Genus Melosira Research Articles

Revision of the non-marine centric diatom flora (Bacillariophyta) of the sub-Antarctic Campbell Island (southern Pacific Ocean) with the descriptions of five new species

During a survey of the moss-inhabiting diatom flora of the sub-Antarctic Campbell Island, located in the southern Pacific Ocean, several unknown centric diatoms were observed that could not be identified using the currently available literature. Detailed light and scanning electron microscopical observations and comparisons with the characters of several species of Melosira, Angusticopula, Ferocia and Arcanodiscus worldwide indicated that five of them should be described as new to science: Angusticopula cosmica Goeyers & Van de Vijver sp. nov., Arcanodiscus crawfordianus Goeyers & Van de Vijver sp. nov., A. indistinctus Goeyers & Van de Vijver sp. nov., A. saundersianus Goeyers & Van de Vijver sp. nov. and Ferocia houkiana Goeyers & Van de Vijver sp. nov. A sixth species, Angusticopula chilensis, was illustrated for the first time using SEM and as a result is considered to differ sufficiently from A. dickiei to warrant epitypification as A. chilensis. The new species were first described in genera that formerly were included within the genus Melosira. All six species are morphologically characterized and compared with similar species within their respective genera. Their presence and distribution on Campbell Island are discussed based on the observations made in the available samples.

Melosira jeanbertrandiana, a new Melosira species (Bacillariophyceae) from the sub-Antarctic region

ABSTRACTDuring a survey of the soil diatom flora of the sub-Antarctic Ile de la Possession (Iles Crozet), located in the southern Indian Ocean, an unknown Melosira species was found that could not be identified using the currently available literature on the genus. The species is described as Melosira jeanbertrandiana sp. nov. based on detailed light and scanning electron microscopy observations. The new species is characterized by a relatively high mantle, the presence of several marginal rings of acute, never bifurcating spines and a series of eight rimoportulae near the central area with several others scattered over the rest of the valve face and mantle. The girdle comprising several large, ligulate open copulae and the position of the rimoportulae clearly place this new species within the genus Melosira C.Agardh. The species was observed in bare, moist soil in scratches in cliffs bordering the ocean where the influence of sea spray is obvious. The description of this new species further increases the number of species of the Melosirales compared to other centric freshwater diatoms which are infrequently found on the sub-Antarctic islands.

Bioindicator for environmental water quality based on saprobic and diversity indices of planktonic microalgae: a study case at Rawapening lake, Semarang district, Central Java, Indonesia

Over the last twenty years, the aquatic environment of Rawapening Lake has been negatively impacted by increasing rates of sedimentation and rising levels of soluble organic materials. The uncontrolled growth rate of hyacinth and other aquatic plants, and the rapidly increased implementation of traditional fish cages are believed to be the main contributing factors, resulting in degraded water quality. Dynamic structure of phytoplankton can be used as a bioindicator. This study is aimed at understanding the phytoplankton community in Rawapening Lake and assessing the water quality based on saprobic and diversity indices. A purposive random sampling method was used to determine four sampling locations. The data were analyzed with the saprobic index, Shanon-Wiener diversity index, and domination index. The result of the study shows that a substantial amount of phytoplankton were dominated by the genus Melosira sp., Aulacoseria granulosa, Oscillatoria sp., and Synedra sp., with low to moderate diversity index values. The quality of the Rawapening Lake water environment based on the saprobic index value was categorized as β meso-Oligosaprobic, indicating very mild to light pollution.

Two new centric diatoms (Bacillariophyta) from the sub-Antarctic region

During a survey of the limno-terrestrial diatom flora of the sub-Antarctic region, two unknown melosiroid diatom taxa were observed in several shaded, damp cave (moss and soil) samples from Heard Island and Ile de la Possession, the main island of the Crozet Archipelago. Comparison with already known species from the genus Melosira and the recently described genera Arcanodiscus, Angusticopula and Ferocia, resulted in the description of both new taxa based on detailed light and scanning electron microscopy. A first species was described as Ferocia subantarctica sp. nov. and can be distinguished based on its numerous, narrow girdle bands, relatively weakly domed valves, a limited number of well-developed spines and a rather large, hyaline central area. The second species, Arcanodiscus desmetianus Van de Vijver sp. nov., can be recognized based on its solitary frustules, a series of parallel ridges surrounding the mantle and a hyaline central area that is only less than 50% of the total valve diameter. Both taxa are morphologically and ecologically characterized and compared with all known melosiroid taxa worldwide.

