著者
Michael Ford Nicholas Bezio Allen Collins
出版者
The Plankton Society of Japan, The Japanese Association of Benthology
雑誌
Plankton and Benthos Research (ISSN:18808247)
巻号頁・発行日
vol.15, no.4, pp.296-305, 2020-11-18 (Released:2020-11-12)
参考文献数
36

On April 10, 2015, three individuals of an undescribed species of ctenophore were observed moving just above the seafloor in the Arecibo Amphitheater inside the Guajataca Canyon, north-northwest of Puerto Rico at a depth of approximately 3,900 m. The ctenophore is distinctive; having two prominent tentacle arms, a body that is rectangular when observed laterally along the tentacular plane, and rounded when observed laterally along the stomodeal plane. The tentacle arms each give rise to an extensible tentacle bearing short tentilla of uniform length and distribution. One ctenophore appeared to be anchored to the seafloor by its two long flexible tentacles, as well as by two filaments exiting its oral end. The overall form of the ctenophore suggests classification within the problematic, non-monophyletic order Cydippida, but the robust tentacle arms are more reminiscent of benthic species of Platyctenida, particularly those of families Lyroctenidae and Ctenoplanidae. Whereas most platyctenid ctenophores do not possess ctene rows in their adult forms, features that are possessed by the new species described herein, species of Ctenoplanidae retain comb rows as adults and are capable of limited swimming. The species described herein is easily distinguishable from all other known species of Ctenophora and may trace its origin to a lineage diverging near the origin of Platyctenida.
著者
Sho Toshino Jun Nishikawa Khwanruan Srinui Supattra Taleb Hiroshi Miyake
出版者
The Plankton Society of Japan, The Japanese Association of Benthology
雑誌
Plankton and Benthos Research (ISSN:18808247)
巻号頁・発行日
vol.14, no.3, pp.143-149, 2019-08-26 (Released:2019-08-17)
参考文献数
29

The stings of box jellyfishes can be fatal, so knowing the fauna of a certain area is important to save lives. Five described and two still-undescribed species of Cubozoa have been reported from Thailand: Chironex indrasaksajiae, Chironex sp., Chiropsella sp., Chiropsoides buitendijki, Copula sivickisi, Morbakka fenneri, and Tripedalia cystophora. We made detailed observations of the morphology of two of the species newly recorded in Thailand: Alatina morandinii and Tripedalia binata. The molecular phylogeny of these species is also discussed. Additional investigations are needed to understand the diversity of Cubozoa in Thailand.
著者
Takahiro Sugiyama Naoto Jimi Ryutaro Goto
出版者
The Plankton Society of Japan, The Japanese Association of Benthology
雑誌
Plankton and Benthos Research (ISSN:18808247)
巻号頁・発行日
vol.15, no.4, pp.289-295, 2020-11-18 (Released:2020-11-12)
参考文献数
30

The Polynoidae, commonly known as “scale-worms” due to the scale-like elytra on the dorsal surface, contains many species living in symbioses with other invertebrates. Most of these symbionts are host-specific, but some have a wide range of hosts. The genus Asterophilia includes two species living in shallow subtropical to tropical waters in the Pacific Ocean as ectosymbionts of asteroids and, more rarely, crinoids. Here, we recorded Asterophilia culcitae from asteroid hosts (Culcita novaeguineae, Linckia laevigata, L. guildingi, and Leiaster leachi) and, for the first time, from holothurian hosts [Stichopus chloronotus, Holothuria atra, H. (Stauropora) pervicax, and Bohadschia argus] along warm Japanese Pacific coasts. The cytochrome c oxidase subunit I sequences of the specimens from holothurians did not differ significantly from those on asteroid hosts, proving that A. culcitae has a wide host range across three different echinoderm classes: asteroids, holothurians, and crinoids. The general body color of A. culcitae was constantly reddish (female) or whitish (male), regardless of the host body color, although a previous study suggested that it differs in accordance with the host body color. However, we found that one individual from a holothurian host showed a different color pattern: A. culcitae typically shows three whitish or yellowish elytral mounds that have been suggested to mimic the tube foot of the asteroid hosts, whereas one individual from S. chloronotus had reddish brown translucent mounds, which we suggest might be cryptic on its holothurian host.
著者
Luna Yamamori Makoto Kato
出版者
The Plankton Society of Japan, The Japanese Association of Benthology
雑誌
Plankton and Benthos Research (ISSN:18808247)
巻号頁・発行日
vol.14, no.2, pp.131-134, 2019-05-28 (Released:2019-05-24)
参考文献数
13

