Tessaly Jen
Advisor: Jim Watanabe
BIO 175H
Anthopleura Sea Anemone Distribution
in the Rocky Intertidal at Hopkins Marine Station
Abstract
Climate change has already begun to change species abundances and distributions
within intertidal habitats. Monitoring such changes over time provides valuable
information about potential shifts in ecosystem dynamics. Congeners of the sea anemone
Anthopleura are conspicuous members of intertidal communities along the North
American Pacific coast. Previous studies have shown that these congeners differ in their
latitudinal habitat range. This study attempted to discern the distribution of anemones in
the intertidal at Hopkins Marine Station. It found that A. xanthogrammica were
significantly more abundant in the exposed areas on the western side of the point, while
A. sola were significantly more abundant on the relatively protected eastern side of the
point. These distributions were correlated with temperature—the body temperatures of
emersed A. xanthogrammica were significantly lower than those of A. sola. Potential
decreases in the more cold-adapted A. xanthogrammica and increases in the warmadapted A. sola may occur as climate change ensues, and this study provides a baseline
against which future distribution studies may be compared.
Permission is granted to use the citation and abstract of this paper.
Introduction
The thermal tolerances and optimal temperature ranges of species may be
increasingly important as the effects of climate change intensify. From the hydrothermal
vents at the bottom of the ocean to the rocky intertidal at the surface, species distributions
are commonly correlated with temperature gradients. For example, the vertical
distributions of Tegula congeners in the intertidal are set by thermal tolerance limits
(Tomanek and Somero 1999). For these snails (and many other organisms) these
tolerance levels are associated with heat damage to proteins and other physiological
structures, and the species’ ability to respond to stress with heat shock proteins (Tomanek
and Somero 1999). Latitudinal species ranges are also often associated temperature
gradients and thermal tolerance. For example the upper and lower thermal limits of
different species of porcelain crabs of the genus Petrolisthes, as set by cardiac function,
correspond to habitat temperatures in colder temperate regions and warmer tropical
regions (Stillman 2003).
Such thermal tolerances have profound implications for warming associated with
climate change. As warmer temperatures spread to higher latitudes, species replacements
and distribution shifts are likely to create drastic changes in intertidal ecosystems. Such
distribution shifts have already begun to occur. A study of limpet congeners at Hopkins
Marine Station illustrates a northward shift in both species (Crummett and Eernisse
2007). The range of the southern congener, Lottia austrodigitalis, was found to have
shifted substantially northward at the expense of the northern congener, Lottia digitalis,
between 1978 and 1998 (Crummett and Eernisse 2007). Another study at Hopkins
Marine Station identified increases in southern invertebrates and decreases in northern
2
invertebrates from the 1930s to the 1990s (Barry et al. 1995). Continued observations of
the occurrence and rate of these shifts provide valuable information about global,
regional, and local impacts of climate change.
Sea anemones of the genus Anthopleura have different latitudinal distributions
with wide overlapping ranges. Anthopleura xanthogrammica and Anthopleura sola, two
solitary Anthopleura species, both have considerable populations in the California rocky
intertidal. A. xanthogrammica has a more northern distribution, ranging from northern
Baja to Alaska (Sagarin and Gaines 2002). Meanwhile A. sola ranges from central Baja
to northern California (Sagarin and Gaines 2002). This study attempted to provide
baseline knowledge of the relative abundances of each species in the rocky intertidal at
Hopkins Marine Station. This map of Anthopleura distributions may be a useful
comparison for future studies. Furthermore this study attempted to determine if either
congener had a habitat preference (in relation to the vertical gradient or the lateral
gradient from exposed to protected regions) within the intertidal. Lastly, the study sought
to determine correlations between temperature and species abundance.
Methods
Study Species and Study Site
Primarily two species of Anthopleura sea anemones were assessed: A. sola and A.
xanthogrammica. A. elegantissima, the cloning Anthopleura, was also considered, but the
spatially heterogeneous nature of A. elegantissima colonies complicated sampling efforts
and thus focus was given to the two solitary species instead. The prevalence of A.
xanthogrammica and A. sola in the intertidal, their relatively easily identifiable features,
3
and differing latitudinal ranges made them ideal species to examine for relationships
between temperature and distribution.
