DIWPA: DIVERSITAS in the Western Pacific and Asia

DIWPA News Letter
Office: Center for Ecological Research, Kyoto University, Otsu, Shiga, Japan

August2022

No. 47

Message from the Secretary General

Message from the chairperson

Shin-ichi Nakano

Atsushi Ishida

I hope all of you are well during the period of theCOVID-19 pandemic since 2020. CER (Center forEcological Research) has concluded MoU with ResearchCenter for Limnology and Water Resources (RCLWR),
National Research and Innovation Agency (BRIN),
Indonesia. To make the MoU more active, Dr. Luki
Subehi, Head of research group “Hydrodynamics andBiogeochemical Processes of Inland Waters Ecosystem”
of RCLWR, has been staying at CER since July 22, 2022.
He has successfully got the grant of JSPS for one monthstaying at CER. During his stay, he is going to conduct
some analyses on Indonesian fish samples and discusswith me about future collaboration between Indonesianand Japanese limnologists/aquatic ecologists. He gave atalk about “Overview and finding unique characteristics
of various tropical lakes in Indonesia” on July 29 at CER.
As you know, the Republic of Indonesia consists of manyislands, and each island has many lakes where some/many of them are still pristine and unexplored. To
conserve their ecosystem and biodiversity, and to havetheir better management of fisheries, IndonesianGovernment should collect limnological, ecological andfisheries information about the lakes as much as possible.
Limnologists and aquatic ecologists in Indonesia havebeen conducting a lot of studies on the lakes.
Unfortunately, however, they encounter difficulties tocollect data due to limited man-power and shortage offinancial resources. In Luki’s talk on July 29, heintroduced the status quo of Indonesian lakes: lakes withunique ecosystems, eutrophication, cyanobacterial
blooms, aquacultures and so on. We were very much
impressed with his talk that we would need more researchon those lakes having their precious ecosystem andbiodiversity.

Since the early July 2022, we have been experiencing the7th of COVID-19 infections caused by the Omicron
variant in Japan. No one knows when the 7th wave willsubside. Due to the infections, we have not held DIWAPInternational Field Biology Course (IFBC) during the last
two years, unfortunately. Because the covid vaccination isproceeding forward in Japan now, we try to hold DIWPAIFBC in this year, although there is a possibility that it
may be cancelled due to the situation of COVID-19
infections. We are unable to predict not only the infection
situation in Japan but also the visa acquisition at thattime. According to this situation, we will hold the DIWPAIFBC in 2022 for foreign young students and/or
researchers who are staying in Japan at the time ofOctober 1, 2022. Please understand that we unfortunately
cannot invite them from abroad in this year. Despite thecircumstances, we are pleased to be able to resume theDIWPA IFBC. In this year, we are planning to hold theDIWPA IFBC in the Ogasawara (Boini) islands, a World
Natural Heritage site in Japan. See more details inpage6-7 in this DIWPA Newsletter.

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DIWPA News Letter No.47

Overview and Finding UniqueRe

1Characteristics of Various Tropicaltr
poLakes in Indonesia
Luki Subehi
Research Center for Limnology and Water Resources,
National Research and Innovation Agency (Indonesia)

Indonesia is listed among the 12 megadiversity
countries, ranked as the first in Asia in the number offreshwater fish species. As the settling of water volume,
it harbors many species of fish communities. Moreover,there are 5,807 inland waters (lakes and reservoirs) in
Indonesia, covering about 586,871.64 ha of area. Tropicalinland water is one of the unique ecosystems which areusually functioning in both ecological and economicservices. Recently, there is an increasing need to conserveand maintain the ecological balance of inland water
systems which are subjected to massive pressure.

eutrophication, highly reduced quality and quantity ofwater; (2) Lake utilization: Hydropower plant,
agriculture, fisheries (aquaculture/floating cage), usable
water, religious and culture values, tourism (includinglake uniqueness, accessibility, amenity-infrastructure andsociety condition); (3) Local government’s and society’s
commitment to wisely manage lakes (master plan, local
regulation, managing committee); (4) Strategic lake:
lakes featuring strategic functions of national interest;(5) Biodiversity (including endemic fish species, avesand vegetation); and (6) Carbon urgency (the challenge
against global climate change).

