博士（水産学）, 北海道大学

生態学

行動学

軟体動物 (貝類、頭足類)

節足動物 (甲殻類、昆虫類)

棘皮動物 (ヒトデ類)

刺胞動物 (イソギンチャク類、クラゲ類)

脊椎動物 (魚類)

Life Science, Ecology and environment

Life Science, Evolutionary biology

Life Science, Aquatic bioproduction science

Bachelor's degree program, School of Fisheries Sciences

Master's degree program, Graduate School of Fisheries Sciences

Doctoral (PhD) degree program, Graduate School of Fisheries Sciences

Oct. 2008, 日本ベントス学会, 日本ベントス学会奨励賞
和田哲

Anatomical and functional specialization of the soldier caste in a heterophyid trematode, Cercaria batillariae
Kentaro Miura; Satoshi Wada; Osamu Miura
Biology Letters, 22, 20250687, 11 Feb. 2026, [Peer-reviewed]
English, Scientific journal

Sexual differences in seasonal changes in major cheliped size and use pattern during dyadic interactions in the hermit crab Pagurus filholi
Tomomi Iyoda; Yuina Kido; Chiaki I Yasuda; Satoshi Wada
Plankton and Benthos Research, 20, 4, 231, 240, The Plankton Society of Japan/The Japanese Association of Benthology, 26 Nov. 2025, [Peer-reviewed], [Last author]
English, Scientific journal

Effect of neighboring prey species on antipredator response of the marine gastropod Nassarius hypolius
Hiroe Tomiyoshi; Satoshi Wada
Plankton and Benthos Research, 20, 3, 205, 209, The Plankton Society of Japan/The Japanese Association of Benthology, 27 Aug. 2025, [Peer-reviewed], [Last author]
English, Scientific journal

Fish yawn: interpopulation variation in yawning characteristics of juvenile white-spotted char Salvelinus leucomaenis
Reo Nagasaka; Hiroyuki Yamada; Satoshi Wada
Journal of Ethology, 43, 97, 103, Springer Science and Business Media LLC, 05 May 2025, [Peer-reviewed], [Last author]
English, Scientific journal

Use of Social Information About Novel Food by Juvenile Solitary Forktongue Goby, Chaenogobius annularis
Daisuke Nakayama; Chiaki I. Yasuda; Satoshi Wada
Ethology, 131, e13569, Wiley, 28 Apr. 2025, [Peer-reviewed], [Last author]
English, Scientific journal, ABSTRACT

Animals use various forms of information to reduce uncertainty about the environment and make adaptive decisions. They can acquire information directly from the environment (personal information) or by observing other individuals' behavior (social information). Since young animals in particular may benefit from acquiring social information owing to their lack of experience at this stage, social information in juveniles would be important even in solitary species. This possibility has, however, been less studied in juvenile solitary fishes. We examined whether juveniles of the solitary forktongue goby, Chaenogobius annularis, use social information about novel artificial food (fish‐food flakes) and a novel food location (water surface). We first tested whether feeding on the novel food is facilitated by past experience to confirm that C. annularis juveniles could learn this information: compared with naïve juveniles, juveniles that previously experienced the novel food showed significantly shorter latencies to begin feeding (at the surface or underwater, hereafter first feeding), and to feed on the water's surface (hereafter, surface feeding). We then compared feeding on novel food between naïve juveniles paired with an experienced juvenile and those paired with a naïve juvenile. Naïve juveniles paired with an experienced juvenile fed significantly more frequently and sooner in both first and surface feedings than the randomly chosen naïve juveniles in each naïve pair. These results suggest that C. annularis juveniles use social information to learn about food and that social information use by juveniles is widespread among vertebrates, regardless of their sociality.

“Standing on tiptoe”: A novel foraging technique in the starfish Patiria pectinifera
Haruto Gushiken; Satoshi Wada
Plankton and Benthos Research, 19, 2, 84, 87, The Plankton Society of Japan/The Japanese Association of Benthology, 31 May 2024, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal

Phenotype‐dependent downstream dispersal under ordinary flow conditions in juvenile white‐spotted char
Hiroyuki Yamada; Satoshi Wada
Ecological Research, 39, 330, 340, Wiley, 05 Mar. 2024, [Peer-reviewed], [Last author]
English, Scientific journal, Abstract

Animal dispersal is often phenotype‐dependent and can exert evolutionary pressures on populations in which it occurs. The evolutionary pressure arising from phenotype‐dependent dispersal is called spatial sorting. We examined the evolutionary pressure arising from spatial sorting (sorting pressure) caused by downstream dispersal in juvenile white‐spotted char Salvelinus leucomaenis under ordinary flow conditions. We conducted outdoor experiments using an artificial channel with 10 steps to investigate the relationship between phenotypic characteristics and the occurrence or distance of downstream dispersal during five daytime hours. Six experiments were conducted using young‐of‐the‐year juveniles collected early in the morning of each experimental day. We focused on two phenotypes, fork length (body size) and station‐holding (SH) behavior, where juveniles remain sedentary on the substrate. Juveniles were assigned to the “SH group” if they exhibited SH behavior for more than 10 s during a 540‐s observation period, and to the “swimming group” if they exhibited SH behavior for less than 10 s. Juveniles in the swimming group had a higher occurrence of downstream dispersal than in the SH group. In addition, large juveniles in the SH group and small juveniles in the swimming group tended to show long dispersal distances. These results suggest an effective sorting pressure against juveniles with active swimming behavior. This sorting pressure may accumulate in isolated char populations located above a tall migration barrier and contribute to the creation and maintenance of the reported interpopulation variation in SH behavior.

Tonic immobility in a marine isopod: the effects of body size, sex, and colour morph
Koichi Igarashi; Satoshi Wada
Journal of the Marine Biological Association of the United Kingdom, 104, e17, Mar. 2024, [Peer-reviewed], [Last author]
Scientific journal

Interpopulation variation of behavioural and morphological traits that affect downstream displacement of the juvenile white‐spotted charr Salvelinus leucomaenis
Hiroyuki Yamada; Satoshi Wada
Journal of Fish Biology, 102, 5, 1168, 1176, Wiley, 13 Mar. 2023, [Peer-reviewed], [Last author]
English, Scientific journal

Fish yawn: the state-change hypothesis in juvenile white-spotted char Salvelinus leucomaenis
Hiroyuki Yamada; Satoshi Wada
Journal of Ethology, 41, 2, 111, 117, Springer Science and Business Media LLC, 10 Jan. 2023, [Peer-reviewed], [Last author]
English, Scientific journal

Stomach contents of the deep-water whelks Buccinum kashimanum and Neptunea sp. (Caenogastropoda: Buccinidae) off the coast of Cape Esan, southwestern Hokkaido, Japan, in the western North Pacific Ocean
Ryusei Yamakami; Satoshi Wada
Venus, 80, 40, 45, 2022, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal

Prey preferences of juvenile whelk Neptunea arthritica (Gastropoda: Buccinidae) in Hakodate Bay, Hokkaido, Japan
Ryusei Yamakami; Satoshi Wada
Plankton and Benthos Research, 16, 257, 265, Nov. 2021, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal

Assemblages of Mollusks (Gastropoda and Bivalvia) on the Intertidal Platform around Kattoshi, Hakodate Bay, Hokkaido
Yamakami, Ryusei; Wada, Satoshi
Bulletin of Fisheries Sciences, Hokkaido University, 71, 1, 1, 14, Aug. 2021, [Last author]
English, Research institution

Interspecific differences of shell utilization pattern of two hermit crab species in southern Hokkaido
Naoya Tsuzaki; Banryu Murakami; Chiaki I. Yasuda; Satoshi Wada
Cancer, 30, 35, 48, Aug. 2021, [Peer-reviewed], [Last author]
Japanese, Scientific journal

