentation. Immunocytochemical assays to detect proapoptotic and antiapoptotic factors reveal the opposite expression of Bcl‐2 and Bax proteins, which extends in tissues of adult Zooids with an antero‐posterior progression starting from the pharynx. Bax is expressed in all tissues of the digestive tract in the stage preceding take‐over: together with signs of DNA fragmentation in the pharynx and pyloric gland, it suggests that this is the crucial...
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haemocytes and blastogenetic cycle in the colonial ascidian botryllus schlosseri a matter of life and death
Cell and Tissue Research, 2008Co-Authors: Loriano Ballarin, Paolo Burighel, A Menin, Laura Tallandini, Valerio Matozzo, Giuseppe Basso, Elena Fortunato, Francesca CimaAbstract:A recurrent blastogenetic cycle characterizes colonies of the ascidian Botryllus schlosseri. This cycle starts when a new Zooid generation opens its siphons and ends with take-over, when adult Zooids cease filtering and are progressively resorbed and replaced by a new generation of buds, reaching functional maturity. During the generation change, massive apoptosis occurs in the colony, mainly in the tissues of old Zooids. In the present study, we have investigated the behaviour of haemocytes during the colonial blastogenetic cycle, in terms of the occurrence of cell death and the expression of molecules involved in the induction of apoptosis. Our results indicate that, during take-over, caspase-3 activity in haemocyte lysates increases. In addition, about 20%–30% of haemocytes express phosphatidylserine on the outer leaflet of their plasma membrane, show DNA fragmentation and are immunopositive for caspase-3. Senescent cells are quickly ingested by circulating phagocytes that frequently, having once engulfed effete cells, in turn enter apoptosis. Dying cells and corpses are replaced by a new generation of cells that appear in the circulation during the generation change.
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a tale of death and life natural apoptosis in the colonial ascidian botryllus schlosseri urochordata ascidiacea
Current Pharmaceutical Design, 2008Co-Authors: Loriano Ballarin, Paolo Burighel, Francesca CimaAbstract:The colonial ascidian Botryllus schlosseri forms new Zooids by blastogenesis, through the formation of palleal buds which progressively grow and mature until adults are formed. At a temperature of 19°C, adult Zooids remain active for about one week; then they contract, close their siphons and are gradually resorbed, being replaced by buds which reach functional maturity, open their siphons and begin their filtering activity as adult Zooids. This recurrent generation change, known as take-over, is characterised by the occurrence of diffuse programmed cell death by apoptosis. Immediately before the take-over, an increase in the expression of molecules recognised by anti-Bax antibodies and a parallel decrease in the expression of molecules immunopositive to anti-Bcl-2 antibodies were observed in Zooid tissues, suggesting a mitochondrion-dependent apoptotic pathway. During the take-over, circulating phagocytes infiltrate the Zooid tissues and engulf apoptotic cells; in addition, the frequency of haemocytes showing nuclear condensation and annexin-V labelling significantly increases. Previous experiments showed the involvement of phosphatidylserine and CD36 in the recognition of effete cell. The resorption of old Zooids is closely related to the rejuvenation of the colony occurring at the take-over. The death of adult Zooids puts a quantity of material at the colony disposal. This material is represented by senescent cells, which, once ingested and digested by phagocytes, can be recycled and used to sustain the burden of blastogenesis: this involves a cross-talk between old tissues, phagocytes and developing buds. Therefore, B. schlosseri can be considered a new and promising model organism for the study of natural apoptosis.
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A tale of death and life: natural apoptosis in the colonial ascidian Botryllus schlosseri (Urochordata, Ascidiacea).