The water resources problems and someeffort to solve them

Challenges ahead
Besides Indonesia has a largest caldera lake (Lake Toba,1,130 km2 area) in North Sumatra and the deepest
tectonic lake (lake Matano, 590 m depth) in South
Sulawesi, there are also more than 300 oxbow lakes inKalimantan Island and some saline lakes (salinity morethan 40 ppt) in the eastern part of Indonesia (RoteIsland) (Figs.1 and 2). To protect them, the capabilitiesof the economic values of these inland waters andecosystem should be balanced. In order to maintain thesustainability of the lakes, basic ecological informationis necessary for the next study.

Generally, the inland water problems in Indonesia are as
follows: (1) Change of land use and land covers:degradation of forest land; (2) Water pollutions andenvironmental qualities; (3) Decrease in water resources
availability; (4) The lake basin management challenges;
and (5) Eutrophication as threat to lake water resources
degradation. Concerning the degradation and environmental
damage, especially in Indonesian lakes, the government
makes the national Indonesian priority lakes as a part of
the focusing and integrating all roles of institutions toprotect those lakes. Some criteria of priority lakes are:
(1) Lake damage: Level of sedimentation, pollution,

LAB GIS - LIPI

Fig. 2. Lake Oemasapoka – the saline lake in Rote
Island (The most southern part of Indonesia)

Fig. 1. Lake Hanjalutung – the Oxbow lake in Central Kalimantan

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DIWPA News Letter No.47

Re

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tr
po

Causes and consequences of hostmanipulation by parasites in ecosystems
Takuya Sato
Center for Ecological Research,
Kyoto University (Japan)

Understanding the energy flow through food webs is afundamental issue in ecology because the energy flow
regulates the food chain length, strength of the trophic
cascade, and biomass distribution of food webs, which
ultimately maintain biodiversity and ecosystem
functions. Historically, studies have largely overlooked
parasites because they are not obvious and thought to be
unimportant in food web energetics. However, parasites
consist of approximately 40% of known species (Dobsonet al. 2008) and their biomasses are even larger thanthose of top predators in some ecosystems (Kuris et al.
2008). We now know that parasites are ubiquitous innature, but still have limited examples of how parasites
play roles in ecosystems.

known example of the “extended phenotype” (Dawkins1999). A noteworthy example is found in nematomorph
parasites (“horsehair worms”, Phylum Nematomorpha:
Family Gordiidae) that inhabit globally, from boreal totropical regions (Poinar Jr 2008). Larval nematomorphs
mature inside a terrestrial invertebrate host,manipulating the host to seek and jump into water so theworm can emerge as an aquatic adult. Infected hosts
wriggling at the water surface invariably attract aquatic
predators, such as fish and frog. Sometimes predators eat
the hosts before the nematomorph can emerge but theworm often escapes through the predators’ gills or mouth(unlike many parasites, nematomorphs don’t parasitize
the predators of their hosts) (Ponton et al. 2006). We
previously quantitatively demonstrated that orthopteranhosts (camel crickets and some predatory katydids; Fig.
1) that jump into water contributed 60% of the annual
energy intake of stream salmonids in a temperate
Japanese forested stream (Sato et al. 2011) (Fig.2).

Manipulative parasites as a cryptic driver ofecological processes
A wide range of parasites manipulate the behaviors of
their hosts in order to complete their life cycle, in a well-Fig. 1. A camel cricket Diestrammena sp. infected bya nematomorph parasite Gordionus sp.

Fig. 2. Trophic interactions and ecosystem functions modi ed by a prey subsidy mediated byparasites. Black arrows, except for the cricket-trout link, denote direct consumptive interactions; thethinness of arrows shows the strengths of each interaction. The upper graph shows the seasonal
dynamics of potential prey abundances for stream salmonid sh around the study site (Sato et al.
2011). Terrcricket and Terrothers represent cricket hosts and other terrestrial invertebrates, respectively.

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DIWPA News Letter No.47

Clearly, streams are not typical orthopteran habitats.
Therefore, such cross-ecosystem energy flow (i.e., theenergy utilized by a consumer in an ecosystem isgenerated in the other ecosystems) would be less likely
to occur without host manipulation by nematomorphs.
Furthermore, the cross-ecosystem energy flow mediatedby the nematomorphs indirectly decreased the predationof aquatic invertebrates by salmonid fish, which in turnweakened the trophic cascade and increased the leafdecomposition rate in the stream ecosystem (Sato et al.
2012) (Fig.2).

