Conxi Rodríguez-Prieto

The Spreading of the Introduced Seaweed Caulerpa taxifolia (Vahl) C. Agardh in the Mediterranean Sea: Testing the Boat Transportation Hypothesis

The Spreading of the Introduced Seaweed Caulerpa taxifolia (Vahl) C. Agardh in the Mediterranean Sea: Testing the Boat Transportation Hypothesis

Lack of severe nutrient limitation in Caulerpa taxifolia (Vahl) C. Agardh, an introduced seaweed spreading over the oligotrophic Northwestern Mediterranean

We performed a seasonal study of the importance of nitrogen (N) and phosphorus (P) as limitation to the productivity of Caulerpa taxifolia (Vahl) C. Agardh, a seaweed invading the western Mediterranean coasts. The study presented here indicates that Caulerpa taxifolia did not respond to nutrient enrichment, except for plants collected in April and September 1993, where productivity and alkaline phosphatase activity (APA) of enriched plants varied 0.5- to 3-fold relative to those of control plants. Rates of APA ranged from 9 to 52 mu M PO4 odw h(-1), close to those characteristic of P-sufficient macroalgae. Tissue nutrient concentrations were frequently above typical critical levels for species of macroalgae ranging from 1.36 to 3.13% dw, and 0.16 to 0.21% dw, for N and P, respectively. Seasonal variation was moderate and not consistent. The lack of severe nutrient limitation in Mediterranean populations of Caulerpa taxifolia could be an important factor enabling it to outcompete native macrophytes

Vegetative and reproductive morphology of Gloiocladia repens (C. Agardh) Sánchez et Rodríguez-Prieto comb. nov. (Rhodymeniales, Rhodophyta), with a taxonomic re-assessment of the genera Fauchea and Gloiocladia

A morphological and molecular study of Fauchea repens, the type species of Fauchea, (Faucheaceae, Rhodymeniales) and its comparison with Gloiocladia furcata, the type species of Gloiocladia, establishes that the two are closely related and belong in the same genus. Accordingly, we propose a new combination, Gloiocladia repens (C. Agardh) Sánchez et Rodríguez-Prieto, comb. nov., for the plant presently known as Fauchea repens (C. Agardh) Montagne et Bory in Montagne and designate a lectotype. We provide an emended description of the genus Gloiocladia, and transfer all the species presently placed in Fauchea to Gloiocladia.

Behaviour of the Nuclei in Pre- and Postfertilization Stages in Kallymenia (Kallymeniaceae, Rhodophyta)

C. Rodríguez-Prieto and M.H. Hommersand. 2009. Behaviour of the nuclei in pre- and postfertilization stages in Kallymenia (Kallymeniaceae, Rhodophyta). Phycologia 48: 138–155. DOI: 10.2216/08-75.1. The female reproductive complex in Kallymenia is composed of separate (nonprocarpic) carpogonial branch and auxiliary cell branch systems that link by means of connecting filaments. We describe the development of these systems and their functioning up to the time of carpospore formation in relation to the behaviour of the nuclei, using hematoxylin stain, in the Mediterranean species of Kallymenia – K. feldmannii, K. lacerata, K. patens and K. requienii – compared to those of the type species, K. reniformis, from Atlantic Europe. Derivatives of the putative fertilization nucleus (diploid) were generally twice the diameter (2.0–3.0 µm) of the vegetative gametophytic (haploid) nuclei (1.0–1.5 µm). Nuclei in the supporting cell and subsidiary cells of the carpogonial branch system are large, with amplified levels of DNA, and increase in size and fuse as the subsidiary cells fuse with the supporting cell and the fusion cell enlarges after presumed fertilization. Putative diploid nuclei inside the fusion cell remain the same size. The fusion cell cuts off numerous uninucleate connecting filament initials some of which elongate into connecting filaments of uniform diameter, each of which is provided with a single terminal diploid nucleus. Connecting filaments seek out and fuse with auxiliary cells, whereupon the diploid nucleus divides repeatedly, producing many derivative nuclei that line the connecting filament and give rise to gonimoblast filaments laterally. Gonimoblast filaments may link up with gametophytic cortical and medullary cells and produce secondary gonimoblast filaments. Branches of the gonimoblast filaments bear carposporangia in chains that mature basipetally and separate forming clusters of carpospores. The carpospores are either released or commonly germinate in situ and connect secondarily with gametophytic cells and with each other to produce a pseudoparenchymatous mat that may function as a propagule.

