Erect Axes Research Articles

Gelidiella papillosa sp. nov. (Gelidiellaceae, Rhodophyta) from Veracruz, Mexico, in the context of the worldwide distribution of G. acerosa

Abstract Gelidiella acerosa is a widely distributed species, with type locality in Yemen, whose morphology has been characterized by decumbent axes from which numerous abundantly branched erect axes emerge, pectinate, alternate or radial. Recent phylogenetic studies have revealed the presence of genetically independent groups throughout its distribution range. However, these groups cannot be described as independent since there are no sequences from the type locality that allow us to establish the genetic group to which the true G. acerosa belongs, generating a complex of cryptic species. In the present study, from COI-5P and rbcL sequence data, we detected six genetically differentiated groups, one of which is represented only by specimens from the Western Atlantic region. Given the allopatric pattern, it is possible to describe the Atlantic group as an independent species of the cryptic complex in the Indo-Pacific. Gelidiella papillosa sp. nov. shares several morphological features with other specimens previously identified as G. acerosa in other countries, like the appearance of the thallus, branching patterns, the presence of multiple superficial hairs on the branches or cell measurements. However, these characters have not been evaluated in detail among the different genetic groups within Gelidiella acerosa, consequently, G. papillosa can be supported only by its genetic independence and allopatric distribution.

A New Species from the Canary Islands Increases the Diversity of the Red Algal Genus Pterocladiella in the Northeastern Atlantic.

Environmental and human factors are inducing a drastic decline in many marine algae in regions with a high floristic richness as in the Canary Islands. Simultaneously, undescribed algal species continue to be discovered, suggesting a probable loss in diversity, before being properly identified and catalogued. Turf-forming Gelidiales occur in marine littoral communities from tropical to warm temperate regions and are challenging to identify correctly because of their small size and simple morphology. In the present study, we combined morphological and molecular phylogenetics methods to study a turf-forming species of the genus Pterocladiella from the Canary Islands (NE Atlantic). Both cox1 and rbcL gene analyses revealed a novel species described here, Pterocladiella canariensis sp. nov. The new species has no single unique morphological feature, but it is different by a distinctive combination of attributes, namely, minute size less than 18 mm in height, ribbon-like erect axes, small polygonal cortical cells, cystocarp circular in outline with placental tissue attached to the floor, spermatangial sori with sterile margins with spermatangia simultaneously formed on both sides of the blade, and tetrasporangia arranged in V-shaped rows. Phylogenies inferred from cox1 and concatenated genes (cox1 + rbcL) suggest a link to only two Pterocladiella species endemic to South Africa and Madagascar; nevertheless, the rbcL gene establishes P. canariensis as the earliest divergent lineage of the genus.

Gelidiorariphycus gen. nov. (Gelidiales, Rhodophyta): a rare genus found in the Americas

ABSTRACT DNA sequence analyses have demonstrated that Gelidium as currently circumscribed is not monophyletic and has three distinctive lineages: Gelidium sensu stricto that includes the generitype Gelidium corneum, the Capreolia group, and another lineage that includes two distinct clades formed by species from the eastern Pacific and western Atlantic Oceans. A new genus of small gelidioid algae, Gelidiorariphycus, is described to accommodate one of the clades in this latter lineage. Four species (Gelidiorariphycus loratus, G. gahunbooi, G. stipitatus and G. sungminbooi) segregated into this genus in single- and multi-gene phylogenies. Gelidiorariphycus is sister to a clade formed by an unidentified eastern Pacific species and Gelidium lingulatum. These clades are closely related to a clade formed by Gelidiophycus and the Capreolia group. All four Gelidiorariphycus species were morphologically similar with small thalli that have simple and distally flattened erect axes. Fertile tetrasporophytes were found to have sori with sterile margins that are acutely tapered, which may be morphologically distinctive, but determining this requires additional study. These species were rare, with only one or two samples of each collected despite Gelidiales surveys having been done in the areas where they are known. They were mainly found growing on shallow subtidal rocky shores, but a G. gahunbooi specimen was also collected at more than 30 m depth. Their small size and preference for subtidal habitats may explain the small number of specimens collected. The recognition of this new genus is a further step in the establishment of a natural classification system for genera within the Gelidiaceae.

