Scutellum Var Research Articles

Cell-Death Metabolites from Cocconeis scutellum var. parva Identified by Integrating Bioactivity-Based Fractionation and Non-Targeted Metabolomic Approaches.

Epiphytic diatoms growing in Mediterranean seagrass meadows, particularly those of the genus Cocconeis, are abundant and ecologically significant, even in naturally acidified environments. One intriguing aspect of some benthic diatoms is their production of an unidentified cell-death-promoting compound, which induces destruction of the androgenic gland in Hippolyte inermis Leach, 1816, a shrimp exhibiting protandric hermaphroditism, principally under normal environmental pH levels. The consumption of Cocconeis spp. by this shrimp is vital for maintaining the stability of its natural populations. Although many attempts have been made to reveal the identity of the apoptotic compound, it is still unknown. In this study, we strategically integrated a bioactivity-based fractionation, a metabolomic approach, and two different experimental avenues to identify potential apoptotic metabolites from Cocconeis scutellum var. parva responsible for the sex reversal in H. inermis. Our integrated analysis uncovered two potential candidate metabolites, one putatively identified as a lysophosphatidylglycerol (LPG) (16:1) and the other classified as a fatty acid ester. This is the first time LPG (16:1) has been reported in C. scutellum var. parva and associated with cell-death processes. These candidate metabolites mark substantial progress in elucidating the factors responsible for triggering the removal of the androgenic gland in the early post-larval phases of H. inermis.

Ocean Acidification Affects Volatile Infochemicals Production and Perception in Fauna and Flora Associated With Posidonia oceanica (L.) Delile

Communication among marine organisms are generally based on production, transmission, and interpretation of chemical cues. Volatile organic compounds (VOCs) can act as infochemicals, and ocean acidification can alter their production in the source organisms as well as the interpretation of the information they drive to target organisms. Two diatoms (Cocconeis scutellum var. parva and Diploneis sp.) and a macroalga (Ulva prolifera), all common epiphytes of Posidonia oceanica leaves, were isolated and cultured at two pH conditions (8.2 and 7.7). Their biomass was collected, and the VOCs produced upon wounding were extracted and analyzed using gas chromatography. Chemotactic reactions of invertebrates triggered by VOCs were tested using a static choice experimental arena and a flow-through flume system. Odor choice experiments were performed on several invertebrates associated with P. oceanica meadows to investigate the modification of behavioral responses due to the growth of algae in acidified environments. Complex patterns of behavioral responses were recorded after exposure to algal VOCs. This study demonstrated that a) ocean acidification alters the bouquet of VOCs released by diatoms and macroalgae and b) these compounds act as infochemicals and trigger peculiar behavioral responses in benthic invertebrates. In addition, behavioral responses are species-specific, dose-dependent, and are modified by environmental constraints. In fact, the static diffusion in choice arenas produced different responses as compared to flow-through flume systems. In conclusion, we demonstrate that in future marine environments higher CO2 concentrations (leading to a pH 7.7 by the end of this century) will modify the production of VOCs by micro- and macroalgae as well as the recognition of these infochemicals by marine invertebrates.

Vertical distribution of epiphytic diatoms in relation to the eelgrass Zostera noltii canopy biomass and height

