Outside JEB iv afford tomiss. papers thatJEBreaderscanʼt research scientistshighlightthe and writtenbyateamofactive articles thathavebeenselected experimental biology. Short most excitingdevelopmentsin monthly featurethatreportsthe isnʼt easy, soOutsideJEBisa Keeping trackoftheliterature Outside JEB THE JOURNAL OFEXPERIMENTAL BIOLOGY two behavioralstates. To this end,theykept drive locomotor rhythms tailoredforthese wanted toseewhetherE21activation can behavior areverydifferent. Theteam and themotorprogramsunderlying each Leeches swiminwaterbutcrawl onland a veryrigidcommandcircuit. flexibility towhatwasthoughtatfirstbe The presenceofthebrainclearlyadded had noef fictive swimming,butinothers,stimulation preparations, stimulatingthecellenhanced swim circuitwerewildlyvariable.Insome brain attached Surprisingly, theduofoundthatwith effects onfictivemotorpatterns. stimulated E21andmeasuredanyresulting motor nerve.Duringswimbouts,they evoked fictiveswimepisodesbyshockinga cord andputtheminadish.Thenthey this, theydissectedoutthebrainandnerve modulated whenthebrainwasintact.To do E21’s abilitytodriveswimmingwouldbe exclusively. Theteamwantedtosee how initiates andenhancesfictiveswimming ‘command-like’ neuron.Whenstimulated,it absence ofthebrain,appearstobea identified aneuron(E21)that,inthe In previouswork,MullinsandFriesen verbena. this assumptionistrueintheleech of Virginia recentlydecidedtoseewhether Mullins andOttoFriesenattheUniversity with orwithoutthebrain.However, Olivia preparations arefundamentallythesame has alwaysbeenthatcircuitsinthese animals. The(largely untested) assumption properties ofmotorcircuitsinmany rhythms’ havebeenusedtouncover Preparations thatgeneratesuch‘fictive from sensorysystemsorthebrain. rhythmic motorpatternswithoutinputs invertebrates (nervecords)oftengenerate Spinal cordsandequivalentstructuresin NEURON OUTPUT FLEXIBILITY TO COMMAND LEECH BRAINADDS MOTOR SYSTEMS fect orexactlytheoppositeeffect. , E21’s actionswithinthe Hirudo systems. grasp howflexibilityisgeneratedinmotor approach maybethebestwaytoreally them. Attheendofday, thissimple progressively addcomplexitybackinto with suchisolatedpreparationsandthen also highlightshowusefulitistobegin preparations. Paradoxically, theteam’s work we interpretdatafrom‘brain-less’ the brain,andsoweneedtobecarefulhow fundamentally different inthe absenceof always true.Motorcircuitscanindeedbe assumption inmotorsystemsresearchisnot important becauseitshowsthatalong-held The workofMullinsandFriesenis attached preparations. seen whenE21isstimulatedinbrain- inputs accountsformuchofthevariability modulation ofthissynapsebydescending mysterious, butitispossiblethatthe variability. Themechanismremains synapses areweakerandshowincreased when thebrainispresent,connecting E21 stronglyexcitesgatingcells;however, are shortened.Intheabsenceofbrain, synapse isweak,triggeredswimepisodes episodes, sowhentheE21-to-gatingcell cell activityisrequiredtomaintainswim cell typeknownto‘gate’ swimming.Gating a synapsebetweenE21anddownstream inputs fromthebrainaffect the strengthof E21? Theteammeasuredhowdescending flexibility tothecircuitscalledintoplayby How doesthepresenceofbrainadd isolated preparationslackingbrains. This effect wascompletelymaskedin appropriate behaviorbasedonsensorycues. are commandingmotorcircuitstodoan circuits todoasinglebehavior, E21cells instead ofrigidlycommandingdownstream enhanced crawling.Thissuggeststhat ground, E21activationinitiatedand when theanimalwasfacedwithsolid enhancing swimepisodesexclusively. But the wateryenvironment,E21wentbackto solid substrate(tostimulatecrawling).In from deepwater(toenhanceswimming)to placed insensoryenvironmentsranging swimming. Thefrontpartoftheleechwas E21 andmotornervesinvolvedin intact, whilesimultaneouslyrecordingfrom the brainandanteriorregionsofleech control. matters: effects ofdescending signalsonmotor Mullins, O.J.andFriesen,W. O. 10.1242/jeb.064253 J. Neurophysiol. Janelia FarmResearchCampus [email protected] doi: 10.1152/jn.00107.2012. (2012) Thebrain Stefan Pulver Outside JEB v relationship between dewlap size and bite force. They predicted that if the handicap hypothesis is correct, and the cost of maintaining the bright dewlap maintains the honesty of the signal, then food restriction should limit both dewlap size and bite force. The question is, when the times are tough, do the lizards stay honest?