Morphology of filamentous thalli of Analipus japonicus (Ralfsiales), temperature and irradiance effects on their formation and growth, and erect thallus formation in the field

Free-living filamentous thalli derived from an Analipus japonicus erect thallus were established in laboratory culture. The filamentous thalli were composed of slender filaments and densely pigmented oval or sub-oval cell masses. Temperature (5–20 °C) and irradiance (25–200 μmol photons m−2 s−1) effects on formation and growth of the thalli from three explant groups (isolated filaments, small cell masses, and large cell masses) were investigated for 15 days. These explants survived over the examined range. The isolated filaments had a high ability to form the thalli, and the isolated and new filaments formed filaments and cell masses. Meanwhile, the isolated and new cell masses formed only filaments, and their ability to grow and form the thalli decreased as they grew in size. Optimum culture conditions for formation and growth of the thalli from the isolated filaments, and the two cell mass growths were 15–20 °C and 100–200 μmol photons m−2 s−1. To produce erect thalli, the filamentous thalli were cultured on seedling threads for 6 weeks at 15 °C, 60 μmol photons m−2 s−1 and 20 cm s−1 water flow velocity. Erect axis density increased with increasing coverage of the filamentous thalli, and their cell masses (primordia of erect thallus holdfast) with mean area of about 140 × 103 μm2 began to produce erect axes. After 4 months of field cultivation, they grew into full-grown erect thalli of about 20 cm long. These findings show that the free-living filamentous thalli were applicable for stable seedling production of A. japonicus to be used in aquaculture.

Secondary attachment disc of edible seaweed Chondracanthus chamissoi (Rhodophyta, Gigartinales): Establishment of permanent thalli stock

In this study we evaluated the productivity of an outdoor cultivation system based in secondary attachment discs (SADs) of Chondracanthus chamissoi as propagation strategy to produce and maintain a permanent thalli stock. For that, re-attachment of fronds, survival of SADs, growth rate of new erect axes, coverage and productivity were evaluated in three different artificial substrates: fiberglass plates, ceramic plates and PVC pipes. C. chamissoi SADs were formed in all three substrates, and they developed new erect axes reaching >6 mm length after 12 weeks. Ceramic and fiberglass plates were the substrates with the best performance. Nonetheless, the cultivation system using fiberglass was the most suitable one, since it presented a higher survival of the SADs and a better use of tank space, improving the amount of seaweeds growing inside the tanks. Based on the results, the estimated cultivation using fiberglass plates would allow to produce 31,993 SADs on a 3m3 tank after 90 days. This technology would allow: (i) to produce thalli to be used as propagules for seaweed cultivation based on vegetative propagation, since nowadays this depends of thalli from natural populations; (ii) to propagate and maintain a thalli stock with desirable commercial traits, providing an better biomass quality, (iii) to grow and maintain thalli in the same tank from diverse localities and/or reproductive phase; optimizing resources and space, which currently is not feasible using free-floating systems, due to the difficulty to recognize isomorphic haploid and diploid phases, and (iv) to adopt this strategy in other red seaweeds of commercial interest, such as the genus Chondracanthus, Gigartina and Solieria.

