Rizal Technological University Boni Ave. Mandaluyong City

College of Arts and SciencesDepartment of Biologymajor in Biotechnology

In partial fulfillment of the Requirementsin Animal Cell Physiology and in vitro Culture

Behavioral Physiology of Hermit Crabs in Different Water Conditions

Submitted by:

Justine M. AlmanonJowanna Marie L. Burce

Romnick J. FeraldoJuaymah B. Policarpio

Submitted to:

Prof. Angelita P. Medalla

11th October , 2010

Introduction

Hermit Crab, common name for any member of a family of marine crabs

and for several related terrestrial crabs. They are found on or just off the coasts

of Europe and the Americas. Hermit crabs, also called robber crabs, are

armorless animals, the largest of which are found along the Pacific coast and

attain a length of up to 46 cm (18 in). They insert their abdomens into gastropod

mollusk shells that they carry about with them for protection. The abdomens of

the crabs are soft and asymmetrical, flexed and twisted to fit into the whorls of

the borrowed shells. Their abdominal appendages are especially modified for

keeping the shell firmly supported on the body (Redmond, WA: Microsoft

Corporation, 2008)

According to Hazlett (1996) hermit crabs are often forced to seek new

shells because they have outgrown their old ones; they change their housing

whenever chancing upon another shell into which they can fit. Most hermit crabs

are marine. The few terrestrial forms are tropical and of the same family as the

coconut crab. Tricarico & Gherardi (2007) stated that Hermit crabs are ideal

organisms to investigate whether resource assessment might effectively modify

an animal’s motivation and to what extent. The survival, growth, and reproduction

of this taxon strictly depend on the occupancy of gastropod shells of appropriate

size and shape. A shell that is, for instance, too small can inhibit the growth of

the inhabiting crabs, reduces their protection against predators and their survival,

and affects reproductive success in both sexes. By contrast, a shell that is too

large makes locomotion energetically wasteful (as found in terrestrial hermit

crabs, and affects female reproduction. Shell fit may also alter hermit crabs’

responses to environmental cues and their general behavior. Therefore, there is

a strong selective pressure for hermit crabs to obtain a shell of the appropriate

size.

Hermit crabs display clustering behavior and daily movements which are

closely related to the tidal rhythm (Turra & Leite, 2000). Clusters are typically

formed during low tides when hermit crabs stay in physical contact with each

other, presenting low activity and preference for shady substrates. The clustering

behavior is probably controlled by interaction between exogenous and

endogenous factors related to the tidal cycle. In this way, environmental stimuli

(air exposure, hydrostatic pressure, light, food availability and small scale water

movements) seem to play an important role in the determining the activity of the

hermit crabs.

The main objective of the study is to determine the effects of different

water conditions in the behavior physiology of Hermit Crabs. To modify their

behavior in appropriate manner and to observed their switching shells if an empty

shell is available.

Review of Related Literature

Cenobita spp., commonly known as Hermit Crab, unlike true crabs have

soft, vulnerable abdomen. In order to protect their soft bodies from predators,

hermit crabs use abandoned shells of other marine animals, mostly snails. Once

it has outgrown its shell, it discards it and looks for a new shell. This behavior of

the hermit crab gives rise to competition for shells among the members of this

species (Bose, 2010). As the distribution of hermit crabs is very wide, the have

been able to adapt to several different kinds of habitats. Though they are usually

found in shallow waters, some hermit crabs even live in plant stems, while

several species are found in kelp forests. Possibly the best know hermit crabs

facts is that their bodies do not have a hard, protective carapace. They need a

shell to protect then from predators, which is why they use discarded snail shells

or other hollow objects. They move around by dragging their shell with them, and

retreat into it when threatened (K, 2010).

There are almost 500 different species of the hermit crab. Some are

aquatic whereas there are others that are terrestrial. The hermit crab habitat of

the aquatic forms range from the shallow waters of the coral reefs and shores to

the depths of the bottom of the sea. The best places to look for hermit crabs are

the inter-tidal areas, for example the tide pools where a large number of

planktons can be found. The terrestrial forms are usually found in the tropics.

