Takahiro IRIE, Ph.D

The University of Tokyo:
Atmosphere & Ocean Research Institute
Fish Population Dynamics Section
(Room 570)

e-mail: irie[at]aori.u-tokyo.ac.jp


Research Interests:

My study is to apply mathematical approach to the quantitative information about life history of marine organisms. Currently, I'm trying to develop and improve the mathematical models and statistical methods, helpful in the resource analysis of marine organisms. My research since schooltime is concerned with understanding the life history evolution of marine ectotherms. My approach is threefold: hypotheses are established to explain the spatial and/or temporal patterns in life-history and morphological traits quantified through (1) field observations such as a quadrat-based survey or mark-recapture sampling. These hypotheses are tested both theoretically by constructing and analyzing (2) mathematical models and empirically by conducting (3) laboratory rearing experiments under controlled conditions.

Larval ecology linking life history and biogeography


In marine gastropods there is a life history spectrum from the direct development species without dispersal ability to the indirect development species with a long-time planktonic stage, as well as the poecilogonic species with both types of strategy. It is impossible to individually trail veligers (= planktonic larvae of gastropods) in the field, because they are so minute and show a wide range of dispersion for a long time in the ocean. This leaves a lot of mysteries around the larval ecology. This project aims to establish the framework for estimating the thermal record experienced by a planktonic larva, based on the data from rearing experiments of planktonic larvae and trace element analyses of protoconchs. I will also construct a mathematical model to calculate the mortality risk before settlement, using the relationship between temperature, body size, and dynamic energy budget. Furthermore, a DNA library of the focal species will be prepared for the future, finer-grained approach to quantify the genetic population structure by the next-generation RAD sequencing.

Population Size Estimation From Neutral Genetic Information

In conservation ecology and fishery science, there is a strong need to improve the estimating techniques for wild population sizes of marine organisms. Current estimation methods have problems with both accuracy and precision, because of heavily relying on fishery-derived data, collected non-randomly. A new technique based on the neutral genetic information of randomly sampled individuals across generations is expected to be the next generation alternative. This procedure is referred to as the Close-Kin approach, in which the numbers of parent-offspring pairs (POPs) and half-sibling pairs (HSPs) are assumed to be the metrics of population size. These kinships are quantified by comparing neutral allele frequencies (e.g., those at SNPs) by means of the RAD-sequencing. However, no statistical procedure has been established yet to estimate population size from kinship information. This project aims to establish a hierarchical Bayesian model to compute the posterior distribution of wild population size from the numbers of parental and offspring samples, POPs, and HSPs.

Geographic Variations of Shell Morphology in Cowries

I am focusing on cowries (Gastropoda; Cypraeidae) characterized by explicit determinate growth; somatic growth accompanied by coiling a fragile shell during the juvenile stage, which is followed by depositing calcareous materials on the lateral exterior during the callus-building stage until sexual maturation. Some intertidal species in genus Monetaria exhibit remarkable latitudinal variations; i.e., adult body size increases and callus thickness decreases with increasing latitude. These macrogeographic patterns are robust in M. caputserpentis, but the body size cline is masked by microgeographic patterns in M. annulus. My recent findings suggest that these variations reflect the spatial and/or temporal heterogeneities of environmental temperatures; these species mature at a smaller size at higher ambient temperatures, according to the temperature-size rule.

Adaptive Significance of the Temperature-Size Rule

Ectotherms often exhibit smaller adult body size with faster growth when reared at higher temperatures. This phylogenetically widespread trend is called the temperature-size rule (TSR) and evolutionary ecologists consider it has an adaptive significance. Exceptionlly, some species do not follow the TSR. Specifying the determinant of whether an ectotherm follows the TSR or not must be important in understanding the mechanism by which the TSR has been evolutionally maintained. Recently, I proposed a hypothesis that calcifying ectotherms may defy the TSR when getting bigger at cooler environments does not pay off, because calcium carbonate is more soluble at lower temperatures and the calcification cost increases with decreasing temperature. As a result, calcifers may mature at a smaller size with very slow growth at lower temperatures. Currently, I am analyzing a mathematical model to theoretically specify the conditions for the TSR being broken according to this hypothesis.