Melosira (Diatomeae) taxa from the Iguaçu River in southern Brazil

Abstract The study of the genus Melosira in plankton samples from the lower Iguaçu River revealed the presence of four taxa: Melosira undulata (Ehrenberg) Kützing var. undulata, M. undulata var. normanni Arnott, M. varians C. Agardh and M. muscigena Iwahashi. We present illustrations of the frustules using light microscopy (LM), descriptions, and comments about the morphology of the four taxa. The analysis of Melosira muscigena under scanning electron microscopy revealed unprecedented details of the ultrastructure, such as the shape and distribution of the rimoportulae at the valve mantle. This is the first record of Melosira undulata var. undulata and the second of M. muscigena in Brazil.

Marine Benthic Diatoms Contain Compounds Able to Induce Leukemia Cell Death and Modulate Blood Platelet Activity

In spite of the high abundance and species diversity of diatoms, only a few bioactive compounds from them have been described. The present study reveals a high number of mammalian cell death inducing substances in biofilm-associated diatoms sampled from the intertidal zone. Extracts from the genera Melosira, Amphora, Phaeodactylum and Nitzschia were all found to induce leukemia cell death, with either classical apoptotic or autophagic features. Several extracts also contained inhibitors of thrombin-induced blood platelet activation. Some of this activity was caused by a high content of adenosine in the diatoms, ranging from 0.07 to 0.31 μg/mg dry weight. However, most of the bioactivity was adenosine deaminase-resistant. An adenosine deaminase-resistant active fraction from one of the extracts was partially purified and shown to induce apoptosis with a distinct phenotype. The results show that benthic diatoms typically found in the intertidal zone may represent a richer source of interesting bioactive compounds than hitherto recognized.

OBSERVATIONS ON TAXA OF MELOSIRA SENSU LATO AMONG THE SLIDES FROM THE GRUNOW DIATOM COLLECTION IN VIENNA (AUSTRIA). PART 1

The taxa belonging earlier to the diatom genus Melosira from slides in the Granow collection at the Natural History Museum in Vienna, were investigated using the light microscope (LM). Raw material related to several slides were also found and observed using the scanning electron microscope (SEM). According to valve morphology some were found to belong to other taxa and so several new combinations are given. This contribution deals with taxa that are mostly neglected in contemporary literature and also brings some old names back into general use. Several Aulacoseira taxa are presented here showing more valve pattern variability therefore emending LM and SEM-pictures presented by other authors.

Feeding ecology of Liza ramada (Risso, 1810) (Pisces, Mugilidae) in a south-western estuary of Portugal

The feeding activity of the Liza ramada population inhabiting the Mira estuary (Portugal) is reduced during the winter and summer months. At the beginning of the spawning migration (i.e. November) an increase in the amount of food ingested was noticed. In the upper estuary, the feeding behaviour is independent of the tidal cycle, although there is some evidence of a daily rhythm in the food consumption rate, with a reduction during the night. No significant correlation was found between the quantity of particulate organic matter and the concentration of microalgae present in the stomach contents, and it seems that the bulk of the organic matter ingested by the thin-lipped grey mullets comes from a different origin than planktonic or benthic microalgae. The L. ramada population showed a positive selection for sediment particles between 55 and 250 μm in diameter. In general, the diet composition of this species showed a low diversity of food items. A total of 52 food items were identified in the stomach contents, the Bacillariophyceae being the dominant group. The genera Melosira and Ciclotella were the most common and abundant food items, although the genera Navicula, Nitzschia and Surirella were also classified as preferential food items. It was found that the volume of ploughed sediment that resulted from the feeding activity of the thin-lipped grey mullets, and the correspondent disturbed area increased exponentially with the length of the fish.