The rock-boring sea urchin, Echinostrephus molaris, excavates soft rocks, and the pits are later used by non-boring sea urchins such as Echinometra mathaei and Anthocidaris crassispina. The pits used by these non-boring sea urchins are also characteristically inhabited by a limpet-like algivorous trochid snail, Broderipia iridescens (Gastropoda, Trochidae). To determine how this unique symbiotic association is maintained, we observed reproduction and larval development of the snail, and performed assays to detect what induced settlement in the snail larvae. As candidates of settlement inducers, a habitat biofilm plate, the host and the non-host sea urchins, and conspecific snails were kept in separate glass bowls, and newly hatched B. iridescens veliger larvae were introduced to each bowl. Sixty to 80% of larvae settled in bowls that contained the non-boring host sea urchins and conspecific snails. On the other hand, only approximately 8% of the larvae settled in bowls containing the boring non-host sea urchins. This is the first report demonstrating that larval settlement of an algivore is induced not by the habitat biofilms, but by the symbiotic hosts.
著者
Avril H. Underwood Ilka Straehler-Pohl Teresa J. Carrette Jessica Sleeman Jamie E. Seymour
出版者
The Plankton Society of Japan, The Japanese Association of Benthology
雑誌
Plankton and Benthos Research (ISSN:18808247)
巻号頁・発行日
vol.13, no.4, pp.143-153, 2018-11-21 (Released:2018-11-14)
参考文献数
71
被引用文献数
1

This research presents the early life history stages of Malo maxima, a recently described tropical Australian cubozoan from the family Carukiidae, from sexual fertilisation to metamorphosis including planula, polyp, asexual reproductive strategies and young medusa. We discuss the similarities between M. maxima and two closely related carukiid species from Japan and Australia including morphology and behaviours previously undocumented in the class Cubozoa. All three carukiids can reproduce by mono-disk strobilation, a strategy common to all other orders of the class Scyphozoa but only recently described in Cubozoa.
著者
Chong Chen Leigh Marsh Jonathan T. Copley
出版者
The Plankton Society of Japan, The Japanese Association of Benthology
雑誌
Plankton and Benthos Research (ISSN:18808247)
巻号頁・発行日
vol.13, no.1, pp.25-27, 2018-02-28 (Released:2018-03-14)
参考文献数
16
被引用文献数
1

“Mating stacks” have been widely documented in calyptraeid slipper limpets, which are protandric and exhibit sequential hermaphroditism. Gigantopelta is a genus of peltospirid snails endemic to deep-sea hydrothermal vents containing two species, one distributed on the East Scotia Ridge in the Southern Ocean and another on the Southwest Indian Ridge in the Indian Ocean. Here, we report the observation that both species form extensive (often >15 individuals) “snail chains”. These chains are potentially analogous to ‘mating stacks’ of calyptraeids, or alternatively, maybe a behaviour to facilitate spermatophore transfer. Both Gigantopelta species apparently have separate sexes and are sexually mature at a small size. However, it remains unclear whether they undergo sex change during their life.
著者
Natasha Phillips Lawrence Eagling Chris Harrod Neil Reid Valentina Cappanera Jonathan Houghton
出版者
日本プランクトン学会、日本ベントス学会
雑誌
Plankton and Benthos Research (ISSN:18808247)
巻号頁・発行日
vol.12, no.2, pp.143-144, 2017-05-30 (Released:2017-06-06)
参考文献数
19
被引用文献数
10

This study presents new evidence of the extensive trophic role of gelatinous zooplankton by documenting typically non-marine predators, mallard ducks, feeding on hydrozoans in shallow, coastal environments.
著者
SAWAMOTO SHOZO MATSUMOTO RUI
出版者
日本プランクトン学会、日本ベントス学会
雑誌
Plankton & benthos research (ISSN:18808247)
巻号頁・発行日
vol.7, no.4, pp.203-206, 2012-11-01
被引用文献数
9