Evolutionary Response to Ocean Acidification

There is serious concern that increasing atmospheric CO2 partial pressure causes ocean acidification, by which both aqueous carbon dioxide and hydrogen ion concentrations increase and carbonate ion concentration decreases. Acidified seawater can have a deleterious effect on the physiology of various taxa of calcifying organisms. Among these organisms, coccolithophores (calcifying algae) are under intense study because they are one of the most important producers of calcite and hence play a pivotal role in global biogeochemical cycles. Accordingly, I am working on a theoretical approach by constructing an optimality model for coccolithophorid life history and analyzing its environmental dependency as a result of adaptation to acidified conditions.

Application of Dynamic Optimization to Life History Theory

The dynamic optimization is a mathematical technique for solving the minimization / maximization problme of an evaluating function in terms of the optimization of time series. This study is based on the Pontryagin's maximum principle, which is a principal tool providing analytical solutions in the optimal control theory. Our model considers an organism with determinate growth, consisting of soft body and external shell. Before sexual maturation, resource is allocated between both conponents for growth at each moment of ontogeny in a given ratio. We consider that natural selection optimize the time series of the allocation ratio by maximizing the lifetime reproductive success of an individual. Entire resource is used for reproduction after sexual maturation. Our model optimize the length of growth stage (i.e., timing of maturation) as well. As a result of analysis, we found that this model can explan well the observed diversity in the growth pattern of molluscs.

Spatial Autocorrelation and Pseudoreplication

Pseudoreplication is an annoyance for empirical ecologists working on benthos. Ecologists often run statitical hypothesis tests on the data obtained from experiments or field surveys. Many models assume the statistical independence in the random term; pseudoreplication arises when this assumption is violated. In practice, it frequently occurs when experimental design is misspecified or when autocorrelation is inherent in (unobservable) environmental variables. I'm providing information on the prevention and considering the post-hoc coping technique of this problem.

Curriculum Vitae:

Born: 1980 (Yokohama). Nationality: Japan.
1996-1999: Keio High School (Yokohama; Japan).
1999-2003: Kyushu University, Department of Biology (Fukuoka; Japan). Bachelor of Science.
2003-2005: Kyushu University, Department of Biology,
Mathematical Biology Laboratory.
Master's Degree in Science.
2005-2008: Kyushu University, Department of Biology,
Mathematical Biology Laboratory.
Doctoral Course; JSPS Research Fellow (DC1).
Ph.D (Science).
2008-2011: University of the Ryukyus, Tropical Biosphere Research Center (Sesoko Station).
JSPS Research Fellow (PD).
2010: University of Amsterdam, IBED
(from March 2010 through December 2010).
2011-2013: Stanford University
Department of Biology
JSPS PD Fellow for Research Abroad
2013-2014: The University of Tokyo
Atmosphere and Ocean Research Institute
International Coastal Research Center
Division of Coastal Ecosystem Restoration
Marine Science Specific Cooperative Researcher
2014: Fisheries Research Agency
National Research Institute of
Far Seas Fisheries

Research Assistant
2014-: The University of Tokyo
Atmosphere and Ocean Research Institute
Resource Population Analysis Laboratory
Assistant Professor

Refereed Publications:

