ダニが語る生物多様性～寄生生物の進化的重要単位の意義～
Mites Talk about Biodiversity - Ecological Significance of Evolutionarily
Significant Units in Parasites.
独立行政法人 国立環境研究所 侵入生物研究チーム・五箇 公一

Koichi GOKA, PhD, Invasive Alien Species Research TeamNational Institute for Environmental Studies

Hello everybody. I am Koichi Goka of the National

As I mentioned just now, parasites played a major roleInstitute for Environmental Studies.

in the evolution of sex according to an idea known as“the Red Queen’ hypothesis”. One of many current ideas

First of all, I must apologize in advance to those ofconcerning evolution, the hypothesis takes its nameyou listening in English because I was late presenting

from the character in Lewis Carroll’s second “Alice”

my slides and the script of my speech is too long. This

book, Through the Looking-Glass, and What Alice Found

means I will have to speak so fast that the simultaneous

There. In the story, the Red Queen says, "It takes all theinterpreters may not be able keep up. So please readrunning you can do, to keep in the same place." Heremy English subtitles where they appear.

the Red Queen is used as a metaphor for the idea thatspecies, individuals and genes have to keep evolving if

Also, as I have a great many slides please regard mythey are to survive. In order for multicellular species

presentation as if it was an animation.

to keep warding off continual attacks by viruses, thespecies needs to be equipped with sufficient variation

At the request of Prof. Murata I am going to talk aboutat the genetic level. Clearly, there is a difference in themites and ticks which are my specialty subject. In

tempo at which evolution can take place in viruses andparticular, I intend to focus on biodiversity as seen

in multicellular organisms consisting of an enormous

through the study of mites. At the same time, I’d likenumber of cells. So if multicellular organisms were toto explain in an autobiographical manner about why I

counter the attacks of viruses by means of ordinary

turned towards the study of mites and why I love them.

mutation alone, they would never be able to win
the evolutionary battle. Instead, they have evolved

In today’s workshop we have been hearing about

as a result of gene exchanges and the creation ofvarious kinds of parasites, including mites. Parasites are

new genotypes through sexual reproduction. This

organisms that have existed almost since the beginning

hypothesis is one of several that attempts to accountof life on Earth. Ever since that time they have evolved

for the evolution of sexual reproduction.

together with the rest of the biosphere. Parasites
attach themselves to other living things in order toParasites have various ways of making a living. Forlive and, as you are probably aware, there is a theory

example, some kinds of organisms parasitize higherthat they played a role in the development of sexual

order organisms, while others practice kleptoparasitism.

reproduction. Many organisms have male and female

This is a photog raph of a Great Reed Warbler

individuals and reproduction between two sexes is the(Acrocephalus arundinaceus) feeding a Common

most common way in which reproduction takes place.

Cuckoo (Cuculus canorus) chick in an example of what
is known as “brood parasitism”. When we consider that36

Many kinds of living creatures, from primitiveparasitism itself is always associated with the evolution

organisms such as insects and plants to human beings,of organisms, and that some parasitic species exist

exist as male or female, as this slide illustrates.

inside almost all species of living things, parasites can

りぶ・らぶ・あにまるず 神戸アニマルケア国際会議 2012

therefore be said to play a major role in promoting

However, even though mites have very simple bodies,

biodiversity.

these animals are distributed everywhere on Earth.
Also, the life histories and food sources of different

When we think about it, we human beings are living as

species of mites are amazingly varied, and the total

the biggest parasitic organisms on the Earth, and ournumber of mite species is enormous. There are aroundstyle of parasitism creates numerous problems. But at

50,000 known species recorded at present, and it

the same time, parasitic organisms have very important

has been estimated that there may be up to a million

functions within the ecosystem. As two other lecturers

species of mites all told.

noted earlier, in a sense parasites play very importantroles, and while they are universally disliked, we also

Mite habits also vary widely. For example, somehave to recognize that their roles make them very

species even live in the ocean. In this respect, mites

precious organisms.

have gone farther than insects as no insects live in thesea. Mites can inhabit both salt water and freshwater

From this point on I am going to talk about mites.

environments where they engage in eating plants
and in sucking the blood of animals. Also, there are

My specialty is acarology (the study of mites andpredatory mites that eat other mites and there areticks), and although I am involved in a variety of work

scavenger mites. There are many varieties of mites inconcerning the preservation of biodiversity, the things

the soil which break down organic matter and convert

I actually like most are mites. Actually, there is an

it to inorganic matter which helps create a rich soil. In

organization called the Acarological Society of Japan.

these and other ways, mites are organisms that carry

And although the study of acarology is not very wellout a wide range of functions and help to support

known, there is also an International Congress of

biodiversity.

