Shark's Spring-Loaded Vertebral Column Provides Continuous

INSIDE JEB

Belugas’ SCUBA tanks term foetus to mature adults – that had important prey of belugas – will follow, died from natural causes and as part of because cod prefer living near the ice better primed at birth the Point Lay community annual beluga edge and the belugas may follow. subsistence hunt in the Chukchi Sea. Indeed, there is evidence that when sea- ‘This collaboration allowed us to obtain ice cover is low, belugas are further sufficient samples within one season’, offshore. This range shift may be explains Noren. problematic for immature belugas and females with calves that prefer Once all of the samples had been nearshore habitats and are disadvantaged assembled, she measured their when competing for resources with myoglobin concentrations. Interestingly, larger animals that have greater dive the myoglobin concentration in the capacities’, Noren explains. muscle of newborn beluga calves 10.1242/jeb.149062 [1.56 g (100 g wet muscle)−1] was higher Noren, S. R. and Suydam, R. (2016). Navigating Beluga mother and calf. Photo credit: Shedd than that of other newborn cetaceans [0.13–1.3 g (100 g wet muscle)−1], under sea ice promotes rapid maturation of Aquarium/Brenna Hernandez. diving physiology and performance in beluga making belugas better prepared for diving whales. J. Exp. Biol. 219, 2828-2836. at birth than other species. However, In the icy waters of the Arctic Ocean, a Kathryn Knight beluga mother gently noses her newborn when Noren turned to the samples to the surface for its first breath. These collected from older calves, she was ocean-going mammals are as dependent astonished to see that their myoglobin on air as we are, and must visit the levels had rocketed and were similar to Shoaling soothes surface regularly throughout their lives. those of fully grown adults. ‘During the damselfish However, many young cetaceans lack first year, the amount of myoglobin per the full range of physiological 100 g of muscle increased by 452%, and adaptations essential for long duration mature levels are achieved by 14 months dives. Adult marine mammals usually after birth’, she exclaims. Noren also have high levels of the oxygen-carrying calculated the amount of oxygen that each protein myoglobin in their muscles, animal could carry and then used the which act like a SCUBA tank carrying value to calculate the maximum dive oxygen that can be released gradually length and depth that they could sustain. Impressively, both the dive length during the course of a dive. In addition, Chromis viridis on the Great Barrier Reef, they also have the capacity to neutralise and depth increased dramatically over the Australia. Photo credit: Amy Cox. lactic acid released into the muscle first year of life, from 3.6 min and 216 m – when they exhaust their oxygen supply at birth to 8.54 min and 512 m in Glinting beneath tropical balmy waters, and switch to anaerobic respiration. ‘For contrast to fully grown adults (>10 years) the Great Barrier Reef is one of the bottlenose dolphins it takes up to that perform dives of up to 14 min and can brightest shows on earth. With 3 years for the muscle biochemistry for reach depths of 812 m. However, the shimmering shoals of iridescent fish ’ diving to be fully mature’, says Shawn youngsters ability to neutralise acid ceaselessly darting between glimmering ’ Noren, from the University of produced by anaerobic respiration wasn t coral edifices, the spectacle is enchanting. California, Santa Cruz, USA. Yet much greater than that of other young ‘The complexity of interactions between from an early age, baby belugas must cetaceans. animals out on the reef is really amazing’, follow their mothers under the sea ice, says Lauren Nadler from James Cook where air holes are transient and scarce. ‘Baby marine mammals are not just University, Australia, who is intrigued Could the youngsters develop the small versions of adult marine by the factors that drive fish to form essential physical adaptations that mammals’, says Noren, who suspects shoals. ‘I had heard whispers and read would permit them to navigate for that the rapid maturation of the calves’ some anecdotal evidence on this idea of a lengthy periods beneath the ice at diving physiology is driven by the calming effect of living in a group. The an earlier age than other marine necessity that they accompany their rationale is that group-living may make mammals? mothers beneath sea ice from an early individuals less fearful of threats, due to age. However, she is concerned that the having “many eyes” to look for predators. Intrigued, Noren and Robert Suydam, retreat of the sea ice at the North Pole This reduction in stress may allow fish to from the Alaskan Department of could place these animals under reduce their overall basic energetic Wildlife Management, collected muscle increasing stress. ‘As sea-ice recedes needs’, says Nadler. However, no one had samples from belugas – from a full- further offshore, cod – which is an succeeded in measuring the metabolic