<p><strong><em>Centroceras gasparrinii</em></strong><strong> subsp. <em>minor</em> subsp. nov. (Ceramiaceae, Rhodophyta) in the North Adriatic Sea (Mediterranean): molecular and morphological characterization</strong></p>

Centroceras Kützing is a small red algal genus with 18 currently accepted species (Guiry & Guiry 2019), characterized by simple filamentous thalli with erect axes arising from a prostrate system and di-trichotomous branching (Hommersand 1963). The characters used to distinguish species are primarily cortical filament morphology: shape and number of the acropetal cortical cells, shape of gland cells, and shape of spines (Won et al. 2009). The generitype C. clavulatum (C. Agardh) Montagne has been viewed for a long time as a highly variable and cosmopolitan species (Hommersand 1963). Molecular and detailed morphological analyses brought Barros-Barreto et al. (2006) to report that C. clavulatum may consist of a species complex and Won et al. (2009) confirmed this hypothesis identifying eight taxonomic entities phylogenetically segregated from genuine C. clavulatum. Seven of these entities were assigned to the following species: C. gasparrinii (Meneghini) Kützing, C. hommersandii Won, T.O. Cho & Fredericq, C. hyalacanthum Kützing, C. micracanthum Kützing, C. natalensis Won, T.O. Cho & Fredericq, C. rodmanii Won, T.O. Cho & Fredericq, and C. tetrachotomum Won, T.O. Cho & Fredericq, (Won et al. 2009). Centroceras gasparrinii, C. hyalacanthum, and C. micracanthum are three western Atlantic species listed as synonyms of C. clavulatum since the middle of the 19th century and resurrected from the ‘C. clavulatum complex’ by Won et al. (2009). In particular, two of these taxa were described from specimens of the Mediterranean Sea: C. gasparrinii (as Ceramium gasparrinii Meneghini, type locality Palermo, Italy) and C. micracanthum (reported with the synonym Centroceras leptacanthum Kützing, type locality Genoa, Italy). Therefore, the numerous Mediterranean records of C. clavulatum (e.g., Gómez Garreta et al. 2001; Verlaque 2001; Sfriso & Curiel 2007; Taşkýn et al. 2013) most probably belong to one of these two species and have to be re-examined for a correct identification and to understand the spatial distribution of the different taxa (Tsiamis et al. 2010). For this reason, in the last years in Greece (Tsiamis et al. 2010), Spain (Gallardo et al. 2016) and Morocco (Hassoun et al. 2018) accurate sampling and morphological analyses of specimens previously identified as C. clavulatum were conducted to determine their correct taxonomic identities. In all cases the recognized species was C. gasparrinii, which can be distinguished morphologically from the other ones previously known as C. clavulatum by the presence of ovoid gland cells and ovoid terminal acropetal cortical cells (Won et al. 2009). As reported by Tsiamis et al. (2010), Greek samples differed from those described by Won et al. (2009), in the smaller number of periaxial cells (10–12 against 13–19).

Frequency of chimerism in populations of the kelp Lessonia spicata in central Chile.

Chimerism occurs when two genetically distinct conspecific individuals fuse together generating a single entity. Coalescence and chimerism in red seaweeds has been positively related to an increase in body size, and the consequent reduction in susceptibility to mortality factors, thus increasing survival, reproductive potential and tolerance to stress in contrast to genetically homogeneous organisms. In addition, they showed that a particular pattern of post-fusion growth maintains higher genetic diversity and chimerism in the holdfast but homogenous axes. In Chilean kelps (brown seaweeds), intraorganismal genetic heterogeneity (IGH) and holdfast coalescence has been described in previous research, but the extent of chimerism in wild populations and the patterns of distribution of the genetically heterogeneous thallus zone have scarcely been studied. Since kelps are under continuous harvesting, with enormous social, ecological and economic importance, natural chimerism can be considered a priceless in-situ reservoir of natural genetic resources and variability. In this study, we therefore examined the frequency of IGH and chimerism in three harvested populations of Lessonia spicata. We then evaluated whether chimeric wild-type holdfasts show higher genetic diversity than erect axes (stipe and lamina) and explored the impact of this on the traditional estimation of genetic diversity at the population level. We found a high frequency of IGH (60–100%) and chimerism (33.3–86.7%), varying according to the studied population. We evidenced that chimerism occurs mostly in holdfasts, exhibiting heterogeneous tissues, whereas stipes and lamina were more homogeneous, generating a vertical gradient of allele and genotype abundance as well as divergence, constituting the first time “within- plant” genetic patterns have been reported in kelps. This is very different from the chimeric patterns described in land plants and animals. Finally, we evidenced that IGH affected genetic differentiation among populations, showed lower levels of FST index when we compared holdfast than lamina samples. In the light of this, future studies should evaluate the significance of chimeric holdfasts in their ability to increase kelps resilience, improve restoration and ecosystem service.

