Physiology & physiological ecology
  Topics considered here include metabolic demands in larvae, desiccation, temperature effects, and ocean acidification. Effects of intertidal temperatures on HEAT-SHOCK PROTEINS in turban snails are considered in another section.
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Metabolic demands in larvae

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Research study 1

graph showing mass of body components during larval development in abalone Haliotis rufescensAn abalone larva is non-feeding and the energy it contains must last it through metamorphosis to a feeding juvenile stage.  But are veliger larvae truly in energy balance? That is, does their store of yolk fully meet their energy needs?  Studies on the energetics and growth of veliger larvae of Haliotis rufescens in southern California attempt to answer this.  First, the larvae actually increase in dry organic mass during the first 2d after hatching, and dry mass of ash increases steadily during the 7d of larval life (see graph on Left). Second, the decrease in organic mass (representing metabolism histogram showing uptake rates by larval abalone Haliotis rufescens of different amino acidsof energy stores) from hatching to metamorphosis only accounts for about 48% on average of the total energy required during this period as measured by oxygen consumption.  The authors suggest that the larvae are utilising nutrients obtained as DOM, specifically amino acids, to make up this deficiency.  Based on estimates of amounts of amino acids in the total pool of DOM in seawater and on measured rates of uptake of amino acids by abalone trochophores and veligers (see uptake rates in graph on Right), the authors calculate that an uptake of only 4% of the total amino-acid pool would satisfy 100% of the missing energy. The authors conclude that these lecithotrophic larvae are not energetically independent of their environment.  Jaeckle & Manahan 1989 Biol Bull 177: 237; Jaeckle & Manahan 1989 Mar Biol 103: 87.

NOTE data obtained in laboratory culture at 16-17oC and presented for egg (0d of age), trochophore larva (1d), early veliger larva (2d), and for several later veliger stages up to the metamorphically competent one (7d)

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Research study 2

photograph of a post-metamorphic juvenile abalone Haliotis rufescens courtesy Shilling et al. 1996 Biol Bull 191: 402In a later paper researchers investigate the energy demands of metamorphosis in 6-9d-old red abalone Haliotis rufescens and determine that the proportion of total metabolic demand supplied from aerobically catabolised biomass is less than 40%.  Thus, metamorphosing veligers have a theoretical shortfall of 60%. Based on measured rates of transport of dissolved alanine from seawater, the authors determine that the energy shortfall could once again be met by uptake of DOM from the environment.  In fact, their data show that the cumulative transport of DOM during development to the early juvenile stage could supply an amount of energy equivalent to the entire maternal endowment of energy reserves in the form of yolk to the egg.  Shilling et al. 1996 Biol Bull 191: 402.

NOTE dissolved organic matter, equated here to amino acids in the surrounding seawater, but in general terms also including fatty acids and perhaps some sugars

Post-metamorphic juvenile Haliotis already feeding on epiphytes on coralline algae
(0.8mm shell length). The red arrow indicates the larval shell; yellow arrow, the juvenile shell.
Photo courtesy Sabine Daume, from Heasman & Savva 2007 Manual for intensive
hatchery production of abalone
Fisheries Res & Dev Corp, Australian Gov

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Research study 1

  By tagging individual Chlorostoma funebralis and monitoring their movements during daily tidal cycles, researchers Hopkins Marine Station, Pacific Grove, California report that populations move to the tops of rocks during high tides at night, but not during high tides in the daytime.  Even light from a full moon appears to inhibit the movement.  The significance of the behaviour is not known, but may relate to temperature effects on feeding and/or reproduction.  Wara & Wright 1964 Veliger 6(Suppl): 30.

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Research study 2


Black turban-snails Chlorostoma funebralis often aggregate during periods of low tide.  Is this for defense against predators or for protection against desiccation?  The last is investigated at Bodega Marine Laboratory, California by measuring the photogaph of a cluster of black turban snails Chlorostoma funebralissalt concentration of water1 held within the closed shell during low tide periods in both solitary and aggregated individuals.  We know that this species cannot regulate the salt concentration of internal fluids, so this water should be a direct reflection of the internal osmolarity2

The histogram indicates a trend of higher values in animals exposed to open air as compared with animals in protected sites (such as within crevices or beneath algae). In both exposed and protected microhabitats there is no significant difference3 between solitary or aggregated individuals. The authors conclude that microhabitat effects are more important than being solitary or aggregated.  Marchetti & Geller 1987 Veliger 30: 127.

