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Physiological responses to different environmental and culture conditions during ontogeny of the spiny lobster, Sagmariasus verreauxi

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Jensen, MA (2012) Physiological responses to different environmental and culture conditions during ontogeny of the spiny lobster, Sagmariasus verreauxi. PhD thesis, University of Tasmania.

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Abstract

Very little is known about the metabolic and biochemical physiology of spiny
lobsters as they develop. An improved understanding of the physiological responses
of spiny lobsters to different environmental and culture conditions during ontogeny is
essential for gaining a better understanding of environmental influences on wild
populations and for their successful propagation. This study addresses important gaps
in our knowledge by examining stage-specific changes in metabolic rates, ammonia-N
excretion rates, thermal tolerance thresholds, and whole body and haemolymph
biochemistry of larval and juvenile Sagmariasus (Jasus) verreauxi in order to observe
these physiological parameters through ontogeny. Automated intermittent flowthrough
respirometry was used to measure the aerobic metabolism of larval and
juvenile lobsters accurately. Whole body biochemical analysis was used to examine
energy storage and utilisation of phyllosoma. Haemolymph biochemistry was used to
determine the thermal tolerance thresholds of juvenile lobsters.
The effect of temperature change on the final instar (instar 17) was examined
to assess whether it could serve as a cue for metamorphosis and it was found that
temperature affected routine metabolic rate (Rr), but did not alter instar duration, and
therefore is not a cue for metamorphosis. Fewer phyllosoma, however, completed
metamorphosis and progressed to the puerulus stage at sub-optimal warm
temperatures compared to cooler temperature. The effect of culture density was
examined from hatch to pueruli. High culture density reduced growth (dry mass) and
development (moult increment) of phyllosoma. There was a shift in metabolism via
energy storage and utilisation of instar 17 phyllosoma in preparation for the
morphological changes associated with metamorphosis. There was also an iv
accumulation of lipid reserves during larval development that fuelled metamorphosis
and the non-feeding puerulus stage.
The aerobic scope of juvenile lobsters was determined through chasing
lobsters by hand until the lobster was exhausted and did not respond to further stimuli
along with the effects of handling, anaesthesia, and activity on the oxygen
consumption rate (ṀO2) and ammonia-N excretion rate. Handling caused a relatively
minor increase in ṀO2 and anaesthetics reduced activity of lobsters, but did not
reduce ṀO2 or recovery periods from force feeding or handling. S. verreauxi
juveniles have a narrow aerobic scope. Increased ṀO2 from anaesthesia and activity
uses a large proportion of energy within the metabolic scope that could otherwise be
utilised for other physiological functions. Thermal tolerance thresholds were
examined in different sized juvenile lobsters. Sudden changes in haemolymph O2
concentrations with water temperature indicated large lobsters have a higher optimum
water temperature than small lobsters. Maximum attainable rates of standard
metabolism indicated the upper critical temperature (Tc) for juvenile S. verreauxi,
characterised by the onset of anaerobic metabolism. Juveniles utilised lipid as an
energy substrate at optimal temperatures, but shifted towards protein catabolism at
temperatures above their thermal tolerance range.
This research revealed the long larval phase of S. verreauxi is essential for
accumulating lipid reserves to fuel later larval stages and provided a more complete
picture of the environmental and culture requirements of spiny lobsters during
ontogeny, particularly for the rarely studied late phyllosoma stages. It also
established that induced stress uses a large proportion of the aerobic scope in juvenile
lobsters, which limits their ability to perform aerobically and deal with additional
physiological challenges. The thermal tolerance of S. verreauxi juveniles identified the potential to expand their geographic distribution, which may have a large impact
on benthic community structures and dynamics through competition for resources
with existing lobster populations and other animals within the ecosystem. This may
also impact local economies, particularly valuable local southern rock lobster
fisheries.

Item Type: Thesis (PhD)
Keywords: Metabolism, biochemistry, metamorphosis, density, stress, thermal tolerance, lobster, ontogeny
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Date Deposited: 17 Aug 2012 04:43
Last Modified: 15 Sep 2017 01:06
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