Do flaggellates living in Symbiosis always harm the animal which they live?

No, flagellates living in symbiosis do not always harm the animal they live in. In fact, many flagellates engage in mutualistic symbiosis, where both organisms benefit from the relationship. For example, some flagellates provide essential nutrients to their animal hosts, while the animal, in turn, provides a protected environment and access to resources for the flagellate. Some examples of mutualistic symbiosis involving flagellates include:

1. Digestive Symbiosis: Certain flagellates reside in the digestive systems of animals like termites and wood-eating cockroaches, helping break down and utilize cellulose, a complex sugar that many animals cannot digest on their own. These flagellates aid their hosts in extracting nutrients from plant material, allowing them to thrive on a diet primarily consisting of wood or other cellulose-rich substances.

2. Nutrient Exchange: Some flagellates, such as those found in the guts of certain marine invertebrates, engage in nutrient exchange symbiosis. They provide essential nutrients like vitamins and amino acids to their hosts, which the animals would have difficulty obtaining from their environment alone. In return, the flagellates receive protection and access to the nutrients present in the host's digestive system.

3. Bio-luminescent Symbiosis: Some marine animals, such as certain jellyfish and deep-sea fish, have bio-luminescent flagellates living in their tissues. These flagellates produce light through biochemical reactions, and the animals utilize this light for various purposes, including attracting prey, deterring predators, or communicating with other members of their species.

4. Reproduction Assistance: Certain flagellates assist their hosts in reproduction. For example, certain species of ants and termites have symbiotic flagellates that help them produce more reproductives (queens and kings). These flagellates manipulate the host's developmental pathways, ensuring the survival and proliferation of the host colony.

It's worth noting that not all interactions involving flagellates and animals are beneficial. Some flagellates can indeed cause harm as parasites, leading to diseases and detrimental effects on their hosts. However, many flagellates also engage in vital mutualistic relationships that contribute to the overall health, survival, and ecological success of both the flagellate and the animal they live with.