Physiological ecology
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  Temperature, desiccation, & other stresses
  Topics on the physiological ecology of sea anemones include temperature, desiccation, & other stresses considered here and METABOLISM and MYCOSPORINE-LIKE AMINO ACIDS located elsewhere.
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Research study 1

photos of bumps or verrucae on the skin of a sea anemone Anthopleura elegantissimaphotograph of sea anemone Anthopleura elegantissima with shell bits stuck to columnSea anemones Anthopleura elegantissima attach gravel and shell bits to their body walls.  The adaptive significance of this is uncertain, but suggestions include protection from predation (physical as well as camouflage), harmful UV radiation, and water loss.  An investigation at the Bodega Marine Laboratory, California reveals, first, that the gravel bits are held on epithelial bumps on the body column, known as verrucae (see photos). Pores on many of the verrucae communicate via canals directly with the internal gastrovascular cavity, and may function to allow water to escape in fine jets during rapid contraction (see Right-hand photo on Right).  Numerous glands on the epidermis of the bumps secrete an adhesive mucus, and this appears to be the means by which the gravel bits are attached.  Comparison of sizes of attached gravel on anemones with sizes of gravel available in the substratum and being moved about by wave action, reveals a strong preference for particles of about 1.5mm diameter. Field experiments involving anemones with and without gravel coatings exposed to various wind and temperature conditions at a high intertidal level for 6h show that almost twice as many individuals survive with gravel coatings than ones without.  Laboratory experiments to assess the effects of gravel coatings on evaporative water loss show that individuals with gravel lose water at about 40% of rates in ones without gravel. Conditions of wind speed and air temperature are the same for both groups.  However, through estimates of exposed surface area of epithelia with and without gravel, the authors conclude that a simple reduction in surface layer cannot account for the magnitude of reduction in water loss; rather, it appears that the gravel must provide an unstirred boundary layer. Hart & Crowe 1977 Trans Amer Microsc Soc 96: 28. Photograph below courtesy Dave Cowles, Walla Walla University, Washington

photographs of Anthopleura elegantissima showing bumpy epitheliumNOTE  see PHYSIOLOGY: MYCOSPORINE-LIKE AMINO ACIDS elsewhere in this part of the ODYSSEY

NOTE  lit. “warts” L.


Anthopleura elegantissima showing verrucae on the
epithelium of the body column 1X
The large bumps on this individual are about 5mm diameter,
much larger than the ones featured in the above B&W photo


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Research study 2


An indicator of health and well-being in marine invertebrates, as well as all other animals, is adenylate energy charge (AEC), or the ratio of adenosine triphosphate (ATP) to adenosine diphosphate (ADP).  Whether AEC can be reliably used as an indicator of stress, such as that caused by desiccation, is the subject of a study in California using the sea anemone Anthopleura elegantissima. In laboratory experiments at Stanford University researchers subject test anemones to a variety of stressors associated with intertidal life, including desiccation and temperature extremes.  Results show that while adenylates overall significantly decrease in response to desiccation, column contraction, and starvation, their ratios or AECs exhibit no significant variation.  The authors conclude that AEC alone is not a useful index of stress in A. elegantissima. Smith & Watt 1994 Mol Mar Biol Biotech 3: 261.

NOTE  a high level of ATP in relation to ADP signifies cell viability and proliferation, while the convere siginifies cell necrosis and generally poor health.  AEC can be used as a static indicator of growth potential for invertebrates in the mariculture industry

