鱼嘴(fish mouth)也称鱼颚鱼颌(fish jaw),是构成鱼类口腔骨骼软骨肌肉韧带软组织的组合结构,是鱼类消化道呼吸道的开端。绝大多数硬骨鱼有两套颌骨——主要的口颌(oral jaws)负责开合嘴部并吞咬食物,而位于咽部后方的咽颌(pharyngeal jaws)则负责咀嚼吞咽食物[2][3]软骨鱼类(比如鲨鱼鳐鱼)只有由软骨组成的口颌。通常情况下,鱼类的颌骨由关节连接、垂直相对的上颌下颌组成,并且可以拥有规则排列的牙齿。软骨鱼的口颌则会长出数套多次从内向外移动更换的牙齿。

慈鲷头骨中口颌(紫色)和咽颌(蓝色)的侧视图[1]
展现一条幼年扁头恐怖丽鱼下咽颌和口颌中的鳃弓(咽弓)和角鳃硬组织(弓骨)的背视图,白色星号所指的带有牙齿的咽颌(图中的比例尺为500微米[1]

鱼类的颌骨(特别是硬骨鱼)演化出了类似连杆机构的复杂结构,来适应水域生态系统中的各种竞争需求。比较明显的是能够迅速协调的将颌骨向前突出张开的平面四杆机构,使得鱼嘴可以迅速扩大口腔体积并产生负压猎物吸入口中。鱼类的前上颌骨也配有这种结构[4],使得整个鱼嘴拥有三套四杆机构可以前后、上下、左右的口腔直径都产生扩大[4][5][6]

演化

 
鱼类和其它脊椎动物演化纺锤图[7],最早发展出颌部的是已经灭绝的盾皮鱼纲棘鱼纲

鱼嘴的颌骨结构可能来源于支撑无颌鱼类鳃部咽弓(pharyngeal arches)。最早的鱼颌出现在约4亿3000万年前的志留纪的(已灭绝的)盾皮鱼[8]棘鱼之中[9]。拥有可积极开合的颚部最初的选择优势可能并不与进食有关,而是增加呼吸效率——颚部开合产生的“颊泵”(buccal pump)效应可以让更多的新鲜水在单位时间内流过鱼鳃以便增加纳氧量。用开合颌骨进行吞咬很可能只是一个连带产生的副功能,但随后变成了许多从早期鱼类演化出的脊椎动物的主要生存技能,被一些演化生物学家誉为“脊椎动物历史上最深刻并最激进的演化步伐”[10][11]和“至关重要的创新”[12]。相比之下,无颌鱼类的生存难度更高,因此大部分都在三叠纪灭绝没能存活至今,对少数存活至今的圆口纲鱼类(盲鳗七鳃鳗)的研究也没能帮助解释早期颌骨的演化对脊椎动物头骨深层重塑的影响[13][14]

通常的看法是脊椎动物的颌骨与鱼类的鳃弓(branchial arch或gill arches)同源[15],都来自于胚胎阶段发展出的咽弓。无颌鱼的鳃裂开口在嘴后方,由软骨组织支撑,而第一组鳃弓则环绕嘴口。这第一组鳃弓在有颌鱼中发生对折弯曲变成了上下颌;第二鳃弓的上部在则变成了负责将颌骨和颅骨连接的舌颌骨(hyomandibula)[16],在真骨鱼中还负责悬挂鳃盖(operculum)[17]。现在被普遍接受的看法是有颌鱼类的祖先是身上有骨质的甲板覆盖、无颌的甲胄鱼[18][19]

