Johan F. Steffensen

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Energy expenditure during flight in animals can best be understood and quantified when both theoretical and empirical approaches are used concurrently. This paper examines one of four methods that we have used to estimate the cost of flight in a neotropical nectar-feeding bat Glossophaga soricina (Phyllostomidae), namely the use of kinematic and(More)
European eels were exposed for 6 weeks to water CO(2) partial pressures (P(CO)(2)) from ambient (approx. 0.8 mmHg), through 15+/-1 mmHg and 30+/-1 mmHg to 45+/-1 mmHg in water with a total hardness of 240 mg l(-1) as CaCO(3), pH 8.2, at 23+/-1 degrees C. Arterial plasma P(CO)(2) equilibrated at approximately 2 mmHg above water P(CO)(2) in all groups, and(More)
Swimming respirometry was employed to compare inactive metabolic rate (Rr), maximum metabolic rate (Rmax), resultant aerobic scope and maximum sustainable (critical) swimming speed (Ucrit), in growth hormone transgenic (GHT) and wild-type (W) tilapia Oreochromis sp. hybrids. Although the Rr of GHT tilapia was significantly (58%) higher than their W(More)
*School of Biosciences, University of Birmingham, Birmingham, B15 2TT, U.K., ‡Marine Biological Laboratory, University of Copenhagen, Strandpromenaden 5, DK-3000, Helsingør, Denmark, §College of Natural Sciences, Hawaii Pacific University, Kaneohe, HI 96744, U.S.A., {School of Biological Sciences, University of Wales Bangor, Gwynedd, LL57 2UW, U.K. and(More)
The volume of the primary (PCS) and secondary (SCS) circulatory system in the Atlantic cod Gadus morhua was determined using a modified dye dilution technique. Cod (N=10) were chronically cannulated in the second afferent branchial artery with PE-50 tubing. Evans Blue dye was bound to harvested fish plasma at a concentration of 1 mg dye ml(-1) plasma, and(More)
Teleost fishes and mammalian lineages diverged 400 million years ago, and environmental requirements (water versus air) have resulted in marked differences in cardiovascular function between fish and mammals. Suggestions that the fish secondary vascular system (SVS) could be used as a model for the mammalian lymphatic system should be taken with caution.(More)
The present study was undertaken to examine cardiac responses to some of the temperature challenges that eels encounter in their natural environment. The contractile properties of ventricular muscle was studied on electrically paced tissue strips after long term acclimation at 0 °C, 10 °C, or 20 °C, and following acute ± 10 °C temperature changes. The(More)
The vascular system in fish is divided into two components, the blood circulation and a secondary circulatory system, which is a vessel system referred to by earlier authors as ‘lymphatics’. Also, Wardle (1971) used the latter term for his description of the secondary system. However, true lymphatics are defined solely anatomically (and not functionally) as(More)
The average rate of swimming speed and the physiological status or stress of individual Atlantic cod Gadus morhua was monitored in response to short-term acute (STA) hypoxia (i.e. partial pressure of oxygen, PO2 , reduced from 20 9 to 4 3 kPa within 1 h at 10° C). The STA hypoxic response of Atlantic cod was associated with a large primary increase (þ29%)(More)
1. Sharksuckers use active branchial ventilation when swimming or at rest in stationary water. When attached to a moving object or when placed in a water current, they shift to ram gill ventilation as water velocity exceeds a certain threshold. 2. Water velocities required for the transition from active to ram gill ventilation were from 10-50 cm s-1,(More)