Vegetative and reproductive morphology of the type species of Gloiocladia, G. furcata (Faucheaceae, Rhodophyta)

N. Sánchez and C. Rodríguez-Prieto. 2005. Vegetative and reproductive morphology of the type species of Gloiocladia, G. furcata (Faucheaceae, Rhodophyta). Phycologia 44: 222–233. The type species of Gloiocladia, G. furcata, is described in detail, and its characters are compared with those of other species currently accepted in Gloiocladia. The presence of a subcortex of ovoid, angular or stellate cells, connected by secondary pit connections to form a network parallel to the thallus surface, is confirmed. Female reproductive structures and postfertilization stages are described for the first time. Plants are procarpic, with the 3-celled carpogonial branch and two-celled auxiliary cell branch borne on a cortical cell that acts as supporting cell. The auxiliary cell contains a large proteinaceous inclusion. After fertilisation cells of the carpogonial branch fuse and connect to the auxiliary cell. The auxiliary cell divides into a primary gonimoblast cell that contains the proteinaceous inclusion and a lower auxiliary cell. A fusion cell between the auxiliary mother cell, the lower auxiliary cell and adjacent vegetative cells is formed. Gonimoblasts arising from the primary gonimoblast cell produce several erect projections bearing lobes of ovoid carposporangia. Basal nutritive cells are present, with erect persistent filaments (= tela arachnoidea) surrounding the fertilised procarp and the gonimoblast. Ostiolate cystocarps, with or without horns, arise on branch margins. Spermatangia remain unknown. Tetrasporangia are grouped in slightly raised nemathecia. In the family Faucheaceae, the presence of a subcortex in all individuals and the presence of basal nutritive tissue with erect persistent filaments in fertile female thalli are confirmed to be important taxonomic characters. These observations support the proposal of Norris (1991) to include Gloioderma in Gloiocladia but do not clarify the relationship between Gloiocladia and Fauchea.

Marine Invasion in the Mediterranean Sea: The Role of Abiotic Factors When There Is No Biological Resistance

The tropical red alga Womersleyella setacea (Rhodomelaceae, Rhodophyta) is causing increasing concern in the Mediterranean Sea because of its invasive behavior. After its introduction it has colonized most Mediterranean areas, but the mechanism underlying its acclimatization and invasion process remains unknown. To understand this process, we decided i) to assess in situ the seasonal biomass and phenological patterns of populations inhabiting the Mediterranean Sea in relation to the main environmental factors, and ii) to experimentally determine if the tolerance of W. setacea to different light and temperature conditions can explain its colonization success, as well as its bathymetric distribution range. The bathymetric distribution, biomass, and phenology of W. setacea were studied at two localities, and related to irradiance and temperature values recorded in situ. Laboratory experiments were set up to study survival, growth and reproduction under contrasting light and temperature conditions in the short, mid, and long term.Results showed that, in the studied area, the bathymetric distribution of W. setacea is restricted to a depth belt between 25 and 40 m deep, reaching maximum biomass values (126 g dw m−2) at 30 m depth. In concordance, although in the short term W. setacea survived and grew in a large range of environmental conditions, its life requirements for the mid and long term were dim light levels and low temperatures. Biomass of Womersleyella setacea did not show any clear seasonal pattern, though minimum values were reported in spring. Reproductive structures were always absent. Bearing in mind that no herbivores feed on Womersleyella setacea and that its thermal preferences are more characteristic of temperate than of tropical seaweeds, low light (50 µmol photon m−2 s−1) and low temperature (12°C) levels are critical for W. setacea survival and growth, thus probably determining its spread and bathymetric distribution across the Mediterranean Sea.

Life histories of Predaea ollivieri and P. pusilla (Nemastomatales, Rhodophyta)

The life histories of Predaea ollivieri J. Feldmann and P. pusilla (Berthold) J. Feldmann were studied in vitro. In P. ollivieri, carpospore germination was unipolar, and sporophytes were formed of sparsely branched uniseriate filaments. In P. pusilla, carpospore germination was bipolar, and sporophytes were formed of uniseriate filaments consolidated in a pseudoparenchymatous crust. Carpospore development was observed in both species when irradiances ranged between 5–40 μmol m−2 s−1 combined with seawater temperature of 16, 18 or 21°C; no development was observed at 80 μmol m−2 s−1 or 14°C. Tetrasporophytes of P. ollivieri developed tetrasporangia in summer, autumn, winter and spring conditions. When the irradiance and temperature were high (40 μmol m−2 s−1, 21°C; hot-summer), bisporangia were produced instead of tetrasporangia. In summer and autumn conditions, some tetraspores gave rise to dioecious gametophytes, with male and female structures identical to those of the mother plant. In P. pusilla, tetrasporangia were not observed, but monosporangia were present in summer, autumn, winter and spring conditions, and bispores in hot-summer conditions. In late spring and summer, some monospores gave rise to dioecious gametophytes, with male and female structures identical to those of the mother plant. In both species, all types of spores were capable of producing new sporophytes that repeat this process for several successive generations. This capacity of sporophyte self-generation appears to promote survival by increasing the number of individual plants of the population.

