|Guppy male and female|
The guppy (Poecilia reticulata), also known as the millionfish, is one of the most popular freshwater aquarium fish species in the world. It is a small member of the Poeciliidae family (females 4–6 centimetres (1.6–2.4 in) long, males 2.5–3.5 centimetres (1.0–1.4 in) long) and like all other members of the family, is live-bearing. Guppies are popular aquarium kept fish because of their inexpensive needs and beautiful color ranges.
A guppy’s digestive system is a lot like a human’s digestive system. Guppies have a tongue, teeth, a pharynx, gill slits, an esophagus, a stomach, intestines, and an anal opening. Digestion begins in the mouth. First, the food is mashed up into small pieces by the teeth. Then, the food travels down the pharynx. On either side of the pharynx, there are gill slits. Gill slits allow water to pass into the chambers, which helps break down the food even more. The food must pass through the esophagus in order to enter the stomach. Inside the stomach, the intestines move food so it can be digested quickly. The remains of the food are then sent out through the anal opening.
Guppies, like all fish, have gills, which oversee the gas exchange. The heart of a guppy is very different from that of a mammal, for instance there are two compartments instead of four. They are called the auricle and ventricle. When the fish breaths the ventricle contracts and blood is forced out to the gills which act as lungs. This is where the gas exchange happens. The blood receives oxygen and releases carbon dioxide. The blood that now carries oxygen goes through the dorsal artery, which divides into smaller and smaller vessels and go all over the body to then distribute the oxygen and gets carbon dioxide and waste. Then, the blood is carried to the heart by veins and lymph vessels. Then the cycle repeats over and over.
A guppy's nervous system is highly centralized around its spinal cord and brain. The cerebellum controls the body's movements, and the olfactory bulbs and cerebrum control's it's sense of smell.