The Effect of Human Urbanization on the Growth And Development of the Acheta domesticus

8/11/2019 The Effect of Human Urbanization on the Growth And Development of the Acheta domesticus

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/bstract

Acheta domesticus are organisms found in a variety of natural and man made habitats& They have

good tolerance of different temperatures and thus e press a good model organism to gauge the

changes to the surrounding environment& The research uestions are: "hat effects does human

interfered environments have on the Acheta domesticus 3 "hat do these changes have on the

growth patterns of the insects themselves3

Two wee old A domesticus will be put into different simulated environments& Some specific

tan s will be used to imitate the natural habit for the species while others are created to simulateman made areas 5e&g& trash filled basements6& Temperature$ humidity$ as well as light e posure

will all be ept at that of that particular environment& ric ets are then observed for their

behavior7growth within their two different environments& 8ood will be monitored so that cric ets

will always have the ability to feed& 9n average in the wild$ it ta es about three months at 2- to

,2 degrees elsius before the cric ets reach adulthood& These growth patterns within a

population will be monitored by the speed of molts$ which a cric et must accomplish in order to

develop 5molting involves the shedding of the old e os eleton6$ as well as behavioral

observations to see whether the cric ets within the human made environments develop

differently than those ept in natural environments& These observations will continue until the

death of the cric ets by natural causes& /fter four months of observation$ the data was processed&

8inal )udgments e pressed a 2&1mm increase in size for individuals within human environments

as compared to individuals within wild environments& To contrast however$ individuals within

the simulated man made environment e pressed a shorter lifespan than those ept within the

The Effect of Human Urbanization on the Growth and Development of the Acheta domesticus


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simulated natural environment& To conclude$ it can be tentatively generalized that human

urbanization can increase cric et size but decrease lifespan&



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* periment Table of ontents:2& /bstract

;& 'ntroduction

.& %ife ycle

-& +aterials


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'ntroduction

The Acheta domesticus $ nown collo uially as the

common house cric et$ was once native to southwestern

/siaAs warm$ subtropical environments 5"eissman6&

!ow however$ its popularity both as fish bait and as a

food source for many pet reptiles and amphibians has caused them to be widely bred by humans&

>ue to its popularity$ the Acheta domesticus has been widely distributed throughout the biosphere in almost every single continent$ barring /ntarctica& 'n the #nited States where it is

commonly sold alongside mealworms and earthworms as fish bait and animal food& The house

cric et has also been distributed across much of the *astern #nited States as feral populations$

adapting to a Bmultitude of different habitats$ minus southern 8loridaC 5"eissman6& %ately$ feral

populations are beginning to ta e hold within the warm$ arid chaparral and urbanized areas of

southern alifornia$ where it most li ely is spreading due to a lac of predation&

Acheta domesticus is a great insect for scientific e periments such as this one due to its

hardiness$ relatively fast rate of growth$ large spawn numbers$ and fairly low pricing for

maintenance& 9ne ey aspect that separates the A domesticus from the ma)ority of !orth

/merican cric et species is its lac of a dormancy period 5"al er6& "ithout this Bspecial

overwinteringC stage$ these cric ets crowd around warm buildings$ sewage dumps$ as well as

enter into human habitation 5"eissman6 in order to sta e out the cold months& This human

association greatly boosts the species possible adaptability to an urbanized world$ but we do not

necessarily now of the effects of this action& The ma)ority of the cric et species die out during



