Feeding cessation alters host morphology and bacterial communities in the ascidian Pseudodistoma crucigaster

11 páginas, 2 tablas, 7 figurasBackground: Ascidians can associate with abundant and diverse consortia ofmicrobial symbionts, yet these communities remain unexamined for the majority of host ascidians and little is known about host-symbiont interactions. Methods: We coupled electron microscopy and 16S rRNA gene tag pyrosequencing to investigate the bacterial communities associated with the colonial ascidian Pseudodistoma crucigaster, a species endemic to theMediterranean Sea that has a life cycle with two phases: actively-filtering (active) and non-filtering (resting) forms. Results: Resting colonies exhibited a reduced branchial sac (feeding apparatus) and a thickened cuticle. Electron microscope images also suggested higher abundance of colonizing microorganisms on surfaces of resting colonies. Accordingly, bacterial sequences associated with environmental sources (sediment and biofilms, >99 % similarity) were detected exclusively in resting colonies. Bacterial communities of P. crucigaster colonies (active and resting) were dominated by 3 core taxa affiliated (>94 % similarity) with previously described symbiotic Alphaproteobacteria in marine invertebrates. Shifts in rare bacteria were detected when ascidians entered the resting phase, including the appearance of strictly anaerobic lineages and nitrifying bacterial guilds. Conclusions: These findings suggest that physical (thickened cuticle) and metabolic (feeding cessation) changes in host ascidians have cascading effects on associated bacteria, where modified oxygen concentrations and chemical substrates for microbial metabolism may create anaerobic microhabitats and promote colonization by environmental microorganisms.This research was funded by the Marie Curie International Reintegration Grant FP7-PEOPLE-2010-RG 277038 within the 7th European Community Framework Program, the Spanish Government projects MARSYMBIOMICS CTM2013-43287-P and CHALLENGEN CTM2013-48163, and the Catalan Government grant 2014SGR-336 for Consolidated Research Groups.Peer reviewe

Ultrastructure, molecular phylogenetics and chlorophyll a content of novel cyanobacterial symbionts in temperate sponge hosts

Marine sponges often harbor photosynthetic symbionts that may enhance host metabolism and ecological success, yet little is known about the factors that structure the diversity, specificity, and nature of these relationships. Here, we characterized the cyanobacterial symbionts in two congeneric and sympatric host sponges that exhibit distinct habitat preferences correlated with irradiance: Ircinia fasciculata (higher irradiance) and Ircinia variabilis (lower irradiance). Symbiont composition was similar among hosts and dominated by the sponge-specific cyanobacterium Synechococcus spongiarum. Phylogenetic analyses of 16S-23S rRNA internal transcribed spacer (ITS) gene sequences revealed that Mediterranean Ircinia spp. host a specific, novel symbiont clade ("M") within the S. spongiarum species complex. A second, rare cyanobacterium related to the ascidian symbiont Synechocystis trididemni was observed in low abundance in I. fasciculata and likewise corresponded to a new symbiont clade. Symbiont communities in I. fasciculata exhibited nearly twice the chlorophyll a concentrations of I. variabilis. Further, S. spongiarum clade M symbionts in I. fasciculata exhibited dense intracellular aggregations of glycogen granules, a storage product of photosynthetic carbon assimilation rarely observed in I. variabilis symbionts. In both host sponges, S. spongiarum cells were observed interacting with host archeocytes, although the lower photosynthetic activity of Cyanobacteria in I. variabilis suggests less symbiont-derived nutritional benefit. The observed differences in clade M symbionts among sponge hosts suggest that ambient irradiance conditions dictate symbiont photosynthetic activity and consequently may mediate the nature of host-symbiont relationships. In addition, the plasticity exhibited by clade M symbionts may be an adaptive attribute that allows for flexibility in host-symbiont interactions across the seasonal fluctuations in light and temperature characteristic of temperate environments

Till death do us part: Stable sponge-bacteria associations under thermal and food shortage stresses