Acarology, which is held every four years. Two years
ago, I attended the International Congress of Acarology

Hearing such a story, you might very well be thinking

held in Brazil where, for an entire week I took part inthat however important mites may be as an element

happy and harmonious conversations with acarologists

in the web of life, as a human being you don’t likefrom around the world about mites and nothing but

them personally. You may wish also that mites weremites.

organisms that did not concern human life at all.
However, mites of the species Demodex folliculorum

Now, what kind of creatures are mites? Since many ofare in all probability living happily on your face. As ayou here today are specialists perhaps I don’t need tomatter of fact, almost 80% of Japanese people are hosts

explain, but many members of the general public areto this species. Of course, newborn babies don’t haveconfused that mites are insects. In fact, mites are notthese mites to begin with but when a mother rubs her

insects. The mite body is very simple. It consists of only

cheek against her baby’s face, the mites are transferred.

one section to which the limbs and mouth are directly

In this way, every human family has its own mites that

attached.

are passed down the generations. So please bear inmind that mites are an excellent part of biodiversity as

The insect body is separated into three sections,a whole.

the head, thorax and abdomen, with six legs andup to four wings attached to the thorax. That’s the

Now I will proceed with my own story. I will explain

insect archetype. So insects have a far more complex

about why I started to research the subject of mites instructure than mites do. Like spiders, mites have eightthe first place. When I was a student in the Department

legs. But the spider body is divided into two sections,of Agriculture at Kyoto University, I chose spider

cephalothorax and abdomen, so spiders also have amites as my research subject. These are a family of

more complex structure than mites do.

herbivorous mites that parasitize plant leaves. From the

2nd Live Love Animals International Conference on Animal Care in Kobe 201237

human standpoint spider mites are a terrible problem

available, the more mating the male will perform. Givenbecause they get onto various plants and suck thethe opportunity, a male will keep mating whenever andjuices from the leaves. They eventually kill the plants

wherever it can until the point where it almost dies ofand cause major problems as a worldwide agricultural

exhaustion. I totally got into mites as living organisms

pest.

that embody the male’s fate as it is. I earned a master’s degree and a PhD by studying mites and after that

Regarding their living environment spider mites begin

went to work for a pesticides manufacture where I waslife as eggs and go through several stages before

involved in developing miticides.

reaching the adult stage. They exist as males andfemales and reproduce sexually. Mating between males

At that time too, in the battle between mites andand females is effective only one time. When a female

miticides, we found that no matter how many types

engages in mating, her semen tank becomes full withof miticide we produced, they would soon lose their

the result that subsequent mating is ineffective. So

effectiveness. We investigated many things related

for males, the obtaining of virgin females is a very

to spider mites including their DNA and came to theimportant breeding strategy. In view of this, the kindconclusion that spider mites encompass a huge rangeof behavior spider mites have evolved includes pre-of diversity and that they maintain their resistance bymating guard behavior. The male climbs onto a female

continuously evolving. From this, I realized more clearly

pupa before the adult stage and guards it. Then, as the

how important biodiversity is. In any case, the miticides

female starts to cast off the chrysalis, the male helps

we developed didn’t sell well, and the company where I

out, and then performs mating immediately. This is thewas working declined. So I left that company and joined

spider mite’s reproductive strategy.

the research institute where I am employed now taking
up work on the preservation of biodiversity.

