Download Gorillas: an example of an issue report

Conservation work done for endangered gorilla populations.
Introduction
One of the main objectives of London Zoo, which is where my field visit was, is part of the
Zoological Society of London, modern zoos list their main roles as: to provide education, carry out
field work, perform scientific research, form global links with other zoos and to participate in
conservation.
Mountain gorillas
There are two sub-species of Eastern lowland gorilla, the eastern gorilla
and the mountain gorilla. The mountain gorilla has to main populations
on in the Virunga volcanic mountains of Central Africa and the other in
Uganda's Bwindi
Impenetrable Forest.
After chimpanzees,
gorillas are our
closest relatives and
share about 97.7% of
our DNA. Gorillas are
the largest living
primates, an adult
male weighing up to
180 kilograms (400
pounds), with an arm
span of about two meters (seven feet). It is estimated (by www.awf.org) there are currently fewer
than 700 left in the wild
The significance of Genetics in Gorilla conservation
The problem for ZSL is if there is a large enough population to support a viable breeding population
of mountain and lowland gorillas, and if some are bred what are the chances of them successfully
reintegrating into the wild? An important consideration is that no mountain gorillas have survived in
long-term captivity (www.informatics.org/gorilla/gorilla.html), so their only option is to preserve their
natural habitat and maintain a healthy gene pool for the next generations. However lowland gorillas
can be bred in captivity and hopefully released to the wild.
Conservation societies like ZSL face many difficulties in protecting and enlarging gorilla
populations. They have identified the problem that the rearing of young into adulthood is a very
slow process; the gestation period of a gorilla is normally 8-9 months while the infant would be
dependent on their mother for around 4 years, during this time the mother would have to be
monitored and protected. This is too slow and so Zoos have taken the measure to participate in
captive breeding programs to boost the number of gorillas. When doing this Zoos map their
breeding individual's genetic lineage so as to avoid any chance of inbreeding. Though this can be a
problem as the numbers in the wild and in captivity are low and they are made even lower as not
all animals are suitable, some may be too old others may not yet have reached sexual maturity. If it
is decided a founder group has to be created, these are the individuals of the species who form the
core of the gene pool, qualities that have to be taken into account include:
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An animal's health and general well being; it was shown in the zoo that flocks of flamingo
will not breed unless they are surrounded by several others.
An animal's behaviour and temperament; animals selected for breeding cannot be
aggressive in case they injure their mates.
Maintaining an appropriate age structure for the group.
Appropriate male to female ratio; mountain gorilla groups usually have one dominant male.
As genetically diverse as possible parents; this is usually the most difficult aspect as
endangered species will have few unrelated individuals.
This will give the off-spring the best chance of survival, as genetic complications will have been
avoided and the species' larger gene pool prevents detrimental genes becoming widespread. While
inbreeding can be beneficial by increasing desirable features, as is done in dog breeding, it
reduces genetic diversity. Alleles (an alternative for a gene) are lost when inbreeding occurs (7).
Also genetic disorders caused by recessive alleles may become more prevalent, so it is overall
important to maintain a species genetic diversity.
Societies like ZSL spot that gorillas have very specific social structures and dynamics. They affect
the territories that gorillas follow, they are usually guided by the dominant male, and it stipulates
the order of mating in the group, so these are taken into account in the zoo and when considering
implementing breeding projects in the wild.
Social and economic implications affecting conservation.
A big reason that brings the animals into conflict with humans is poaching. Local tribesmen trap the
animals and hunt the animals for mainly two reasons; one is for their meat (bush meat) the other is
for body parts to be sold as traditional medicine or souvenirs. The hunters that do this are usually
poor, 85% of farmers in the surrounding region, Congo, Rwanda and Uganda, are subsistence
farmers (they only produce crops for their own consumption). So they are in dire need of the
money. But their countries have banned this, making the hunters lawbreakers and forcing them into
black-markets. In other words a potential solution to a social problem has actually made the
situation worse. Another issue the zoo faced in helping gorillas and indeed all the other animals
they are involved with is finance. All this conservation costs money which has to be met by the
ZSL. To help towards this they charge admissions to centres like the London Zoo and Whipsnade.
The effect of loss of habitats on biodiversity
Biodiversity is the diversity of species, ecosystems and genes that exist on earth. The ZSL is a
conservation society and maintaining the world's biodiversity is a main aim of theirs. There are
several forms of biodiversity and being aware of each helps in allowing ZSL to concentrate their
efforts:
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Species Diversity: the sheer numbers and kinds of plants, animals, and other forms of life that
share our world - and the interactions between these species.