Coalescing red algae exhibit noninvasive, reversible chimerism.

Chimerism is produced by the somatic fusion of two or more genetically distinct conspecific individuals. In animals, the main cost of fusion is competition between genetically different cell lineages and the probability of original cell line replacement by more competitive invasive lines, which limits its natural frequency (3%-5%). In red and brown seaweeds, chimerism is widespread (27%-53%), seemingly without the negative outcomes described for animals. The rigidity of cell walls in macroalgae prevents cell motility and invasions. In addition, in moving waters, most somatic fusions involve the holdfast. Histological observations in laboratory-built bicolor macroalgal chimeras indicated that upright axes emerge from the base of plants by proliferation and vertical growth of discrete cell groups that include one or just a few of the cell lineages occurring in the holdfasts. Laboratory experiments showed growth competition between cell lineages, thus explaining lineage segregation during growth along originally chimeric erect axes. Genotyping of the axes showed more heterogeneous tissues basally, but apically more homogeneous ones, generating a vertical gradient of allele abundance and diversity. The few chimeric primary branches produced, eventually became homogenous after repeated branching. Therefore, coalescing macroagae exhibit a unique pattern of post-fusion growth, with the capacity to reverse chimerism. This pattern is significantly different from those in animals and land plants, suggesting chimerism is a biologically heterogeneous concept.

A revised classification of the Gelidiellaceae (Rhodophyta) with descriptions of three new genera: Huismaniella, Millerella and Perronella

AbstractThe agarophyte family Gelidiellaceae currently includes 26 species in two genera, Gelidiella and Parviphycus, but the generic status and species boundaries have not been fully explored. In order to resolve taxonomic issues in the family, we analyzed mitochondria‐encoded cox1 and plastid‐encoded rbcL and psaA genes from types and fresh collections including topotype material. The Gelidiellaceae was resolved with five distinct groups, interpreted here as representing five genera: (1) Gelidiella, including the type, (2) Huismaniella gen. nov., (3) Millerella gen. nov., (4) Parviphycus s.str. including the type, and (5) Perronella gen. nov. Gelidiella was recognized as including a new species, G. flabella, that is described for specimens from Madagascar. A new genus, Huismaniella, is described for the species previously known as Gelidiella ramellosa, characterized by lateral tetrasporangial branchlets inserted at right angles on erect axes and irregularly arranged tetrasporangia. Parviphycus includes P. adnatus which is characterized by simple thalli with tetrasporangial branchlets formed directly on prostate axes and holdfasts forming continuous fringes along the entire length of prostrate axes. The new genus Millerella is described to accommodate five species previously known as Gelidiella or Parviphycus, characterized by tetrasporangial sori formed on erect axes or branches and unicellular rhizoids forming irregular clumps along prostrate axes. Perronella gracilis gen. et sp. nov. is described for plants with terete axes, multifarious branching, and monosporangia formed on erect axes and branches. The implications for nomenclature, taxonomic revisions, and biogeography in the Gelidiellaceae are discussed.