Given this state of affairs, virgin females are a very
precious asset for the males. If another male comes

My initial research work at the institute was on thealong, the result is a fight. Two males will enter into

subject of alien species control, and I am still mainly

a violent combat that involves fencing using theirinvolved in this work. The first alien species I worked

stylet-like mouthparts. (These mouthparts are usually

on was the Buff-tailed Bumblebee (Bonbus terrestris),

employed to suck the juices out of plants). Often thewhich was imported to Japan from Europe.

fight continues until one kills the other and while they
are engaged in this battle, a third male may come along

This species of bee has been bred commercially for use

and mate with the virgin female. This kind of thingin pollinating tomatoes and other crops in greenhouses.

occurs quite often.

A species native to Europe, the Buff-tailed Bumblebee
has been imported to Japan in large numbers. As you

38

In my student days, there was a laboratory class during

can see, the beehives are installed in greenhouses inwhich we could observe these things taking place

this way, and the bees fly around carrying pollen andthrough a microscope. I first got into mite researchcarrying out the pollination tasks that previously had

when I saw these things. I was very impressed that mite

to be performed by the farmers themselves, while

ecology was so graphically revealing of the meaning ofsignificantly improving the tomatoes’ productivity inreproduction.

the process.

There was another experiment in which we observed

However, some of these bees of European origin

what happens when one male is placed alone in a placeescaped from the greenhouses and began to live in thewhere there are many virgin females. The point of thiswild as an alien species, which had a very bad effect

was to test the male mites’ reproductive capabilities.

on the native Japanese Bumblebee (Bombus hypocrita

Results showed that the more that virgin females are

sapporoensis). Because of this, use of the Buff-tailed

りぶ・らぶ・あにまるず 神戸アニマルケア国際会議 2012

Bumblebee is now strictly regulated by the Ministry

analysis is that it allows us to guess at once theof the Environment to ensure that individuals of thiseffective evolutionary times of organisms such as

species do not escape from greenhouses.

different mites and bees, which may be very different
morphologically and taxonomically, because they have

While I was carrying out this ecological risk evaluationsome similar genes. This method is beneficial in that

I thought that, in importing the beehives from Europe,

we can get to know the effective evolutionary times

they must have also brought in some strange parasites.

of species by studying the genes that control identical

So I looked for parasitic mites and detected thecharacters in different species and calibration can bepresence of an endoparasitic mite species called theperformed by means of the molecular clock method.

Tracheal Mite (Locustacarus buchneri) on the bodies ofUsing this method, I located the region governingthese bees. Then I surveyed how widely these mites had

the assembly of the enzyme cytochrome c oxidase

been introduced into Japan.

in the mitochondrial DNA of both mites and bees. By
searching and analyzing the genes in this region I was

However, I discovered that the Japanese Bumblebee

able to construct an evolutionary tree for each species.

also carries this same endoparasitic mite. As a resultof analyzing the mites’ DNA, I ascertained that theIn this way, I was able to show that the evolutionary

Japanese and European forms have different DNA,trees of both species were almost exactly the same

which means that these mites also exhibit local

shape. You can see that, in the case of the bees, there

endemism.

is a clear separation and differentiation between thebees of Eurasia and Asia on the one hand and those

While conducting this research, I have paid particularof America on the other. The evolutionary tree of theattention to parasite co-evolution. Originally parasites

mites has an awkward shape as you can see. In short,and their hosts evolve in a kill-or-be-killed relationship,

the shapes of the trees of the two species do not

but when they continue in this over a long period, they

match. What this means is that we can surmise thateventually become tired out. Then they move to the next

the bees and the mites did not evolve in the same way.

step, which is a symbiotic relationship. For example,

In particular, we know that, compared with the Asianthe power of viruses becomes attenuated because theirand Eurasian bees which have undergone a great deal

hosts are able to use their immune systems to controlof genetic differentiation, the mites that parasitize

the viruses to a certain extent. Accordingly, symbiotic

these bees exhibit only a very slight degree of genetic

relationships represent the evolutionary end point ofdifferentiation.

the battle between parasites and hosts.
On the other hand, you can see that in America, theWhat this means is that, in order to prevent pandemics

mites are parasitic on only one species of bee thatand limit the disease damage that may be caused by

has no mitochondrial DNA variation, but the mites

various parasites in future, it is important to know

themselves display very active genetic differentiation.

the preexisting evolutionary histories of hosts andparasites. In other words, it is important to know

From the standpoint of diversity, in the case of Asia andwhere the original parasite evolved and where it lives.