Morphological evolution reduces downstream displacement in juvenile landlocked salmon
Hiroyuki Yamada; Satoshi Wada
Evolution, 75, 7, 1850, 1861, Wiley, Jul. 2021, [Peer-reviewed], [Last author]
English, Scientific journal

Prey utilization by Neptunea arthritica (Gastropoda: Buccinidae): predation on gastropods and size-related variation
Ryusei Yamakami; Satoshi Wada
Journal of Molluscan Studies, 87, 2, eyab016, May 2021, [Peer-reviewed], [Last author]
English, Scientific journal

Males display “inverse rapping” as a mating behavior to receptive females in the hermit crab Pagurus nigrofascia
Yuina Kido; Satoshi Wada
Plankton and Benthos Research, 15, 3, 279, 288, Aug. 2020, [Peer-reviewed], [Last author]
English, Scientific journal

Personality differences in white-spotted char fry evident between habitats
Hasegawa Ryota; Yamada Hiroyuki; Ishihara Chiaki; Wada Satoshi
Japanese Journal of Ichthyology, 67, 1, 11, 24, The Ichthyological Society of Japan, Apr. 2020, [Peer-reviewed], [Last author]
Japanese, Scientific journal,

Animal personality, defined as consistent individual differences in behavior across time and/or context, has been associated with individual dispersal tendencies in some species. White-spotted char (Salvelinus leucomaenis) populations, often found in above-dam watersheds in Japanese mountain streams, the dams preventing continuous distribution with lower stream reaches, were subject of a behavioral study comparing above-dam and open-stream behavior of fry. Fries were collected from an above-dam area and two open-stream areas within the Kame River system (southern Hokkaido), and personality quantified by measuring a suite of behaviors, such being repeated two-month later. Above-dam fry showed a shorter swimming duration against a novel object and mirror than open-stream fry. The latency time to catch food in above-dam fry tended to be longer than that of the latter. Swimming duration against a novel object and mirror were significantly correlated when data for both groups combined, but not so when data for each group were analyzed independently. These results suggest that personality traits in whitespotted char fry would be shaped by natural selection acting on each habitat, resulting in differing adaptive personality traits.

Different effects of mating group size as male and as female on sex allocation in a simultaneous hermaphrodite
Masami M. Tamechika; Kohei Matsuno; Satoshi Wada; Yoichi Yusa
ECOLOGY AND EVOLUTION, 10, 5, 2492, 2498, Mar. 2020, [Peer-reviewed]
English, Scientific journal

Behavioral and morphological comparisons of newly emerged white-spotted char, Salvelinus leucomaenis, in two tributaries of the Kame River, southern Hokkaido, Japan
Yamada Hiroyuki; Enomoto Takashi; Wada Satoshi
Japanese Journal of Ichthyology, 66, 2, 221, 225, The Ichthyological Society of Japan, Nov. 2019, [Peer-reviewed], [Last author]
Japanese, Scientific journal,

Many local populations of white–spotted char (Salvelinus leucomaenis), a widespread Far East Asian species, persist in above–dam areas, even when erosion control dams prevent continuing upstream movement of individuals. Four morphological characters (dorsal fin height, body depth, caudal peduncle depth, and eye diameter) and two behavioral traits (settlement time and number of foraging actions) of S. leucomaenis fry were compared between two tributaries, one above an erosion control dam and the other an unrestricted stream. Dorsal fin height and caudal peduncle depth were smaller, and settlement time during daytime longer in the above–dam fry, which also showed less frequent foraging behavior than unrestricted stream fry during nighttime, suggesting that the former had unsuitable morphology for swimming and a lower wondering tendency. These characteristics may ultimately aid survival of the above–dam population.

Sexual conflict in the hermit crab Pagurus nigrofascia: Female avoidance of male initiation of precopulatory guarding
Yuina Kido; Tomomi Iyoda; Chiaki I. Yasuda; Satoshi Wada
Cancer, 28, 7, 15, Carcinological Society of Japan, Aug. 2019, [Peer-reviewed], [Last author]
Japanese, Scientific journal, This paper described female guarding avoidance behaviors against precopulatory guarding attempts by males and examines the effect of the number of days until female prenuptial molting on rejection behaviors in the hermit crab Pagurus nigrofascia. We used three types of females in an experiment; (1) ovigerous females (OV–female), (2) females which had not been guarded in the field (NG–female), and (3) females which had been guarded by other males in the field (G–female). We placed a male that had been solitary and a female of either type in a small container, observed the interaction, and compared the female behaviors among the three types of female. The frequencies of retreat and escape from approaching male were highest in OV–females, and lowest in G–females. During male assessment behaviors of females, frequencies of struggle and escape in OV– and G–females were higher than NG–females. 33 of 51 G–females were guarded by males although OV– and NG–females were rarely guarded by males. Many G–females showed rejection behavior during male guarding. However, no significant effect was found in the number of days until the female prenuptial molt on the frequencies of rejection behavior.

Regeneration of major cheliped after the mating season in the hermit crab Pagurus middendorffii
Chiaki I. Yasuda; Satoshi Wada
Cancer, 27, 1, 5, 2018, [Invited], [Last author]
Japanese, Scientific journal

Antenna length in the hermit crab Pagurus middendorffii: sexual dimorphism and effect on two types of male-male competition
Ayumi Morita; Satoshi Wada
Bulletin of Fisheries Sciences, Hokkaido University, 68, 27, 32, 2018, [Last author]
English, Research institution

Quality assortative pairing and effect of prior contest outcome on male mate choice in the hermit crab Pagurus nigrofascia
Sachi Kojima; Chiaki I. Yasuda; Satoshi Wada
Cancer, 25, 25, 17, 24, 日本甲殻類学会, 2016, [Peer-reviewed], [Last author]
Japanese, Scientific journal

Male-male contests in the hermit crab Pagurus filholi: many males do not initiate contests
Natsumi Kaga; Chiaki I. Yasuda; Satoshi Wada
Cancer, 25, 25, 9, 16, 日本甲殻類学会, 2016, [Peer-reviewed], [Last author]
Japanese, Scientific journal

Pre- and post-molting behaviors in the barnacle, Balanus rostratus
Masami Tamechika; Chiaki I. Yasuda; Satoshi Wada
Caner, 25, 25, 25, 27, 日本甲殻類学会, 2016, [Last author]
Japanese, Scientific journal

Sex-related differences in size, function and regeneration of the major cheliped in the hermit crab Pagurus filholi
Kento Matsuo; Daisuke Tanikawa; Chiaki I. Yasuda; Satoshi Wada
MARINE ECOLOGY-AN EVOLUTIONARY PERSPECTIVE, 36, 4, 1391, 1399, Dec. 2015, [Peer-reviewed], [Last author]
English, Scientific journal

Reason for being single: some males do not guard receptive females in the hermit crab Pagurus filholi
Yukari Hasaba; Chiaki I. Yasuda; Satoshi Wada
ANIMAL BEHAVIOUR, 107, 1, 5, Sep. 2015, [Peer-reviewed], [Last author]
English, Scientific journal

Previous mating experience increases fighting success during male-male contests in the hermit crab Pagurus nigrofascia
Chiaki I. Yasuda; Kento Matsuo; Satoshi Wada
BEHAVIORAL ECOLOGY AND SOCIOBIOLOGY, 69, 8, 1287, 1292, Aug. 2015, [Peer-reviewed], [Last author]
English, Scientific journal

Autotomy of the major cheliped as the antipredatory behavior in the hermit crab Pagurus middendorffii
Kento Matsuo; Chiaki I. Yasuda; Satoshi Wada
Cancer, 24, 21, 23, Carcinological Society of Japan, 2015, [Last author]
Japanese, Scientific journal

Regeneration of major cheliped after the mating season in the hermit crab Pagurus middendorffii
Chiaki I. Yasuda; Satoshi Wada
Crustacean Research, 44, 29, 38, Carcinological Society of Japan, 2015, [Peer-reviewed], [Last author]
English, Scientific journal, Males of the hermit crab Pagurus middendorffii use their major cheliped in male–male contests during the reproductive season. This study examined whether autotomized major chelipeds were regenerated before, during or after the mating season. We reared males that were experimentally induced to autotomize just before the mating season (October). During the mating season (November), few males molted even if they had autotomized their major cheliped. In contrast, males initiated a molt at the end of and after the mating season, and most of the autotomized males regenerated their major cheliped before the end of the rearing period (December). This suggests that regenerated major chelipeds in this study affect events other than mating, particularly perhaps future shell acquisition associated with general activities such as predator avoidance, physiological tolerance and growth.