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the cold months$ leaving only eggs to overwinter$ or sit dormant in burrows and hibernate

through the winter& This dormancy period creates a lac of se ual reproductive activity for many

of the native cric ets& ?owever$ A domesticus%which lac the dormancy period$ may utilize the

time within the warm human habitation to continue reproduction$ thus curving an imbalance

within the overall species population& This is why it is a nice candidate for answering what

urbanization has on the species&

Their life cycle begins with the deposition of eggs into damp soil$ sand$ or peat moss this step

will simply be s ipped in my e periment for the sa e of saving time& The e periment calls for

two wee old cric ets& 8ollowing their brea out from the eggs$ Acheta domesticus will continueto eat and develop& *ating$ and more importantly food$ is of importance if the cric et is to

successfully mature in a timely manner 5before winter sets in6& * periments have already been

done where the cric ets will have slowed growth if a lac of food is present& (ypassing this$ the

environments themselves will be focused upon for the duration of the observation& (y using the

same offerings for both the natural and the human made simulated habitats$ one will not have to

worry about an e tra variable which can potentially s ew data& #ltimately$ results from the

e periment can determine whether urbanization will help or harm the species&

%ife ycle

The ma)ority of this observation will be during the nymphal stage of the Acheta domesticus & 't is

within this particular stage that one can see the largest amount of growth and change within the

organism& 9nce a cric et becomes an adult$ it is much harder to )udge change for it will be more

apt at trying to breed than to feed and interact with its environment$ simulated or not& >uring this

period of growth$ as mentioned before$ the nymph will go through well over five molts before

reaching adulthood 5"eissman6& This period of time is perfect for observing the cric etAs



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development through gradual differences within the set habitats& These changes are most

apparent towards the beginning of their life cycle$ where molts may only be within one to two

wee s of each other 5 ?allett6& !earing the end of the molts$ the cric ets will begin to slowdown in

growth and eating in preparation for their last molt& They will then begin final development of their

se ual organs within their penultimate instar&

*ach group of cric ets will be monitored for changes as well as molting rate$ which is the ey

factor in identifying developmental patterns& These patterns will then be used to view specific

insects within their environment$ and whether the habitat and se of the organism have any

correlation to developmental alterations& These differences will then be tied bac to the effects of

human urbanization changes on the species as a whole&

Materials:

100 Acheta domesticus cric ets of two wee s

old 5obtainable from pet shops$ herpetological

stores$ and fish bait dealers6&

Two ten gallon tan s 5or plastic tubs6 with

ventilated lids 59ne will be used for the

simulated natural environment while the other

for the simulated man made environment6

=eat +oss 5*nough to give two inches of substrate for one of the two ten gallon tan s and

one inch for the other6 >ried sphagnum moss 5for holding moisture6

%arge branches 5for climbing6



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*nglish 'vy or some other ind of vine that can survive in relatively low light 5'vy used

for this e periment in small amounts6

*gg cartons

!ewspapers

ardboard tubes from paper towel rolls 5optional6

arrots 5Should be able to be replenished twice a wee 6

>andelion %eaves 5*nsure that there are no pesticides6

%eaf litter 5optional and not used for one tan in this e perimentation6

BTrashC items such as cut open plastic water bottles$ old pieces of cardboard$ glass and

paper waste 5ensure that there are no contact with chemicals6

/ basement room with controlled temperature at 2- degrees elsius and a room with the

temperature of the BoutsideC world 5Such as a dec or patio6

9ne dozen earthworms 59btained from a store which sell bait for fishing6

Two dozen pillbugs 5*nsure that they are collected from an area without e posure to

chemicals and pesticides6 58or complete chemical safety$ they can also be bought from

stores6



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Photographs of My Setups

Procedures

1& Start by layering the peat moss 5one inch for man made and two inches for natural6