Research study 3

histogram showing heat-shock protein expression in sea anemones Anthopleura elegantissima in response to varying degrees of emersionhistogram showing concentrations of heat-shock protein HSP70 in body parts of a sea anemone Anthopleura elegantissimaIntertidal marine invertebrates such as sea anemones are subject to a variety of physical stresses associated with tidal exposure, including temperature extremes, UV radiation, and desiccation.  A readily quantifiable measure of these stresses is the extent of expression of heat-shock proteins (HSPs). Up to the time of this publication, little was known of the natural in situ expression of HSPs and, in response to this lack, researchers at the Bodega Marine Laboratory, California measure levels of HSP70 in the anemone Anthopleura elegantissima under different environmental conditions.  An advantage of selecting this species is that genetically identical clones can be compared under different natural circumstances, for example, intertidal height, time of emersion, degree of insolation, and so forth.  Results show, as predicted, that higher intertidal position, longer emersion, and greater exposure to the sun (see graph upper Right) lead to significantly greater HSP70 expression.  Most of the HSPs are expressed in the tentacles, rather than the body column or other areas (see histogram on Left). The authors note that in addition to elevated levels of heat-shock proteins, low-intertidal A. elegantissima are able to alleviate effects of physical stress associated with emersion through shrinking of polyps, secretion of mucus, covering with sand, living in close proximity to conspecific clone-mates, and possessing UV-absorbing molecules known as mycosporine-like amino acids (MAAs). Snyder & Rossi 2004 Scientia Marina 68: 155.

NOTE  more on HSPs and their functions can be found in the ODYSSEY at: ABALONES & RELATIVES: PHYSIOLOGICAL ECOLOGY: HEAT-SHOCK PROTEINS; LEARN ABOUT MUSSELS: LIFE IN THE INTERTIDAL ZONE: HEAT-SHOCK PROTEINS.  HSPs are categorised according to their molecular mass in kDa; hence, HSP70, and so on

NOTE an account of MAAs in A. elegantissima can be found at: PHYSIOLOGICAL ECOLOGY: MYCOSPORINE-LIKE AMINO ACIDS

Research study 4
  photograph of normal and bleached sea anemones Anthopleura elegantissimaImportant stressors leading to bleaching in symbiont-containing cnidarians, such as sea anemones and corals, are elevated temperature and UV irradiation. Previous research has not clarified whether the stressor mainly affect the symbionts or the hosts, but research at Oregon State University in Corvallis on aggregating anemones Anthopleura elegantissima shows that physiological changes in the hosts themselves are certainly involved. The researchers use a transcriptomic approach, monitoring changes in cDNA levels in anemone tissues immediately following temperature (20oC or +8oC above normal) and UVB (368nm) stresses over 24h periods. Results show that of 86 features sequenced, 27 are similarly up- and down-regulated in both stress conditions (10 up and 17 down, in all cases more than 20-fold change over controls). These include genes that are widely involved in the host’s cellular regulation, such as ones controlling cytoskeleton genesis and organisation, protein synthesis, cell growth and death, and cell-membrane transport mechanisms. The study is the first of its kind to investigate molecular effects on cellular pathways involved with bleaching. Richier et al. 2008 Comp Biochem Physiol D 3: 283. Photograph courtesy Virginia Weis, Oregon State University.
Research study 5

graphs comparing body temperatures of sea anemones Anthopleura elegantissim isolated and aggregatedphotograph of aggregating anemones Anthopleura elegantissima semi-aggregatedElevated body temperature in an aggregating anemone Anthopleura elegantissima affects not just the individual’s own metabolic performance, but also that of its complement of symbionts.  An interesting study by researchers at Shannon Point Marine Center, Washington investigates whether aggregations act to mitigate temperature effects and whether size of aggregations might change with tidal height.  Results from laboratory wind-tunnel tests with emersed anemones show, as expected, that both larger body size and aggregating behaviour mitigate effects of temperature (see graphs on Left).  Note in the upper graph that a few of the largest-sized individuals stay nearly 6oC below ambient air temperature during the 9h period of monitoring.  In the lower graph, even though all test individuals in the aggregation are small, temperature rise is slightly less than for anemones in isolation, and overall results are much less variable.  Readings from individuals wrapped in plastic to minimize water loss suggests that evaporative cooling in normal animals in the field may be significant. In field aggregations after almost 9h emersion on a warm day in July, individuals in the centre are a few degrees cooler than ones on the edge.  In the warmest month of summer (July) aggregations are significantly larger at higher tidal levels than at lower levels, suggesting a behavioral response to temperature and related desiccation effects.  Given that this anemone species hosts species of symbionts with differing thermal tolerances, behavioral amelioration of temperature extremes in this way may be adaptive in ways not previously predicted.  Bingham et al. 2011 Invert Biol 130 (4): 291.s

NOTE  temperatures are recorded using submersible thermocouples inserted via the mouth into the gastrovascular cavity

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