Hajime Ohtsuki's research while affiliated with Tohoku University and other places

Publications (27)

Article
Full-text available
How evolutionary relatedness influences the strength of competitive interactions among genetically isolated populations has been a long-standing interest in ecology. Darwin’s “Competition-Relatedness Hypothesis (CRH)” states that, since closely related species should compete more strongly, they are less likely to coexist, while Herbert’s “Bimodal C...
Article
Population genetic diversity and structure are known to influence successful colonisation and establishment of a population in a novel habitat. However, our understanding of actual population genetic changes in the early stage of colonisation and detailed time‐series of genetic changes during the establishment of a new population is still limited d...
Article
Full-text available
To verify the “nearly neutral theory (NNT),” the ratio of nonsynonymous to synonymous substitutions ( dN/dS ) was compared among populations of different species. To determine the validity of NNT, however, populations that are genetically isolated from each other but share the same selection agents and differ in size should be compared. Genetically...
Article
How a population adapts to environmental changes is a central topic in ecology, but long-term changes in the phenotype of an organism have rarely been studied in aquatic systems. In this study, we examined the morphological changes in Daphnia pulex from the initial establishment stage, using paleolimnological analysis, in Lake Fukami-ike (Nagano Pr...
Article
Several recent studies have shown that ectosymbiotic bacterial microbiota, including gut microbes, affect the growth and reproduction of Daphnia, a key organism in lake ecosystems. However, these studies examined specific species, such as the model organism, Daphnia magna, and used green algae as food. It is unclear if symbiotic bacteria affect fit...
Article
Full-text available
An increase in nutrient levels due to eutrophication has considerable effects on lake ecosystems. Cladocerans are intermediate consumers in lake ecosystems; thus, they are influenced by both the bottom‐up and top‐down effects that occur as eutrophication progresses. The long‐term community succession of cladocerans and the effects cladocerans exper...
Article
Full-text available
Several genetic lineages of obligate parthenogenetic Daphnia pulex, a common zooplankton species, have invaded Japan from North America. Among these, a lineage named JPN1 is thought to have started colonization as a single genotype several hundred to thousand years ago and subsequently produced many genotypes in Japan. To examine the phenotypic var...
Article
Full-text available
We examined the morphology of Daphnia individuals maintained in our laboratory for several years, originally collected in Lake Inbanuma, Chiba, Japan. We determined partial sequences of the mitochondrial cytochrome c oxidase subunit I and 12S rRNA genes from specimens in the cultured material. These animals are morphologically similar to D. obtusa...
Article
Phaeomelanin is a common pigment that confers a reddish colour to animals. Since phaeomelanogenesis requires the sulfhydryl group from cysteine or glutathione (GSH), which is an important antioxidant, this pigmentation and the associated coloration may be an honest signal, whereby only high-quality individuals (e.g. with lower oxidative stress) are...
Article
Lignins have been used as a biomarker to explore changes in terrestrial organic matter input into lakes and to investigate past watershed vegetation. Burial of organic carbon (OC) in lake sediments, an important component of the global C cycle, is likely associated with the terrestrial OC input. However, few studies have explored changes in terrest...
Chapter
Full-text available
The carnivorous snail (Laguncula pulchella) was once considered an endangered species in Japan because its habitat was limited to western Japan. However, alien L. pulchella populations were transported from China and the Korean Peninsula to the Pacific coast of northeast Japan, presumably via anthropogenic activities. This study examined the geneti...
Article
Full-text available
Background The visual system is important for animals for mate choice, food acquisition, and predator avoidance. Animals possessing a visual system can sense particular wavelengths of light emanating from objects and their surroundings and perceive their environments by processing information contained in these visual perceptions of light. Visual p...
Article
Full-text available
To examine if changes in species composition of a plankton community in the past due to anthropogenic activities can be clarified in lakes without any monitoring data, we analyzed genetically ephippial carapaces of Daphnia with plankton remains stored in the bottom sediments of Lake Hataya Ohunma in Japan. In the lake, abundance of most plankton re...
Article
Full-text available
We examined Daphnia pulex in Japan to clarify if they were representative of indigenous populations or colonized recently. Phylogenetic analysis of mtDNA suggests that Japanese lineages of D. pulex are immigrants from North America, and are hybrids formed with Daphnia pulicaria prior to this immigration. Based on the mtDNA sequences, the D. pulex i...
Article
Full-text available
Fireflies (Coleoptera: Lampyridae) emit various types of light that differ among species and populations of the same species. Their lights are assumed to be biological properties that play important ecological and evolutionary roles. Some species in the Lampyridae emit periodic luminescence, the patterns of which are characterized by speciesspecifi...
Article
Full-text available
Even though calanoid copepods produce diapausing eggs that stay alive in lake sediments, these eggs have rarely been used paleolimnologically, as they lack diagnostic morphological features. In this study, we developed a method to identify copepod diapausing eggs in Japan as a clue toward reconstructing past plankton populations. We first determine...
Article
Full-text available
This study describes a method of DNA extraction and amplification for ephippial cases of Daphnia resting eggs from lake sediment. Recent studies have reconstructed succession records of Daphnia species by genetically analyzing Daphnia resting eggs stored in lake sediments and revealed changes in dominant Daphnia species that correspond well with en...
Data
Supplemental material and methods. The detailed descriptions of the methods for Experimental enclosure and identification of individual bees, the nucleotide sequence determination of Bifor and real-time PCR analyses.
Article
Full-text available
In eusocial hymenopteran insects, foraging genes, members of the cGMP-dependent protein kinase family, are considered to contribute to division of labor through behavioral caste differentiation. However, the relationship between foraging gene expression and behavioral caste in honeybees is opposite to that observed in ants and wasps. In the previou...
Article
Species-specific flash patterns in firefly species are important for the investigation of the evolution of Lampyridae. Since nitric oxide synthase (NOS) is one of the key enzymes controlling flash patterns, we determined the cDNA sequences of NOS in the Japanese fireflies Luciola lateralis and L. cruciata. The identity of the NOS sequences was very...

