2010-2013 Ryland et al. UK first Schizoporella japonica records

Schizoporella japonica Ortmann was described from Japan but was subsequently introduced on Pacific oysters to the Pacific coast of North America, where it is now well established. In this paper we record it for the first time in European waters. The initial discovery was in a marina at Holyhead, North Wales, in July 2010 but S. japonica has since been observed abundantly in the Orkney Islands (from May 2011) and, subsequently, at other localities in northern Scotland. Introduction seems most likely to have been on an ocean-going vessel. The British material is here fully described and illustrated with SEMs and colour photographs; some unusual characters are discussed. Unlike other recently introduced bryozoans, S. japonica is a cold-water species and its breeding season in Britain extends through the winter. Extensive confusion between this and other species of Schizoporella on the west coast of Canada and the USA led us to make thorough morphometric comparisons between the species concerned (Schizoporella unicornis (Johnston in Wood), Schizoporella errata (Waters) and Schizoporella pseudoerrata Soule, Soule and Chaney). Zooid size in cheilostomate bryozoans is variable and often an unreliable character for species separation but shape (and therefore ratios between variables,which are independent of size) are often valuable: S. japonica zooids have a much greater length:width ratio than the other species. Density of frontal pseudopores provides a useful discriminatory character. Schizoporella unicornis, repeatedly reported in error from the Pacific coast of North America, does not occur there; it is a European species. Full comparisons are made between S. japonica and S. unicornis for European identification and between S. japonica, S. errata and S. pseudoerrata (which are also illustrated) for North American localities.

日本裂壳藻（Schizoporella japonica Ortmann）原产于日本，但随后引入太平洋牡蛎，在北美太平洋沿岸得以广泛定殖。本文首次记录其在欧洲水域的出现。最初的发现于2010年7月在北威尔士的霍利黑德一个船坞中，但自那时起，S. japonica在奥克尼群岛（自2011年5月起）以及其他苏格兰北部地区的多个地点均有大量出现。其引入很可能是由一艘远洋船只带来的。本处对英国的材料进行了全面的描述，并附有扫描电子显微镜（SEM）和彩色照片进行说明；一些不寻常的特征也得到了讨论。与最近引入的其他石鳃类不同，S. japonica是一种冷水种，其在英国的繁殖季节贯穿整个冬季。与加拿大和北美西海岸的其他Schizoporella物种之间的广泛混淆，促使我们对相关物种（Schizoporella unicornis (Johnston in Wood)、Schizoporella errata (Waters)和Schizoporella pseudoerrata Soule, Soule and Chaney）进行了彻底的形态计量比较。在多板虫类石鳃中，虫体的尺寸存在差异，且常常不是一个可靠的物种鉴别特征，但形状（以及因此变量之间的比率，这些比率与尺寸无关）通常具有很高的价值：S. japonica的虫体具有远大于其他物种的长度：宽度比率。前侧伪孔的密度提供了一个有用的鉴别特征。重复报道出错的Schizoporella unicornis，在太平洋沿岸并不存在；它是一种欧洲物种。为了欧洲的鉴定，对S. japonica和S. unicornis进行了全面比较，并且为了北美地区，对S. japonica、S. errata和S. pseudoerrata（亦附有插图）进行了比较。