Sporadic mass mortality events of Mediterranean sponges following periods of anomalously high temperatures or longer than usual stratification of the seawater column (i.e. low food availability) suggest that these animals are sensitive to environmental stresses. The Mediterranean sponges Ircinia fasciculata and I. oros harbor distinct, species-specific bacterial communities that are highly stable over time and space but little is known about how anomalous environmental conditions affect the structure of the resident bacterial communities. Here, we monitored the bacterial communities in I. fasciculata (largely affected by mass mortalities) and I. oros (overall unaffected) maintained in aquaria during 3 weeks under 4 treatments that mimicked realistic stress pressures: control conditions (13°C, unfiltered seawater), low food availability (13°C, 0.1 µm-filtered seawater), elevated temperatures (25°C, unfiltered seawater), and a combination of the 2 stressors (25°C, 0.1 µm-filtered seawater). Bacterial community structure was assessed using terminal restriction fragment length polymorphism (T-RFLP) analysis of 16S rRNA gene sequences and transmission electron microscopy (TEM). As I. fasciculata harbors cyanobacteria, we also measured chlorophyll a (chl a) levels in this species. Multivariate analysis revealed no significant differences in bacterial T-RFLP profiles among treatments for either host sponge species, indicating no effect of high temperatures and food shortage on symbiont community structure. In I. fasciculata, chl a content did not significantly differ among treatments although TEM micrographs revealed some cyanobacteria cells undergoing degradation when exposed to both elevated temperature and food shortage conditions. Arguably, longer-term treatments (months) could have eventually affected bacterial community structure. However, we evidenced no appreciable decay of the symbiotic community in response to medium-term (3 weeks) environmental anomalies purported to cause the recurrent sponge mortality episodes. Thus, changes in symbiont structure are not likely the proximate cause for these reported mortality events

Stable populations in unstable habitats: temporal genetic structure of the introduced ascidian Styela plicata in North Carolina

14 páginas, 3 tablas, 4 figuras.The analysis of temporal genetic variability is an essential yet largely neglected tool to unveil and predict the dynamics of introduced species. We here describe the temporal genetic structure and diversity over time of an introduced population of the ascidian Styela plicata (Lesueur, 1823) in Wilmington (North Carolina, USA, 34°08′24″N, 77°51′44″W). This population suffers important salinity and temperature changes, and in June every year we observed massive die-offs, leaving free substratum that was recolonized within a month. We sampled 12–14 individuals of S. plicata every 2 months from 2007 to 2009 (N = 196) and analyzed a mitochondrial marker (the gene cytochrome oxidase subunit I, COI) and seven nuclear microsatellites. Population genetic analyses showed similar results for both types of markers and revealed that most of the genetic variation was found within time periods. However, analyses conducted with microsatellite loci also showed weak but significant differences among time periods. Specifically, in the samplings after die-off episodes (August–November 2007 and 2008) the genetic diversity increased, the inbreeding coefficient showed prominent drops, and there was a net gain of alleles in the microsatellite loci. Taken together, our results suggest that recruits arriving from neighboring populations quickly occupied the newly available space, bringing new alleles with them. However, other shifts in genetic diversity and allele loss and gain episodes were observed in December–January and February–March 2008, respectively, and were apparently independent of die-off events. Overall, our results indicate that the investigated population is stable over time and relies on a periodic arrival of larvae from other populations, maintaining high genetic diversity and a complex interplay of allele gains and losses.This research was supported by a grant from the United States–Israel Binational Science Foundation (BSF), Jerusalem, Israel (number 2014025), the Spanish Government project CTM2013—48163—and the Catalan Government Grant 2014SGR-336 for Consolidated Research Groups.Peer reviewe