Pterocladiella feldmanniisp. nov. andP. hameliisp. nov. (Gelidiales, Rhodophyta), Two New Species Uncovered in Madagascar During the Atimo Vatae Expedition

We analyzed both mitochondrial cox1 and plastid rbcL sequences from specimens of Pterocladiella from Madagascar and compared their morphologies with previously described species in the genus. Both molecular and morphological datasets demonstrated the presence of five species in Madagascar: P. australafricanensis, P. bartlettii, P. caerulescens, and two new species, P. feldmannii and P. hamelii, described here. Pterocladiella feldmannii is distinguished by plants with a size of about 6 cm with narrow axes and opposite to irregular branches, rhizines congested in medulla, tetrasporangial branchlets constricted at base of branches, tetrasporangial sori without sterile margins, and irregular arrangement of tetrasporangia. Pterocladiella hamelii is characterized by plants with a size of about 3 cm with flattened and thin erect axes and irregular branches, radial arrangement of subapical cells at tips of main axes, tetrasporangial sori with sterile margins and horizontal to irregular arrangement of tetrasporangia. Phylogenetic analyses based on cox1 and rbcL sequences revealed the sister relationship between P. feldmannii and P. hamelii, and their distant relationships to P. australafricanensis, P. bartlettii, and P. caerulescens. The Madagascan Pterocladiella is composed of two geographical elements: Madagascan endemic (P. feldmannii and P. hamelii) and species with wide distributions (P. australafricanensis, P. bartlettii and P. caerulescens).

NEW PALEONTOLOGICAL INSIGHTS INTO THE EMSIAN–EIFELIAN TROUT VALLEY FORMATION, BAXTER STATE PARK'S SCIENTIFIC FOREST MANAGEMENT AREA, AROOSTOCK COUNTY, MAINE

Abstract The Trout Valley Formation of Emsian–Eifelian age in northern Maine hosts evidence of early vascular plant communities interpreted as having colonized wetland, estuarine environments. To date, collections made under permits issued by the Baxter State Park Commission originate from outcrop along Trout Brook, its tributaries, and poorly exposed lithologies inside the woodlands. Construction of a new roadway in the Scientific Forest Management Area, oriented parallel to Trout Brook, unearthed pavement exposures in which new fossil assemblages were found. These were collected under a salvage and conservation effort. Plant megafossils, as well as new macroinvertebrates and ichnofossils, were recovered from sandy siltstone and siltstone lithofacies along a west-to-east transect along Wadleigh Mountain Road. Autochthonous plants fossils include erect axes of cf. Psilophyton forbesii and vertical rooting structures of unknown affinity. Parautochthonous and allochthonous plants include Pertica quadrifaria...

Neosiphonia yongpilii sp. nov. (Rhodomelaceae, Rhodophyta), known as Neosiphonia simplex from Korea, with an emphasis on cystocarp development

:A critical re-examination of recent collections and herbarium specimens from Korea previously referred to Neosiphonia simplex (Hollenberg) Y.Lee showed them to be incorrectly identified. The phylogenetic analyses of rbcL sequences demonstrated that ‘N. simplex’ from Korea formed a clade distinct from other species in Polysiphonia sensu lato, and was clearly separate from N. simplex from California, with high sequence divergence. We propose N. simplex sensu Y.Lee from Korea as the new species, Neosiphonia yongpilii sp. nov. This novel species was characterized by severely twisted erect axes, with two to three pinkish sterile cells at apices of spermatangial branches. We also noted that lateral and basal sterile cell groups remain until maturation of the gonimoblast, and that the origin of inner and outer cortical filaments of the pericarp are central cells and pericentral cells respectively.

Morphological and community changes of turf algae in competition with corals.

The morphological plasticity and community responses of algae competing with corals have not been assessed. We evaluated eight morphological characters of four species of stoloniferous clonal filamentous turf algae (FTA), including Lophosiphonia cristata (Lc) and Polysiphonia scopulorum var. villum (Psv), and the composition and number of turf algae (TA) in competition for space with the coral Orbicella spp. under experimental and non-manipulated conditions. All FTA exhibited morphological responses, such as increasing the formation of new ramets (except for Psv when competing with O. faveolata). Opposite responses in the space between erect axes were found when Psv competed with O. faveolata and when Lc competed with O. annularis. The characters modified by each FTA species, and the number and composition of TA species growing next to coral tissue differed from that of the TA growing at ≥3 cm. The specific and community responses indicate that some species of TA can actively colonise coral tissue and that fundamental competitive interactions between the two types of organisms occur within the first millimetres of the coral−algal boundary. These findings suggest that the morphological plasticity, high number, and functional redundancy of stoloniferous TA species favour their colonisation of coral tissue and resistance against coral invasion.