Ecosystem Diversity: the habitats where these plants, animals, and other organisms live and
evolve-and the interconnections between them.
Genetic Diversity: the inherited traits that distinguish one species from another.
Cultural Diversity: the mosaic of human cultures that both influence and are affected by the
natural world.
However there are limitations to this information as species diversity relies on knowing accurately
the number and types of species. Taxonomy (classification of species) is vital to this. However
scientists are aware that there is still large numbers of species (especially fungi and bacteria) that
are yet to be discovered.
Food webs describe the feeding relationships between species to another within an ecosystem.
They are complex and intricate networks where species are inter-dependant. Species in higher
trophic levels are dependent on producers in the lowest tropic level for their energy. So when
food webs are disrupted by humans burning forest, damming rivers or releasing
pollution, biodiversity is affected. The change may make certain species less able to compete
and so lose out to other species. As a consequence species diversity and ecosystem diversity may
be altered. This effect may cascade to other areas and this is something conservation
organizations like the ZSL are trying to prevent.
Social and environmental implications.
Human population growth
10000
9000
Population (millions)
8000
7000
6000
5000
4000
3000
Religions like Christianity have the
view that Christians should consider
themselves to be stewards of God's
creation. In other words they should
protect what they believe God has
given them. This means they want to
protect the environment and maintain
species and their habitats.
2000
Human development like urbanization
has encroached on animals' habitats.
0
This has reduced the areas they can
1500
1600
1700
1800
1900
2000
2100
Year
feed and reproduce in. It has also
brought them into contact with
humans and while this is not always detrimental (as in the case of pigeons) it changes the dynamic
of the species' biodiversity in that area. In fact, the % of gorillas remaining in the wild is almost a
mirror image of the human population graph shown above (data from
http://en.wikipedia.org/wiki/World_population ).
1000
The biology involved in conserving gorilla populations.
Conservation societies like the ZSL view breeding programs as a good method in conserving
gorilla populations. Breeding programs use stud-books (which are an official list of animals within a
specific breed whose parents are known) to track individuals so that inbreeding is prevented and
genetic diversity is maintained.
When considering genetic diversity it is important to consider how it arises so that it can be
implemented in the breeding of gorillas. Every gorilla is slightly different from one another, this
partly due to differences of their phenotypes (the observable trait of a gene) and environmental
factors. For example a gorilla may have a genetically predisposition to have a tall and large frame,
but environmental factors such as poor nutrition may limit the individual's growth.
A very important source of genetic diversity is crossing over during meiosis 11). When
two unrelated individual gorillas are mated they will each provide half the number of chromosomes
(the diploid number of gorillas is the same as humans; 46) the haploid number 23. Gorillas are
similar to humans, we share 97%-98%of our DNA, and we both produce gametes to reproduce, the
egg and sperm.
(11) The process of crossing over of genes to produce gametes:
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Chromosomes replicate to double their numbers.
They then pair up to form homologous pairs.
These pairs then exchange information where they make contact called chiasmata.
The homologous chromosomes separate, the cell divides leaving a pair of chromosomes in
each cell.
The chromatids separate and cell divides forming 4 gametes with 23 chromosomes, the diploid
number.
Conservationists want to make the offspring they create to have as good a chance as possible of
surviving in the wild. The genetic diversity created gives rise to new genotypes and these may
create new phenotypes in the population. These new phenotypes may allow the species to be
better able to adapt to small changes in their habitat. There are differences between lowland and
mountain gorillas. As they inhabit different areas that have different selection pressures on them.
The lowland gorillas have evolved to be more slender and agile to allow them to move faster
through grassland and climb trees. This shows how phenotypes have become evident due to
changes in the habitat.
Genetic diversity can also arise from mutations, point mutations, addition mutations etc. The
mutation can be germ line mutations, which can be passed on to descendants, and somatic
mutations, which are not transmitted to descendants. ZSL would be more interested in germ line
mutations as these can be given to offspring and can add genetic diversity to the species. But
mutations are usually unfavourable; examples in humans include cystic fibrosis, FOP and
Huntingdon's disease, however natural selection will ensure that only beneficial or neutral
mutations are passed along.
There are two main sub-species of gorilla (as of 2008), the Western gorilla and Easter gorilla.
