Haruki Ochi
Kyoto University
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Featured researches published by Haruki Ochi.
Zoological Science | 2007
Michio Hori; Haruki Ochi; Masanori Kohda
Abstract Antisymmetry in the direction of the mouth opening, to either the right (“lefty”) or left (“righty”), was documented in the scale-eating cichlid Perissodus microlepis. This study revealed the presence of lefty and righty mouth morphs in the herbivorous cichlid Neolamprologus moorii, although the degree of deviation was not large. Both species are biparental brooders and guard their young. We examined the inheritance pattern of the dimorphism (laterality) using parents and broods of P. microlepis and N. moorii collected in the wild. In P. microlepis, lefty-lefty pairs had a 2:1 frequency of lefty:righty young, lefty-righty pairs a similar number of each type of young, and righty-righty pairs only righty young. Similar inheritance patterns were observed in N. moorii. We propose two hypotheses to explain the inheritance pattern: Mendelian genetics with the lefty allele dominant over the righty and the dominant allele homozygous lethal, and cross-incompatibility that is predominant in lefty homozygotes.
Environmental Biology of Fishes | 1996
Masanori Kohda; Yasunobu Yanagisawa; Tetsu Sato; Kazuhiro Nakaya; Yasuo Niimura; Kazunori Matsumoto; Haruki Ochi
SynopsisGeographical colour variation and distribution of 48 common cichlid fish species were studied at 20 sites along an 85 km shoreline at the southern end of Lake Tanganyika, Africa. Sixteen species had two or more colour morphs and 11 species showed a limited distribution in the study area. They were all rock-dwellers. Distributional borders of the color morphs and species with a limited distribution mostly lay in two long sandy beaches, 7 and 13 km long. We suggest that the long sandy beaches can be effective barriers against dispersal of shallow-water rock-dwelling cichlid fishes.
Behaviour | 2009
Haruki Ochi; Satoshi Awata
In two coexisting species with similar body colours, one species may acquire benefits from mimicking the body colour of the other species. In Lake Tanganyika, the zoobenthivorous cichlid Neolamprologus mustax preferentially exploits the territories of the algivorous cichlid Variabilichromis moorii as a feeding ground, even though other zoobenthivorous cichlid species are expelled from these territories. The yellow body colour of the guest species, N. mustax , resembles that of juveniles of the host species, V. moorii , adults of which have entirely black bodies. To estimate the effect of juvenile colour on aggression from conspecific adults, the responses of adult V. moorii to dummy fish of four colours (black, yellow, white, and blue) were observed in this lake system. Our observations clearly demonstrated that adult V. moorii were less aggressive toward yellow, white, and blue dummies compared to black ones, with a slight difference in response to the yellow and white or blue dummies. This study indicates that resembling the colour of host juveniles can facilitate access of the guest species to host territory, but does not provide sufficient evidence for a hypothesis that the guest species mimics the body colour of the host juvenile.
Copeia | 2001
Haruki Ochi; Takeshi Kanda; Yasunobu Yanagisawa
Abstract Brooding and nest-maintenance behaviors of the bagrid catfish Auchenoglanis occidentalis (Valenciennes, 1840) were studied in the southern end of Lake Tanganyika. We observed huge saucerlike nests, 1.2–3.8 m across, on the fine sand bottom of the littoral zone. The lowest parts of the nests were covered with an accumulation of coarse particles consisting mainly of gastropod and bivalve shells and shell-fragments, which the catfish sifted out from the sediment. Broods were buried within the shell accumulation and tended solely by males for up to two weeks until the juveniles were motile. Brooding males spent most of their time fanning the pectoral fins and undulating the posterior body. These movements resulted in water flow over the broods, which might serve to prevent oxygen deficiency. They did not act aggressively against intruding potential brood-predators. Nest distribution and relationships between nest size and shell content in the sediment suggest that nest site selection and nest size are determined by the shell availability in the sediment.
Biology Letters | 2012
Tetsumi Takahashi; Haruki Ochi; Masanori Kohda; Michio Hori
A focus on pair bonds between males and females is fundamental to study the evolution of social organization. Because pair bonds are generally identified from direct observations of pairs that maintain physical proximity, pair bonds may have been overlooked in animals that do not exhibit such visible pairs. The Lake Tanganyika cichlid fish Xenotilapia rotundiventralis forms schools that consist of mouthbrooding and non-brooding adults in mid-water, and visible pairs are not recognized. A previous study suggested that mouthbrooding females transfer fractions of the young to males when the young become large. However, it remains a mystery whether the mating pairs maintain pair bonds so that the females can transfer the young to their mates. To answer this question, we conducted a parentage analysis using 10 microsatellite markers. The analysis showed that the mouthbrooding adults were most likely genetic fathers and mothers of the young in their mouths. This finding suggests that the female-to-male shift of young takes place between mating partners, and thus the mating pairs maintain pair bonds at least until the shift of young. The present study is the first to detect pair bonds in animals in which physical proximity has not been observed.