There is also the Caribbean hermit crab that is known to be capable of climbing

up trees (Bose, 2010). Among the 500 listed species of Hermit crabs,

approximately only 15 species are terrestrial, while the rests are aquatic. Most of

the species of Hermit crabs popular as pets are terrestrial in nature. These

include prominent species such as the Caribbean hermit crab, Australian land

hermit crab and the Ecuadorian hermit crab. Other than these species, a few

more species are becoming popular due to their longer life span and availability

in abundance. The average life span of the species kept as pets initially, seldom

exceeded a few months. More recently, it has been observed that some species

of Hermit crabs tend to live for relatively longer period, if proper care is provided.

In fact, species like the Caribbean hermit crab have an average life span of 23

years; with some individuals even living for 30 years or more, though such

examples are rare (Naik, 2010).

The most general classification is the Kingdom Animalia, which contains

all the animals on Earth. Hermit Crabs belong to one of the largest groups of

animals. The arthropods known as Phylum Arthropoda. They are invertebrates

that have jointed legs and a hard outer covering called exoskeleton. The Phylum

Arthropoda is further broken down and includes the Class Crustacea. It is divided

into Order such as crab, lobster, and shrimp which are all in the Order Decapoda.

(Choosing Crustaceans: All about Hermit crabs (n.d.) Moreover, Hermit crabs

can’t reproduce in captivity as they do in the wild. When mating, the Hermit

Crabs extended about ¾ of the way out of their shells. The male uses his flexible

fifth pair of legs to place his spermatophore into the female’s gonophores. After

the crabs have mated, the female attaches the eggs to her abdomen inside her

shell and carries them around with her until they are ready to hatch. Hermit crab

eggs must be hatched in salt water in order to survive. They use the tiny pinchers

on the end of her fifth pair of legs to snip each cluster of eggs from her body. The

eggs hatch upon contact with the sea water and the little creatures are released.

Hermit crabs are one of the most extraordinary pets because of their

ability to make attention-grabbing, easy care friends. They have very distinctive

characteristics; have vigorous and inquisitive nature, and their unique personality

with low maintenance charges make them appealing to us as good pets as long

as we provide them proper environment and food. Basically, Hermit Crabs are

omnivores, which mean they feed on both vegetation and animal material. There

are two types of Hermit Crabs found, marine and land hermit crabs. Usually,

Land Hermit Crabs are considered as good pets (Pakhare, 2010). Their feeding

behavior is highly fascinating retreat for eyes. In the wild, land hermit crabs eat

almost anything like fallen fruit, leaf litter, decaying wood, plants and grasses.

Although they are not specific in their diet, recent studies have shown that hermit

crabs need calcium, carotene and antioxidants (McGuigan, 2010). It can witness

the fading in their color at the time of molting if their diet is carotene deficient. It

can supplement their diet with brightly-colored vegetables, like corn and carrots

to make up the deficiency of carotene. It can feed them meat, fish, vegetables

and fruit as they are omnivorous in nature. They also like tannin-rich foods like

tree bark and oak leaves. (Pakhare, 2010). Hermit crabs are nocturnal

scavengers that will eat almost anything. Based on the article of Land Hermit

Crabs (2002), they are terrestrial crabs that carry their shells on their backs. And

like the other crabs; they are decapod (ten-legged) crustaceans. In addition,

Choosing Crustaceans: All about Hermit crabs (n.d.) states that hermit crabs

have long abdomen that curl under their bodies. They also use only three pairs of

legs for walking and have longer antennae than the true crabs. In the same way,

hermit crabs are actually quite sociable creatures. In the wild, they live in

colonies and often travel in packs of up to 100 crabs. Fight occasionally breaks

out among these crabs as they outgrow their shells and look for larger ones to

inhabit.

During the day, hermit crabs conceal themselves from the harsh sun and

predators by hiding out under trees, driftwood, leaves, and rocks or by burying

themselves in the sand. But during the cooler evening hours, they wonder the

beach looking for food, searching for new shells, and mating. However, they are

very particular about their shells, which offer them much needed protection in the

wild. The crabs always seem to be looking for newer, bigger or better shell to

move in.

Molting is a process in which a hermit crab faces a lot of stress so it is at

this time that it requires a lot of care and concern. Molting is a natural process of

growing for a hermit crab wherein it sheds its exoskeleton and forms a new one.

The frequency at which a crab molts depends on the growth rate and size of

individual crabs with smaller ones molting every 3 to 4 months and larger ones

molting once every year. This is a time that the hermit crab needs to be treated

with extra care as it is defenseless and vulnerable (Gupta, 2010).

