Publishing type：Research paper (scientific journal)   Publisher：Frontiers Media SA  

Within the set of risk factors that compromise the conservation of marine biodiversity, one of the least understood concerns is the noise produced by human operations at sea and from land. Many aspects of how noise and other forms of energy may impact the natural balance of the oceans are still unstudied. Substantial attention has been devoted in the last decades to determine the sensitivity to noise of marine mammals—especially cetaceans and pinnipeds—and fish because they are known to possess hearing organs. Recent studies have revealed that a wide diversity of invertebrates are also sensitive to sounds, especially via sensory organs whose original function is to allow maintaining equilibrium in the water column and to sense gravity. Marine invertebrates not only represent the largest proportion of marine biomass and are indicators of ocean health but many species also have important socio-economic values. This review presents the current scientific knowledge on invertebrate bioacoustics (sound production, reception, sensitivity), as well as on how marine invertebrates are affected by anthropogenic noises. It also critically revisits the literature to identify gaps that will frame future research investigating the tolerance to noise of marine ecosystems.

DOI： 10.3389/fmars.2023.1129057

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Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1111/jfb.15131

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/jfb.15131

Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1111/jfb.15047

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/jfb.15047

Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1111/acv.12725

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/acv.12725

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

We evaluated whether a strict fisheries management measure of closure of fishing for recruiting juveniles (glass eels) could have resulted in the recovery of a local population of Japanese eels, Anguilla japonica, when there was no harmonized management of the other life stages, the relevant ecosystem, or local socioeconomic factors (i.e., Ecosystem-Based Management (EBM) approach not applied). The study was conducted in the Kojima Bay-Asahi River system, Okayama Prefecture, Japan, because this prefecture has not permitted commercial glass eel fisheries since 2003, which provides a unique opportunity to conduct a quasi–experimental evaluation of the effects of a glass eel fisheries moratorium. Longline eel fishery data and fishery-independent sampling data indicate that growth-phase Japanese eel (yellow eel) abundance in this water system has not increased, or maybe even decreased, since commercial glass eel fisheries in this area were closed. Based on the results obtained in this study, we concluded that the closure of glass eel fisheries was not a sufficient countermeasure to recover the Japanese eel population in the study area. To conserve and sustainably use Japanese eels, a series of management measures such as habitat restoration and management of yellow and silver eel fisheries are needed along with the control of glass eel fisheries throughout the species distribution range. The EBM approach might be helpful to progress integrated management at appropriate spatial scales.

DOI： 10.1016/j.marpol.2021.104806

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Language：English   Publishing type：Research paper (scientific journal)  

Anguillid eels are found globally in fresh, transitional and saline waters and have played an important role in human life for centuries. The population status of several species is now of significant concern. The threats to populations include direct exploitation at different life stages, blockages to migratory routes by dams and other structures, changes in river basin management that impact habitat carrying capacity and suitability, pollution, climate change, diseases and parasites. While much has been done to understand eel biology and ecology, a major challenge is to identify the key research and management questions so that effective and targeted studies can be designed to inform conservation, management and policy. We gathered 30 experts in the field of eel biology and management to review the current state of knowledge for anguillid eel species and to identify the main topics for research. The identified research topics fell into three themes: (a) Lifecycle and Biology; (b) Impacts and (c) Management. Although tropical anguillid eels are by far the least well understood, significant knowledge gaps exist for all species. Considerable progress has been made in the last 20 years, but the status of many species remains of great concern, particularly for northern temperate species. Without improved engagement and coordination at the regional, national and international level, the situation is unlikely to improve. Further, adaptive management mechanisms to respond to developments in science, policy and our knowledge of potential threats are required to ensure the future of these important and enigmatic species.