Hermit crab, Pagurus middendorffii, males avoid the escalation of contests with familiar winners
Chiaki I. Yasuda; Kento Matsuo; Yukari Hasaba; Satoshi Wada
ANIMAL BEHAVIOUR, 96, 49, 57, Oct. 2014, [Peer-reviewed], [Last author]
English, Scientific journal

Sexual size dimorphism in two endemic hermit crabs, Pagurus traversi and P. novizealandiae, in New Zealand
Satoshi Wada; Chiaki I. Yasuda; Colin McLay
Bulletin of Fisheries Sciences, Hokkaido University, 64, 2, 31, 35, 北海道大学大学院水産科学研究科編集出版委員会, 2014, [Lead author, Corresponding author]
English, Research institution, The evolutionary factors of sexual size dimorphism and reproductive characters in Pagurus traversi and P. novizealandiae,are discussed. Investigations and sample collection were conducted in the intertidal area around Kaikoura peninsula, southernisland of New Zealand from 22 February to 23 March 2012. The number of crabs collected was 1198 P. traversi and 318 P.novizealandiae. The degree of size dimorphism ((mean male size)/(mean female size)) was 1.09 and 1.03 in P. traversi and P.novizealandiae, respectively. The fecundity relationship between clutch size and female body size (shield length, mm) in P. traversiwas estimated as log10[clutch size] =1.010 + 0.794 × log10[female size3], indicating that clutch size approximately increaseas an isometric relationship. All males guarded females smaller than themselves in nine precopulatory guarding pairs of P.traversi. However, difference in the mean size between the guarding males (4.79 mm) and other males (4.50 mm) was small(0.29), suggesting that large size advantage might be weak in mate acquisition compared with other species of the genus Pagurus. Weak evolutionary selection pressure acting on male body size may explain relatively small degree of sexual size dimorphism inP. traversi.

Effect of cheliped loss due to autotomy on shell selection behavior in the hermit crab Pagurus middendorffii
Kento Matsuo; Chiaki I. Yasuda; Satoshi Wada
Crustacean Research, 43, 43, 41, 46, The Carcinological Society of Japan, 2014, [Peer-reviewed], [Last author]
English, Scientific journal, Major cheliped is used in shell selection in the hermit crab Pagurus middendorffii. This study examined how loss of the major cheliped due to autotomy affected shell selection behavior and whether shell-size preference was affected. Crabs after autotomy changed shells less frequently than intact crabs. However, there was not a significant difference in shellsize preference between autotomized crabs and intact crabs. Since autotomy occurs during fleeing from a predatory attack in the field, subsequent reduction of frequency of changing shells might suppress the risk of predation for crabs.

Rapid regeneration of the major cheliped in relation to its function in male-male contests in the hermit crab Pagurus middendorffii
Chiaki I. Yasuda; Kento Matsuo; Satoshi Wada
Plankton and Benthos Research, 9, 2, 122, 131, Plankton Society of Japan, 2014, [Peer-reviewed], [Last author]
English, Scientific journal

Contrasting anti-predation responses in the intertidal periwinkle Littorina sitkana: Effects of chemical cue, body size and time of day
Hisae Ojima; Satoshi Wada
Plankton and Benthos Research, 8, 1, 38, 45, 18 Jun. 2013, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal

Reproductive ecology of the strawberry conch Strombus luhuanus: comparison between two sites differing in the degree of fishery exploitation
Taichi Koyano; Atsushi Ito; Satoshi Wada
Japanese Journal of Benthology, 68, 1, 1, 6, 日本ベントス学会誌編集委員会, 2013, [Peer-reviewed], [Last author, Corresponding author]
Japanese, Scientific journal

Male mate choice and male-male competition in the hermit crab Pagurus nigrofascia: importance of female quality
Yutaro Suzuki; Chiaki Yasuda; Fumio Takeshita; Satoshi Wada
MARINE BIOLOGY, 159, 9, 1991, 1996, Sep. 2012, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal

Assessment strategy in male-male contests of the hermit crab Pagurus middendorffii
Chiaki Yasuda; Fumio Takeshita; Satoshi Wada
ANIMAL BEHAVIOUR, 84, 2, 385, 390, Aug. 2012, [Peer-reviewed], [Last author]
English, Scientific journal

MORPHOLOGICAL COMPARISON OF THE SECOND GNATHOPOD IN MALES OF FOUR CAPRELLID SPECIES (AMPHIPODA: CAPRELLIDAE)
Fumio Takeshita; Satoshi Wada
JOURNAL OF CRUSTACEAN BIOLOGY, 32, 4, 673, 676, Jul. 2012, [Peer-reviewed], [Last author]
English, Scientific journal

Effects of male size and mate quality on male-male contest in the hermit crab Pagurus filholi
Tanikawa, D; C. Yasuda; Y. Suzuki; S. Wada
Japanese Journal of Benthology, 67, 1, 15, 19, JAPANESE ASSOCIATION OF BENTHOLOGY, 2012, [Peer-reviewed], [Last author, Corresponding author]
Japanese, Scientific journal, Males of the hermit crab Pagurus filholi guard females until spawning, and male-male contest often occur when guarding males encounter other males. A contest comprises two phases, initial contact and physical combat, and larger males typically win. We conducted male-male contest experiments to examine whether body sizes of both sexes of P. filholi and female receptivity affect whether and when a contest escalates to physical combat, as well as contest duration and outcome. For each experimental trial, a pair, comprising a “pairing male” and a “pairing female”, and a second male (“intruder”) were placed into a small container, and their behaviors were observed for 15 minutes. Each intruder had been guarding a female in the field but we removed this female (“removed female”) just before the trial. All pairs in the field were reconstructed each after trial to quantify female receptivity. This was done by checking each female for spawning every day. As an index of size, we measured shield length (length of calcified anterior portion of cephalothorax) of all crabs. In the trials, large size of the intruder and high receptivity of the removed female significantly shortened the time until the onset of physical combat. Intruders needed more time to take over the pairing females and were less likely to win the contests when the intruders were small, the pairing males were large, and the removed females were large. Body size and receptivity of the pairing female had no effect on the process and the outcome of male-male contest. These results suggest that a male P. filholi can assess the quality of female it is guarding and remember its assessment for at least a short period. Asymmetry between contestants in this memory store for female quality could affect the process and the outcome of male-male contests in P. filholi.
Contents of supplementary materials: Appendix 1: Explanation of movie files, Mov 1: Male-male contest, Mov 2: Cessation of male contest, Mov 3: No guarding after takeover.

