Editorial Board Member’s Choice

4 11 2015

By Maria Luisa da Silva

Agonistic sounds and swim bladder morphology in a malapterurid electric catfish

K. S. Boyle, G. Bolen & E. Parmentier, 2015, Journal of Zoology, 296: 249-260.

I was glad to read this article about sound production in fish, because it is a field that must be better studied and this study represents an effort to cover the lack of information. The difficulties to study behaviour in fish start because they live in the water and we are terrestrial, so this team of researchers from University of Liège, Belgium, kept some individuals of Malapterurus beninensis in several aquaria and recorded their agonistic sounds. Many fish species produce sounds and sometimes it is a mystery which structure is responsible for the sound emission. The movement of the protactor muscle linked at “elastic spring apparatus” (ESA) during the production of low frequency drumming sounds in doradid catfish has already been described, and the authors present a detailed sound analysis of broadband clicks trains, unusual emissions among catfish families, with high-quality spectrograms and oscillograms.

The sounds that the authors observed M. beninensis to make were ratchet, click train and mouth sounds. Mouth sounds were single event, of low frequency and coincided with a bite-like motion, whereas ratchet and click sounds were high-frequency and occured in trains. This species also produced bubble sounds, however they did not coincide with behavioural interactions and seemed to be by-products of air released from the orobranchial chamber or the swim bladder. The authors also show impressive images of the swim bladder obtained by computerized tomography and histological and ultrastructure analysis. What is particularly interesting is that this structure has evolved several times among Siluriformes, especially in a group that also uses electrical signals for defence. However, the scope for answering questions like the authors proposed – ‘What is the evolutionary function of the ESA morphology in Malapteruridae?’ – it is limited in laboratory experiments to analyse and to interpret natural behaviour associated with sound production. If it is possible to study this species in a semi-captive, almost natural condition, with some control and maybe with waterproof cameras to identify which individual produce the sound, we might be better able to answer evolutionary questions about sound production in these fish.

New Journal of Zoology Podcast

21 09 2015

A new episode of the Journal of Zoology podcast is now available and you can listen to it here.

Journal of Zoology PodcastIn this episode, Raoul Manenti talks to us about how density and resource competition affects intraspecific aggression in a cannibalistic salamander that lives in caves, we will here from Rob Slotow about reintroduced lions and how resource selection models could help mitigate conflicts between them and the local people, and Inigo Zuberogoitia tells us about nest site selection behaviour and decision making in peregrine falcons.

You may subscribe in iTunes to receive the latest Journal of Zoology podcasts.

Elina Rantanen

Author Spotlight: The metabolic machinery putting the “fight” in Siamese fighting fish

20 07 2015

Biochemical correlates of aggressive behavior in the Siamese fighting fish

M. D. Regan, R. S. Dhillon, D. P. L. Toews, B. Speers-Roesch, M. A. Sackville, S. Pinto, J. S. Bystriansky and G. R. Scott


Aggressive interactions between individuals of the same species can result in the evolution of exaggerated body traits that improve success in these interactions, and subsequently, access to resources such as food and mates. Although conspicuous morphological adaptations such as antlers are usually what come to mind, metabolic processes that occur hidden within cells are required to sustain aggressive behaviour, so their enhancement may also be important for a successful outcome.

Siamese fighting fish, Betta splendens

Siamese fighting fish, Betta splendens; photo by Dave Toews

With this in mind, we designed a study to examine the intersection of aggressive behaviour and metabolic biochemistry using the Siamese fighting fish, a staple of the world’s pet shops. Male Siamese fighting fish are notoriously aggressive towards one another, fighting over access to territory and females. Because such aggressive behaviour is energetically costly, we hypothesized that more aggressive fish, which win more fights, would have a greater ability to generate cellular energy in their muscles than less aggressive fish, which tend to lose.

The research team

The research team; photo by Sheldon Pinto

The eight of us met in Hamilton, Ontario to run the behavioural experiments together in Dr. Graham Scott’s lab at McMaster University. These experiments involved pairing equally-sized male Siamese fighting fish in tanks and allowing them to “fight” one another from either side of a glass divider. The glass divider was necessary for the reason you probably guessed: these fish will do each other harm. Our goal with the experiments was to accurately quantify aggressive behaviour of the fish and then examine how the metabolic pathways supplying energy to the fish’s muscle cells varied with aggression, and ultimately, fighting success. We used behavioural assays to quantify aggression and estimate winners and losers, and biochemical assays to quantify reliance on, and capacity for, aerobic and anaerobic energy supply pathways.

