Toh Y, Sagara H, Iwasaki M
Vision Res. 1983;23(4):313-23. doi: 10.1016/0042-6989(83)90079-2.
The ocellar receptor and neuropil in the dorsal ocellar system of the cockroach and the lateral ocellar system of the swallowtail butterfly larva have been compared. In the dorsal ocellus of the cockroach more than 10,000 retinular cells each with a rhabdomere are piled up one upon another without a specific pattern in the ocellar capsule. Retinular axons synapse exclusively with branches of four thick second order neurons in the lower region of the capsule. Dark granule-containing neurons, originating in the brain, also synapse with the second order neurons in the ocellar neuropil. The ocellar nerve is comprised of four thick second order processes (ca. 6-16 micron) and 20-40 thin processes (ca. 1-5 micron), which include retinular axons, collaterals of thick processes, possible third order processes and unidentified processes. Synapses occur against these processes in the ocellar nerve and in the extreme proximal region of the ocellar neuropil. Six lateral ocelli occur on both sides of head in the butterfly larva. Each ocellus contains seven retinular cells, which are grouped into three distal cells and four proximal cells, or four distal cells, two peripheral cells and one central cell by the position of their rhabdomeres. Retinular axons extend to the brain, and enter the distal optic neuropil. There are six neuropils, each of which contains the seven axons from one ocellus and a dozen or so second order processes. Of seven retinular axons, four occur peripherally and the remaining three occur centrally in the neuropil. All axons synapse with fine branches of interneurons. Second order processes together with at least three central retinular axons extend to the second optic neuropil, but the peripheral axons could not be followed there. The highly organized receptors and the neuropil in the lateral ocellar system suggest a complexly integrated function. An ocellar nerve and proximal ocellar neuropil appear like an extension of the CNS, and direct connections of retinular axons with interneurons in the CNS appear characteristic of the dorsal ocellus. This difference may be related to the distribution of the two ocellar systems: the dorsal ocelli co-exist with the compound eyes of the adult, whereas the lateral ocelli are the only photoreceptor organs of the larval insect.
对蟑螂背单眼系统和燕尾蝶幼虫侧单眼系统中的单眼感受器和神经纤维网进行了比较。在蟑螂的背单眼中，超过10000个各具一个视杆的小网膜细胞在单眼囊中彼此堆叠，没有特定模式。小网膜轴突仅与囊下部四个粗大的二级神经元的分支形成突触。起源于脑的含暗颗粒神经元也与单眼神经纤维网中的二级神经元形成突触。单眼神经由四个粗大的二级突起（约6 - 16微米）和20 - 40个细突起（约1 - 5微米）组成，其中包括小网膜轴突、粗突起的侧支、可能的三级突起和未识别的突起。在单眼神经和单眼神经纤维网的最近端区域，突触与这些突起相对发生。蝴蝶幼虫头部两侧各有六个侧单眼。每个单眼包含七个小网膜细胞，根据视杆的位置，它们被分为三个远端细胞和四个近端细胞，或者四个远端细胞、两个周边细胞和一个中央细胞。小网膜轴突延伸至脑，并进入远端视神经纤维网。有六个神经纤维网，每个神经纤维网包含来自一个单眼的七个轴突和十几个二级突起。在神经纤维网中，七个小网膜轴突中有四个位于周边，其余三个位于中央。所有轴突都与中间神经元的细分支形成突触。二级突起与至少三个中央小网膜轴突一起延伸至第二视神经纤维网，但周边轴突在那里无法追踪到。侧单眼系统中高度有组织的感受器和神经纤维网表明其具有复杂的整合功能。单眼神经和近端单眼神经纤维网看起来像是中枢神经系统的延伸，小网膜轴突与中枢神经系统中的中间神经元的直接连接似乎是背单眼的特征。这种差异可能与两种单眼系统的分布有关：背单眼与成虫的复眼共存，而侧单眼是幼虫昆虫唯一的光感受器器官。