Desenho do teletrabalho : percepções e práticas

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Economia, Administração e Contabilidade, Programa de Pós-Graduação em Administração, 2020.O teletrabalho (TT) é uma modalidade que possibilita ao trabalhador executar as suas atividades fora do ambiente organizacional, com o apoio de recursos tecnológicos. A adoção desse arranjo de trabalho é crescente no Brasil e encontra amparo em três marcos legais que regulamentam o TT em órgãos dos Poderes Judiciário e Executivo Federal e empresas públicas e privadas cujos empregados são regidos pela Consolidação das Leis Trabalhistas (CLT). Adota-se o modelo teórico de desenho do trabalho, proposto por Morgeson e Humphrey (2006), visando preencher lacuna teórica acerca das percepções de teletrabalhadores sobre as características da tarefa, sociais e do contexto de trabalho. O objetivo desta pesquisa é analisar as percepções dos teletrabalhadores em relação às características da tarefa, sociais e de contexto de trabalho, bem como aos benefícios, às dificuldades e aos desafios associados ao regime de Teletrabalho em Tempo Parcial (TTP). Os dados foram extraídos a partir de 83 entrevistas individuais com servidores predominantemente do sexo feminino; casados; com especialização lato sensu; e com experiência de 1 ano em regime de TTP. Os resultados desta pesquisa indicam que as percepções dos participantes são predominantemente positivas em relação às características do trabalho, como, por exemplo, autonomia para organizar e realizar o trabalho; suporte social do gestor; uso de ferramentas de comunicação; e condições de trabalho em regime de teletrabalho. Os benefícios percebidos pelos entrevistados indicam maior autonomia e flexibilidade para organizar a própria rotina; redução dos deslocamentos; maior qualidade de vida e bem-estar; maior capacidade de concentração; conciliação trabalho-família-trabalho; maior produtividade e qualidade do trabalho; entre outros. As dificuldades e os desafios percebidos revelam preocupações relacionadas às características do contexto de teletrabalho e às características sociais do teletrabalho, como infraestrutura tecnológica provida pelo órgão (lentidão no sistema); fragilidade na gestão do teletrabalho; e autodisciplina. As demandas de aprendizagem percebidas pelos teletrabalhadores parecem reforçar algumas dessas dificuldades e desafios, tendo sido citados temas como conhecimentos de informática (hardware e software) e gestão do tempo. Este estudo apresentou contribuições teóricas, metodológicas e gerenciais ao aprofundar a investigação sobre teletrabalho, as quais permitem sugerir que as características da tarefa, sociais e do contexto de trabalho sejam consideradas pelos gestores que pretendem implantar o regime de teletrabalho ou aperfeiçoar um programa vigente, de modo a possibilitar um melhor ajuste para os que estão direta e indiretamente implicados na adoção da modalidade.Teleworking (TT) is a modality that allows workers to carry out their activities away from the organizational environment with the help of technological resources. The adoption of this work arrangement has been growing in Brazil and finds support in three legal frameworks which regulate TT in the Federal Executive and Judiciary Branches, as well as public and private companies whose employees are governed by the Consolidation of Labor Laws (CLT). This study adopted Morgeson and Humphey’s (2006) work design theoretical framework aiming to fill a theoretical gap regarding the teleworkers’ perceptions of the social, contextual and task characteristics of their work. The aim of this research is to analyze the teleworkers’ perceptions regarding both the social, contextual and task characteristics, as well as the benefits, difficulties and challenges associated to part-time telework arrangements (TTP). The data were collected from 83 individual interviews with mostly female employees who had lato sensu specialization and one year’s experience working in TTP. The results of this study show that the participants’ perceptions are predominantly positive regarding the characteristics of the work, such as the autonomy to organize and carry out their work; social support of the manager; use of communication tools; and working conditions in a telework arrangement. The participants’ perceived benefits include greater autonomy and flexibility to organize their own routine; reduced displacements; enhanced quality of life and well-being; greater concentration capacity; better work-family balance; increased productivity and quality of work; among others. The perceived difficulties and challenges reveal concerns related to the contextual characteristics of teleworking and to social characteristics such as the technological infrastructure provided (system sluggishness), management fragility, and self-discipline. The perceived learning demands by teleworkers seem to reinforce some of these difficulties and challenges, including themes such as computer skills (hardware and software) and time management. By deepening the investigation into teleworking, this study has made theoretical, methodological, and managerial contributions which suggest that the social, contextual and task characteristics of the work be taken into account by managers who intend either to implement a telework arrangement or to improve an existing program, in order to enable a better adjustment for those who are directly and indirectly affected by the adoption of this work modality

