THE MORPHOLOGY AND DEVELOPMENT OF SOME PROMINENTLY STALKED SOUTHERN AUSTRALIAN HALYMENIACEAE (CRYPTONEMIALES,RHODOPHYTA). I. CRYPTONEMIA KALLYMENIOIDES (HARVEY) KRAFT COMB. NOV. AND C. UNDULATA SONDER1

Several southern Australian red algae of the family Halymeniaceae (Cryptonemiales) are differentiated into hard, massive stalks and considerably softer laminar blades or phyllodes. The taxonomy, morphology and pit-connection ultrastructure of one such species, Cryptonemia kallymenioides (Harvey) Kraft comb. nov., are compared to C. undulata Sonder, which lacks massive stalks. In both species there is extensive periodic secondary cortication of the stalks, resulting in the formation of distinct “growth rings.” The blades of C. kallymenioides appear to be seasonal and its stalks perennial, while plants of C. undulata are apparently perennial but shorter lived than C. kallymenioides. As a result, stalks in the latter can reach 2–3 cm in diameter with up to 18 growth rings, compared to the 1–2 mm diameters and up to 6 rings within the stalks of C. undulata. Heavy secondary thickening of cortical cell walls occurs in both species and confers a “woody” texture to the stalks of C. kallymeniodes. Regardless of the large differences in average stalk diameters between the two species, the pit-connection ultrastructure from cortex to medulla shows much the same sequence of morphological modification. Pit-connections are standard red algal structures in the outer cortex, but become increasingly convoluted on the membrane-bound surfaces abutting cytoplasm and develop wider apertures and less dense cores with increasing distance from the stalk surface. In occasional medullary cells of C. kallymenioides, the cytoplasm disintegrates, leaving cell walls and pit-connections to play an apparently structural role which has not been reported in other red algae. It is suggested that the increase in aperture size and surface areas of pit-connections is compatible with their playing a role in the intercellular transport of solutes towards the inner cell layers which may, in C. kallymenioides, lie many millimeters distant.     

CONCEPTACLE STRUCTURE OF THE PARASITIC CORALLINE RED ALGA CHOREONEMA THURETII (CORALLINALES) AND ITS TAXONOMIC IMPLICATIONS1

The major diagnostic features for erecting the red algal subfamily Choreonematoideae (Corallinales) were a combination of 1) absence of both cell fusions and secondary pit connections, 2) conceptacle roof and wall comprised of a single cell layer, and 3) presence of tetrasporangial pore plugs within a uniporate conceptacle in the monotypic taxon Choreonema thuretii (Bornet) Schmitz. Because this alga is a parasite, the absence of secondary cell connections is most likely an adaptation to a reduced thallus. This study shows that all conceptacles are not composed of a file of cells but rather a single layer of epithallial cells that are underlain by a thick layer of calcified acellular material; both epithallial cells and the calcified layer are produced by peripheral sterile cells. Although the outermost tetrasporangial pore canal is uniporate, there is a calcified acellular multiporate plate recessed just below the rim. The plate is produced by interspersed sterile cells and is continuous with the calcified layer supporting the conceptacle. These unique structures are likely due to parasitism rather than to the ancestral state. Based on these results and a reexamination of published micrographs depicting lenticular cells in Austrolithon intumescens Harvey et Woelkerling, we propose that both subfamily Choreonematoideae and Austrolithoideae are closely allied with subfamily Melobesioideae. This distant relationship to its host (Corallinoideae) plus a combination of unique conceptacle and unusual type of parasitism indicates that C. thuretii is an alloparasite and that it is likely the most ancient red algal parasite studied to date.     

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.     