Citations

... Although genetic diversity was limited and the dominant haplotype did not change during the studied period, the D. pulex population of the studied lake changed their traits including the body size of matured females and induced defensive traits (Otake, Ohtsuki, Urabe, Yamada, & Yoshida, 2021b), which was considered to be an adaptive response to the change in predation. Phenotypic plasticity is a possible mechanism contributing to changes in these traits. ...
... These phytoplankton such as green algae have distinct microbiome based on genotype and external environment [20][21][22]. However, the effects of diet-associated microbes on zooplankton gut microbiota are still in infancy as most of the studies used axenic diets [23,24]. These diet-associated microbes may be important in structuring zooplankton microbiota and might interact with external environment bacterial communities while host establishes its gut microbiome. ...
... We focused on a population of Daphnia pulex Leydig inhabiting Lake Fukami-ike. A previous paleolimnological study suggested that D. pulex had established a stable population in Lake Fukami-ike since the early 2000s (Otake et al. 2021). Daphnia is a keystone taxon in lake ecosystems that is sensitive to biotic and abiotic environmental changes (Capenter and Kitchell 1993;Jeppesen et al. 2001Jeppesen et al. , 2011. ...
... Although this is often defined as the genetic distance estimated by the number of base substitutions among species or individuals (e.g. Van de Peer, 2009), the similarity in the heritable traits between two species or individuals is not necessarily related to the genetic distance (Cheverud, 1988;Stern, 2013;Tian et al., 2019a). Therefore, to examine the appropriateness of the CRH and BCH, not only genetic or phylogenetic distance but also a similarity of heritable traits should be considered. ...
... Existence of the latter was first proposed by Korovchinsky (2006) and then confirmed by special faunistic and phylogeographic studies Kotov et al. 2021). Significant progress was achieved in faunistic, taxonomic, phylogenetic and phylogeographic studies of cladocerans of the Russian Far East, Japan and NE China (Ishida & Taylor 2007;Ishida et al. 2011;Korovchinsky 2012;Maruoka et al. 2018;Wu et al. 2019;Yamamoto et al. 2020). The Republic of South Korea represents a country with a very well studied cladoceran fauna (Yoon 2010;Kotov et al. 2012;Jeong et al. 2014), but even in this country new interesting findings are still possible . ...
... It may be that darker feathers absorb solar radiation to prevent transmitting heat to the skin (Wolf & Walsberg, 2000). Conversely, paler feathers reflect more light and thus reduce body temperature (Arai et al., 2017;Fargallo et al., 2018). A thermoregulation hypothesis would seem to lead to the same predictions as the UV hypothesis. ...
... Chronology was determined based on the constant rate of supply (CRS) method of 210 Pb dating (Appleby and Oldfield 1978) and verified using the 137 Cs peak traced in the period 1962-1963(Appleby 2001. Details of the chronological method have been reported elsewhere (Hyodo et al. 2017). Briefly, dried samples were sealed in holders for a month to allow 222 Rn and its short-lived decay product ( 214 Pb) to equilibrate. ...
... L. pulchella shells collected in Matsushima Bay and Matsukawa-ura Lagoon showed morphological changes such as a reduction in a shell thickness, and the presence of jagged cracks around the aperture of the shell after the disturbance (Suzuki and Okoshi, 2018). The genetic population structure of this specie in Sendai Bay and Sanriku Ria was minimally affected by the tsunami (Ohtsuki et al., 2016). The population of the snail Batillaria attramentaria on the northeast coast of Japan was greatly affected by both the large amount of sand present in the bays and the dragged material by tsunami waves (Miura et al., 2012). ...
... Common and Endler's guppies both have three cone cells sensitive in the long-wavelength range (i.e., the green, yellow, and red portion of the visible light spectrum); the two species also have similar genetic architecture of long-wavelength sensitive opsin genes [58], indicating they have similar 'machinery' for colour vision in the yellow and red spectrum. However, as the two species may have differential expression of opsin genes, they may show differences in the ability to discriminate yellow and red [59]. To disentangle to what extent the cognitive differences we found are due to differences in perception or learning and memory, other colour combinations and tests of behavioural sensitivity to those [59] would be necessary. ...
... Panarctic Daphnia pulex (D. cf. pulex sensu Hebert, 1995) is an endemic species in North America (Colbourne et al., 1998;Crease et al., 2012) that has invaded Japan (So et al., 2015). Among the genetically distinct lineages found in Japan, a lineage named JPN1 is widely distributed across Japan and contains several genotypes (So et al., 2015). ...