Journal of Experimental Biology - Latest Issue

• Honeybees express foodward flight vectors after a detour

  ABSTRACT

  The honeybee waggle dance communicates a flight vector to a food source, but it is challenging to isolate how precisely dancers and recruits can navigate using this vector information independently of environmental cues. We introduce an enforced-detour paradigm, using tunnels, to quantify the initial flight vectors expressed by experienced foragers and new recruits en route to the food. Upon exiting the detour, bees exhibit immediate corrective turns consistent with using path integration to fly towards the food's virtual location. While the populations' flight bearings after the turn are correctly centred on the food, the bearings of individuals are considerably scattered around it. We further show that recruits' bearings can be predicted by observing their mechanical sensory experiences during dance following. Our findings suggest that the communicated or recalled vector can be combined with path integration to take corrective shortcuts, but also that the vector provides an approximate location rather than pinpoint accuracy.

• Integrated response of the zebrafish ( Danio rerio ) cardiovascular system to hypoxia acclimation

  ABSTRACT

  Chronic hypoxia exposure of fish can cause remodelling of the gills as well as increases to haematocrit and haemoglobin binding affinity. There is less known, however, about how chronic hypoxia affects the structure and function of the heart. In the current study, zebrafish were exposed to moderate hypoxia for 7 weeks and then ultrasound was used to characterize cardiac function. We found that cardiac output of the hypoxia-acclimated fish was greater than that of the control fish during an acute hypoxia exposure. This difference was due, at least in part, to the higher cardiac stroke volume. Histological measurements demonstrated an increase in the cross-sectional area of the ventricle of hypoxia-exposed fish and this was supported by higher end diastolic area measurements made using ultrasound. These changes to the heart occurred in conjunction with an increase in haematocrit and the respiratory surface area of the gills, as well as an improved capacity of the fish to respond to a more severe acute hypoxia challenge. We also found an increase in the expression of the gene transcripts for hif-1αa and vegfaa at 24 h, 3 days and 8 days of hypoxia exposure, suggesting a rapid and consistent response. Our results suggest that, unlike normoxia-acclimated fish which demonstrate a decrease in cardiac output with acute hypoxia exposure, zebrafish acclimated to hypoxia maintain cardiac output when acutely exposed to hypoxia.

• Fluid flow and feeding performance in infant mammals: evaluating the impact of nipple design

  ABSTRACT

  Infant mammals must suckle in order to acquire food. Many factors, including the design of a nipple, impact suckling, and thus can alter feeding performance. For example, feeding on a bottle nipple that has ducts embedded in silicone requires infants to generate suction to acquire milk, whereas a hollow bottle nipple allows infants to express milk via nipple compression. Furthermore, the design of a nipple impacts milk flow, and likely changes the relationships between suction generation, tongue kinematics and milk flow. In this experiment, we designed two ducted bottle nipples with similar properties and flow rates but with different branching patterns (a nipple with multi-level branching ducts and a nipple with a single central channel), and compared feeding performance with a hollow, cisternic nipple. We also experimentally calculated milk flow using a venturimeter attached to the single ducted nipple, while synchronously recording high-speed biplanar videofluoroscopy and intraoral pressure generation in infant pigs, a validated animal model. We found no significant differences between the ducted nipple types, but infants showed greater suction generation, different tongue kinematics and smaller bolus sizes when feeding from the ducted nipples as compared with a hollow, cisternic nipple. We calculated milk flow and volume per suck using the venturimeter, and saw correlations between milk flow rate and both middle tongue translation and intraoral suction generation. Overall, these data demonstrate that nipple design has a profound impact on the relationship between infant feeding physiology and milk flow.

• Disruption of the sea turtle magnetic map sense by a magnetic pulse

  ABSTRACT

  Although some migratory animals can derive directional (compass) and positional (map) information from Earth's magnetic field, the underlying mechanisms of magnetic sensing have remained enigmatic. One hypothesis proposes that crystals of the mineral magnetite (Fe₃O₄) function in magnetoreception, a concept bolstered by findings that brief, strong magnetic pulses capable of reversing the magnetic dipole moment of magnetite affect magnetic orientation responses of several animals. Disentangling whether such pulses affected an animal's magnetic compass sense or magnetic map sense, however, has often been difficult. Here, we investigated the effect of a magnetic pulse on the magnetic map sense of loggerhead sea turtles (Caretta caretta) using an established conditioning assay that requires turtles to use magnetic map information but not their magnetic compass. We report that a magnetic pulse disrupted turtle responses, consistent with the interpretation that the magnetic map sense of turtles is based at least partly on magnetite-based magnetoreceptors.

• ECR Spotlight – Alayna Mackiewicz

  ECR Spotlight is a series of interviews with early-career authors from a selection of papers published in Journal of Experimental Biology and aims to promote not only the diversity of early-career researchers (ECRs) working in experimental biology but also the huge variety of animals and physiological systems that are essential for the ‘comparative’ approach. Alayna Mackiewicz is an author on ‘ Disruption of the sea turtle magnetic map sense by a magnetic pulse’, published in JEB. Alayna is a PhD student in the lab of Dr Kenneth Lohmann at University of North Carolina at Chapel Hill, USA, investigating the mechanisms and neural processing of sensory cues in animal behavior.