A type of syngamy in which both fusing gametes are flagellated but different in size are known as:

Explanation

Anisogamy is a form of sexual reproduction in which gametes (reproductive cells) differ in size or shape between the male and female individuals. Typically, anisogamy involves the fusion of a small, motile male gamete (sperm) with a larger, non-motile female gamete (egg or ovum). This reproductive strategy is common in many organisms, including animals, plants, algae, and fungi. Anisogamy contrasts with isogamy, where the gametes are similar in size and shape, and with oogamy, where there is a significant difference in size between the gametes (such as the large, non-motile egg and small, motile sperm).