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The effects of daily cyclic hypoxia on the ecophysiology of the Atlantic ditch shrimp, Palaemon varians

The effects of daily cyclic hypoxia on the ecophysiology of the Atlantic ditch shrimp, Palaemon varians
The effects of daily cyclic hypoxia on the ecophysiology of the Atlantic ditch shrimp, Palaemon varians
Oxygen partial pressure (pO2) is not always constant in aquatic environments and can vary on different timescales, from hours to weeks. In many coastal environments, such as estuaries, lagoons or marshes, pO2 level scan vary on a daily base, resulting in daily cyclic hypoxia. By monitoring temperature and pO2 in the Lymington salt marshes (UK), I was able to quantify diel and seasonal pO2 variability in this coastal habitat:diel oscillations in pO2 were measured in winter, spring and summer, and the greatest pO2 oscillations were recorded in summer, when pO2 could fluctuate from ~42 kPa to ~ 1 kPa every 12 hours, causing diel cyclichypoxia. Even if cyclic hypoxia is common in numerous coastal areas around the world and affects many species, this phenomenon is less studied in comparison to acute or chronic hypoxia. The aim of this thesis was to characterize the short-term effects and the long-term consequences of daily cyclic hypoxia on the physiology of an important decapod crustacean, Palaemon varians. This species was found in the Lymington salt marshes (UK) and, in the laboratory, was subjected to a cyclic hypoxic regime that mimicked conditions measured in the field during summer.
In the laboratory, a short 8-hour exposure to hypoxia (pO2 < critical oxygen pressure, pcrit) induced behavioural and metabolic changes and suppressed feeding and ammoniacal excretion. Long-term exposure to diel cyclic hypoxia induced changes in the transcriptome of the animals, prompted an acceleration of the moult cycle (validated at transcriptional and phenotypic level) and eventually resulted in morphological changes to the gills, which increased lamellar surface area. Further, long-term exposure to cyclic hypoxia impaired animal’s growth (in terms of body weight and length), reduced ammoniacal excretion and negatively influenced reproduction by reducing egg yolk content. Interestingly, long-term acclimation to cyclic hypoxia increased thermal tolerance and copper tolerance in comparison to control animals, probably as a consequence of the morphological changes to the gills induced by cyclic hypoxia. Overall, results underline that a short hypoxic exposure repeated daily was able to induce in P. varians alterations at multiple levels of biological organisation. In particular, the observed long-term consequences(i.e. growth reduction, reduced ammoniacal excretion and impaired reproduction) might have important ecological implications for the species and for its ecosystem.
University of Southampton
Peruzza, Luca
97dfdd24-f9e8-4d76-aee5-67bdd9b92541
Peruzza, Luca
97dfdd24-f9e8-4d76-aee5-67bdd9b92541
Hauton, Christopher
7706f6ba-4497-42b2-8c6d-00df81676331
Thatje, Sven
f1011fe3-1048-40c0-97c1-e93b796e6533

Peruzza, Luca (2017) The effects of daily cyclic hypoxia on the ecophysiology of the Atlantic ditch shrimp, Palaemon varians. University of Southampton, Doctoral Thesis, 199pp.

Record type: Thesis (Doctoral)

Abstract

Oxygen partial pressure (pO2) is not always constant in aquatic environments and can vary on different timescales, from hours to weeks. In many coastal environments, such as estuaries, lagoons or marshes, pO2 level scan vary on a daily base, resulting in daily cyclic hypoxia. By monitoring temperature and pO2 in the Lymington salt marshes (UK), I was able to quantify diel and seasonal pO2 variability in this coastal habitat:diel oscillations in pO2 were measured in winter, spring and summer, and the greatest pO2 oscillations were recorded in summer, when pO2 could fluctuate from ~42 kPa to ~ 1 kPa every 12 hours, causing diel cyclichypoxia. Even if cyclic hypoxia is common in numerous coastal areas around the world and affects many species, this phenomenon is less studied in comparison to acute or chronic hypoxia. The aim of this thesis was to characterize the short-term effects and the long-term consequences of daily cyclic hypoxia on the physiology of an important decapod crustacean, Palaemon varians. This species was found in the Lymington salt marshes (UK) and, in the laboratory, was subjected to a cyclic hypoxic regime that mimicked conditions measured in the field during summer.
In the laboratory, a short 8-hour exposure to hypoxia (pO2 < critical oxygen pressure, pcrit) induced behavioural and metabolic changes and suppressed feeding and ammoniacal excretion. Long-term exposure to diel cyclic hypoxia induced changes in the transcriptome of the animals, prompted an acceleration of the moult cycle (validated at transcriptional and phenotypic level) and eventually resulted in morphological changes to the gills, which increased lamellar surface area. Further, long-term exposure to cyclic hypoxia impaired animal’s growth (in terms of body weight and length), reduced ammoniacal excretion and negatively influenced reproduction by reducing egg yolk content. Interestingly, long-term acclimation to cyclic hypoxia increased thermal tolerance and copper tolerance in comparison to control animals, probably as a consequence of the morphological changes to the gills induced by cyclic hypoxia. Overall, results underline that a short hypoxic exposure repeated daily was able to induce in P. varians alterations at multiple levels of biological organisation. In particular, the observed long-term consequences(i.e. growth reduction, reduced ammoniacal excretion and impaired reproduction) might have important ecological implications for the species and for its ecosystem.

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Published date: November 2017

Identifiers

Local EPrints ID: 421109
URI: http://eprints.soton.ac.uk/id/eprint/421109
PURE UUID: 32614bdc-ee6a-4f61-8c57-2df68635de00
ORCID for Christopher Hauton: ORCID iD orcid.org/0000-0002-2313-4226

Catalogue record

Date deposited: 22 May 2018 16:30
Last modified: 09 May 2019 04:01

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Contributors

Author: Luca Peruzza
Thesis advisor: Christopher Hauton ORCID iD
Thesis advisor: Sven Thatje

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