The Classification of the Goldfish

Goldfish, known also as the Carassius aura us, still can be found in streams and ponds throughout Asia. In the wild their colors are somewhat muddier. The goldfish comes from the Cyprinidae family, a classification of Carp. They are descended from the Crucian Carp, also known as Carassius carassius, and are related to the common carp, which is known as Cyprinus carpio.

The best way to distinguish between a carp and a goldfish is to look at the dorsal fin. The goldfish's dorsal is usually straight up or is concave (curved in) while the carp's dorsal is generally convex (curved out).

The Body and Its Structure

There are over 300 different varieties of goldfish. Some of them are unique, and fall outside the general physiognomy of fish altogether. We will use the Comet goldfish as the classic example of a goldfish when we discuss them in general terms. Comets are the common American variety.

The Comet's body is streamlined, being more or less flat on the sides. The view from the top shows the middle as somewhat thicker than the head or tail section. The view from the side shows the middle as somewhat deeper, whereas the body tapers toward the head and the section where the body meets the tail. This narrow section is also known as the caudal peduncle.

Regardless of variety, especially among the fancies, the caudal peduncle is almost always narrow, no matter how large the body. Some Fantails, especially the Redcap and the Marigold Chinese Lion head, have exceptionally large heads, while Fantail, Moor and Veil tail, which are quite round, vary in their head shapes and sizes.

Fins

Fins have three main functions: stabilization, braking and propulsion. They come in two types, paired and median, and they are located at five places on the fish's body.

The pectoral fins are the forward most fins, and are an excellent example of paired fins. They are almost always moving, because they help the fish to turn, hover, navigate tight corners or propel backward. While they can help in forward propulsion, it is not their main function. The pectorals are usually found somewhere underneath or just behind and below the gills, on each side, toward the bottom of the body. They are not always shaped the same on different varieties. They can be short and small as on a Lion head, or long and flowing as on a Veil tail.

The dorsal fin is an excellent example of the median fin. It rises directly from the top of the middle of the fish's back. It is made up of rigid and soft spines webbed with membrane. When a goldfish is healthy, this fin stands straight up, and its main function is to help stabilize the fish. It keeps the fish from rolling over by keeping the bottom of the fish down. Whether hovering or during forward propulsion, it keeps the fish moving straight. Some varieties, like the Celestial, have no dorsal fin, and consequently have more difficulty swimming.

The pelvic or ventral fins are a pair of fins at the abdomen, toward the bottom of the fish, generally in front of the anal canal. More than anything they act as brakes, but they also stabilize and help in turning. While ventral or pelvic fins may be elongated, as on a Veil tail Ryun kin, they rarely grow so large that they impair or grow beyond use, as opposed to the dorsal and caudal fins.

The anal fin protrudes from the bottom of the body in front of the anal and sexual openings. It is a median fin, and its main job is to function as a stabilizer. On some varieties, these fins can aid in propulsion and turning in small spaces. Sometimes, in the fancy varieties, the anal fin becomes a set of paired fins. Interestingly, they grow from the spot where there would have been a median fin, and are the only sets of paired fins that are actually joined together where they meet the body. Sometimes the fins themselves are actually joined along the backside of the fin for a short distance, but never for the length of it.
The caudal or tail fin is actually a median fin. The caudal or tail fin is extremely important in propulsion, and is usually the source for most of the power during swimming. It can also act as a brake, but is much more helpull in turning. While fancy varieties might have a fan tail or some other elongated tail, like the anal fin, it is really a median fin. The fins can sometimes be forked, as in the Black Moor, or can be wide and fan-shaped, as in the Veil tail. In the fancier varieties, these fins are so exaggerated that they are not as helpful, if at all, and consequently, these fish are bad swimmers.

There are three different types of caudal fins: the single tail fin, the veil tail and the fantail. There are varieties of each of these, but these are the three main types. The single tail fin is obvious, and can be found on the common goldfish. .The fantail is the most common of the fancy varieties. This is a pair of forked tails joined at the caudal peduncle. The veil tail is a beautiful, large tail, which has no indentations (or forks) and is square finished. It is usually very long and elegant.