NOTE1  also known as “extra-corporeal” water (lit. “outside body” L.). 

NOTE2 salt concentration is expressed here as “osmolarity”, although the two units are not quite the same, and defined as mOsM per liter.  Full-strength seawater is around 1000 mOsM per liter

NOTE3 internal body temperatures are about 4oC lower in aggregated individuals than in solitary ones

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Temperature effects

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Research study 1

map showing collecting sites for black turban-shells Chlorostoma funebralis for use in study on temperature effectson activityTemperature should affect locomotion, food-consumption, and gut-passage rates in snails as predicted from Q10 principle and temperatures characteristic of the snails’ geographic distributions.  This is examined in 3 Chlorostoma species with distinct thermal distributions: C. brunnea (cold water), C. aureotincta (warm water), and C. funebralis (both warm and cold water).  Rates for each species are tested at 4 temperatures: 11, 15, 19, and 23oC. 

Results for C. aureotincta, the warm-water species, show that activity and consumption rates increased with increasing temperature.  For C. brunnea, the cold-water species, rates are lowest at 11oC and highest at 19oC, a temperature rarely experienced in its natural habitat.  For cold-water C. funebralis, overall activity is highest at 15oC and food-consumption is highest at 23oC.  For warm-water C. funebralis, activity and food-consumption is lowest at 11oC.  Gut-passage times are little affected by temperature in these species.  Overall, and as might be expected, activity and food-consumption in the more broadly distributed C. funebralis are less affected by temperature than those of the 2more narrowly distributed species.  The authors discuss their data in the context of temperature effects on distributions in the various species. Yee & Murray 2004 Mar Biol 145: 895.

NOTE  rates are tested after acclimation periods of 10d in the laboratory

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Research study 2

histogram comparing thermal-tolerance ranges of snails Chlorostoma spp.Three commonly occurring west-coast Chlorostoma species live at different tidal heights on the shore of Pacific Grove, California.  Thus, funebralis inhabits the low- to mid-intertidal zone, while brunnea and montereyi live in low intertidal or subtidal regions.  What are the thermal limits of heart function in these snails and how do these relate to their vertical zonation?  This is investigated in 3 populations of Chlorostoma at Hopkins Marine Station, California. 

Results show that the thermal range of field-acclimatised C. funebralis is greater than those of the 2 lower-occurring species. Thus, ABT and FLThot are higher (see histogram on Left), and FLTcold is lower (data not shown).  If snails of each species are acclimated to lower (14oC) and higher (22oC) temperatures, all 3 species show increases in ABT and FLThot, with the largest changes occurring in brunnea and montereyi.  The authors note that while funebralis is more eurythermal than its co-occurring congeners, it may sometimes encounter body temperatures that impair or even stop heart function, that is, exceed ABT.  Stenseng et al. 2005 Biol Bull 208: 138.graph showing how the Arrhenius Break Temperature of ABT is determined for heart-beat response to rising temperature in snails Chlorostoma funebralis

NOTE  the authors use 3 indices to provide an estimate of the thermal range within which Chlorostoma’s heart function is maintained: 1) temperature at which heart rate initially decreases rapidly during heating, also known as the Arrhenius break temperature or ABT; see graph on Right), 2) temperature at which the heart ceases to beat during heating, termed the flatline temperature or FLThot, and 3) temperature at which the heart ceases to beat during cooling, termed FLTcold

NOTE  heart rate is monitored using an impedance converter with electrodes inserted via 2 1mm diameter holes drilled into the shell close to the heart and glued in place with cyanoacrylate adhesive