Current pharmaceutical design, 2008Co-Authors: Loriano Ballarin, Paolo Burighel, Francesca CimaAbstract:The colonial ascidian Botryllus schlosseri forms new Zooids by blastogenesis, through the formation of palleal buds which progressively grow and mature until adults are formed. At a temperature of 19 degrees C, adult Zooids remain active for about one week; then they contract, close their siphons and are gradually resorbed, being replaced by buds which reach functional maturity, open their siphons and begin their filtering activity as adult Zooids. This recurrent generation change, known as take-over, is characterised by the occurrence of diffuse programmed cell death by apoptosis. Immediately before the take-over, an increase in the expression of molecules recognised by anti-Bax antibodies and a parallel decrease in the expression of molecules immunopositive to anti-Bcl-2 antibodies were observed in Zooid tissues, suggesting a mitochondrion-dependent apoptotic pathway. During the take-over, circulating phagocytes infiltrate the Zooid tissues and engulf apoptotic cells; in addition, the frequency of haemocytes showing nuclear condensation and annexin-V labelling significantly increases. Previous experiments showed the involvement of phosphatidylserine and CD36 in the recognition of effete cell. The resorption of old Zooids is closely related to the rejuvenation of the colony occurring at the take-over. The death of adult Zooids puts a quantity of material at the colony disposal. This material is represented by senescent cells, which, once ingested and digested by phagocytes, can be recycled and used to sustain the burden of blastogenesis: this involves a cross-talk between old tissues, phagocytes and developing buds. Therefore, B. schlosseri can be considered a new and promising model organism for the study of natural apoptosis.
Francesca Cima - One of the best experts on this subject based on the ideXlab platform.
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apoptosis and pattern of bcl 2 and bax expression in the alimentary tract during the colonial blastogenetic cycle of botryllus schlosseri urochordata ascidiacea
Italian Journal of Zoology, 2009Co-Authors: Francesca Cima, Loriano BallarinAbstract:Botryllus schlosseri is a colonial ascidian representing a suitable subject for studies on cyclical involution and resorption of tissues. At 19°C, adult Zooids remain active for one week, then they are gradually resorbed, being replaced by a new generation of adult Zooids, represented by buds which reach functional maturity. This stage, known as regression or take‐over, is characterised by diffuse programmed cell death by apoptosis in Zooid tissues, as shown by annexin V labelling for detection of exposed phosphatidylserine and the TUNEL reaction for chromatin fragmentation. Immunocytochemical assays to detect proapoptotic and antiapoptotic factors reveal the opposite expression of Bcl‐2 and Bax proteins, which extends in tissues of adult Zooids with an antero‐posterior progression starting from the pharynx. Bax is expressed in all tissues of the digestive tract in the stage preceding take‐over: together with signs of DNA fragmentation in the pharynx and pyloric gland, it suggests that this is the crucial...
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haemocytes and blastogenetic cycle in the colonial ascidian botryllus schlosseri a matter of life and death
Cell and Tissue Research, 2008Co-Authors: Loriano Ballarin, Paolo Burighel, A Menin, Laura Tallandini, Valerio Matozzo, Giuseppe Basso, Elena Fortunato, Francesca CimaAbstract:A recurrent blastogenetic cycle characterizes colonies of the ascidian Botryllus schlosseri. This cycle starts when a new Zooid generation opens its siphons and ends with take-over, when adult Zooids cease filtering and are progressively resorbed and replaced by a new generation of buds, reaching functional maturity. During the generation change, massive apoptosis occurs in the colony, mainly in the tissues of old Zooids. In the present study, we have investigated the behaviour of haemocytes during the colonial blastogenetic cycle, in terms of the occurrence of cell death and the expression of molecules involved in the induction of apoptosis. Our results indicate that, during take-over, caspase-3 activity in haemocyte lysates increases. In addition, about 20%–30% of haemocytes express phosphatidylserine on the outer leaflet of their plasma membrane, show DNA fragmentation and are immunopositive for caspase-3. Senescent cells are quickly ingested by circulating phagocytes that frequently, having once engulfed effete cells, in turn enter apoptosis. Dying cells and corpses are replaced by a new generation of cells that appear in the circulation during the generation change.
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a tale of death and life natural apoptosis in the colonial ascidian botryllus schlosseri urochordata ascidiacea
Current Pharmaceutical Design, 2008Co-Authors: Loriano Ballarin, Paolo Burighel, Francesca CimaAbstract:The colonial ascidian Botryllus schlosseri forms new Zooids by blastogenesis, through the formation of palleal buds which progressively grow and mature until adults are formed. At a temperature of 19°C, adult Zooids remain active for about one week; then they contract, close their siphons and are gradually resorbed, being replaced by buds which reach functional maturity, open their siphons and begin their filtering activity as adult Zooids. This recurrent generation change, known as take-over, is characterised by the occurrence of diffuse programmed cell death by apoptosis. Immediately before the take-over, an increase in the expression of molecules recognised by anti-Bax antibodies and a parallel decrease in the expression of molecules immunopositive to anti-Bcl-2 antibodies were observed in Zooid tissues, suggesting a mitochondrion-dependent apoptotic pathway. During the take-over, circulating phagocytes infiltrate the Zooid tissues and engulf apoptotic cells; in addition, the frequency of haemocytes showing nuclear condensation and annexin-V labelling significantly increases. Previous experiments showed the involvement of phosphatidylserine and CD36 in the recognition of effete cell. The resorption of old Zooids is closely related to the rejuvenation of the colony occurring at the take-over. The death of adult Zooids puts a quantity of material at the colony disposal. This material is represented by senescent cells, which, once ingested and digested by phagocytes, can be recycled and used to sustain the burden of blastogenesis: this involves a cross-talk between old tissues, phagocytes and developing buds. Therefore, B. schlosseri can be considered a new and promising model organism for the study of natural apoptosis.
