Cristina Zenato

Cristina Zenato Instagram – 1. What makes a shark a shark?
These are few of the essential differences between sharks and regular fishes:
A Teeth, sharks can renew their teeth throughout their lives; if one breaks, the next one rotates from the inside of the jaw to replace it (No bony fishes are able ti replace their teeth when they break and fall out)
B. Sharks have gill slits visible on the outside of the body and they vary between five and seven slits (Fish only have one visible external slit per side)
C. Sharks bodies are covered in placoid scales known as dermal denticles, presenting the same structure as teeth. Each species has distinctive denticles, allowit scientists to recognize species by analyzing the skin. (Most, not all, of fishes are covered in scale, which are outgrows of the skin and overlap like tiles on a roof)
D. Sharks have large livers, rich in oil. The liver provides some buoyancy to the animals, and allows them to be lighter than counterpart fish of the same size, however sharks sink when they stop swimming, making them heavier than the surrounding water. (Fishes have an air bladder in their bodies that they control through blood flow to inflate and deflate, allowing them to hover motionless in midwater and making them weightless compared to the surrounding water)
E. Sharks skeletons are made of cartilage, a tough but flexible tissue and have no bone structure to protect their organs; think rib cage. (While the beginning stage of all fish structure is cartilage, it develops into bones as they leave the embryo stage)
F. It is very easy to detect the gender of sharks; male present two exteral organs called claspers and females present a genital slit called cloaca. (It is almost impossible to recognize the gender of fish, as they do not present visible organs and many species transition from female to male – or vice versa, through their life spans)
G. Reproduction happens through internal fertilization. Sharks give birth in different ways depending on the species; they can be oviparous, exaciparous or viviparous. (In fish fertilization is generally external, and most fish are oviparous)
NOTE: These are some of the main not all of the differences
📸 Tiger Shark | Posted on 11/May/2024 16:40:58