1. Brown,
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Influence of High Volume Human Populations on the Common
Starfish, Asterias rubens
Courtney N. Brown, Department of Biology, University of Nebraska at Kearney, Kearney, NE
68849

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ABSTRACT1
The goal of this study was to examine the influence of high volume human populations2
on the near-shore populations of the starfish species Asterias rubens, or the Common Starfish.3
Specifically, the purpose of this study was to examine the relationship of human populations and4
the arm damage that A. rubens incurs from these human populations. For two separate beaches5
with similar conditions aside from human population, sixty-five A. rubens starfish were collected6
from thirteen random, different feeding spots of pre-designated criteria. Five A. rubens7
specimens were collected from each of these spots, including ones that had missing or damaged8
arms. Arm lengths were measured from the center of the starfish to the outermost point of each9
arm. These lengths were averaged for each A. rubens measured, and an overall average was10
calculated. When compared statistically, the overall average arm length of the A. rubens at the11
beach with the smaller human population was found to be significantly different than the overall12
average arm length for the beach with the larger human population. These results suggest that13
high volume human populations do influence the size of Asterias rubens in a beach
setting.
14
15
Key Words: Asterias rubens, arm damage, habitat, human interference, conservation
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INTRODUCTION1
Disruption of a habitat by humans can cause lasting effect (Sano et al., 1987). Over time,2
the more humans disturb a habitat, including that of starfish such as Asterias rubens, the less3
food a species within that habitat will be able to obtain (Sano et al., 1987). As in all species,4
when food supply is low many changes will occur (Vevers, 1949). Some of these changes may5
be irreversible (Whilde, 1985). When the food supply diminishes, individual starfish size trends6
smaller through time. (Menge, 1972). In addition, high levels of human impact cause physical7
damage to the bodies of starfish, causing them to have to regenerate limbs (Ramsay et al., 2001).8
While regeneration is one of the defining traits of starfish, continued regeneration will require9
energy from the starfish that would be used differently if a specimen did not have to deal with so10
much damage (Ramsay et al., 2001). Energy that would have gone toward reproduction or11
hunting larger prey would have to go toward arm regeneration (Barker and Nichols, 1983).12
Starfish that regenerate limbs multiple times due to constant damage can lose up to 40% of their13
lipids and 85% of the amount of kilojoules in their pyloric caeca (Lawrence and Larrain, 1994).14
While large, this loss of lipids and energy is not necessarily lethal for starfish (Lawrence et al.,15
1999). However, starfish with arms that are lost multiple times will have a lowered ability to feed16
(Ramsay et al., 2001). Furthermore, a continuously damaged habitat on top of arm loss will17
result in decreased size of the starfish, including misshapen or shorter limbs (Marrs et al., 2000).18
Starfish arm regeneration is not a cost-free attribute for any starfish species
(Bingham and19
Burr, 2000). While this regenerative ability is helpful and allows starfish to escape many20
potentially life-threatening situations (Ramsay et al., 2000), the starfish does trade a lot of energy21
to regenerate a lost appendage (Bingham and Burr, 2000). This energy used for regeneration will22
lower the ability of the starfish to reproduce (Bingham and Burr, 2000). Also, when starfish has23

