Physiological ecology
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  Metabolism
  Topics on the physiological ecology of sea anemones include metabolism considered here, and MYCOSPORINE-LIKE AMINO ACIDS and DESICCATION & OTHER STRESSES considered elsewhere.
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Research study 1
 

graph showing oxygen uptake in sea anemones Metridium senile in air and waterMany intertidal animals have some ability for aerial oxygen uptake when air-exposed by tides as long as their gas-exchange surfaces remain moist. Studies on sea anemones Anthopleura elegantissima and Metridium senile collected from Pacific Grove, California show that both species have a good capacity for oxygen consumption or VO2 in air over durations of at least 4h. In the smallest individuals of both species, VO2’s in air are comparable to those in water, but with increasing body size aerial rates decline disproportionately. VO2 of contracted individuals of A. elegantissima in water is significantly less that that of expanded ones, suggesting that most of the gas exchange is via the tentacles, with their provision of relatively greater surface area.  Interestingly, following 4h air-exposure, neither species shows evidence of a significant oxygen debt.  However, in other experiments comparing VO2’s in air of high- and low-level A. elegantissima, while high-level individuals do not incur a debt after 20h, low-level ones do, indicating an anaerobic contribution to their metabolism.  Shick et al. 1979 Physiol Zool 52: 50; Shick 1981 Mar Biol Lett 2: 225.

NOTE  while A. elegantissima is regularly (4h) exposed to air in its intertidal habitat, M. senile is less likely to be exposed, especially larger individuals. Only results for M. senile are shown here

 

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Research study 2

 

photograph of an intertidal population of aggregating anemones Anthopleura elegantissimadrawing of sea anemone Anthopleura elegantissima showing measurements used to estimate total prey-catching surface areaIn Bodega Bay, California, sea anemones Anthopleura elegantissima at high-intertidal levels may be air-exposed for up to 18h each day, while low-intertidal individuals may be continuously immersed for periods of several days.  Time available for feeding therefore differs greatly between them and the question arises as to whether physiological compensation occurs to redress the imbalance.  This is tested at the Bodega Marine Laboratory by examining prey masses in in the gastrovascular cavities of each of the 2 types after a single immersion period.

Results show that high-level individuals catch 3 times more prey than low-level ones.  The difference does not owe to differences in digestion rates or to graph comparing prey-capture surface areas in high- and low-intertidal anemones Anthopleura elegantissimafeeding surface-areas.  In fact, tentacle surface areas relative to mass do not differ significantly in the 2 groups (see graph). These greater prey-capture rates in high-level anemones support faster growth rates than in low-level ones.  Thus, minimum size for reproduction is attained relatively faster in the high-level individuals despite the reduced time available for feeding. The author discusses alternative hypotheses to explain the results but, in the end, returns to the simplest explanation that high-level anemones capture prey faster than low-level ones.  Zamer 1986 Mar Biol 92: 299.

NOTE  represented by combined areas of tentacles and oral disc as shown in the drawing above Right. Tentacle areas are estimated using the formula for surface area of a cylinder, using the mid-point of each tentacle as mean cylinder diameter

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Research study 3
 

pie diagrams comparing energy budgets in high- and low-level sea anemones Anthopleura elegantissimaIn a follow-up article to Research Study 2 above, researchers at the Bodega Marine Laboratory, California calculate energy budgets for high- and low-intertidal populations of Anthopleura elegantissima.  Components of the budget include measured costs of ammonia excretion, as well as estimates for respiration, food intake, and absorption, and for energy and nutrients translocated from symbiotic algae.  The overall budgetary shortfall is about 30% of absorbed energy, attributed by the authors to unmeasured costs of specific dynamic action (SDA) and mucus production.  The budgets for the 2 populations shown in the pie diagrams confirms that “scope for growth”, or the energy available for growth and reproduction, is considerably greater in high-level anemones (29% of absorbed energy) than in low-level ones (20%), partly because of lower estimated metabolic demands and greater prey-capture rates in the former group.  Another cause of the difference, as suggested by the authors, is that continuous feeding in the low-level anemones may decrease digestive efficiency owing to faster transit of food through the gastrovascular cavity.  Zamer & Shick 1987 Mar Biol 93: 481.

 

photograph of sea anemone Anthopleura elegantissima at high tide NOTE  SDA is manifested as extra heat produced after a meal.  Long thought to be wasted energy, as in this paper, SDA is now considered a requisite cost of protein synthesis or growth.  In studies that measure oxygen uptake post-prandially, that is, within a few hours of eating, SDA is included in the respiration component of the budget (= R), and thus would not be missing from the budget.  The authors do not measure oxygen uptake directly; rather, estimate it from results of previous experiments, which may have been done as long as 24h after feeding, thus possibly excluding most or all SDA

Several high-intertidal A.
elegantissima
photographed
when the tide is in 0.7X

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Research study 4
 

Although most or all clonal taxa have the ability to reproduce sexually, the question arises as to whether limited genetic variability leads to a reduced ability to respond to environmental change.  In this regard, there are 2 alternative evolutionary “pathways”.  The first is selection for  a general-purpose genotype that maintains high fitness in a variety of conditions; the second, selection for genotypes that are specialised to specific conditions (termed the “frozen niche-variation” hypothesis).  To test this, a researcher at Santa Catalina Island, California compares several physiological traits in clones of the corallimorpharian Corynactis californica at a single site.  Then, clones are translocated reciprocally between 2 sites to test their physiological adaptability.  Results show that while rates of asexual fission do not differ among clones at a single site, other physiological differences exist, sometimes of surprisingly large magnitude.  For example, significant differences are present in tissue-protein content (1.6-fold), gas exchange polyp of corallimorpharian Corynactis californica possibly in early division(3.4-fold), excretion (3.5-fold), and tissue growth (35-fold).  Translocation of clones reveals some effects of environment, but not on gas exchange or fission rates.  The author concludes that clones of C. californica have markedly different phenotypes and exploit phenotypic plasticity to maintain relatively constant fission rates despite significant tissue-growth differences among clones and between environments.  The finding that clones of C. californica are associated with genotypes that do well in differing environments therefore supports the “general-purpose genotype” hypothesis.  Edmunds 2007 Mar Biol 150: 783.

NOTE  these include tissue composition, gas exchange, excretion, tissue growth, and rates of asexual fission

NOTE  genetically identical clone-mates are initially identified by colour and close physical contact, then confirmed by DNA “fingerprint” analyses

 

A polyp of Corynactis californica possibly in an early
stage of asexual fission. Note the pronounced indentation
in the edge of the polyp at the 10 o'clock position 3X

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