Male hermits are often seen dragging around a female by their small claw,

fiercely fighting off rival suitors with their big claw. The male will drag his potential

mate around until she is ready to molt. When the female crab molts she is

receptive and the male can then fertilize her eggs. Hermit crabs are mainly

scavengers and can often be seen digging for food, preying on smaller

organisms, or scrounging for scraps on the ocean floor (Ellie, 2010).

Hermit crabs are common in tropical intertidal areas of the world and

occupy the empty shells of marine gastropods. However, unlike the original

gastropod owner of the shell, they are unable to completely seal off the aperture

of the shell in times of environmental stress, such as dilution of seawater by fresh

water. These factors may make hermit crabs better indicators of changes

occurring in intertidal conditions and community structures than snails, clams and

oysters which can temporarily seal out unfavorable changes in surrounding

conditions. Further, hermit crabs, like many other decapods, tend to have a

limited capacity for osmotic regulation. Consequently, they are vulnerable to

osmotic stress caused by freshwater inundation resulting in the dilution of sea

water. Species, however, may differ in their tolerance to dilution of their blood

and body fluids, and therefore, in their survival during episodes of freshwater

inundation (Dunbar et al., 2003).

The cognitive abilities of hermit crabs in information gathering and

decision making are impressive. They rely on the use of gastropod shells for

shelter and shells of adequate size, shape and strength, but without being too

heavy, are key resources. A hermit crab gathers information about shells by

vision (Reese 1963) but this information is enhanced during approach and

contact. After contact it grasps the shell with its walking legs and chelipeds and

explores the exterior, moving its chelipeds over the surface, and then turns the

shell so that the aperture is uppermost and begins to investigate the interior by

inserting one or both chelipeds or sometimes a walking leg. It obtains detailed

information as to the size, internal volume, shell species (shape) and weight

during this process and assesses the overall quality relative to that of the shell it

is currently occupying. The crab may move into the new shell and test the inside

of the shell by thrusting the abdomen back and forth. It might also investigate the

interior and exterior of the original shell and even move back into it, assessing

which is the better of the two. Hence these crabs demonstrate sophisticated shell

investigation behavior, remembering the information gathered at each stage of

the investigation, and also remembering specific shells for up to 40. They may

also fight another crab over ownership of shells in which case information about

the shells and the opponent is integrated with information about their own

physiological state. They can remember previous opponents for up to 4 days and

it has been suggested that they may select which crabs to fight on the basis of

their perception of how their current shell might suit the opponent. Thus crabs

have the ability to gather and use information from a variety of sources and to

make comparisons between shells and between opponents (Elwood & Appel,

2009).

Many invertebrates do appear able to assess risk levels based on

chemical stimuli. For example, marine snails can distinguish between predatory

and non predatory brachyuran crabs, starfish and snails as well as between

crabs fed conspecific or other snail species. Freshwater snails respond differently

to the scent of different predators (fish or crayfish) fed conspecific snails.

Barnacles can distinguishbetween predatory and nonpredatory snails and

starfish. Mussels can distinguish between predatory crabs and herbivorous

urchins, and burrowing bivalves can distinguish between feeding and starved

crabs. Similarly, snails, polychaete worms and crabs can all distinguish chemical

stimuli released by damaged conspecifics from those released by more distantly

related prey. Hermit crabs respond differently to different chemical stimuli in their

environment. They can distinguish their own scent from that of other individuals.

Predator effluent may interfere with mating, and odors from living, damaged or

dead snails or conspecific hermit crabs attract them or increases shell grasping

behaviour. Hermit crabs also respond to visual stimuli in their environment, and

these responses may be modulated by olfactory cues. Shell-breaking crabs are

important predators of hermit crabs. Although hermit crabs clearly respond to the

effluent from predatory crabs, whether they can distinguish between predatory

and non predatory crabs remains unclear (Rosen et al., 2009).

Hermit crabs are ideal organisms to investigate whether resource

assessment might effectively modify an animal’s motivation and to what extent.