Flora Algale Dell'Isola Lachea (Golfo di Catania)

Abstract

Observations on the seaweeds on the Island of Lachea. — Within the frame of the research on seaweeds in the Eastern part of Sicily which is being carried out at the Botanical Department of Catania University, the AA. have undertaken a study on the seaweeds to be found on the Island of Lachea. The material has been collected from the supralittoral to the infralittoral. One hundred and thirty-five species have been identified and data about the local distribution and habitat have been given. The following species are new to Sicily: Spatoglossum solierii (Chauv.) Kuetz., Bonnemaisonia asparagoides (Woodw.) Ag., Gelidiella ramellosa (Kuetz.) Feld. et Ham., Antithamnion cruciatum (C. Ag.) Naeg. var. profundum G. Feld., Antithamnion plumula var. bebbii (Reinsch) J. Feld., Ceramium bertholdi Funk, Ceramium codii (Richards) G. Maz., Spermothamnion repens (Dillw.) K. Ros. var. flagelliferum (De Not.) Feld., Griffithsia barbata (Smith) C. Ag., Polysiphonia biformis Zan., Lophocladia lallemandi (Mont.) Schmitz; and the following species are new to Eastern Sicily: Codium difforme Kuetz., Bryopsis penicillata Kuetz., Liebmannia leveillei J. Ag., Thuretella schousboei (Thur.) Schmitz, Dudresnaya verticillata Le Jol., Amphiroa cryptharthrodia Zan., Corallina squamata Ell. et Sol., Pseudolithophyllum expansum (Phil.) Lem., Ceramium rubrum var. implexo-contortum Solier, Ptilothamnion pluma (Dillw.) Thuret, Aglaothamnion neglectum G. Feld.     

AN EXAMINATION OF PACHYMENIA AND AEODES (HALYMENIACEAE,RHODOPHYTA) IN NEW ZEALAND AND THE TRANSFER OF TWO SPECIES OF AEODES IN SOUTH AFRICA TO PACHYMENIA1

A phylogenetic study was conducted of species of Halymeniaceae from New Zealand presently placed in Aeodes or Pachymenia, based on maximum‐likelihood (ML), maximum‐parsimony (MP), and Bayesian analyses of rbcL and nuclear internal transcribed spacer (ITS) rDNA sequences. We used molecular and morphological data in combination with exhaustive sampling of herbarium collections to clarify the taxonomy and distributions of New Zealand members of Pachymenia and Aeodes. Our study confirms the presence of three erect species of Pachymenia on the New Zealand mainland, and we resurrect the name Pachymenia dichotoma J. Agardh for the widely distributed, southernmost species. Species of Aeodes from South Africa are shown to be closely related to Pachymenia carnosa (J. Agardh) J. Agardh, the type species of Pachymenia, and are accordingly transferred to Pachymenia.     

STRUCTURE AND REPRODUCTION OF NEOARDISSONEA KYLIN (RHODOPHYTA-NACCARIACEAE)1

Neoardissonea naccarioides (J. Ag.) Kylin, the type and only species of its genus, is shown to be referable to Naccaria Endlicher, to which genus it is transferred as Naccaria naccarioides (J. Ag.) comb. nov.     

THE BIOLOGY OF HARVEYELLA MIRABILIS (CRYPTONEMIALES,RHODOPHYCEAE). VI. TRANSLOCATION OF PHOTOASSIMILATED 14C122

Pulse-chase labelling experiments demonstrate that photoassimilated ¹⁴C-bicarbonate is translocated from the host red alga Odonthalia floccosa (Esper) Falkenberg to the parasite Harveyella mirabilis (Reinsch) Schmitz & Reinke. The primary path of translocation is from host cortical cells (the site of photoassimilation) to the erumpent parasite pustule via the zone of interdigitation. The latter is a tissue region in which rhizoidal cells of Harveyella grow between, and establish secondary pit plugs with medullary cells of Odonthalia. A secondary translocation pathway occurs from isolated host cells dispersed in the pustule of Harveyella to adjacent parasite cells.     

PHENOTYPIC PLASTICITY INDUCED IN TRANSPLANT EXPERIMENTS IN A MUTUALISTIC ASSOCIATION BETWEEN THE RED ALGA JANIA ADHAERENS (RHODOPHYTA,CORALLINALES) AND THE SPONGE HALICLONA CAERULEA (PORIFERA: HAPLOSCLERIDA): MORPHOLOGICAL RESPONSES OF THE ALGA1

