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First published online November 28, 2008
Journal of Experimental Biology 211, 3790-3799 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.018721
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Haemoglobin as a buoyancy regulator and oxygen supply in the backswimmer (Notonectidae, Anisops)

Philip G. D. Matthews* and Roger S. Seymour

Ecology and Evolutionary Biology, School of Earth and Environmental Sciences, Darling Building, University of Adelaide, Adelaide, SA 5005, Australia

* Author for correspondence (e-mail: philip.matthews{at}adelaide.edu.au)

Accepted 11 September 2008

Unlike all other diving insects, backswimmers of the genus Anisops can exploit the pelagic zone by temporarily achieving near-neutral buoyancy during the course of a dive. They begin a dive positively buoyant due to the large volume of air carried in their ventral air-stores, but rapidly enter a protracted period of near-neutral buoyancy before becoming negatively buoyant. This dive profile is due to haemoglobin found in large tracheated cells in the abdomen. Fibre optic oxygen probes placed in the air-stores of submerged bugs revealed that oxygen partial pressure (PO2) dropped in a sigmoid curve, where a linear decline preceded a plateau between 5.1 and 2.0 kPa, before a final drop. Buoyancy measurements made by attaching backswimmers to a sensitive electronic balance showed the same three phases. Inactivating the haemoglobin by fumigating backswimmers with 15% CO eliminated both buoyancy and PO2 plateaus. Oxygen unloaded from the haemoglobin stabilises the air-store during the neutrally buoyant phase after a decrease in volume of between 16% and 19%. Using measurements of air-store PO2 and volume, it was calculated that during a dive the haemoglobin and air-store contribute 0.25 and 0.26 µl of oxygen, respectively.

Key words: buoyancy, haemoglobin, insect, respiration


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Related articles in JEB:

BACKSWIMMERS REGULATE BUOYANCY WITH HAEMOGLOBIN
Kathryn Phillips
JEB 2008 211: i. [Full Text]  



This article has been cited by other articles:


Home page
 J. Exp. Biol.Home page
K. Phillips
BACKSWIMMERS REGULATE BUOYANCY WITH HAEMOGLOBIN
J. Exp. Biol., December 15, 2008; 211(24): i - ii.
[Full Text] [PDF]


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