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to regenerate arms more than normal, and it does not have enough energy to do this since it1
cannot catch prey as well, the arms can come back shorter and not quite equal to the other arms2
(Ramsay et al., 2001). However, starfish having a normal, pentameral symmetry is advantageous3
to the organism (Wu et al., 2012). A starfish that has all five of its arms is best at autotomy, or4
self-amputation, which gives it a better chance of escaping a deadly situation in comparison to5
starfish that do not have that pentameral shape (Wu et al., 2012). In combination with autotomy,6
starfish with five arms have an advantage in detection, turning over, and adherence versus those7
with a different number of arms (Wu et al., 2012).8
Humans influence the environment of starfish in more ways than one. For example, the9
starfish caught by towed, bottom fishing gears are adversely affected as well as areas that were10
subjected to different levels of fishing intensity (Ramsay et al., 2001). This does not only result11
in arm loss that will result in regeneration as a means of repair (Ramsay et al., 2001). In an even12
worse scenario, starfish will not lose the arm, but will have its ambularal ossicles damaged13
(Ramsay et al., 2001). These little plates that cover the arm of starfish, when damaged, can cause14
misshapen arms that do not heal (Ramsay et al., 2001). This type of damage can result in reduced15
fitness and reduced ability to capture prey, which can result in reduced size and reduced arm16
length (Ramsay et al., 2001). The continued, potentially severe damage often has more severe17
repercussions than simply not being able to capture prey and reduced size. The starfish with18
missing or damaged arms showed a 44 – 69% decrease in egg production seven months after arm19
loss (Bingham and Burr, 2001). Even 19 months after the arm damage or arm loss occurred,20
lowered egg reproduction was still evident (Bingham and Burr, 2001). It is estimated that even21
normal arm damage, such as partial arm loss from a predator, can reduce the ability of a starfish22
to reproduce by 7 – 10% (Bingham and Burr, 2001).23

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There are quite a few factors regarding starfish feeding and the specific prey starfish will1
pursue (Menge, 1972). Some of these factors include the caloric content of the potential prey,2
how easy the prey is to capture, and the size of the prey (Menge and Menge, 1974). While3
starfish are typically food generalists, the type of prey they tend to search for is usually4
influenced by the environment that they live in (Menge, 1983; Gallagher et al., 2008). If human5
interactions with the environment of Asterias rubens has altered the environment or cause6
excessive arm damage or arm removal at, then this species of starfish will have a difficulty7
catching prey (Marrs et al., 2000). This includes being able to pry open bivalves (Marrs et al.,8
2000). In addition, starfish that are disfigured or constantly missing an arm will not be able to go9
after the normal size of prey they have been known to seek (Marrs et al., 2000).10
The major goal of this study is to determine if a beach with more human traffic11
negatively impacts the size of starfish in a beach setting in comparison to a beach with much less12
human traffic. Specifically, this study will examine the average arm length of the Common13
starfish, Asterias reubens. A second goal is to examine conservation methods of near-shore14
habitats of the Asterias reubens in regards to human interference.15
16
MATERIALS AND METHODS17
Animals18
All specimens used in this study are invertebrates of one starfish species, Asterias rubens.19
Even though neither the Guide for the Use and Care of Laboratory Animals (NAS, 2011) nor a20
review board will be needed for this study, it is a goal of this study not to damage any animals or21
disturb their habitat. Sixty-five specimens of A. rubens will be obtained by hand from shallow22
feeding spots less than a meter deep on both beach study sites. Feeding spots are defined as the23

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shallow, rocky tide pool areas found near the shores of both beaches. The species of starfish1
being examined usually eats bivalves, but will eat small crustaceans and other echinoderms if2
necessary in order to survive (Tuya and Duarte, 2012). All of these organisms exist in the3
feeding spots along with A. rubens. To randomize the selection of the feeding spots, twenty-five4
spots will be located and numbered before the study is conducted. The names of the spots will be5
entered in Excel and, using the random function, thirteen spots will be chosen. Five specimens6
will be carefully removed from each feeding area. Each specimen obtained will then have its7
arms measured with a standard ruler. Natural rubber gloves will be worn to decrease contact with8
the A. rubens. This will help to prevent any mishandling or dropping of the specimen due to9
spines that can be irritating to touch. Specimens of A. rubens that do not have all of their legs10
intact will still be measured so that results will not be incorrect or skewed.11
No A. rubens will be permanently removed, sacrificed, or modified during the duration of12
the study. Each specimen will be removed from its habitat, have its arms measured, and returned13
to its original location. All arm measurements and weather conditions will be logged on custom14
logbook sheets.15
16
Arm Length Average17
Arms on each A. rubens will be measured and noted. The arm lengths will then be18
averaged for each starfish. The arm of each starfish will be measured from the center of the19
specimen to the tip of each arm. These averages will then be used for statistical analysis.20
21
Weather Conditions and Feeding Location Marking22
Weather conditions will be monitored closely, recorded, and should be similar and close23

