Curt M. Pueschel

AN EXPANDED SURVEY OF THE ULTRASTRUCTURE OF RED ALGAL PIT PLUGS1

The fine structure of pit plugs in 90 species of red algae was examined, bringing the total number of species in the continuing survey to 153. The organization of plug caps was confirmed to be a stable, predictable trait within thalli, between generations in heteromorphic life histories, and within the presently recognized orders, with one exception—the Acrochaetiales. Two forms of the outer cap were found in this group, a thin plate, as in the Nemaliales and Palmariales, and a dome, as in Batrachospermales and Corallinales. Variation of pit plug structure indicates that the Acrochaetiales are a heterogeneous assemblage and that pit plugs will be useful in reappraising their systematics. The systematic affinities of several species of uncertain affinities are clarified. Schmitziella endophloea Bornet et Batters is excluded from both orders, Corallinales and Acrochaetiales, with which it previously was allied. Although other ordinal attributions are not precluded by pit plug structure alone, pit plug structure is consistent with placement of Apophlaea sinclairii Harvey and Hildenbrandia rivularis (Liebman) J. Agardh in the Hildenbrandiales, Plagiospora gracilis Kuckuck, Schmitziella endophloea, and Wurdemannia miniata (Duby) J. Feldmann et Hamel in the Gigartinales, and Pseudorhododiscus nipponicus Masuda in the Palmariales.

A proposal for a new red algal order, the Thoreales

Representatives of the freshwater red algal family Thoreaceae were studied to resolve their taxonomic and phylogenetic status. Three specimens of Nemalionopsis and five collections of Thorea were examined for pit plug ultrastructure and analyzed for the sequences of the genes coding for the large subunit of RUBISCO (rbcL) and the small subunit of rRNA (18S rRNA). The phylogenetic trees generated from the two genes, and a combined tree all showed the Thoreaceae to be contained in a well‐supported monophyletic clade that is separate from the other two families currently classified in the Batrachospermales, the Batrachospermaceae and the Lemaneaceae. In addition, secondary structure elements of the 18S rRNA gene were observed at positions 650 and 1145 (Escherichia coli numbering system) that are not present in other members of the Rhodophyta. The pit plugs of the gametophytic and chantransia stages of the Thoreaceae contain two cap layers, the outer one of which is typically plate‐like, though occasionally inflated ones have been seen. No pit plug cap membrane has been observed. These findings indicate the Thoreaceae has been misclassified in the Batrachospermales and should be placed in its own order, the Thoreales. This order is characterized by having freshwater representatives with multiaxial gametophytes, a uniaxial chantransia stage, and pit plugs with two cap layers, the outer one of which is usually plate‐like.

Scanning electron microscopy and infrared spectroscopy of iron sediments formed by Thiobacillus ferrooxidans

Abstract Sediments from FeSO4 · 7H2O solutions oxidized by resting cell suspensions of Thiobacillus ferrooxidans in the absence of additional monovalent cations consisted of amorphous hydrated Fe(III) sulfate possessing reticular or filamentous microstructure. In the presence of additional sulfate supplied as Li2SO4, MgSO4, (CH3NH3)2SO4, or (CH3NH3)HSO4 at pH 2.4, hydronium jarosite crystallized in the form of pseudocubic rhombohedra. Other cations produced ammonio‐ and natrojarosites as pyramidal and bipyramidal rhombohedra or potassium and rubidium jarosites in rounded and botryoidal forms. Addition of Na2SeO4 yielded the selenium analog of amorphous hydrated Fe(III) sulfate, but in the presence of NH4 + or Rb+, selenojarosites formed instead. Addition of organic ligands, together with (NH4)2SO4, produced ammoniojarosite in the form of irregular granules and rounded and spheroidal crystals. Despite delayed precipitation, the infrared spectra of sediments were usually the same in the presence or absence ...