Too cold for invasions? Contrasting patterns of native and introduced ascidians in subantarctic and temperate Chile

10 páginas, 1 tabla, 2 figuras.We analysed the biodiversity of ascidians in two areas located in southern and northern Chile: Punta Arenas in the Strait of Magellan (53º latitude, subantarctic) and Coquimbo (29º latitude, temperate). The oceanographic features of the two zones are markedly different, with influence of the Humboldt Current in the north, and the Cape Horn Current System, together with freshwater influxes, in the Magellanic zone. Both regions were surveyed twice during 2013 by SCUBA diving and pulling ropes and aquaculture cages. Both artificial structures and natural communities were sampled. A total of 22 species were identified, three of them reported for the first time in Chilean waters: Lissoclinum perforatum, Synoicum georgianum, and Polyzoa minor. The first is an introduced species found here for the first time in the Pacific. No species occurred in both regions, highlighting the very different environmental conditions of subantarctic vs. temperate waters. In spite of exhaustive searches in aquaculture facilities and on artificial structures such as harbour docks and piers, no introduced species were found in the Punta Arenas area. Conversely, 5 out of 11 (45%) species found in northern Chile were introduced. The Coquimbo area has a history of ship traffic dating back at least 150 years, and cultures of native (e.g. scallop) as well as exotic species (e.g. abalone) have been deployed for ca. 35 years. Some of the introduced species, such as Ciona robusta (formerly C. intestinalis sp. A), constitute pests for scallop culture facilities in the area, causing serious losses to local farmers. It is surprising that the Punta Arenas zone, with a history of ship traffic dating back ca. 500 years and over 25 years of sustained mussel and salmon aquaculture activity, is apparently free from introduced species. The ascidian cover on artificial structures is high, but it is made up of native species such as Paramolgula sp., Cnemidocarpa verrucosa, or Polyzoa opuntia. It is hypothesized that cold waters (5 to 11ºC) are the determining factor hindering the development of introduced ascidians, which tend to be temperate-warm water species. The ongoing warming in the Southern Cone may change this picture and continued monitoring is strongly advised.This research was funded by CONICYT Chile (Grant 80122006). Additional funding was obtained by XT from the Spanish Government (project CHALLENGEN CTM2013-48163) and by JIC from University of Magallanes - UMAG/DI&P Grant PR-F2-01CRN- 12, CIMAR 18 & CIMAR 20 Fjords Chilean Navy, and GAIAAntarctic Project (MINEDUC-UMAG). RMR received a research grant from CNPq–National Counsel of Technological and Scientific Development (304768/2010-3).Peer reviewe

Ascidian fauna (Tunicata, Ascidiacea) of subantarctic and temperate regions of Chile

30 páginas, 15 figuras, 2 tablasWe studied the ascidian fauna from two zones located in subantarctic (Punta Arenas, latitude 53º) and temperate Chile (Coquimbo, latitude 29º). The different oceanographic features of the two zones, with influence of the Humboldt Current in the north and the Cape Horn Current System and freshwater inputs in the south, led to markedly different ascidian faunas. A total of 22 species were recorded, with no shared species across the two areas (11 species each). The new species Polyzoa iosune is described, Lissoclinum perforatum is found for the first time in the Pacific Ocean, and Synoicum georgianum and Polyzoa minor are new to the Chilean fauna. The populations of Ciona in the Coquimbo area (formerly attributed to Ciona intestinalis) correspond to the species Ciona robusta. A total of 35 Cytochrome oxidase (COI) sequences of the standard barcode region have been obtained for 17 of the 22 species reported.This research was funded by CONICYT Chile (Grant 80122006). Additional funding was obtained by XT from the Spanish Government (project CHALLENGEN CTM2013-48163) and by JIC from University of Magallanes: UMAG/DI&P Grant PR-F2-01CRN-12, CIMAR 18 & CIMAR 20 Fjords Chilean Navy, and GAIA-Antarctic Project (MINEDUC-UMAG). RMR received a research grant from CNPq–National Counsel of Technological and Scientific Development (304768/2010-3).Peer reviewe