The survival, growth, and reproduction of this taxon strictly depend on the

occupancy of gastropod shells of appropriate size and shape. A shell that is, for

instance, too small can inhibit the growth of the inhabiting crabs, reduces their

protection against predators (e.g., Angel 2000) and their survival, and affects

reproductive success in both sexes. By contrast, a shell that is too large makes

locomotion energetically wasteful and affects female reproduction. Shell fit may

also alter hermit crabs’ responses to environmental cues and their general

behavior. Therefore, there is a strong selective pressure for hermit crabs to

obtain a shell of the appropriate size. Empty shells (hermit crabs are unable to

directly prey on living snails; for an exception, are in acutely short supply in the

habitat. Most often, they can be found after snail death at gastropod predation

sites. Alternatively, shells may be obtained by conspecifics or heterospecifics

through negotiation or interference competition. In any case, except for very few

instances, appropriate shells are extremely difficult to recruit. As a result, the vast

majority of the hermit crab populations studied so far chronically suffers from a

reduced growth. An apparently obvious consequence of the vital importance of

empty shells for hermit crabs on the one hand, and of their scarce availability on

the other, is that these organisms have evolved the ability to make fine

distinctions between the quality of a shell found in the habitat, either empty or

occupied by conspecifics or heterospecifics, and the current domicile shell. This

ability has been confirmed by a large number of studies, mostly conducted in

Pagurus bernhardus. For instance, escalated shell fights occur in this species

when the shell at stake is of a higher quality than the attacker’s domicile shell.

Similarly, individuals enter an empty shell more quickly when there can be an

increase in quality, whereas the speed of rejecting the shell correlates with its

unsuitability. Knowledge about the quality of an external shell is obtained by

hermit crabs first by the means of sight and later by tactile stimuli acquired during

their manipulation of both the exterior and the interior of the shell–shell

investigation (Tricarico & Gherardi, 2007).

The cognitive abilities of hermit crabs in information gathering and

decision making are impressive. They rely on the use of gastropod shells for

shelter and shells of adequate size, shape and strength, but without being too

heavy, area key resource. A hermit crab gathers information about shells by

vision but this information is enhanced during approach and contact. After

contact it grasps the shell with its walking legs and chelipeds and explores the

exterior, moving its chelipeds over the surface, and then turns the shell so that

the aperture is uppermost and begins to investigate the interior by inserting one

or both chelipeds or sometimes a walking leg. It obtains detailed information as

to the size, internal volume, shell species (shape) and weight during this process

and assesses the overall quality relative to that of the shell it is currently

occupying (Elwood & Appel, 2009).

Materials and Methods

Collection of Hermit Crabs

Cenobita clypeatus were collected from Cartimar in Gil puyat Avenue,

Makati Extension, Pasay City. They were separated randomly into three groups

with three samples each that were submerged with different water condition.

Hermit crab were gathered immediately transported to the laboratory where they

were be kept in aquariums for 12 hours light and acclimated in a constant

temperature at 25-27°C in aerated water for at least two weeks before being

exposed to treatments.

Preparation of Water in Different Conditions

In order to assess the different conditions, capabilities and how it would be

affected by water types, the hermit crab were submitted to individual and

combined saltwater and Artesian well water taken in Pateros. Using groups of

three Hermit Crabs submerged in water with different conditions have been

tested: (1) Artesian well water (groundwater, GW); (2) Saltwater (SW); (3)

Artesian well water + Saltwater (GW+SW), and (4) Control (aerated water).

Setting of the Experimental Conditions

Cenobita clypeatus were weighed every week, until the 21 days of

exposure have been completed. They have been selected for testing without

regard to the shell type, weight, and no effort was made to mate the individuals.

For setting-up the videos, these were created by filming the natural environment

of the hermit crabs. Using 30 cm wide colored video monitor was placed outside

of the aquariums. The duration of filming were recorded every Friday between

September 17, 24, and October 1, 2010. Extraneous sound, vibration and visual

stimulation were minimized during the experiment and all the filming were

conducted between one to three hours.

Survival Test

In laboratory, hermit crabs were kept in three glass aquarium with the

volume of two liters of saltwater for Aquarium (SW), two liters of Artesian well

water for (FW), 1 liter for (SW) + 1 liter of FW for SW+FW aquarium and for the

control, Aerated water (AW) was used. The crabs were fed thrice a week with

tiny shrimp pellets, etc.