Behaviour | 2012
Haruki Ochi; Masanori Kohda
An algivorous cichlid, Variabilichromis moorii (Vm), defends permanent territories in Lake Tanganyika, Africa. A zoobenthivorous cichlid, Neolamprologus mustax (Nm), spends 60% of daylight hours foraging in Vm territories, from which other zoobenthivorous fishes are chased out and consequently which are much richer in prey animals than areas outside of Vm territories. We conducted a field experiment to examine whether Nm residents and non-residents received different degrees of attacks from Vm. Nm fish were caught in their territories, released at a point distant from these territories, and followed to observe interactions with Vm fish. The frequency of attacks received by the displaced Nm fish was greater than attacks received by Nm residents, indicating that Nm residents had easier access to Vm territories than non-residents did. A possible mechanism for this is reduced aggression of Vm towards Nm residents, as a result of the ‘dear enemy’ effect that has been reported in territorial contests between rivals. An alternative mechanism is that tolerance towards Nm differs among Vm fish and Nm residents selectively visit more tolerant Vm fish due to previous experience while non-residents randomly approach both tolerant and hostile Vm fish. The ability of Vm to discriminate between Nm residents and non-residents is essential to the former mechanism but not to the latter. To more specifically examine which mechanism works in the Vm-Nm commensal system, we will need to follow individually identified Vm fish interacting with Nm residents and non-residents.
Ichthyological Research | 2009
Haruki Ochi; Tomohiro Takeyama; Yasunobu Yanagisawa
Underwater observations conducted in Lake Tanganyika showed that males of a maternal mouthbrooding cichlid, Petrochromis fasciolatus, defended a mating territory for at least several months, but left at approximately noon every day. After the experimental removal of males from their territories, new owners occupied the vacated territories within several days. New owners exhibited higher body-condition factors and fat indices than the original owners. These results suggest that the new owners had not previously occupied a territory, considering the physical exhaustion of owners owing to the energy expenditure on territory maintenance and mating behaviors and a limited time for feeding. Original owners had heavier testes than new owners, despite similar body sizes. This disparity in testis weight suggests that energy investment in testes increases following territory acquisition. Among males that newly occupied a territory during the observation period, larger individuals occupied territories sooner, suggesting that large body size facilitates competition for territory. It is concluded that energy investment in testes is delayed for somatic growth until territory acquisition.
Hydrobiologia | 2017
Haruki Ochi; Hiroki Hata; Masanori Kohda
Animals in a population consistently differ from one another in behavioural types over time and this difference can affect intra- and interspecific relationships. However, empirical studies about roles of behavioural individual variation in interspecific interactions are scarce. Here, we provide evidence that inter-individual variation of a cichlid in aggression affects access to its territory by a heterospecific cichlid. In Lake Tanganyika, a zoobenthivorous cichlid Neolamprologus mustax (Nm) is admitted into territories of an algivorous Variabilichromis moorii (Vm) to prey on benthic invertebrates, while other zoobenthivorous fishes are chased from the territories. We conducted an experiment in which caged Nm fish were exposed twice to each Vm fish in natural habitats. Results indicated repeatable individual variations in Vm aggression towards Nm. Moreover, diving observations indicated that Nm fish frequently used some of Vm territories inside their own territories, but rarely or never used others. This uneven use of Vm territories by the Nm fish was negatively correlated with individual variations in Vm aggression. We conclude that the preferential access of Nm to Vm territory is gained by Nm’s recognising more tolerant Vm fish or discriminating among sites for their territories.
Royal Society Open Science | 2016
Hiroki Hata; Haruki Ochi
Cichlid fish in Lake Tanganyika represent a system of adaptive radiation in which eight ancestral lineages have diversified into hundreds of species through adaptation to various niches. However, Tanganyikan cichlids have been thought to be oversaturated, that is, the species number exceeds the number of niches and ecologically equivalent and competitively even species coexist. However, recent studies have shed light on niche segregation on a finer scale among apparently equivalent species. We observed depth and substratum preferences of 15 herbivorous cichlids from four ecomorphs (i.e. grazer, browser, scraper and scooper) on a rocky littoral slope for 14 years. Depth differentiation was detected among grazers that defended feeding territories and among browsers with feeding territories. Cichlid species having no feeding territory also showed specificity on depth and substratum, resulting in habitat segregation among species that belong to the same ecomorph. Phylogenetically close species did not occupy adjacent depths, nor the opposite depth zones. Our findings suggest that apparently equivalent species of the same ecomorph coexist parapatrically along depth on a few-metre scale, or coexist with different substratum preferences on the rocky shore, and this niche segregation may have been acquired by competition between encountering equivalent species through repetitive lake-level fluctuations.
Ecology of Freshwater Fish | 2010
Yuichi Takeuchi; Haruki Ochi; Masanori Kohda; D. Sinyinza; Michio Hori