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A tale of death and life: natural apoptosis in the colonial ascidian Botryllus schlosseri (Urochordata, Ascidiacea).
Current pharmaceutical design, 2008Co-Authors: Loriano Ballarin, Paolo Burighel, Francesca CimaAbstract:The colonial ascidian Botryllus schlosseri forms new Zooids by blastogenesis, through the formation of palleal buds which progressively grow and mature until adults are formed. At a temperature of 19 degrees C, adult Zooids remain active for about one week; then they contract, close their siphons and are gradually resorbed, being replaced by buds which reach functional maturity, open their siphons and begin their filtering activity as adult Zooids. This recurrent generation change, known as take-over, is characterised by the occurrence of diffuse programmed cell death by apoptosis. Immediately before the take-over, an increase in the expression of molecules recognised by anti-Bax antibodies and a parallel decrease in the expression of molecules immunopositive to anti-Bcl-2 antibodies were observed in Zooid tissues, suggesting a mitochondrion-dependent apoptotic pathway. During the take-over, circulating phagocytes infiltrate the Zooid tissues and engulf apoptotic cells; in addition, the frequency of haemocytes showing nuclear condensation and annexin-V labelling significantly increases. Previous experiments showed the involvement of phosphatidylserine and CD36 in the recognition of effete cell. The resorption of old Zooids is closely related to the rejuvenation of the colony occurring at the take-over. The death of adult Zooids puts a quantity of material at the colony disposal. This material is represented by senescent cells, which, once ingested and digested by phagocytes, can be recycled and used to sustain the burden of blastogenesis: this involves a cross-talk between old tissues, phagocytes and developing buds. Therefore, B. schlosseri can be considered a new and promising model organism for the study of natural apoptosis.
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apoptosis and phosphatidylserine mediated recognition during the take over phase of the colonial life cycle in the ascidian botryllus schlosseri
Cell and Tissue Research, 2003Co-Authors: Francesca Cima, Giuseppe Basso, Loriano BallarinAbstract:Colonies of the ascidian Botryllus schlosseri undergo recurrent generation changes in which adult Zooids are gradually resorbed and replaced by new blastogenic generations. During these periods, known as take-over phases, programmed cell death, which, on the basis of morphological analysis is ascribed to apoptosis, occurs widely in Zooid tissues. In the present report, we re-investigate cell death during the take-over process. Results confirm the occurrence of diffuse apoptosis, as evidenced by chromatin condensation, positivity to the TUNEL reaction and expression of phosphatidylserine on the outer leaflet of the plasma membrane. Apoptosis also occurs among haemocytes, and senescent blood cells are actively recognised and ingested by circulating professional phagocytes. Both phosphatidylserine and CD36, a component of the thrombospondin receptor, are involved in the recognition of apoptotic haemocytes, which fosters the idea that fundamental recognition mechanisms are well conserved throughout chordate evolution.
Irving L Weissman - One of the best experts on this subject based on the ideXlab platform.
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life histories and senescence of botryllus schlosseri chordata ascidiacea in monterey bay
The Biological Bulletin, 1995Co-Authors: Nanette E Chadwickfurman, Irving L WeissmanAbstract:The colonial ascidian Botryllus schlosseri is a model organism for research on invertebrate histocompatibility, development, and evolutionary biology. Nonetheless, the basic life history of Pacific Ocean populations of the species remains unknown. We determined field rates of growth, reproduction, and senescence in four cohorts of B. schlosseri colonies in Monterey Bay, California. Colonies grew exponentially as juveniles and reached sizes of up to 1400 Zooids within 69 days. After a juvenile phase lasting at least 49 days, the colonies began to reproduce sexually. Each Zooid produced up to 10 clutches, each with a maximum of 5 eggs, resulting in very high fecundity of up to 8000 eggs per colony. Following a short period (maximum 70 days) of continuous sexual reproduction, colonies abruptly senesced and died while still bearing a full clutch of eggs. Senescence progressed through four distinct stages over 1-2 weeks, and inevitably led to the simultaneous death of all Zooids in the colony. Although senesce...