Experiments investigated the survival of Cenobita clypeatus to different

water conditions at different pH. Twelve individuals of hermit crabs were

randomly selected and three individuals placed in aquariums with different

conditions. Throughout the duration of experiment, Hermit crabs were observed

for signs of life. Individuals that did not respond by the movements of antennules,

walking legs, chelipeds and with foul odor, were considered dead and are to be

removed from the aquarium. The interval in which each hermit crab died was

recorded.

Behavioral Physiology

The behavior of the Hermit crabs was observed for a total of 5 hours. Two

separate behaviors were observed and these occurred to varying degrees

depending on the water conditions:

Locomotion of Hermit Crab

The locomotion was examined in the laboratory. This was the only

behavior that has been described previously in relation to water conditions.

According to McGaw et. al, (1999), locomotion activity were quantified each time

the hermit crab changed the speed whether it is fast, slow or moderate as they

submerged in water. Hermit crabs have two types of pattern in terms of

movement which Herreid & Full (1986) observed. It can be move forward and

sideways.

Flicking of antennae

The antennae were flicked up and down, independently of each other;

each separated movement was counted as an event. To determine the

percentage time of antennules retraction, we observed the antennules made

continuous rapid flicking movement while extended, but for periods of time they

would be folded backwards into a depression in the carapace; the approximate

percentage of time and the antennules were retracted was observed (McGaw et

al, 1999).

Shell Acquisition

Using the empty shell, we were offered the hermit crabs empty shells and

observed the movement of their resource, the empty shell or vacancy, a chain of

interactive events.

Three Hermit crabs for each sample were randomly assigned three empty

shells for observation the movement of their resources, the empty shell or

vacancy, in a chain of interactive event. For each of them, it recoded the

likelihood and total duration of shell investigation.

Hiding Times

To determine the hiding times of hermit crabs: the time elapsed from the

moment of the tap until the hermit crab emerged fully from its shell, was recorded

to the nearest second with a digital stopwatch.

Results and Discussion

Survival test

Exposure of the crabs to both SW + GW resulted in important increased of

10% of the total body weight after 10 days. No change in weight was observed

upon exposure to saltwater and aerated water. Exposure of the crabs to GW

resulted in mortality: 1 hermit crab died (within 15days).

Table 1 shows the survival rates of the hermit crabs in SW, SW + GW and

AW in low pH. From this table, it can be clearly seen that hermit crab survive

notably in SW, better than GW in 7 pH. Survival of hermit crabs for all water

conditions are the longest at the acclimation of room temperature. In controls

(AW), 3 hermit crabs had 100% survival after 21 days of exposure, respectively.

In SW and SW + GW, all hermit crabs are still alive while in GW, one hermit crab

died. However, Hermit crabs in SW and SW + GW survived extensively rather

than GW which has two crabs survived after 15 days of exposure.

 Alive Total Dead Total

SW GW SW+GW AW SW GW SW+GW AW

September17 3 3 3 3 12 ---- ------ ---------- ---- 0

September24 3 2 3 3 11 ---- ------ ---------- ---- 1

October 6 3 2 3 3 11 ---- ------ ----------- ----- 0

Table 1 shows the survival rates of Hermit crabs in Different Water Conditions.

Laboratory studies indicated a higher tolerance of Cenobita sp. in SW

longest periods of exposure. Prolonged exposure to low pH in the experimental

condition resulted in a significant differences in survival in favor of Cenobita spp.

Shell acquisition

Hermit crabs rely on shell for their survival. A total of ten observations

were made resulted in 6 fights. This observation was analyzed because the

hermit crab initiated shell fight. Fights were most possible observed in GW and

least possible in SW. In the first week of experimental conditions, we observed

that 1 of the hermit crabs in SW + GW aquarium has a missing limb. Gupta

stated that once the hermit crab loss limb, they begin to restore their limbs by

growing a gel limb. This is a natural process called molting wherein hermit crab

shed its exoskeleton and forms a new one. According to Childress, it is a time

where hermit crab needs to have a new empty shell to fit in. in fact, empty shells

are extremely rare in some environment, all except the most damaged being

occupied by the crabs. As a result of the limited nature of useful gastropods shell,

there is competition associated with highly ritualized aggressive display and shell

fighting behavior. In addition, reduced hiding time when attacked by a shell

breaking crab is probably adaptive because it would abandoned their shell and

flee when picked up by a large, shell breaking crab.

