The effects of alcohol can beunpredictable; while some consumersbecome amiable and affectionate, othersturn into brutish thugs, and JensHerberholz, from the University ofMaryland, USA, explains that the cellularmechanisms that underpin theconsequences of intoxication remainelusive. ‘Alcohol is a complicated drug’,he says, because it affects a wide range ofcellular systems, making it difficult tounravel which factors contribute to alcoholsensitivity. However, humans are not theonly animals that can suffer theconsequences of over-indulgence;inebriated crayfish tail-flip animatedlywhile under the influence and becomeheavily intoxicated after lengthyexposures. Having studied the cellularmechanisms that underlie decision-makingand aggression in these crustaceans,Herberholz was curious to learn howprevious social experience might impactthe effect of alcohol on crayfish.
‘Howpast social experiencemight shape theneurobehavioural effects of acute alcoholexposure is significantly understudied’, saysHerberholz, who teamed up with hisstudentsMatthewSwierzbinski andAndrewLazarchik to find out how inebriatedcrayfish behave. Intoxicating individualcrayfish – which had previously beenhoused together – in tanks of dilute alcoholranging from 0.1 to 1 mol l−1, members ofthe lab filmed the animals as they initiallybegan walking aggressively on stiff straightlegs, before switching to tail-flipping as theybecamemore intoxicated, and finally losing
control as they rolled on their backs likeincapacitated humans. And the effects tookhold much faster at the highestconcentrations, with the intoxicated animalsenthusiastically tail-flipping after 20 min inthe strongest alcohol, while the animals thatwere bathed in the most dilute alcohol tookalmost 2h to feel the effects.However,whenthe trio tested the effects of the mostconcentrated alcohol on crayfish that hadbeen held in isolation for aweek before theirdrinking spree, the animals were far lesssensitive to the alcohol, taking 28 min tobecome inebriated and begintail-flipping.
But how were the effects of intoxicationmanifested in the neurons that control thecrayfish’s drunken behaviour? Insertingfine silver wires near the sensory nerves thatexcite the lateral giant interneuron – whichcontrols the tail-flipping behaviour –Lazarchik recorded that the neural circuitbecame more sensitive in both the isolatedand gregarious crayfish whenthe crustaceans were inebriated. However,the effects of alcohol became apparentmoreswiftly in the sociable crayfish’s lateralgiant interneuron, mirroring the animals’behavioural sensitivity. Swierzbinski waseven able to use intracellular electrodes tomeasure a difference in the effects ofalcohol in individual neurons in the isolatedand communal crayfish. Paying tribute toSwierzbinski, Herberholz says, ‘It takestalent and patience to collect data fromenough animals’.
As the inhibitions of the drunk socialisedcrayfish were loosened more than those ofthe drunken loners, Herberholz suspectsthat the alcoholhasmore of an impact on theGABA neurotransmitter, which inhibitsbehaviour, in the gregarious crayfish. Healso speculates that isolation could makehumans less sensitive to the effects ofalcohol, leading them to consume more.Herberholz says, ‘Our study shows thatsocial experience can change the sensitivityto acute alcohol’. He adds, ‘Inebriatedpeople…could potentially have differentresponses to alcohol depending on theirprior social experience’. And, although weare still a long way from confirming thatsocial experience produces similar effects inthe brains of inebriated mammals
(including humans), Herberholz isoptimistic that, one day, drunken crayfishcould help us to develop better treatmentsand preventative measures to supporthumans suffering from alcohol abuse.
10.1242/jeb.159822
Swierzbinski, M. E., Lazarchik, A. R. andHerberholz, J. (2017). Prior social experienceaffects the behavioral and neural responses toacute alcohol in juvenile crayfish. J. Exp. Biol.220, 1516-1523.
Kathryn Knight
Archer fish jump as wellas shoot
An archer fish take-off. Photo credit: Anna Shih.
While spitting is taboo in some humancultures, a few species have honed it to afine art, from cobras that eject venom intothe eyes of their victims to archer fish thatdown their prey with a precisely aimed jetof water. In addition, archer fish haveimplemented another weapon in theirhunting arsenal – they jump out of thewater to snap up prey – and AlexandraTechet, from the Massachusetts Instituteof Technology, USA, explains that thisalternative method of attack is more likelyto be successful than spitting when otherhungry archer fish are gathered round.‘It’s a competitive world out there. Whenthey spit there is no guarantee that they’llactually get to eat the prey, but when theyjump it’s almost guaranteed that theywill’, says Techet. With a passion fordesigning aquatic robots, Techet turned tothe agile archer fish for inspiration.