另见

参考

  1. ^ 1.0 1.1 Fraser, G. J.; Hulsey, C. D.; Bloomquist, R. F.; Uyesugi, K.; Manley, N. R.; Streelman, J. T. An ancient gene network is co-opted for teeth on old and new jaws. PLOS Biology. 2009, 7 (2): e1000031. PMC 2637924 . PMID 19215146. doi:10.1371/journal.pbio.1000031. 
  2. ^ Mabuchi, K.; Miya, M.; Azuma, Y.; Nishida, M. Independent evolution of the specialized pharyngeal jaw apparatus in cichlid and labrid fishes. BMC Evolutionary Biology. 2007, 7 (1): 10. PMC 1797158 . PMID 17263894. doi:10.1186/1471-2148-7-10. 
  3. ^ Alfaro, M. E.; Brock, C. D.; Banbury, B. L.; Wainwright, P. C. Does evolutionary innovation in pharyngeal jaws lead to rapid lineage diversification in labrid fishes?. BMC Evolutionary Biology. 2009, 9 (1): 255. PMC 2779191 . PMID 19849854. doi:10.1186/1471-2148-9-255. 
  4. ^ 4.0 4.1 Westneat, Mark W. Feeding mechanics of teleost fishes (Labridae; Perciformes): A test of four-bar linkage models. Journal of Morphology. September 1990, 205 (3): 269–295. PMID 29865760. S2CID 46933606. doi:10.1002/jmor.1052050304. 
  5. ^ Olsen, Aaron M.; Camp, Ariel L.; Brainerd, Elizabeth L. The opercular mouth-opening mechanism of largemouth bass functions as a 3D four-bar linkage with three degrees of freedom. Journal of Experimental Biology. 15 December 2017, 220 (24): 4612–4623. PMID 29237766. doi:10.1242/jeb.159079 . 
  6. ^ Muller, M. A novel classification of planar four-bar linkages and its application to the mechanical analysis of animal systems. Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences. 29 May 1996, 351 (1340): 689–720. Bibcode:1996RSPTB.351..689M. PMID 8927640. doi:10.1098/rstb.1996.0065. 
  7. ^ Benton 2005.
  8. ^ Placodermi: Overview. Palaeos. [10 December 2014]. (原始内容存档于2022-06-28). 
  9. ^ Acanthodii. Palaeos. [10 December 2014]. (原始内容存档于2022-06-28). 
  10. ^ Gai, Z.; Zhu, M. The origin of the vertebrate jaw: Intersection between developmental biology-based model and fossil evidence. Chinese Science Bulletin. 2012, 57 (30): 3819–3828. Bibcode:2012ChSBu..57.3819G. doi:10.1007/s11434-012-5372-z . 
  11. ^ Maisey, J. G. Discovering Fossil Fishes. Westview Press. 2000: 1–223 [2023-01-06]. ISBN 978-0-8133-3807-1. (原始内容存档于2022-06-30). 
  12. ^ Kimmel, C. B.; Miller, C. T.; Keynes, R. J. Neural crest patterning and the evolution of the jaw. Journal of Anatomy. 2001, 199 (1&2): 105–119. PMC 1594948 . PMID 11523812. doi:10.1017/S0021878201008068. 
  13. ^ Janvier, P. Homologies and Evolutionary Transitions in Early Vertebrate History. Anderson, J. S.; Sues, H.-D. (编). Major Transitions in Vertebrate Evolution. Indiana University Press. 2007: 57–121 [2023-01-06]. ISBN 978-0-253-34926-2. (原始内容存档于2022-06-29). 
  14. ^ Khonsari, R. H.; Li, B.; Vernier, P.; Northcutt, R. G.; Janvier, P. Agnathan brain anatomy and craniate phylogeny. Acta Zoologica. 2009, 90 (s1): 52–68. S2CID 56425436. doi:10.1111/j.1463-6395.2008.00388.x. 
  15. ^ For example: (1) both sets of bones are made from neural crest cells (rather than mesodermal tissue like most other bones); (2) both structures form the upper and lower bars that bend forward and are hinged in the middle; and (3) the musculature of the jaw seem homologous to the gill arches of jawless fishes. (Gilbert 2000)
  16. ^ Gilbert. Evolutionary Embryology. 2000 [2022-06-27]. (原始内容存档于2021-09-07). 
  17. ^ Clack, J. A. Earliest known tetrapod braincase and the evolution of the stapes and fenestra ovalis. Nature. 1994, 369 (6479): 392–394. Bibcode:1994Natur.369..392C. S2CID 33913758. doi:10.1038/369392a0. 
  18. ^ Donoghue, P. C.; Purnell, M. A. Genome duplication, extinction and vertebrate evolution. Trends in Ecology & Evolution. 2005, 20 (6): 312–319. PMID 16701387. doi:10.1016/j.tree.2005.04.008. 
  19. ^ Forey, P. L.; Janvier, P. Agnathans and the origin of jawed vertebrates. Nature. 1993, 361 (6408): 129–134. Bibcode:1993Natur.361..129F. S2CID 43389789. doi:10.1038/361129a0. 

额外阅读

外部链接

外部视频链接
  Video of a slingjaw wrasse catching prey by protruding its jaw
  Video of a red bay snook catching prey by suction feeding