In order to determine whether truly pico-sized adult radiolarians exist, we compared spumellarian sequences from individual adult samples collected in the central Pacific, with filtered sea water samples of juvenile (5–42 μm) and gamete (0.2–5 μm) sized fractions to see whether the gene sequences are similar or different. Environmental spumellarian-affiliated sequences we sampled were mostly concentrated in samples from 250 to 400 m depth and only appeared in the RAD-III clade, which corresponds to the family Astrosphaeridae (including Arachnosphaera, Astrosphaera, and Cladococcus). None of the same ITS (internal transcribed spacer) sequences were found in both filter membranes of the same sea water samples. Pairwise distances among these environmental spumellarian-affiliated sequences are within or slightly above the range of intra-morphospecific variations. We propose a model to explain our observations based on the hypothesis that the “pico-sized radiolarians” represent gametes of radiolarians of normal size, assuming different sinking speeds of parents and offspring.

为了确定是否存在真正的皮大小的成年放射虫，我们将太平洋中部收集的成年个体样品的散发菌序列与少年（5–42μm）和配子（0.2–5μm）大小级分的过滤海水样品进行了比较看看基因序列是相似还是不同。我们采样的与环境spumellarian相关的序列大多集中在深度为250至400 m的样本中，并且仅出现在RAD-III进化枝中，该进化枝对应于Astrosphaeridae科（包括Arachnosphaera，Astrosphaera和Cladococcus））。在相同海水样品的两个滤膜中均未发现相同的ITS（内部转录间隔子）序列。这些环境spumellarian关联的序列之间的成对距离在形态内特异变异的范围内或略高。我们提出了一个模型来解释我们的观察结果，基于以下假设：假设父母和后代的下沉速度不同，“皮大小的放射虫”代表正常大小的放射虫的配子。