No the box jellyfish is probably the only animal without brains. It possesses a network of nerves—a net that helps the jelly to be sensitive to the changes in the external environment. As it turns out, the box jellyfish doesn’t have the central nervous system. However it does possess have a nervous system (decentralized network). The box jellyfish nervous system is divided into three functional parts namely; rhopalia, conducting nerve ring, and motor nerve net.
Do Box Jellyfish have Brains?
Scientists are trying to figure out why and how jellyfish behaves the way it does about certain things. For instance an animal that lacks central nervous system is able to communicate with the external environment, detect movement of potential predators, capture prey, or in fact avoid objects underwater. The box jellyfish does all of it. Scientists wonder how? Part of the answer lies in its operations of tissues and cells.
Box jellyfish are diploblastic animals which means they possess two layers of embryonic germ namely ectoderm and endoderm. Other diploblastic animals include sea anemones, corals, and comb jellies. The two layers of embryonic germ or cells do not act independently. They operate in coordination with each other. Cnidarian is the first group of animals that distinguishes it from the primitive animals called sponges.
There is a jelly-like substance called mesoglea which lies in between the ectoderm and endoderm. Much of the box jellyfish structure is made up of mesoglea. This is why the umbrella-like bell of the box jellyfish appears to be jelly. The nervous system of the box jellyfish is located within the mesoglea.
Network of Cells
The sensory neurons of the jellies run through the network of nerves and spread all across the organism’s body. The tissues or cells cross each other thereby creating a complex neuron network.
The network of cells provides superhighway for signals to travel from one cell to the other but they never get to the centralized area. However, signals do not travel as fast as they do in triploblastic animals (from flatworms to humans). But still jellies do not require these signals to travel faster because they lack cephalization, a region where sense organs such as head and brain are concentrated.
Alongside network of cell, the box jellyfish seem to possess a nerve ring which connects pedalia (tentacle bases) with rhopalia (sensory clubs). Researchers conclude that the nerve ring facilitates in communication between the swim pacemakers.
All the cubozoans have a specialized ring of tissue that stretches inside the bottom wall of the bell. During swimming the box jellyfish contracts its bell and velarium narrows the bottom opening which ultimately creates a thrust. This helps the jellies to swim fast and with great efficiency.