21. 2016, Takahiro Irie and Naoko Morimoto. Intraspecific variations in shell calcification across thermal window and within constant temperatures: experimental study on an intertidal gastropod Monetaria annulus. Journal of Experimental Marine Biology and Ecology 483: 130-138.
20. 2015, Kozue Nishida, Atsushi Suzuki, Rryosuke Isono, Masahiro Hayashi, Yusuke Watanabe, Yuzo Yamamoto, Takahiro Irie, Yukihiro Nojiri, Chiharu Mori, Mizuho Sato, Kei Sato, and Takenori Sasaki. Thermal dependency of shell growth, microstructure, and stable isotopes in laboratory-reared Scapharca broughtonii (Mollusca: Bivalvia). Geochemistry, Geophysics, Geosystems 16: 2395-2408.
19. 2015, Shouji Houki, Tomohiko Kawamura, Takahiro Irie, Nam-II Won, and Yoshiro Watanabe. The daily cycle of siphon extension behavior in the Manila clam controlled by endogenous rhythm. Fisheries Science 81: 453-461.
18. 2013, Shun Ohki, Takahiro Irie, Mayuri Inoue, Kotaro Shinmen, Hodaka Kawahata, Takashi Nakamura, Aki Kato, Yukihiro Nojiri, Atsushi Suzuki, Kazuhiko Sakai, and Rovert van Woesik. Calcification responses of symbiotic and aposymbiotic corals to near-future levels of ocean acidification. Biogeosciences 10: 6807-6814.
17. 2013, Takahiro IRIE, Naoko MORIMOTO, and Klaus FISCHER. Higher calcification costs at lower temperatures do not break the temperature-size rule in an intertidal gastropod with determinate growth. Marine Biology 160(10): 2619-2629.
16. 2011, Mana HIKAMI, Hiroyuki USHIE, Takahiro IRIE, Kazuhiko FUJITA, Azumi KUROYANAGI, Kazuhiko SAKAI, Yukihiro NOJIRI, Atsushi SUZUKI, and Hodaka KAWAHATA. Contrasting calcification responses to ocean acidification between two reef foraminifers harboring different algal symbionts. Geophys. Res. Lett. 38: L19601.
15. 2010, Takahiro IRIE, Kazuhiro BESSHO, Helen S. FINDLAY, Piero CALOSI. Increasing costs due to ocean acidification drives phytoplankton to be more heavily calcified: Optimal growth strategy of coccolithophores. PLoS One, 5(10): e13436.
14. 2010, Takahiro IRIE. Adaptive significance of the temperature-size rule. Japansese Journal of Ecology, 60(2): 169-181 [In Japanese].
13. 2010, Naoko MORIMOTO, Yasuo FURUSHIMA, Masayuki NAGAO, Takahiro IRIE, Akira IGUCHI, Atsushi SUZUKI, and Kazuhiko SAKAI. Water quality variables across Sekisei Reef, a large reef complex in southwestern Japan. Pacific Science, 64(1): 113-123.
12. 2009. Azumi KUROYANAGI, Hodaka KAWAHATA, Atsushi SUZUKI, Kazuhiko FUJITA and Takahiro IRIE. Impacts of ocean acidification on large benthic foraminifers: Results from laboratory experiments. Marine Micropaleontology, 73: 190-195.
11. 2009, Takahiro IRIE and Klaus FISCHER. Ectotherms with a calcareous exoskeleton follow the temperature-size rule - evidence from field survey. Marine Ecology Progress Series, 385: 33-37.
10. 2008, Saki HARII, Naoko YASUDA, Mauricio RODRIGUEZ-LANETTY, Takahiro IRIE, Michio HIDAKA. Onset of symbiosis and distribution patterns of symbiotic dinoflagellates in the larvae of scleractinian corals. Marine Biology, 156: 1203-1212.
9. 2008, Takahiro IRIE and Naoko MORIMOTO. Phenotypic plasticity and sexual dimorphism in size at post-juvenile metamorphosis: Common-garden rearing of an intertidal gastropod with determinate growth. Biological Bulletin, 215(2): 126-134.
8. 2007, Takahiro IRIE and Ben ADAMS. Sexual dimorphism in soft body weight in adult Monetaria annulus (Family Cypraeidae). Veliger, 49(3): 209-211.
7. 2007, Kazunori YAMAHIRA, Maiko KAWAJIRI, Kenichi TAKESHI and Takahiro IRIE. Inter- and intrapopulation variation in thermal reaction norms for growth rate: Evolution of latitudinal compensation in ectotherms with a genetic constraint. Evolution, 61(7): 1577-1589.
6. 2007, Takahiro IRIE. Phenotypic plasticity as a proximate mechanism of geographic variations: Body bize clines in ectotherms. Japansese Journal of Ecology, 57(1): 55-63 [In Japanese].
5. 2006, Takahiro IRIE. Geographic variation of shell morphology in Cypraea annulus (Gastropoda: Cypraeidae). Journal of Molluscan Studies, 72(1): 31-38.
4. 2005, Takahiro IRIE and Yoh IWASA. Optimal growth pattern of defensive organs: The diversity of shell growth among molluscs. The American Naturalist, 165(2): 238-249.
3. 2003, Takahiro IRIE and Yoh IWASA. Optimal growth model for latitudinal cline of shell morphology in cowries (genus Cypraea). Evolutionary Ecology Research, 5(8): 1133-1149.
2. 1997, Ken-Ichi HOSAKA, Takahiro IRIE and Tomoyuki SUGIMURA. The family Cypraeidae (Caenogastropoda) of Yamaguchi Prefecture, western Japan. The Yuriyagai: J. Malacozool. Ass. Yamaguchi, 5(1):127-183.
1. 1997, Takahiro IRIE. Relationships between geographic variation of shell structure and water temperature in Cypraea caputserpentis (Gastropoda: Cypraeidae). The Yuriyagai: J. Malacozool. Ass. Yamaguchi, 5(1):17-29.
Final updata: 2016.9.1