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Fruit Fly News Guest of Honour - Interview with Professor Keng Hong Tan
Introducing myself
While writing-up my master thesis, I was very fortunate to be offered a scholarship to undertake my Ph. D. programme (Nov. 1970 – July, 1973) at the prestigious Imperial College of Science and Technology, University of London. After completing the programme, I returned to Malaysia to take up an academic position in the University of Sciences, Penang, Malaysia, where I initially served as a Lecturer (5 years), an Associate Professor (11 years), a Professor (5 years) and ultimately a Senior Professor until obligatory retirement, even though I was offered research positions in two countries.
As a swan song prior to retirement, I assisted in a) the organisation of two International Meetings held in Penang, Malaysia\– i) the International Conference on Area-Wide Control of Insect Pests, May 28 – June 2, 1998; and ii) the Fifth International Symposium on Fruit Flies of Economic Importance June 1-5, 1998; and b) edited the IAEA sponsored 782-page Joint Proceedings of the two International Meetings entitled; “Area-Wide Control of Fruit Flies and Other Insect Pests” published in 2000.
Group photo of participants in the Fifth ISFFEI held in Penang, Malaysia,1998
Fruit Fly research collaborators. Left to Right – K.H. Tan, S.L. Wee, R. Nishida and Alvin Hee
Initially, I was eager to learn biochemistry and physiology during my undergraduate days. For my M. Sc. research project in the Department of Zoology, University of Malaya, I chose the cave-cockroach, Pycnoscelus striatus to study its reproduction. I found i) both sexes, accumulated sufficient fat and when starved from adult emergence for over a month (in individual isolation) they could mate and females produce viable nymphs via ovoviviparity; and ii) a papaya diet (instead of its normal ‘guano’ food) during nymphal stages would induce production of long-winged males instead of the normal short-winged males with abdominal dorsum exposed. For my doctorate programme, I continued with a ‘stored product’ moth, Ephestia kuhniella, in which males could be induced by certain chemicals to undergo ‘permanent copulation’ caused by neuroendocrine disruption. This phenomenon was independently reported in the New Scientist (l972) vol. 55: p.7l – “A dastardly way to limit moth population”; and (1975) vol. 65: p.766 – “Permanent copulation is an end to the species”. These further encouraged me to investigate effects of ‘semiochemicals’ in the reproduction and control of insects. In addition, in 1980, I took up a challenge to determine the actual role of methyl eugenol (ME) as a male lure to tephitid fruit flies, as experimental organisms. That was when I switched from working on moths to fruit flies.
The most proud of in my career, being able to contribute via collaborative research
It is strange to say, as an entomologist, that I am most proud of in my research career is being awarded the “Lifetime Achievement Award” by Asia-Pacific Association of Chemical Ecologists for research into chemical ecology of fruit flies and Bulbophyllum orchids. In addition, through international collaboration, I am especially proud of our discoveries as follows:
A male Bactrocera albistrigata on a solitary flower of Bulbophyllum hortorum. The flower possesses fruit fly attractants - raspberry ketone and cue lure (CL) as major and trace components, respectively. N.B. First known case of natural CL in nature.
b) Identified the actual chemical (first reported case in year 2000) in the floral fragrance that is responsible for attracting pollinators such as male tephritid fruit flies belonging to the Tribe Dacini;
c) New fruit fly male-attractants, particularly zingerone (a phenylbutanoid), and β-carophyllene (a sesquiterpene) – the latter specifically attracts Bactrocera correcta.
d) Discovered a natural source of cue-lure (long known as a synthetic chemical and not found in nature) in flowers of an orchid species – Bulbophyllum hortorum.
A solitary flower of Bulbophyllum macranthoides subspecies tollenoniferum.
People who inspired me most
a) The late Professor Thaddeus Mann, Director, Agricultural Research Council's
Unit of Reproductive Physiology and Biochemistry, Cambridge University, for his
encouragement to conduct in-depth study on insect reproduction;
b) The late Professor Kenji Mori for his encouragement in conducting research
related to chemical ecology, and advice to achieve international recognition;
c) Professor Frank H. Haramoto, Department of Entomology, University of Hawaii
at Manoa, USA for his contributions to biology and ecology of the Oriental fruit
fly; and my temporary appointment as a Visiting Professor in his department;
d) Dr. Jorge Hendrichs, Joint FAO/IAEA Division, IAEA, Vienna, for his
assistance and commitment to help and résolve the taxonomic issue encountered
related to certain putative sibling species in the B. dorsalis species complex.;
and last but not least
e) Professor Ritsuo Nishida, a dear friend, for his endless inspiration and
encouragement as well as his dedicated commitment in our genuine research
collaboration (for 35 years) into the chemical ecology of fruit flies and
Bulbophyllum orchids.
