Urochordata includes about 2000 fixed and 100 pelagic species. It has been divided into the following three classes: Class 1. Larvacea (Appendicularia): 1. Small (5 mm long solitary) free-swimming pelagic forms. 2. Neotenic forms which retain the larval form throughout adult life with persistent tail, nerve cord, notochord. 3. Test is temporary and renewed periodically. 4. Single pair of gill-slits [...]
The following points highlight the nine main types of urochordata. The types are: 1. Molgula 2. Botryllus 3. Ascidia 4. Ciona 5. Clavelina 6. Pyrosoma 7. Doliolum 8. Salpa 9. Oikopleura. Type # 1. Molgula: Molgula (Fig. 5.1) is a round, solitary and sessile ascidian, about 2.5 cm long. It is found abundantly in the shallow water of Atlantic and [...]
In this article we will discuss about the affinities of urochordata. Affinities # Urochordata with Non-Chordates: Similarities: 1. Food collection similar to spongec, mussels and lophophores. 2. Typhlosole in the intestine. 3. Presence of larval eye and oocytes. 4. Budding leading to a chain of new zooids. 5. Formation of colony. Dissimilarities: 1. Fish-like tadpole larva. 2. Absence of [...]