Some species move in a looping, leech-like fashion. The animal is capable of reversing its ciliary beat in order to withdraw from an unpleasant stimulus. Micro-organisms including bacteria and invertebrates form most of the Gastrotrich diet, and they are sucked into the mouth by the powerful pumping pharynx. Reproduction and development Gastrotrichs are hermaphrodite organisms. Spermatophores are picked up from the male pore by the male copulatory organ, which transfers the sperm package to the female pore of the partner, who returns the action.
Fertilisation takes place internally, and large eggs are produced.
Dormant eggs can remain viable and survive for long periods in environmental conditions that are unsuitable for development. These eggs grow by a process of complete cleavage. The gastrotrichs are thought to share characteristics with a number of other phyla. The presence of external cilia, a two-pronged foot and flame cells are characteristic Rotiferan features, whilst the pattern of the gut closely resembles that of the Nematoda. They are characterised by the presence of adhesive tubules on the posterior, anterior and ventral surfaces.