DOI： 10.1111/faf.12549

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1038/s41598-020-65883-4

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Other Link： http://www.nature.com/articles/s41598-020-65883-4

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

This study evaluated the size and age distributions and otolith microchemistry of the Japanese eel Anguilla japonica in freshwater and brackish water areas in the Aki and Tsuchikawa rivers for 1 year, and in brackish water areas in the Asahi River for 3years to understand the movements of Japanese eels between continental habitats of different salinity after recruitment (n = 759). For all three rivers, the total length (L-T) and age distributions were consistent; yellow eels captured in the upper brackish water (Aki River: 353.5 +/- 77.4mm and 3.0 +/- 0.8years; Tsuchikawa River: 287.7 +/- 87.3mm and 3.7 +/- 1.3years; Asahi River: 418.2 +/- 112.1mm and 4.2 +/- 1.7years) were smaller and younger than not only those in the fresh water of the two rivers but also those in the lowest brackish water sampling areas (Aki River: 436.0 +/- 71.6mm and 3.8 +/- 1.1years; Tsuchikawa River: 370.9 +/- 121.7mm and 4.9 +/- 2.3years; Asahi River: 558.5 +/- 85.9mm and 5.7 +/- 1.7years). In the Asahi River, these tendencies were found throughout the 3years. Otolith analysis indicated that the majority of the eels captured in the lowest brackish water areas had moved down from upstream. These results suggest that Japanese eels inhabiting saline water generally move from the upper estuary as they grow. The upper estuary can be an important area for the management of this species because these eels spend their early continental growth life there.

DOI： 10.1111/jfb.14236

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE INC  

To clarify the relationships between growth, endocrine status and habitat characteristics in Japanese eel (Anguilla japonica), plasma and stomach mRNA levels of ghrelin were examined in wild eels captured in the river and the bay, and in cultured eels during and after experimental fasting. Wild juvenile eels captured in freshwater habitats within the river showed significantly higher plasma and stomach mRNA levels of ghrelin than did fish obtained from brackish-water habitats within the bay. In cultured eels experimentally fasted for 4 weeks, plasma and stomach mRNA levels of ghrelin increased. After refeeding, the both parameters returned to the levels observed in continuously feeding control fish. In pigmented elvers, 2 months of feed restriction resulted in a significant increase in whole-body ghrelin mRNA. It is suggested that interaction between ghrelin and feeding is related to their habitats through differential food acquisition in fresh and brackish water environments.

DOI： 10.1016/j.cbpa.2020.110700

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Authorship：Lead author,　Corresponding author   Language：Japanese  

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/aqc.3058

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/aqc.3058

Authorship：Lead author,　Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Although Japanese eel, Anguilla japonica, is listed as endangered on the International Union for Conservation of Nature Red List of Threatened Species, a previous stock assessment of the Japanese eel estimated that the age 1+ stock of the species has been recovering since 1990. To help understand the population dynamics of wild Japanese eels, eel fisheries in coastal and estuarine areas in Japan were investigated, because inland fisheries cooperative associations have conducted eel stocking that is presumed to bias the fisheries data in inland waters of Japan. We conducted a questionnaire survey of 1509 fisheries cooperative associations in coastal and estuarine areas of Japan, where the possible bias of eel stocking is expected to be relatively low. Based on the questionnaire, exploitable eel (yellow and silver eels) catch and effort data from 2003 to 2018 were obtained from six fisheries cooperative associations. A standardized catch per unit effort (CPUE) was developed using a generalized linear model for each fisheries cooperative association. The results indicated that the standardized exploitable eel CPUE was significantly lower in four of the six associations. As for the other two associations, significant relationships between CPUE and year was not found. Additionally, of the 227 fisheries cooperative associations that confirmed they catch eels, 1.3%, 5.3%, 21.6%, and 71.8% answered that the eel stock is “relatively increasing,” “stable” “relatively decreasing,” or “decreasing,” respectively, with no association stating that the eel stock is “increasing.” Moreover, reported glass eel CPUE in nine prefectures in Japan was significantly lower in both periods of 1977–2018 and 2003–2018. Because the dataset used in this study is likely to be one of the best currently available, the wild Japanese eel stock appears to be currently declining in Japanese coastal and estuarine waters, where the bias of eel stocked eels on stock dynamics is thought to be relatively low.