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life histories and senescence of botryllus schlosseri chordata ascidiacea in monterey bay
The Biological Bulletin, 1995Co-Authors: Nanette E Chadwickfurman, Irving L WeissmanAbstract:The colonial ascidian Botryllus schlosseri is a model organism for research on invertebrate histocompatibility, development, and evolutionary biology. Nonetheless, the basic life history of Pacific Ocean populations of the species remains unknown. We determined field rates of growth, reproduction, and senescence in four cohorts of B. schlosseri colonies in Monterey Bay, California. Colonies grew exponentially as juveniles and reached sizes of up to 1400 Zooids within 69 days. After a juvenile phase lasting at least 49 days, the colonies began to reproduce sexually. Each Zooid produced up to 10 clutches, each with a maximum of 5 eggs, resulting in very high fecundity of up to 8000 eggs per colony. Following a short period (maximum 70 days) of continuous sexual reproduction, colonies abruptly senesced and died while still bearing a full clutch of eggs. Senescence progressed through four distinct stages over 1-2 weeks, and inevitably led to the simultaneous death of all Zooids in the colony. Although senescence was the main cause of mortality, some colonies died as a result of predation or undermined causes. Certain life history traits varied significantly between cohorts that settled at different times of year. For example, lifespans in the field varied from about 3 months for spring to 8 months for fall-born colonies, but the lifetime fecundity of colonies did not vary between cohorts. The morphologies and life histories of colonies monitored in the field and reported here differed from those of colonies cultured previously in the laboratory.
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a morphological and immunohistochemical study of programmed cell death in botryllus schlosseri tunicata ascidiacea
Cell and Tissue Research, 1993Co-Authors: Robert J Lauzon, Chris Patton, Irving L WeissmanAbstract:The blastogenic cycle of the colonial ascidian Botryllus schlosseri concludes in a phase of selective cell and Zooid death called takeover. Every week, all asexually derived parental Zooids synchronously regress over a 30-h period and are replaced by a new generation. Here we document the sequential ultrastructural changes which accompany cell death during Zooid degeneration. The principal mode of visceral cell death during takeover occurred by apoptosis, the majority of cells condensing and fragmenting into multiple membrane-bounded apoptotic bodies. Cytoplasmic organelles (mitochondria, basal bodies, striated rootlets) within apoptotic bodies retained ultrastructural integrity. Dying cells and fragments were then swiftly ingested by specialized blood macrophages or intraepithelial phagocytes and subsequently underwent secondary necrotic lysis. Certain organs (stomach, intestine) displayed a combination of necrotic and apoptotic changes. Lastly, the stomach, which demonstrated some of the earliest regressive changes, exhibited intense cytoplasmic immunostaining with a monoclonal antibody to ubiquitin at the onset of takeover. Affinity-purified rabbit antiserum against sodium dodecyl sulfate-denatured ubiquitin detected a characteristic 8.6-kDa mono-ubiquitin band by Western blot analysis. Collectively, these findings raise the possibility that cell death during takeover is a dynamic process which requires active participation of cells in their own destruction.
Gordon, Dennis P. - One of the best experts on this subject based on the ideXlab platform.