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Research study 3

histogram showing effects on gonadal indices in red and green abalone of various combinations of temperature, and food quality and quantityphotographs of Haliotis rufescens & H. fulgens, courtesy Kevin Lee, Fullerton, CaliforniaCan predicted climate-change effects be simulated in the laboratory? This approach has been growing in popularity1 and is examined here for red abalone Haliotis rufescens and green abalone H. fulgens at the Scripps Institution of Oceanography in La Jolla, California using treatments that mimic El Niño and La Niña conditions in the California current.  Haliotis rufescens is a cool water-inhabiting species, while H. fulgens prefers warm water. The researchers simultaneously test the possible synergistic effects of temperature, and food quality and quantity on survivorship, growth, and reproduction in the 2 species, with special emphasis on exacerbation of disease2 susceptibility.  The design of the experiments is complex and only a brief summary of results is presented here.  Basically 7 individuals of each species are housed in each of 9 floating plastic-mesh cages in larger tanks maintained at 3 temperatures.  The 9 cages represent a 3 x 3 combination of food3 quality and quantity.  Over a 50-wk treatment period the test abalone are measured periodically for changes in shell length, live mass, and gonadal maturation.  At the end of the experiment, 3 individuals from each treatment are assessed for gonad index, done by cross-sectional measurement, and intensity of withering syndrome disease.  Results for H. rufescens show that warm temperatures increase the onset of withering disease, and halt growth and reproduction (see histograms for effects on gonadal indices).  In comparison, temperature has little effect on these parameters in H. fulgens, with growth and reproduction being most influenced by food quantity.  Overall, then, the cool-water red abalone suffer more in warm water than do green abalone.  The authors conclude that ocean warming will have significant adverse effects on California abalone populations. Vilchis et al. 2005 Ecol Appl 15: 469. Photograph of H. rufescens courtesy Kevin Lee, Fullerton, California diverKevin.

NOTE1  a later and similar study also compares health and survival of H. rufescens in laboratory simulations of El Niño and La Niña conditions.  It differs from the earlier study in using wild abalone from San Miguel Island, Channel Islands, California, an area characterised by generally cooler water temperatures throughout the year, rather than cultured abalone.  Results are similar to the earlier study, with higher temperatures leading to elevated expression of withering syndrome (now identified as Candidatus Xenohaliotis californiensis).  Based on their results the authors predict that strong El Niño events will result in significant mortality of red abalone at San Miguel Island.  Moore et al. 2011 J Aquat Anim Health 23: 78.

NOTE2  the disease, withering syndrome, is a Rickettsiales-like prokaryote found in the gastroinstestinal epithelia.  The disease is invariably fatal.  In order to eliminate it from experimental animals (purchased from hatcheries), all are treated with antibiotics over 7wk prior to the start of the experiment. For more on the disease see Friedman et al. 2002 J Shellf Res 21: 817

NOTE3  food is kelp Macrocystis pyrifera collected at different vertical levels in the kelp bed, and treated or not for 72h in nitrogen-enriched seawater to make high-, medium-, and low-quality diets.  The 3 diets vary from about 1.5-3.5% dry mass of nitrogen.  The 3 quantities are high (ad libitum), medium (30% of ad labitum), and low (10% of ad labitum). Temperatures vary over the time span of the experiment, but are maintained at about 2oC separation for the 3 treatments.  Each combination is replicated 3 times

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Research study 3.1

Some marine invertebrates, such as sea mussels Mytilus californianus, can maintain membrane stability over a range of potentially debilitating high environmental temperatures, a process known as homeoviscous adaptation. Whether this happens in black turban-snails Chlorostoma funebralis is investigated by researchers at Hopkins Marine Station, California, who acclimate individuals at 3 temperatures from 5-25oC for 4wk, then test gill/mantle-tissue homogenates for viscosity using fluorescent-anisotropic techniques (see graph). Note in the graph that no obvious homeoviscous compensation occurs at higher experimental temperatures indicating a lack of compensatory effects of acclimation. Additionally, winkles Littorina keenae sampled in the field at the beginning and end of a hot mid-day low tide in late spring similarly show no significant effect of temperature (+24oC over the 8h period) on membrane viscosity, nor do tissue samples from another 10-or so gastropod species collected from the field at Cape Arago, Oregon show effects of laboratory incubation temperatures from 10-30oC graph showing lack of homeoviscous adaptation in tissues of black turban-snail Chlorostoma funebralison membrane viscosity (data not shown). Demonstration of lack of homeoviscous adaptation in these snails, although unexpected, adds to our knowledge of this interesting area of research. Rais et al. 2010 Mar Biol 157: 2407.