DOI： 10.1016/j.fishres.2019.105348

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Society of Fisheries Science  

<p> To clarify the natural distribution of Japanese eels in Japan, otolith oxygen and carbon stable isotope analyses were conducted by analyzing collections of data on Japanese eels in scientific archives. The stable isotope analyses can segregate naturally recruited eels from stocked eels. As a result, coastal regions of the whole area of Kyushu, the Seto Inland Sea, the Pacific side south of Aomori Prefecture, and the Sea of Japan side south of Kyoto Prefecture were identified as main areas of natural distribution, and coastal regions from Fukui Prefecture to Aomori Prefecture facing the Sea of Japan were identified as marginal areas of natural distribution. Even in the main area, some rates of naturally recruited eels were less than 30%, suggesting that the eel resources inhabiting Japanese rivers and lakes are dependent on stocked eels.</p>

DOI： 10.2331/suisan.18-00038

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s10641-019-00915-1

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Ecology and Civil Engineering Society  

DOI： 10.3825/ece.22.73

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford  

We successfully discriminated wild and cultured anguillid eels without artificial tagging. For the purpose of population restoration of anguillid eels, stocking has been widely conducted in the European Union (EU) and Japan, although the net benefits of stocking remain unclear. To evaluate the effectiveness of eel stocking for population restoration, the survival, growth, escapement, and reproduction of stocked eels should be tracked. In this study, we explored the potential of using otolith oxygen and carbon stable isotope ratios as a natural tag to discriminate between wild and cultured eels, because cultured eels are often stocked into natural rivers and lakes. A discrimination model was developed based on wild (n = 95) and cultured (n = 314) Japanese eels as a training dataset. The results of accuracy estimation based on leave-one-out cross-validation were 96.8%. We then tested the applicability of the model to stocked-recaptured eels (n = 20); 100.0% were successfully identified as cultured eels, indicating that these eels spend their early continental phase in aquaculture ponds before stocking. This method could be widely applied to assess the effectiveness of eel stocking by determining the proportion of stocked eels among those captured from rivers, coastal areas, or spawning grounds.

DOI： 10.1093/icesjms/fsx173

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The catch of the Japanese eel, Anguilla japonica, has decreased since the 1970s and this species is currently listed as endangered in the IUCN Red List of Threatened Species. This article reviews current activities for the conservation and sustainable harvest of the Japanese eel in Japan and discusses the challenges that need to be overcome. The public and private sectors have been conducting stocking, research, and habitat restoration activities and making donations for the purpose of species conservation. However, only one academic paper has assessed its population dynamics and a web search revealed only a few activities aimed at restoring the Japanese eel habitat. Because the available data on its population dynamics are so limited, stock management procedures should be selected carefully. In addition to fisheries management, the rivers and lakes where the Japanese eel spends its growth phase should be restored. Because of its high trophic level and broad habitat range, the Japanese eel can be a flagship species for aquatic ecosystems.

DOI： 10.18960/seitai.68.1_43

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Language：English   Publishing type：Part of collection (book)   Publisher：SPRINGER-VERLAG BERLIN  

Marine invertebrates potentially represent a group of species whose ecology may be influenced by artificial noise. Exposure to anthropogenic sound sources could have a direct consequence on the functionality and sensitivity of their sensory organs, the statocysts, which are responsible for their equilibrium and movements in the water column. The availability of novel laser Doppler vibrometer techniques has recently opened the possibility of measuring whole body ( distance, velocity, and acceleration) vibration as a direct stimulus eliciting statocyst response, offering the scientific community a new level of understanding of the marine invertebrate hearing mechanism.

DOI： 10.1007/978-1-4939-2981-8_6

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Language：Japanese   Publisher：JAPANESE SOC FISHERIES SCIENCE  

DOI： 10.2331/suisan.81.873

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publisher：The Japanese Society of Fisheries Science  

