ABSTRACT

The Prorocentrales are a unique group of dinophytes based on several apomorphic traits, but species delimitation is challenging within the group. Prorocentrum triestinum was described by Josef Schiller in 1918 as an important bloom-forming species from Trieste (Mediterranean, Adriatic Sea) with a conspicuous asymmetric outline and a small, asymmetrically located subapical spine. All subsequent records under this name fail to conform to Schiller’s original description. These inconsistencies have their origin in John Dodge’s 1975 revision of Prorocentrum, which placed Prorocentrum redfieldii, a more symmetrical, slender species with a long apical spine, into synonymy under P. triestinum. To clarify this confusion, we collected samples at the type locality of P. triestinum in Trieste and established a strain that is morphologically consistent with the protologue and suitable for use in epitypification. Morphology and rRNA sequence data of this strain were compared with four new strains identified as P. redfieldii from the Mediterranean Sea and the North Atlantic Ocean. Cells of P. triestinum had an asymmetric outline in lateral view and a small, dorso-subapical spine. These features, which are readily resolved by light microscopy, were distinct from those of the nearly symmetrical and slender cells of P. redfieldii, which had a long, apically located spine. The species are nevertheless closely related and share an identical architecture of the periflagellar area with a distinctive, largely reduced accessory pore together with a very small platelet 7. This apomorphy clearly differentiates both species from other species of Prorocentrum. Both species differ in their primary rRNA sequences, and ITS and LSU sequence differences will enable them to be distinguished in future meta-barcoding studies. The present study demonstrates that P. triestinum and P. redfieldii are distinct species and thus contributes to a reliable biodiversity assessment of Prorocentrum.

HIGHLIGHTS

Prorocentrum triestinum is characterised molecularly for the first time and delimited from P. redfieldii.

The identity of important bloom-forming species is clarified.

Structural details of the periflagellar area are described.

摘要

Prorocentrales 是一个独特的甲藻类群，基于几个无形性状，但在群内物种划界具有挑战性。1918 年，Josef Schiller 将Prorocentrum tristinum描述为来自的里雅斯特（地中海，亚得里亚海）的一种重要的开花形成物种，具有明显的不对称轮廓和一个小的、不对称的尖下棘。此名称下的所有后续记录均不符合席勒的原始描述。这些不一致源于 John Dodge 1975 年对Prorocentrum的修订版，该修订版将Prorocentrum redfieldii（一种更对称、细长的物种，具有较长的顶端棘）与P. tristinum同义。. 为了澄清这种混淆，我们在的里雅斯特的P. tristinum类型产地收集了样本，并建立了一个在形态上与原体一致并适用于表型鉴定的菌株。将该菌株的形态学和rRNA序列数据与来自地中海和北大西洋的四种新菌株进行了比较。P. tristinum的细胞在侧视图中具有不对称的轮廓和一个小的背侧尖下棘。这些特征很容易通过光学显微镜解决，与P. redfieldii几乎对称和细长的细胞不同，它有一个长而位于顶端的脊椎。然而，这些物种是密切相关的，并且在鞭毛周围区域具有相同的结构，具有独特的、大大减少的副孔以及非常小的血小板 7。这种变形清楚地将这两个物种与其他物种区分开来。这两个物种的主要 rRNA 序列不同，ITS 和 LSU 序列差异将使它们能够在未来的元条形码研究中得到区分。本研究表明P. tristinum和P. redfieldii是不同的物种，因此有助于对Prorocentrum进行可靠的生物多样性评估。

强调

Prorocentrum tristinum 首次在分子上进行了表征，并与P. redfieldii分隔开来。

澄清了重要的开花形成物种的身份。

描述了鞭毛周围区域的结构细节。