Which of the following has no Skeleton at all?

Q. Which of the following has no Skeleton at all?

1. Star fish
2. Sponge
3. Jelly fish
4. Silver fish

Answer: Jelly Fish

Jelly Fish does not have skeleton.

Most jellyfish do not have specialized digestive, osmoregulatory, central nervous, respiratory, or circulatory systems. The manubrium is a stalk-like structure hanging down from the center of the underside, often surrounded by oral arms, which connects with the mouth/anus at the base of the bell. This opens into the gastrovascular cavity, where digestion takes place and nutrients are absorbed. It is joined to the radial canals which extend to the margin of the bell, where tentacles are attached. Nematocysts, which deliver the sting, are located mostly on the tentacles; scyphozoans also have them around the mouth and stomach. Jellyfish do not need a respiratory system since their skin is thin enough that the body is oxygenated by diffusion. They have limited control over movement, but can use their hydrostatic skeleton to navigate through contraction-pulsations of the bell-like body; some species actively swim most of the time, while others are mostly passive. Depending on the species, the body contains between 95 and 98% water. Most of the umbrella mass is a gelatinous material — the jelly — called mesoglea which is surrounded by two layers of protective skin. The top layer is called the epidermis, and the inner layer is referred to as gastrodermis, which lines the gut.