2& =lace the branches into the tan designated for BnaturalC

,& =lace sphagnum moss on top of the peat moss 5+oisture holder6

4& /dd a ;00m% of water and mi up substrate until moist&

;& /dd decorations such as the branches and ivy to ma e it loo more natural

.& =ut in the earthworms and pillbugs into the natural tan and wait at least two days for the

creatures to settle in before adding food and cric ets

-& >o not moisten the Bman madeC tan & 'nstead$ add the substrate and the BtrashC items

along with the cardboard tubes and other materials to simulate a cluttered basement

environment&

@& Set the Bman madeC into a basement area and the BnaturalC in a porch or some other area

directly affected by outside temperatures


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11& 9bserve daily$ record daily and add new carrots and dandelion leaves two to three times a

wee depending on cric et activity 5ensure there is always a supply of food6

12& "atch for signs of growth within the cric ets& / lac of feeding means that they are ready

to molt and grow&

1,& Deep notes and observations until the cric ets die off of old age

Observations of Individuals within the Simulated Natural Habitat

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/ppro imately three dozen of the small sized cric ets were added into the ten gallon enclosure

for the natural habitat& >ue to a space restraint$ ' will be initializing the two separate contains at

different times& The cric ets entered the enclosure and soon began to settle down& Some

individuals began loo ing for natural hiding places behind the logs while other individuals began

crawling about loo ing for food& 't too less than five minutes before the ma)ority have found the

leaves with which to feed upon& /fter the initial twenty minutes of feeding and grooming$ the

ma)ority of the house cric ets began to climb into and around the branches and plants which line

their enclosures& 9thers begin obtaining moisture from the sphagnum moss which lines the

bottom of the tan & So far$ no mortalities have occurred& 't will most li ely be a few days before

they start molting and growing& 8or the ne t few days$ the cric ets e perienced rela ed

composure and fed well alongside the pillbugs and earthworms within the enclosure& There is

some competition between these two other species and some cric ets have to often chase away

others in order to obtain food& This went on for a few days until the end of wee one& 9nly about

two individuals$ most li ely the individuals who obtain the largest amount of food$ molted&

Wee ":



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ompetition between both cric ets as well as their tan mates rose for many of the growing

cric ets began a search for food& Though ' ensured that there will always be enough dandelion

leaves for the A domesticus and other organisms to feed on$ the natural tendency for the species

to uarrel can easily been seen& >ominance between larger individuals over the smaller ones can

be viewed& They now were more active during the dus and midnight hours as the individuals all

had a basic understanding of their environment& (y the end of wee two$ about


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>uring wee s ; 10$ the ma)ority of the cric ets only ate and grew in size& !one of them

e perienced anything unusual or anything out of the ordinary& The ma)ority now is feeding out of

schedule but continues to compete with pillbugs for the same sustenance& Those individuals

which were smaller continued to stay small and their growth are often slower than the larger

individuals& 'n the end$ it can be assumed that this simply is )ust natural selection at wor 5#nli e

nature however$ there is enough food to go around even for the small individuals which in the

wild would have been dead due to a lac of nourishment6&

Wee !"

The ma)ority are now at the penultimate stage of their lives$ which means one more molt before becoming adults& /t this time$ many have also started to camp and not feed a sign that they are

about to mature into adults& Some of the smaller individuals$ which grew at a slower pace due to

competition$ ta e this opportunity to feed&

Wee !#

(y wee 1,$ about @0 percent of the cric ets have become adult& +any have )ust been freshly

molted at this stage and are still waiting to dry completely& Some were removed and separated

for observation& Fenerally$ they tend to be docile but many are still )umpy& 't seems as though the

ma)ority of the males matured earlier than the females and were already starting to call by the

time the females were ready to mate&

Wee !(

/ll the cric ets have now died of old age& / few of the specimens will be stored in -0E

isopropyl alcohol for measurement&



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Observations of Individuals within Simulated Man&made Habitat

Wee !

ric ets put into the Bman madeC enclosure to simulate an indoor environment& 'ndividuals

scattered in search of food and hiding spots&

Wee "&(

Similar to the events which occurred in those individuals ept in the natural environment&

?owever$ due to the controlled heat$ about


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*ata +ollecting and Processing

Crickets for

Natural

Crickets forManMade

Crickets for

Natural

Cricketsfor Man

Made

Crickets for

Natural

Crickets forManMade

Cricketsfor

Natural

CricketsforManMade

Size(mm)

