原始虫的内解剖学及其对早期鱼进化的影响
Elena Berger1, Eli Amson1, Emanuele Peri2
1Staatliches Museum für Naturkunde Stuttgart, Germany.
概括
早期的鱼进化了更大的大脑,并保留了强烈的嗅觉,同时仍然部分生活在陆地上. 这挑战了关于在过渡到水生生物期间嗅觉减少的时间的假设.
科学领域:
- 古生物学的古生物学
- 进化生物学 进化生物学
- 神经科学是一个神经科学.
背景情况:
- 类动物 (鱼,海豚,海豚) 经历了从陆地向完全水生生物的重大转变.
- 这一宏观进化转变涉及到感官系统的重大变化,包括大脑大小和嗅觉.
- 现代鱼表现出高的脑分化率 (大脑大小与身体大小相比),特别是有牙的鱼,而嗅觉能力被认为已经下降.
研究的目的:
- 研究早期鱼的脑分化系数和嗅觉系统.
- 为了确定鱼过渡到水生生物的过程中嗅觉减少的时间.
- 为鱼感官系统的进化提供新的见解.
主要方法:
- 使用高分辨率计算机断层扫描 (CT) 分析灭绝的鱼Protocetus atavus的内解剖学.
- 与其他早期的类动物和现存的哺乳动物对Protocetus atavus内解剖学的比较.
- 在Protocetus atavus中评估脑化系数和嗅觉球泡大小.
主要成果:
- 一个早期的半水生鱼,Protocetus atavus,已经拥有增加的大脑化系数.
- 原生的嗅觉器官发达得很好,这表明嗅觉仍然很重要.
- 有证据表明,在这个早期的类动物中,嗅觉减少还没有受到强大的选择性压力.
结论:
- 鱼大脑大小的增加比以前假设的更早发生.
- 像Protocetus atavus这样的早期类动物在半水生阶段保持了功能性的嗅觉系统.
- 过渡到水生生物的过程中,感官系统的演变比以前所认为的要慢得多.
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