Larva Found in Phylum Echinodermata! 1. Dipleurula Larva: 1. The dipleurula form (Fig. 21.39A) is reached during development and is characterised by its bilaterally symmetrical, egg-shaped body. 2. The ventral concave side bears the mouth and is encircled by a circumoral ciliated band. 3. The anus is disposed ventrally. 4. The digestive canal is differentiated into oesophagus, stomach and intestine. [...]
In this article we will discuss about the development characteristics of protostomes and deuterostomes. Protostomes: Developmental Characteristics: 1. Pattern of embryonic cleavage: Spiral cleavage pattern; the spiral cleavage is masked at the 6th cleavages (64-cell stage), e.g., Sipuncula, Echiura, Annelida, Pogonophora, Mollusca and some groups of Arthropoda (e.g., Myriapoda, Crustacea and Insecta except Chelicerata). 2. Fate of embryonic blastomeres: Determinate [...]
In this article we will discuss about Sagitta:- 1. Habit and Habitat of Sagitta 2. External Structures of Sagitta 3. Body Wall 4. Coelom 5. Digestive System 6. Circulatory, Respiratory and Excretory Systems 7. Nervous System 8. Reproductive System 9. Development. Habit and Habitat of Sagitta: Sagitta is a marine planktonic animal which lives throughout the world. It can swim [...]