Genome size is a fundamental characteristic of the cell and is associated with a number of key features of the organism, such as cell size, division rate or metabolic rate. Knowledge of the genome size is also a prerequisite for many areas of research (e.g. selection of suitable organisms for whole genome sequencing or cell cycle analysis). However, genome size analysis in microalgae is often difficult and involves many methodological challenges. As a result, genome size data for microalgae are largely lacking. In this study, we focused on fragile, poorly growing colonial chrysophytes. We analysed their genome size using flow cytometry and tested the difference between colonial and solitary living chrysophytes on all published genome size data using analysis of variance. We successfully established nine cultures that were further determined to belong to six species of colonial chrysophytes. We estimated their genome size to be on average 0.24 pg & centerdot;cell-1 for Chrysosphaerella longispina Lauterborn, 1.70 pg & centerdot;cell-1 for Neotessella lapponica (Skuja) B.Y.Jo, J.I.Kim, W.Shin, P.& Scaron;kaloud & P.A.Siver, 0.25 pg & centerdot;cell-1 for Uroglenopsis turfosa (Skuja) R.H.Thompson & D.E.Wujek, 0.31 pg & centerdot;cell-1 for Urostipulosphaera articulata (Korshikov) Pusztai & & Scaron;kaloud, 0.22 pg & centerdot;cell-1 for U. granulata Pusztai & & Scaron;kaloud and 0.19 pg & centerdot;cell-1 for U. lindiae (Bourrelly) Pusztai & & Scaron;kaloud. It was also shown that colonial chrysophytes have larger genomes compared to solitary living species. This study further revealed the smallest genome among colonial chrysophytes, belonging to Urostipulosphaera lindiae. Nevertheless, colonial chrysophytes have lower variance in genome size, possibly due to evolutionary constraints on cell size (and genome size) variation to maintain the functionality of the whole colony movement.
Chara braunii C.C.Gmelin, C. pseudohydropithys Imahori, and Nitella laotica R.E.Romanov, V.Yu Nikulin, K.-G.Bernhardt & A.A.Gontcharov, sp. nov. are reported for Laos. These records seem to be the first species records of charophytes for the country. Chara pseudohydropithys is lectotypified here and described in detail. It is the first record for Southeast Asia, extending its distribution range from mainland China, Taiwan, India, and Brazil. We mention this first record of C. braunii which is a frequently reported species in well-studied regions of Southeast and East Asia, because of the complete absence of records of charophytes from Laos. Nitella laotica sp. nov. is described as a new species using integrative taxonomy. The plants of N. laotica sp. nov. are macrodactylous, homoclemous, with mostly two-furcated branchlets, some branchlets one-two-or two-three-furcated, with or without central secondary ray within the same thallus and the same whorl, without accessory branchlets originating from central secondary rays or any furcation of branchlets, with bicellular dactyls and conical and mucronate end cells, solitary conjoined gametangia at first and more frequently at second furcation of branchlets, with reticulate ornamentation on both oospore surface and low spiral striae. The formation of ripe oospore surface is tentatively outlined for N. laotica sp. nov. This species is similar to N. oligospira A.Braun, a species distinctly different in morphology, in rbcL and ITS rDNA data. Further studies of charophytes are essential for Laos because the three species found there do not correspond to the species richness that can be expected for charophytes in a tropical country with a humid climate.
The systematic status of the newly proposed genus Stirkia Barros-Barreto & Maggs and its relationship to the currently accepted name Ceramothamnion H.Richards remain uncertain because no authentic specimens of the generitype C. codii H.Richards from the type locality in Bermuda have been sequenced. To clarify the taxonomy of C. codii, we performed high-throughput sequencing on a topotype, a 1912 Phycotheca Boreali-Americana (P.B.-A.) specimen collected by F.S. Collins. The rbcL, COI-5P and LSU genetic markers from the P.B.-A. specimen were assembled and used to infer gene and multi-gene phylogenies to determine its phylogenetic history. In all analyses, the topotype of C. codii was closely allied with C. fujianum Barros-Barreto & Maggs, the generitype of Stirkia, as well as with other species of Ceramothamnion from the southwestern Atlantic and Pacific Oceans. These data support the relegation of the genus Stirkia to Ceramothamnion and indicate that the only previously published DNA sequences of C. codii, from Hawai'i, represent a different, presumably undescribed species of Ceramothamnion. They also highlight the power of whole genome sequencing and the need to analyse type, topotype, or historically authentic herbarium specimens to ensure the accurate application of algal binomials.
We report on a new record of Sargassum hornschuchii C.Agardh in the Spanish Mediterranean after having no reports for more than a century. Sargassum hornschuchii was found in a deep-water rocky bottom offshore Menorca together with the kelp Laminaria rodriguezii Bornet and the rockweed Ericaria zosteroides (C.Agardh) Molinari & Guiry. We make an accurate morphological description and provide pictures of the specimens collected. This new record puts into question the assignment of the IUCN "extinct" category for deep-water rare macroalgae as they can go unnoticed for a long time. This also highlights the need to protect remote deep-water spots where biodiversity can still be flourishing.
Crypsis-high morphological similarities of adult thalli of distinct species of algae-is a common challenge in algal taxonomy, where multiple taxa are characterized as the same species due to identical morphologies. Algal genera with cryptic species and similar morphologies may contain underestimates of both diversity and endemism. Extensive studies of Mesophotic Coral Ecosystems (MCEs; from c. 30 to >150 m depths) have revealed high levels of endemism in the Hawaiian Archipelago using DNA sequence-based analyses augmented by morphological analyses. Here, we characterize specimens collected from both the Papah & amacr;naumoku & amacr;kea Marine National Monument and the Main Hawaiian Islands corresponding to the genus Gloiocladia J.Agardh; previous reports from Hawai'i included only a single subtidal species (G. iyoensis (Okamura) R.E.Norris). Phylogenetic analyses using both plastidial (ribulose-1.5-biphosphate carboxylase/oxygenase) and mitochondrial (cytochrome oxidase subunit 1) markers revealed three clades of Hawaiian specimens with strong sequence divergence. However, the gross morphology of these specimens was nearly identical, except for small differences in the number of layers and sizes of cortical and medullary cells, which can easily be overlooked. This study extended the depth record of G. iyoensis to 63 m (aside from a previous report of a dredge sample from 66 m) and revealed one new species exclusive to MCEs (described here as G. laukuamoo K.R.Allsopp, F.P.Cabrera & A.R.Sherwood, sp. nov.), as well as one new intertidal species (formal description awaiting analysis of further collections) present in the Hawaiian Archipelago, including the Papah & amacr;naumoku & amacr;kea Marine National Monument (PMNM) and the Main Hawaiian Islands.