Affinities of the freshwater red alga Audouinella macrospora (Florideophyceae, Rhodophyta) and related forms based on ssu rrna gene sequence analysis and pit plug ultrastructure

Small subunit rDNA sequencing and transmission electron microscopy were performed to clarify the ordinal affinities of Audouinella macrospora (Wood) Sheath et Burkholder isolates 3394, 3395, and 3603, as well as Chantransia sp. isolate 3585. Culture 3603 is known to produce thalli of Batrachospermum ‐like morphology under certain culture conditions. Sequence analyses unequivocally placed the three Audouinella macrospora isolates in a clade with Batrachospermum macrosporum Montagne of the Batrachospermales, and Chantransia sp. was found to have affinities with B. louisianae Skuja and B. virgato‐decaisneanum Sirodot. The pit plugs of the Audouinella macrospora cultures 3394 and 3395 were nearly identical in size and structure, having thickened plug caps and no cap membranes. Both of these features agree with those of the Batrachospermaceae, with the latter feature showing batrachospermacean rather than acrochaetioid affinities. Pit plugs in the chantransia phase of 3603 were similar, but the plug caps were less well developed. The Batrachospermum phase generated from 3603 had pit plugs that were variable in diameter, according to location in the thallus, thus reflecting the more variable cell size in this phase. Dome‐like outer caps, considered typical of Batrachospermum, were present between cells of the determinate lateral filaments. The pit plugs of Chantransia sp. had prominent, dome‐like outer caps, but the plug cores were strikingly and consistently smaller in diameter than those of the A. macrospora chantransia cultures, suggesting that plug diameter may be of systematic value in some contexts.

ABSENCE OF CAP MEMBRANES AS A CHARACTERISTIC OF PIT PLUGS OF SOME RED ALGAL ORDERS1

The current general model of the organization of a fully developed rhodophycean pit plug includes a cap membrane associated with each end of the plug. Continuity of the plasmalemma and cap membrane results in the plug core being extracellular. However, routine ultrastructural methods have not convincingly demonstrated cap membranes in the Bangiales or the Corallinales. In this study, a variety of fixation regimes that enhance membrane contrast were used in an attempt to detect cap membranes in representatives of these two orders. Although cap membranes were readily and clearly demonstrable by these methods in a representative of an order previously known to have cap membranes, they could not be detected in members of the Bangiales or Corallinales. Should the absence of cap membranes prove to be an invariant feature of these two orders, presence or absence of cap membranes will constitute a new character for phylogenetic analysis.

Ultrastructural observations of tetrasporangia and conceptacles in Hildenbrandia (rhodophyta: Hildenbrandiales)

Ultrastructural techniques were used to investigate tetrasporangial development and conceptacle contents of Hildenbrandia occidentalis Setch. and H. rubra (Sommerf.) Menegh. = H. prototypus Nardo. Tetrasporocytes are formed by transformation of vegetative cells. A distinctive tetrasporangial wall is deposited around the tetrasporocyte. Cleavage of the tetrasporocyte is effected by mucilage-filled furrows initiated successively, but completed simultaneously. Following discharge of the tetraspores, the cell subtending the sporangium becomes a tetrasporocyte. Repetition of this process enlarges the conceptacle. True paraphyses and regenerative stalk cells were not observed in either species. Tetrasporangial walls persist in the conceptacle after spore release and, presumably, these are responsible for some of the reports of paraphyses. The implications of these findings for the intrageneric taxonomy of Hildenbrandia are considered. The unique mode of tetrasporogenesis found in the HIldenbrandiaceae supports ...

Biology of a terrestrial green alga, Chlorococcum sp. (Chlorococcales, Chlorophyta), collected from the Miruksazi stupa in Korea

T.A. Klochkova, S.-H. Kang, G.Y. Cho, C.M. Pueschel, J.A. West and G.H. Kim. 2006. Biology of a terrestrial green alga, Chlorococcum sp. (Chlorococcales, Chlorophyta), collected from the Miruksazi stupa in Korea. Phycologia 45: 349–358. DOI: 10.2216/04-58.1 A terrestrial chlorophyte, Chlorococcum sp., was isolated from the stone walls of Miruksazi stupa, which is a national treasure of Korea. The alga was one of the dominant organisms contributing to biodeterioration of the monument and it grew extensively on the walls of the inner room of the stupa, which had been sealed for more than 5 yr before we started this experiment. Chlorococcum survived in darkness during that time as dormant, warty, thick-walled spores. The resting spores revived in freshwater medium and released numerous unicellular progeny, which were isolated into a unialgal culture. The isolate was subjected to 18S rDNA phylogenetic analysis as well as ultrastructure and life cycle studies. In addition, the effect of salinity stress was investigated using sterile enriched seawater as a medium. Chlorococcum sp. grew in seawater culture medium for more than 5 mo and reproduced by aplanospores.