The association between the red macroalga Jania adhaerens J. V. Lamour. and the sponge Haliclona caerulea is the most successful life‐form between 2 and 4 m depth in Mazatlán Bay (Mexican Pacific). J. adhaerens colonizes the rocky intertidal area and penetrates into deeper areas only when it lives in association with H. caerulea. The aposymbiotic form of the sponge has not been reported in the bay. To understand the ecological success of this association, we examined the capacity of J. adhaerens to acclimate in Mazatlán Bay using transplant experiments. The transplanted aposymbiotic J. adhaerens did not survive the first 2 weeks; however, J. adhaerens when living in association with H. caerulea, acclimated easily to depth, showing no sign of mortality during the 103 d of the experiment. We conclude that the ability of J. adhaerens to colonize in deeper areas in this hydrodynamic environment may in part rely on the protection provided by the sponge to the algal canopy. Both species contribute to the shape of the associated form. Nevertheless, the morphological variation in the association appears to be dominated by the variation in J. adhaerens canopy to regulate pigment self‐shading under light‐limited conditions and/or tissue resistance under high hydrodynamics. Consequently, our results are consistent with light as the abiotic controlling factor, which regulates the lower depth distribution of the association in Mazatlán Bay, through limiting the growth rate of J. adhaerens. Hydrodynamics may determine the upper limit of the association by imposing high mass losses.     

A taxonomic appraisal of Callophyllis and Euthora (Rhodophyta)

Critical examination of the literature and specimens of the three described species of Euthora indicates that the acceptance of the northern species E. cristata (C. Ag.) J. Ag. and E. fruticulosa (Rupr.) J. Ag. has been based on lack of familiarity with the degree of variation normal within one species, and these two species should be united. The carpogonial branch system of this combined species is typical of that found in the genus Callophyllis within which it should therefore be included as Callophyllis cristata (C. Ag.) Kütz. The taxonomic position of the only other species of Euthora, E. tristanensis Baardseth, cannot be determined until information on the carpogonial structure is available.     

THE GENUS HYPOGLOSSUM KÜTZING (DELESSERIACEAE,RHODOPHYTA) IN THE TROPICAL WESTERN ATLANTIC,INCLUDING H. ANOMALUM SP. NOV.1

Observations are made on the occurrence and distribution of the red algal genus Hypoglossum Kützing (Delesseriaceae, Ceramiales) in the tropical western Atlantic. In addition to the type of the genus, H. hypoglossoides (Stackh.) Coll. & Herv., three other species are reported: H. anomalum sp. nov., H. involvens (Harv.) J. Ag., and H. tenuifolium (Harv.) J. Ag. A key is presented to distinguish these four species. The newly described species, H. anomalum, is like other species in the genus in that its branches arise endogenously from the primary axial row but it is unique in that the branches emerge from the parent blade at some point between the midline and the margin of the blade. The new species is reported from Puerto Rico and Florida.     

A morphological and molecular assessment of the genus Prionitis J. Agardh (Halymeniaceae, Rhodophyta)

A critical reassessment of the morphological features of two closely related red algal genera, Grateloupia C. Agardh and Prionitis J. Agardh (Halymeniaceae), shows that members of the two genera share very similar reproductive (including the Grateloupia‐type auxiliary‐cell ampullae) and vegetative characters. Diagnostic features hitherto used for distinguishing these two genera, the texture of blades (lubricous to leathery in Grateloupia vs cartilaginous in Prionitis) and the position of reproductive structures (scattered over the entire blade in Grateloupia vs confined to particular portions of the blade in Prionitis), are continuous across some 75 species of both genera, thus making it difficult to draw a clear‐cut distinction between the two genera. In ribulose‐1,5‐bisphosphate carboxylase/oxygenase gene (rbcL) sequence analyses, the species of Grateloupia and Prionitis, including the two generitypes, constitute a large monophyletic clade in the Halymeniaceae. It is therefore proposed that Prionitis be included in the synonymy under Grateloupia and the appropriate combinations are proposed.     

A PROPOSAL FOR A NEW RED ALGAL ORDER,THE THOREALES1

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.     