Size(mm)

Size(mm)

Size(mm)

Size(mm)

Size(mm)

Size(mm)

Size(mm)

16 19 18 17 18 21 17 19

17 20 17 17 18 21 18 19

16 20 16 18 17 18 17 18

17 20 16 18 17 18 18 17

18 19 16 19 17 19 16 18

19 18 16 19 17 21 18 19

16 20 16 19 17 21 16 19

17 20 16 21 17 21 16 20

16 21 16 21 17 20 18 21

17 21 17 20 18 21 17 21

18 21 16 21 17 20 19 20

19 20 17 21 17 19 17 20

17 19 18 20 17 19 16 19

18 18 18 19 17 18 18 18

16 17 18 18 17 19 20 20

16 18 18 17 17 18 20 2116 18 18 17 17 18 16 20

16 18 17 17 18 17 16 21

17 18 16 18 18 17 - 21

17 19 16 19 18 20 - -

18 19 18 18 18 21 - -

16 19 17 18 18 20 - -

17 19 18 19 16 19 - -

16 20 18 18 16 20 - -

17 20 18 17 16 18 - -

5/ccuracy G7 0&;mm6



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't is important to ensure that measurements of the cric ets are from the head to the end of the tip

of the abdomen& >o not include the legs within the measurements&

,ocus on the Natural Habitat:

't appears that cric ets in the natural environment showed slower maturation as well as decreased

size& The altering temperatures$ lighting$ as well as competition with other organisms have made

the species ta e longer to reach its penultimate molt& This e tended period represents how wild

A domesticus will ta e longer to mature& Judging from the data$ it appears that wild populationsA

lifespans may also be longer than those living within man made habitat 5longer maturation time

resulting in longer lifespan6& Hice versa$ as a rule of thumb$ early maturation e uals early death&

,ocus on the Man&Made Habitat:

ric ets living within the simulated +an made habitat e pressed a faster growth rate than those

within the simulated natural habitat& 'ndividuals grew at a pace 2;E faster than that of the

average within the natural habitat& Temperatures were stable at the 2- degree range and humidity

was at .;E$ 20E higher than the average of the outside at ;4E& !o other organisms were in the

environment to compete with the cric ets 5>ry earth and open ground cannot support pillbugs6&

>ue to this$ the cric ets only needed to compete with each other& Judging by the data$ it appears

that populations living within urban environments$ especially unfinished basements$ e hibited



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shorter lifespans that those living within the wild& Shorter maturation time meant faster death for

the cric ets& ?owever$

they did grow a few

millimeters larger than

those within the

simulated human environment&

+onclusion

The e perimentation concluded during the final growth phases of the cric ets$ through three

months to adulthood$ e pressed some uni ue results& To answer the uestion on what effects

urbanization has one cric ets$ one interesting characteristic which differentiated those grown in

the temperature constant$ Bman madeC environment from those which grew up within a more

naturalistic setting is the individual size difference& /ssuming the decrease in competition

between snails$ earthworms$ and pillbugs$ there is good confirmation that having a limitless food

supply$ stable temperatures and zero competition has increased the differences in size of the

cric ets as shown within the collected data& ric ets grown in simulated natural only grew to

having an average of 1-&1mm while cric ets grown in simulated man made had an average size

of 1ifferentiation in size is one aspect speed of growth is another& ric ets raised in a

more stable environment allowed for a balanced growth pattern& "ithout the natural changes in

temperatures$ the A domesticus managed to feed$ grow and move even during colder days& To

simulate natural changes in temperature$ the cric ets living in the Bnatural habitatC were put in an

area in which the temperature changed according to the temperature outside& This temperature

change switched between highs of up to


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temperature is high& "hen there is a drop in temperature during the night$ or even during the

mornings$ cric ets are sluggish and are only limited to perching on logs in order to bas and raise