AN UNRECOGNIZED ANCIENT LINEAGE OF GREEN PLANTS PERSISTS IN DEEP MARINE WATERS 1

We provide molecular phylogenetic evidence that the obscure genera Palmophyllum Kütz. and Verdigellas D. L. Ballant. et J. N. Norris form a distinct and early diverging lineage of green algae. These palmelloid seaweeds generally persist in deep waters, where grazing pressure and competition for space are reduced. Their distinctness warrants recognition as a new order, the Palmophyllales. Although phylogenetic analyses of both the 18S rRNA gene and two chloroplast genes (atpB and rbcL) are in agreement with a deep‐branching Palmophyllales, the genes are in conflict about its exact phylogenetic placement. Analysis of the nuclear ribosomal DNA allies the Palmophyllales with the prasinophyte genera Prasinococcus and Prasinoderma (Prasinococcales), while the plastid gene phylogeny placed Palmophyllum and Verdigellas as sister clade to all other Chlorophyta.

Ramicrusta textilis sp. nov. (Peyssonneliaceae, Rhodophyta), an anatomically complex Caribbean alga that overgrows corals

Pueschel C.M. and Saunders G.W. 2009. Ramicrusta textilis sp. nov. (Peyssonneliaceae, Rhodophyta), an anatomically complex Caribbean alga that overgrows corals. Phycologia 48: 480–491. DOI: 10.2216/09-04.1 Ramicrusta textilis sp. nov. (Peyssonneliaceae, Gigartinales) is described from shallow, nearshore waters of Jamaica (Caribbean Sea). The reddish-gold to brown thalli grow on bedrock and dead coral heads, but they may also overgrow living corals. Thallus morphology is highly variable; a single confluent thallus may include smooth, prostrate crustose portions, overlapping foliose lobes, curtainlike erect lobes, and apically flaring columns. Tabular basal cells in parallel filaments support downgrowing, unicellular rhizoids on the ventral surface and branching assurgent filaments toward the dorsal surface. Extensive formation of secondary pit connections among lower cells of the assurgent filaments join cells of adjacent filaments along a horizontal axis that is oblique to that of each subtending layer, resulting in a pseudoparenchymatous construction that is highly patterned and tightly integrated. The outer cortex contains large cells associated with raised rims on the thallus surface, and these cells are interpreted as hair cell initials. Calcification is extensive, and the structure of the mineral skeleton, exposed by removal of organic material, is described by scanning electron microscopy. Peyssonnelia calcea and Ramicrusta nanhaiensis, both known only from the Indo-Pacific Ocean, are the only other peyssonnelioid species whose vegetative anatomy involves secondary pit connections or cell fusions, and their relationship to R. textilis is considered. Molecular analyses also indicate a relationship with R. nanhaiensis and support assignment of this new species to the genus Ramicrusta.

SYSTEMATIC SIGNIFICANCE OF THE ABSENCE OF PIT‐PLUG CAP MEMBRANES IN THE BATRACHOSPERMALES (RHODOPHYTA)

Four species of the Batrachospermales were examined by transmission electron microscopy to determine whether or not cap membranes, a typical structural component of pit plugs in several orders of red algae, were present. Routine specimen preservation methods used in past studies led to contradictory reports, so Batrachospermum keratophytum Bory, B. sirodotii Skuja ex Reis, Sirodotia suecica Kylin, and S. tenuissima (Collins) Skuja ex Flint were prepared by secondary fixation in potassium permanganate or a combination of potassium ferrocyanide‐osmium tetroxide to enhance membrane contrast. These fixation procedures produced clear, well‐contrasted images in which cap membranes were absent. The absence of cap membranes in S. suecica and S. tenuissima and the presence of cap membranes in two members of the Nemaliales was confirmed by freeze‐substitution methods. Absence of cap membranes in representatives of the Batrachospermales further distinguishes the Batrachospermales from the Nemaliales, the order in which they long resided, and demonstrates the value of this character in elucidating ordinal alliances among the Rhodophyta.