Comparison of reproductive traits among local populations of the freshwater crayfish Cambaroides japonicus near Hakodate
Abe, S; S. Tashiro; F. Takeshita; S. Wada
Bulletin of Fisheries Sciences, Hokkaido University, 62, 2, 29, 41, 北海道大学大学院水産科学研究科, 2012, [Peer-reviewed], [Last author]
Japanese, Research institution, ニホンザリガニCambaroides japonicusは北海道から北東北に分布する日本固有の純淡水産甲殻類である。淡水ザリガニ類の多くの種では局所個体群の遺伝的独立性が高いため,生物・物理環境の異なる生息地間でみられる生活史形質の変異は遺伝的変異に起因する可能性が高い。本研究の目的は,北海道南部におけるニホンザリガニの繁殖形質を記載して,本種を保全するための基礎的な知見を得ることである。本研究では,北海道南部に位置する6地点で野外調査をおこない,体サイズ,抱卵・抱仔メスの出現時期,抱卵数,卵・幼生サイズを記載した。そしてこれらの結果を本種の他個体群及び他種と比較した。

Function of the major cheliped in male-male competition in the hermit crab Pagurus nigrofascia
Chiaki Yasuda; Yutaro Suzuki; Satoshi Wada
MARINE BIOLOGY, 158, 10, 2327, 2334, Oct. 2011, [Peer-reviewed], [Last author]
English, Scientific journal

Regional variation in preference for gastropod shell species in the hermit crab Pagurus filholi
Hiromi Hasegawa; Satoshi Wada; Masakazu Aoki; Keiji Wada
JOURNAL OF THE MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM, 91, 4, 893, 896, Jun. 2011, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal

Increased guarding duration reduces growth and offspring number in females of the skeleton shrimp Caprella penantis
Fumio Takeshita; Roberto Carlos Lombardo; Satoshi Wada; Yasuhisa Henmi
ANIMAL BEHAVIOUR, 81, 3, 661, 666, Mar. 2011, [Peer-reviewed]
English, Scientific journal

Male mate choice in hermit crabs: prudence by inferior males and simple preference by superior males
Satoshi Wada; Yuusei Arashiro; Fumio Takeshita; Yasutoki Shibata
BEHAVIORAL ECOLOGY, 22, 1, 114, 119, Jan. 2011, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal

Reproduction and growth in the hermit crab Pagurus nigrofascia: Do males incur costs for growth in precopulatory guarding?
Yoshii, T; F. Takeshita; S. Wada
Japanese Journal of Benthology, 64, 25, 31, JAPANESE ASSOCIATION OF BENTHOLOGY, 2009, [Peer-reviewed]
Japanese, Scientific journal, Reproduction carries costs, in terms of growth, survival, and future reproduction, because reproduction entails the expenditure of energy and time that could be used for other functions. Male Pagurus hermit crabs engage in precopulatory mate guarding behavior for a period of up to several days, and this guarding behavior may entail costs for males. We investigated whether precopulatory mate guarding depresses feeding rate and molting frequency as a cost of reproduction for males in the hermit crab Pagurus nigrofascia. Males were discriminated into the following three size classes: small males that were not observed to guard females, middle-sized males, and large males that guarded females. In the field, molting frequency of the large males was significantly lower than that of the other two size classes. The feeding activity of males was greatly depressed while they were engaged in guarding behavior. The duration of guarding was affected by sex ratio in laboratory experiments, the total guarding time increasing along with the number of mates. Molting frequency did not differ significantly among male crabs under the different sex ratios, however. We suggest that precopulatory mate guarding may entail a reproductive cost for males of P. nigrofascia due to depression of feeding activity although this cost may be compensated for by higher feeding activity before and/or after guarding.

Regional variation in shell utilization pattern of the hermit crab Pagurus filholi
Hasegawa, H; S. Wada; M. Aoki; K. Wada
Plankton and Benthos Research, 42, 72, 76, 2009, [Peer-reviewed]
English, Scientific journal

Factors affecting the interval between clutches in the hermit crab Pagurus nigrivittatus
Satoshi Wada; Takashi Oba; Kazuyoshi Nakata; Atsushi Ito
MARINE BIOLOGY, 154, 3, 501, 507, May 2008, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal

Shell partitionong of two sympartric hermit crabs, Pagurus middendorffii and P-brachiomastus, in north-eastern Hokkaido, Japan
Takashi Oba; Satoshi Wada; Seiji Goshima
JOURNAL OF THE MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM, 88, 1, 103, 109, Feb. 2008, [Peer-reviewed]
English, Scientific journal

Temporal allocation pattern between reproduction and growth within a breeding season of the hermit crab Pagurus nigrivittatus
Wada, S; T. Oba; K. Nakata; A. Ito
Crustacean Research, 37, 67, 73, 2008, [Peer-reviewed]
English, Scientific journal

函館近辺の海岸でみられるヤドカリたちの見分け方と繁殖生態
和田哲
Oshimanography, 15, 17, 18, 2008
Japanese, Symposium

Evolutionary significance of prenuptial molting in female Pagurus hermit crabs
Satoshi Wada; Atsushi Ito; Azusa Mima
MARINE BIOLOGY, 152, 6, 1263, 1270, Nov. 2007, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal

Combined effect of risk type and activity rhythm on anti-predator response of the shore crab Gaetice depressus (Crustacea : Grapsidae)
Ryo Sakamoto; Atsushi Ito; Satoshi Wada
JOURNAL OF THE MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM, 86, 6, 1401, 1405, Dec. 2006, [Peer-reviewed]
English, Scientific journal

Intrasexual copulation and mate discrimination in a population of Nodilittorina radiata (Gastropoda : Littorinidae)
A Ito; S Wada
JOURNAL OF ETHOLOGY, 24, 1, 45, 49, 2006, [Peer-reviewed]
English, Scientific journal

Size assortative mating by the hermit crab Pagurus filholi (Decapoda: Anomura: Paguridae)
Goshima, S; S. Minouchi; K. Yoshino; S. Wada
Biology of Anomura II. Crustacean Research, Special Issue, 6, 87, 94, 2006, [Peer-reviewed]
English, International conference proceedings

Reproductive phenology of sympatric hermit crabs in temperate Japan
S Wada; A Mima; A Ito
JOURNAL OF THE MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM, 85, 4, 889, 894, Aug. 2005, [Peer-reviewed]
English, Scientific journal

Habitat preference in puerulus postlarvae of Japanese spiny lobster Panulirus japonicus
Ito, A; T. Koyano; Y. Okamoto; M. Ohno; S. Wada
水産増殖, 53, 1, 23, 30, Japanese Society for Aquaculture Science, 2005, [Peer-reviewed]
Japanese, Scientific journal, Settlement of puerulus Postlarvae of Japanese spiny lobster Panulirus japonicus was investigated using seaweed-like collectors at a seawall in Uranouchi Inlet, Tosa Bay, Japan. Developmental stage of collected pueruli differed in soaking time of collectors. Late stage pueruli were not collected after one day soaking to compare with longer soaking days, indicating that pueruli might not move around before metamorphosis. In field and laboratory experiments on color preference for artificial seaweed, pueruli did not show consistent preference on color, indicating that puerulus postlarvae do not choose settlement site by color. Timing of metamorphosis from puerulus postlarvae to juvenile was not affected by shelter, indicating that post settled pueruli could not delay metamorphosis.