Field experiments were conducted in the rocky intertidal at Hopkins Marine
Station (HMS) of Stanford University in Pacific Grove, CA (36°36’N, 121°54’W). The
study site lies within the Lovers Point State Marine Reserve, one of the four small marine
protected areas in the Monterey/Pacific Grove coastline. Its latitude within the
overlapping region of the three study species’ ranges makes it a key location to study
potential species distribution and abundance shifts.
Transects to assess species abundance were completed during low tide 19 April,
20 April, 21 April, 29 April, 30 April, 3 May, 17 May, and 19 May (2010). A. sola and A.
xanthogrammica body temperatures were measured on 19 May, 2010.
Experimental Design
Six transects were chosen to represent wave-exposed environments and six were
chosen to represent protected environments. The protected sites were mostly shielded
from incoming waves by large rocks and thus experienced less wave action and reached
warmer temperatures than the exposed sites (Fig. 1). Two transects, one in an exposed
area and one in a protected area, were sampled by a Stanford University biology class
along transects which were delineated by permanent bolts on the rocks and which have
been monitored for species abundances since 2002. The remaining ten transects were
chosen to span the majority of the point, 5 in exposed areas and 5 in protected areas (Fig.
1).
4
Transects ran perpendicular to the shoreline from the higher intertidal (beyond the
vertical limit of anemone distribution) to the lowest point that was sufficiently exposed to
sample at low tide. .25 m2 quadrats were placed on altering sides of each transect at every
meter. A. sola and A. xanthogrammica individuals were counted and recorded and
percent cover of A. elegantissima was estimated within quadrats. A visual estimate of
algal cover and substrate was also recorded. Quadrat heights were estimated using
reference heights with known absolute heights above MLLW, a surveyor’s level, and a
4m stadia rod.
Temperature data were obtained every hour starting at 7am and continuing until
the tide had risen high enough to submerge all A. sola individuals and the majority of A.
xathogrammica individuals at 2pm. Body temperature was measured using a
thermocouple. Forty A. xanthogrammica individuals and 40 A. sola individuals were
sampled, almost all of which were emersed for the majority of the sampling period,
which occurred from 7am to 2pm. Individual A. xanthogrammica were all located within
roughly a 10m radius at a wave-exposed site and individual A. sola were all located
within a roughly 10m radius at a wave-protected site (Fig. 2). These sites were chosen to
represent the exposed area as a whole and the protected area as a whole. If anything, the
chosen protected site (where A. sola individuals were monitored) was not as warm and
sheltered as many of the other sites, thus any differences indicated by the study are likely
amplified in other regions of the intertidal.
Statistical Analysis
5
T-tests were used to compare the mean number of A. xanthogrammica per square
meter in exposed sites versus protected sites. The same was done for A. sola. T-tests were
also used to compare the mean height of A. xanthogrammica and A. sola individuals
along common transects. Lastly, T-tests were used to identify significant differences in
the mean temperatures of A. xanthogrammica and A. sola at each hour of the thermal
study.
Results
Abundance Study
A. xanthogrammica and A. sola differed distinctly in abundance along the
Hopkins shoreline (Fig. 3). The mean population density of A. xanthogrammica was
significantly higher in exposed areas compared to protected areas (t = 2.933, P = .015;
Fig. 4). The mean density of A. sola showed the opposite pattern and was significantly
greater in protected transects compared to exposed areas (t = 4.522, P = .001; Fig. 5).
An attempt to compare height distributions of A. xanthogrammica and A. sola was
made, however results were relatively inconclusive due to the limited number of transects
with both species present. Only transects A and E had sufficient individuals of each
species to analyze mean height of anemones statistically. Mean heights of A.
xanthogrammica were significantly higher than A. sola along transect E (t = 2.851, P =
.009; Fig. 6) but not significantly different along transect A (t = .864, P = .404; Fig. 7).
Temporal comparisons between the abundances of each Anthopleura species
along the two class transects (C and J) this year and previous years were inconclusive.
The extent of sampling each year was contingent upon the height of the tide and intensity
6
of waves—in years when the tide was higher or waves were bigger, the lower portion of
the transect was not assessed. This makes it difficult to compare year to year. In addition,
dubious and dramatic species shifts suggested by the class’ data are likely
misidentifications rather than true changes.
