Undoubtedly, during the developmental period, the caudal fin of all fishes passes through the protocercal stage. This type of fin is found in cyclostomes and the living dipnoans lungfishes. The heterocercal tail is sometimes called the shark-tail type of caudal fin. Elasmobranch cartilaginous fish and some primitive type of bony fishes contain this type of fin. This fin has two unequal lobes where the upper smaller lobe is known as epichordal lobe and a much larger lower lobe is known as hypochordal lobe.
In this case, the hind end of the vertebral column becomes bent upwards and continues almost up to the tip of the fin. Most of the higher teleosts have homocercal caudal fin. It has superficially symmetrical and two equal sized lobes such as upper epichordal and the lower hypochordal lobe. Internally, this tail is asymmetrical and the hinder end part of the vertebral column is greatly shortened and turned upward. In this case, the vertebral column does not touch the posterior limit of the fin..
The internal and external structure of caudal fin varies which depends on the swimming habits of the fish. Generally, these variations involve special modification of the vertebral column.
Following seven main types of caudal fins are found in fishes:. In some fishes, tapering and symmetrical types of fin is present which is known as isocercal or leptocercal caudal fin. In this case, the spine is long with a straight rod-like structure. Rat tails Macruidae , Blennies Blennidae Eels Anguilliformes , feather backs Notopteridae , and Gymnarchids Gymnarchidae , etc have the isocercal caudal fin.
This is a reduced type of caudal fin where some fin elements are fused together. They are found in cods Order: Gadiformes. In the modern lungfishes Dipnoi , the pseudocaudal caudal fins are found.
In this case, fins are developed from the backward growth of dorsal and ventral elements. This type of caudal fin bears much larger dorsal lobe than the ventral lobe which is greatly reduced. They are found in certain early Agnathans.
Unlike shoaling, in which fish merely swim loosely together, schooling requires coordinated body positions and synchronized movement. When fish, shrimp or other aquatic creatures swim together in a loose cluster, this is typically called a shoal. A school is a group of the same fish species swimming together in synchrony; turning, twisting and forming sweeping, glinting shapes in the water.
Schools are highly structured with coordinated movements and a common direction. A group of fish can switch from shoaling to schooling and back again.
Schools come together on their own, a phenomenon known as self-organizing. Different species prefer to school with their own kind.
If given the option, they greatly prefer their own species. Yes, different types of tetras can live together in a tank, only when there are enough species of each to form a different school. The same species of tetra tend to school together and only live well if there is sufficient member in a school. Most tetras are schooling fish, swimming together in groups. Generally, tetras will only school with their own species.
However, there are several situations where fish of different species will school together. However, a group of 10 is an ideal number, though. For the 10 Neon Tetras, a gallons aquarium is the best.
Furthermore, if you keep Neon Tetras, then increase the tank size to gallons of water. Neon tetras can live up to ten years, but they can die easily with the slightest change in the fish tank environment.
If there are any drastic changes in the water chemistry, the fish begin experiencing stress, depression and develop low immunity.
Neon tetras should be kept in schools of but 10 would be ideal. They are schooling fish that are very active typically swimming horizontally. Use plants and rocks and driftwood to provide entertainment and also provide security for these little guys. Use a good small filter to keep the tank healthy and clean.
Angels might eat tetras. If they grow up together they might be ok. According most experts, the ideal water pH for an angelfish is between 6. When there is a greater than 0. Signs of Spawning The most noticeable sign that spawning is about to occur between a pair of angelfish is the pairing-off behavior. Females who are ready to spawn will display a bulging belly and may become more aggressive towards tank mates.
In fact, its mostly likely the opposite — they are fighting! Often, battling fish will lock their mouths together and roll, each trying to injure the other.
But the sensory system of the wing-like, high AR fins was also more sensitive, meaning the fins were more responsive to a smaller magnitude of bending.
Aiello said he believes that a more sensitive nervous system evolved in the high AR fins because it needed to be more responsive to smaller movements as the fish use these stiff, less flexible fins to swim. The work is the product of collaboration across disciplines, a hallmark of the Organismal Biology and Anatomy program at UChicago.
The resulting PNAS study could have been three separate papers: the archival research of specimens from the Field Museum, the genetic phylogeny, and the neurobiological study of the living species. For experimentalists, like us, working with colleagues and natural history collections at the Field Museum has been particularly important as they bring key insights on evolution and biodiversity. Besides giving biologists a better understanding of how fish have optimized their swimming mechanics, the results of the study could also be useful to engineers developing underwater autonomous vehicles.
The propulsion systems of these devices need to be both efficient and responsive, and there are perhaps no better designs to copy than those perfected through evolution over millions of years. Materials provided by University of Chicago Medical Center.
Note: Content may be edited for style and length. Science News. Journal Reference : Brett R. Aiello, Mark W. Westneat, Melina E. Mechanosensation is evolutionarily tuned to locomotor mechanics. ScienceDaily, 10 April
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