Effects of male mating frequency and male size on ejaculate size and reproductive success of female spiny king crab Paralithodes brevipes
T Sato; M Ashidate; S Wada; S Goshima
MARINE ECOLOGY PROGRESS SERIES, 296, 251, 262, 2005, [Peer-reviewed]
English, Scientific journal

Effect of food availability on reproduction and growth in the intertidal sea hare Aplysia juliana
Ito, A; S. Wada
Benthos Research, 60, 11, 16, 2005, [Peer-reviewed]
English, Scientific journal

Effect of fishery on density of the strawberry conch, Strombus luhuanus in Uranouchi Inlet, Tosa Bay, Japan
Koyano, T; S. Wada
水産増殖, 52, 2, 129, 132, Japanese Society for Aquaculture Science, 2004, [Peer-reviewed]
Japanese, Scientific journal, Effect of fishery on density of S. luhuanus was surveyed with monthly change of density from April to December in 2002 and yearly change in catch for five years in Uranouchi Inlet, Tosa Bay, Japan. Monthly density in S. luhuanus did not show seasonal fluctuation with a peak in summer, which was reported in other populations. Although the highest density was recorded in May, it largely decreased in the following months, suggesting that the fishery activity for S. luhuanus might decrease the density of our study site in fishery area. However, the average catch amount per day did not change among years from 1998 to 2002. This suggests that introduced larva form other sites might contribute to stabilize the fishery population in Uranouchi Inlet.

Predator avoidance of the conch snail Strombus luhuanus
Higuchi, M; T. Koyano; A. Ito; S. Wada
水産増殖, 52, 3, 251, 258, Japanese Society for Aquaculture Science, 2004, [Peer-reviewed]
Japanese, Scientific journal, Predator avoidance of the conch snail, Styombus luhuanus, and the effect of development of morphological defense on behavioral defense were studied. S. luhuanus shows ontogenetic change in the thickness of shell lip, and two types of conchs, the thin type and the thick type, were used in the experiments. Predatory hermit crab, Dardanus pedunculatus, preferred conchs with thin shell to those with thick shell. Conchs actively jumped and released mucus when attacked by the predator. However, S. luhuanus did not change their behavior under chemical and/or visual stimulus of the predatory hermit crab or conspecific mucus. When subjected to a crushed conspecific stimulus, conchs buried deeper into the sand than under controlled condition. Shell thickness did not seem to affect the predatory avoidance behavior. These antipredatory tactics in S. luhuanus might be effective to increase the fitness in the condition of high density of this species and various potential predators in the field.

Antipredator defence of the hermit crab Pagurus filholi induced by predatory crabs
A Mima; S Wada; S Goshima
OIKOS, 102, 1, 104, 110, Jul. 2003, [Peer-reviewed]
English, Scientific journal

Comparisons in distribution, reproduction and aggressive behavior between two sea anemones, Anthopleura uchidai and A. asiatica
Takahashi, M; M. Higuchi; S. Wada
Bulletin of Marine Sciences and Fisheries, Kochi University, 22, 53, 60, 高知大学海洋生物教育研究センター, 2003
Japanese, Research institution, Distribution pattern, reproductive mode and aggressive behavior of the sea anemones Anthopleura uchidai and A. asiatica from rocky coast of Kochi were studied. Anthopleura uchidai occurred on the crevices and hollows of rocks in splash area and A asiatica did on the underside of stones in intertidal area. The frequency of occurrence in aggressive response between two neighbor individuals differed between species was higher in A. uchidai than in A. asiatica, suggesting that sexual reproduction might be dominant in A. uchidai while A. asiatica might frequently perform asexual reproduction. Anthopleura uchidai more often used acrorhagi for aggression than A. asiatica. Distances between individuals and between colonies were similar between the two species, although A. uchidai formed larger colony than A. asiatica. This suggests that dominant reproductive mode and the intensity of aggressive interaction might not affect local distribution pattern in the two sea anemones.

Effect of light condition on foraging behavior of Japanese spiny lobster
Akamatsu, K; S. Wada
Bulletin of Marine Sciences and Fisheries, Kochi University, 22, 61, 64, 高知大学海洋生物教育研究センター, 2003
Japanese, Research institution, The effect of light condition on size preference for prey clam (Ruditapes philippinarum) and foraging site of Japanese spiny lobster Punulirus japonicus was studied in the laboratory. Light condition was controlled by whether a black curtain was covered over experimental tank or not. Lobsters (60-91mm in carapace length) preferred small clams (>15mm in shell length), and no effect of light condition was detected on the prey size preference. However, lobsters seemed to forage around feeding spot under dark condition while they did around shelter under light condition, suggesting that predation pressure for lobsters might vary with light level in the field.

Reproductive characters of the hermit crab Pagurus proximus Komai 2000 in Hakodate Bay, southern Hokkaido, Japan
Wada, S; A. Mima
Crustacean Research, 32, 73, 78, 2003, [Peer-reviewed]
English, Scientific journal

Extended maternal care observed in Parallorchestes ochotensis (Amphipoda, Gammaridea, Talitroidea, Hyalidae)
T Kobayashi; S Wada; H Mukai
JOURNAL OF CRUSTACEAN BIOLOGY, 22, 1, 135, 142, Feb. 2002, [Peer-reviewed]
English, Scientific journal

Exposure to predators affects shell preference of the hermit crab Pagurus filholi
Mima, A; H. Ohmori; S. Wada; S. Goshima
Benthos Research, 57, 85, 89, 2002, [Peer-reviewed]
English, Scientific journal

Reproductive characters and population structure of the subtidal hermit crab Pagurus ochotensis
Satoshi Wada
Benthos Research, 56, 1, 43, 46, Japanese Association of Benthology, 2001, [Peer-reviewed]
English, Scientific journal

Maturity in male stone crab Hapalogaster dentata (Anomura : Lithodidae) and its application for fishery management
S Goshima; M Kanazawa; K Yoshino; S Wada
JOURNAL OF CRUSTACEAN BIOLOGY, 20, 4, 641, 646, Nov. 2000, [Peer-reviewed]
English, Scientific journal

Reproduction of the hermit crab Pagurus lanuginosus and comparison of reproductive traits among sympatric species
S Wada; H Kitaoka; S Goshima
JOURNAL OF CRUSTACEAN BIOLOGY, 20, 3, 474, 478, Aug. 2000, [Peer-reviewed]
English, Scientific journal

Effects of sex ratio on egg extrusion frequency and mating behavior of the spiny king crab Paralithodes brevipes (Decapoda : Lithodidae)
S Wada; M Ashidate; K Yoshino; T Sato; S Goshima
JOURNAL OF CRUSTACEAN BIOLOGY, 20, 3, 479, 482, Aug. 2000, [Peer-reviewed]
English, Scientific journal

Seasonal Growth Pattern and the Effect of Gastropod Shells on Sexual Growth Rates in the Hermit Crab Pagurus middendorffii
Satoshi Wada
Bulletin of the Faculty of Fisheries, Hokkaido University, 51, 1, 1, 11, Mar. 2000, [Lead author, Corresponding author]
English, Research institution

Life history evolution in hermit crabs : A review
Satoshi Wada
Bulletin of Marine Sciences and Fisheries, Kochi University, 20, 1, 14, 2000
Japanese, Research institution

Preliminary observation on "tip-lip" attachment in the periwinkle Nodilittorina radiata
Satoshi Wada; Atushi Ito
Bulletin of Marine Sciences and Fisheries, Kochi University, 20, 15, 24, 2000
Japanese, Research institution

Environmental factors affecting sexual size dimorphism in the hermit crab Pagurus middendorffii
S Wada
JOURNAL OF THE MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM, 79, 5, 953, 954, Oct. 1999, [Peer-reviewed]
English, Scientific journal

Precopulatory mate guarding in the hermit crab Pagurus middendorfii (Brandt) (Decapoda : Paguridae): effects of population parameters on male guarding duration
S Wada; K Tanaka; S Goshima
JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY, 239, 2, 289, 298, Jun. 1999, [Peer-reviewed]
English, Scientific journal

Shell utilization of the hermit crab Pagurus lanuginosus: sexual differences and specific comparisons
Wada, S; K. Ishizaki; H. Kitaoka; S. Goshima
Benthos Research, 54, 1, 9, 16, Japanese Association of Benthology, 1999, [Peer-reviewed]
English, Scientific journal