Thermal Study
Though 40 A. xanthogrammica and 40 A. sola individuals were observed in the
thermal study, some of these were submerged by changing tides. Due to the
overwhelming control of the ambient water temperature on the core temperature of
submerged anemones, these individuals were not included in statistical analyses of the
Anthopleura temperatures. Hourly comparisons of mean body temperatures showed
significantly higher values for A. sola for every time measured (t-tests, Table 1; Fig. 8).
Discussion
Anthopleura xanthogrammica and Anthopleura sola show clearly defined spatial
patterns with A. xanthogrammica primarily occupying the wave-exposed western side of
the point at Hopkins Marine Station and A. sola occupying the protected eastern side of
the point. These observations are consistent with previous findings that A.
xanthogrammica inhabits less protected habitats and is especially abundant in surge
channels, crevices, and areas which are constantly washed over by water, as compared to
A. sola, which generally favors calmer pools and rock surfaces (Sagarin and Gaines 2002;
Russo 1984). I expected to find a correlation between height in the intertidal and species
as well, however these results were inconclusive. Due to the extreme lateral separation of
species across the intertidal, there were a limited number of transects for which both
7
species were present and thus the assessment of differences in vertical distributions was
inconclusive. Of the two transects analyzed for differences in mean anemone height, one
suggested that A. xanthogrammica inhabited a slightly (less than 0.5 m) higher section of
the intertidal. This counters the expected direction of difference yet it is relatively
inconsequential since there are no replicates to support the conclusion. The clear support
for a lateral separation of species and lack of data/evidence for a vertical separation of
species may indicate that wave exposure plays a more dominant role in setting
distributions than do vertical gradients in physical conditions. However, the design of the
study may skew conclusions as transects could not pick up as much fine scale variability
as might be necessary to determine height specificity. It is therefore possible that A.
xanthogrammica generally prefers lower habitats, just as past research has shown
(Francis 1988).
Though there were not a sufficient number of A. elegantissima clones along
transect lines, a rough survey of the rocks surrounding transects suggested a clear site
preference of this cloning anemone. Large colonies were often observed on the sides of
rock faces in protected areas but rarely seen in wave-exposed areas. This is consistent
with previous research which identified A. elegantissima as confined to protected outer
coast sites or moderately exposed inner coast sites in the Pacific northwest (Sebens
1983).
The apparent lack of overlap in species within regions of the intertidal may be due
to competitive exclusion. In discussing the limited northward extent of A. sola, Russo
(1984) suggested that A. xanthogrammica might competitively exclude A. sola. These
forces may be at play on a smaller scale in the intertidal off Pacific Grove as well.
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Aggressive interactions are best established in cloning species, which compete with each
other for space (Williams 1991). A. elegantissima clones responded aggressively to
genetically distinct neighboring clones during repeated contact (Francis 1973). A.
xanthogrammica also has acrorhagi (fighting tentacles) bearing potent nematocysts which
are used in such aggressive responses (Francis 1973). Though A. xanthogrammica
individuals undergo habituation and do not show aggression towards neighbors in contact
with their tentacles for long periods of time, selective removal and replacement of
individuals shows that A. xanthogrammica do exhibit agonistic behavior to non-neighbor
anemones (Sebens 1984). It is plausible therefore, that A. xanthogrammica aggressively
exclude A. sola individuals that attempt to establish themselves in exposed areas.
A rough survey of the substrate and surrounding organisms indicated some
differences between wave-exposed and protected sites, including a higher abundance of
mussels, feather boa kelp, and barnacles in wave-exposed sites. Such differences may
affect the suitable habitats of Anthopleura congeners. Sebens (1983) identified the
dominance of Mytilus californianus prey as an indicator for abundant populations of A.
xanthogrammica. Therefore composition of prey species or competitors within a site may
also affect which Anthopleura congener dominates.
The significant differences between temperatures experienced by A.