grassland/ foliage reflecting sunlight or moonlight. Thus,a simple alteration of the positive response to lightintensity may not be enough for hosts to effectively findwater and jump into it. Contrary to the previous studies,
we recently solved the mystery by focusing on“polarized light”. The reflection of sunlight off water
bodies is horizontally polarized, which is uniquepolarized light in nature and is used by many arthropods
to either seek out or avoid water habitats (Heinloth et al.
2018). In the two-choice experiment, arboreal mantids(Hierodula patellifera) infected by nematomorph
parasites (Chordodes sp.) were attracted to horizontally
polarized light but not to vertically polarized light,
whereas uninfected mantids were not attracted to either(Fig.3A). In a field experiment, most of the infectedmantids (14 out of 16 mantids) entered a deep pool(Fig.3B), where the water surface strongly reflectedhorizontally polarized light (Fig.3C). By contrast, only 2
mantids entered a shallow pool (Fig.3B), where thesurface reflection had higher light intensity but weakerpolarization (Fig.3C). This is the first study
demonstrating that a manipulative parasite can takeadvantage of its hosts’ ability to perceive polarized lightstimuli to alter host behavior (Obayashi et al. 2021).

Solving a mystery: How parasites manipulate
their hosts?
A series of our researches are one of the best examples
of how parasites can have large ecological impacts
within and across ecosystems. However, there is amissing piece for the researches; the key mechanism
triggering the hosts’ entry into water has long been
wrapped in mystery. A previous study reported thenematomorph-induced positive phototaxis, which may
increase the encounter rate of hosts and water bodies(Ponton et al. 2011). However, luminous environments
are ubiquitous in nature, such as right sandy habitats orFig.3. Induced positive polarotaxis and water entry of Hierodula patellifera infected by Chordodes sp. (A) Proportions of infected anduninfected mantids that located the horizontal polarization third in the choice experiment at four different light intensities; number ofmantids used in each treatment (infection status and light intensity) is shown on right side of each bar. (B) Overview of the eld experimentand the number of infected mantids that jumped into each pool. (C) Polarization images of the water surfaces of each pool; left pool (reddishsurface) strongly re ected horizontally polarized light, whereas right pool (blackish surface) re ected less polarized light. In a color chart
synthesized with angle of polarization (AOP, left bar) and degree of linear polarization (DOLP, right bar), color indicates angle of polarization
direction, and brightness shows degree of polarization. The polarization images were taken at an angle of 35°, from which the infected
mantids often jumped into the water.

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Conclusions
Animals have evolved a diversity of photosensitive visualsystems, which allow them to detect intensity, color,contrast and polarization of light (Kooi et al. 2021).
During their co-evolution with those animals, parasites
might have evolved to take advantage of the diversevisual systems of their insect hosts to enhance the hostmanipulations. Therefore, our finding of parasite-induced
positive polarotaxis may be one of many examples ofhost manipulation strategies in illuminated environments.
As a next step for our research, we are currently
uncovering molecular and neural mechanisms behind theenhanced polarization, which may ultimately help tounderstand temporal and spatial variations in energy flow
mediated by the nematomorphs.
References
Dawkins R. 1999. The extended phenotype: The long reach of the gene. Oxford
University Press.
Dobson A., Lafferty K. D., Kuris A. M., Hechinger R. F. and Jetz W. 2008. Homageto Linnaeus: How many parasites? How many hosts? Proceedings ofthe National Academy of Sciences 105:11482-11489.
Heinloth T., Uhlhorn J. and Wernet M. F. 2018. Insect responses to linearlypolarized re ections: orphan behaviors without neural circuits.
Frontiers in Cellular Neuroscience 12:50.
Kooi C. J. v. d., Stavenga D. G., Arikawa K., Belušič G. and Kelber A. 2021. Evolutionof Insect Color Vision: From Spectral Sensitivity to Visual Ecology.
Annual Review of Entomology 66:435-461.
Kuris A. M. et al. 2008. Ecosystem energetic implications of parasite and freeliving biomass in three estuaries. Nature 454:515-518.
Sato T. et al. 2021. Enhanced polarotaxis can explain water-entry behaviour ofmantids infected with nematomorph parasites. Current Biology
31:R777-R778.
Poinar Jr G. 2008. Global diversity of hairworms (Nematomorpha: Gordiaceae) in
freshwater. Hydrobiologia 595:79-83.
Ponton F. et al. 2006. Parasitology: parasite survives predation on its host.
440:756.
Ponton F. et al. 2011. Water-seeking behavior in worm-infected crickets andreversibility of parasitic manipulation. Behavioral Ecology 22:392.
Sato T. et al. 2012. Nematomorph parasites indirectly alter the food web andecosystem function of streams through behavioural manipulation of
their cricket hosts. Ecology Letters 15:786-793.
Sato T. et al. 2011. Nematomorph parasites drive energy ow through a riparian
ecosystem. Ecology 92:201-207.

