Monikammioiset
Monikammioiset refers to a group of organisms characterized by having multiple chambers within a specific structure, typically their heart. In vertebrates, this is most commonly applied to the hearts of fish. Unlike the single-chambered hearts of many invertebrates or the more complex multi-chambered hearts of amphibians, reptiles, and mammals, fish hearts are generally considered to possess two primary chambers: an atrium and a ventricle. However, the term monikammioiset can also encompass the presence of accessory chambers, such as the sinus venosus and the bulbus arteriosus (or conus arteriosus in some species), which contribute to the overall circulatory system and its function. These additional structures play roles in collecting blood before it enters the atrium and in regulating blood flow into the gills, respectively. The specific arrangement and complexity of these chambers can vary among different fish species, reflecting adaptations to diverse aquatic environments and lifestyles. This distinct cardiac structure is a defining feature of the piscine circulatory system, enabling efficient oxygenation of blood within their aquatic habitats.