To answer this question, the authors captured juvenile male green anoles and raised them to sexual maturity in the laboratory, under either food-restricted or plentiful diets. At the end of the study, both dewlap size and bite force were measured. The authors discovered that while lizards COMMUNICATION

with plenty of food developed the typically CRYOPROTECTION honest relationship between dewlap size WHEN THE TIMES GET TOUGH, and bite force, the food-restricted males FRUIT FLIES ON ICE THE LIZARDS START LYING developed the bright dewlaps without The ability to survive freezing comes For the most part, it seems that animals developing the corresponding bite force. naturally to a select group of . These communicate honestly with one another. Therefore, food-deprived lizards were not cold-adapted species live in areas Individuals use various signals such as as honest as their resource-rich where they might experience sub-zero elaborate colours or ornaments to convey counterparts. Moreover, it appears that for temperatures for at least some of the year. information to others about their fighting green anoles, bite force itself is more costly But Drosophila melanogaster, the favourite ability or potential value as a mate. Signals than the bright dewlap signal. fly of researchers from several life sciences are useful, and communication can save disciplines, is better known for its time and energy. For example, mismatched As the cost of a bright dewlap doesn’t keep preference for the warmth of human rivals can avoid a risky dual if they can the lizards honest, what factors maintain kitchens and is injured by cold – even at communicate their fighting ability, and the dewlap size? The authors suggest several temperatures above freezing. Scientists weaker opponent cede to the stronger. explanations, including the possibility that would love to know how to successfully social feedback might play an important put these flies into suspended animation The lingering puzzle of animal role. In this study, lizards were raised in using cryopreservation to maintain their communication is why animals are honest individual cages, and did not interact with valuable stocks of laboratory-modified D. with one another. On the surface, it would one another. However, in the wild, melanogaster lines. In recent work seem beneficial to embellish exaggerating about bite force with a bright published in Proceedings of the National communication signals. What animal would dewlap might land a lizard in a fight where Academy of Sciences, Vladimir Koštál and not want to appear stronger and more he is overmatched and could be injured. colleagues from the Czech Republic show attractive? The classic explanation is the While more research is necessary to fully that with a few simple tricks picked up ‘handicap hypothesis’, or the hypothesis understand the factors that maintain honest from a freeze-tolerant cousin, it is possible that the cost of communication signals communication signals, it seems that, for to convert the chill-susceptible D. maintains the honesty of these signals. One lizards, honesty is still the best policy. melanogaster into a fly that can survive common example is the tail of the peacock. freezing. This lavish adornment is so cumbersome 10.1242/jeb.064246 that only strong males can haul around an Lailvaux, S. P., Gilbert, R. L. and Edwards, J. R. Earlier work by Koštál and his colleagues (2012). A performance-based cost to honest signalling impressive tail and still escape from in male green anole lizards (Anolis carolinensis). Proc. showed that Chymomyza costata, a predators. R. Soc. B doi: 10.1098/rspb.2011.2577. drosophilid fly closely related to D. melanogaster, has two requirements to Simon Lailvaux, Rebecca Gilbert and Constance M. OʼConnor survive freezing: (1) it must be in Jessica Edwards from the University of McMaster University developmental arrest (called diapause) New Orleans put the handicap hypothesis to [email protected] during an overwintering stage, and (2) it the test in a unique way using green anole must accumulate large quantities of the free lizards (Anolis carolinensis). The green amino acid proline. The authors thought a anole is an excellent subject for such a similar protocol might work for D. study, as male green anoles signal to one melanogaster. First, the team reared larvae another with a brightly coloured dewlap – a at either room temperature or a relatively flap of skin beneath the jaw that they can low temperature for D. melanogaster extend and retract – and the size of this (15°C) until they reached the final larval dewlap is an honest signal of their bite stage. Then, they subjected the larvae to force, an essential trait for fighting. temperatures that fluctuated between 6°C Importantly for the study, the dewlap is and 11°C for 3days to induce a type of developmentally unrelated to the muscles diapause. In addition, some of the insects surrounding the jaw that generate bite force, were fed diets rich in known so it is possible for the two traits to vary cryoprotectants: glycerol, proline or independently of one another. Lailvaux and trehalose. Finally, the team slowly cooled his colleagues investigated whether the flies to –5°C and held them there for resource limitation would change the honest