Re-identifying Grateloupia yangjiangensis (Rhodophyta, Halymeniaceae) based on morphological observations, life history and rbcL sequence analyses

On the basis of morphological observations, life history and molecular phylogeny, Grateloupia yangjiangensis, which is similar to G. filicina, G. orientalis, G. catenata, and G. ramosissima in appearance, was re-examined. The results are as follows: (1) the auxiliary-cell ampullae of G. yangjiangensis were of Grateloupia type, thalli was fleshy and gelatinous in texture, and the erect axes were compressed; the cortex was 0.25–0.30 mm thick, consisting of five to seven outer layers, and there were five inner layers of triangular or stellate cells; (2) there was no filamentous stage in the development of the carpospores; (3) the ribulose-1,5-bisphosphate carboxylase/oxygenase gene (rbcL) sequence of four G. yangjiangensis examined showed that there was no intergeneric divergence among them, and for the phylogenetic tree, four sequences of G. yangjiangensis formed a single monophyletic subclade within the large Grateloupia clade of Halymeniaceae. In conclusion, G. yangjiangensis was a single species within the genus Grateloupia. This research provided criterion for identification and cultivation of G. yangjiangensis.

The turf-forming alga Gelidium crinale (Florideophyceae, Rhodophyta) on Atlantic Patagonian coasts

Abstract We describe for the first time the morphology of Gelidium crinale from its natural habitat in Atlantic Patagonia with special consideration of diagnostic characters. Observations and morphometric measurements were done on fresh specimens using scanning electron and inverted light microscopy. This report is a new record for Atlantic Patagonian coasts. The thalli comprise prostrate and erect axes; they are subterete at the base and compressed to flattened at the apices. The basal parts are scarcely and irregularly branched, while the apical parts are highly ramified and subdichotomously branched. The lengths of thalli and the ramification patterns differ from previous descriptions, and were variable between seasons and life history phases. “Brush-like” haptera confirmed the identity of the algae as members of the Gelidiaceae. Internal rhizoidal filaments are abundant and distributed in groups throughout the medulla. The life history was of the “Polysiphonia-type”; occurrences of carposporophytes and tetrasporophytes were variable.

Morphology and molecular study of Pterosiphonia arenosa sp. nov. (Rhodomelaceae, Rhodophyta) from Jeju Island, Korea

The genus Pterosiphonia is composed of 22 species worldwide and four of these species have been reported in the North-East Asia. In Korea, P. pennata originally described from the Mediterranean Sea has been previously recorded from the southern coast as a widespread species. In order to confirm the same species from Korea and Mediterranean, we observed the morphology of Korean Pterosiphonia specimen and analyzed rbcL sequences for inferring phylogenetic relationships among similar congeners. Korean entity was recognized as a new species, Pterosiphonia arenosa sp. nov. The new species is characterized by ecorticate axes with 7-10 pericentral cells, branches formed every two segments, and coalesced with main axis over 1-1.25 axial segments, and tetrasporangia formed in straight series on determinate branches of the upper parts of erect axes. A phylogenetic analysis of rbcL sequences demonstrated that P. arenosa was distinct from P. pennata found in Spain as well as other species. In conclusion, morphological and molecular sequence data indicated that P. arenosa sp. nov. has been previously misidentified as P. pennata in Korea.