These are able to produce fertile offspring so they are members of the same species. Ecological
isolation (the sub-species occupy different areas) has probably given rise to the difference between
the two sub-species. Conservationists could try and breed individuals from the same sub-species
to try and keep intact phenotypes while still introducing new alleles into the gene pool. What is
more likely, due to the small numbers of suitable individuals, any two individuals are breed. This
may lead to future generations becoming mixtures of the two sub-species, as heterozygous
genotypes become more prevalent in their genome. If that matters or not, depends on how
precisely conservationists like ZSL want to conserve a species; ie. does that include conserving
sub-species as well?
Alternatives for the future
IVF treatment
Zoos breed gorillas using conventional methods, such as bringing them physically together in order
for them to breed. This method is however very unreliable, gorillas may dislike one another and
conflict may arise or one or both may be physically unable to procreate. So conservationists
decided to apply developments in human IVF treatment to animals like the gorilla.
"Research studies using animal gametes led to the first documented human IVF in 1969" (12) the
first human IVF was able to happen as animal testing first took place. It is therefore logical that this
procedure can be applied to animals, and as gorilla physiology is similar to humans (97%-98% of
the same DNA) the procedure can successfully be used on them.
An outline on how human IVF is carried out.
In an IVF Procedure, the doctor:
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prescribes hormonal medications to stimulate the ovaries,
gathers the eggs,
fertilizes the eggs in vitro (outside the body),
transfers the resulting embryos through the cervix into the
uterus
An example of successful insemination of gorillas is Ya Kwanza: “The silverback was born in
Melbourne Zoo in 1984/ He was also the first silverback gorilla to be conceived by artificial
insemination anywhere in the world" (12). This shows that artificial insemination is possible in
helping to breed new gorillas, but how effective is it in helping to conserve them?
Human IVF success rates are "21.8 per cent of IVF treatment cycles resulted in a birth" (13). These
are very low success rates and IVF treatment is expensive. Gorilla artificial insemination also has
low success rates "A modified method for insemination is described which has resulted in a 21%
success rate" (14).
New methods have been developed to get this increased 21%successrate. Research has been
conducted into factors which determine successful insemination: "sperm preparation, site of
insemination, and timing of insemination" (14) and disinfection procedures for gametes and
embryos. The research has allowed IVF to become a tool for conservation but "Artificial
insemination in the great apes has not achieved its potential as a tool in maintenance of the
endangered captive population" (14).
A new procedure for collecting sperm from male apes could be used. Electrical stimulation can
be used to make gorillas ejaculate. Nerves can be stimulated using electrical signals and by a
process of trial and error it may be possible to develop a method in which sperm can be efficiently
collected. Collected sperm can be frozen and put into sperm banks. From a conservation point of
view, this may in the future ensure that enough genetic diversity is present for the species to
survive should numbers diminish.
Chromosome selection developments
"Gorillas at the North Carolina Zoo will soon be part of a
ground breaking animal reproduction research project, if all
goes as planned. The zoo's three female gorillas are
potential participants for an in vitro fertilization (IVF)
program that would supplement the species' natural
mating."(15) This project is called, "Assisted Reproduction
Using Sex-Sorted Sperm".
The procedure itself involves scientists separating gorilla
sperm into x and y-bearing cells (notice the XY of the
chromosomes shown – data from
http://en.wikipedia.org/wiki/Chromosomes ). Having
determined the sex of the embryo being put into the female gorilla, researchers thereby determine
the sex of the resulting offspring. This opens up important possibilities for the future for gorilla
conservation. Gorilla social groups consist of one dominant male and a large number of females.
This leaves many young males who have to be kept separate in their own enclosures, and this is a
problem for zoos like London Zoo. It is the sperm that determines the sex of the offspring, XX for
female and XY for male (10) (shown in the punnet square below).
X
(male sperm)
Y
(male sperm)
X
(female egg)
X
(female egg)
XX
XX
XY
XY
This would allow conservations to pick the gender of the embryo that will be made from the
gametes. However in humans there are genetic conditions like ‘de la Chapelle syndrome’ (XX male
syndrome). "Usually it is caused by unequal crossing over between X and Y chromosomes during
meiosis" (10). The chance of this is small but it highlights that this new method may not provide the
answer conservationists seek as genes have many functions and interfering with them may have
serious consequences. Many features are polygenic and so their effects are hard to predict as
many genes are involved to certain extents, however the research may provide other as of now
unexpected benefits.