Seasonal vertical migration within sediment in the brackish water clam Corbicula japonica
Goshima, S; M. Ikegawa; T. Sonoda; S. Wada
Benthos Research, 54, 2, 87, 97, Japanese Association of Benthology, 1999, [Peer-reviewed]
English, Scientific journal

Mate choice by males of the hermit crab Pagurus filholi: Do males assess ripeness and/or fecundity of females?
S Goshima; T Kawashima; S Wada
ECOLOGICAL RESEARCH, 13, 2, 151, 161, Aug. 1998, [Peer-reviewed]
English, Scientific journal

Shell-size preference of hermit crabs depends on their growth rate
S Wada; H Ohmori; S Goshima; S Nakao
ANIMAL BEHAVIOUR, 54, 1, 8, Jul. 1997, [Peer-reviewed]
English, Scientific journal

Observations on the reproductive behavior of the spiny king crab Paralithodes brevipes (Anomura: Lithodidae)
Wada, S; M. Ashidate; S. Goshima
Crustacean Research, 26, 56, 61, The Carcinological Society of Japan, 1997, [Peer-reviewed]
English, Scientific journal, The reproductive behavior of the spiny king crab, Paralithodes brevipes, was observed in the laboratory. Females always molted before mating and extruding eggs. Males performed pre-copulatory guarding behavior before and/or after its mate molted. When males guarded females, prior to the female molting, the average duration from the start of guarding to molting was 38.6 ± 24.9SD hours. Females spawned within 24 hours of molting. Competition among males for females was observed, and larger males appeared to have a competitive advantage although copulation occurred even when males were smaller than their mates.

Reproductive biology of the hermit crab Pagurus nigrofascia (Anomura: Paguridae)
Goshima, S; S. Wada; H. Ohmori
Crustacean Research, 25, 86, 92, The Carcinological Society of Japan, 1996, [Peer-reviewed]
English, Scientific journal, The distribution and reproductive biology of the hermit crab Pagurus nigrofascia Komai, 1996, were studied from March 1992 to May 1995 at Kattoshi, Hakodate Bay, northern Japan. The species was distributed in the upper intertidal zone, mainly at pebble-covered areas on the shoreline. Ovigerous females were observed from April to February. Developmental stages of incubated eggs were synchronized within the population. The appearance of ovigerous females and examination of developmental stages of eggs revealed that the main spawning month was May, females oviposited once a year, and eggs were incubated for about nine months through the hot summer and cold winter. This long incubation period is a striking reproductive characteristic compared with other Pagurus spp., and suggests a wide variety of reproductive features may exist within the same genus Pagurus, even among species living in the same habitat.

Temporal size covariation of mating pairs of the hermit crab Pagurus middendorffii (Decapoda: Anomura: Paguridae) during a single breeding season
Wada, S; T. Sonoda; S. Goshima
Crustacean Research, 25, 158, 164, The Carcinological Society of Japan, 1996, [Peer-reviewed]
English, Scientific journal, Temporal size variation of precopulatory guarding males and females of the hermit crab Pagurus middendorffii were described from field data collected during a single breeding season, and the advantage of large size to males competing for mates was examined in a laboratory experiment. Larger males won in mate competition, and size assortative mating occurred in the peak and the late periods of the breeding season, but not in the early period. Both mating male and female sizes declined with time during the breeding period. The decrease in size of mating males with time might be caused by the trade-off between the present and future reproductive success, or by physiological constraints. Decreasing size of breeding females might be due to size-dependent variation in the allocation of reproduction and growth, or to physiological constraints experienced by small females.

Reproductive biology of the stone crab Hapalogaster dentata (Anomura: Lithodidae)
Goshima, S; K. Ito; S. Wada; M. Shimizu; S. Nakao
Crustacean Research, 24, 8, 18, Carcinological Society of Japan, 1995, [Peer-reviewed]
English, Scientific journal

Reproductive biology of the hermit crab Pagurus middendorffii Brandt (Decapoda: Anomura: Paguridae)
Wada, S; S. Goshima; S. Nakao
Crustacean Research, 24, 23, 32, The Carcinological Society of Japan, 1995, [Peer-reviewed]
English, Scientific journal, Reproductive biology of the hermit crab Pagurus middendorffii was studied from August 1992 to January 1994 in Kattoshi, located along the west side of Hakodate Bay, Hokkaido, Japan. Its mating season was from late October to early December with a peak in early November. Ovigerous females were observed from October to March, with highest frequencies occurring from December to February (mean: 91.3%). Developmental stages of incubated eggs were synchronized within the population. Females were found to be able to reproduce in their first year and laying a single clutch each following year. Incubation period was about 3.5 months. While ovigerous females did not molt from November to March, male molting frequency was also low during the female incubation period. The covariation of male and female molt frequencies suggests that females do not necessarily have a growth disadvantage due to molt cessation during incubation.

Effects of body size and shell availability on the shell utilization pattern of the hermit crab Pagurus filholi (Anomura: Paguridae)
Ohmori, H; S. Wada; S. Goshima; S. Nakao
Crustacean Research, 24, 85, 92, The Carcinological Society of Japan, 1995, [Peer-reviewed]
English, Scientific journal, Shell availability and shell utilization patterns of the hermit crab Pagurus filholi (de Man) were studied on a rocky shore at Kattoshi, Hakodate Bay, Japan. Quantitative sampling revealed that the proportion of Reticunassa and Littorina shells used by hermit crabs was significantly higher than the relative abundance of these gastropods. Since shell-species preference tests revealed that P. filholi preferred Reticunassa shells, it is suggested that shell-species preference is one of the factors that influence shell utilization. Shell adequacy index (SAI) decreased with increasing crab size for each shell type, and hermit crabs used relatively suitable shells (SAI=1) when shell availability was high. Larger crabs used smaller than preferred shell sizes (SAI<1) and smaller crabs used larger than preferred shell sizes (SAI>1) with decreasing shell abundance. Shell species used by the hermit crab changed with increasing crab size. Therefore, it is suggested that hermit crabs obtain relatively suitable shells by changing shell species.

Precopulatory guarding in hermit crabs: what information do crustaceans use in decision making?
和田哲; 守田安祐美; 石原(安田)千晶, 海洋と生物, 40, 1, 106, 113, 15 Feb. 2018, [Lead author, Corresponding author]
生物研究社, Japanese, Introduction scientific journal

汽水域の生態プロセスを解く(1)
松政 正俊; 倉田 健悟; 和田 哲; グライガー マーク・J, 日本ベントス学会誌 = Japanese journal of benthology, 65, 1, 27, 27, 23 Jul. 2010
JAPANESE ASSOCIATION OF BENTHOLOGY, Japanese, Introduction scientific journal

2009年日本ベントス学会・日本プランクトン学会合同大会後記
五嶋 聖治; 和田 哲; 今井 一郎; 山口 篤, 日本プランクトン学会報, 57, 1, 56, 57, 26 Feb. 2010
Japanese, Meeting report

Male mate choice of Pagurus hermit crabs
WADA Satoshi, 日本甲殻類学会大会講演要旨集, 47th, 33, 2009, [Lead author, Corresponding author]
English, Summary international conference

Mate guarding and reproductive cost to female in skeleton shrimp Caprella penantis
TAKESHITA Fumio; HENMI Yasuhisa; WADA Satoshi, 日本甲殻類学会大会講演要旨集, 47th, 136, 2009, [Last author]
English, Summary international conference

Male-male competition and the role of large cheliped in the hermit crab Pagurus nigrofascia
YASUDA Chiaki; SUZUKI Yutaro; WADA Satoshi, 日本甲殻類学会大会講演要旨集, 47th, 45, 2009, [Last author]
English, Summary international conference

