Micronucleus and macronucleus are the characteristic features of

The correct option is Vorticella and Paramecium.

Nuclear dimorphism, which is the presence of two distinct types of nuclei within a single cell, is a key characteristic feature of ciliates (phylum Ciliophora). These two types of nuclei are:
1. Macronucleus: This is a larger, typically polyploid nucleus that controls the vegetative and metabolic activities of the cell, such as growth and protein synthesis.
2. Micronucleus: This is a smaller, diploid nucleus that is responsible for reproductive and genetic functions, participating in genetic recombination during processes like conjugation.

Let's analyze the organisms mentioned in the options:
- Paramecium: A well-known genus of unicellular ciliates that exhibits distinct nuclear dimorphism with one large macronucleus and one or more small micronuclei.
- Vorticella: Another genus of bell-shaped, stalked ciliates that also possesses a large, horse-shoe-shaped macronucleus and a tiny micronucleus.
- Hydra: A multicellular animal (Cnidarian), not a unicellular ciliate, and does not have micronuclei or macronuclei.
- Opalina: A genus of multinucleate protists (Opalinids) that contains many monomorphic nuclei (all nuclei are of the same type), lacking nuclear dimorphism.

Therefore, because both Vorticella and Paramecium are ciliates characterized by nuclear dimorphism, they possess both a micronucleus and a macronucleus.