A TAXONOMIC STUDY OF THE GENUS PADINA (DICTYOTALES, PHAEOPHYCEAE) INCLUDING THE DESCRIPTIONS OF FOUR NEW SPECIES FROM JAPAN, HAWAII, AND THE ANDAMAN SEA(1)

Inventory of the Seaweeds and Seagrasses of the Hawaiian Islands

This updated list is composed of a total of 661 records, which includes 71 brown algae, 450 red algae, 137 green algae, and three seagrasses, with an overall rate of endemism of 13.2%. Almost half (46.7%) of the Hawaiian records presented here are represented by at least one DNA sequence, while 16.3% are confirmed through a DNA sequence match to a topotype, and 6.7% are confirmed through a DNA sequence match to a type specimen. The data are presented in the context of the natural history of the Hawaiian Islands, which is heavily influenced by the volcanic hotspot origin of the archipelago in the middle of the Pacific Ocean, as well as the important cultural role of seaweeds and other marine plants in Hawai'i, and the current threats to marine ecosystems, which include the introduction and proliferation of a number of invasive marine macroalgae.

Global Diversity and Geographic Distributions of Padina Species (Dictyotales, Phaeophyceae): New Insights Based on Molecular and Morphological Analyses

The taxonomic status and species diversity of the brown algal genus Padina (Dictyotales, Phaeophyceae) was assessed based on DNA sequences and the morpho-anatomy of specimens collected worldwide, especially from tropical and subtropical western Pacific regions. Phylogenetic analyses using chloroplast rbcL and mitochondrial cox3 gene sequences demonstrated four distinct clades for newly collected samples with high bootstrap support. Each species clade possesses a suite of morphological features that are not shared by any known species of Padina. These are P. imbricata sp. nov., Padina lutea sp. nov., P. moffittianoides sp. nov., and P. nitida sp. nov. The occurrence of these and other species of Padina clearly points to an elevated diversity of the genus in tropical/subtropical waters of the western Pacific. Phylogenetic analyses provided new insights into biogeographic characteristics of the genus, with many species in the Pacific Ocean showing shared/overlapping distributions, whereas species from the Mediterranean/Atlantic and/or the Indian Ocean tend to be confined to particular regions. Consideration has also been given to the evolutionary time frame of the genus Padina based on molecular time trees: a time tree of the concatenated data set (rbcL + cox3) revealed the estimated divergence time in the mid-Cretaceous, whereas those of cox3 and rbcL showed older estimates pointing to the periods of mid-Jurassic and Early Cretaceous, respectively.

Maximizing the Antioxidant Capacity of Padina pavonica by Choosing the Right Drying and Extraction Methods

Marine algae are becoming an interesting source of biologically active compounds with a promising application as nutraceuticals, functional food ingredients, and therapeutic agents. The effect of drying (freeze-drying, oven-drying, and shade-drying) and extraction methods (shaking at room temperature, shaking in an incubator at 60 °C, ultrasound-assisted extraction (UAE), and microwave-assisted extraction (MAE)) on the total phenolics content (TPC), total flavonoids content (TFC), and total tannins content (TTC), as well as antioxidant capacity of the water/ethanol extracts from Padina pavonica were investigated. The TPC, TFC, and TTC values of P. pavonica were in the range from 0.44 ± 0.03 to 4.32 ± 0.15 gallic acid equivalents in mg/g (mg GAE/g) dry algae, from 0.31 ± 0.01 to 2.87 ± 0.01 mg QE/g dry algae, and from 0.32 ± 0.02 to 10.41 ± 0.62 mg CE/g dry algae, respectively. The highest TPC was found in the freeze-dried sample in 50% ethanol, extracted by MAE (200 W, 60 °C, and 5 min). In all cases, freeze-dried samples extracted with ethanol (both 50% and 70%) had the higher antioxidant activity, while MAE as a green option reduces the extraction time without the loss of antioxidant activity in P. pavonica.

Antioxidant Potential of Sulfated Polysaccharides from Padina boryana; Protective Effect against Oxidative Stress in In Vitro and In Vivo Zebrafish Model

Elevated levels of reactive oxygen species (ROS) damage the internal cell components. Padina boryana, a brown alga from the Maldives, was subjected to polysaccharide extraction. The Celluclast enzyme assisted extract (PBE) and ethanol precipitation (PBP) of P. boryana were assessed against hydrogen peroxide (H2O2) induced cell damage and zebra fish models. PBP which contains the majority of sulfated polysaccharides based on fucoidan, showed outstanding extracellular ROS scavenging potential against H2O2. PBP significantly declined the intracellular ROS levels, and exhibited protection against apoptosis. The study revealed PBPs' ability to activate the Nrf2/Keap1 signaling pathway, consequently initiating downstream elements such that catalase (CAT) and superoxide dismutase (SOD). Further, ROS levels, lipid peroxidation values in zebrafish studies were declined with the pre-treatment of PBP. Collectively, the results obtained in the study suggest the polysaccharides from P. boryana might be a potent source of water soluble natural antioxidants that could be sustainably utilized in the industrial applications.