NOTE lower temperatures cause the packing order of membrane phospholipids to increase, thus lowering membrane “fluidity”, while higher temperatures cause the packing order to decrease. Under prolonged exposure to potentially membrane-disrupting temperatures, some organisms can adaptively modify the phospholipid composition or other aspects of membrane structure to maintain proper membrane function

NOTE the authors also include winkles and other snails in the study and a mention of corroborative field evidence for them is included above

Without going into details, this graph shows an absence of homeoviscous adaptation in
C. funebralis tissue preparations with increasing temperature (after 4wk acclimation
to the 3 experimental temperatures). Were this adaptation to be present, the slope of the
line would tend to flatten, indicating decreasing viscosity at higher treatment temperatures

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Research study 4

photograph of Chlorostoma funebralis clusterA study by researchers at Hopkins Marine Station, California on temperature preferences of the trochid snail Chlorostoma funebralis has an interesting premise and even more interesting results.  The premise, based mainly on data for terrestrial ectotherms such as lizards and insects, is that an organism when given a choice prefers to have a body temperature just below its physiological optimum, that is, just below the temperature at which bodily functions work most effectively and efficiently.  Results, however, from experiments in which C. funebralis snails are allowed to roam along a temperature gradient until they stop, indicate that their preferred temperature is actually below that of optimal physiological performance, not by a minor amount, but by a whopping 16oC.  The preferred temperature of 5oC is actually close to the species’ lower thermal limit of 3oC.  The authors’ explanation for this is that it will tend to guide snails into cooler, shadier habitats.  That this may negatively affect fitness by reducing growth and reproductive output is therefore secondary to its value in reducing risk of exposure to temperature stress, and possibly to predators, in more exposed habitats. Tepler et al. 2011 Biol Bull 220: 107. 

NOTE  the authors estimate this physiological optimum temperature to be intermediate between the upper and lower temperatures at which death occurs by heart failure (39 and 3oC, respectively), or about 21oC

Trochid snails Chlorostoma funebralis exhibiting
typical intertidal clustering behaviour 0.6X

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Research study 5

map of California showing sampling locations for study on heat stresses in Chlorostoma funebralisThe snail Chlorostoma funebralis has a moderately dispersing veliger larva (less than a week) and is broadly distributed from British Columbia to Mexico.  Genetic data suggest extensive gene flow across a broad range of populations, with the corollary that physiological adaptation to temperature stresses in different localities would be unexpected.  Whether this is so or not is tested by researchers at Scripps Institution of Oceanography, San Diego who compare responses to heat stress in northern and southern populations of Chlorostoma in California separated by about 700km (see map). Results show that in two of the tests, southern populations have a significantly greater tolerance to heat stress than northern populations, suggesting the presence of “physiological races” in population structure. The findings support a growing body of evidence that, despite planktonic modes of gene dispersal, populations of some marine invertebrates may not be as genetically connected as presumed.  Gleason & Burton 2013 J Exp Mar Biol Ecol 448: 360.

NOTE  these include mortality during and after application of heat stress, and rate of recovery 

NOTE however, while earlier analyses on the 2 populations revealed no evidence for genetic differentiation, later outlier tests disclose 34 loci that do show clear differentiation between the northern and southern populations. Three of these outlier loci are thought to be involved in stress-granule formation, a response associated with environmental heat stress. Gleason & Burton 2016 Mol Ecol 25: 3557.


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  Ocean acidification
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Research study 1

histogram comparine effects of different carbon-dioxide concentrations on larval development in northern abalones Haliotis kamtschatkanaphotograph of juvenile northern abalone Haliotis kamtschatkanaA study at the Bamfield Marine Sciences Centre, British Columbia investigates pH effects on growth of different life stages of northern abalone Haliotis kamtschatkana.  Larvae are reared to juvenile stage over an 8d period in pH conditions of 8.3, 8.1, and 7.8 at a temperature of 7oC.   Results show a significant negative effect on growth and survival, and on shell integrity.  In fact, shells are about 40% abnormal in the 800ppm treatment and either abnormal or completely absent in the 1800ppm treatment (see histogram).  Although larval survival is decreased by only about 40% in the elevated CO2-treatments over the control treatment, the authors comment that the malformed state of the larvae may, in nature, leave them more susceptible to planktonic predation.   Overall, impending acidification of coastal seawaters may have serious effects on health of populations of this species already threatened by reduced larval recruitment. Crim et al. 2011 J Exp Mar Biol Ecol 400: 272.