their bodily activities& ?owever$ those who lived in the basement$ with its stable -@ @0 degrees

range$ have grown at a constant rate over time& !ot only is this so$ the cric ets have also shown

size differences& The stable environment$ as well as zero competition$ has allowed them to gain

e tra nutrients from the litter around their home& 9verall$ cric ets resulted positively to the

surroundings and only seven within the natural and si within the man made environments died

before maturation&

"ith all these data points and variables in mind$ it is certain to say that human urbanization hasaffected A domesticus in uni ue ways& 8irst$ A domesticus has increased the growth rate by

appro imately three wee s$ thus allowing for faster maturation of the species& Secondly$ it has

increased the average size of the individuals living in human habitation& %astly$ it appears$ using

my e perimental data that males of the species seemed to have increased their growth rate$

breaching the final molt of the females ept in the same environment by well over two days& !ot

only does it e press that urbanization and human altercations have created changes within the

life and growth cycles of the cric ets$ but also that human interference has created a group of

Acheta domesticus with a larger average size& Though their lifespans were limited and shortened$

the cric ets living inside human habitation$ along with their larger size$ may help them avoid

predators$ escape the cold$ while still continuing to prosper away from danger& Thus$ while

human urbanization has caused death$ destruction$ and e tinction within thousands of species$ it

has fueled success within the small organism that is of the Acheta domesticus



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-valuation of Procedures

Though data within the e perimentation is pushed to ensure accuracy$ some limitations did

occur& The lac of predation$ as well as competition within the man made environment is only

best considered to be simulated to an e tent& 'n actual basements and man made buildings$ there

are most li ely different species of spider$ such as the ever common wolf spiders$ to act as

predator to the cric ets$ as well as other species

of insects li e coc roaches which compete with

them also& Similarly$ testing only A domesticus

and no other species greatly limits the accuracy

of the e perimentation& "hile A domesticus

certainly is a great organism$ other species of

cric ets may react differently& To add on$ even A

domesticus may respond differently in different States and locations around the world& The

difference in body size may also be contributed to negative factors such as genetics and rearing&

>ue to the large gene pools of insects$ it is hard to completely avoid BbadC traits despite selective

breeding& /s with any e periment$ more trials with different cric ets obtained for different

locations may help further yield different results&

.he Importance of /nderstanding +ric ets and .heir 0ehavioral +hanges

(iology is much greater than )ust loo ing at diversity& "ith increased human activity$ habitat

destruction$ pollution$ and human urbanization$ many species of animals are pushed to the

B%imits of Itheir *nduranceC 5/ttenborough %ife of (irds 1


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ability to wor with large ape predators& 'nstead$ it may be more economically friendly and

more accessible to )ust observe not what is at the top of the food web$ but what is at the bottom&

(y viewing the data recorded from arthropods and other organisms at the Bbottom$C scientists$

students and scholars are further able identify what is occurring at the top& This economically

friendly and less stressful method can allow for great development within biology$ which will

help humans better understand the planet$ its strengths and its wea nesses& >avid /ttenborough$

one of the most well nown (( presenters of natural history$ described this necessity at the end

of his last episode of the TH series$ BThe %ife of (irds&C ?owever$ the concept$ if switched from

birds$ applies also to the many ignored organisms of the undergrowth: /rthropods once ran asape predators on the land$ the air$ and even deep$ blue oceans& !ow$ humans have ta en over the

land$ the sea and the s ies& "ith Bs ill$ and care$ and nowledge$C 5/ttenborough 1


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Sources:

/damo$ S&/& and ?oy$ K& K& 1


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"al er$ Thomas& Qhouse cric et /cheta domesticus 5%innaeus6&Q house cric+et Acheta

domesticus 3innaeus4 . Version 1. University of Florida n.d. !eb. 1" #an. "$1%.

Documents

The Effect of Human Urbanization on the Growth And Development of the Acheta domesticus