小丑鱼中不同条纹类型是如何演化的?-福建海洋渔业科学馆
《海底总动员》让大家认识了尼莫。尼莫橘黄色身体上的3段白色条纹,让它看起来既像西方的小丑,又像京剧丑角,所以,人们又叫它“小丑鱼”。
最近,尼莫身上憨态可掬的条纹,引起了科学家的好奇——这些条纹是从哪来的?9月4日,《生物学杂志》刊发了一篇研究论文,为上述问题给出了答案。
此次发表的研究成果解释了小丑鱼中不同条纹类型的演化,以及不同种群里个体在长大过程中身上的条纹是怎么变化的。
小丑鱼属于珊瑚鱼的一种,目前,珊瑚鱼已经演化得五彩缤纷,可有趣的是,人们至今不明白这些颜色是怎么进化而来的,以及这些颜色在鱼的一生中是怎么形成的。
“小丑鱼的祖先原本拥有3道白色条纹,之后,它们在进化中丢失了一些条纹。我们发现,物种进化过程中条纹的丢失,与如今不同物种个体中不同条纹模式的发展之间存在惊人的相似之处。”论文通讯作者、法国索邦大学博士Vincent Laudet说。
科研人员对两种小丑鱼进行了研究,一种是像尼莫一样有3条条纹的小丑鱼,即“眼斑双锯鱼”;另一种只有头上有1条条纹,被称为“番茄小丑鱼”。
他们发现,当两种小丑鱼都还是刚孵化出来的“小宝宝”时,它们身上都没有条纹。随后,两种小丑鱼同时在头部和躯干上长出了条纹烙印残妻。再后来,眼斑双锯鱼在尾部附近渐渐长出了第三条条纹,而番茄小丑鱼在即将成年之前渐渐失去了躯干上的条纹。
科研人员还研究了另外26种小丑鱼的发育情况,他们观察到,蒋申 至少有9种小丑鱼像番茄小丑鱼一样,幼年比成年时条纹多。
有趣的是黄丹仪 ,现存的每一种小丑鱼出生后,条纹都是从前往后长的,其中一些物种个体在长大成年的过程中,又会从后往前失去条纹。“这和小丑鱼进化历史中的条纹消失过程类似。”Laudet说。
不仅如此,虽然小丑鱼的条纹从0到3条不等,但条纹的组织方式十分有限。“你永远也找不到只在尾巴上有一条条纹的小丑鱼,或者一条条纹在头上、一条条纹在尾巴上的小丑鱼。”Laudet说。
Fig. 1
Adult color patterns of clownfish species. Pictures of adult clownfishes classified depending on their color patterns.aNo vertical stripe,bone vertical stripe on the head,ctwo vertical stripes (one on the head, the other on the body),dthree vertical stripes (one on the head, one on the body trunk, and the last one on the peduncle),efishes having stripes polymorphism
Fig. 2
Successive caudo-rostral loss of stripes during evolution. Phylogenetic tree of clownfishes from Litsios et al. 2014 with a summary map of white stripe number histories generated through stochastic character mapping. This trait mapping shows that the diversification of white striped pattern is a history of loss from an ancestral clownfish having three stripes and that these losses occurred in a progressive and sequential fashion from caudal to rostral. Circles at the tips of the tree indicate each species striped pattern and circles at every internal nodes give probabilities of ancestral striped pattern
那么,这种神奇的变身术是怎么完成的?科研人员决定从分子层面一探究竟。
于是,他们对小丑鱼幼鱼使用了一种用于抑制斑马鱼条纹发育的物质周秋波 。这种物质会作用于虹彩细胞中的一些受体,而虹彩细胞是动物表皮中的一种细胞,可以让动物体表呈现各种光泽。
结果,他们发现,处理后的幼鱼没有完全发育出本应发育出的条纹,由于使用剂量不同,一些幼鱼连一条条纹都没有长出来。
这一发现表明,小丑鱼身上的条纹是通过虹彩细胞产生的,而且虹彩细胞的减少会抑制条纹的形成。
“因为珊瑚鱼提供了复杂颜色图案,为理解复杂图案的起源提供了独特的机会。揭示为什么珊瑚鱼的颜色模式如此多样、它们是如何进化的郭思语 ,以及它们是从哪里开始多样化的张明高,将有助于我们理解非常复杂的表型的形成。”Laudet说。
Fig. 3
Ontogeny of stripe formation reveals a rostro-caudal stereotyped pattern.A.ocellaris(a–c′ and g) andA.frenatus(d–f′ and h) color pattern ontogenesis at 8 dph (a-a′, d-d′,A.ocellaris:n= 10;A.frenatus:n= 3), 11 dph (b-b′吕教主 , e-e′,A. ocellaris:n= 10;A.frenatus: n = 3), 14 dph (c-c′, f-f′,A. ocellaris:n= 10;A. frenatus:n= 3) and 6months post hatching (g and h,n= 5). Higher magnification of the medial white stripe ontogenesis (a′, b′, c′, d′玛德来娜公主 , e′, f′). Note that the white stripes appear in the same rostral to caudal sequence in both species. Scale bars correspond to 1mm
Fig. 4