Diatoms make an important contribution to the total primary production in Zostera beds. The study of the vertical distribution of diatoms in the canopy of Zostera noltii Hornemann 1832 and its relationship with the biomass and height of the host species was the goal of this paper.The Z. noltii canopy with a height of 39.2 ± 0.91 cm was divided into eight horizontal layers with a step of 5 cm. The mean biomass of the eelgrass canopy leaves per bottom area was 0.240 ± 0.091 kg dry weight (d.w.) m−2. On the leaves, stems, and rhizomes of Z. noltii, 34 diatom species belonging to 24 genera were found. In terms of relative cell density (43 ± 15.6%) and biomass (57.5 ± 15.2%), Cocconeis scutellum var. scutellum was the dominant species. In different layers of the canopy, the total abundance of diatoms and their biomass on Zostera per unit of its phytomass varied widely from 0.88·105 to 2.95·105 cells g−1 and from 0.24 to 2.10 mg g−1, respectively. The total abundance of diatoms and their biomass on Zostera leaves per bottom area covered by the canopy reached, on average, (54.879 ± 20.675)·106 cells m−2 and 0.332 ± 0.126 g m−2, respectively. The total mass of diatoms averaged 0.046 ± 0.0006% per wet weight of the aboveground part of Zostera. It is suggested that two factors play an important role in the distribution of diatoms in the horizontal layers of the Z. noltii canopy: the amount of the surface area available for settlement and its morphological characteristics.

Epiphytic diatoms on Gelidiales (Rhodophyta) from Gran Canaria (Spain)

ABSTRACT The composition and patterns of spatial and season variability of epiphytic diatom assemblages of five intertidal species of Gelidiales (Rhodophyta) from three sampling sites off Gran Canaria (Canary Islands, Atlantic Ocean) were investigated during summer (2007) and winter (2008) seasons using scanning electron microscopy (SEM). Dominant species included Cocconeis scutellum var. scutellum, C. scutellum var. posidoniae, Grammatophora oceanica, Lichmophora eherembergi, Navicula sp. and Tabularia fasciculata and these represented 78% of the total diatom assemblage on Gelidiales. Eight of the diatom taxa, Cocconeis maxima, Amphicocconeis debesii, Cocconeis convexa, C. neothumensis var. marina, C. scutellum var. scutellum, C. scutellum var. posidoniae, Gomphonemopsis obscura and Pseudohimantidium pacificum, found in the present study represent new records for the Canary Archipelago. These species showed two distinct patterns of zonation, one in relation to their position at the intertidal area and the other relative to position on the host thalli. Although the vertical distribution of host thalli at the intertidal zone was important when considering the assemblage structure of epiphytic diatoms, the results showed that the cell abundance distribution changed more significantly when considering season rather than spatial distribution. Moreover, even though morphology of host thalli was not a determining factor, their aggregation mode had a significant influence on the abundance and distribution of microalgae. Finally, considering the growth forms of diatom communities, adnate diatoms were more abundant in turf than in clump species.

Colonization of fiber-glass plates by benthic diatoms from subtidal sediment off the coast of Yucatan, Mexico

Benthic diatoms thrive in many types of substrata, either natural or alternative such as the surfaces of large and small boats in which colonization by micro- and macro-organisms (fouling) represents an important economic and environmental problem. Addressing this issue is difficult given the scarce information on benthic diatoms one of the main micro-fouling settlers. Thus, this study aimss to describe the colonization process by diatoms on fiber-glass plates and construct a floristic list of the diatom taxa growing both on these surfaces and their likely source the subtidal bottom sediment. The study was conducted at a coastal site off Telchac, Yucatan (Mexico), where fiber-glass plates were laid over the bottom sediment at a depth of 10 m during four months. Sampling was carried out over successive spaced points in time (1st, 3rd, 4th, 8th, 12th and 16th weeks) after the initial immersion of the plates. At the end 88 taxa growing on the plates and sediment were identified, the most abundant ones being Cocconeis scutellum var. parva, Cymatosira lorenziana, Paralia sulcata, Delphineis surirella var. australis, Actinoptychus senarius, Grammatophora marina and Shionodiscus oestrupii. Included were two new records for the Mexican littorals: Cocconeis latestriata and Navicula uniseriata. Overall species composition differs from previous studies in the area, to which forty-seven taxa are added here, increasing their total number to 210. Our results show the changes in the species composition of the taxocenosis over time, during the initial colonization period, i.e., the period during which there is no intense competition for space. The high percentage of common species between the plates and sediment (similarity) support the hypothesis that subtidal sediment is the most likely source for diatoms colonizing the plates.

