Monthly Archives: June 2016

Oceans may become too acidic for animals to smell their way around

Christina C. Roggatz, University of Hull

The oceans are becoming ever more acidic as humans pump increasing amounts of carbon dioxide into the atmosphere. These acidic oceans will change smell molecules and render them unrecognisable for animals in the sea.

Chemical communication using smell is essential for marine organisms. Its importance is comparable to the combined status of vision and hearing in humans. My latest research reveals that smell molecules in the ocean are significantly affected by ongoing ocean acidification.

Smell molecules are chemicals that are produced by organisms either on purpose – by females to attract males, for instance – or by chance during natural processes such as protein degradation. In both cases, they can be used by animals to smell their way around.

Imagine you are a little crab living on a shore covered with large rocks and deep pools, and battered by tides and waves. The only way to find your lunchtime snack would be to smell it from a distance. But the same also applies to the octopus hunting you. So you, the crab, also rely on smelling the octopus first to avoid being eaten. What if all this were no longer possible?

Man-made, increasing carbon dioxide emissions have caused the pH in our world’s oceans to decrease, an effect called ocean acidification. By the year 2100, the sea surface pH is predicted to drop by up to 0.4 units. This may not seem much, but it has been shown to significantly affect the fitness, physiology, reproduction and behaviour of everything in the sea from huge sharks and whales to the tiniest of plankton.

Many molecules transporting smell from its source to an organism are potentially sensitive to pH. This holds particularly true for peptides and proteins, which are used, for example, by crabs, barnacles and mussels as indicators for food, predators, settlement spaces or during brood care and larval hatching. The main question is whether a drop in pH will render them ineffective.

For a molecule to be “smelled” by an animal’s receptor – usually its “nose”, although crabs actually smell using their antennae and even the tips of their legs – two characteristics are key: how the different bits of the molecule are arranged, or “conformed”, together, and whether it is positively or negatively charged. Both turn out to be affected by changes in pH.

Ocean acidification chemical signalling.

Nuclear magnetic resonance spectroscopy can be used to determine what happens to smell molecules in different pH conditions. But to assess what smell molecules of the future will be like (when the ocean will become more acidic) we need to use computer models.

The image below looks at three smell molecules used by crab larvae to communicate. While in their eggs, tucked underneath the female’s belly, the larvae release these smells to tell their mums when they need more ventilation, oxygen or assistance to hatch. The three smell molecules are shown as they are in today’s oceans (on the left) and under expected conditions until 2100 (on the right).

Three different smell molecules and how their charge and arrangement changes between now and 2100.
Roggatz & Lorch

Molecules representing the smell today are relatively compact and have very distinct areas of positive and negative charge (with green indicating neutral areas). In contrast, the future molecules are less compact and have an overall positive charge. These changes were found to happen exactly within the ocean pH range expected from today until the year 2100.

With both charge and conformation affected by pH changes, ocean acidification clearly affects the process of smelling.

Will animals still be able to smell?

This can be tested by observing animal behaviour in different pH conditions before and after a smell substance is added to the water. In our study we used female green crabs, also known as shore crabs (Carcinus maenas), Britain’s most common crab. In normal pH conditions, after the smell substance was added, the female crabs responded by increasingly ventilating their eggs.

But when we lowered the pH to the more acidic levels predicted for the year 2100, the crabs no longer responded to the smell. This suggests that in future oceans, smell molecules may lose their function.

The combination of computational, chemical and biological techniques has helped to uncover a new mechanism by revealing the molecular effects and actual consequences of changing pH in the world’s oceans on “scent”.

But what do these observed changes mean? The smell molecules tested in the study are examples for one class of chemicals and are known to play a role in the settlement of barnacle and oyster larvae, shell location of hermit crabs and brood care and larval release of shrimps and crabs.

This looks like a good spot … let’s tell the others.
Emil Larsen, CC BY

If all marine smell molecules were affected in a similar way, chemical communication in the ocean would be completely disrupted. It would be comparable to a world without light and sound for us humans.

Luckily, not all smell molecules are the same and some may work differently. How each one works will determine whether the crab or the octopus will end up with their lunchtime snack. At the moment we don’t know enough about smell molecules and their functions in the ocean to foresee the overall effects. The wider ecosystem consequences of this newly found mechanism, however, are yet to be investigated.

The Conversation

Christina C. Roggatz, PhD researcher in Marine Chemical Ecology, University of Hull

This article was originally published on The Conversation. Read the original article.