Cellular mechanism of color pattern ontogenesis inA.ocellaris.a–dDose-dependent modifications of color pattern (left and middle panel) and iridescence of the eye (right panel) after 13days of TAE684 drug treatment ofA.ocellarisat 18 dph at 0.6μM (d) and 0.3μM (b,c) compared to DMSO (control,a).eCumulative histogram of fishes having fully stripes: one stripe (head—red), two stripes (head and trunk—green)文王梦熊, or three stripes (blue) in control (n= 6), TAE 0.3μM (n= 16) and TAE 0.6μM (n= 3).fStereomicroscope pictures showing the three types of chromatophores within the trunk of juvenileA.ocellaris. (g,h,n= 4). Live imaging pictures of the sameA.ocellarisindividual at 10 dph (g) and 11 dph (h) show that during medial white stripe formation, the distance increases between melanophores underlined with red dots and melanophores underlined with blue dots
Fig. 5
Stripe loss during ontogeny occurs multiple times inAmphiprion.a–fPictures of juveniles (big picture) and adult (small picture-top right) ofA.frenatus(a),A.melanopus(b),A.rubrocinctus(c),A. ephippium(d),A.nigripes(e), andA.sandaracinos(f).A. frenatus(a),A.melanopus(b),A.rubrocinctus(c), andA. ephippium(d) show that juveniles have extra stripes compared to its respective adult whereas the number of vertical stripes does not vary over ontogeny inA.nigripes(e) andA.sandaracinos(f). Pictures of juveniles were nicely provided by GR Allen.gMaximum clade credibility phylogeny of clownfishes [27] with a summary map of striped pattern ontogenesis generated through stochastic character mapping. It reveals a minimum of five major transitions to an ontogenetic pattern made of white stripe loss, occurring (1) in theA.frenatusclade, (5) in the clade groupingA.mccullochiandA.akindynos, and in three individual species (2)A.chrysopterus, (3)A.latifasciatus, and (4)A.allardi(number in red circles)
Fig. 6
Morphological trait analysis reveals a link between striped pattern and shape of the dorsal fin.a–dPictures ofA.ocellaris(a),A.bicinctus(b),A.frenatus(c), andA.ephippium(d) and cartoons illustrating their dorsal fin shape (A anterior, P posterior). There is an indentation at the middle of the dorsal fin (black arrowhead) with the anterior spiny rays longer than the most posterior one in clownfishes having two or three stripes.eMethods for quantification of anterior lobe and posterior lobe morphology index (l1 length of the third dorsal spine, l2 length of the most posterior spine宝丰能源, lr length of the longest soft ray, L length of the dorsal fin was used for normalization). Anterior and posterior lobes morphology indexes correspond to (l1-l2)/L and (lr-l2)/L, respectively.f,gScatterplots showing the relationship between the numbers of vertical white stripes (x-axis) and lobe morphologies index of the dorsal fin (y-axis). Each point corresponds to one clownfish species
对于这项研究,中科院海洋所研究员尤锋评价刘庆新 ,该研究虽是基础研究,但正如海洋生物学研究一样敏德瑞 ,可以为应用提供理论基础。科研人员对小丑鱼条纹机制的探索,不仅可能会为将来类似鱼类的育种提供理论支撑,还将有助于丰富观赏鱼市场。
本文来源:海洋生物多样性