Eurasia, the basic diversity index of the host bees is

So in the case of the Tracheal Mite, I tried to find out

0.04 while that of the parasitic mites is an order below

about its origin and how it has evolved up to now bythat at only 0.005. On the other hand, in the case ofgathering bumblebees and the mites that parasitize

America, the basic diversity index of the host bees isthem from all over the world.

zero while that of the parasitic mites is 0.05, which is
the reverse of the Asian and Eurasian situation. What

I checked the DNA of each of the types of organism I

this means is that these mites and bees have undergone

found. A convenient point about molecular phylogenetic

different evolutionary processes and their origins are

2nd Live Love Animals International Conference on Animal Care in Kobe 201239

also different.

When we examine this in more detail, we find that it isdifferentiated into the ‘big blue’ family in the northern

Basically, a lot of evolutionary research has been carriedpart and the ‘big red’ family in the southern part of its

out on the bees. They are considered to have originatedrange, and at the root of this tree is the ancestor of allin the central region of Asia and then rapidly expanded.

the subspecies of Giant Stag Beetle that exist today. In

As for the mites, from their present mitochondrial

fact, the point of differentiation occurred 5.2 million

DNA tree, they are considered to have originated inyears ago. Even species of such small insects achieve

America and, after spreading across that continent, they

genetic differentiation over time by spreading out theirswitched their hosts to bees and travelled to Eurasia.

ranges, and in the case of the Giant Stag Beetle thishas created subspecies with a history spanning more

In America this mite is parasitic on locusts so we canthan 5 million years. We call such a population an

suppose that in some way it must have switched hosts

evolutionarily significant unit (ESU). In the near future,

to bees and then newly evolved into its present form of

we will no longer be able to classify organisms merely

Locustacarus buchneri.

as species, but we must also handle them as units inwhich we consider the evolutionary history of each

When a parasite switches hosts we often focus on the

genotype and its weight.

point that introduced alien species usually have a bad
influence on native species. But actually, when alienThis next story concerns conservation. Again, I am

species enter Japan, Japanese parasites also transfer togoing to turn my attention to mites. This time, I would

these alien species and begin evolving into new forms,

like to talk about mites that parasitize beetles. There isand Japanese parasites are also capable of generatinga genus of mites called Coleopterophagus that live bypandemics on occasion.

attaching themselves thickly to the backs of beetles. I’
m sure that people who keep beetles have seen theseAn example of this is a Japanese mite that has

mites. Many beetle lovers hate them and brush them

explosively parasitized alien bees despite the fact that

off the backs of their pet beetles with considerable

this mite does not parasitize native bees very much. So

enthusiasm. Because so many of these mites attachparasites can utilize different strategies for living and,themselves to the back of a single beetle, the beetle

in many instances, they can more easily parasitize hosts

looks poorly, which is why the common Japanese namethat they have not co-evolved with.

of this mite is the ‘kuwagatanakase’, which literallytranslated into English means “beetle’s bane”.

After mites and bees, I turned next to stag beetles.
Individuals of alien species in this family are imported

However, these mites are merely scavengers. They areinto Japan in large numbers for commercial purposes,

cleaners that eat the fungus that grows on the stag

and their introduction has created problems. In Japan

beetle’s back or any waste matter that gets attached.

alone, there are many species of stag beetles, andSo actually, these are very good mites as far as thethroughout Asia the amount of speciation is greater still.

beetles are concerned. For this reason, I would advise

The beetles shown here are all of different subspecies

people who keep these beetles not to remove theof a species called the Giant Stag Beetle (Dorcus

mites. Moreover, the kuwagatanakase can only live ontitanus), which is distributed in Japan and across Asia.

the backs of stag beetles. They would die even if they

In order to know how much genetic diversity thiswere placed on some other insect or given double thespecies possesses, I made an evolutionary tree using

amount of waste to eat. For this reason, it is considered

mitochondrial DNA. As a result, I discovered that thisthat the stag beetles and the mites that live on theirsingle species encompassed a huge amount of genetic

backs have co-evolved.

diversity. This one species exhibits clear differentiationin each region and each island throughout its range.