Clarification for Modifying 3 Common Phytoplankton Genera Names

根据近年来国外文献所涉及的藻类分类学研究进展着重解释了蓝藻门的颤藻属和硅藻门的直链硅藻属和针杆藻属的一些浮游种类的学名变更情况同时介绍了国际上最新的蓝藻门颤藻目和硅藻门的分类概况.根据Anagnostidis和Komárek的分类原颤藻属的大部分浮游种类进入了新属[浮游蓝丝藻属](Planktothrix)其他种类则分别属于[湖生蓝丝藻属](Limnothrix)、胶鞘藻属(Phormidium)和现在的颤藻属(Oscillatoria)等多个颤藻目的类别.根据Krammer和Lange-Bertalot的分类原直链硅藻属的浮游种类进入了新属[浮生直链藻属](Aulacoseira),另外的种类归属于Orthoseira、Ellerbeckia和现在的直链硅藻属(Melosira)等硅藻类别中;原针杆藻属的浮游种类并入脆杆藻属(Fragilaria),其他种类进入菱形藻属(Nitzschia)、双尖菱板藻属(Hantzschia)和现在的针杆藻属(Synedra)中.;Based on the recent international publications, this study explained the modification of taxonomic name in three common phytoplankton genera. The new classification systems of Oscillatoriales and Bacillariophyceae were also introduced. According to the taxonomy of Anagnostidi & Komárek (1988), the former cyanobacteria genus Oscillatoria was split up. Most of the planktonic species of this group can now be found in two new genera Planktothrix and Limnothrix. About 70 other species in this group were shifted into the genus Phormidium. According to the taxonomy of Kramme and Lange-Bertalot (1991), all the planktonic species of the former diatom genus Melosira formed a new genus Aulacoseira. Some other species in this group were moved into the genera Orthoseira and Ellerbeckia. Most of the planktonic species of the former diatom genus Synedra were altered back to the genus Fragilaria. Some other species can now be found in the genera Nitzschia and Hantzschia.

Survey for microalgae and cyanobacteria in a drinking-water utility supplying the city of Florence, Italy

The occurrence of algae was investigated in surface water of the Arno river and in a drinking-water treatment utility serving the city of Florence. Throughout the 12 months monitoring period, raw water and treated water samples were collected and analysed for the number and species of microalgae and cyanobacteria; settled and filtered water samples were only examined for counts of organisms. Chlorophyll concentrations, temperature, pH, turbidity, flow rate and other indicators of surface water pollution were measured in raw water samples. Microalgae, mainly diatoms (46.1%, with a predominance of the genus Melosira ) and green algae (35.1%: non flagellate 30.7%, green flagellate 4.4%) were constantly found in river water samples. Cyanobacteria were rarely detected except in summer, mainly of genera Oscillatoria and Anabaena . In treated water only depigmented and inactive algal cells, mainly of green algae, were detected for which the treatment procedure was found to be less effective. The average algal removal by drinking-water treatment resulted in 97.4% for all samples and in 98.3% when significant algal concentrations were present in raw water. The combination of chlorine dioxide and coagulants resulted in a removal of 90.1%.

Qualitative and quantitative investigations of phytoplankton in Lake Ringsjön, Scania, Sweden

The algal record from Lake Ringsjon covers a period of more than 100 years. Towards the end of the 19th century, the lake had a well-functioning commercial fishery, when a brownish mess began to appear in the water, clogging-up the fishing nets and making fishing difficult. This was the first record of algal problems in the lake. Following complaints from the fishermen, the algal flora was investigated and the mess was stated to be a mass development of diatoms belonging to the genus Melosira (Aulacoseira). Diatom maxima then appeared regularly in spring and autumn, whereas blue-green algae only occurred occasionally and in low abundances. Between 1900 and 1950, nutrient concentrations slowly increased in the lake. Algal blooms of Anabaena lemmermannii and Gloeotrichia echinulata began to appear in summer. Between 1960 and 1980, the lake developed into a hypertrophie status with extensive blooms of blue-green algae from May to October, including high biomasses of mainly Microcystis spp. This severe pollution started with increased usage of the lake, increased tourism and recreation, intensified farming with the introduction of artificial fertilization, and also the diversion of sewage water from a sewage treatment plant. In 1968, cattle death was reported and in 1981, algal toxicity was verified by mouse bioassay. After a period of extremely poor water quality, the lake began to show signs of improvement as a result of the nutrient and fish reduction programmes. The very heavy blooms of blue-green algae decreased and the duration of blooms became shorter. The Microcystis species were to a certain extent replaced by Anabaena and Aphanizomenon species, and biodiversity of algae increased. With respect to the algal community, the lake has improved considerably, but is still eutrophic and suffers summer blooms of toxic blue-green algae.