Cocconeis scutellum var. ornata Grunow and C. interrupta Grunow from the historical Grunow collection in Vienna (sample 131)

Cocconeis scutellum var. ornata Grunow (1868) was originally described and illustrated in Grunow (1862) as Rhaphoneis marginata Grunow, and later illustrated by Grunow in Van Heurck (1880). Several further illustrations were produced by diverse authors, i.e., drawings and photographs from light microscopy and more recently using the scanning electron microscope (SEM), yet all done without checking the holotype. Material from a small historical mica-slide from the Grunow collection in Vienna, capsule N° 131–6, marked as containing C. scutellum var. ornata, was examined with the SEM and given a new status for this taxon, renamed as Cocconeis pseudornata Riaux-Gobin, Igersheim, Ector et Witkowski stat. et nom. nov. Herein, remarks are provided for the intricate history of the latter taxon. Cocconeis interrupta Grunow, mentioned by Grunow in his accession book as present in sample 131, is examined with the SEM and an emended description is provided.

Epilithic diatom communities from areas of invasive Caulerpa species (Caulerpa taxifolia and Caulerpa cylindracea) in the Adriatic Sea, NE Mediterranean

Epilithic diatom community structures are compared among three locations of the eastern Adriatic Sea coast (Croatia), in the presence of two different invasive Caulerpa species, C. taxifolia and C. cylindracea, which have spread rapidly in the Mediterranean in the last decades. Forty samples were taken seasonally at three sites (island of Hvar, island of Mljet, and Dubrovnik) between November 2008 and October 2010. Light and electron microscopy examinations were used for qualitative analysis. Altogether 310 epilithic taxa belonging to 65 genera were identified. The highest number of these taxa belonged to Mastogloia (48) and Amphora (32), followed by Diploneis (24), Nitzschia (23), Navicula (22), and Cocconeis (19). A similar seasonal shift in growth form structure was observed for epilithic communities at the three sampling sites, where the number of erect group diatoms doubled (Hvar, Mljet) and tripled (Dubrovnik) in spring. Apart from erect forms, Dubrovnik and Mljet were characterised by adnate forms, while Hvar was characterised by tube-dwelling forms. The highest values of the Shannon-Wiener Diversity Index were recorded in autumn and ranged from 5.26 to 5.34. ANOSIM tests performed on species relative abundance data confirmed that the diatom communities differed significantly between the sampling sites, and that the differences were correlated with the presence of the two species of invasive macroalgae (Hvar – area of C. taxifolia; Mljet and Dubrovnik – areas of C. cylindracea). As revealed by SIMPER analyses, the group of taxa contributing the most to variance between diatom assemblages from sites of different invasive alga included Cocconeis scutellum var. scutellum, Rhopalodia pacifica, Navicula ramosissima, and Berkeleya rutilans. Although the spatial variation in communities may also reflect the effects of unmeasured environmental variables, the results suggest the possible influence of invasive seaweeds of the genus Caulerpa which may affect the habitat by competing with autochthonous algae. This study contributes to the knowledge of diatom diversity both at regional and at broader scales in these challenged environments.

Biodiversity and ecology of epilithic diatoms in the Agnéby River, Ivory Coast

The ecology and taxonomy of the epilithic diatom flora of the Agnéby River, Ivory Coast were studied in 2012. Ten sites were investigated and diatoms were sampled on glass slides immersed for a period of 30 days during the wet and dry seasons. Physico-chemical parameters were measured at each site while sampling diatoms. Five taxa were largely dominant: Planothidium comperei CE Wetzel, N’Guessan and Tison-Rosebery, Eolimna minima (Grunow) Lange-Bertalot, Planothidium piaficum (JR Carter and Denny) CE Wetzel and Ector, Cocconeis schroederi Foged and Cocconeis scutellum var. parva (Grunow in Van Heurck) Cleve. Electrical conductivity, temperature, dissolved oxygen, nitrite and phosphorus were found to influence the distribution of taxa.