Moving beyond BMI for assessing the health of young people in Kingston-upon-Hull

Much has been written in recent years about the childhood obesity epidemic which is affecting record numbers of children from around the UK. However, what is perhaps less well known is that levels of muscular fitness and habitual physical activity have also declined significantly in young people over the past 25 years.
This is a considerable problem given the strong association between low levels of physical activity and muscular fitness, and the increased risk of cardiovascular disease and musculoskeletal ill-health. A team in the Department of Sport, Health & Exercise Science at the University of Hull led by Professor Lee Ingle has recently investigated this issue in two secondary schools in the Kingston-upon-Hull region. The study, recently published in the European Journal of Sports Science, compared the performance of nearly 600 boys and girls from the Hull region with an age- and sex-matched group of school children from similar socio-economic backgrounds in the south-eastern region of England. Each child completed a physical activity recall questionnaire, a vertical jump test, and a hand-grip strength test. Boys from the south-eastern region had significantly stronger hand-grip scores, jumped higher, were more powerful, and reported being more physically active than their male counterparts in the Hull region. In girls, the opposite trend was evident. Girls from the Hull region were stronger (based on hand-grip strength), jumped higher, and were more powerful than their peers from the south-eastern region. All analyses were adjusted to account for differences in age, body mass index (BMI), physical activity levels, and area level deprivation, between the children in the two regions.

Declines in young people’s fitness have prompted calls for the introduction of a more systematic surveillance of fitness in the UK, possibly as an addition to the current measurement of BMI (body mass divided by the square of body stature) within the National Child Measurement Programme (NCMP). There has been resistance to these calls from some quarters with concerns focused on how such a testing regime would impact on children of lower abilities. Parents of children deemed overweight or obese according to NCMP data receive a letter warning of potential ill-effects to their child’s health. Interpreting a single measure of body size for identifying an increase in health risk is clearly problematic. In our study, based on BMI alone, one interpretation of the data could be that boys from the south-eastern region and girls from the Hull region have greater health risks due to higher adiposity indicated by their higher BMIs (based on mean scores). However, when BMI values are interpreted in conjunction with measures of muscular fitness (from the hand-grip strength test), the data suggests no increased health risks as boys from the south-eastern region and girls from the Hull region are also stronger. The higher BMI values are likely to indicate greater lean body mass in    these groups, not excessive adiposity. Therefore, we advocate the implementation of a functional test such as the hand-grip strength test (which is less likely to impact on children of lower abilities) beyond a single assessment based on BMI within the NCMP. Furthermore, the identification of significant regional variations in muscular fitness that was not explained by anthropometric differences suggests that our current normative data derived from large regional samples (>10 000 children) should be expanded and updated. Therefore, a more systematic approach to fitness testing incorporating as many schools as possible in the Hull region is required prior to roll-out of any national fitness surveillance programme.

More information about the study can be found at the link below:

Lee Ingle, Ashlie Stephenson & Gavin R. Sandercock (2016): Physical activity profiles and selected muscular fitness variables in English schoolchildren: A north–south divide? European Journal of Sport Science. DOI: 10.1080/17461391.2016.1183714

University of Hull Proud to Announce Published Study into Evolution of Parental Care in Male Mammals

Dr Isabella Capellini, Senior Lecturer in Vertebrate Zoology and Hannah West, PhD Student at the University of Hull, have had their paper Male Care and Life History Traits in Mammals published in Nature Communications, the 3rd world ranking discovery journal.

Nature Communications is an open access journal that publishes high-quality research from all areas of the natural sciences.

Dr Capellini says: ‘In most mammals, males do not provide any care for their offspring but in about 10% of species males provision, carry, groom or huddle with them, and so spend substantial amount of time and energy in parental duties. So we were interested in finding out which potential benefits male parental care might have for mothers and offspring’.

Little is known about the substantial benefits that males may provide to females and offspring. Male care has energetic and opportunity costs, and is more likely to evolve when males gain greater certainty of paternity or when future mating opportunities are scarce.

The study aimed to determine the benefits males provide to females and offspring through male care. Phylogenetic comparative methods were used on a sample of 500 mammalian species.

The Results show that when males carry offspring a shorter lactation time occurs which leads to more frequent breeding, while litters are larger when males provision the mother. Offspring of species with male care grow faster.

The study proposes that males provide an energetic contribution during the most expensive time of female reproduction, which is lactation, and that different male care behaviours increase female fecundity, which in turn helps males offset the costs of caring.

Miss Hannah West says: ‘Surprisingly, we found that regardless of the specific behaviour – carrying heavy offspring or provisioning the mother – male care ultimately has the same ‘effect’ on female reproduction: when males care, females have more numerous offspring. This in turn helps males offset the costs of parental care as they can father more offspring’.

The study has been funded through a Hull Postgraduate studentship.

For more information visit, http://www2.hull.ac.uk/science/bbes.aspx

http://www.nature.com/ncomms/2016/160614/ncomms11854/abs/ncomms11854.html