More than 50 specimens of the megamouth shark Megachasma pelagios have been reported so far, but biological observations on the species are still limited. We examined a female megamouth specimen that was captured by the bonito purse seine fishery in the Kuroshio Extension in July 2007 and donated to the Okinawa Churaumi Aquarium. The specimen was an immature female, 3,667 mm in total length and 361 kg in weight. The stomach contents measured 2,200 mL excluding the portion that was lost from the specimen before measurement. Detailed examination of a small part (14.6 mL) of the stomach contents revealed undamaged worm-like organisms, 10 partially damaged euphausiids and abundant fragmented pieces of euphausiids. The worm-like organisms were probably parasites such as tapeworms. The partially damaged euphausiids were identified as Euphausia pacifica except for one individual of Nematoscelis difficilis. Based on the number of fragmented right mandibles, which were less damaged than the other fragmented appendages, the total number of euphausiids in the stomach contents is estimated to be at least 18,000 individuals. The high abundance of euphausiids in the stomach contents suggests that the present specimen has fed on a swarm of E. pacifica in an oceanic area.
著者
Yusuke Kondo Shoma Okada Susumu Ohtsuka Takeshi Hirabayashi Aya Adachi Makoto Urata Sho Toshino Hiroshi Miyake Nanako O. Ogawa Naohiko Ohkouchi
出版者
The Plankton Society of Japan, The Japanese Association of Benthology
雑誌
Plankton and Benthos Research (ISSN:18808247)
巻号頁・発行日
vol.13, no.2, pp.66-74, 2018-05-30 (Released:2018-05-24)
参考文献数
50
被引用文献数
1 1

In this study, we investigated the trophic interactions between the Japanese giant box jellyfish, Morbakka virulenta, and fish in the central part of the Seto Inland Sea, western Japan, in autumn and winter. Occurring in the surface waters at nighttime, these cubomedusae, regardless of their size (1.5 to 22.5 cm in bell height), were found to be piscivorous, feeding mainly on the Japanese anchovy, as shown by their stomach contents analysis. This finding was supported by a stable isotopic analysis and by an unchanged cnidome, irrespective of the bell height of medusae. Their nocturnal occurrence near the surface often took place around the slack tide, during which the medusae were foraging with tentacles fully extended. Other associations between the medusae and fish were also observed at this time: presumed commensalism with juvenile Japanese horse mackerel, and predation by black scraper.
著者
Isao Sano Takumi Saito Jun-Ichi Miyazaki Akihisa Shirai Takeru Uechi Takaki Kondo Satoshi Chiba
出版者
The Plankton Society of Japan, The Japanese Association of Benthology
雑誌
Plankton and Benthos Research (ISSN:18808247)
巻号頁・発行日
vol.15, no.2, pp.97-111, 2020-05-27 (Released:2020-05-30)
参考文献数
81

The evolutionary history and diversity of unionoid mussels in East Asia need to be clarified and would shed light on the formation process of the unique fauna of Japan. Unionoid mussels (Mollusca: Bivalvia) are unique models for understanding the process by which organisms have diversified before and after the formation of the Japanese archipelago. Unionoid mussels have poor dispersal ability, so it is thought that they would have been strongly influenced by the archipelago’s formation. Therefore, the speciation and diversification processes of mussels before and after the archipelago’s formation were investigated by analyzing the nuclear and mitochondrial DNA of a wide range of species, particularly those inhabiting East Asia. The evolutionary history and divergence time of these mussels were examined. Unionoid mussels were found to have higher endemicity than other freshwater organisms. Although most of the endemic unionoid mussels of Japan are likely to have diverged before the formation of the Japanese archipelago, some other Japanese unionoid mussel species, including species endemic to Lake Biwa, an ancient lake in Japan, potentially diverged after the Japanese archipelago began to separate from the continent. This suggest that adaptation to the unique habitat of the ancient lake has caused diversification in the mussels endemic to it.
著者
Mitsuko Hidaka-Umetsu Dhugal J. Lindsay
出版者
The Plankton Society of Japan, The Japanese Association of Benthology
雑誌
Plankton and Benthos Research (ISSN:18808247)
巻号頁・発行日
vol.13, no.2, pp.41-45, 2018-05-30 (Released:2018-05-24)
参考文献数
14