Evaluation of sources' validities.
An important source I used was source (11: the SNAB textbook. It was published by Heinemann
publishers which was founded in 1890 and is known for publishing educational books (16). The
book has been used in class and has been referenced by me, classmates and my teacher.
Being commercially published it has been scrutinised and checked repeatedly by professionals, so
it is as accurate as possible. Science however is always progressing and theories in the book may
be in the process of being proven wrong. Also as the textbook is intended for an A-level student the
information in it is simplified to be easier to understand and at times this may leave gaps in
information or at other times it may simply be incorrect to allow AS students to understand.
An example of information I took from the book is meiosis. I took extracts and applied it to my
report, however I also found other sources that had more information in them and showed some of
the lack of depth the book offers.
Source (10) states that "Occurrence of meiosis in eukaryotic life cycles / Leptotene,
Zygotene, Pachytene, Diplotene Diakinesis" an area book does not cover in much depth.
The IVF success rate data, source (13), gave two different success rate values, one for women
over 38 and one for women below. If there is so much variance for humans applying it too gorillas
undermines its validity. Other sources like (17) give the value as 25% and 10% for over 40s.
Source (13) also comments on its own data by saying it "accepted that there was great variation in
the success rates of different clinics..."Most critically regarding its validity is the fact that the data
was published in 30 August 2002. This is several years ago and techniques will have improved by
then, as shown by source (17). However for an illustrative purpose it is suitable, but its figures
cannot be taken as being completely valid.
Source (12) is a news website and not a scientific website. It gives no references to support its
claims and the objective of the article is entertainment. The writer may have only limited scientific
knowledge and may be relying on secondary sources to write his article. As I cannot verify the
information's provenance I should not place much weight to its claims.
Source (10) is Wikipedia; it is a free online encyclopaedia. It is maintained and updated by
volunteers that visit the site. This however means that anyone with internet access can edit the
information in the articles. To function the site requires references to be provided and other visitors
can highlight any incorrect information. Although for it to be completely valid its information should
be reiterated in other sources. The article on gorillas is backed up by 20 references, such as:
http://www.volcanoessafaris.com/gorilla_diet.html,
http://www.philadelphiazoo.org/index.php?id=3_1_1_9 and
http://www.shsu.edu/~his_ncp/Hanno.htmI. Still when using the website common sense is paramount
in helping to avoid clear inaccuracies in the text.
Source (7) is an in-depth article on inbreeding. It is written in a very balanced approach both the
pros and cons are discussed and all the points are laid out concisely and relevant biological detail
is included with each point.
Source (5) and Source (10) both back up the claims in source (7), so the points it makes are valid.
However the article mainly focuses on domesticated animals like dogs and horses and only leaves
a footnote for wild animals like the cheetah. While the genetics will be relevant to gorillas as all
these animals are mammals, the fact that gorillas are not the article's focus bring in a slight degree
of discrepancy. Overall the article is a good example of the effects of inbreeding, due to its many
examples and sound biology.
Bibliography
www.edgeofexistence.org -a website listing facts regarding the 100 most endangered animals.
www.awf.org – African wildlife foundation, information and facts on African wildlife.
www.google.co.uk
www.informatics.org
(5) cc.ysu.edu/~helorime/inbred.html – a scientific article on inbreeding.
www.newscientist.com/article.ns?id=dn6920
www.un.org/ecosocdev/geninfo/afrec - A UN site about Africa.
(7) www.messybeast.com/inbreed.htm - Website on the results of inbreeding.
www.nczoo.org/press/view.cfm(10) http://en.wikipedia.org/wiki/ ( these include the following subsections: Gorilla, meiosis,
mutations, Jersey Zoo, XY sex-determination system)
(11) 2005, Salter’s-Nuffield Advanced Biology AS textbook, First Edition, Heinemann Publishers,
ISBN0435628577
(12) www.bbc.co.uk
http://www.ingentaconnect.com/content/repro/rebi/2002/00000004/A00101s1/art00011
(13) http://www.hfea.gov.uk/en/969.html
(14) http://www3.interscience.wiley.com/cgi-bin/abstract/110487398/ABSTRACT
(15) www.nczoo.org/press/view.cfm
(16) http://wapedia.mobi/en/Heinemann - (book publisher)
(17) http://www.babycentre.co.uk/preconception/fertilitytreatments/ivf/?_requestid=1191701#8
NB. Some ‘visuals’ and graphs are not included because of copyright reasons.