テナガホンヤドカリの相対繁殖成功度の試算(ミニシンポジウム : 『甲殻類の繁殖様式』を終えて)
和田 哲, Cancer : 会員連絡誌, 0, 5, 33, 34, 01 May 1996
日本甲殻類学会, Japanese

〔主要な業績〕ぼくらは航海しない : 水産学部・動物生態学研究室での卒業研究体験記
和田, 哲
海文堂出版, Oct. 2025, 9784303800123, 95p, Japanese, [Editor]

〔主要な業績〕今すぐ見つけに行きたくなる ヤドカリ探索図鑑
第５章 ヤドカリを学ぶ 繁殖生態にも戦略あり：ホンヤドカリ属の多様な生き方
緑書房, Aug. 2025, 9784868110279, [Contributor]

〔Major achievements〕Coastal marine ecology: lessons from the diversity of benthic animals
日本ベントス学会, 第６章 個体群動態
海文堂出版, Sep. 2020, 9784303800512, viii, 246p, Japanese, [Contributor]

〔Major achievements〕Coastal marine ecology: lessons from the diversity of benthic animals
日本ベントス学会, 第３章 種内変異と種内関係
海文堂出版, Sep. 2020, 9784303800512, viii, 246p, Japanese, [Contributor]

〔主要な業績〕海をまるごとサイエンス : 水産科学の世界へようこそ
海に魅せられた北大の研究者たち, 第６章 動物が好きな人へ
海文堂出版, Aug. 2018, 9784303800017, 127p, Japanese, [Contributor]

海洋生物学特論Ⅱ, 2024年, 修士課程, 水産科学院

海洋生物学特論Ⅰ, 2024年, 修士課程, 水産科学院

環境と人間, 2024年, 学士課程, 全学教育

海洋生物科学実験Ⅱ, 2024年, 学士課程, 水産学部

水圏生物科学実習, 2024年, 学士課程, 水産学部

水産科学英語Ⅱ, 2024年, 学士課程, 水産学部

水産資源各論, 2024年, 学士課程, 水産学部

海洋生物科学実験Ⅰ, 2024年, 学士課程, 水産学部

実験統計学, 2024年, 学士課程, 水産学部

ベントス学, 2024年, 学士課程, 水産学部

野外巡検, 2024年, 学士課程, 水産学部

高校生の実習：みんな意外と分かってる！海岸動物の社会関係
LASBOS Moodle, 和田 哲, 01 May 2021 - Present, [Educational materials]

個体群動態入門：基本的な数理モデルの説明
LASBOS Moodle, 和田 哲, 01 Oct. 2020 - Present, [Educational materials]

巻貝も「托卵」する
LASBOS Moodle, 和田 哲, 01 Aug. 2020 - Present, [Educational materials]

行動生態学入門：ヤドカリのオスはどのような情報を利用して、配偶行動をおこなうか？
LASBOS Moodle, 和田 哲, 01 Aug. 2020 - Present, [Educational materials]

統計解析入門 & 統計解析フリーソフトウェアRの使い方
LASBOS Moodle, 和田 哲, 01 Apr. 2020 - Present, [Educational materials]

性配分のwhyとhow: フジツボ類における究極要因と至近要因の解明
科学研究費助成事業
Apr. 2024 - Mar. 2028
遊佐 陽一; 山口 幸; 關野 正志; 和田 哲; 豊田 賢治
日本学術振興会, 基盤研究(B), 奈良女子大学, 24K02100

Molecules that regulates mating behavior of crustaceans: diversity of pheromones and their functions
Grants-in-Aid for Scientific Research
01 Apr. 2023 - 31 Mar. 2027
神尾 道也; 脇本 敏幸; 和田 哲; 千葉 晋; 山家 秀信
2023年度は実験設備の整備を含んだ研究全体の準備を行った。クリガニに関しては5月に北海道大学臼尻実験所にて採集を行い、十分な数の脱皮前メスとそれをを抱いたオスの交尾前ガードペア、脱皮後交尾し交尾栓を持ちながら単独で歩行する交尾後メス、そして単独のオスを捕獲した。これらを実験所にて一時飼育しながら採尿を行い、オス尿約300ml、メス尿約1300mlを採取し、求愛フェロモン精製を開始するための十分な試料を得た。この試料を、脱塩装置で処理した。さらに、東京海洋大学品川キャンパスに冷却水槽を増設し、飼育可能数を拡充した。この飼育設備を用いて飼育したオスを用いて、抱卵メス尿の活性試験、NAGLの活性試験を行った。また、交尾済みのメスも品川にて飼育し、産卵、抱卵させ、抱卵メスの尿を採集した。東京農業大学オホーツクキャンパスにも冷却器を備えた飼育施設を設置しクリガニとトゲクリガニ間の種特異性を検証するための行動実験の準備を整えた。
タラバエビ類の研究においては、研究用水槽システムの構築とフェロモンに対する反応を観察するための行動実験の条件検討を行った。
ヤドカリ類においては、行動実験用設備の構築と、それを用いたフェロモン検出のための行動実験の条件検討、フェロモンを用いた個体間の相互作用の観察を行った。
フェロモンの生合成酵素を探索するための基盤として、クリガニの求愛フェロモン産生器官と考えられているメスの触覚腺の摘出法の検討を行った。また、交尾フェロモン放出期間と考えられている鰓周辺の解剖と、分別方法の検討を進めた。
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Tokyo University of Marine Science and Technology, 23K27002

肉食性巻貝ヒメエゾボラによる在来種及び外来種の餌利用；進化トラップ仮説の検証
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
Apr. 2021 - Mar. 2025
和田 哲
在来種が外来種に示す適応進化は「進化トラップ (外来種に対する適応が、外来種がいない環境で不利にはたらく現象)」となる危険性がある。進化トラップは、陸上生物で危険性が指摘されているが、海洋動物でも作用する可能性がある。とくに肉食性巻貝の多くの種は浮遊幼生期をもたないため、個体群ごとで特殊な適応進化が生じやすい。本研究では、肉食性巻貝ヒメエゾボラと外来種ムラサキイガイに注目して、進化トラップ仮説を検証する。
2021年度は、1980年代における餌種がおもにムラサキイガイであったことが報告されている有珠湾で、摂餌状況の調査を行い、ムラサキイガイが分布していない函館湾葛登支岬周辺の海岸における調査結果と比較した。函館湾ではヒメエゾボラが巻貝を中心に摂餌していたのに対して、有珠湾における主な餌種は二枚貝であった。また、函館湾では餌を各個体が独占して摂食していたのに対して、有珠湾では、複数個体が１個体の餌を同時に摂食する状況が高頻度で観察された。
有珠湾で摂食されていた二枚貝は、函館湾で摂食されていた二枚貝よりも大きく、複数個体が同時に摂食していた二枚貝は、そのなかでも大型の餌であった。また、有珠湾のヒメエゾボラの平均サイズは函館湾よりも大型であることなどが確認された。
有珠湾における主な餌種が、すでにムラサキイガイから他の二枚貝に変化していたことは想定外であった。しかし、摂餌生態の明瞭な個体群間変異が認められた。また、複数個体が同時に摂食する行動は、単体で生息するアサリを餌としている現状では非適応的な行動だと考えられるが、群生するムラサキイガイを餌種としていた場合に有効な摂餌戦略であると考えられる。すなわち、有珠湾のヒメエゾボラには、すでに進化トラップが作用している可能性がある。
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, Principal investigator, 21K05722