NOTE  these pHs are obtained by treating seawater with levels of 400, 800, and 1800ppm CO2.  The levels represent, in order, present conditions, predicted future conditions at year 2100, and near maximal conditions (we hope) predicted for year 2300

NOTE  although couched in terms of long-scale effects of climate change, like most other papers on a similar topic, this one really just deals with acute effects of lower pHs on early development. Quite understandably, it cannot take into account possible adaptive evolution that may occur over the many generations between now and year 2100 or year 2300.  Other researchers working with transcriptomic effects in purple urchins Strongylocentrotus purpuratus in upwelling areas of California appear to be on a potentially more informative line of research

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Research study 2

graphs showing effect of predatory scent of seastars Pisaster ochraceus on escape behaviour of black-turban snails Tegula funebralis in different pH seawatersphotograph of black-turban snails Tegula funebralis in a tidepool with predatory seastar Pisaster ochraceusA comparable study done by researchers at Bodega Marine Laboratory, California tests for effects of low pH on escape behaviour of black-turban snails Tegula funebralis reacting to water-borne scent of a major predator, ochre stars Pisaster ochraceus. The study population of snails in the Bodega Marine Reserve live in tidepools that are isolated from the ocean during normal summer/autumn low tides for approximate 5h periods. During these periods pH changes in the pools, especially overnight when organisms respire, leading to rising CO2 levels and concomitant falling pH. The experiments involve exposing snails to both constant and fluctuating pH conditions, at levels and over durations that mimic natural variability in the tidepools inhabited by the snails. In the first experiment, using “constant pH1”, snails (two1 in each pH treatment) are maintained at 16 pH levels3 ranging from 6.3-8.0 for 5d periods. After 5d one snail from each pair is exposed to predator-conditioned seawater in a small arena, while the other snail from each pair is treated with control seawater. For 28min post-treatment each snail is periodically monitored for level/intensity of 3 escape-related behaviours4: total distance crawled, path shape, and time out of water. The first is a measure of escape intensity; the second, a quantification of flight vs. random wandering; and the third, an assessment of “full-blown” escape response where the snails actually seek refuge by crawling out of water. In the “fluctuating pH” experiment, a similar protocol is used, but with pHs being alternated every second day (8 levels ranging from 6.2-7.6) better to simulate natural tidepool conditions. Results for both types of experiments show non-significant responses for the 1st and 2nd behaviours, but highly significant responses for the 3rd behaviour (see graphs, shown only for the 3rd behaviour). Note in the “constant pH” experiment (graph above) that snails in low pH treatments (i.e., less basic) are less responsive to predator scent than ones in high pH treatments (closer to normal pH). The effect is even more pronounced for the “fluctuating pH” data (see lower graph). Thus, lower pHs appear to interfere with a snail’s ability to perceive predation risk. When extrapolated to the situation in natural tidepool habitats, the second-experiment data suggest that refreshment of nighttime-induced low-pH conditions by the incoming tide may be insufficient to ameliorate negative effects of low pH on a snail’s escape behaviour. As provocative as these laboratory observations are, notably in their “ecological relevance” to future ocean “acidification”, one wonders if the researchers could now go out to the tidepools and perform some confirmatory in situ experiments? Jellison et al. 2016 Proc R Soc B 283: 20160890.

NOTE1 in comparison, the second or “fluctuating pH” experiment uses 10 pH levels with alternating exposure times (18h at one pH followed by 6h at a second pH reduced by 0.75 units from the first), repeated daily for 5d. This protocol tests whether daily “rebound” exposure to higher pH will enable recovery from low-pH impairment effects on escape behaviour. Behavioral tests are done in the second, reduced level, pH

NOTE2 if there were to be any criticism of this nicely designed and executed study, it would be to question why, with such an abundance of research specimens available in the tidepools, only a single snail is tested at each pH level. How can individual variability be appraised and incorporated into the statistical analysis?

NOTE3 the high levels in this range (8.0-7.7) represent natural fluctuations that occur in nearshore waters around the study site, with the addition of a pH 7.2 treatment representing an extreme level projected for the next century. The low levels (7.2-6.5) are based on the range just given and reflect a drop of 0.75 pH that occurs during nighttime in the tidepools from respiratory CO2 production from both plants and animals

NOTE4 another more dramatic escape behaviour by Tegula is to release its attachment to rocks and fall downwards on contact with, or scent of, Pisaster ochraceus. The authors likely considered and then rejected this behaviour, on the basis that holding on takes energy and, if energy were sapped by exposure to lower-pH water, the response assessment could be confounded

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