In Euthyneuran molluscs, the distribution and plethora of dopamine (DA) functions are likely coupled to the feeding ecology with a broad spectrum of modifications both in the central and peripheral neural systems. However, studies of benthic grazers currently dominate the analysis of DA-mediated signaling, whereas adaptations to pelagic lifestyles and other feeding strategies are unknown. Here, we characterize the distribution of central and peripheral neurons in representatives of distinct ecological groups: the pelagic predatory pteropod Clione limacina (Pteropoda, Gymnosomata) and its prey - Limacina helicina (Pteropoda, Thecosomata), as well as the plankton eater Melibe leonina (Nudipleura, Nudibranchia). By using tyrosine hydroxylase immunoreactivity as a reporter, we mapped their dopaminergic systems. Across all studied species, despite their differences in ecology, small numbers of dopaminergic neurons in the central ganglia contrast to an incredible density of these neurons in the peripheral nervous system, primarily representing sensory-like cells, which are predominantly concentrated in the chemotactic areas and project afferent axons to the central nervous system. Combined with tubulin immunoreactivity, this study illuminates the complexity of sensory signaling and peripheral neural systems in Euthyneuran molluscs with lineage-specific adaptations across different taxonomical and ecological groups.

Despite numerous studies on mercury in Arctic biota, data from inaccessible, ice-covered regions − especially during the polar night and late winter − remain scarce. This scarcity results in poor understanding of the seasonal dynamics of mercury within the food web. From the Northern Barents Sea, we quantified total mercury and the dietary descriptors δ15N and δ13C as long-term dietary signals (weeks to months) in biota to a) investigate the seasonal pelagic food web structure, b) seasonality in total mercury concentration, c) and its biomagnification in the food web. Mercury and dietary descriptors were analyzed in copepods, macrozooplankton (krill, amphipods, arrow worms and pteropods) and the fishes, Atlantic cod (Gadus morhua), polar cod (Boreogadus saida) and capelin (Mallotus villosus) during spring, late summer, early,and late winter. Seasonal changes were observed in δ15N values in some macrozooplankton and capelin, and some seasonal variation was observed across the food web with depleted δ13C values in spring and enriched δ13C values in late summer. Mercury concentrations were lower (range: 2.49 ng/g dw in the krill Thyssanossa sp. – 70.55 ng/g dw in the pelagic pteropod Clione limacina) than reported from other parts of the Arctic. We found a positive linear relationship between mercury and relative trophic position represented by δ15N, i.e., biomagnification, during all seasons, except in early winter. As Clione limacina likely had different turnover rates for mercury and stable isotopes resulting in low δ15N, but high mercury concentrations in early winter, compared to the other species in the food web, the pteropod was omitted from the regression. By omitting Clione limacina, biomagnification was similar across all seasons (R2adj = 0.45). Thus, we saw clear mercury biomagnification with consistent and little seasonal variation in this high Arctic marine food web despite large seasonal fluctuations in abiotic and biotic conditions.

Dopamine is one of the most versatile neurotransmitters in invertebrates. It’s distribution and plethora of functions is likely coupled to feeding ecology, especially in Euthyneura (the largest clade of molluscs), which presents the broadest spectrum of environmental adaptations. Still, the analyses of dopamine-mediated signaling were dominated by studies of grazers. Here, we characterize the distribution of dopaminergic neurons in representatives of two distinct ecological groups: the sea angel - obligate predatory pelagic mollusc Clione limacina (Pteropoda, Gymnosomata) and its prey - the sea devil Limacina helicina (Pteropoda, Thecosomata) as well as the plankton eater Melibe leonina (Nudipleura, Nudibranchia). By using tyrosine hydroxylase-immunoreactivity (TH-ir) as a reporter, we showed that the dopaminergic system is moderately conservative among euthyneurans. Across all studied species, small numbers of dopaminergic neurons in the central ganglia contrast to significant diversification of TH-ir neurons in the peripheral nervous system, primarily representing sensory-like cells, which predominantly concentrated in the chemotactic areas and projecting afferent axons to the central nervous system. Combined with α-tubulin immunoreactivity, this study illuminates the unprecedented complexity of peripheral neural systems in gastropod molluscs, with lineage-specific diversification of sensory and modulatory functions.