Relationship between marine epilithic diatoms and environmental variables in oligotrophic bay, NE Mediterranean

The taxonomic composition and structure of a marine epilithic diatom community were sampled from the bottom of the two sites at monthly intervals from January to December 2011 in the small semi-enclosed oligotrophic Neum Bay in Bosnia and Herzegovina (Middle Adriatic). Altogether, 264 diatom taxa (species and infraspecific taxa) within 69 genera were identified. Among them, 149 and 203 taxa occurred in samples from the shallow (0.5 m depth) and deep (8 m depth) sites, respectively. The monthly distribution of most of the diatoms was irregular and high numbers of sporadic taxa were found. SIMPER analysis indicated that the difference between shallow and deep sites could be largely attributed to the frequently recorded diatom taxa and those with high percentage abundances. They were Halamphora coffeiformis, Caloneis excentrica, Cocconeis scutellum var. scutellum, Licmophora flabellata, Licmophora gracilis, Licmophora sp., Navicula abunda, Rhabdonema adriaticum, and Striatella unipunctata. Canonical Correspondence Analysis (CCA) showed that temperature, oxygen saturation (O2/O2′), silicate concentration (SiO4), and salinity were the most important factors influencing diatom community structure in the bay.

Cocconeis scutellum var. parva (Bacillariophyceae) re-examination and typification

Electron microscope (EM) is essential for the morphological description of small taxa, but also reveals taxa hitherto grouped under the same name although presenting marked ultrastructural differences: e.g., Cocconeis scutellum var. parva. The latter taxon has been interpreted differently by authors, while no type has been examined since the original description. A slide from the Grunow’s collection in W, annotated by Albert Grunow as containing C. scutellum var. parva was examined and detailed for the first time. This slide allowed for a more precise definition of C. scutellum var. parva and is here designated as lectotype. This paper analyzes the history of C. scutellum var. parva and attempts to exclude definitions that are too far from the original drawings and from the lectotype illustration. A tropical–population from Rodrigues Island (Indian Ocean) composed of small specimens with stria densities significantly denser than observed on the nominate variety, is here described as an epitype of C. scutellum var. parva and is illustrated with SEM. A small taxon from Tahiti Island (South Pacific Ocean), seemingly close to C. scutellum var. parva, has unique raphe valve valvocopula with cupuliform papillae. The latter specificity is considered a simple variation and may illustrate the range of morphological variability admitted for a taxon.

Diatomeas de Texcala, Puebla

Se registran 57 taxa específicos e infraespecíficos pertenecientes a 17 géneros de diatomeas provenientes de un arroyo en Texcala, cerca de Ia Ciudad de Tehuacán, Puebla. Seis taxa que no habían sido registrados previamente para México se ilustran y se describen con anotaciones de algunas características ecológicas y su distribución geográfica. Los nuevas registros son: Cocconeis scutellum var parva (Grunow) Cleve, Cymbella turgidula Grunow, Navicula recens Lange Bertalot, Pleurosigma salinantm (Grunow), Nitzschia calida Grunow, Nitzschia constricta (Kützing) Ralfs.

Cocconeis Ehrenberg (Bacillariophyta), a genus dominating diatom communities associated with Posidonia oceanica Delile (monocotyledons) in the Mediterranean Sea