xanthogrammica and A. sola during low tide suggest that temperature tolerance may be a
driving force behind their intertidal distributions. The consistently lower temperature
experienced by emersed A. xanthogrammica and absence of A. xanthogrammica at the
warmer A. sola site imply that that A. xanthogrammica may have a lower thermal
tolerance or at least a lower thermal optimum than A. sola. An analysis of anemones on
9
the North American Atlantic coast indicated a clear correlation between habitat
temperature and upper lethal temperature of anemone species (Sassaman and Mangum
1970). The southern limit of species ranges in Metridium senile, Diadumene leucolena,
and Haliplanella luciae correlated to lethal temperature, with the northernmost species
(Metridium senile) having the lowest lethal temperature and the southernmost species
(Haliplanella luciae) having the highest lethal temperature (Sassaman and Mangum
1970). Sassaman and Mangum (1970) noted that the three species had otherwise
ecologically similar niches and suggested that temperature was therefore the likely
constraint on species ranges. They further noted that the metabolic rates of anemones
were subject to Q10 effects, thus indicating a mechanism of temperature sensitivity
(Sassaman and Mangum 1970). Given the analogous restrictions on the ranges
Anthopleura congeners, similar effects may dictate latitudinal distribution limits in these
Pacific anemones. Furthermore, it is possible that such temperature sensitivity exists on a
local scale between cooler wave-exposed areas and warmer protected areas to set
distribution limits within one intertidal location as well.
The relationships between temperature and algal symbionts of Anthopleura
species have been studied extensively and may affect anemone distributions as well.
Anthopleura congeners may have one or two species of algal symbionts—some have
solely zooxanthellae, some have solely zoochlorellae, and some have both—and the
relative proportion of either symbiont is closely correlated to light/temperature gradients
(O’Brien and Wyttenbach 1980, Secord and Augustine 2000, McCloskey et al. 1996,
Secord and Muller-Parker 2005). A study of A. xanthogrammica and A. elegantissima
showed that zoochlorellae are commonly associated with the cooler temperatures at
10
higher latitudes and in the lower intertidal, while zooxanthellae are more abundant in
anemones at lower latitudes or higher in the intertidal (Secord and Augustine 2000).
Another study of A. xanthogrammica identified a transition from solely zoochlorellate
individuals in the subtidal and low intertidal to anemones with mixed algal populations in
the middle intertidal to exclusively zooxanthellate anemones in the high intertidal
(O’Brien and Wyttenbach 1980). A shift from zooxanthellate to zoochlorellate A.
elegantissima along a gradient from light-exposed to fully shaded environments in an
intertidal cave show the same correlation (Secord and Muller-Parker 2005).
The composition of algal symbionts within a host may have significant
implications on the growth and reproduction of the host. Zooxanthellae respire and
photosynthesize at a higher rate than zoochlorellae and translocate a substantially greater
amount of carbon to their hosts (contribution of carbon to animal respiration was
estimated at 48% for zooxanthellate anemones but only 9% for zoochlorellate anemones)
(Alan Verde and McCloskey 1996). A study of A. elegantissima revealed that
temperature increase from 13°C to 20°C caused a significant reduction in density of
zoochlorellae which led to zoochlorellate anemones receiving 3.5 times less carbon at
20°C (Engebretson and Muller-Parker 1999). As zoochlorellae are more temperature
sensitive, warming due to climate change will likely have significant effects on the
densities of these two symbionts in their Anthopleura hosts. Given the symbionts’
different nutritional contributions to their hosts these shifts may have profound effects on
the growth and reproductive abilities of anemones. Since zoochlorellae are typically
associated with larger individuals in the lower intertidal (Secord and Augustine 2000), A.
xanthogrammica may experience more dramatic shifts in symbiont composition. If
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zoochlorellate A. xanthogrammica are unable to acquire zooxanthellae as they lose
zoochlorellae, they may become aposymbiotic. As aposymbiotic anemones lose mass
more quickly during starvation than those with symbionts (Sebens 1983), this could have
profound effects on the survival of A. xanthogrammica if prey abundances decline.
A. elegantissima and A. sola must cope with the environmental stresses associated
with their habitats. To handle elevated sunlight exposure, they attach gravel and other
debris to their body surfaces as an effective sunscreen that reduces zooxanthellae
expulsion (Dykens and Shick 1984). In addition to this protection, A. elegantissima
respond biochemically and behaviorally to sunlight and photosynthetically generated
oxygen stress by increasing superoxide dismutase and catalase activities in proportion to
chlorophyll concentration, and by contracting and shading zooxanthellae (Dykens and
Shick 1984). If anemones experience shifts in symbiont densities from less productive
zoochlorellae to more productive zooxanthellae, these photodynamic stresses may
increase and force anemones to invest more into enzymatic defenses, which could come
at a cost to growth or reproduction.