DOI： 10.2331/suisan.81.635

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

Unidirectional water flow results in the downstream-biased, asymmetric dispersal of many riverine organisms. However, little is known of how asymmetric dispersal influences riverine population structure and dynamics, limiting our ability to properly manage riverine organisms. A metapopulation of the freshwater pearl mussel Margaritifera laevis may be sensitive to river currents because mussels are repeatedly exposed to downstream drift during floods-a parasitic life stage is the only, limited period (similar to 40 days) during which larvae (glochidia) can move upstream with the aid of host fish. We hypothesized that water-mediated dispersal would overwhelm upstream dispersal via host fish, and therefore, that upstream subpopulations play a critical role as immigrant sources. To test this hypothesis, we examined the effects of both up-and downstream immigrant sources on the size of target subpopulations in the Shubuto River system, Hokkaido, Japan. We found that target subpopulation size was dependent on the upstream distribution range of reproductive subpopulations and the number of upstream tributaries, which are proxies for the number of potential immigrants moving downstream. In contrast, little influence was observed of downstream immigrant sources (proximity to downstream reproductive subpopulations). These results were consistent even after accounting for local environments and stream size. Our finding suggests that upstream subpopulations can be disproportionately important as immigrant sources when dispersal is strongly asymmetric.

DOI： 10.1002/ece3.1135

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

The Japanese coastlines along the Sea of Japan (Japan Sea) have been thought to be one of the margins of the distribution range of the Japanese eel Anguilla japonica, and there is evidence that eels had naturally recruited into these areas several hundred years ago. However, recruitment there is uncertain recently, because there seems to be no study that reported glass eel or elver recruitment into the coasts along the Japan Sea for a couple of decades, and the eels inhabiting these areas were probably stocked by fisheries cooperatives. In order to improve understanding of the present-day natural geographic distribution range of this species, we searched for naturally recruited wild eels in the Hayase River system, Fukui Prefecture, which flows into the Japan Sea. Multiple approaches including investigation of glass eel recruitment, comparison of body size, and estimation of habitat use types was employed. During the observation period (from January to July 2010), no glass eels were found at the river mouth of the Hayase River in monthly sampling. Of eels collected in this study (n = 127), no eels smaller than the initial body size of eels for stocking were found in this water system and none were identified as being of wild origin based on the habitat use type classifications from otolith microchemistry (n = 48). This lack of evidence of Japanese eels recruiting into Japan Sea coast waters suggests most eels present there may be stocked eels. Japanese eels could have been distributed naturally along the Japan Sea coast more than in recent years, indicating a possible decrease of the natural distribution range of this species.

DOI： 10.1007/s10641-013-0193-8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer-Verlag Tokyo  

Catch statistics and biological data of the Japanese eel Anguilla japonica from 12 river systems in nine prefectures of Japan (36°N, 140°E-31°N, 130°E) during 1999-2004 were analyzed in order to evaluate the demography of A. japonica in Japan. Significant differences in biological characteristics of 6388 eels were found among the river systems. Fishery catches of eels in all locations have declined, but the magnitudes or patterns of decline seem to be different. Of sex-identified eels, mean total lengths ± SD (mm) of females (n = 3776) and males (n = 962) were 495.6 ± 104.3 and 412.9 ± 80.7, respectively, and overall sex ratio (% female) was 79.6 %. Mean age (years) and growth rate (mm year-1) were 5.0 ± 1.9 and 96.7 ± 38.6 for females (n = 3643) and 3.6 ± 1.7 and 120.5 ± 65.4 for males (n = 907), respectively. This study highlights the demographic heterogeneity of the A. japonica among the studied river systems, which suggests that it is important to conserve a variety of habitats in multiple river systems as an inclusive management target in addition to restoration of the diversity of habitats for eels in a single river system. © 2014 The Japanese Society of Fisheries Science.

DOI： 10.1007/s12562-014-0735-9

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER JAPAN KK  

The aim of this study was to examine the possible interspecific interactions between the freshwater eel Anguilla japonica and the marine conger eel Conger myriaster. Spatial distribution, foraging time, and diet were compared between 380 A. japonica and 221 C. myriaster juveniles in a large brackish water bay and a tributary river estuary. Almost no C. myriaster were caught in the estuary, but both species coexisted in the bay at similar densities. For both species, percentages of eels with stomach contents were greater in the morning than in the afternoon, indicating they forage at night. Both species mainly fed on benthic crustaceans in the bay, but the size of the main prey species, mud shrimp Upogebia major, was significantly larger in A. japonica. The difference in prey size appears to be related to the eel body size (A. japonica: 559.5 +/- A 88.0 mm, C. myriaster: 356.4 +/- A 56.0 mm), which probably reflects the differences in the life history-related movements of these eels, with A. japonica using the bay at large sizes and C. myriaster using the bay as a nursery area before moving to deeper water. The differences in their migratory and movement patterns may result in niche segregation in the brackish bay where both species coexist.