Behavioral physiology

Locomotor activity

Hermit crab usually moves forward rather than sideways. Locomotors of

Cenobita spp. Increased as the pH decreased. In SW, there was a large variation

between individual crabs. Although there was a strong movement towards

greater activity in low ph. Locomotion of hermit crabs was move to manifest in

SW + GW aquarium wherein activities remained important above conditions in

the duration of the experiment. Both SW and GW showed an immediate

increased in activities of the crabs as the pH lowered. However, the pattern was

somewhat differ in AW and SW + GW. The activity level of Hermit crab in GW

decreased during the 2 hours of exposure and in AW was largely inactive after

30 minutes. They covered themselves in the sand and rocks, and move from

time to time. We also minimized the used of driftwoods to avoid overstay in

branches for them to submerged in different water conditions. Mortality was low

after 3 weeks of exposure and the acclimation time used would be a good

adjustment that are made by hermit crabs to specific set of laboratory

conditions .Cenobita spp. Walk forward on six legged using an alternating tripod

gait similar to that of insects. The first walking leg provides the driving force for

locomotion aided secondarily by the second walking leg, while the cheliped act

largely as support. The left appendages are longer and heavier that the right and

they extended further laterally from the midline during their stride, thus

compensating for the asymmetry of the crab which has dextrally coiled shell and

abdomen displaced to the right. The abdomen is normally carried off the ground,

but it is dragged when the shell is large. This has been confirmed by other

studies (Herreid II & Full, 1986).

Flicking of Antennae

The antennae and antennules of crustaceans have been implicated as

having a chemo sensory role in water exposure (Mcgan et al., 1999). Both the

antennae and antennules were flicked up and down during the experiments.

Each Hermit crab also responded to a decrease in pH with an increase in

frequency of flicking their antennae. In saltwater, the HC antennae were flicked

up and down, on the average, 2-3 times per minutes, and it did not change with

the water condition. There was also no significant change in antennae flicking in

AW, since this behavior was only observed in GW and SW aquarium.

The antennules of all the crabs were flicked rapidly while oriented in

different directions, but were also retracted into the carapace for period of time.

In GW, each species retracted the antennae for about S-20 second of every

minute, but distinct differences between the species occurred in the lower pH.

Crabs in AW retracted its antennules upon initial exposure, but after 10 minutes

the antennules remained extended. For the entire experimental condition, the

pattern was similar in SW + GW, with the antennules exposed for longer periods

in all. In SW and GW, the opposite response was seen, in low pH, the HC

retracted the antennules. Each HC individuals in GW also retracted the

antennules to a greater degree in all experimental condition, but there was no

significant differences in the retraction times between the GW, SW, AW and SW

+ GW, as occurred in HC. However, with such variability within and between the

species, it is hard to draw conclusions as to the role of the antennae in salinity

detection (Mcgan et al.,1999). The percentage of time that the antennules were

folded dack into the carapace was recorded because flicking was too rapid to

allow accurate determinator of rate. According to Van Weel et at., possibly these

HC avoid low pH exposure with an isolation type response. These results as well

as other behavioral and physiological work suggest that the antennules are more

important than the antennae for salinity setection. In addition to the antennae and

antennules HC posses’ hair –peg organ on many areas.

Hiding time

Log transformation normalized the distribution of hiding times and also

homogenized the variances. Mean hiding times varied by a factor of two among

the experimental condition and those differences are highly significant. Hiding

time (time to emerge from the shell after disturbance) is a convenient behavior of

hermit crabs because it is easy to score quantitatively (Rosen et al.,2009) and it

is a useful measure of response to predation risks. Hiding times of hermit crabs

might increase either in the presence of predators that are unlikely to break

through their gastropod-shell retreat, or in the presence of visually orienting

predators that are on prey motion (Hazlett, 1997)

Conceptual Framework

Preparation of Hermit Crabs

List of Figures

Preparation of Water in Different Condition

Setting of the Experimental Condition

Survival Test

Behavioral Physiology Observation

Locomotion of Hermit Crabs

Flicking of Antennae

Shell Acquisition Hiding times

Figure 1. Acclimation of aquarium, a) Aerated Water, b) Groundwater, c)

Saltwater and d) Saltwater + Groundwater.

Figure 2. Selection of Hermit Crabs in different water condition, a) Aerated

water, b) Groundwater, c) Saltwater and d) Groundwater + Saltwater.

Figure 3. Preparation of artificial environment in different water condition

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