The pteropod mollusk, Clione limacina, is a useful model system for understanding the neural basis of behavior. Of particular interest are the unique swimming behavior and neural circuitry that underlies this swimming behavior. The swimming system of Clione has been studied by two primary groups-one in Russia and one in the United States of America-for more than four decades. The neural circuitry, the cellular properties, and ion channels that create and change the swimming locomotor rhythm of Clione-particularly mechanisms that contribute to swimming acceleration-are presented in this review.

In the Southern Ocean, the biomass of Clione limacina is relatively large in some sea areas, and the largest biological density was found in the survey reached 300 Ind /m3. The acoustic data were obtained from the scientific fish finder (SIMRAD EK60) on Xuelong polar research vessel during China's 32nd Antarctic expedition. The system operated at a frequency of 38 and 120kHz. The acoustic data obtained from the expedition were processed in the specialized software used by the Institute for Underwater Acoustic Survey and Analysis of Biological Resources (ECHOVIEW 6.1.72, MYRIAX, AUSTRILIA). Biological sampling was carried out by using a "Framed Antarctic Krill Resource Assessment with Double capsule trawl". The sampling net is double capsule structure, the network port is frame type, the size is 4 m×2 m, the net capsule net mesh is 15 mm. It was found that the target intensity of Clione limacina in the central Ocean was significantly stronger at 120 kHz, which was 12.97±0.61 dB stronger than 38 kHz in general.

Ctenophores, hydroid jellyfish, appendicularians, salpas, and the pteropoda mollusk Clione limacina , conditionally combined into the group of “jellyfish”, are found in the food of all Pacific salmon — chum salmon, pink salmon, sockeye salmon, coho salmon and chinook salmon, but only in chum salmon their share is most significant, which is shown both absolute criteria (CHIN-private index of gastric filling of certain species and groups of jelly beans) and relative (share of jelly in the total INJ-general index of stomach filling). In food, chum salmon were present in 45.0 % of samples, pink salmon — 11.0 %, sockeye salmon — 7.0 %, coho salmon — 3.3 %, chinook salmon — 1.1 %. Chum salmon is well adapted to nutrition with jelly, because. has a stomach many times larger than that of other salmon, and in the diet of gelatinous it takes first place among them. Thus, in the event of a shortage of the main food (crustaceans, fish, squid), the chum salmon, due to the ability to consume and assimilate low-calorie food in large volumes, receives additional benefits in competitive relations with salmon and other pelagic fish.

Particulate organic matter release below melting sea ice (Terra Nova Bay, Ross Sea, Antarctica): Possible relationships with zooplankton

Synopsis Both nitric oxide (NO) and serotonin (5HT) mediate swim acceleration in the marine mollusk, Clione limacina. In this study, we examine the role that the second messenger, cyclic guanosine monophosphate (cGMP), plays in mediating NO and 5HT-induced swim acceleration. We observed that the application of an analog of cGMP or an activator of soluble guanylyl cyclase (sGC) increased fictive locomotor speed recorded from Pd-7 interneurons of the animal’s locomotor central pattern generator. Moreover, inhibition of sGC decreased fictive locomotor speed. These results suggest that basal levels of cGMP are important for slow swimming and that increased production of cGMP mediates swim acceleration in Clione. Because NO has its effect through cGMP signaling and because we show herein that cGMP produces cellular changes in Clione swim interneurons that are consistent with cellular changes produced by 5HT application, we hypothesize that both NO and 5HT function via a common signal transduction pathway that involves cGMP. Our results show that cGMP mediates NO-induced but not 5HT-induced swim acceleration in Clione.