40

りぶ・らぶ・あにまるず 神戸アニマルケア国際会議 2012

This is a close up of one of these mites. The photo will

appeal strongly to mite lovers, but if you hate mites you

have an opportunity to talk about mites, I purposefully

probably won’t be able to stand it.

put in a slide like this in an effort to educate people as
to the splendor and beauty of mites. However, theseI love mites more than beetles, so I want to know about

efforts often come to grief as the bigger I make thethe evolution of mites. Actually, these kuwagatanakase

slides, the more people say they feel sick. When I drewmites are not only found on Japanese stag beetles.

this image, I thought it was well done, so I sent it to

They also live on stag beetles all over Asia. I performed

the publisher of an international acarology journal

a search of the beetles’ DNA and, along the way, I

in the United States and they used it on one of theiralso took a great deal of interest in the sort of trivia

cover pages. The publisher was very impressed withthat only an acarologist would care about. I refer tothe image and assumed I was an artist. He invited methings such as the amount of genetic diversity within

as an artist to attend the journal’s 60th anniversary

the genus Coleopterophagus, the evolutionary history

party and requested that I bring the original image

between the beetles and the mites, and place fromwith me. I felt frustrated that I wasn’t recognized as an

where the kuwagatanakase mites originally came. In

acarologist, so I told the publisher, “I am not an artist,

order to find out as much as I could I collected stag

I’m an acarologist!” and sent them one of my papers.

beetles from all over Asia and the mites attached to

They replied, “Never mind your paper! Just send yourtheir backs as well. Using the information in their DNA

picture.” Since the party was being held in Ohio andI built up an evolutionary tree. This is a mitochondrial

it was too much bother for me to travel there, in theevolutionary tree of the stag beetle species living in

end I sent the picture after all. This made the publisher

Asia including the Giant Stag Beetle. Since the tree is sovery happy, and they turned it into a memorial postage

large, you can’t read the writing on this slide, but pleasestamp. So if you are in the United States, please look

don’t worry about that.

out for a memorial postage stamp with a mite pattern
and buy it.

In order to complete this evolutionary tree, I had to readapproximately 2,000 bases. From this evolutionary tree,

Another thing, when the COP 10 conference on

we can see that the host species has a huge amountbiodiversity was held the year before last, the Emperorof genetic diversity. And here is the evolutionary tree

and Empress visited our research institute and I wasof the mites that live on these beetles. Somewhat

one of the people guiding them around. At that time, I

surprisingly, this species’ genetic differentiation has

put a lot of pictures on the wall. The Empress showedalso progressed to a great extent. Moreover, if we try tointerest and asked me what they were. I’m sure thatlink up the relationship between the host and parasite,

up until then she hadn’t seen any big pictures of mites.

we can obtain a one-to-one relationship like this.

From that point, I became a bit hyperactive. I stopped
talking about the institute and about biodiversity

This means that the mites have not simply been drifting

and instead I talked about mites for ten minutes. The

in their evolution and their mode of living. They have

Emperor and Empress seemed very impressed and theywalked and lived together with their beetle hosts along

took one of the pictures back to the Imperial Palace

an evolutionary history that stretches back for overwith them. This became a historical monument as

12 million years. The fact that different populations of

the first picture of a mite to be taken into an Imperial

these two species have been evolving together for such

residence.

long time also indicates that these small mites also exist
as evolutionarily significant units.

Recently I appeared on TV, where I had photos ofmyself taken with many entertainers. Among them,This is a computer graphic image of a Tracheal Mite.

