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| Figure1. Anatomy of Pleco |
Dorsal Fin
The dorsal fin is located at the top of the Pleco fish. This fin supports the balancing of the fish and also allowed the fish to swim in a straight path. Dorsal fin also plays an important role in stabilizing the fish against rolling in the water. A unique feature of the Pleco fish is that it has a huge dorsal fin compared to other aquarium fish. The dorsal fin of juvenile Pleco is usually folded (closed) when they are stationary. When the juvenile Plecos are resting on the wall of the aquarium or any surfaces, their dorsal fin is always closed to minimize turbulence from water currents. As they reach adulthood, the dorsal fin can be seen to remain open at all times. This could possibly because the larger body mass of the adult Pleco can help to maintain balance even when the dorsal fin remains open.
Pectoral Fin
The pectoral fins are located just below the Pleco grills as do most fishes. Main functions of these fins are to facilitate the swimming capabilities of the fish. These fins also allowed the Pleco to hover or glide in water. Generally, the pectoral fins are always moving in most fishes to keep them stable in the water. But it has been a week that we observed our Plecos, their pectoral fins remained immobile most of the time if they are not swimming around the aquarium. This is because they spent a majority of the time attaching to surfaces, so their pectoral fins remained still to induce minimal movement.
Pelvic Fin
The pelvic fins are situated at the bottom of the Pleco fish just in front of the anal fin. Like most other fished, Pleco fish used these fins to change the direction of their motion in water while also stabilizing themselves. Besides that, the Pleco uses the pelvic fins for breeding purpose. For Plecos fishes, the male species will be the one caring for their offspring. He will guard the eggs, occasionally turns them over with his mouth and wait for it........ he will supply oxygen to the eggs by fanning them with his pelvic fins. The video below captured the precious moment where the male Pleco is fanning the eggs. It is soooo adorable!!!
Caudal (Tail) Fin
The caudal (tail) fin as it name suggest is located at the back of the Pleco fish. This is one of the most important fin of any fished as it is the main fin which allows them to propel forward. This is the only fin of the Pleco (other fishes as well) that is connected with the spine of the fish. In some species of fish, the caudal fin can easily distinguish the sex of the fish, a good example is Guppies. Just like the dorsal fin of juvenile Plecos, the caudal fin is usually closed and open only if the Plecos are in motions. Similarly, the caudal fin remained open at all times they reached adulthood
Anal Fin
The anal fin is exactly what the name state, where the fin is located near the anal cavity which is between the pelvic fins and caudal fin. Anal fin also aids the Pleco in swimming on a straight path. For some fishes, the anal fin plays an important role for spawning.
Eye
The eye of the Pleco is unique compared to most of the species of aquarium fishes. The Pleco has an eye structure called the “iris operculum” which enables them to monitor the amount of light entering their eye during the day. Plus it also helps them to disguise their eye-spot. The iris of the Pleco was also referred to as the “omega iris” because as the operculum is closed the pupil of the Pleco actually resembles the Greek letter Omega.
References
http://www.monsterfishkeepers.com/forums/threads/pleco-anatomy.29321/http://hubpages.com/animals/all-about-algae-eaters
http://www.tropical-fish-success.com/fish-anatomy.html
https://www.youtube.com/watch?v=0ASUfZnIoBk