An individual narcomedusa assignable to Solmissus incisa sensu lato was observed having ingested a fish at 573 m depth near the southeast slope of the Kaikata seamount, Japan. Solmissus is a very common deep-sea narcomedusan genus that is widely considered to be a predator specializing on gelatinous plankton. Several cryptic species, with differences in the number of tentacles and form of manubrial pouches, are thought to be included in the nominal species Solmissus incisa. Therefore, the present study gives a short description of the morphotype of Solmissus incisa s.l. observed with a fish in its stomach, as well as several individuals of the same morphotype that had ingested gelatinous prey.
著者
Yuka Kushida Hiroki Kise Catherine S. McFadden James Davis Reimer
出版者
The Plankton Society of Japan, The Japanese Association of Benthology
雑誌
Plankton and Benthos Research (ISSN:18808247)
巻号頁・発行日
vol.15, no.3, pp.259-268, 2020-08-14 (Released:2020-08-04)
参考文献数
48

Sea pens are ecologically important habitats for associated marine organisms, serving as ecosystem engineers in sandy or muddy seafloor environments. In such areas, sea pens can form habitats with high population densities known as “sea pen fields”. However, the presence and importance of sea pen fields have not been well studied in shallow waters in East Asia. Here, we report a sea pen field of Virgularia sp. aff. gustaviana in the shallow waters of Ushibuka Marine Park, in the Amakusa Islands of southern Japan. The average colony numbers of the field across all depths (7–20 m) was 10.3 colonies/m2 (live colonies) to 13.6 colonies/m2 (all: live+dead colonies+holes), and the area of the sea pen field was at least ∼50,000 m2. At a depth of 15 m, the substratum consisted of sand and fallen leaves of terrestrial origin, and the highest sea pen density was observed (averages=17.2 live colonies/m2, =25.8 total (live+dead+holes) colonies/m2). At a depth of 20 m, the substratum consisted of broken shells and rocks and had the lowest density (live colonies: average=0.8 colonies/m2, all: average=1.0 colonies/m2). There were significant differences in colony number of Virgularia sp. aff. gustaviana between the “sand”, “sand+leaves”, and “broken shells/rocks” substrates. We hypothesize that the strength of the water currents caused by local geographic features and tidal movements produce suitable sedimentation and habitat for this species of sea pen. Therefore, we suggest that preserving the natural coastline is crucial to protect this and other sea pen fields in shallow waters and their benthic marine communities.
著者
Yusuke Yamana Taiga Kunishima Masami Obuchi Takuma Fujii
出版者
The Plankton Society of Japan, The Japanese Association of Benthology
雑誌
Plankton and Benthos Research (ISSN:18808247)
巻号頁・発行日
vol.15, no.2, pp.168-177, 2020-05-27 (Released:2020-05-30)
参考文献数
11

With a focus on building an inventory of subtropical species of epifaunal holothurians and completing an environmental assessment, SCUBA surveys were carried out in the Amami Islands of Kagoshima Prefecture in southern Japan. The following 12 nominal species belonging to seven genera (subgenera), as well as two as yet undescribed species belonging to two genera, were observed: Bohadschia argus Jäger, 1833; B. bivittata Mitsukuri, 1912; B. vitiensis (Semper, 1867); Holothuria (Halodeima) atra Jäger, 1833; H.(H.) edulis Lesson, 1830; Holothuria (Microthele) nobilis (Selenka, 1867); Personothuria graeffei (Semper, 1867); Stichopus chloronotus Brandt, 1835; S. hermanni Semper, 1867; S. naso Semper, 1867; Thelenota anax H.L. Clark, 1921; Euapta sp.; Synapta maculata (Chamisso et Eysenhardt, 1821); and Opheodesoma sp. In the semi-closed waters around the Amami Islands, epifaunal holothurians showed what seemed to be species-specific distribution patterns related to topographical features. Furthermore, ignition loss values of feces and sediments suggested that selective deposit feeding may be predominant in at least several of the species sampled.
著者
Tatsuya Ishikawa Akira Kurashima
出版者
The Plankton Society of Japan, The Japanese Association of Benthology
雑誌
Plankton and Benthos Research (ISSN:18808247)
巻号頁・発行日
vol.15, no.2, pp.112-120, 2020-05-27 (Released:2020-05-30)
参考文献数
50

