Jørgensen J M, Locket N A
Department of Zoophysiology, Aarhus University, Denmark.
Proc Biol Sci. 1995 May 22;260(1358):183-9. doi: 10.1098/rspb.1995.0078.
The monotremes, comprising the echidnas and platypus, have more sensory organs in the inner ear than do other mammals. In addition to the organs usually seen in the mammalian inner ear, they have a lagenar macula, a sense organ found in all non-mammalian vertebrates. In the echidna Tachyglossus aculeatus, this macula consists of a narrow sensory strip at the end of the cochlea. All vestibular sensory organs are populated by two types of sensory cells, cylindrical bouton-innervated hair cells and more or less regular bottle-shaped calyceal-innervated hair cells. The two types are mixed in all vestibular organs, as in placental mammals, and their arrangement in the maculae in particular is very unlike that in reptiles. The sensory epithelia are very large relative to the size of the animals. The utricular macula contains more sensory cells than found in any other amniote so far examined.
单孔目动物，包括针鼹和鸭嘴兽，其内耳中的感觉器官比其他哺乳动物更多。除了在哺乳动物内耳中常见的器官外，它们还有一个瓶状囊斑，这是一种在所有非哺乳动物脊椎动物中都能找到的感觉器官。在针鼹（短吻针鼹）中，这个斑由耳蜗末端的一条狭窄的感觉带组成。所有前庭感觉器官都由两种类型的感觉细胞组成，即圆柱形终扣支配的毛细胞和或多或少规则的瓶状杯状支配的毛细胞。这两种类型在所有前庭器官中混合存在，就像在胎盘哺乳动物中一样，而且它们在斑中的排列，尤其是与爬行动物中的排列非常不同。相对于动物的大小而言，感觉上皮非常大。椭圆囊斑所含的感觉细胞比迄今为止所检查的任何其他羊膜动物都要多。
