Two new marine species of Cocconeis (Bacillariophyceae) from the west coast of Sweden

Adil Y Al-Handal,Alison Minerovic,Regine Jahn,Angela Katarina Wulff,Catherine Riaux-Gobin

doi:10.5852/ejt.2019.497

Abstract

This paper is part of a project of studying benthic diatom biodiversity on marine coastal regions of Sweden with focus on rare and less known species. Two new species of Cocconeis Ehrenb. are described from Vrångö, a small island in the west coast of Sweden. Both species were found as epiphytic on the green alga Ulva intestinalis L. Cocconeis magnoareolata Al-Handal, Riaux-Gob., R.Jahn & A.K.Wulff sp. nov. is a small species not exceeding 9 µm in length and characterized by having large subquadrangular areolae on the sternum valve. Cocconeis vrangoensis Al-Handal & Riaux-Gob. sp. nov. appears similar to some taxa of the ‘Cocconeis scutellum complex’, but differs by its stria density on both valves and variable features of the areola and valvocopula ultrastructure. Detailed descriptions based on light and electron microscopy examination, a comparison with closely related taxa, as well as a description of the habitat of both species are here presented.

Highlights

Cocconeis Ehrenb. is one of the most diversified genera of diatoms in terms of number of species and variability of habitats
Several taxa of Cocconeis were observed in moderate densities such as C. scutellum Ehrenb., C. stauroneiformis (W.Sm.)
Cocconeis magnoareolata sp. nov. with its large areolae may be compared to C. arenicola Ryznik, described from tidal flats in the Yaquina Estuary, USA, but the later differs by having larger valves (22–27 × 17–20 μm) and by its striae density, almost one third of that in our new species (7 vs 21–22 in 10 μm)

Summary

Introduction

Cocconeis Ehrenb. is one of the most diversified genera of diatoms in terms of number of species and variability of habitats. Several works attempted to typify such species by examining fine structure of type material and compare it with recent specimens examined under electron microscopy (e.g., De Stefano et al 2008; Jahn et al 2009). One of such problematic species is C. scutellum Ehrenb., with ca 15 varieties being separated on the basis of the fine structure of the areolae and valvocopulae (De Stefano et al 2008). Such distinction between several varieties is important in the context of biodiversity, but it seems rather unhelpful in ecological surveys where morphological features may not appear different using light microscopy

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