COMPARATIVE ALKALINE PHOSPHATASE CHARACTERISTICS OF THE ALGAL BLOOM DINOFLAGELLATES PROROCENTRUM DONGHAIENSE AND ALEXANDRIUM CATENELLA,AND THE DIATOM SKELETONEMA COSTATUM1

The alkaline phosphatase (AP) characteristics of three algal bloom species in the coastal waters of China [Prorocentrum donghaiense D. Lu, Alexandrium catenella (Whedon et Kof.) Balech, and Skeletonema costatum (Grev.) Cleve] were analyzed in a laboratory batch culture experiment using bulk assay and the single‐cell enzyme‐labeled fluorescence (ELF) method. Results showed that the AP of these three test species shared some common characteristics: AP was inducible in all three species and was expressed by algae under phosphorus (P)–stress conditions; no constitutive AP enzyme was detected in the three test species. Once AP was produced, all three test species gradually released the enzymes into the water, and the algae would reinduce AP production. There were also different specific AP characteristics among the three test species under severe P‐stressed conditions. In P. donghaiense, AP covered most of the cell, and the AP production sites were mainly on the cell surface, although some could be observed inside cells. AP also covered the whole cell of A. catenella, but the AP sites were mainly inside the cell with only some on the cell surface. Only one or two AP sites could be detected in S. costatum, and they were all on the cell surface.     

INCORPORATION OF FRESHWATER RHODOPHYTA INTO THE CASES OF CADDISFLIES (TRICHOPTERA) FROM NORTH AMERICA

Cases of larvae and pupae from six caddisfly (Insecta, Trichoptera) genera in three families from North America were observed to contain pieces of freshwater rhodophyte thalli. Seven genera of Rhodophyta, representing 13 species and 35 populations, were observed in this association. Four of the 25 species of Batrachospermum were incorporated into cases of Ochrotrichia ( Hydroptilidae) and Agrypnia ( Phryganeidae). Two of the three freshwater species of Bostrychia were used by Ochrotrichia larvae. Both Compsopogon coeruleus ( Balbis) Mont. and C. prolificus Yadava et Kumano were present in the cases of Hydroptial ( Hydroptilidae) and Ochrotrichia; Compsopogonopsis leptocladus ( Mont.) Krishnamur-thy was observed in the cases of Hydroptila. The more cartilaginous thalli of Lemanea fluviatilis ( L.) C. Ag. and Tuomeya americana ( Kütz.) Papenfuss were used by the brachycentrid larvae of Brachycentrus and Mi-crasema. Lemanea and Paralemanea spp. were also in the cases of Dibusa angata Ross (Hydroptilidae). The architecture of each caddisfly case was studied with light and scanning electron microscopy. Strips of algae were fit together in a transverse, concentric, or spiralled fashion. Based on transmission electron micrographs, cortical cells of Lemanea and Tuomeya in the cases of Brachycentrus and Micrasema appeared to be healthy with intact chloroplasts and typical batrachospermalean pit plugs. Geographic distributions of each rhodophyte-caddisfly association are given .     

DNA BARCODING IS A POWERFUL TOOL TO UNCOVER ALGAL DIVERSITY: A CASE STUDY OF THE PHYLLOPHORACEAE (GIGARTINALES,RHODOPHYTA) IN THE CANADIAN FLORA1

Previous studies have established that the 5′ end of the mitochondrial gene COI (cytochrome oxidase subunit I) is useful for rapid and reliable identification of red algal species and have demonstrated that our understanding of red algal biodiversity and biogeography is fragmentary. In this context, we are completing a thorough sampling along the Canadian coast and using the DNA barcode for the assignment of collections to genetic species to explore algal diversity in the Canadian flora. In the present study, we provide results regarding diversity of members of the red algal family Phyllophoraceae. We have analyzed 354 individuals from the Arctic, Atlantic, and Pacific coasts of Canada, as well as 26 specimens from the USA, Europe, and Australia, resolving 29 species based on the analyses of the DNA barcode. Twenty‐three of these genetic species were present in Canada where only 18 species are currently recognized, including Ceratocolax hartzii Rosenv., which was in the same genetic species group as its host Coccotylus truncatus (Pall.) M. J. Wynne et N. J. Heine and is thus transferred to Coccotylus, C. hartzii (Rosenv.) comb. nov., but retained as a distinct species owing to its unique habit and phenology. Our results revealed the presence of cryptic diversity within the genera Coccotylus, Mastocarpus, Ozophora, and Stenogramme, for which we resurrect Coccotylus brodiei (Turner) Kütz. and describe Mastocarpus pachenicus sp. nov., Ozophora lanceolata sp. nov., and Stenogramme bamfieldiensis sp. nov., leaving a multitude of unnamed Mastocarpus spp. in need of further taxonomic study. In addition, we report range extensions into British Columbia of Besa papillaeformis Setch., previously known only from its type and nearby localities in California; Gymnogongrus crenulatus (Turner) J. Agardh, recorded only from the Atlantic; and Stenogramme cf. rhodymenioides Joly et Alveal, previously only known from South America. Finally, the phylogenetic affinities of the Canadian species of Phyllophoraceae characterized in this study were investigated using LSU rDNA, RUBISCO LSU (rbcL), and combined analyses.     