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to optimal conditions for the study on both beaches. Optimal conditions, in this study, would1
mean no rain, an average humidity of 75% to 80%, an average wind velocity of 24.14 to 32.192
kph, and an average temperature of 23.85° to 25.85° Celsius for both beaches. Weather will be3
recorded for both beaches each day the study is conducted. Specifically, temperature, humidity,4
wind velocity, tide height, and tide speed will be measured in regards to weather. The study will5
not be conducted in inclement weather, including thunderstorms of any severity. For records,6
each A. rubens feeding spot will be noted in terms of latitude and longitude with a GPS receiver7
– a Bushnell 360310BG Backtrack D-Tour.8
9
Statistical Analysis10
The data will be tested for normality using the Shapiro-Wilks test. Provided that the data11
collected is normal, it will be analyzed using the Student’s t-test. The level of significance will12
be α = 0.05. This means that if the calculated p-value for average arm length is less than the13
significance level, or p < 0.05, the null hypothesis of the average arm length of the starfish on the14
two beaches no different will be rejected in favor of the alternative hypothesis. However, if the15
data is shown to be non-normal, then the Wilcoxon rank-sum test can be used as an alternative to16
a Student’s t-test.17
18
RESULTS19
The data sets collected from both Wrightsville Beach, NC and Myrtle Beach, SC were20
shown to be normal and have equal variances, allowing a Student’s t-test to be used to examine21
the data. The overall average arm length of the Asterias rubens specimens that were collected22
and measured from Wrightsville Beach, NC were significantly different (p=0.001) in comparison23

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to the overall average arm length of the Asterias rubens specimens that were collected and1
measured from Myrtle Beach, SC (Wrightsville 8.77 + 1.28; Myrtle 8.09 + 1.06. The five2
individual averaged arm lengths were larger for the Asterias rubens data set collected from3
Wrightsville Beach, NC.4
5
DISCUSSION6
The interference by humans on starfish habitats has been known to lead to increased7
instances of arm damage and an overall reduction in size of starfish species over time8
(Barthelemy, 1992). Anywhere up to 80 – 85% of the kilojoules of energy that Asterias rubens9
stores can be used to regenerate lost limbs (Fan et al., 2005; Franco et al., 2012). If this energy10
expenditure can lead to an overall reduction in size, normal prey such as the mussel Mytilus11
edulis or other smaller species of starfish may become harder to catch by Asterias rubens (Allen,12
1983; Dolmer, 1998). In addition, if arm damage occurs often and in multiple arms, prying13
mussels open can become increasingly difficult for Asterias rubens (Anger et al., 1977; Jackson14
et al., 2008). The observation of significant differences in overall Asterias rubens arm length on15
the shores of Wrightsville Beach, NC and Myrtle Beach, SC suggests that interference from high16
volume human populations does influence these arm length differences when other conditions17
are similar. The beach with the larger human population, Myrtle Beach, had the smaller overall18
arm length as well as smaller individual average arm lengths. This is consistent with the19
observation that increased human interference, physical, mechanical, or otherwise, on starfish20
populations correlates with increased damage to members of these populations (Kaiser, 1996;21
Joly-Turquin et al., 2009). The larger the volume of a human population, the more damaged22
limbs Asterias rubens seem to have. In addition, the observation in this study is consistent with23

