Pseudo-nitzschia arenysensis Quijano-Scheggia, Garces, Lundholm 2009
Pseudo-nitzschia arenysensis is a newly described species, thus little is known about it's specific biology. To date, it has been found in the pelagic environment of the Mediterranean Sea during late spring. This species has not been found to produce the neurotoxin, domoic acid.
Pseudo-nitzschia arenysensis is a marine, pennate diatom found in the Mediterranean Sea. It is a newly described cryptic species from the Pseudo-nitzschia delicatissima complex.
Cells are linear with apices tapering at the very end of the valve 1.6-2.5 μm wide, 22-59 μm long. A central interspace is present. The fibulae and striae are more or less regularly spaced 20 to 26 fibulae in 10 μm, interstriae 34-43 in 10 μm. Each stria contains two rows of poroids with a density of 7-12 poroids in 1 μm. The first cingular band (valvocopula) contains 40-50 striae in 10 μm, each being subdivided into two, three or four sectors by weakly silicified bridges. The second band had a single row of rectangular poroids, each divided into two sectors. The third band was plain and nonporous. From Quijano-Scheggia et al. 2009
Synapomorphy in helix I of ITS2 of the nuclear rDNA: 5'-GTGTAGTGTATTCGTATTCTATGCCG-3'. This sequence included the CBC that differentiates P. arenysensis and P. delicatissima and an insert that is characteristic of all the strains of P. arenysensis examined or those presently in GenBank. The homologous sequence of the type strain (Læsø 5) of P. delicatissima is 5'-GTCTATTCTGTAGGCTA-3'. A test for how unique the diagnostic signature of P. arenysensis is was confirmatory. The sequence, in a blastn search in GenBank, was found to have an E-value of 4e-05. The next five hits all had E-values of 2.4 and were a cnidarian, an apicomplexan and three higher plants. From Quijano-Scheggia et al. 2009
Batch cultures of P. arenysensis grew exponentially for 5 days and then maintained a stationary phase that lasted for more than 10 days. Longer cells has slower growth rates than shorter cells. Growth rates ranged from 1.2-1.5 μ d-1 (Quijano-Scheggia et al. 2009).
P. arenysensis differs from P. micropora by possessing a central nodule. P. decipiens has a higher density of interstriae and P. dolorosa has a lower density of interstriae and poroids and a wider valve width. The striae of P. dolorosa comprise one to two rows of poroids whereas in P. arenysensis there is always two rows. P. turgidula has a wider valve width, a higher density of fibulae and interstriae and a different valve outline than P. arenysensis. P. arenysensis differs from P. delicatissima in the helix I of ITS2 rDNA (Quijano-Scheggia et al. 2009).
Individual cells in laboratory cultures ranged in size from 41.52-57.65 μm long and 1.83-2.22 μm wide (Quijano-Scheggia et al. 2009).
Phylogenetic analysis of the ITS1, 5.8S and ITS2 regions of the rDNA of several laboratory strains identified as members of the P. delicatissima species complex indicated the existence of two distinct clades of P. delicatissima with P. micropora as a sister clade. One of the P. delicatissima clades was described as the new, cryptic species P. arenysensis. These two P. delicatissima clades have also been observed by Lundholm et al. (2006), Amato et al. (2007) and Kaczmarska et al. (2008).
P. arenysensis is a cryptic species separated from P. delicatissima based on phylogenetic analysis, mating experiments and physiology (Quijano-Scheggia et al. 2009). Prior to being described it was referred to as clade B1 in the literature. The holotype is an acid-cleaned sample of strain ICMB-129 deposited as an SEM stub at the Instituo de Ciencias del Mar, Barcelona, Spain (accession # SQ6-6C). The type locality is near Arenys, Spain 41°34'39.43"N, 2°33'32.51".
P. arenysensis is named after the place of isolation, Arenys, Spain.
Thus far, P. arenysensis has been described only from the Mediterranean Sea, but phylogenetic studies comparing strains from different parts of the world suggest that this species is cosmopolitan in marine environments (Quijano-Scheggia et al. 2009).
P. arenysensis has been observed to reproduce sexually and produce viable offspring. The species is heterothallic, meaning strains of opposite mating types (+ and - or male and female) are needed. Other strains from alternate clades within P. delicatissima did not undergo sexual reproduction when kept at 19-21°C (Quijano-Scheggia et al. 2009). However, this clade did undergo sexual reproduction at a lower temperature, 12°C (Kaczmarska et al. 2008). This suggests that P. arenysensis is separated from the other clade of P. delicatissima by reproductive barriers associated with sexualization at different temperatures and thus different seasons (Quijano-Schieggia et al. 2009).