Radial symmetry and lack of chidoblasts are the characteristics of

Options

A. Hydra
B. Starfish
C. Ctenoplane
D. Aurelia

Answer

To determine the characteristics of organisms with radial symmetry and a lack of nidoblasts, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Radial Symmetry**:
- Radial symmetry refers to a body plan in which the organism can be divided into similar halves by multiple planes passing through the central axis. This means that if you cut the organism in any direction, the resulting halves will be mirror images.

2. **Define Nidoblasts**:
- Nidoblasts, also known as cnidocytes, are specialized cells found in organisms of the phylum Cnidaria. They are used for defense and capturing prey, and they contain stinging structures called nematocysts that can inject toxins into prey.

3. **Identify Organisms with Radial Symmetry**:
- Organisms that exhibit radial symmetry include jellyfish, sea anemones, and other members of the phylum Cnidaria as well as members of the phylum Ctenophora (comb jellies).

4. **Identify Organisms Without Nidoblasts**:
- Since nidoblasts are characteristic of Cnidaria, any organism that does not belong to this phylum will lack nidoblasts. For example, organisms in the phylum Echinodermata (like starfish) and Ctenophora do not have nidoblasts.

5. **Analyze the Options**:
- If we consider the options:
- **Hydra**: Belongs to Cnidaria, has nidoblasts.
- **Starfish**: Belongs to Echinodermata, has radial symmetry but lacks nidoblasts.
- **Ctenophora**: Exhibits radial symmetry and lacks nidoblasts.
- **Aurelia**: Belongs to Cnidaria, has nidoblasts.

6. **Conclusion**:
- The organisms that exhibit radial symmetry and lack nidoblasts are from the phylum Ctenophora. Therefore, the correct answer to the question is Ctenophora.

### Final Answer:
Ctenophora