DOI： 10.1007/s12562-013-0628-3

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：日本生態学会  

We investigated the ichthyofauna of 18 temporary lentic water bodies along the river (floodplain sites), as well as reference sites including two isolated ponds, two oligotrophic wetland sites dominated by sphagnums, and four lentic tributaries (non-floodplain sites) in the Shubuto River System, SW Hokkaido. In total, 16 fish species belonging to eight families were recorded. Cluster analysis revealed three clusters containing both floodplain and non-floodplain sites and one cluster consisting of only floodplain sites. Three species, Lethenteron camtschaticum, Lethenteron sp. N, and Gymnogobius opperiens, were indicator species that were significantly associated with the only-floodplain cluster. Nestedness analysis showed that the fish species composition of the floodplain sites was significantly nested. Multiple regression and canonical correlation analyses demonstrated that fish diversity in floodplain sites was positively affected by water surface area and water depth and negatively affected by channel distance from the ocean. With reference to the results of the present study, we discussed the design of ecological restoration measures for the floodplains along the Shubuto River, which will contribute to the conservation of fish fauna.

DOI： 10.18960/hozen.18.1_55

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

The diet of Japanese eels, Anguilla japonica, was investigated using stomach content and stable isotope analyses. Stable isotope enrichment of carbon and nitrogen (Delta delta C-13 and Delta delta N-15) was first estimated for A. japonica by comparing the isotopic signatures (delta C-13 and delta N-15) of reared eels to that of their food. The estimated isotope enrichment was then applied to the diet estimation of A. japonica in the Kojima Bay-Asahi River system, Japan, combined with conventional stomach content analysis. Stable isotope enrichment varied among tissues, from 0.2aEuro degrees to 0.8aEuro degrees for carbon and from 1.3aEuro degrees to 2.1aEuro degrees for nitrogen. Nitrogen isotope enrichment of A. japonica muscle estimated in this study was 2.1aEuro degrees, which was different from the previously reported mean delta N-15 enrichment of several animals of 3.4aEuro degrees. These results indicate that isotope-based diet estimations for A. japonica need to use species- and tissue-specific values of isotope enrichment. In the diet analysis, stomach contents and stable isotopes revealed that (1) A. japonica appear to usually feed on a single type of prey species in each feeding session, (2) principal prey species were mud shrimp, Upogebia major, in brackish Kojima Bay and crayfish, Procambarus clarkia, in the Asahi River, (3) A. japonica in Kojima Bay primarily depend on the pelagic food web as a carbon source due to mud shrimp being filter feeders and eels in the Asahi River primarily depend on the littoral food web. Based on these results and the recently reported eel movements between Kojima Bay and the Asahi River, it appears that A. japonica can adapt to various feeding environments as opportunists, but also utilize the food resources by targeting a single type of prey species during a single feeding session.

DOI： 10.1007/s10641-012-0027-0

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

The age, total length (LT), head shape and skull shape were investigated for 379 Japanese eels Anguilla japonica sampled in freshwater and brackish areas of the Kojima BayAsahi River system, Okayama, Japan, to learn about the differentiation process of head-shape polymorphism. The relative mouth width (ratio of mouth width to LT) of A. japonica&gt;400mm LT collected in fresh water was significantly greater than that of fish collected in brackish water. Growth rates of mouth width and the distance from the snout to the midpoint of the eyes (the ratio of width and distance to age, respectively) were not significantly different between freshwater and brackish-water samples, whereas the somatic growth rate (the ratio of LT to age) of freshwater samples was significantly lower than that of brackish-water eel samples. These results suggest that the factors affecting head and somatic growth of A. japonica are not identical. According to these results and feeding patterns in each habitat reported by another study, it is suggested that somatic growth appears to play a significant role in the differentiation process of the head-shape polymorphism in A. japonica, with the slow-growing fish in fresh water becoming broad-headed and the fast-growing fish in brackish water becoming narrow-headed. (C) 2013 The Authors Journal of Fish Biology (C) 2013 The Fisheries Society of the British Isles

