টপিক সীমারেখা
My Research
Research in my lab now focuses on the giant Pacific octopus in three main areas: behavior, learning, and fisheries.
To learn more about cephalopods, please contact me!
Overview
Cephalopods are beautiful animals that display complex and fascinating behavior. They have existed for about 500 million years and have fascinated humans for thousands of years. One of the first to study them was Aristotle, who described how octopuses change color. Today, cephalopods are targeted in large fisheries around the world. They are also studied for both basic and applied research.
What is a Cephalopod?
Cephalopods belong to the phylum Mollusca. They originated during the Cambrian period (541-485 million years ago (mya)). The early cephalopods were very small, with slightly curved shells, and occurred only in shallow seas, but they expanded their distribution during the Great Ordovician Biodiversity Event (485-443 mya). Today, there are about 790 species in two sub-classes: Coleoidea and Nautiloidea. The Coleoidea comprise two superorders: Octopodiformes and Decapodiformes.
Skin
A remarkable feature of cephalopods is their complex and beautiful skin. Many species can rapidly change their appearance quickly. This feature is called Rapid Adaptive Coloration. It is used for camouflage and communication.
The most important elements in the skin are chromatophores. They are tiny sacs of pigment surrounded by muscles that are under nervous control, so they can rapidly expand and contract. The color of the pigment may be red, brown or yellow, depending on development and species.
In many species, the chomatophores overlie reflective tissue called iridophores, which reflect light. Some species also have permanent white patches just below the iridophores called leucophores.
Recent experiments have shown that cephalopods control their body pattern visually. For camouflage, they view their surroundings and quickly process the visual information. Then, the central brain sends neural signals throughout the skin to chromatophores and iridophores to produce the appropriate body pattern. This entire process can take less than 200 milliseconds – faster than a blink of the eye!
In addition to the colorful body patterns, octopuses and cuttlefishes can morph their skin into three-dimensional shapes to enhance camouflage called papillae. No other animal on the planet can do this.
Intelligence
Octopuses are fast learners. They have large brains with 34 lobes and millions of neurons. Yet only one-third of its total number of neurons occur in the brain. Two-thirds occur in arms, skin and other organs! There is strong evidence in octopuses and cuttlefishes for both short-term (one hour) and long-term (several months) memory.
But even though they seem smart, it is difficult to assess intelligence. For example, there is little evidence (so far) that they play or can use tools. And most cephalopods are not social. Are they really intelligent? More experimentation is needed!
Fisheries
Cephalopods are an excellent protein source and a popular food around the world, especially in Asia. During 1999-2015, the world catch of cephalopods increased from 3.4 to 4.7 million tons. Most of the catch is composed of squids (3.5 million tons in 2015).
- Food and Agriculture Organization of the United Nations, 2016 ফাইল 5.4এমবি PDF document Uploaded 13/05/20, 11:37
The largest squid fishery is Japan is for Japanese flying squid (Todarodes pacificus). In 2015, octopus landings were 400,000 tons. The most important species in Hokkaido is the giant Pacific octopus (Enteroctopus dofleini).