Reproductive morphology and DNA sequences of the brown alga Platysiphon verticillatus support the new combination Platysiphon glacialis

Platysiphon verticillatus, a brown alga endemic to the Arctic, was described based on vegetative specimens collected at Inglefield Bay, West Greenland. The species is distinctive in having a lanceolate blade-like thallus terminated by a terete portion, both covered with hair-like assimilatory filaments. Punctaria glacialis was described from Eastern Greenland, and the species differs from other Punctaria species in lacking hairs and plurilocular zoidangia. Unilocular zoidangia were reported, but instead of zoids being released they formed cell walls in situ developing the appearance of plurilocular zoidangia. However, the fate of the zoids, as well as the walled cells was not traced, and the life history of the alga has remained unclear. By comparing DNA sequences (cox1, cox3, and rDNA ITS2) of specimens morphologically referable to Platysiphon verticillatus and Punctaria glacialis collected at Baffin Island, as well as re-examining morphology and studying crude cultures, we concluded that they are the same taxonomic entity. Furthermore, their cox3 sequence and vegetative morphology agreed with those of the type specimen of Punctaria glacialis. Consequently, we propose Platysiphon glacialis comb. nov. The life cycle could not be completed in culture, but we hypothesize that in situ germination of the unizoids produces reduced gametophytes housed in peripheral tissue of erect sporophytic thalli.

Toward an inordinate fondness for stars, beetles and Lobophora? Species diversity of the genus Lobophora (Dictyotales, Phaeophyceae) in New Caledonia

Until the recent use of molecular markers, species diversity of Lobophora, an ecologically important brown algal genus with a worldwide distribution in temperate and tropical seas, has been critically underestimated. Using a DNA-based taxonomic approach, we re-examined diversity of the genus from New Caledonia in the Southwest Pacific Ocean. First, species were delineated using general mixed Yule coalescent-based and barcoding gap approaches applied to a mitochondrial cox3 data set. Results were subsequently confirmed using chloroplast psbA and rbcL data sets. Species delimitation analyses agreed well across markers and delimitation algorithms, with the barcoding gap approach being slightly more conservative. Analyses of the cox3 data set resulted in 31-39 molecular operational taxonomic units (MOTUs), four of which are previously described species (L. asiatica, L. crassa, L. nigrescens s.l., L. pachyventera). Of the remaining MOTUs for which we obtained a representative number of sequences and results are corroborated across analyses and genes, we described 10 species de novo: L. abaculusa, L. abscondita, L. densa, L. dimorpha, L. gibbera, L. hederacea, L. monticola, L. petila, L. rosacea, and L. undulata. Our study presents an excellent case of how a traditional morphology-based taxonomy fails to provide accurate estimates of algal diversity. Furthermore, the level of Lobophora diversity unveiled from a single locality in the Pacific Ocean raises important questions with respect to the global diversity of the genus, the distributions and range sizes of the individual species, as well as the mechanisms facilitating coexistence.

Species Diversity, Phylogeny and Large Scale Biogeographic Patterns of the Genus Padina (Phaeophyceae, Dictyotales)

The brown algal genus Padina (Dictyotales, Phaeophyceae) is distributed worldwide in tropical and temperate seas. Global species diversity and distribution ranges, however, remain largely unknown. Species-level diversity was reassessed using DNA-based, algorithmic species delineation techniques based on cox3 and rbcL sequence data from 221 specimens collected worldwide. This resulted in estimates ranging from 39 to 61 putative species (ESUs), depending on the technique as well as the locus. We discuss the merits, potential pitfalls, and evolutionary and biogeographic significance of algorithmic species delineation. We unveil patterns whereby ESUs are in all but one case restricted to either the Atlantic or Indo-Pacific Ocean. Within ocean basins we find evidence for the vast majority of ESUs to be confined to a single marine realm. Exceptions, whereby ESUs span up to three realms, are located in the Indo-Pacific Ocean. Patterns of range-restricted species likely arise by repeated founder events and subsequent peripatric speciation, hypothesized to dominate speciation mechanisms for coastal marine organisms in the Indo-Pacific. Using a three-gene (cox3, psaA and rbcL), relaxed molecular clock phylogenetic analysis we estimated divergence times, providing a historical framework to interpret biogeographic patterns.