DOI： 10.1111/jfb.12070

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

To learn about the relationships between feeding and growth of temperate eels in freshwater and brackish water habitats, we analysed 533 yellow-phase Japanese eels Anguilla japonica collected in both types of habitats in southeastern Japan. Because male eels were very rare in each habitat (FW, N = 1; BW, N = 20), characteristics of female eels were compared between the different habitats. Annual food consumption was evaluated with the consideration of instantaneous food consumption and annual activity period. Stomach fullness index (stomach content weight/body weight) was used as an indicator of instantaneous food consumption. The ratios of number of months with eel catch to those when eel sampling was conducted were used as an indicator of activity period. Female yellow eels tended to be older and slower growing in fresh water (N = 78; age, mean +/- SD = 7.9 +/- 2.4 years; growth rate, 59.8 +/- 14.0 mm year-1) than in brackish water (N = 229; age, 5.5 +/- 1.8 years; growth rate, 90.1 +/- 24.4 mm year-1). Irrespective of sex, yellow eels in brackish water had a higher stomach fullness index and a greater ratio of months with eel catches, indicating greater annual food consumption by brackish water eels. These results indicate that greater annual food consumption contributes to the greater growth rates of Japanese eels in brackish water habitats.

DOI： 10.1111/eff.12010

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：動物考古学研究会  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：日本音響学会  

To understand the mechanism of the peripheral auditory system of the cephalopod statocyst, the frequency dependence of particle motion sensitivity in cephalopods was estimated using a physical model of the sensory system, which was assumed to be forced oscillation. Reported perception thresholds of Sepia officinalis, Octopus vulgaris, and O. ocellatus fit the model well at low frequencies, whereas at frequencies above 150 Hz, the empirically measured threshold increased more steeply than the predicted increment. These results indicate that the frequency response of the perception threshold of cephalopods to particle motion can be primarily understood using the forced oscillation model, while unknown factor(s) play a role in the higher frequency range. Cephalopods are thought to be sensitive to low-frequency particle motion rather than high-frequency motion. The evolutionary function of cephalopod acoustical perception is not clear
however, the data suggest that they recognize the low-frequency particle motion that may be generated by prey, predators, and conspecifics. © 2011 The Acoustical Society of Japan.

DOI： 10.1250/ast.32.255

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：東京大学大気海洋研究所  

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Other Link： http://hdl.handle.net/2261/35855

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER TOKYO  

The cephalopod receptor of particle motion was identified. In a previous study, it was suggested that statocysts served this function, but there was no direct supporting evidence, and epidermal hair cells had not been conclusively ruled out. Experiments on Octopus ocellatus were conducted using respiratory activity as an indicator of sound perception. Intact animals clearly responded to 141-Hz particle motion at particle accelerations below 1.3 x 10(-3) m/s(2), and the mean perception threshold at this frequency was approximately 6.0 x 10(-4) m/s(2). Specimens in which the statoliths had been surgically removed did not show any response for accelerations up to 3.9 x 10(-3) m/s(2) at 141 Hz, which was approximately 16 dB greater than the mean perception threshold at this frequency. Specimens that had undergone a control operation in which the statoliths remained intact showed positive responses at 2.8 x 10(-3) m/s(2) for the same frequency stimulus. This indicates that the statocyst, which is morphologically similar to the inner ear system in fish, is responsible for the observed responses to particle motion in O. ocellatus. This is the first direct evidence that cephalopods detect kinetic sound components using statocysts.

DOI： 10.1111/j.1444-2906.2008.01589.x

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：日本海洋音響学会  

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Total pages：237   Responsible for pages：18   Language：Japanese   Book type：Scholarly book

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Total pages：275   Responsible for pages：16   Language：Japanese   Book type：Scholarly book

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Poster presentation  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Poster presentation  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (invited, special)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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