Seasonal signals in Lake Malawi sediments

The sedimentary record of Lake Malawi, one of the large rift valley lakes of east Africa, contains thick sequences of biologically undisturbed, finely laminated muds and silts. Laminated sequences were recovered in cores from the extensive diatom ooze and silty diatom clay facies of the lake basin that is permanently anoxic below 250 m. The sequences consist of light‐dark laminae couplets with average thickness of 1 mm. The light laminae are completely dominated by the diatom genus Melosira with a relatively minor contribution from the genus Stephanodiscus. The dark laminae consist of 50% diatoms (equal proportions of Melosira and Stephanodiscus, few Nitzschia, and occasional littoral diatom genera) and 50% terrestrial plant debris, mineral grains, and fine clay and organic material. Based on a 210Pb and 14C calculated sedimentation rate of 1 mm yr−1 for Lake Malawi basin sediments and the well‐defined seasonal variations in fluvial input and diatom productivity levels, our data suggest that the lamination couplets are annual varves, representing biannual sedimentation sequences. The light laminae result from diatom blooms occurring during the dry, windy season (April–October) when the upper 250 m of the lake is well‐mixed, localized upwelling occurs, and the epilimnion becomes enriched with nutrients. The dark laminae represent sedimentation in the rainy, low‐wind velocity season (November–March) when runoff and allochthonous terrestrial input are at a maximum and primary productivity is at a minimum.

Cavernosa kapitiana, a new diatom genus and species from Kapiti Island, New Zealand

The type species of the new genus Cavernosa kapitiana from Te Rere Stream, Kapiti Island, New Zealand is described. Studies of its structure and ultrastructure have been made by Light Microscopy (LM) and Scanning Electron Microscopy (SEM). Initially it was proposed to assign. C. kapitiana to the genus Melosira but several prominent and constant morphological features separate it from that genus as discussed below

Freshwater diatom influx in intertropical Atlantic: Relationships with continental records from Africa

Diatom assemblages from modern West African rivers and from lacustrine sediments subjected to deflation represent the present-day sources of continental diatoms to the sea. Diatom productivity in large rivers is high, especially for the genus Melosira. Windblown diatoms derive mainly from the central and northern Sahara (summer dust plume) where saline chloride-water assemblages are widespread, or from the southern edge of the Sahara (winter dust plume) where Melosira-rich assemblages of dilute water predominate. Freshwater diatom peaks in Atlantic cores may reflect (1) phases of increased river influx, correlated with humid episodes on the continent or (2) phases of enhanced deflation and wind transport during arid episodes (the single hypothesis for fine sediments from mid-ocean sites). Genus Melosira dominates the freshwater assemblages of many modern and fossil marine samples, whatever the transport agent is. Therefore, it is not an accurate paleoclimate indicator by itself, but associated taxa may provide information on the environmental and geographical origin of the displaced diatoms. This tentative approach shows that freshwater diatoms in Atlantic cores may be a good tool for reconstructing paleoclimates and for establishing continent-ocean correlations if species analyses are made and if the continental distribution of the taxa encountered is considered.

Diatom, contributors of coralloid speleothems, from Togawa-Sakaidani-Do Cave in Miyazaki Prefecture, Central Kyushu, Japan

Coralloid speleothems are commonly distributed in Togawa-Sakaidani-do Cave in Miyazaki Prefecture, Central Kyushu, but their speleological study has not heretofore been achieved. Light and scanning microscopes analyses revealed that coralloid speleothems consist of alternating layers of diatom colonies, detrital minerals and clay. Electron microprobe analysis shows coralloid speleothems to be silicious. This paper asserts that diatom (genus Melosira) is one of the important contributors to siliceous coralloid speleothems in the threshold zone at non-calcareous caves.