Participants of IAEA-CRP on Resolution of Cryptic Species Complexes
of Tephritid Pests to Overcome Constraints to SIT Application and
International Trade. Left to Right: in Brisbane,
Australia. in Tucuman, Argentina, in Vienna, Austria
Things I wanted to achieve/complete but I
did not manage to Since Professor R. Nishida, an excellent organic chemist, retired from Kyoto
University, I am keen to seek assistance of a dedicated organic chemist who is
interested to analyse ‘head-space’ volatile extracts collected, on a half-hourly
basis, from newly bloomed orchid flowers. This is to determine a) the volatile
component(s) besides ME in the floral fragrance that attracts wild male fruit
flies throughout the day in the presence of traps baited with relatively huge
quantities of ME; and b) how and when a flower with less than 1 mg of ME could
attract a significant number of wild males away from the ME-traps, thereby,
might affect ‘mass trapping’ or the ‘male annihilation technique’ in the control
of fruit pests . Two foreseeable problems one may encounter are a) that
daciniphilous Bulbophyllum species releasing floral ME may bloom seasonally or
irregularly; and b) research funding. Thus, failing to get a dedicated organic
chemist to assist in this study, the idea may have to be abandoned. What I have got planned for my retirement In my third decade of retirement from teaching in a university, I plan to
take more vacations to be closer to nature. Nevertheless, I will still continue
with my passion to do some investigations related to fruit fly pollination
ecology, especially on how a dynamic lip mechanism of an orchid flower helps in
the selection of a right-sized fly (weight of fruit flies vary from 5 to 21 mg)
to remove the orchid’s pollinia (packages of hard capsule containing thousands
of fine pollen grains – with a combined weight ca 2 mg). I envisage that to
conduct these kind of investigations will require a few more of my twilight
years. Places where I would like to go with my family on vacation After the current pandemic is officially declared over, we (my wife – L.C.
Sim and I) would like to revisit either Kyoto or Hawaii for a short vacation. My best foreign destination Vienna, Austria, where I have been to almost a dozen times to attend IAEA and
IPPC meetings, and still have very fond memories of my visits, despite my only
experience of carry-on baggage being snatched while purchasing a train ticket
after arrival from Vienna airport. My advice to fellow students and researchers To my younger collaborators please continue with innovative and
international collaborative research, to maintain an utmost integrity in
scientific publications/reports. We have raised issues related to
misinterpretation and misinformation in certain scientific publications - let us
continue to believe that “the truth will always prevail” even when under the
darkness of political upheavals, fake news and discriminations. My suggestions for improving the international cooperation on fruit
flies On fruit fly research: Although the fruit fly fraternity had resolved the
issue related to four (former putative) pest fruit fly species as a single
species, I think there are a few taxonomic issues related to both fruit flies
and daciniphilous Bulbophyllum (orchid) species that require international
cooperation to resolve them amicably. Therefore, my suggestion is certain United
Nations and/or funding agencies would take a ‘lead’ role to improve
international cooperation for open discussions in order to resolve the taxonomic
issues (based solely on morphological characters) via an integrated approach
using DNA sequencing, phylogenetical, chemoecological techniques etc, for the
sake of humanity and science. This highlights the timely need for improved
cross-discipline research in attaining the United Nations Sustainable
Development Goals (UNSDG).
My next favourite foreign destination is Bonn, Germany, I made several trips
accompanied by wife to spend quality time with our daughter, son-in-law and
granddaughter. When time and physical health permit after the current COVID-19
pandemic, we would like to visit various historical sites in China.
Members of IPPC-Technical Panel on Pest Free Areas and Systems Approaches
for Fruit Flies (TPFF) (2004-2018)n
On fruit fly collaboration: Though almost 15 years into my teaching retirement,
I still had the privilege of being appointed to serve as a member of the First
Tephritid Workers of Asia, Australia and Oceania (TAAO) Steering Committee. I
observed a great deal of enthusiasm and willingness in cooperation amongst
members in the committee. From my experience, this is a good start to an effort
that must be creatively and proactively sustained.
Delivering keynote lecture for the First
Symposium of TAAO in 2016 In addition, thanks to rapid
advances in communication technology, the pace of networking is very much faster
than before. Therefore, I am proud of the active networking that I observed
between our regional groups led by Dr Marc De Meyer (TEAM), Dr Teresa Vera
(TWWH) and Dr Alvin Hee (TAAO). This effort must be sustained for our younger
generations as one big global fruit fly community.
Participants of First Symposium of Tephritid workers of Asia, Australia
and Oceania (TAAO) held in Putrajaya, Malaysia (August 15-18, 2016). The most interesting/important discoveries I made about fruit flies
during my career In my humble opinion based on the quote: “Nothing in biology makes sense
except in the light of evolution” by T. Dobzhansky, my team made three important
discoveries related to Dacini fruit flies:
Bactrocera Scientific Advisory Panel of California Department of
Food & Agriculture
(Left to Right) A. Malavasi, S. Quillici, K. Hoffman,
S. McComb, B.C. Dominiak, T. Teruya, E.B. Jang and K.H. Tan
Thank you very much to all fruit fly workers and friends particularly, A.
Clarke, S. Ekesi, D. Haymer, A.K.W. Hee, J. Hendrichs, E. B. Jang, A. Malavasi,
R. Nishida, H. Ono, R. Pereira, J. Royer, T. Shelly and S.L. Wee) for their
encouragement, and friendship as well as dedication to the fruit fly fraternity. Best wishes and regards to all.
a) Methyl eugenol (ME), a male lure, is a sex pheromone ‘precursor’. It is
bio-transformed to chemical components in male Bactrocera dorsalis. The volatile
components when released simultaneously act as sex pheromone, and aggregation
pheromone to form a ‘lek’ as well as an allomone to deter predation by
vertebrates.
b) In a span of 18 years starting from 1994, my collaborators and I have
published works showing that the following four putative species B. dorsalis, B.
papayae, B. invadens and B. philippinensis were actually one and the same
species – B dorsalis.
c) In the natural ecosystems of the tropics there are no “pest” fruit fly
species as they are also important beneficial insects that are exclusive
pollinators for many orchids, especially daciniphilous [attracting fruit fly
species belonging to the Tribe Dacini in subfamily Dacinae (Tephritidae)]
Bulbophyllum orchids. My current field tests show that these orchids, especially
those releasing floral ME, may affect the use of male lures in the fruit fly
surveillance, mass trapping and MAT (male annihilation technique).
Merry Christmas and a Happy New Year!
K.H. Tan