Shokotan (Shoko Nakagawa) took the most interest in

I do computer graphics as a hobby and I’m proud tomites. I told her a lot about how mites couple, and she

say that this image is one of my own efforts. When I

responded that she would like to see mites coupling. So

2nd Live Love Animals International Conference on Animal Care in Kobe 201241

I devoted all my time over Golden Week to completingthe species level. What has caused this? I thought it

a computer graphic image of two mites coupling. Thiswas curious that such extensive genetic exchange wasis that picture. The larger mite is the female, and thetaking place in such a limited region as Japan. So I

other one, which is holding up its bottom, is the male.

studied those individuals for which differentiation was

They take a very unusual sexual position. I gave thisparticularly pronounced, and ascertained that they

picture to Shokotan and she was very happy with it.

were all parasitic on carnations.

Moreover, when former Environment Minister Ryu
Matsumoto visited our institute, I also presented the

As these mites are specifically parasitizing carnations,same image to him, explaining, “This is a picture of two

it would be quite reasonable if they were geneticallymites coupling.” He casually brought it back with him,

homogeneous. So why was there this much genetic

but he actually had it put up on the wall of his office.

variation among them? I studied this question andSince he later resigned in controversial circumstances,

found out that most carnations are not grown in Japan

this is now a sad memory for me.

but are cultivated abroad and imported and sold as cut
flowers. These carnations are grown in many countries,

I’ve wandered off the subject, but to come back to point

and Two-spotted Spider Mites live in all of these

I wanted to make, even mites exhibit endemism andcountries. That’s the reason why there is now so muchdiversity. These days, however, with problems suchgenetic diversification among the Two-spotted Spider

as globalization and the introduction of alien species,

Mites that live in Japan.

the endemism and diversity of mites is in a criticalsituation.

In fact, I interviewed carnation farmers asking themwhere they purchased their carnations, and found that

This is a spider mite. These mites are agricultural pests.

they imported them from many countries as shown

I myself researched this both in my student days andhere. Moreover, almost all the mites that exhibit genetic

when I was working for the pesticide manufacturer.

differentiation are of foreign origin. Clearly these mites

Spider mites also exhibit endemism and diversity, andwere brought into Japan from overseas.

this is also in a critical situation. As an example, thisTwo-spotted Spider Mite (Tetranychus urticae) is one

An even more troublesome thing is that because theseof the many spider mite species and it is a serious

mites are pests, their drug sensitivities differ from those

agricultural pest on a worldwide scale. This speciesof ordinary spider mites. When exposed to miticide,comes in two color varieties—a red variety and a green

since the green type mites are very similar genetically,variety. This is a rare intra-species variation, which isthey all die straight away, and most of the red typeconsidered to be part of an on-going process of genetic

monophyletic mites, which are the main variety in

speciation. Accordingly, I have taken an interest in thisJapan, also die.

process and tried to study the degree of differentiationof the intra-species variation. And to do this I have

However, such miticides are totally ineffective against

collected red and green mites from all over Japan andthe spider mites that have been imported from abroad

Europe and analyzed their DNA.

because these mites had sufficient genetic resistanceto the miticide from the beginning. When this much

As a result, I was able to construct this evolutionary

genetic variation is so widely distributed within atree, and from it I found that the green mites became

group, there must be some mites that have resistance,

differentiated from the red mites, perhaps throughand these survive and breed.

pigment decolorization. Here, I would like to draw

42

your attention to the fact that the red mites’ genetic

Since these mites are pests, they should have beendifferentiation is unusually active even within Japan.

prevented from entering the country by means of plantIndeed, this differentiation has progressed almost toquarantine in the first place. So I investigated why so

りぶ・らぶ・あにまるず 神戸アニマルケア国際会議 2012

many things (that should have been incinerated) wereto the black list system is that the release ratio ofallowed to come into Japan. Now, the World Tradeagricultural pests has become higher. Since only thoseOrganization is aiming for global free trade and a part

species deemed to present a risk are listed, almostof that effort is the Trans-Pacific Partnership (TPP). This

all agricultural and forestry pests can now be freelyorganization, which promotes free trade, is promoting

imported.

agricultural pests as well.
The TPP, which has become a major subject of talk,Originally, the Two-spotted Spider Mite was on thepresents us with the same situation. One government

list of species for which importation into Japan was

minister has described the TPP as the ‘third opening

prohibited. However, in 2004, they were found onof the country’. Whenever the country is opened theapples imported from the United States and the apples

number of alien species increases. So if we think about

were incinerated. This provoked an angry response

protecting biodiversity in a true sense, in future, wefrom the US side, which sued Japan through the WTO.

should pay a lot of attention to this TPP argument fromThe US argument was that since the Two-spotted Spider

the ecological science and animal hygiene standpoints.