Optimization of fourteen microsatellite loci in a Mediterranean demosponge subjected to population decimation, Ircinia fasciculata

The recovery potential of decimated populations of sponges will largely hinge on their populations' size retrieval and their connectivity with conspecifics in unaffected locations. Here, we report on the development of microsatellite markers for estimation of the population connectivity and bottleneck and inbreeding signals in a Mediterranean sponge suffering from disease outbreaks, Ircinia fasciculata. From the 220,876 sequences obtained by genomic pyrosequencing, we isolated 14 polymorphic microsatellite loci and assessed the allelic variation of loci in 24 individuals from 2 populations in the Northwestern Mediterranean. The allele number per locus ranged from 3 to 11, observed heterozygosity from 0.68 to 0.73, and expected heterozygosity from 0.667 to 0.68. No significant linkage disequilibrium between pairs of loci was detected. The 14 markers developed here will be valuable tools for conservation strategies across the distributional range of this species allowing the detection of populations with large genetic diversity loss and high levels of inbreeding

Plasticidad fenotípica de la esponja Callyspongia vaginalis (Porifera: Haplosclerida)

Sponge morphological plasticity has been a long-standing source of taxonomic difficulty. In the Caribbean, several morphotypes of the sponge Callyspongia vaginalis have been observed. To determine the taxonomic status of three of these morphotypes and their relationship with the congeneric species C. plicifera and C. fallax, we compared the spicule composition, spongin fiber skeleton and sequenced fragments of the mitochondrial genes 16S and COI and nuclear genes 28S and 18S ribosomal RNA. Phylogenetic analyses with ribosomal markers 18S and 28S rRNA confirmed the position of our sequences within the Callyspongiidae. None of the genetic markers provided evidence for consistent differentiation among the three morphotypes of C. vaginalis and C. fallax, and only C. plicifera stood as a distinct species. The 16S mtDNA gene was the most variable molecular marker for this group, presenting a nucleotide variability (π = 0.024) higher than that reported for COI. Unlike recent studies for other sponge genera, our results indicate that species in the genus Callyspongia maintain a high degree of phenotypic plasticity, and that morphological characteristics may not reflect reproductive boundaries in C. vaginalis.La gran plasticidad morfológica de ciertas esponjas dificulta una correcta clasificación taxonómica. En el Caribe, se han observado varios morfotipos de la esponja Callyspongia vaginalis a nivel de colores y formas. Con el fin de determinar su clasificación taxonómica, se muestrearon y analizaron tres morfotipos de C. vaginalis y sus especies congenéricas C. plicifera y C. fallax. Para cada muestra, se observó la composición espicular y del esqueleto dermal y se secuenciaron parte de los genes mitocondriales 16S y COI y parte de los genes ribosomales 28S y 18S. Los análisis filogenéticos con los genes ribosomales 18S y 28S confirmaron la posición taxonómica de las secuencias obtenidas. Ninguno de los marcadores genéticos utilizados reveló diferencias consistentes entre los tres morfotipos de C. vaginalis y C. fallax, y sólo C. pleicifera apareció en los análisis como una especie distinta. El gen mitocondrial 16S fue el marcador molecular más variable para este grupo, presentando una variabilidad nucleotídica (p = 0.024) superior a la descrita para COI. Nuestros resultados indican que las especies del género Callyspongia presentan una gran plasticidad fenotípica y que estas diferencias morfológicas no suponen barreras reproductivas para C. vaginalis