Inside JEB highlights the key developments in Journal of Experimental Biology. Written by science journalists, the short reports give the inside viewof the science in JEB. Journal of Experimental Biology

2775 INSIDE JEB Journal of Experimental Biology (2016) 219, 2775-2777 rates of individual fish in the midst of a impressive drop in metabolic rate when escapades are unsuccessful, Entler, John shoal. ‘There have been studies that they were reintroduced to their shoal. Cannon and Marc Seid wondered whether looked at how the group as a whole is the highly motivated insects could get changing in terms of their overall energy Converting the enormous energy savings hooked on a life of self-administered drug demands, but they have not been able to gained from living in a shoal into practical dependency. get at that individual change’,says benefits, Nadler explains, ‘They have Nadler. extra energy for all sorts of things; they can go out and find mates and reproduce Tempting Florida carpenter ants to visit a After discussing the challenge of how to and they have more energy to grow, and feeder full of tasty sugar solution, Entler simulate the conditions experienced by these are all processes that are going to gradually removed the sugar while individual damselfish without letting them help them to survive and do really well simultaneously increasing the directly interact with the other members of out on the reef and pass their genes on to concentration of highly addictive the shoal with Philip Munday, Mark the next generation of fish’. morphine over a 6-day period in a bid to McCormick and Shaun Killen, Nadler get them hooked. Initially, the ants lost began developing a new respirometry 10.1242/jeb.149070 interest in the feeders as the sugar concentration declined; however, once the approach. She started by placing a fish in a Nadler, L. E., Killen, S. S., McClure, E. C., glass tube – which allowed her to measure Munday, P. L. and McCormick, M. I. (2016). insects were completely weaned off the their oxygen consumption – while Shoaling reduces metabolic rate in a gregarious sugar and only the morphine remained, immersing it in a tank surrounded byshoal- coral reef fish species. J. Exp. Biol. 219, the ants’ interest in the feeder was 2802-2805. mates. The isolated fish remained calm so rekindled. And when Entler offered the long as it could see and smell its chums; Kathryn Knight ants a choice of snacks – a feeder full of however, the fish’s serenity vanished as tasty sugar solution versus another soon the shoal-mates swam away. ‘When containing the drug – their preferences the fish in the chamber couldn’t follow, it Ants discover inner junkie were abundantly clear as they headed for would thrash around and make its the morphine-laced feeder to feed their metabolic rate increase’, she recalls. The habit despite the lack of nutrition. next time, she introduced a second However, when Entler offered ants that chamber to ensure that the shoal remained had never touched the drug the same in close proximity, allowing her to measure option, they clearly sought out the sweet the oxygen consumption of an individual treat. The ants were certainly attracted to fish while surrounded by its shoal. morphine, but were they getting the reward-seeking ‘high’ of true junkies or Having refined the details of the did they just prefer the taste of morphine technique, Nadler tested the method on water? Campanotus floridanus. Photo credit: Marc damselfish collected at the Lizard Island Seid. Research Station on the Barrier Reef. ‘One To answer the question, Entler analysed of the things I wanted to do was make sure Viewed from a great height as we scurry the ants’ brains to find out whether I was using fish that had already been about, it can be hard to tell the difference they were producing any of the tell-tale living together in shoals, to ensure that I between human and ant societies. We both neurotransmitters that indicate addiction, wasn’t freaking them out by exposing live in highly organised communities and found that the morphine-fed ants them to strangers as opposed to friends’, surrounded by architectural structures had higher levels of dopamine, which says Nadler. After using a barrier net to where each individual has a well-defined directs reward-seeking behaviour: the herd shoals together with Eva McClure role. However, Brian Entler and ants were true junkies. ‘This study and transporting the fish back to the lab, colleagues, from The University of establishes ants as the first non- Nadler measured the metabolic rates of Scranton, USA, wondered whether we mammalian model of self-administration individuals in isolation and when may also share a darker side to our that is truly analogous to mammals’, says surrounded by their shoal-mates, and saw characters. The team explains that some the team, who are keen to begin an extraordinary 26% drop in metabolic insects are capable of forming addictions untangling the basic neural circuits that rate, ‘which is really quite a lot’, she says if the drug is delivered simultaneously drive drug addiction in ants and probably understatedly. The fish were certainly with food, teaching us essential lessons humans. soothed when surrounded by friends in a about the neurobiology of addiction. shoal. And when Nadler kept individuals However, humans have the ability to 10.1242/jeb.149047 in solitary confinement for several weeks, become addicted to drugs that provide the strain was evident as they initially lost pleasure alone, and no other species seem Entler, B. V., Cannon, J. T. and Seid, M. A. (2016). weight. However, after a fortnight, their to be able to develop such an addiction Morphine addiction in ants: a new model for self- condition stabilised, and when Nadler without the added temptation of food. administration and neurochemical analysis. J. Exp. Biol. checked the metabolic rates of these Knowing that ants are keen to scurry 219, 2865-2869. isolated fish, she found the same around searching for titbits even if their Kathryn Knight Journal of Experimental Biology