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FIGURE 5. Fatkullina imitata n in Fatkullina imitata n. sp., second species of a unique cheilostome bryozoan genus with reversed-polarity Zooidal budding, and new family Fatkullinidae
2018Co-Authors: Grischenko Andrei, Gordon, Dennis P., Morozov, Taras B.Abstract:FIGURE 5. Fatkullina imitata n. sp. A, paratype 5 ZIRAS 6/50666; B, holotype ZIRAS 1/50661; C–G, paratype 2 ZIRAS 3/ 50663. A. Orificial area of newly formed Zooid near colony margin, showing transversely oval primary orifice bordered by thinly calcified smooth narrow rim, and surrounded by granular-tubercular surface with circular pseudopores. B. Orificial area of completed Zooid, showing drop-shaped secondary orifice with granular tubercular surface, overhanging distal curvature of deeply submerged primary orifice, leaving visible its proximal thickened smooth shelf with shallow sinus; note circular infundibular pseudopores with finely tuberculated surfaces stretched deep inside. C. Interior of Zooidal orificial area, showing transversally oval primary orifice with shallow sinus and deep calcified visor with denticulate margin, covers half of primary orifice length. D. Interior of group of Zooids from central colony area, indicating their incoherent orientation, showing transversally oval primary orifices, smaller circular scattered openings of pseudopores in frontal shields, and enlarged circular to oval openings of tubular areolar pore channels encroaching via vertical walls, which connect main coelom with hypostegal coelom. E. Interior of frontal shield, showing scattered smaller openings of pseudopores centrally, enlarged openings of tubular areolar pore channels encroaching via vertical walls, which connect main coelom with hypostegal coelom, and transversally oval primary orifice with distal overhanging visor of secondary calcification covering more than 2/3 of primary orifice length. F. Internal and external view of Zooidal lateral wall with basal pore chambers and external openings of tubular areolar pore channels encroaching lateral wall to open into the hypostegal coelom. G. Longitudinal cross-section through Zooid, showing remarkable thickness of frontal shield, with deep, proximally tilted lumen between primary and secondary orifices, and lateral to frontal openings of tubular areolar pore channels connecting main coelom with hypostegal coelom. Scale bars: A–C, E–G, 0.1 mm; D, 0.25 mm
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FIGURE 35. Calyssopora clarionensis n. gen., n in Bryozoa (Cyclostomata and Ctenostomata) from polymetallic nodules in the Russian exploration area, Clarion - Clipperton Fracture Zone, eastern Pacific Ocean-taxon novelty and implications of mining
2018Co-Authors: Grischenko Andrei, Gordon, Dennis P., Melnik, Viacheslav P.Abstract:FIGURE 35. Calyssopora clarionensis n. gen., n. sp. Progressive stages of development of ancestrular and young colonies. A–D, specimen YMG18–01, Stn 24, three-Zooid colony; E–H, specimen GLD4–08, Stn 144, four–five-Zooid stage; I–L, specimen YMG4–07, Stn 134, seven-Zooid stage with central cavity presumably representing incipient incubation chamber; M–P, specimen GLD4–11, Stn 209, eight-Zooid stage with paired central cavities. Scale bars: 200 µm
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FIGURE 52. Alyonushka filia n. gen., n in Bryozoa (Cyclostomata and Ctenostomata) from polymetallic nodules in the Russian exploration area, Clarion - Clipperton Fracture Zone, eastern Pacific Ocean-taxon novelty and implications of mining
2018Co-Authors: Grischenko Andrei, Gordon, Dennis P., Melnik, Viacheslav P.Abstract:FIGURE 52. Alyonushka filia n. gen., n. sp. Micro-CT scans of paratype, NIWA 127724, as back-face isosurface renders showing colony interiors. A, entire colony in profile; note the density of kenoZooidal chambers in the column; B, close-up of distal part of column showing diminished numbers of kenoZooids where it broadens into the calyx; C, optical section through gonoZooid and ooeciostome, with arrowhead indicating a ledge at inner opening of ooeciostome; D, optical section through base of column showing protoecial dome with ancestrular peristome emerging from its apex (purple) and first daughter Zooid (red) also originating from protoecium (its communication pore outside plane of section); note multiple layers of kenoZooids; E, three successive sections through ancestrular region, moving upwards from left to right, respectively showing protoecium (red) and first daughter Zooid (yellow), narrowing to ancestrular peristome and broadening peristome of daughter Zooid. Scale bars: A, B, 250 µm; C–E, 100 µm
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FIGURES 1–3 in Systematics of some calloporid and lacernid Cheilostomata (Bryozoa) from coastal South Korean waters, with the description of new taxa
2017Co-Authors: Min, Bum Sik, Grischenko Andrei, Seo, Ji Eun, Lee Sang-kyu, Gordon, Dennis P.Abstract:FIGURES 1–3. Crassimarginatella kumatae (Okada, 1923), Stn I2 near Wan Island. 1, AutoZooids and a subvicarious avicularium; note the variability in spination; scalebar 200 µm. 2, Ovicellate Zooid showing the large exposure of granular endooecium; scalebar 100 µm. 3, Tatiform ancestrula, three daughter Zooids and later proximal Zooids; scalebar 200 µm
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FIGURES 24–26. Exochella cryptodontia n in Intertidal Bryozoa from Korea—new additions to the fauna and a new genus of Bitectiporidae (Cheilostomata) from Baengnyeong Island, Yellow Sea
2017Co-Authors: Min, Bum Sik, Grischenko Andrei, Seo, Ji Eun, Gordon, Dennis P.Abstract:FIGURES 24–26. Exochella cryptodontia n. sp., Hwadong (except for 25, from Cheongsan Island). 24, Frontal view of ovicellate Zooids, with three umbonate ooecia occupying virtually the entire frontal shield of each next-distal Zooid; scale bar, 200 µm. 25, Interior of a frontal shield showing the clearly delimited umbonuloid area with a toothed distal margin; scale bar, 100 µm. 26, Differentiating Zooids at the colony margin showing distal oral-spine bases and the formation of the peristomial pseudospiramen; arrows indicate the denticulation on the inner proximal margin of the orifice; scale bar, 200 µm
Casey W Dunn - One of the best experts on this subject based on the ideXlab platform.