Siamese fighting fish bouts aren’t on the level of, say, Ali vs. Frazier in ’75. But we’d be lying if we said excitement didn’t run high during each 20-minute encounter, with the fish striking at each other in fits and starts through the glass divider. At the end of each bout, muscle samples were taken from each fish on which we made our biochemical measurements of metabolic fuels, metabolic wastes, and enzyme activity rates.

Our results were very much in line with our predictions: winning fish were better able to supply energy to their muscles during fights than losing fish, and they were able to do this using two major strategies. First, the muscles of winning fish were better able to supply energy from aerobic pathways, which was matched with greater breathing frequency during fighting (Siamese fighting fish have the ability to breathe air). Second, the muscles of winners also made greater use of anaerobic energy supply pathways and accumulated more lactic acid as a result. Overall, fighting success appears to require muscles with a greater biochemical ability to supply energy, as well as an all-out exploitation of these metabolic pathways during fights.

Matthew Regan

Winner of the 2014 Journal of Zoology ‘Paper of the Year’ award

18 06 2015

Seeing through the skin: dermal light sensitivity provides cryptism in moorish gecko

D. Fulgione, M. Trapanese, V. Maselli, D. Rippa, F. Itri, B. Avallone, R. Van Damme, D. M. Monti, and P. Raia

The ability of some animals to rapidly change colour fascinates and astounds us in equal measure. Such colour change is enabled by specialized cells called melanophores in the animal’s skin, and this phenomenon has been observed for instance in octopuses, chameleons and fiddler crabs. This ability allows the animal to use its colour as camouflage and blend into their background that is heterogeneous or constantly changing, in order to conceal it from its predators or prey. However, the mechanisms by which animals perceive their surroundings to match their colour to the background are still not clear.

Moorish geckos Tarentola mauritanica are known to turn darker or lighter depending on the tone of their surroundings, and Domenico Fulgione and his co-authors from University of Naples Federico II and University of Antwerp wanted to examine whether these geckos match their skin tone to their surroundings via the nervous system, endocrine system or local cell response. In order to test this, the authors brought wild-caught moorish geckos into the lab and as treatments covered their eyes or their trunk, and then put them inside terrariums covered by either black or white paper and with a transparent lid. The team then observed whether the geckos were still able to change their colour to match the tone of their surroundings.

Surprisingly, the blindfolded individuals still changed their colour consistently with their background, whereas when the geckos had their trunk covered they did not change colour, even when they could see their surroundings. This and examinations of opsin levels in tissue samples from various parts of the geckos’ body led the authors to conclude that the moorish geckos have melanophores on their trunk that are light-sensitive and react to the light reflectance levels of their surroundings, leading to the observed skin colour change. Although a similar phenomenon has been observed in some non-amniotes such as tilapia and cuttlefish, this study has been the first to show evidence of such cryptic colour change triggered by dermal light perception in amniotes.

Elina Rantanen

New Journal of Zoology Podcast

30 04 2015

A new episode of the Journal of Zoology podcast is now available and you can listen to it here.

In this episode, we will hear from Pierre-Paul Bitton and Brendan Graham about the success of European starlings colonising North America and how this phenomenon may have been aided by their wing morphology, Madlen Ziege tells us how the burrow structure of European rabbits changes as they move from the countryside into cities, and we learn from Megan Owen how polar bears communicate via scent from their paws!

You may subscribe in iTunes to receive the latest Journal of Zoology podcasts.

Elina Rantanen

Recently Published in the Journal

16 03 2015

What animals can live in cryoconite holes? A faunal review

Zawierucha, M. Kolicka, N. Takeuchi and Ł. Kaczmarek

Glaciers support a whole range of life, from bacteria and algae to more complex organisms such as mosses, nematodes and arachnids, despite their harsh environmental conditions. Indeed, it has been suggested that glaciers should be treated as a new biome altogether. Cryoconite holes, which are small, water-filled reservoirs on the surface of glaciers, form microecosystems complete with simple trophic webs that sustain primary producers and primary and even secondary consumers. Cryoconite holes are formed when windblown dust or soot land on the surface of a glacier and start melting the ice, as they absorb heat from the sun owing to their dark colour. In their article published in the Journal of Zoology, Krzysztof Zawierucha and his co-authors provided the first comprehensive review of the fauna found living in cryoconite holes on glaciers around the globe. They found that only 26 papers published since 1885 have reported on cryoconite hole fauna, and these studies were conducted on glaciers located in the Arctic, Antarctic, Patagonia, Alps and Himalayas. These papers had found invertebrates from five phyla (Rotifera, Annelida, Tardigrada, Nematoda and Arthropoda) and 41 taxa living in cryoconite holes, forming basic food webs where primary consumers feeding on microbes and algae are prey to secondary consumers.

