头足类角质颚的色素沉积机制

角质颚是头足类重要的摄食器官,其表面具有特殊的色素沉积。为了探明角质颚色素的沉积机理,本研究分析了角质颚色素沉积程度不同的3种头足类(剑尖枪乌贼、茎柔鱼、曼氏无针乌贼),以及茎柔鱼角质颚色素沉积程度不同部位(喙部、侧壁、翼部)的主要化学成分和碳氮稳定同位素比。结果显示,茎柔鱼角质颚不同部位的蛋白质与儿茶酚含量为喙部>侧壁>翼部,而C/N比值为翼部>侧壁>喙部;3种头足类角质颚中蛋白质与儿茶酚含量为曼氏无针乌贼>茎柔鱼>剑尖枪乌贼,而C/N比值为剑尖枪乌贼>茎柔鱼>曼氏无针乌贼。茎柔鱼角质颚各部位壳聚糖含量与C/N值呈显著正相关,各部位蛋白质含量与C/N值呈显著负相关;3种头足类角质颚C/N随壳聚糖含量增大而增大,C/N随蛋白质含量增大而减小。角质颚C/N增大,则几丁质含量高,蛋白质含量低,对应色素沉积变浅;C/N减小,则几丁质含量低,蛋白质含量高,对应色素沉积变深。研究表明,蛋白质与几丁质含量的高低决定角质颚色素沉积的深浅,这一结论为研究头足类种间食性差异以及个体发育期食性转变提供了基础。

Mechanism analysis of Cephalopod beak pigmentation

Cephalopod beaks,a main feeding structure,is characterized by special formation of pigment.In this study,we analyzed the main chemical composition and carbon-nitrogen stable isotope ratio of whole beaks of three species and different beak parts of Dosidicus gigas with different pigment formation.The results showed that the protein and catechol content in different parts of the beaks were observably different with rostrum>lateral wall>wing,and the C/N ratio is wing>lateral wall>rostrum.The protein and catechol content of three cephalopods were observably different with Sepiella maindroni>D.gigas>Uroteuthis edulis,and the C/N ratio is U.edulis>D.gigas>S.maindroni.There was a significantly positive correlation between chitosan content and the C/N ratio value in different parts of D.gigas’s beak.There was a significantly negative correlation between protein content and C/N value.The C/N of three cephalopods increased with the increasing of chitosan content and the C/N decreased with the increasing of protein content.When the C/N increased,the chitin content was high,the protein content was low and the corresponding pigment became light,while when the C/N decreased,the chitin content was low,the protein content was high and the pigment is dark.Consequently,the degree of pigmentation results from the proportion of protein and chitin,which provides an important basis for investigating specific foraging strategy and individual ontogenetic feeding variation.