THE JOURNAL OF EXPERIMENTAL BIOLOGY Outside JEB vi over an hour before allowing the insects to Laurence Cook from the University of resume development. Manchester and an international team of collaborators. The researchers found that feeding the larvae diets rich in cryoprotectants or Working in his Cambridge backyard, subjecting them to fluctuating temperatures Majerus overcame the flaws in Kettlewell’s both increased the larvae’s survival of design and validated the predation freezing, but only for a short time after the hypothesis. Black and white indeed stress. However, the combination of the rest on tree trunks and branches. More proline-rich diet in particular with the importantly, predatory birds do feed fluctuating temperatures had a synergistic preferentially on the less camouflaged effect, producing larvae with almost a 10% morph. In today’s cleaned-up post-industrial chance of surviving to reproduce landscape, the black morph is more successfully after being frozen at –5°C for conspicuous and its survival level is about over an hour – which is long enough to 10% lower than that of the white morph. convert half of their body water to ice. However valid the doubts were about Kettlewell’s experiments, Majerus’s results NATURAL To investigate how these treatments should now silence the critics. protected the diapausing larvae from PEPPERED MOTHS IN BLACK freezing to death, the authors measured the AND WHITE Science, unlike creationism, is self- concentration of several of the larvae’s The peppered represents one of the correcting. Cherished ideas can be tested metabolites after consuming their most iconic examples of natural selection in and amended or overturned. The strategy of cryoprotectant-supplemented diet, using action. The popular account of its creationists, in contrast, is to target single mass spectrometry. They found that the is both simple and intuitive. Nineteenth examples for scorn while offering neither larvae fed on the supplemented diets all century industrialization in Britain ideas nor credible tests to support their accumulated extra cryoprotectant, although dramatically altered the landscape. Pale challenges. Majerus was not the only the proline-supplemented diet had the lichen covering tree branches was killed person in Britain with moths in his largest effect on cryoprotectant and trees blackened with soot. On this backyard, but he was the only one carrying concentration. The authors thought that background, white peppered moths that out the hard work to test predictions of the perhaps the larvae do not control their sheltered on the trees became conspicuous story. Unfortunately, he died proline levels as tightly as they do other targets to visual predators and were eaten, before he could prepare his work for metabolites, which might have contributed causing their decline. Simultaneously, publication. Now freely available, his data to the success of proline in producing because they escaped detection, mutant are both interesting and important. They freeze tolerance. black moths increased in frequency. The also serve as a clear demonstration of how predation explanation was plausible and science works by building an ever more While Koštál and colleagues plan further well tested. It was a classic textbook case. refined understanding of the natural world. studies into the mechanisms of proline’s Creationists, with their unscientific agenda, effects, this first report of inducing freeze In 1998, however, the story took an working at so-called ‘research’ institutes, tolerance in a tropical insect like D. unexpected turn. Cambridge geneticist and can offer nothing of substance in response. melanogaster contributes to the elucidation lepidopterist Michael Majerus published a of the mechanisms of natural freeze book that raised legitimate questions about 10.1242/jeb.064220 tolerance, and may lead to an end of the Bernard Kettlewell’s predation experiments, Cook, L. M., Grant, B. S., Saccheri, I. J. and Mallet, J. (2012). Selective bird predation on the peppered labour-intensive work of maintaining the foundation of the moth story. Were moth: the last experiments of Michael Majerus. Biol. laboratory fly stocks. Kettlewell’s experiments natural? Was it Lett. doi: 10.1098/rsbl.2011.1136. appropriate to study the responses of birds 10.1242/jeb.064238 to dead moths arranged on trees? Did Daniel E. Rozen Koštál, V., Šimek, P., Zahradníčková, H., Cimlová, moths even rest on tree trunks where University of Manchester J. and Štětina, T. (2012). Conversion of the chill susceptible fruit fly larva (Drosophila melanogaster) to Kettlewell had put them? This questioning [email protected] a freeze tolerant organism. Proc. Natl. Acad. Sci. USA triggered a firestorm of controversy that doi: 10.1073/pnas.1119986109. raged.

Katie Marshall A book review in Nature implied that the University of Western Ontario moth story was as disappointingly uncertain [email protected] as Santa Claus, while another book accused Kettlewell of fraud. Despite the defence from scientists that it was not the predation hypothesis itself that was in doubt, creationists rejoiced. The curiously named Institute of Creation Research railed that ‘the supposed best proof of evolution in action is so flimsy that it cannot stand the test of truth’. However, this controversy has finally been put to rest in a Biology Letters paper based on Majerus’s experiments by

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