“Small fish may have small brains but they still have some surprising cognitive abilities”, says Dr Jeremy Kendal* from Durham University’s Anthropology Department.

Dr Kendal is the lead author of a new study showing that Nine-spined stickleback fish (Pungitius pungitius) can compare the behaviour of other sticklebacks with their own experience and make choices that lead to better food supplies.

“‘Hill-climbing’ strategies are widely seen in human society whereby advances in technology are down to people choosing the best technique through social learning and improving on it, resulting in cumulative culture”, says Dr Kendal. “But our results suggest brain size isn’t everything when it comes to the capacity for social learning.”

Around 270 Nine-spined sticklebacks were caught from Melton Brook in Leicester using dip nets. After being divided into three experimental groups and one control group, the fish were housed in different aquariums and the fish in the experimental groups were subjected to two different learning experiences and two preference tests in a tank with a feeder placed at each end.

1.) The fish were free to investigate both feeders during a number of training trials. One feeder (dubbed “rich feeder”) always handed out more worms than the other one (dubbed “poor feeder”). The fish were then tested to see which feeder they preferred.
2.) In the second training trail, those fish that come to prefer the rich feeder could see other fish feeding. During this stage, the rich and poor feeders were swapped around and the rich feeder either gave even more worms than before or roughly the same or less. During the second test, the fish were once again free to explore the tank and both feeders. Around 75 per cent of the Nine-spined sticklebacks had learned from watching the other fish that the rich feeder, previously experienced first hand themselves as the poor feeder, gave them more worms. In comparison, significantly fewer sticklebacks favoured the feeder that appeared to be rich from watching other sticklebacks if they themselves had experience that the alternative feeder would hand out roughly the same or more worms.

Further testing showed that the sticklebacks were more likely to copy the behaviour of fast feeding fish.

“Lots of animals observe more experienced peers and that way gain foraging skills, develop
food preferences, and learn how to evade predators”, Dr Kendal explained. “But it is not always a recipe for success to simply copy someone. Animals are often better off being selective about when and who they copy. These fish are obviously not at all closely related to humans, yet they have this human ability to only copy when the pay off is better than their own.”

The study, which has been published in the journal Behavioral Ecology, was carried out by scientists from St Andrews and Durham universities and funded by the Biotechnology and Biological Sciences Research Council. The lead author of the study, Dr Kendal, is a Research Council UK Fellow.

Researchers at Woods Hole Oceanographic Institution (WHOI) unveiled a hazardous cocktail of pesticides when analysing the brain matter of 12 marine mammals; eleven cetaceans and one gray seal stranded near Cape Cod, Massachusetts.

This is the most extensive study of pollutants in marine mammals’ brains and it confirms suspicions of marine mammals being the carrier of a vast array of different chemicals that have found their way into marine ecosystems.

Lead author Eric Montie analyzed the cerebrospinal fluid and the gray matter of the cerebellum in the twelve animals and found them to contain a long row of different man-made chemicals, including a group of especially widespread substances labelled “the dirty dozen” by environmentalists. Many countries banned the “the dirty dozen” as early as the 1970s due to their adverse effect on human health, but they are unfortunately still present in our environment.

Montie didn’t just test for the presence of certain chemicals; he also measured their concentration and found one instance where it was surprisingly high.

“The biggest wakeup was that we found parts per million concentrations of hydroxylated PCBs in the cerebrospinal fluid of a gray seal”, says Montie. “That is so worrisome for me. You rarely find parts per million levels of anything in the brain.”

PCBs are neurotoxicants known to disrupt the thyroid hormone system. Other examples chemicals found in the tested mammals are DDT (diklorodifenyltriklorethane), which can cause cancer and disturb reproduction, and PBDEs (polybrominated diphenyl ethers); a type of flame retardants known to impair the development of motor activity and cognition.

Co-author Chris Reddy, a senior scientist in the WHOI Marine Chemistry and Geochemistry Department, describes the new study as “groundbreaking because Eric measures a variety of different chemicals in animal tissues that had not been previously explored. It gives us greater insight into how these chemicals may behave in marine mammals.”

The results of this study was published online April 17 in Environmental Pollution.

A Taiwan research team has successfully extracted a brain-boosting nutrient from squid skin, according to an announcement made by the Council of Agriculture’s Fisheries Research Institute.

The nutrient in question is phospholipid docosahexaenoic acid, commonly known as PL-DHA, a substance known to improve a persons memory and enhance learning ability.

According to the institute official, PL-DHA is superior to TG-DHA another form of docosahexaenoic acid commonly found in deep-sea fish oil — when it comes to inhibiting degradation of the intellect since PL-DHA can cross the blood brain barrier and be absorbed directly by the brain.

Researchers at the institute have also showed that PL-DHA is effective in reviving neural cells and enhancing the content of three oxidation-resistant enzymes — GSH, CAT and SOD. In addition to this, the fatty acid will moderate the oxidative damage to neural cells that can be induced by free radicals in the body, which means that it will decrease the pace of plaque and tangle accumulation in brain cells.

Quoting medical reports, the institute official stressed that Alzheimer’s and other forms of senile dementia is known to be associated with the accumulation of plaque and tangles in the brain.

In a new study on Tanganyika cichlids, three scientists[1] [2] [3] from Uppsala University in Sweden have shown that intricate rearing behaviour varies with brain size in females. The only previously published study showing similar patterns concerned predatory animals.

Tropheus moori – one of the species used in the study. – Picture www.jjphoto.dk

How the vertebrate brain has developed throughout the course of evolution is still not clear, and we are still not certain if brain functions in a specific species develop to match a demanding environment. One way of learning more about this is to compare brain size and structure in closely related species living under dissimilar circumstances.

“It is important to look at differences between males and females since females often distinguish themselves from males, both in behaviour and appearance”, says Niclas Kolm, lead-author of the study.

The study looked for correlations between brain size and ecological factors in a large number of specimens from 39 different species of Tanganyika cichlid. Lake Tanganyika is especially suitable for this type of study since it is inhabited by cichlid groups exhibiting significant dissimilarities in both brain structure and ecology, and whose ancestry is well known. Tanganyika cichlids varies dramatically from species to species when it comes to factors such as body size, diet, habitat, parental care, partner selection, dissimilarities between the sexes, mating behaviour, and brain structure.

The result of the study showed a correlation between brain size and the two factors diet and parental care behaviour. Species where only the female fish cares for egg and fry turned out to have bigger brains than species where both parents engage in parental care. The brain was however only larger in females; there was no difference in brain size between males of the two groups.

The largest brains of all were found in algae-eating cichlids. These fishes live in environments characterized by a high level of social interaction. “This indicates that social environment have played a role in brain development”, says Kolm.

The study was published in the web version of “Proceedings of the Royal Society of London Series B” on September 17. You can find it here (http://journals.royalsociety.org/content/j114062824820l76/).