SEASONAL GROWTH,BIOMASS, AND REPRODUCTIVE BEHAVIOR OF THREE SPECIES OF RED ALGAE IN GODAVARI ESTUARY,INDIA1

Growth and different phases in the life histories of Bos-trychia tenella (Vohl.) J. Ag., Caloglossa leprieurii (Mont.) J. Ag., and Catenella impudica (Mont.) J. Ag. were estimated for 23 months from January 1986 to December 1987 in the Gautami Godavari estuary of lndia. Seasonal data on hydrographical conditions, biomass, and plant length were collected from three stations in this estuary. Biomass was minimum in August and September and maximum in January and February, as was frond length of tetrasporic and vegetative plants. Temperatures of 24°–27°C and salinities of 5–20 ppt coincided with optimal growth for all three algae. In all three species, tetrasporophytes were present in all months of the year without any seasonal periodicity, and nearly 50% of the plants were tetrasporophytes. The gametophytes of B. tenella and C. leprieurii and cystocarpic plants of C. impudica occurred from October to May, with greatest abundance in January. The abundance of spermatangial and cystocarpic plants in the populations of B. tenella and C. leprieurii ranged from 3 to 15%. Spermatangial plants of Catenella impudica could not be identified, and the abundance of cystocarpic plants was very low.     

REVISION OF THE MASTOPHOROIDEAE (CORALLINALES,RHODOPHYTA) AND POLYPHYLY IN NONGENICULATE SPECIES WIDELY DISTRIBUTED ON PACIFIC CORAL REEFS1

The subfamily Mastophoroideae (Corallinaceae, Rhodophyta) is characterized by species possessing nongeniculate, uniporate tetrasporangial conceptacles without apical plugs, the presence of cell fusions, and the absence of secondary pit connections. However, molecular phylogenetic studies not including the type genus Mastophora indicated that the Mastophoroideae was polyphyletic. Our molecular phylogenetic analysis of the subfamily including the type genus using DNA sequences of SSU rDNA and plastid‐encoded gene of PSII reaction center protein D1 (psbA) revealed that Mastophora formed a robust clade only with Metamastophora. The other mastophoroid genera were divided into six lineages within the family Corallinaceae. Five supported lineages—(i) Pneophyllum; (ii) Hydrolithon gardineri (Foslie) Verheij et Prud’homme, Hydrolithon onkodes (Heydr.) Penrose et Woelk., and Hydrolithon pachydermum (Foslie) J. C. Bailey, J. E. Gabel et Freshwater; (iii) Hydrolithon reinboldii (Weber Bosse et Foslie) Foslie; (iv) Spongites; and (v) Neogoniolithon—were clearly distinguished by the combination of characters including the presence or absence of palisade cells and trichocytes in large, tightly packed horizontal fields and features of tetrasporangial and spermatangial conceptacles. Therefore, we amend the Mastophoroideae to be limited to Mastophora and Metamastophora with a thin thallus with basal filaments comprised of palisade cells, tetrasporangial conceptacles formed by filaments peripheral to fertile areas, and spermatangia derived only from the floor of male conceptacles. This emendation supports Setchell’s (1943) original definition of the Mastophoroideae as having thin thalli. We also propose the establishment of three new subfamilies, Hydrolithoideae subfam. nov. including Hydrolithon, Porolithoideae subfam. nov. including the resurrected genus Porolithon, and Neogoniolithoideae subfam. nov. including Neogoniolithon. Taxonomic revisions of Pneophyllum and Spongites were not made because we did not examine their type species.     

