The development of the compound eyes ofPenaeus duorarum (Crustacea: Decapoda) with remarks on the nervous system

Summary The development of the compound eyes and nervous system of the penaeid shrimp,Penaeus duorarum, from the first nauplius to the first postlarva, has been studied. The first anlage of the compound eyes is a pair of optic discs on the front of the animal. These increase in size through cell-division until the second protozoea stage, where the eye-stalks appear with ommatidia and optic neuropiles developed. The original neuroectoderm of the optic discs is retained in the shape of a proliferation zone throughout the life of the animal. From the optic discs, develop the ommatidia, the lamina ganglionaris, and the medulla externa. The medullae interna and terminalis develop from cells coming from the brain anlage. From the second protozoea and onwards, the development is less rapid. The final shape of the adult eye is reached during the postlarval stages and includes the appearance of a few more pigments and a perfecting of several features. A scheme for the development of crustacean compound eyes is laid down. Further, the medulla externa of the Malacostraca and the single medulla of non-malacostracan crustaceans are homologized.The continuous growth of the nervous system is traced in the development of the neuropile. The appearance of glomeruli structures is reported, as are also, to some extent, neurosecretory organs. The development of the SPX-organ conforms to that of other decapods.For the sake of simplicity, the findings reported below in Results are grouped under two headings, namely the eye-stalk and the nervous system. Under the eye-stalk will be described both the structures coming from the optic discs comprising the ommatidia, the lamina ganglionaris, and the medulla externa, and the contributions from the nervous system comprising the medulla terminalis and medulla interna. Under the nervous system will be described the rest of the nervous system. The term anlage of the compound eyes is the same as the optic discs and denotes all contributions from this area in the early larva.