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the observation that continued injuries to members of a starfish population will lead to an overall1
decrease in size to cut back on the energy used to regenerate limbs. If Asterias rubens have limbs2
that are smaller in general, less energy will be spent to regenerate those limbs after damage or3
loss has occurred.4
The ways high volume human populations influence arm lengths can upset the balance of5
the ecosystem that exists in near-shore feeding spots as well. Since Asterias rubens cannot pry6
open mussels or successfully prey on other starfish species if they are missing or have damaged7
arms, this can lead to a number of problems involving the population control of other species8
(Kamermans et al., 2009). Asterias rubens typically preys on and are most successful with9
averaged sized mussels, not under or over sized ones (Norberg and Tedengren, 1995). If Asterias10
rubens are not able to prey on mussels, such as Mytilus edulis, it can lead to that particular size11
or species of mussel overcrowding a habitat and not allowing other, smaller species of mussels to12
coexist with them (Yamada et al., 1992; Kulakovskii and Lezin, 1999; Reimer et al., 1999). Also,13
if Asterias rubens cannot hunt smaller starfish or outcompete other starfish species in their14
habitat, problems can still occur (Zeidler, 1992; Saier, 2001). Either situation would allow15
another species of starfish to overpopulate a habitat and upset the balance of that habitat (Penney16
and Griffiths, 1984). Asterias rubens can also be reduced in size enough or damaged enough to17
become easier prey to more species (Aldrich, 1976). Other species in a habitat that are not18
normally predators may become predators if Asterias rubens are reduced in size or are19
continuously damaged (Arrontes and Underwood, 1991). Regardless of the main cause for20
Asterias rubens not being able to obtain prey, mortality rates of this species if they are deprived21
of a food source or have a harder time obtaining it (Paine, 1976; Bergmann and Moore, 2001).22
The loss of the ability to prey on mussels is the biggest, since Asterias rubens need sterols to23

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function and mussels are a major source of them (Voogt and Rheenen, 1976).1
It is important to try and limit the amount of damage dealt to Asterias rubens populations2
by human interference. Asterias rubens can already face difficulty thriving by other3
environmental changes, and human interference can only add to these problems (Guillou et al.,4
2012). Changes such as ocean acidification can suppress the immune system of Asterias rubens5
(Hernroth et al., 2011). In addition, increased salinity can lead to decreased adhesive tenacity as6
well as slowed or improper development in Asterias rubens (Saranchova and Kulakovskii, 1982;7
Berger and Naumov, 1996). Environmental changes alone can lead to abnormal behavior in8
Asterias rubens, such as retreating to deeper waters, since this species of starfish does not9
tolerate environmental changes as well as other competitive starfish species (Smith, 1940;10
Shulgina, 2006). Even sediment changes can lead to a change in the vertical distribution of11
starfish (Kurihara, 1999). These environmental changes, coupled with human interference in12
high levels, can lead to Asterias rubens that are very easy to damage or easily lose their limbs13
(Rogers et al., 2001; Hotchkiss, 2008). At minimum, if this human interference is lowered,14
Asterias rubens could face less amounts of damage or lost limbs.15
16
ACKNOWLEDGEMENTS17
Thanks to Dr. Marc Albrecht for assistance with editing suggestions for this manuscript18
and guidance throughout the entire research project it is based around and to the UNK19
Department of Biology for technical assistance and the chance to design and carry out this20
research project21

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29.

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Table 1. Averages for individual and overall arm length of collected Asterias rubens specimens from
Wrightsville Beach, NC and Myrtle Beach, SC.
_____________________________________________________________________________________
Arm 1 Arm 2 Arm 3 Arm 4 Arm 5 Overall Average
Wrightsville (n=65) 8.75 + 1.49 8.79 + 1.40 8.77 + 1.50 8.82 + 1.46 8.74 + 1.56 8.77 + 1.28*
Myrtle (n=65) 8.16 + 1.41 8.06 + 1.45 7.93 + 1.54 8.08 + 1.55 8.26 + 1.17 8.09 + 1.06*
_____________________________________________________________________________________
Values in Table 1 are means + standard deviations. Arm lengths expressed in centimeters (cm). Starfish
were measured from center to the tip of each arm, even if the arm had been damaged or removed. Starfish
from each location were taken from randomly selected feeding spots of pre-determined criteria. Weather
conditions for collection days were of pre-determined criteria and were similar for both beach collection
sites. *When the overall average arm lengths are compared in a two-tailed t-test, the p-value = 0.001,
which is less than the alpha level of α = 0.05.

18. Brown,
Courtney
BIOL
831E
Spring
2014
2
May
2014
18
Figure 1. Legend

19. Brown,
Courtney
BIOL
831E
Spring
2014
2
May
2014
19
Figure 1. Average arm length of individual arms of Asterias rubens collected from Myrtle Beach, SC and
Wrightsville Beach, NC. Arm lengths are measured in centimeters to the nearest tenth. Error bars are with
the standard deviation of each averaged arm length. n = 65 for each group and includes damaged or
missing arms.