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Compared to similarly sized fish, mammals and birds typically have brain sizes fifteen times larger, though some species of fish such as elephantnose fish have very large brain-to-body ratios. However, fish still display intelligence that cannot be explained through Pavlovian and operant conditioning, such as reversal learning, novel obstacle ...
Jaws allow fish to eat a wide variety of food, including plants and other organisms. Fish ingest food through the mouth and break it down in the esophagus. In the stomach, food is further digested and, in many fish, processed in finger-shaped pouches called pyloric caeca, which secrete digestive enzymes and absorb nutrients.
Fingerling – refers to a fish that has reached the stage where the fins can be extended and protective scales have covered the body. [4] At this stage, the fish is typically about the size of a human finger, [5] hence the name. Once reaching this stage, the fish can be considered a juvenile, and is usually active enough to move around a large ...
The behavior of an amphibian hatchling, commonly referred to as a tadpole, is controlled by a few thousand neurons. [4] 99% of a Xenopus hatchling's first day after hatching is spent hanging from a thread of mucus secreted from near its mouth will eventually form; if it becomes detached from this thread, it will swim back and become reattached, usually within ten seconds. [4]
The head or skull includes the skull roof (a set of bones covering the brain, eyes and nostrils), the snout (from the eye to the forward-most point of the upper jaw), the operculum or gill cover (absent in sharks and jawless fish), and the cheek, which extends from the eye to the preopercle. The operculum and preopercle may or may not have spines.
Fish embryos go through a process called mid-blastula transition which is observed around the tenth cell division in some fish species. Once zygotic gene transcription starts, slow cell division begins and cell movements are observable. [4] During this time three cell populations become distinguished. The first population is the yolk syncytial ...
Researchers also found that an extra daily serving of processed red meat on average was associated with a 1.6-year acceleration in brain aging, according to the study.
Coelacanth eggs are large, with only a thin layer of membrane to protect them. Embryos hatch within the female and eventually are born alive, which is a rarity in fish. This was only discovered when the American Museum of Natural History dissected its first coelacanth specimen in 1975 and found it pregnant with five embryos. [69]