There are clear differences in the distributions of A. xanthogrammica and A. sola
in the rocky intertidal at Hopkins Marine Station. A. xanthogrammica appear to prefer
more wave-exposed areas while A. sola favor more protected areas. Multiple factors may
influence these differences, including competitive exclusion, prey abundance, and
temperature. The temperatures of emersed A. xanthogrammica individuals were
significantly lower than those of emersed A. sola, suggesting that temperature may be a
major factor influencing species distributions not only at wide latitudinal scales but also
at local scales, such as around the point at the Hopkins Marine Station. The temperature
12
relationships of each species’ lethal thermal tolerance, metabolism, and symbiont
composition will be of increasing importance as climate change warms intertidal
ecosystems. Due to these effects, I suspect that future years and higher temperatures may
produce an increase in the abundance of A. sola at Hopkins Marine Station and a decrease
in A. xanthogrammica. This study provides a baseline against which future changes in the
composition of Anthopleura congeners may be compared.
13
Acknowledgements
Many thanks to my advisor, Jim Watanabe, for being extremely generous with his
support, advice, and time. Thanks to Mark Denny as well for help with the temperature
study. Lastly, thank you to the BIO 44Y class, and especially to the students who helped
with my transects.
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References:
Alan Verde, E. and L.R. McCloskey (1996). Photosynthesis and respiration of two
species of algal symbionts in the anemone Anthopleura elegantissima. Journal of
Experimental Marine Biology and Ecology. 195(2): 187-202.
Barry, J.P., Baxter, C.H., Sagarin, R.D. and S.E. Gilman (1995). Climate-related, longterm faunal changes in a California rocky intertidal community. Science.
267(5198): 672-675.
Crummett, L.T. and D.J. Eernisse (2007). Genetic evidence for the cryptic species pair,
Lottia digitalis and Lottia austrodigitalis and microhabitat partitioning in
sympatry. Marine Biology. 152(1): 1-13.
Dykens, J.A. and J.M. Shick (1984). Photobiology of the symbiotic sea anemone,
Anthopleura elegantissima: defenses against photodynamic effects, and seasonal
photoacclimatization. Biological Bulletin. 167: 683-697.
Engebretson, H.P. and G. Muller-Parker (1999). Translocation of photosynthetic carbon
from two algal symbionts to the sea anemone Anthopleura elegantissima.
Biological Bulletin. 167(1): 72-81.
Francis, L. (1973). Intraspecific aggression and its effect on the distribution of
Anthopleura elegantissima and some related sea anemones. Biological Bulletin.
144: 73-92.
Francis, L. (1988). Cloning and aggression among sea anemones (coelenterata: actinaria)
of the rocky shore. Biological Bulletin. 174: 241-253.
McCloskey, L.R., Cove, T.G. and E. Alan Verde (1996). Symbiont expulsion from the
anemone Anthopleura elegantissima (Brandt) (Cnidaria; Anthozoa). Journal of
Experimental Marine Biology and Ecology. 195: 173-186.
O’Brien, T.L. and C.R. Wyttenbach (1980). Some Effects of Temperature on the
Symbiotic Association between Zoochlorellae (Chlorophyceae) and the Sea
Anemone Anthopleura xanthogrammica. Transactions of the Americal
Microsopcial Society. 99(2): 221-225.
Russo, A.R. (1984). Space partitioning within populations of sea anemones (genus
Anthopleura) in the California rocky intertidal zone. International Review of
Hydrobiology. 64(4): 521-528.
Sagarin, R.D. and S.D. Gaines (2002). Geographical abundance distributions of coastal
invertebrates: using one-dimensional ranges to test biogeographic hypotheses.
Journal of Biogeography. 29: 985-997.
15
Sassaman, C. and C.P. Mangum (1970). Patterns of temperature adaptation in North
American Atlantic coastal actinians. Marine Biology. 7(2): 123-130.
Sebens, K.P. (1983). Population dynamics and habitat suitability of the intertidal sea
anemones Anthopleura elegantissima and A. xanthogrammica. Ecological
Monographs. 53(4): 405-433.
Sebens, K.P. (1984). Agonistic behavior in the intertidal sea anemone Anthopleura
xanthogrammica. Biological Bulletin. 166: 457-472.
Secord, D. and L. Augustine (2000). Biogeography and microhabitat variation in
temperate algal-invertebrate symbioses: zooxanthellae and zoochlorellae in two
Pacific intertidal sea anemones, Anthopleura elegantissima and A.
xanthogrammica. Invertebrate Biology. 119(2): 139-146.