This study aimed to estimate the feeding pressure of a Diadema setosum population on a barren ground in Kata Bay, Mie Prefecture, Japan, which is a temperate region. We combined data of the feeding rate of D. setosum from tank experiments and of the D. setosum population dynamics obtained from monthly surveys. We conducted tank experiments to clarify the relationships between the feeding rate of D. setosum and the water temperature and test diameter of the sea urchins. The feeding rate and water temperature were positively correlated over the range of 15°C to 30°C. The test diameter composition of the D. setosum population in Kata Bay was stable throughout the study period (June 2014 to May 2015). The results revealed distinct seasonal changes in the feeding pressure of the D. setosum population owing to temperature variations.
著者
Itoh Hiroshi Nishida Shuhei
出版者
日本プランクトン学会、日本ベントス学会
雑誌
Plankton & benthos research (ISSN:18808247)
巻号頁・発行日
vol.2, no.3, pp.134-146, 2007-08-01
参考文献数
48
被引用文献数
3 9

A 17-month field survey and laboratory experiments were conducted to investigate the life cycle, seasonal population fluctuations, and salinity tolerance in the poecilostomatoid copepod Hemicyclops gomsoensis associated with the burrows of the mud shrimp Upogebia major and the ocypodid crab Macrophthalmus japonicus in the mud-flats of the Tama-River estuary, central Japan. On the basis of sample collections in the water column and from the burrows, it was revealed that H. gomsoensis is planktonic during the naupliar stages and settles on the bottom during the first copepodid stage to inhabit the burrows of U. major and, to a lesser extent, those of M. japonicus. While females carrying egg-sacs were present throughout the year, the copepods' reproduction took place mainly during early summer to autumn with a successive decrease from autumn to winter. Occasionally the copepod populations in the burrows suffered from severe flushes of river water that led to salinity decreases in the burrow water to fatal levels, but usually the salinity in the burrow was within optimal levels and permitted recovery and maintenance of the populations.
著者
Yusuke Yamana Hayato Tanaka
出版者
日本プランクトン学会、日本ベントス学会
雑誌
Plankton and Benthos Research (ISSN:18808247)
巻号頁・発行日
vol.12, no.2, pp.83-94, 2017-05-30 (Released:2017-06-06)
参考文献数
32

Two new taeniogyrinid sea cucumbers collected in the intertidal zone of southern Japan, Taeniogyrus verruculosus sp. nov. and Scoliorhapis sesokoensis sp. nov. are described. Both species possess a small body size (approximately 30–40 mm), light body color (translucent white in preserved specimens), ten tentacles, and numerous verrucous surfaces on the body, within which small (mostly less than 70 µm in length) sigmoid-hook ossicles are present. The two new species have a very similar external appearance to each other, however they do differ in the number of tentacle digits: T. verruculosus possesses up to eight digits, whereas S. sesokoensis possesses up to six. In both species, wheel papillae are not present. T. verruculosus possesses only a few small (mostly less than 30 µm in diameter) wheel ossicles in the anterior dorsal skin, which are not present in S. sesokoensis. Additionally, the DNA barcode sequences of two new species were determined and are available in the DDBJ/NCBI/GenBank databases under the accession numbers.
著者
Tatsuya Ishikawa Miyuki Maegawa Akira Kurashima
出版者
日本プランクトン学会、日本ベントス学会
雑誌
Plankton and Benthos Research (ISSN:18808247)
巻号頁・発行日
vol.11, no.4, pp.112-119, 2016-11-25 (Released:2016-11-23)
参考文献数
30
被引用文献数
4

This study examines the effects of the sea urchin Diadema setosum on algal composition, coverage and biomass on barren ground. In cage experiments, the effects of D. setosum density were examined at 5 levels over the range of 0–8 ind. m−2. Algal coverage and number of species, densities and lengths of Sargassum spp. on experimental blocks in each cage were measured monthly. In the cage without D. setosum, algal coverage and biomass were higher than in cages with D. setosum. For D. setosum density of 1 ind. m−2 and higher, decreased algal coverage and decreased biomass and density of Sargassum spp. were observed. D. setosum at a density higher than 2 ind. m−2 had a negative effect on algal species numbers. Consequently, algae could grow when the D. setosum density was fewer than 2 ind. m−2. This study revealed that grazing by D. setosum has a great effect on the seaweed bed ecosystems along the coast of central Japan.
著者
James Davis Reimer Takuma Fujii Hiroki Kise Kensuke Yanagi Katie Cook James Cant Keita Koeda Tatsuki Koido Takaya Kitamura Takuma Mezaki
出版者
The Plankton Society of Japan, The Japanese Association of Benthology
雑誌
Plankton and Benthos Research (ISSN:18808247)
巻号頁・発行日
vol.15, no.2, pp.185-187, 2020-05-27 (Released:2020-05-30)
参考文献数
13