2776 INSIDE JEB Journal of Experimental Biology (2016) 219, 2775-2777

Shark’s spring-loaded vertebral column provides continuous variable power transmission

At the core of the shark’s hypnotic composite of different materials’, they They suspect that the shark’s swimming motion, there is an elastic say. So they decided to investigate how remarkably elastic spinal column may secret. Marianne Porter, from Florida sections of the vertebral column become more springy to provide more Atlantic University, USA, explains that (comprising 9 or 10 vertebrae) from propulsion as the animal increases the fish’s cartilaginous skeleton allows spiny dogfish (Squalus acanthias) exert speed, while increasing braking power energy to be stored in the vertebrae as force as the team systematically wiggled as the shark continues beating the tail the vertebral column bends, compressing them to and fro over realistic swimming over a wide amplitude but at a slower the bulky centra structures that stack curvatures and tailbeat frequencies rate when slowing down. And the team together to build the spinal column. This ranging from one tailbeat every 4 s to suggests that the vertebral column’s energy is then released at the end of a two tailbeats per second. unique combination of material tailbeat to power them on their way. properties provides ‘continuous variable According to Porter, the elastic vertebral Measuring the displacement of the power transmission’ to smoothly power column could store and release as much section of spinal column as it flexed sharks on their way. as 10% of the shark’s energy, providing and the force exerted at the end, the trio a substantial advantage over the rigid was then able to calculate how the 10.1242/jeb.149039 skeletons of bony fishes. However, stiffness of the vertebral column Porter, M. E., Ewoldt, R. H. and Long, J. H., Jr (2016). Automatic control: the vertebral column of Porter and colleagues Randy Ewoldt and (energy storage) and energy dissipation dogfish sharks behaves as a continuously variable John Long suspected that shark spinal (braking power) varied. ‘Based on its transmission with smoothly shifting functions. columns were more than simple springs mechanical behaviour, the vertebral J. Exp. Biol. 219, 2908-2919. because of their complex material column may serve as both a spring and Kathryn Knight properties; ‘[the vertebral column] is a abrake’, say Porter and colleagues. [email protected] Journal of Experimental Biology

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