buoyancy
- In vivo measurement of lung volume in ringed seals: insights from biomedical imaging
Summary: CT imaging of living ringed seals suggests that lung volumes are smaller than those obtained postmortem, reveals that total lung capacity is overestimated by established allometric relationships, and affirms that body density and net vertical forces influence the cost of diving.
- Near-equal compressibility of liver oil and seawater minimises buoyancy changes in deep-sea sharks and chimaeras
Summary: Pressure change during vertical migrations of sharks has little effect on buoyancy because liver oil and seawater have almost equal compressibility. Temperature and salinity effects dominate, possibly influencing behaviour and swimming performance.
- Swim bladder morphology changes with female reproductive state in the mouth-brooding African cichlid Astatotilapia burtoni
Highlighted Article: Redistribution of gas between anterior and posterior chambers of a compartmentalized swim bladder allows mouth-brooding females to better regulate buoyancy and swimming posture during this extreme maternal care behavior.
- Physostomous channel catfish, Ictalurus punctatus, modify swimming mode and buoyancy based on flow conditions
Summary: Channel catfish adopted negative buoyancy in lentic environments, but maintained buoyancy closer to neutral in lotic environments to optimise their locomotion.
- Body density and diving gas volume of the northern bottlenose whale (Hyperoodon ampullatus)
Summary: Body density and diving gas volume, two important but poorly understood physiological characteristics of beaked whales, are revealed through analysis of hydrodynamic performance during glides.
- Does the physiology of chondrichthyan fishes constrain their distribution in the deep sea?
Summary: Chondrichthyan fishes (sharks, rays and chimaeras) are exceedingly rare or possibly absent at abyssal depths (>4000 m), unlike bony fishes. This Commentary discusses hypotheses implicating the unusual physiology of chondrichthyans as an explanation for their scarcity at great depths.
- Gas exchange and dive characteristics of the free-swimming backswimmer Anisops deanei
Highlighted Article: Exotic gas experiments and mathematical modelling show that backswimmers extend dive duration by extracting 20% of their O2 directly from the water.
- Mechanical challenges to freshwater residency in sharks and rays
Summary: The high negative buoyancy of elasmobranchs increases the cost of locomotion and may be responsible for the scarcity of sharks in fresh water.