The zooxanthellate scleractinian species Goniopora stokesi is widely distributed across the Indo-Pacific Ocean, and in Japan the northernmost records of this species are from Tatsukushi, Kochi on Shikoku, although these records are not associated with specimens deposited in museums. The species is unique among Goniopora in that it lives on soft bottom sediment, forming free-living colonies, and produces asexual daughter colonies, or ‘polyp balls,’ via budding from parent colonies. Here we report on a large G. stokesi community from Otsuki, Kochi, Japan, representing the northernmost specimen-based record of the species. Specimen-based records are important as verifiable baseline data in light of global warming and climate change, which is expected to drastically effect the marine flora and fauna of Kochi and surrounding areas.
著者
Koji Seike Ryutaro Goto
出版者
The Plankton Society of Japan, The Japanese Association of Benthology
雑誌
Plankton and Benthos Research (ISSN:18808247)
巻号頁・発行日
vol.15, no.3, pp.220-227, 2020-08-14 (Released:2020-08-04)
参考文献数
35

Burrows produced by marine invertebrates often harbor other small commensal invertebrates. The mud shrimp Upogebia is known to coexist with the myid bivalve Cryptomya in a burrow produced by the shrimp. Both species are filter-feeders, and thus interspecific competition or trophic niche segregation may occur in the burrow. Samples for carbon and nitrogen stable isotope analysis were collected from a tidal flat near the tidal inlet of Akkeshi Lake, Hokkaido, northern Japan in April 2013. In addition, stratified benthos sampling was conducted on the tidal flat in August 2018, to clarify the interspecific relationship between U. major and C. busoensis in the burrow. The stratified benthos sampling showed the vertical distribution of these species, and indicated that both species filter water from the same part of the burrow for feeding. The stable carbon and nitrogen isotope analysis showed that important food sources for both U. major and C. busoensis are marine phytoplankton and microphytobenthos. In addition, C. busoensis is likely to consume terrestrial organic matter whereas U. major is unable to utilize it. The partial trophic segregation between the species increases the potential benthic filtering because it allows the Upogebia burrow complex to consume a wide variety of organic matter, and it might reduce interspecific competition between the filter-feeding host and its commensal species. These results demonstrate how ecologically similar macrobenthos can coexist in a burrow.
著者
Yasuhide Nakamura Akihiro Tuji Wataru Makino Shin-ichiro S. Matsuzaki Nobuaki Nagata Megumi Nakagawa Noriko Takamura
出版者
The Plankton Society of Japan, The Japanese Association of Benthology
雑誌
Plankton and Benthos Research (ISSN:18808247)
巻号頁・発行日
vol.15, no.1, pp.44-54, 2020-02-28 (Released:2020-03-25)
参考文献数
40

Neomysis awatschensis is an important prey item for various fishes in Lake Kasumigaura, Japan. There is, however, a contradiction concerning the major food sources of this mysid species: whether “bottom mud”, “particulate organic matter (POM) including phytoplankton”, or “mesozooplankton” is the main diet, and this uncertainty may be due to differences in the methodology used to determine the prey items in previous studies. This study examined the main food sources of N. awatschensis by combining three methods to eliminate methodological biases: DNA metabarcoding, microscopy and stable isotope analysis. Planktonic diatoms and green algae sequences were the main taxa detected by DNA metabarcoding and microscopy on the fecal pellets. The δ15N values of the mysids were similar to those of phytoplankton feeders rather than carnivorous planktonic crustaceans. These results suggest that diatoms and green algae were the major food sources for N. awatschensis in Lake Kasumigaura during the investigation period, and that its trophic level is as low as that of herbivores. However, the partial contribution of other “POM” (e.g., benthic diatoms) is also implied, considering the dispersion in δ13C values. Mesozooplankton prey, such as copepods, were detected both using DNA metabarcoding and microscopy, but they could not be a major food source due to the low nitrogen stable isotopic signature of the mysids. The opportunistic feeding habits of N. awatschensis possibly explain the consistent dominance of this species in the lake, where the ecosystem structure was substantially changed because of successive desalination.