Mail Us!
We welcome your articles,
news or any information related tobiodiversity.
Please send them todiwpa@ecology.kyoto-u.ac.jp

flfl5DIWPA News Letter No.47

2022 DIWPA International Field Biology Coursein Ogasawara Islands will be held!!

YLPAP !!
NOWDIWPA Office is pleased to announce that we will have DIWPA International Field Biology Course(IFBC) in this autumn for the first time in three years. However, there are still difficulties in opening thegate to foreign researchers/students from abroad because of COVID-19. Thus, for this 2022 DIWPA
IFBC, we can accept only foreign young researchers/students residing in Japan at the time ofOctober 1, 2022. We ask for your kind understanding.
DIVERSITAS in the Western Pacific and Asia (DIWPA) is an international network for the promotion ofcooperative studies and information exchange on biodiversity in the Western Pacific and Asia whichaims to connect existing networks of people working on biodiversity and research projects in Asia andthe Western Pacific. One of the main functions of DIWPA is “capacity building of scientists in particularyoung scientists from developing countries”. In the autumn of 2022, the International Field Biology
Course will take place in the Ogasawara Islands, a World Natural Heritage site, in Japan.
DIWPA accepts an application for a scholarship to attend the International Field Biology Course.
Details
1.

Date and schedule:
10:00 a.m. November 17, 2022 (PCR test at Takeshiba ferry terminal in Hamamatsu-cho, Tokyo)
November 18-23, 2022 (6 days trip)・At JR Hamamatsu-cho station in Tokyo at 10:00 a.m. on November 17 for PCR test
・At Takeshiba ferry terminal in Hamamatsu-cho at 10:00 a.m. on November 18 for boarding
・IFBC will break up in Takeshiba ferry terminal at approximately 15:30 on November 23.

(There is a possibility that the arrival time of ship in Tokyo delays due to sea conditions.)
2.

Accommodation and Station :Chichi-jima island (Research station of Tokyo Metropolitan University)

3.

Site:
The islands are in Pacific Ocean, 1,000km south of Tokyo. The climate is subtropical and thearea of Chichi-jima island is 24km2.

4.

Financial support:
DIWPA provides a scholarship to cover his/her expenses for accommodations and travel fromTakeshiba ferry terminal in Hamamatsu-cho, Tokyo. Please cover the cost of the trip to/fromTakeshiba by your own.

6DIWPA News Letter No.47

5.

Application:
Applicants should be talented researchers/graduate students who belong to DIWPA or whose
supervisor is the DIWPA member.
Applicants should prepare the following documents.
(1) CV(2) Inform whether you need to stay at a hotel in Hamamatsu-cho (Tokyo) in the night on
November 16, 2022. Note that you must take the PCR test at the ferry terminal in themorning on November 16. If not, your boarding will not be allowed.
(3) A statement of their interests in the field of ecology(4) A recommendation letter written by the supervisor

6.

Application submission and deadline:
Submit applications to DIWPA office by e-mail before September 11, 2022.
DIWPA Office : diwpa@ecology.kyoto-u.ac.jp

7.

Others:
It takes 24 hours in one way between Tokyo and Chichi-jima island by ship. There is a
restaurant in the ship, but you need to pay some money when you use it. Some researchersand students will use the accommodation together. A shower room and a kitchen are sharedby the accommodation members. We are unable to guarantee 100% for sure to correspondhis/her food restrictions or other matters for the religious reasons, though we would positivelywork on these matters as much as possible. Just before getting on the ship, your bodytemperature will be taken. If it is too high, you will not be allowed to board. Please be awarethat this IFBC may be suddenly cancelled due to the situation of COVID-19 infections andtyphoon or sea conditions. And your cancellation fee for a ferry will be charged if you call off
your attendance at the IFBC at your convenience after October 31, 2022.

Only successful candidate(s) will receive the details by September 16, 2022
by e-mail.
If you have any question, please feel free to contact us.

DIWPA OFFICE
Chairperson

Shin-ichi, Nakano

Secretary General

Atsushi Ishida

SecretaryHiroshi Kudo
Shoko Sakai
Shigeo Yachi

Center for Ecological Research
Kyoto University509-3, 2-chome, Hirano, Otsu, Shiga 520-2113, JAPANTel : +81-77-549-8238
E-mail : diwpa@ecology.kyoto-u.ac.jp
http://diwpa.ecology.kyoto-u.ac.jp/

Assistant Secretary Akiko Seki

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DIWPA News Letter No.47