Raven Glacier; photo by Frank Kovalchek

Raven glacier, photo by Frank Kovalchek

Moreover, some of these animals are specifically adapted to these extreme environments: they may enter anabiosis in unfavourable conditions or produce dormant eggs, or have black pigment granules in their epidermis to protect them from the high levels of UV radiation, particularly in the polar regions. Furthermore, other studies have found in cryoconite holes bacteria that produce special antifreeze proteins. Further research will probably find more taxa inhabiting cryconite holes, and improve our understanding on how organisms adapt to living in these extreme environments. However, accelerated melting of glaciers due to climate change means that these ecosystems are disappearing at increasing rates, making them one of the most endangered ecosystems in the world.

Elina Rantanen

Author Spotlight: Adrian Barnett

4 02 2015

More food or fewer predators? The benefits to birds of associating with a Neotropical primate varies with their foraging strategy

A. Barnett and P. Shaw; Journal of Zoology, Vol. 294, Issue 4, pages 224–233, December 2014

Adrian Barnett

Adrian Barnett; photo by Eliana dos Santos

With some studies, you go into the field site with the idea and a series of questions ready formed, while others leap out and clamour for your attention while you are already there and doing something else. The study on uacaris and their influence on the foraging success of bird species is an example of the second.

With a group of Brazilian biologists, I was researching the feeding ecology of the Golden-backed uacari, a monkey which lives in igapó, the seasonally-flooded forests along the sides of blackwater rivers in central Amazonian Brazil. At the time almost nothing was known about the animal’s lifestyle, so what it ate seemed a pretty good place to start.

Paddling our small wooden canoes through the igapó we noticed that small antbirds would follow uacaris whenever they were in their territory. They would move along in the general direction of the uacari band, stopping when the monkeys left the bird’s territory. This didn’t make a lot of sense initially, because the antbirds feed on tiny insects that live in the moss and crevices on treetrunks. Not the kind of insects that you’d imagine get disturbed by a band of monkeys.

It was a different story, though, with the nunbirds and the jacamars, who are sit-and-wait predators feeding on grasshoppers and moths – exactly the kind of insects you can imagine leaping out of the way when monkeys are crashing around. Checking out how often these birds made their feeding sallies when monkeys were and were not around, we found that, indeed, yes, they fed more when monkeys were present. But what about the antbirds?

Golden-backed uacari; photo by Bruna M. Bezerra

Golden-backed uacari; photo by Bruna M. Bezerra

Well, it turns out that its not only grasshoppers that get out of the way of monkeys, small hawks do too. We’re not sure if its because they just find the monkeys annoying and leave, or if its because eagles feed on the monkeys and tend to follow them. And eagles also eat hawks. Either way, the upshot is that when and where there are monkeys there are fewer hawks. Which is good news for the antbirds, because its exactly these small hawks that are their major predators.

So, there is quite a lot going on, with two different groups of birds benefiting from the monkeys’ rumbuctious activities in quite different ways (while the hawks are probably off cursing in a corner somewhere).

Igapo forest in the Amazon; photo by Adrian Barnett

Igapo forest in the Amazon; photo by Adrian Barnett

Not only does it show the complexity of ecological interactions, the study is only the second time that anyone has actually shown that the presence of monkeys can increase feeding rates in some birds. People seeing monkeys and birds together have always assumed that the primates are acting as some sort of beater, but only one other study (on how gorillas visiting swamps increase lilly-trotter feeding rates) had actually shown it.

The work was done in Jau National Park in central Amazonian Brazil, and we continue our work there, trying to unravel the fascinating ecology of the seasonally-flooded igapó forests in which the monkeys and the birds in this study make their home.

Adrian Barnett

University of Roehampton / Instituto Nacional de Pesquisas da Amazônia


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