Amphora subhyalina Podzorski & Hakansson

Amphora subhyalina Podzorski & Håkansson Figs 5–7 Syn.: Amphora insulana Stepanek & Kociolek Ref. illus.: Podzorski & Håkansson 1987, p. 52; pl. 15, fig. 10, pl. 51, figs 7, 8; Stepanek & Kociolek 2018, p. 14, pl. 5, figs 13–16, pl. 8, figs 1–4. Samples: GU44Y-13, GU44Z-15, GU52Q-1a, GU66G-2, GU68A-2 Dimensions: Length 27–45 µm, width 7–8 µm; dorsal striae 36 in 10 µm in the middle increasing to 39 toward the apices, ventral striae 38 in 10 µm. Diagnostics: Valves and copulae frequently forming a hyaline oval pattern in LM. In SEM, more prominent elongated areolae on either side of the dorsal rib with the rest of the dorsal striae comprising small areolae; prominent conopea at the central raphe endings. Comments: As far as we can tell from the SEM illustrations of valves in Podzorski & Håkansson (1987) and Stepanek & Kociolek (2018), the same species is being described and therefore the former name has priority. Although clearly shown in SEM by Stepanek & Kociolek (2018), they did not include a written description of ultrastructure. Podzorski & Håkansson (1987), although showing SEMs, also did not specify stria densities. Our SEM images show dorsal striae of irregular transapical slits, ending with a long, prominent slit at valve margin, mantle sharply delimited by a ridge and bearing a similar series of prominent slits (Figs 6, 7). Small central area on dorsal side of central nodule, and central striae somewhat more prominent. Ventral valve face with single row of slit-like areolae, interrupted by a conopeum developed ventrally and the ventrally deflected raphe. Internally, as shown in Stepanek & Kociolek (2018, pl. 8, fig. 4) the proximal raphe endings are straight. The girdle bands have a single line of slits along the narrow ventral part and faint striae on the wide dorsal part (Fig. 7 arrow). The lack of a ventral raphe ledge is indicative of Halamphora rather than Amphora, as summarized by Stepanek & Kociolek (2018, pp. 8–9 vs 28–29), but the broad girdle bands are indicative of Amphora. Neither Podzorski & Håkansson (1987) nor Stepanek & Kociolek (2018) showed girdle bands. Their materials were, respectively, from Palawan (Philippines) and Florida Keys. These fairly large, hyaline frustules resemble Halamphora hyalina (Kützing) Rimet & R.Jahn (Rimet et al. 2018) and Halamphora pseudohyalina (Simonsen) Stepanek & Kociolek (2018) (neither yet recorded from our region) in the presence of the distinct central area and a ventral surface; H. pseudohyalina has fine dorsal striae 28–30 in 10 µm barely distinguished in LM and ventral striae ca 65 in 10 µm, whereas as H. hyalina and A. vaughanii Giffen have clearly visible striae, 20–23 in 10 µm and 28–30 in 10 µm, respectively. Amphora hyalina, reported from Yap by Navarro & Lobban (2009, figs 97, 98), has an exposed, dorsally deflected raphe with a conopeum extending dorsally on the dorsal raphe ledge; the striae are finely biseriate, the areolae consistently small, apicallyelongated slits. Amphora vaughanii was recorded from Guam (Lobban et al. 2012, pl. 56, figs 7–9), it has biseriate striae of very fine pores on the dorsal surface and a line of very closely spaced slits on the mantle, conopea absent; its position in Halamphora or Amphora has not yet been considered.半透明双眉藻（Amphora subhyalina）Podzorski & Håkansson，图版5~7 异名：岛生双眉藻（Amphora insulana）Stepanek & Kociolek 图解参考文献：Podzorski & Håkansson 1987，第52页；图版15图10、图版51图7、8；Stepanek & Kociolek 2018，第14页，图版5图13~16、图版8图1~4。 标本编号：GU44Y-13、GU44Z-15、GU52Q-1a、GU66G-2、GU68A-2 尺寸：壳长27~45微米，壳宽7~8微米；中部背条纹密度为每10微米36条，向壳端逐渐增至每10微米39条；腹条纹密度为每10微米38条。 鉴别特征：光学显微镜（Light Microscope, LM）下，壳面与连接带（copulae）常形成透明的椭圆形结构；扫描电子显微镜（Scanning Electron Microscope, SEM）下，背肋两侧具更显著的伸长形窝孔（areolae），其余背条纹由小型窝孔构成；壳缝中央末端具显著的壳缝盖（conopea）。 评论：结合Podzorski & Håkansson（1987）与Stepanek & Kociolek（2018）中的壳面SEM图像来看，二者描述的为同一物种，因此较早发表的名称具有优先命名权。尽管Stepanek & Kociolek（2018）在SEM图像中清晰展示了该物种的超微结构，但并未附带文字描述。Podzorski & Håkansson（1987）虽提供了SEM图像，却未明确条纹密度。本次研究的SEM图像显示：背条纹为不规则的跨壳缝缝裂，在壳缘处以长而显著的缝裂收尾；壳套（mantle）以脊棱清晰界定，且带有一系列类似的显著缝裂（图6、7）。壳面中央结节（central nodule）的背侧具小型中央区，中部条纹略显著。腹壳面具单列缝裂状窝孔，被腹侧发育的壳缝盖以及向腹侧弯曲的壳缝所中断。内部结构方面，Stepanek & Kociolek（2018，图版8图4）所示的壳缝近端末端为直形。环带带（girdle bands）在狭窄的腹侧部分具单列缝裂，在宽阔的背侧部分具微弱的条纹（图7箭头所示）。缺乏腹侧壳缝脊（raphe ledge）这一特征符合哈尔曼藻属（Halamphora）而非双眉藻属（Amphora），正如Stepanek & Kociolek（2018，第8~9页与第28~29页）的总结，但宽阔的环带带则是双眉藻属的特征。Podzorski & Håkansson（1987）与Stepanek & Kociolek（2018）均未展示环带带结构。二者的研究材料分别采自菲律宾巴拉望岛与佛罗里达礁岛群。 该类群的硅质壳（frustules）体型较大且呈透明状，因具有清晰的中央区与腹壳面，与透明哈尔曼藻（Halamphora hyalina）(Kützing) Rimet & R.Jahn（Rimet et al. 2018）以及假透明哈尔曼藻（Halamphora pseudohyalina）(Simonsen) Stepanek & Kociolek（2018）（二者在本研究区域均未被记录）相似。假透明哈尔曼藻的背条纹极细，每10微米28~30条，在LM下难以分辨，腹条纹密度约为每10微米65条；而透明哈尔曼藻与沃恩双眉藻（Amphora vaughanii）Giffen的条纹清晰可见，二者的条纹密度分别为每10微米20~23条与28~30条。Navarro & Lobban（2009，图97、98）曾在雅浦岛报道过透明双眉藻（Amphora hyalina），该物种具外露且向背侧弯曲的壳缝，背侧壳缝脊上有向背侧延伸的壳缝盖；其条纹为细双列型，窝孔均为小型、向壳端伸长的缝裂。沃恩双眉藻在关岛已有记录（Lobban et al. 2012，图版56图7~9），其背表面具双列型极细孔隙的条纹，壳套上具一列间距极近的缝裂，无壳缝盖；该物种在双眉藻属与哈尔曼藻属中的分类地位尚未明确。