Secord, D. and G. Muller-Parker (1995). Symbiont distribution along a light gradient
within an intertidal cave. Limnology and Oceanography. 50(1): 272-278.
Stillman, J.H. (2003). Acclimation capacity underlies susceptibility to climate change.
Science. 4(5629): 65.
Tomanek, L. and G.N. Somero (1999). Evolutionary and acclimation-induced variation in
the heat-shock responses of congeneric marine snails (genus Tegula) from
different thermal habitats: implications for limits of thermotolerance and
biogeography. Journal of Experimental Biology. 202: 2925-2936.
Williams, R.B. (1991). Acrorhagi, catch tentacles and sweeper tentacles: a synopsis of
‘aggression’ of actinarian and scleractinian Cnidaria. Hydrobiologia. 216-217(1):
539-545.
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Figures and Tables
QuickTime™ and a
decompressor
are needed to see this picture.
Figure 1. Transects: from left to right, the first Transects A-F are the exposed transects
and transects G-L are the protected transects. Transects C and J are the transects which
were pre-chosen and assessed by the biology class.
17
QuickTime™ and a
decompressor
are needed to see this picture.
Figure 2. The site of the 40 A. xanthogrammica individuals monitored in the temperature
study is denoted by the blue square. The site of the 40 A. sola individuals is denoted by
the red square.
18
Density of Anemones by Species
Mean # of Anemones per sq. m
8
7
6
5
A. xanthogrammica
A. sola
4
3
2
1
0
A
B
C
D
E
F
G
H
I
J
K
L
Transect
Figure 3. Density of anemones by species along each transect with 95% confidence bars,
from west to east (A to L), with transects A to F representing exposed sites and G to L
representing protected sites.
Abundance of A.
Mean # of Anemones per sq. m
5
4
3
2
1
0
exposed
protected
-1
Site
Figure 4. Mean abundance of Anthopleura xanthogrammica in exposed sites versus
protected sites with 95% confidence interval bars. A t-test confirms significant
differences between exposed and protected sites (t = 2.933; P = .015).
19
Abundance of A.
7
Mean # of Anemones per sq. m
6
5
4
3
2
1
0
exposed
protected
-1
Site
Figure 5. Mean abundance of Anthopleura sola in exposed sites versus protected sites
with 95% confidence interval bars. A t-test confirms significant differences between
exposed and protected sites (t = 4.522; P = .001).
Vertical Distribution of Anemones
3
2.5
Height (m)
2
A. xanthogrammica
A. sola
1.5
1
0.5
0
0
1
2
3
4
5
Abundance
Figure 6. Height distributions of A. xanthogrammica and A. sola individuals along
transect A. A t-test of the mean height of A. xanthogrammica individuals versus A. sola
20
individuals suggests that there is not a significant difference in the vertical distribution of
the two species (t = .864; P = .404).
Vertical Distribution of Anemones
1.4
1.2
Height (m)
1
0.8
A. xanthogrammica
A. sola
0.6
0.4
0.2
0
0
1
2
3
4
5
6
7
8
Abundance
Figure 7. Height distributions of A. xanthogrammica and A. sola individuals along
transect E. A t-test of the mean height of A. xanthogrammica individuals versus A. sola
individuals suggests a significant difference in the vertical distribution of the two species
(t = 2.851; P = .009).
Mean Temperature of Emersed Anemones
Temperature (degrees C)
30
25
20
A. xanthogrammica
A. sola
15
10
5
0
7am
8am
9am
10am
Time
21
11am
12pm
1pm
Figure 8. Mean temperature of emersed anemones at each hour of measurement are
shown with 95% confidence interval bars. Table 1 presents the relevant values of t-tests
for differences between A. xanthogrammica and A. sola temperatures at each hour.
Table 1. Results of t-tests comparing the average temperature of emersed A.
xanthogrammica individuals and emersed A. sola individuals at each hour of the study
show that differences are significant at each time of measurement.
Time
t-value
P-value
7am
10.165
7.355x10-14
8am
6.798
3.695x10-9
9am
7.621
7.791x10-11
10am
7.803
3.578x10-11
11am
5.239
1.538x10-6
12pm
8.389
5.330x10-12
1pm
6.598
1.593x10-8
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