Mate choice of hermit crabs: do they use social information due to encountering other individuals
Grants-in-Aid for Scientific Research
2013 - 2015
Wada Satoshi
The following two hypotheses were examined in Pagurus hermit crabs; (1) males choose their mates with using social information due to encoutering other crabs, and (2) males choose their mates with using private information due to encoutering other crabs. We found that frequency of encountering a female were used as private information indicating the encounter frequency of the female in a species, but not as social information indicating encounter frequency of females, and that males tend to overestimate the quality of females pairing with other males.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, Principal investigator, Competitive research funding, 25440228

Resource allocation between growth and reproduction after maturationin Pagurus hermit crabs
Grants-in-Aid for Scientific Research(基盤研究(C))
2007 - 2009
Satoshi WADA
ホンヤドカリ属を対象として、オスとメスの成長と繁殖の資源配分様式を調べた。本属の一部の種では、交尾直前にメスが脱皮することがあり、繁殖期中にも成長する。本研究の結果、脱皮する個体は、とくに産卵間隔が長い傾向が強く、抱卵数も変異が大きかった。オスも配偶行動によって摂餌行動が抑制されるため、繁殖に費やす時間の増加が成長を低下させることが示唆されたが、実験ではそれを強く支持する結果は得られなかった。
Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(C), 北海道大学, Principal investigator, Competitive research funding, 19570012

変動環境における成長と繁殖の資源配分戦略:ヤドカリの交尾直前脱皮に着目して
科学研究費補助金(若手研究(B))
2005 - 2006
和田 哲
ホンヤドカリ属における成長と繁殖の資源配分パターンと環境条件の影響を明らかにするために、函館湾に生息するホンヤドカリ、イクビホンヤドカリ、ケアシホンヤドカリ、ヨモギホンヤドカリのガードペアを採集後、産卵まで飼育して、産卵間隔、産卵数、交尾直前脱皮の有無、メスサイズ、貝殻サイズの関係を調べた。その結果、1回産卵/年であるヨモギホンヤドカリのメスは、全て脱皮したが、複数回産卵/年の他種個体群のメスで、産卵間隔の長い個体のほうが高頻度で脱皮する傾向が得られた。いっぽう、産卵数やメスサイズ、貝殻サイズの影響は、種間で異なっていた。またホンヤドカリでは、脱皮頻度と産卵間隔の時間変動が大きく、本種の成長と繁殖における資源配分が水温や餌条件などの環境条件によって大きく左右されることが示唆された。なお、今年度は飼育実験によって、これらの環境条件の影響を検証する予定だったが、飼育環境に不備があり、多くの飼育個体が死亡したために、検証を行うことができなかった。また、函館湾のヨモギホンヤドカリを対象種として、野外で採集された個体を3日間飼育して、脱皮個体数と脱皮あたり成長量を測定して、成長フェノロジーを調査した。その結果、ヨモギホンヤドカリでは、夏季に脱皮頻度が大きく低下する傾向が得られた。この傾向は、夏季に脱皮頻度が高い同属他種とは大きく異なっているため、本種と他種における成長と繁殖の資源配分の違いにも大きく関与する可能性が示唆された。
文部科学省, 若手研究(B), 熊本大学->北海道大学, Principal investigator, Competitive research funding, 17770018

ヤドカリはなぜ交尾直前に脱皮するのか:変動環境下における成長と繁殖の資源配分戦略
科学研究費補助金(若手研究(B))
2003 - 2004
和田 哲
ヤドカリには交尾・産卵直前に雌が(1)常に脱皮する種、(2)脱皮しない種、(3)脱皮したりしなかったりする種がいる。(2)や(3)に属する種の存在は、脱皮がヤドカリの配偶行動に不可欠ではないことを示唆する。しかし多くの種で雌は交尾直前に脱皮する。本研究は交尾直前脱皮の適応的意義の解明を目的としておこなった。上記(3)に属する種では、同一個体群の雌が連続産卵雌(過去に産卵した卵を孵化した雌がすぐに雄と交尾し産卵する)と不連続産卵雌(過去の卵を持たない雌が産卵する)に区分できる。本研究はこの点に着目して以下の仮説を検証した。成長仮説:雌は脱皮のコストで不連続産卵となっても、成長するために脱皮する繁殖仮説:脱皮が抱卵場所の更新に役立つならば、雌は連続産卵時に脱皮する上記(3)に属し高知県で普通に見られるホンヤドカリ属3種(ホンヤドカリ、クロシマホンヤドカリ、ユビナガホンヤドカリ)を対象種として、野外で雄に交尾前ガードされている雌をペアとして採集し、研究室で産卵まで飼育して、連続/不連続産卵の識別と脱皮の有無等を比較した。その結果、全ての種で成長仮説が支持された。さらにユビナガホンヤドカリを用いて、脱卵数、抱卵数、オスとメスの体サイズ、メスが背負っている貝殻サイズが脱皮頻度に与える影響を訥べた結果、脱皮によって脱卵数が増加し抱卵数が減少する傾向を認められた。また、脱皮あたり成長率は有意に0よりも大きく、脱皮によって体サイズが増大することが明らかとなった。以上の結果でも成長仮説が支持された。ホンヤドカリ属の他種を含めた種間比較の結果、成長仮説はホンヤドカリ属における(1)-(3)の種間変異もよく説明することが示唆された。
文部科学省, 若手研究(B), 高知大学->熊本大学, Principal investigator, Competitive research funding, 15770010

海産甲殻類の生活史進化:ヤドカリ類の生活史形質の変異と生物・物理条件の関係
科学研究費補助金(奨励研究(A), 若手研究(B))
2001 - 2002
和田 哲
甲殻類では交尾(産卵)直前にメスが(1)常に脱皮する種、(2)常に脱皮しない種、(3)脱皮したりしなかったりする種がいる。これは甲殻類の生活史進化における興味深い現象だが、研究例はほとんどない。本研究ではヤドカリ類の生活史形質、とくにメスの交尾(産卵)直前脱皮と繁殖形質に着目して調査をおこなった。高知県中央部に位置する浦の内湾の転石海岸と高知県東部羽根岬に生息するホンヤドカリ、ユビナガホンヤドカリ、アカシマホンヤドカリ、カノコケアシホンヤドカリなどを対象として交尾直前脱皮の有無、脱皮当たり成長率、繁殖フェノロジー、産卵数、幼生艀化数を記録した。その結果、幼生艀化後すぐに新たな産卵をおこなう連続産卵メスよりも不連続産卵メスの方が交尾直前脱皮頻度が高く、この脱皮によって実質的な対サイズの増大が認められた。産卵パターン(連続か不連続か)や脱皮の有無による産卵数の違いは明らかではなかった。これらのことから、ヤドカリにとって交尾直前脱皮は繁殖成功度を高めるわけではなく、清澄を介して将来の生存率や繁殖力を高める機能をもつことが示唆された。さらに、脱皮と産卵の間にトレードオフ関係が成立していることが示唆された。しかし、ホンヤドカリとユビナガホンヤドカリを対象として、繁殖期を通して交尾直前脱皮と産卵パターンの関係を調べたところ、両種共に繁殖盛期に連続産卵メスの脱皮頻度が高くなった。このことは脱皮と産卵のトレードオフが単純な関係ではなく、水温や餌の質と量などの環境要因や産卵数などの内的要因の影響を受けていることを示唆している。
文部科学省, 奨励研究(A), 若手研究(B), 高知大学, Principal investigator, Competitive research funding, 13740443

タラバガニ科のカニ型形態への進化をもたらした生態学的条件の種間比較による検証
科学研究費補助金（特別研究員奨励費）
1998 - 1999
和田哲
文部科学省, 特別研究員奨励費, 北海道大学, Principal investigator, Competitive research funding, 98J02268

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Other than myself
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読売新聞
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魚眼図, [Paper]

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