‘We trained them by hanging bait abovethe tank’, says Techet, who removed thebait whenever the fish tried to spit. Oncethe fish were vaulting reliably, Techet andAnna Shih filmed the animals with a high-speed camera as they attempted to reachGammarus shrimp suspended as high as
Inside JEB highlights the key developments in Journal of Experimental Biology. Written by science journalists, the short reports give the inside view ofthe science in JEB.
2.5 times the fish’s body length above thesurface of the water. Analysing the fish’stactics during the countdown, LeahMendelson observed that once the fishhad spotted the tasty treat, they hoveredbelow it weaving their pectoral fins to andfro until ready for the launch. ‘This part ofthe process is the same as when they huntby spitting’, says Techet. But as soon asthe take-off was initiated, the fish beganbeating their tails hard from side to sidewhile extending their pectoral fins as theysurged upward and broke through thesurface. Sometimes the tail continuedflapping to and fro even when they weresailing through the air. Correlating thenumber of propulsive tail beats with theheight reached, Techet was surprised tosee that instead of flapping harder, the fishincreased the number of tail beats to reachthe highest bait, landing an impressive70% of their catches.
In addition to determining the fish’slaunch technique, Techet and Shihvisualised the swirling patterns generatedin the water as the fish powered upward tolearn more about the forces that propel thefish into the air. Although convincing thefish to jump in a plane of laser light whilefilming was technically challenging,Mendelson eventually discovered that thefish used their tails in combinationwith theanal, pectoral and dorsal fins to generateenough thrust to become airborne. Andwhen she calculated the energetic cost of afish launch and compared it with theamount of energy consumed during thefrantic dash to capture prey after asuccessful squirt, the two came out aboutequal – ranging from 2.5 to 47 mJ –suggesting that the jump strategy may beas efficient as pursuing a victim downedby a well-aimed jet of water.
Having revealed how the fish jump out ofthewater from a stationary position, TechetandMendelson are now keen to learn moreabout the contribution of the tail and otherfins to the lift-off, and Techet adds, ‘Thiswork serves as the foundation for ourultimate goal’, which is to produce a 3Dmodel of the physics of a launch to designarcher-fish-inspired robots that can take offsmoothly from water.
10.1242/jeb.159806
Shih, A. M., Mendelson, L. and Techet, A. H.(2017). Archer fish jumping prey capture:kinematics and hydrodynamics. J. Exp. Biol.220, 1411-1422.
Kathryn Knight
Spinner dolphin SCUBAtanks develop no faster
Spinner dolphins. Photo credit: US Fish andWildlife Service Headquarters (uploaded byDolovis) [CC BY 2.0, via Wikimedia Commons].
Just because dolphins are born in waterdoesn’t necessarily mean that their in-built SCUBA system is fully prepared foraction at birth; it can take between 1 and3 years for the oxygen carrying capacityof whales and dolphins to maturesufficiently. Shawn Noren, from theUniversity of California, Santa Cruz,USA, explains that the muscles of fullydeveloped diving species – includingdolphins, whales, birds and seals –contain more of the oxygen carryingprotein, myoglobin, than land-basedanimals and are better prepared toneutralise lactic acid produced in themuscles when divers switch to anaerobicrespiration after exhausting their oxygentoward the end of a dive. ‘Wewondered ifpelagic (offshore) living promotes rapidpostnatal maturation of musclebiochemistry’, says Noren. In other words,might deep-diving ocean-going whalesand dolphins develop large reserves ofmyoglobin and the ability to buffer muscleagainst acid earlier in life than species thatremain in shallow coastal waters?
As it is almost impossible to collectmuscle samples from spinner dolphins inthe open ocean, Noren depended onKristi West, from Hawaii PacificUniversity, USA – who set up a dolphinstranding program in Hawaii 11 yearsago and attends all strandings on theisland – to collect the essential samples.Over 7 years, West collected smallportions of the swimming muscle from17 spinner dolphins that her team hadbeen unable to rescue – ranging from afetus that died during birth to newborns,adolescents and fully grown males andfemales. She then shipped the samples toSanta Cruz, where Noren painstakinglyanalysed the muscles’ myoglobin contentand how much sodium hydroxide shehad to add to 0.5 g of minced muscle toraise the pH from 6 to 7 to measure themuscle’s buffering capacity against
anaerobic acid production. Plotting theanimals’ body lengths (which correlatewell with their ages) against their musclemyoglobin content, Noren could see thatthe dolphins’ abilities to carry oxygencontinued increasing as the animalsaged. The ability of the muscle to bufferagainst pH changes also increasedgradually; however, it reached thecapacity of the mature dolphins andplateaued at an age around 1.6–2 years,when the dolphin youngsters are weaned,which is similar to the age at which thediving apparatus of some coastal speciesreaches maturity.