A fine-scale analysis of diatoms associated with Posidonia oceanica in selected locations was carried out along a longitudinal gradient in the Mediterranean Sea (00°21′W–27°07′E) to investigate the composition and diversity of epipthytic communities and to determine the distribution and relative importance of their components with special reference to the most common and abundant genus, Cocconeis. Posidonia oceanica was sampled twice (once per year for two years) at 19 sites. At each site, forty samples of P. oceanica shoots separated by several metres were taken. Epiphytic diatom communities were studied with SEM (scanning electron microscopy) and TEM (transmission electron microscopy). Fifty-two diatom genera were identified. In every studied case, adnate Cocconeis spp. cells dominated the community. Among 32 Cocconeis species and varieties found, recently described C. neothumensis var. marina and C. scutellum var. posidoniae were almost always the most numerous. The structure of Cocconeis assemblages changed across the various geographic regions both in terms of the species’ presence–absence and their relative abundance. In general, the most abundant species appeared to be broadly distributed, while less abundant species had a more distinct biogeographic pattern. In the course of this study, several Cocconeis species described as Indo-Pacific were found in the Mediterranean Sea for the first time. Potential relationships between different Cocconeis species and genetically distinct P. oceanica populations are discussed.

Growth of Benthic Diatom Cocconeis scutellum var. parva, A Suitable Food for Post-larval Abalone

Growth of Benthic Diatom Cocconeis scutellum var. parva, A Suitable Food for Post-larval Abalone

A comparative study of Cocconeis scutellum Ehrenberg and its varieties (Bacillariophyta)

Abstract We present an ultrastructure-based revision (using light and electron microscopy) of the type species of the genus Cocconeis, C. scutellum var. scutellum, and four often-mentioned but poorly described, morphologically related varieties: C. scutellum var. baldjikiana, C. scutellum var. clinoraphis, C. scutellum var. parva, C. scutellum var. posidoniae. In addition, we introduce three new taxa, C. scutellum var. gorensis var. nov., C. scutellum var. posidoniae f. decussata f. nov. and C. scutellum var. sullivanensis var. nov. The taxonomic relationships between these varieties and the remaining validly described C. scutellum varieties are analyzed on the basis of their ultrastructural differences. We also provide additional information on the geographical distribution of all analyzed C. scutellum taxa.

NEW TAXONS OF BENTHIC DIATOM ALGAE OF THE TILIGUL ESTUARY (THE NORTH-WESTERN PART OF THE BLACK SEA COAST)

181 species and taxons of the diatom algae were revealed in benthos of the Tiligul Estuary. 74 of them are represented for the reservoir for the first time and 25 for the first time for the estuaries of the north-western part of the Black Sea. Cocconeis scutellum var. tiligulicus Kovtun var. nov. and Fallacia gusliakovi Kovtun sp. nov. are described as new species for science. The original micrographs are presented.

Marine taxa of Cocconeis on leaves of Posidonia oceanica, including a new species and two new varieties

Eight Cocconeis Ehrenberg taxa (species and varieties) epiphytic on the leaves of Posidonia oceanica (L.) Delile were studied by scanning and transmission electron microscopy. Samples of Posidonia oceanica were collected throughout the year from seagrass meadows around the island of Ischia (Gulf of Naples, Italy). On the basis of some peculiar ultrastructural characteristics of the valve areolation, a new species, Cocconeis multiperforata sp. nov., and two new varieties, C. neothumensis var. marina var. nov., and C. scutellum var. posidoniae var. nov., are described. Ultrastructural analysis also revealed new morphological characteristics in C. britannica Naegeli in Ku$ tzing and C. maxima (Grunow) Peragallo & Peragallo, and confirmed observations of other authors for C. molesta var. crucifera Grunow, C. pellucida Grunow in Rabenhorst and C. stauroneiformis (Rabenhorst) Okuno. Our observations on the abundance of the different species provide new information on their distribution and ecology.