SURVIVAL OF FUCOID EMBRYOS IN THE INTERTIDAL ZONE DEPENDS UPON DEVELOPMENTAL STAGE AND MICROHABITAT1

Embryos of the fucoid alga Pelvetia fastigiata (J. Ag.) DeToni were outplanted into the intertidal zone to assess survival during the physical stress brought about by emersion during a single low tide. Survival varied among microhabitats. Under the adult Pelvetia canopy, survival of 6-h-, 24-h-, 48-h-, and 1-wk-old embryos was nearly 100%. Almost all embryos of all ages died in exposed habitats on bare rock or within habitats where the Pelvetia canopy was removed experimentally. However, within red algal turfs, where most juvenile Pelvetia occur, survival was unusually age specific: 24- to 48-h-old embryos survived poorly compared to younger (6 h old) or older embryos (1 wk old). Survival patterns reflected microhabitat temperatures during the experiments. The fate of young post-settlement stages must be studied at these fine temporal and spatial scales to understand the organization of intertidal communities.     

The complete chloroplast genome of Gracilariopsis lemaneiformis (Rhodophyta) gives new insight into the evolution of family Gracilariaceae

The complete chloroplast genome of Gracilariopsis lemaneiformis was recovered from a Next Generation Sequencing data set. Without quadripartite structure, this chloroplast genome (183,013 bp, 27.40% GC content) contains 202 protein‐coding genes, 34 tRNA genes, 3 rRNA genes, and 1 tmRNA gene. Synteny analysis showed plasmid incorporation regions in chloroplast genomes of three species of family Gracilariaceae and in Grateloupia taiwanensis of family Halymeniaceae. Combined with reported red algal plasmid sequences in nuclear and mitochondrial genomes, we postulated that red algal plasmids may have played an important role in ancient horizontal gene transfer among nuclear, chloroplast, and mitochondrial genomes. Substitution rate analysis showed that purifying selective forces maintaining stability of protein‐coding genes of nine red algal chloroplast genomes over long periods must be strong and that the forces acting on gene groups and single genes of nine red algal chloroplast genomes were similar and consistent. The divergence of Gp. lemaneiformis occurred ~447.98 million years ago (Mya), close to the divergence time of genus Pyropia and Porphyra (443.62 Mya).     

Temperature responses of macroalgae from the tropical island Hainan (P.R. China)

The temperature tolerances of 24 tropical macroalgae collected on Hainan Island (P.R. China) were investigated. For some isolates, growth response curves were also determined. The upper survival temperatures (USTs, 32–37°C) of these tropical west Pacific strains are similiar to those of tropical Atlantic species. With regard to their lower survival temperatures (LSTs) the species investigated show high variations: 12 species have LSTs between 16 and 7°C (Hypnea musciformis (Wulfen) Lamx. var esperi J, Ag., Centroceras clavulatum (C. Ag) Mont., Falkenbergia hillebrandii (Bornet) Falkenberg, Gelidiopsis intricata (Ag.) Vickers, Halymenia maculata J. Ag., Hypnea cenomyce J. Ag., Hypnea spinella (C. Ag.) Kütz., Gracilaria changii (Xia et Abott) Abott, Chang et Xia, Dictyopteris repens (Okam.) Boerg., Laurencia cartilaginea Yamada, Gelidium pusillum (Stackh.) Le Jol., Laurencia sp.). Their LSTs and temperature requirements for growth (range: 15–30 °C, optimum: 25–30 °C) are mostly similar to those of tropical west Atlantic and amphi-Atlantic (sub)tropical macroalgae as well as to tropical isolates of species with an Atlantic tropical to warm-temperate distribution. The remaining 12 species have LSTs between 6 and 1 °C (Ulva conglobata Kjellm., Ulva fasciata Delile, Padina boryana Thivy, Dictyosphaeria cavernosa (Forssk.) Boerg., Boodlea composita (Harv.) Brand, Boergesenia forbesii (Harv.) Feldm., Cladophora vagabunda (L.) van den Hoek, Enteromorpha compressa (L,) Grev., Enteromorpha intestinalis (L.) Link, Gracilaria tenuistipitata Chang et Xia, var liui Chang et Xia, Monostroma nitidum Wittr. and Valonia aegagropila C. Ag.). Their LSTs are mostly similar to those of Atlantic macroalgae with a tropical to (warm-) temperate distribution. The results are discussed with respect to the factors which may have triggered the development of the temperature requirements of the various species.