Mite already existed in Japan it was unreasonable toquarantine imports from the US on the grounds thatAs a case example, I’d like to talk about a dangerous

they harbored the mites. Japan lost this case and as amite that is brought into Japan together with imported

result, was forced to abolish the quarantine measuresliving organisms. Up to now I have been talking about

for the Two-spotted Spider Mite, allowing this species

rather mild things unrelated to human health. But

to be imported freely into the country.

what I’m going to talk about now are ixodid - hardbodied ticks - which feed on the blood of animals andThis is a very inconsistent approach. As I explained

spread various diseases. The most dangerous ones canearlier, perhaps these mites do look the same buttransmit zoonoses to humans.

they have very different genes and their sensitivity to
drugs also varies widely. Now they are freely imported.

In the current situation, there is concern that with the

And although most of us are unaware of the fact, thelarge numbers of reptiles being imported into Japanliberalization of agricultural pest species has been

and with almost all of them taken from the wild, many

proceeding apace.

kinds of ixodid ticks are being brought in with them.
What is even more troubling is that legal protections

The Plant Protection Act was finally revised in thesuch as guarantees on the safety of imported animals

spring of last year. Under the revised law, Japan has

mandated under the Infectious Disease Law by the

moved from a ‘white list’ system to a ‘black list’ system.

Ministry of Health, Labour and Welfare and animal

Under the white list system, the importation of all pests

quarantine provisions are limited to warm-bloodedthat damage plants was banned in principle. Only thoseanimals. Reptiles and amphibians can be brought into

species of insects, etc., that were on the white list (suchJapan without any guarantees at all. I was concerned

as stag beetles and unicorn beetles) were considered

about this so I began a project to study the mattersafe to import. The white list was a very strict

jointly with Prof. Kawabata of the National Institute ofregulation. By contrast, the black list system operates

Infectious Diseases. In the course of this research, as I

on the principle that all species can be imported unlesshad expected, we found ticks of the genus Amblyomma

they have been examined and specifically placed on

on turtles and many kinds of mites attached to reptiles

the black list. So only those species considered toimported into Japan.

constitute a risk are prohibited from being brought into
the country. Any species not on the black list can be

Moreover, the number of countries from where

freely imported. This is the same system as specified

these living things are imported is surprisingly large,

by the Alien Species Act. A consequence of the change

including such widely separated places as Sri Lanka,

2nd Live Love Animals International Conference on Animal Care in Kobe 201243

Tanzania, and Suriname. I wasn’t even sure of precisely

Parasites and their hosts establish peaceful andwhere some of the countries of origin were so, due

stable relations after a long period of co-evolution.

to this research, I also had an opportunity to study

Biodiversity is a cradle in which these organisms cangeography. What especially worried me was that thegrow and develop together, but it can also serve as amites themselves might be carrying some dangerous

cradle for pathogens. When human beings destroy thispathogens so I asked the NIID to do some testing. The

biodiversity there follows a collapse of evolutionary

results came back positive. We discovered the presence

history and co-evolution, and in its place, pandemicsof the bacterial genus Borrelia which can infect humans

occur. Examples of this process at work include SARS

with many diseases. I studied the genetic differentiationand HIV/AIDS. They have their respective origins inof this genus and produced an evolutionary tree. I

horseshoe bats in China and in chimpanzees in thenoticed that the genus includes a species that is the

Cameroon, and were living quietly with their hosts. The

agent for Lyme disease and a species that causes tick-reason why they turned into emerging diseases is thatborne relapsing fever. This information was so complete

humans destroyed the habitats of the hosts, allowingthat I was able to make use of it in conjunction withthe viruses to cross the species barrier. Now the viruses

the evolutionary tree. The new Borrelia bacteria weare desperately evolving in order to survive in theirdiscovered were not members of either of the above

new hosts, human beings, of which there are about 7

species. They are a totally new type. This is a very

billion individuals at present. They have already arrived

dangerous situation because nothing is clear includingin the urban jungle.

