Jordano Mayara de A, Nagata Renato M, Morandini André C
Departamento de Zoologia, Instituto de Biociências, Universidade de São Paulo, Rua do Matão, trav. 14, n. 101, São Paulo, 05508-090, Brazil.
Instituto de Oceanografia, Universidade Federal do Rio Grande, Av. Itália, km 8, Rio Grande, 96203-000, Brazil.
Biol Rev Camb Philos Soc. 2024 Jun;99(3):950-964. doi: 10.1111/brv.13052. Epub 2024 Feb 2.
Cilia are widely present in metazoans and have various sensory and motor functions, including collection of particles through feeding currents in suspensivorous animals. Suspended particles occur at low densities and are too small to be captured individually, and therefore must be concentrated. Animals that feed on these particles have developed different mechanisms to encounter and capture their food. These mechanisms occur in three phases: (i) encounter; (ii) capture; and (iii) particle handling, which occurs by means of a cilia-generated current or the movement of capturing structures (e.g. tentacles) that transport the particle to the mouth. Cilia may be involved in any of these phases. Some cnidarians, as do other suspensivorous animals, utilise cilia in their feeding mechanisms. However, few studies have considered ciliary flow when examining the biomechanics of cnidarian feeding. Anthozoans (sessile cnidarians) are known to possess flow-promoting cilia, but these are absent in medusae. The traditional view is that jellyfish capture prey only by means of nematocysts (stinging structures) and mucus, and do not possess cilia that collect suspended particles. Herein, we first provide an overview of suspension feeding in invertebrates, and then critically analyse the presence, distribution, and function of cilia in the Cnidaria (mainly Medusozoa), with a focus on particle collection (suspension feeding). We analyse the different mechanisms of suspension feeding and sort them according to our proposed classification framework. We present a scheme for the phases of pelagic jellyfish suspension feeding based on this classification. There is evidence that cilia create currents but act only in phases 1 and 3 of suspension feeding in medusozoans. Research suggests that some scyphomedusae must exploit other nutritional sources besides prey captured by nematocysts and mucus, since the resources provided by this diet alone are insufficient to meet their energy requirements. Therefore, smaller particles and prey may be captured through other phase-2 mechanisms that could involve ciliary currents. We hypothesise that medusae, besides capturing prey by nematocysts (present in the tentacles and oral arms), also capture small particles with their cilia, therefore expanding their trophic niche and suggesting reinterpretation of the trophic role of medusoid cnidarians as exclusively plankton predators. We suggest further study of particle collection by ciliary action and its influence on the biomechanics of jellyfishes, to expand our understanding of the ecology of this group.
纤毛广泛存在于后生动物中，具有多种感觉和运动功能，包括在悬浮取食动物中通过摄食流收集颗粒。悬浮颗粒密度低且体积太小，无法单独捕获，因此必须进行浓缩。以这些颗粒为食的动物已经进化出不同的机制来获取和捕获食物。这些机制分为三个阶段：（i）相遇；（ii）捕获；以及（iii）颗粒处理，颗粒处理通过纤毛产生的水流或捕获结构（如触手）的运动来实现，这些结构将颗粒输送到口中。纤毛可能参与这些阶段中的任何一个。一些刺胞动物，与其他悬浮取食动物一样，在其摄食机制中利用纤毛。然而，在研究刺胞动物摄食的生物力学时，很少有研究考虑纤毛流。已知珊瑚虫（固着型刺胞动物）具有促进水流的纤毛，但水母中没有。传统观点认为，水母仅通过刺丝囊（刺蛰结构）和黏液捕获猎物，并不拥有收集悬浮颗粒的纤毛。在此，我们首先概述无脊椎动物的悬浮取食，然后批判性地分析刺胞动物门（主要是钵水母纲）中纤毛的存在、分布和功能，重点是颗粒收集（悬浮取食）。我们分析悬浮取食的不同机制，并根据我们提出的分类框架对其进行分类。我们基于此分类提出了一个远洋水母悬浮取食阶段的方案。有证据表明，纤毛会产生水流，但仅在钵水母纲动物悬浮取食的第1阶段和第3阶段起作用。研究表明，一些钵水母除了通过刺丝囊和黏液捕获的猎物外，必须利用其他营养来源，因为仅靠这种食物提供的资源不足以满足它们的能量需求。因此，较小的颗粒和猎物可能通过其他可能涉及纤毛流的第2阶段机制捕获。我们假设，水母除了通过触手和口腕上的刺丝囊捕获猎物外，还能用纤毛捕获小颗粒，从而扩大它们的营养生态位，并表明需要重新解释钵水母纲刺胞动物作为单纯浮游生物捕食者的营养作用。我们建议进一步研究纤毛作用收集颗粒及其对水母生物力学的影响，以扩展我们对这一群体生态学的理解。