So ocean-going spinner dolphin calvesdo not develop the physicalcharacteristics that are essential to sustaindeep dives any faster than shallow-diving coastal species, such as bottlenosedolphins. However, the youngest spinnerdolphins already had higherconcentrations of muscle myoglobin thancoastal bottlenose dolphins at thesame ages, and the adult spinnerdolphins’ myoglobin concentrations(6–7.1 g Mb 100 g−1 wet muscle mass)matched those that had been measuredpreviously for other champion divers,including short-finned pilot whales andGervais’ beaked whales.
But what implications might the relativelyslow development of their divingapparatus have for young spinnerdolphins in the Eastern Tropical Pacific?Knowing that tuna purse-seine fisheries inthis region specifically target dolphinpods – they pursue the animals toexhaustion before encircling them inenormous nets to capture the tuna shoalsthat reside beneath –Noren calculated thatan immature calf that cannot keep upmight be adrift of its mother by up to15.4 km by the end of a 100 min pursuit.Noren says, ‘The relativelyunderdeveloped muscle biochemistry ofcalves likely contributes to documentedmother–calf separations for spinnerdolphins chased by the tuna purse-seinefishery’, and this could affect dolphinpopulations dramatically if our hunger fortuna continues to separate dolphin calvesfrom their mothers.
10.1242/jeb.159798
Noren, S. R. and West, K. (2017).Muscle biochemistry of a pelagic delphinid(Stenella longirostris longirostris): insight intofishery-induced separation of mothers andcalves. J. Exp. Biol. 220, 1490-1496.
Kathryn Knight
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INSIDE JEB Journal of Experimental Biology (2017) 220, 1369-1371
Lynne Sneddon is a myth buster. Havingdebunked the fisherman’s legend that fishdon’t feel pain, Sneddon, from theUniversity of Liverpool, UK, has becomea leading figure in the movement toreduce, replace and refine the use ofanimals in scientific research.Uncomfortable with the increasing use ofadult fish in pain research, Sneddon andJavier Lopez-Luna decided to testwhether tiny zebrafish larvae feel pain.‘Previous studies have identified multiplesubtypes of nociceptors [pain receptors]in zebrafish…even as early as a few dayspost-fertilization’, the team says. Couldthey replace the adult fish that are used inresearch with larvae that are a matter ofdays old? Only if they could prove that thefish respond to pain and any discomfortcould be relieved.
Lopez-Luna and Sneddon exposed 5-day-post-fertilization zebrafish embryos todilute concentrations of acetic acid andcitric acid, both of which are known toirritate adult fish, and tracked the larvae’sactivity with software produced byQussay Al-Jubouri and Waleed Al-Nuaimy. Analysing the minute fish’smotion, Lopez-Luna and Sneddonnoticed that the larvae became less activein the two most dilute concentrations ofacetic acid (0.01 and 0.1%). However, themost concentrated acetic acid (0.25%) andall three concentrations of citric acid (0.1,1 and 5%) stimulated the fish to swimharder and farther, possibly in a bid toescape the uncomfortable sensation. Butwhen Lopez-Luna administered painrelief to the disturbed fish larvae – in theform of aspirin, morphine and lidocaine –
their discomfort appeared to be relievedand their behaviour returned to normal.
Having confirmed that larval fish arecapable of experiencing pain and benefitfrom pain relief, Sneddon and Lopez-Luna recommend, ‘Larval zebrafish canbe used as a model for the study of painand nociception’, sparing many of theadult fish that are currently used intoxicity tests.
10.1242/jeb.159814
Lopez-Luna, J., Al-Jubouri, Q., Al-Nuaimy, W.and Sneddon, L. U. (2017). Reduction in activityby noxious chemical stimulation is ameliorated byimmersion in analgesic drugs in zebrafish. J. Exp.Biol. 220, 1451-1458.
