Catfish uses a complex coordination to suck its prey

Catfish have no arms or tongue to help them catch and swallow their prey. Instead, a catfish ready to hit moves its head.

Using powerful x-ray technology, scientists at Brown University tracked catfish as they caught and swallowed their prey to develop an accurate understanding of the complex set of movements required to create the suction. necessary for consumption. They found that many bones of the catfish skull work in a coordinated way to catch food. However, the bones move more independently when the fish swallow.

"Fish have the most mobile skulls of vertebrates," said Aaron Olsen, a postdoctoral research fellow in Brown's department of ecology and evolutionary biology. "The fish have more than a dozen moving parts in their skull, and they are all interconnected by joints and ligaments in these closed loops called" bonds "in engineering. Humans have a moving lower jaw and a middle ear, but that's all Fish heads also have very diverse shapes, so we can study how these complex systems evolved in many types of fish lines. "

The results were published on Wednesday, April 17 in the journal Acts of the Royal Society B.

To make the observations, Olsen and his colleagues used a 3D imaging technology called X-ray reconstruction of morphology in motion (XROMM), which was developed at Brown. The technology combines skeletal computed tomography with high-speed x-ray video, assisted by tiny implanted metal markers, to create visualizations of how bones and muscles move within humans and animals. The technique is so precise that scientists can track movements with errors equivalent to the width of a human hair.

"XROMM basically gives us an X-ray vision to see how multiple bones move within an animal when they adopt a behavior," Olsen said.

In this study, the team used XROMM to monitor three catfish catches and swallow prey including food pellets, squid pieces, and earthworms. First, the fish move their whisker-like barbs into the tank. Immediately after a barb touches a piece of food, four major bones surrounding the mouth and throat expand outward in a consistent and coordinated manner to form the suction needed to catch it.

On the other hand, these bones move more independently and less coherently as the fish swallow. Olsen does not know why swallowing is less coordinated.

"It seems like different tasks require different levels of coordination," said Olsen. "But what determines a good level of coordination for a specific task is an open question.What our study shows is that these natural behaviors have different levels of coordination.We do not know if they require strictly different levels of coordination. "

Previous research from Professor Brown's lab and senior researcher, Elizabeth Brainerd, used XROMM to study the feeding behavior of other fish, including bass and sharks. The largemouth bass exceeds their jaws, which helps them catch their prey. Catfish can not protrude from the jaw in this way, said Olsen. Instead, the bone essential for this bass action has evolved to the basis of whisker-like barbs in catfish, he added.

Bamboo sharks are distantly related to all bony fish, including catfish. However, bamboo sharks and catfish have mighty shoulders, or glandular belts, as both species move a lot while feeding, said Olsen.

The comparison of fish species with different body shapes, skull structures and eating behaviors can provide information on how fish of different body shapes have evolved in structures and mechanisms to solve similar tasks. said Olsen.

Members of the research team are currently using XROMM to track the characteristic behavior of the "vacuum-like" koi. Other members of the Brainerd laboratory are studying the feeding behaviors of other fish species.

Olsen is building a model to explain how the bones and ligaments that make up the skull of catfish move together as a complex system.