The complete lifecycle of the planktonic foraminifera has continued to remain obscure. Benthic foraminifera exhibit an obligate alternation of generations between haploid gamonts and diploid agamonts, yet despite years of observation, the fusion of gametes to form a zygote, gamont or agamont has never been observed in the planktonic groups. Recent evidence from Neogloboquadrina pachyderma culture confirms that they do have a biphasic reproductive cycle and the agamonts may exhibit dimorphism in coiling direction. In this study we examine the morphology of normal and aberrant coiling tests of both N. pachyderma and N. incompta from three Arctic and North Atlantic water masses, to explore whether aberrant coiling is an indicator of a biphasic life cycle in the non-spinose planktonic foraminifera group as a whole. Using a Nano-Computed Tomography scanning approach, we morphologically compared the proloculus and growth trajectories of aberrant and normal coiling tests. Aberrant coiling tests were found to have a slightly larger proloculus and test size, consistent with a left coiling N. pachyderma agamont in the literature. This degree of dimorphism is insufficient to discriminate agamonts in the wild population and coiling direction remains their only distinguishable feature without further morphological investigation. The constant low-level aberrant coiling signature in a range of non-spinose planktonic foraminiferal genera implies that a biphasic life cycle is the principal mode of reproduction in the non-spinose planktonic group.

浮游有孔虫的完整生命周期仍然不清楚。底栖有孔虫在单倍体配子和二倍体配子之间表现出必然的世代交替，然而，尽管经过多年的观察，配子融合形成合子、配子或配子从未在浮游群体中观察到。来自Neogloboquadrina 厚皮藻培养物的最新证据证实，它们确实具有双相生殖周期，并且阿加蒙特可能在卷曲方向上表现出二态性。在这项研究中，我们检查了来自北极和北大西洋三个水团的厚皮猪笼草和不完整猪笼草的正常和异常卷绕测试的形态，以探讨异常卷绕是否是无刺浮游生物双相生命周期的指标。有孔虫类群作为一个整体。使用纳米计算机断层扫描方法，我们从形态上比较了异常和正常卷绕测试的前室和生长轨迹。发现异常卷曲测试具有稍大的前室和测试尺寸，与文献中的左卷曲厚皮猪笼草一致。这种程度的二态性不足以区分野生种群中的阿加蒙，并且在没有进一步形态学研究的情况下，卷曲方向仍然是它们唯一的可区分特征。一系列非刺浮游有孔虫属中恒定的低水平异常卷曲特征意味着双相生命周期是非刺浮游类群的主要繁殖模式。