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the histology of nanomia bijuga hydrozoa siphonophora
Journal of Experimental Zoology, 2015Co-Authors: Samuel H Church, Stefan Siebert, Pathikrit Bhattacharyya, Casey W DunnAbstract:The siphonophore Nanomia bijuga is a pelagic hydrozoan (Cnidaria) with complex morphological organization. Each siphonophore is made up of many asexually produced, genetically identical Zooids that are functionally specialized and morphologically distinct. These Zooids predominantly arise by budding in two growth zones, and are arranged in precise patterns. This study describes the cellular anatomy of several Zooid types, the stem, and the gas-filled float, called the pneumatophore. The distribution of cellular morphologies across Zooid types enhances our understanding of Zooid function. The unique absorptive cells in the palpon, for example, indicate specialized intracellular digestive processing in this Zooid type. Though cnidarians are usually thought of as mono-epithelial, we characterize at least two cellular populations in this species which are not connected to a basement membrane. This work provides a greater understanding of epithelial diversity within the cnidarians, and will be a foundation for future studies on N. bijuga, including functional assays and gene expression analyses.
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the histology of nanomia bijuga hydrozoa siphonophora
bioRxiv, 2014Co-Authors: Samuel H Church, Stefan Siebert, Pathikrit Bhattacharyya, Casey W DunnAbstract:The siphonophore Nanomia bijuga is a pelagic hydrozoan (Cnidaria) with complex morphological organization. Each siphonophore is made up of many asexually produced, genetically identical Zooids that are functionally specialized and morphologically distinct. These Zooids predominantly arise by budding in two growth zones, and are arranged in precise patterns. This study describes the cellular anatomy of several Zooid types as well as of the stem and gas-filled float, called the pneumatophore. The distribution of cellular morphologies across Zooid types enhances our understanding of Zooid function. The unique absorptive cells in the palpon, for example, indicate specialized intracellular digestive processing in this Zooid type. Furthermore, there are multiple areas of both endodermal and ectodermal epithelial complexity. Though cnidarians are usually thought of as mono-epithelial, we characterize at least two cellular populations in this species which are not connected to a basement membrane. This work provides a greater understanding of epithelial diversity within the cnidarians, and will be a foundation for future studies on Nanomia bijuga, including functional assays and gene expression analyses.
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complex colony level organization of the deep sea siphonophore bargmannia elongata cnidaria hydrozoa is directionally asymmetric and arises by the subdivision of pro buds
Developmental Dynamics, 2005Co-Authors: Casey W DunnAbstract:Siphonophores are free-swimming colonial hydrozoans (Cnidaria) composed of asexually produced multicellular Zooids. These Zooids, which are homologous to solitary animals, are functionally specialized and arranged in complex species-specific patterns. The coloniality of siphonophores provides an opportunity to study the major transitions in evolution that give rise to new levels of biological organization, but siphonophores are poorly known because they are fragile and live in the open ocean. The organization and development of the deep-sea siphonophore Bargmannia elongata is described here using specimens collected with a remotely operated underwater vehicle. Each bud gives rise to a precise, directionally asymmetric sequence of Zooids through a stereotypical series of subdivisions, rather than to a single Zooid as in most other hydrozoans. This initial description of development in a deep-sea siphonophore provides an example of how precise colony-level organization can arise, and illustrates that the morphological complexity of cnidarians is greater than is often assumed.