Ceramium cormacii sp. nov. (Ceramiaceae, Rhodophyta), a new Mediterranean species epizoic on loggerhead sea turtles (Caretta caretta)

Abstract Ceramium cormacii is newly described based on both vegetative and tetrasporangial features of specimens growing on loggerhead sea turtles (Caretta caretta) from the Mediterranean Sea. The new species is characterised by both prostrate and erect axes (9–12 mm high), dichotomously to pseudo-dichotomously branched with apices straight or slightly incurved, attached to the substratum by unicellular rhizoids often terminating in multicellular pads, incomplete cortication formed by one to three rows of acropetal cells, five to six periaxial cells, and tetrahedral tetrasporangia produced by periaxial cells, strongly protruding and partially involucrated.

Ochtodes searlesii sp. nov. (Gigartinales, Rhodophyta), from the Pacific tropical coast of Mexico, based on morphological and molecular evidence

SUMMARYOchtodes searlesii Mendoza‐González, Mateo‐Cid et Sentíes sp. nov. is described from Michoacán, tropical Mexican Pacific, on the basis of comparative morphology and rbcL sequence analysis. It is distinguished from other Ochtodes species by its erect axes arising from an encrusting base, its small terete fronds, regularly dichotomously branched axes, and obliquely divided zonate tetrasporangia. Phylogenetic analyses showed that three Pacific Mexican samples, from Caletilla, Zapote and La Majahuita (Michoacán), were identical and formed a distinctive and well supported Clade segregated from other species of Ochtodes from Brazil, Cuba, Ecuador, Guadeloupe and Mexico. The Mexican entity is morphologically distinct from other Ochtodes species as well. On this basis we propose a new Ochtodes species.

Effects of light and temperature on the attachment and development of Gloiopeltis tenax and Gloiopeltis furcata tetraspores

Two 60-day experiments were conducted to study the influence of photon flux density (PFD) and temperature on the attachment and development of Gloiopeltis tenax and Gloiopeltis furcata tetraspores. In the first experiment, tetraspores of the two Gloiopeltis species were incubated at five temperature ranges (8°C, 12°C, 16°C, 20°C, 24°C) under a constant PFD of 80 μmol photons m−2 s−1 with a photoperiod of 12:12. In a second experiment, tetraspores were incubated under five PFD gradients (30, 55, 80, 105, 130 μmol photons m−2 s−1) at a constant temperature of 16°C with a photoperiod of 12:12. Maximum density of attached tetraspores was observed at 16°C for both species. Maximum per cent of spore germinating into disc was recorded at 12–16°C for G. tenax and 8–12°C for G. furcata. Maximum per cent of discs producing erect axes for G. tenax and G. furcata were recorded at 24°C and 20°C, respectively. Light had no significant effect on tetraspore attachment and developing into disc, but it affected the growth, sprouting and survival of its discs. Under 30–55 μmol photons m−2 s−1, the discs of the two species of Gloiopeltis did not form thallus until the end of the experiment. Optimum PFD range for G. tenax discs was 80–105 μmol photons m−2 s−1, whilst it was 80–130 μmol photons m−2 s−1 for G. furcata. Results presented in this study are expected to assist the progress of artificial seeding of Gloiopeltis.

The effects of coalescence on survival and development of Mazzaella laminarioides (Rhodophyta, Gigartinales)

The potential benefits associated with coalescence in red algae have been best documented with early stages of development. In this study, we report on the effects of the original number of spores on branching and fertility during later stages of development. Measurements for 20 months of survival rates, field growth, and fertility of a set of 96 sporelings produced in the laboratory with different number of spores, and outplanted at mid levels of the Mazzaella laminarioides belt at a locality in central Chile, indicate significant differences between multisporic holdfasts (50 and 100 coalescing spores) and uni- or oligosporic (ten spore) holdfasts in the number of branches and erect axes produced 10 and 15 months after germination. The difference is related to the persistence of clusters of axes and branch initials in deep portions of holdfasts of multisporic plantlets and their absence from equivalent portions of uni- or oligosporic holdfasts. This is an example in macroalgae of an event occurring during germination and expressing its effects in the next growing season (some 10 months after).