the pathogenicity and, even more troublingly, no risk
evaluation has been made of these bacteria because it

The important thing here is that, in line with thehas not been possible to grow them in isolation up to

evolutionary rule that has always been followed until

now. In view of this I have to say that, under the current

now, hosts that are infected either die or else they

free trade situation, people who want to keep reptiles

survive. Those that survive are more likely to passas pets need to seriously consider the potential risks

on their genes to the next generation. In this way,

they are taking.

succeeding generations have better resistance to theeffects of the virus and the two species gradually enter

For my own research I previously chose only visible

into a symbiotic relationship. Today, however, welarge alien species. But now I am paying attention toattempt to contain dangerous viruses by any means

invisible alien species as well. What set me off in thisavailable including the use of antiviral drugs anddirection was a disease called chytridiomycosis, another pharmaceuticals. The result is that the viruses

infectious disease of amphibians that is often fatal.

continue to evolve rapidly in response to the drugs

Perhaps you have heard of it. Chytridiomycosis is anthey are exposed to. This becomes a non-stop fightemerging disease that has spread worldwide and wiped

between humans and viruses. Only humans break thisout entire species of frogs in some places. It landed

evolutionary rule. When we consider the evolutionary

in Japan several years ago and caused considerable

history of viruses there is a high possibility that humans

uproar. I dislike frogs but I worked on this theme out ofwill lose this fight one day.

necessity, and I was shocked by my results. I don’t havetime to go into the details now, but I’d like to tell you

So, if we want to stop this fight, it is important for

about it when I get an opportunity.

humans to keep at a distance from biodiversity fromnow on. The idea of “natural symbiosis” or “living in

As Prof. Nakamura said at the beginning, the reason

harmony with nature” is often talked about. But thiswhy such emerging diseases that are close to being

does not mean it is OK for owners to kiss their pets or

zoonoses are being encountered more often now issomething like that. Humans have evolved as naked

because biodiversity is being gradually destroyed.

apes who can survive in the concrete jungle so when wetalk about ‘natural symbiosis’ it is important to apply

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りぶ・らぶ・あにまるず 神戸アニマルケア国際会議 2012

some kind of zoning between the wild world and thehuman world and to properly separate their functions.
In that sense, protecting biodiversity has anotherimportant meaning. It can serve as a means ofpreventing the expansion of emerging infectious
diseases. Biodiversity does not exist only to be
applied to beautiful living things. Even parasites areencompassed within biodiversity. So please extend yoursupport to the mites and ticks too.
【Slide 1】

That completes my talk. Thank you very much forlistening.

【Slide 2】【Slide 3】【Slide 4】

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【Slide 5】【Slide 9】【Slide 6】【Slide 10】【Slide 7】【Slide 11】【Slide 8】【Slide 12】

りぶ・らぶ・あにまるず 神戸アニマルケア国際会議 2012

【Slide 13】【Slide 17】【Slide 14】【Slide 18】【Slide 15】【Slide 19】【Slide 16】【Slide 20】

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【Slide 21】【Slide 25】【Slide 22】【Slide 26】【Slide 23】【Slide 27】【Slide 24】【Slide 28】

りぶ・らぶ・あにまるず 神戸アニマルケア国際会議 2012

【Slide 29】【Slide 33】【Slide 30】【Slide 34】【Slide 31】【Slide 35】【Slide 32】【Slide 36】

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【Slide 37】【Slide 41】【Slide 38】【Slide 42】【Slide 39】【Slide 43】【Slide 40】【Slide 44】

りぶ・らぶ・あにまるず 神戸アニマルケア国際会議 2012

【Slide 45】【Slide 49】【Slide 46】【Slide 50】【Slide 47】【Slide 51】【Slide 48】【Slide 52】

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【スライド 53】

【スライド 57】

【スライド 54】

【スライド 58】

【スライド 55】

【スライド 59】

【スライド 56】

【スライド 60】

りぶ・らぶ・あにまるず 神戸アニマルケア国際会議 2012