Gorzelak Przemysław, Dery Aurélie, Dubois Philippe, Stolarski Jarosław
Institute of Paleobiology, Polish Academy of Sciences, Twarda 51/55, 00-818 Warsaw, Poland.
Laboratoire de Biologie marine, Faculté des Sciences, Université Libre de Bruxelles, CP 160/15, av., F.D.Roosevelt, 50, B-1050 Bruxelles, Belgium.
Front Zool. 2017 Aug 25;14:42. doi: 10.1186/s12983-017-0227-8. eCollection 2017.
Fluorochrome staining is among the most widely used techniques to study growth dynamics of echinoderms. However, it fails to detect fine-scale increments because produced marks are commonly diffusely distributed within the skeleton. In this paper we investigated the potential of trace element (manganese) labeling and subsequent cathodoluminescence (CL) imaging in fine-scale growth studies of echinoderms.
Three species of sea urchins (, sp. and ) were incubated for different periods of time in seawater enriched in different Mn concentrations (1 mg/L; 3 mg/L; 61.6 mg/L). Labeling with low Mn concentrations (at 1 mg/L and 3 mg/L) had no effect on behavior, growth and survival of sea urchins in contrast to the high Mn dosage (at 61.6 mg/L) that resulted in lack of skeleton growth. Under CL, manganese produced clearly visible luminescent growth fronts in these specimens (observed in sectioned skeletal parts), which allowed for a determination of the average extension rates and provided direct insights into the morphogenesis of different types of ossicles. The three species tend to follow the same patterns of growth. Spine growth starts with the formation of microspines which are simultaneously becoming reinforced by addition of thickening layers. Spine septa develop via deposition of porous stereom that is rapidly (within less than 2 days) filled by secondary calcite. Development of the inner cortex in cidaroids begins with the formation of microspines which grow at ~3.5 μm/day. Later on, deposition of the outer polycrystalline cortex with spinules and protuberances proceeds at ~12 μm/day. The growth of tooth can be rapid (up to ~1.8 mm/day) and starts with the formation of primary plates (pp) in plumula. Later on, during the further growth of pp in aboral and lateral directions, secondary extensions develop inside (in chronological order: lamellae, needles, secondary plate, prisms and carinar processes), which are increasingly being solidified towards the incisal end. Interradial growth in the ambital interambulacral test plates exceeds meridional growth and inner thickening.
Mn labeling coupled with CL imaging is a promising, low-cost and easily applicable method to study growth dynamics of echinoderms at the micro-length scale. The method allowed us to evaluate and refine models of echinoid skeleton morphogenesis.
荧光染色是研究棘皮动物生长动态最广泛使用的技术之一。然而，它无法检测到精细尺度的生长增量，因为产生的标记通常在骨骼内分布弥散。在本文中，我们研究了微量元素（锰）标记及随后的阴极发光（CL）成像在棘皮动物精细尺度生长研究中的潜力。
三种海胆（、属物种和）在富含不同锰浓度（1毫克/升；3毫克/升；61.6毫克/升）的海水中孵育不同时间。与高剂量锰（61.6毫克/升）导致骨骼生长停滞相反，低锰浓度（1毫克/升和3毫克/升）标记对海胆的行为、生长和存活没有影响。在阴极发光下，锰在这些标本（在骨骼切片部分观察到）中产生清晰可见的发光生长前沿，这使得能够确定平均延伸率，并直接洞察不同类型小骨的形态发生。这三个物种倾向于遵循相同的生长模式。棘的生长始于微棘的形成，微棘同时通过添加增厚层而得到加强。棘隔板通过多孔骨针状结构的沉积而发育，这种结构在不到2天的时间内迅速被次生方解石填充。头帕目海胆内皮层的发育始于微棘的形成，微棘以约3.5微米/天的速度生长。后来，带有小刺和突起的外多晶皮层以约12微米/天的速度沉积。齿的生长可以很快（高达约1.8毫米/天），始于羽枝中初级板的形成。后来，在初级板向口面和侧面进一步生长的过程中，内部会依次发育出次生延伸结构（顺序为：薄片、针状体、次生板、棱柱和嵴突），这些结构朝着切端逐渐固化。围口区间步带测试板的间辐生长超过子午线生长和内部增厚。
锰标记结合阴极发光成像技术是一种很有前景的、低成本且易于应用的方法，可用于在微观长度尺度上研究棘皮动物的生长动态。该方法使我们能够评估和完善海胆骨骼形态发生模型。