Nomenclatural Changes among Some Kansas Diatoms

Recent work on the diatoms of Kansas, as part of the algal survey initiated by the State Biological Survey of Kansas in 1977, has revealed several nomenclatural problems. Six generic transfers, two in the genus Melosira to Aulacosira and four in the genus Amphiprora to Entomoneis were deemed necessary in the course of these studies and are reported as follows: Aulacosira granulata var. angustissima forma spiralis (Hust.) comb. nov.; A. ikapoensis var. minor (Choln.) comb. nov.; Entomoneis paludosa var. duplex (Donkin) comb. nov.; E. paludosa var. hyperborea (Grun.) comb. nov.; E. paludosa var. borealis (Grun.) comb. nov.; E. paludosa var. punctulata (Grun.) comb. nov. Preserved samples from which material was obtained for this study are on deposit at the State Biological Survey, Lawrence, Kansas. Voucher slides have been deposited in the General Collection, Diatom Herbarium, The Academy of Natural Sciences, 19th & The Parkway, Philadelphia, Pennsylvania 19103. Recent studies on the morphology of various diatoms previously assigned to the genus Melosira Ag. (e.g., Crawford, 1979) have essentially confirmed the earlier speculations of Ross and Sims (1973) that the M. granulata group should be removed from Melosira and placed in a separate genus. Simonsen (1979) elected to place this group in the genus Aulacosira (as Aulacoseira ) Thwaites and designated A. italica (Ehr.) Simons as the type of the genus. The Aulacosira group is characterized by having all loculi with their foramina on the outside of the value and the cribra on the inside. While Simonsen (op. cit.) included 59 taxa in his revision, he failed to include Melosira granulata var. angustissima forma spiralis Hust. This form was reported as occurring in Kansas by Williams et al. (1978) and erroneously attributed to O. Miiller. It is therefore appropriate to initiate the following transference:

VALVE AND BAND MORPHOLOGY OF SOME FRESHWATER DIATOMS. III. PRE‐ AND POST‐AUXOSPORE FRUSTULES AND THE INITIAL CELL OFMELOSIRA ROESEANA1

ABSTRACTFrustules of a clonal culture ofMelosira roeseanaRabenh. were examined with light and scanning electron microscopy. Vegetative valves in the post‐auxospore (full size) stage exhibit a larger width/length ratio than those in the pre‐auxospore (size‐reduced) stage. Cells form chains by linking spines of adjacent valves which occur at the periphery of the valve face‐mantle junction. Three or jour large pores occur at the center of the valve face, with the diameter of each pore tapering from the inner to the outer valve surface; these pores are often occluded by siliceous processes. Features ofM. roeseana,not shown previously forMelosira,include a “stepped” mantle, on only one of the two valves resulting from the same cell division, flattened processes attached to short siliceous stalks on the valve face, disk‐like processes on the mantle, and an open girdle band with up to eight antiligulae. Siliceous scales on the surface of the initial cell are remnants of the auxospore wall. The epivalve of the initial cell is larger in diameter than the hypovalve, and both valves lack linking spines and a step on the valve surface. The initial, cell epicingulum consists of only two bands; the hypocingulum has up to seven. Initial cells with four or more hypocingular bands divide to form new post‐auxospore filaments.Melosira roeseanashould not be included in the genusMelosiraas it is presently defined by the type species,M. nurnmuloidesC. Ag. Major differences include irregular linking spines, a closed pseudoloculate valve construction, and labiate processes on the valve face and mantle ofM. nummuloides,compared with well‐defined linking spines, a valve constructed of a basal siliceous layer perforated by poroid areolae, and labiate processes lacking on the valve ofM. roeseana.

ULTRASTRUCTURE OF THE FILAMENTOUS HABIT IN THE DIATOM NAVICULA CONFERVACEA (KÜTZ.) GRUN.1

SUMMARYFrustules of the filamentous diatom Navicula confervacea (Kütz.) Grun. are united by the overlapping of marginal teeth located alongside the junction of valve face and mantle. Scanning and transmission electron microscopy show this connecting mechanism to differ from the previously reported inter‐digitating spines or teeth in the genera Melosira, Stephanodisus, and Fragilaria.

Alleged Pseudopodes of Diatoms

WILL you allow me to express my concurrence in your criticism (p. 140) on Mr. Grenfell's paper on the occurrence of pseudopodia in the Diatomaceous genera Melosira and Cyclotella? I express no doubt on the accuracy of Mr. Grenfell's observations, the knowledge of which I have derived from his paper in the Quarterly Journal of Microscopical Science, and from his verbal description at a meeting of the Linnean Society; but I do desire to enter my protest against the use of the term “pseudopodia” for the protoplasmic filaments observed by him. According to the accepted meaning of this term, it is applied to masses of protoplasm which are in organic connection with the protoplasm of the body of the organism, and which are retractile. I understand Mr. Grenfell that he is unable to affirm either of these facts with regard to the structures observed by him; and, until this is done, the application to them of the term “pseudopodia” appears to me to involve a begging of the question at issue, and a needless and regrettable confusion in terminology.