Survival and growth rates of post-larval abalone Haliotis discus hannai fed conspecific trail mucus and/or benthic diatom Cocconeis scutellum var. parva

The settlement rate and growth rate of post-larval Haliotis discus hannai were compared in the laboratory when raised on the following three experimental substrata. (1) Mucus: trail mucus of juvenile H. discus hannai (3 cm in shell length); (2) diatom: monoculture of the benthic diatom Cocconeis scutellum var. parva; (3) diatom and mucus: C. scutellum var. parva coated with trail mucus of juvenile abalone. The mean percentage of larvae that settled were 48.7 on mucus, 98.0 on diatom, and 97.3% on diatom and mucus substrata. All post-larval abalone that settled on the mucus substratum died by the end of the third week, with a mean shell length during the third week of 711.9 μm. Individuals on the diatom substratum died by the end of the second week, with a mean shell length during the second week of 481.6 μm. Post-larvae on the diatom substratum and on the mucus substratum did not reach 800 μm in shell length; the size at which they are able to utilize the cell contents of C. scutellum var. parva. In contrast, on the diatom and mucus substratum, 70.0% of the individuals survived to the end of the experimental period (4 weeks). Individuals on the diatom and mucus substratum grew well over the entire experimental period and reached approximately 1.4 mm in shell length 4 weeks after settlement. Post-larvae reared on the diatom and mucus substratum grew to more than 800 μm by feeding initially on the trail mucus of conspecific juveniles, which was probably supplemented with extracellular diatom mucus and decomposed cells of the diatom. Once they reached about 800 μm, they were able to access diatom cell contents.

MORPHOLOGICAL VARIATION OF THE ATTACHED DIATOM:COCCONEIS SCUTELLUMVAR.SCUTELLUM: (BACILLARIOPHYCEAE)1

ABSTRACTThe morphology and sexual reproduction of the attached diatom Cocconeis scutellum Ehr. var. scutellum have been investigated using field and culture materials. The diatom grew well at 14–22° C and in a medium using enriched full strength seawater or 50% diluted seawater. One gamete was formed without cytokinesis in a gametangium and one auxospore arose from paired gametangia. The size of gametangia and initial cells were 17.8–29.9 μm and 43.3–59.5 μm, respectively. Valve width decreased linearly with decreasing valve length. The regression coefficient between them was invariable with the change of the environment. The transapical striation densities were 7–12 and 7.5–13.5 in 10 μm in araphid and raphid valves, respectively. The density showed a tendency to increase with decreasing valve length in both valves. The densities in both valves, except the small araphid valve, are invariable with the change of the environment. The relationships between valve length and width, and between valve length and striation density have been compared with those of taxa allied to C. scutellum var. scutellum. It is concluded that C. scutellum var. scutellum, as usually delimited, is a heterogenous taxon.

Seasonal ecology of littoral epiphytic diatoms on Great Cumbrae Island.

Summary 216 species of diatoms have been found epiphytic on common intertidal marine algae from Great Cumbrae Island, Firth of Clyde, Scotland. Green and red algae had larger epiphytic floras than brown algae. Cocconeis spp. (especially C. scutellum var. scutellum) were common and abundant, and the endophytic Navicula endophytica was found in large numbers in fucoid algae. Similar epiphytic floras were observed on Cladophora rupestris, Polysiphonia lanosa, Gigartina stellata, and Palmaria palmata, but that on Enteromorpha intestinalis was quite distinct.

The annual pattern of the diatoms in the epiphyton of eelgrass (Zostera marina L.) at Roscoff, France

The epiphytic diatom flora living on eelgrass, Zostera marina L., at Roscoff (France) has been observed during a whole year, from March 1976 to March 1977. The structure of this epiphyton has been analysed by investigating the species richness and the relative abundance of the taxa concerned. The study recorded 199 diatom taxa, representing 48 genera.The epiphytic diatom association is characterized by Cocconeis scutellum Ehrenb., C. scutellum var. parva Grun. in Cleve and Synedra investiens W.Sm., of which C. scutellum and its variety are dominant throughout the year.Differences in community structure between the diatom assemblages in the spring, summer, autumn and winter were most distinct as a consequence of the ephemeral character of the substrate. It appears that chlorine content and temperature have no direct effect on the species richness of the diatom association on eelgrass leaves. The seasonal variation in the epiphyton seems to be more closely related to insolation patterns and characteristics of the substrate and this relationship is discussed.