Black-ray goby mother bird regurgitating food to her chicks. This way, the shrimp and the goby are kept well fed. Sometimes, if the shrimp is not kept well fed, it will resort to killing the goby. In the wild, most burrows are shared by male and female goby pairs, with their respective shrimp partners, and the female goby will use this burrow as a nesting site to lay her eggs. The obvious benefits to both organisms of this symbiotic relationship make the interaction a form of mutualism. Here is an interesting example of this. The other fish is a dartfish (genus "Ptereleotris").
Round goby Nord-Ostsee (Kiel) Canal. As of 2010, the westernmost site of round goby occurrence in Europe was the Lower River Scheldt, the tidal zone in the river mouth, and Albert Canal, Belgium. In 2011, the round goby began invading the fresh waters of France: the species appeared in the Rhine River (on the border between France and Germany), and in the French part of the Moselle River. In total, 52 parasite species are registered in the round goby in the native area. Most abundant parasites of the Black-Sea round goby are metacercariae of trematodes of Heterophyidae family, such as "Cryptocotyle concavum",