Deep-water macroalgal-dominated coastal detritic assemblages on the continental shelf off Mallorca and Menorca (Balearic Islands, Western Mediterranean)

Abstract We present a quantitative physiognomic characterization of major macroalgal-dominated assemblages on coastal detritic bottoms of the continental shelf off Mallorca and Menorca (Balearic Islands, Western Mediterranean). In late spring of 2007 and 2008, 29 samples were collected by bottom trawling at depths between -52 and -93 m. These samples were then sorted and identified to their lowest taxonomic level. Statistical analyses distinguished six different assemblage types: shallower water environments (-52 to -65 m in depth) were characterized by Osmundaria volubilis and Phyllophora crispa meadows and two types of Peyssonnelia beds; two assemblage types, Laminaria rodriguezii beds and maërl beds, were only present in deep-water environments (-77 to -81 m); and an assemblage dominated by P. crispa and Halopteris filicina was found in both shallow and deep waters (-57 to -93 m). We assess the distribution of these six assemblage types through the studied area.

Botryocladia chiajeana and Botryocladia macaronesica sp. nov. (Rhodymeniaceae, Rhodophyta) from the Mediterranean and the eastern Atlantic, with a discussion on the closely related genus Irvinea

J. Afonso-Carrillo, C. Rodríguez-Prieto, F. Boisset, C. Sobrino, I. Tittley and A.I. Neto. 2006. Botryocladia chiajeana and Botryocladia macaronesica sp. nov. (Rhodymeniaceae, Rhodophyta) from the Mediterranean and the eastern Atlantic, with a discussion on the closely related genus Irvinea. Phycologia 45: 277–292. DOI: 10.2216/04-97.1 Specimens from the eastern Atlantic, Mediterranean and Adriatic seas previously reported as Botryocladia chiajeana showed differences in morphology, and re-examination of Meneghinis original collection of Chrysymenia chiajeana (basionym B. chiajeana) revealed that only the Mediterranean and Adriatic specimens are in agreement with the original protologue, whereas plants reported from the eastern Atlantic are recognised here as Botryocladia macaronesica Afonso-Carrillo, Sobrino, Tittley & Neto sp. nov. The vegetative and reproductive morphology of western Mediterranean plants is examined in detail for the first time, and B. chiajeana is characterised by the following combination of features: solid axes bearing frequently dichotomously branched vesicles, vesicle walls three layered, outer cortical cells arranged in rosettes, secretory cells borne on modified medullary cells, spermatangia cut off from scattered spermatangial mother cells, cystocarps strongly protuberant and tetrasporangia cruciately divided and exposed on the outer cortical layer at maturity. From the Meneghini collection, a lectotype specimen of C. chiajeana was selected. Botryocladia macaronesica, known so far only from the islands of Azores, Madeira, Canaries and Cape Verde, differs from other Botryocladia species by a unique combination of significant attributes including elongate saccate vesicles, near-continuous cortication of vesicle walls, secretory cells on unmodified medullary cells and completely immersed cystocarps. An analysis of the morphological characters currently used for separating Botryocladia from related genera (i.e. Chrysymenia, Gloiosaccion and Irvinea), showed that there is considerable overlap between Botryocladia and Irvinea. These genera are presently discriminated mostly by molecular evidence as the supposed morphological characters are shown here to vary considerably within the genus Botryocladia.

Leptofauchea coralligena (Faucheaceae, Rhodophyta), a new species from the Mediterranean Sea

Morphological and reproductive studies, corroborated by gene sequence data, demonstrate that there are two distinct entities within Mediterranean specimens referable to the red alga Rhodymenia ardissonei (Rhodymeniaceae). Genuine R. ardissonei grows in shallow water while specimens from deep water habitats, traditionally attributed to the same species, belong to Leptofauchea, a genus placed in the Faucheaceae. The deep water growth is herein described as a new species, Leptofauchea coralligena. Female gametophytes in Leptofauchea are easily distinguished because of the presence of a tela arachnoidea in the pericarp cavity and tetrasporangia developing in nemathecia. Sterile specimens, however, can be extremely difficult to tell apart because differences in vegetative morphology and anatomy are subtle. Refractive bodies in the medullary cells form the most conspicuous diagnostic character separating L. coralligena from R. ardissonei. These structures can be easily observed in young specimens of L. coralligena, both in surface view and transverse sections. However this character becomes less obvious or even impossible to observe in mature thalli with medullary cells containing large amounts of floridean starch. Refractive bodies are also difficult to observe in herbarium specimens. The existence of these structures has not previously been reported from any other Leptofauchea species. The presence of L. coralligena has been confirmed in the western Mediterranean Sea. Atlantic specimens attributed to R. ardissonei require further study.