Each pedal ganglion of the pteropod mollusc Clione limacina contains a cluster of serotonin-immunoreactive neurons that have been shown to modulate contractions of the slow-twitch musculature of the wing-like parapodia, and contribute to swim accelerations. Each cluster has a variable number of neurons, between 5 and 9, but there is no significant difference between right and left ganglia. In experiments with electrophysiological recordings followed by dye-injection (carboxyfluorescein), the clusters were found to contain two subsets of neurons. The majority innervate the ipsilateral wing via nerve n4. Two of the neurons in each cluster send processes out of the pedal ganglion in nerves n3 and n8. The processes in nerve n3 innervate the body wall of the neck region, while those in nerve n8 innervate the body wall of the tail. The baseline electrophysiological activity of the two subsets of neurons was different as "wing" neurons had constant barrages of small synaptic activity, while the "body wall" neurons had few synaptic inputs. The potential roles of the Pd-SW cluster in swim acceleration (wing neurons) and control of fluid pressure in the body and wing hemocoelic compartments (body wall neurons) are discussed.

Pteropods from the Kuril-Kamchatka Trench and the sea of Okhotsk (Euopisthobranchia; Gastropoda)

The pteropod mollusc Clione limacina is a feeding specialist, preying on shelled pteropods of the genus Limacina. Specialized prey-capture structures, called buccal cones, are hydraulically everted from within the mouth to capture the prey. Once captured, the prey is manipulated so the shell opening is over the mouth of Clione. Analyses of high-speed cine sequences of prey capture suggest that the mouth is actively opened rather than passively forced open by buccal cone eversion. The inflated buccal cones are initially straight and form a wide angle (maximum, 113°) prior to prey contact. Individual buccal cones bend orally following prey contact, suggesting a sensory trigger. To determine the muscular basis of buccal cone movements, the musculature of the buccal cones is described. Three distinct muscle fiber types include circular smooth muscle, longitudinal smooth muscle, and longitudinal striated muscle. The organization, distribution, and innervation of the muscle types suggest that circular muscle is used during buccal cone eversion, longitudinal smooth muscle is used for buccal cone withdrawal, and longitudinal striated muscle is used for oral bending of the buccal cones after prey contact and for manipulation of the prey.

Pteropods are a group of small marine gastropods that are highly sensitive to multiple stressors associated with climate change. Their trophic ecology is not well studied, with most research having focused primarily on the effects of ocean acidification on their fragile, aragonite shells. Stable isotopes analysis coupled with isotope‐based Bayesian niche metrics is useful for characterizing the trophic structure of biological assemblages. These approaches have not been implemented for pteropod assemblages. We used isotope‐based Bayesian niche metrics to investigate the trophic relationships of three co‐occurring pteropod species, with distinct feeding behaviors, sampled from the Southern Kerguelen Plateau area in the Indian Sector of the Southern Ocean—a biologically and economically important but poorly studied region. Two of these species were gymnosomes (shell‐less pteropods), which are traditionally regarded as specialist predators on other pteropods, and the third species was a thecosome (shelled pteropod), which are typically generalist omnivores. For each species, we aimed to understand (a) variability and overlap among isotopic niches; and (b) whether there was a relationship between body size and trophic position. Observed isotopic niche areas were broadest for gymnosomes, especially Clione limacina antarctica, whose observed isotopic niche area was wider than expected on both δ13C and δ15N value axes. We also found that trophic position significantly increased with increasing body length for Spongiobranchaea australis. We found no indication of a dietary shift toward increased trophic position with increasing body size for Clio pyramidata f. sulcata. Trophic positions ranged from 2.8 to 3.5, revealing an assemblage composed of both primary and secondary consumer behaviors. This study provides a comprehensive comparative analysis on trophodynamics in Southern Ocean pteropod species, and supports previous studies using gut content, fatty acid and stable isotope analyses. Combined, our results illustrate differences in intraspecific trophic behavior that may be attributed to differential feeding strategies at species level.

Stable isotope analysis (SIA) is a powerful tool to estimate dietary links between polar zooplankton. However, the presence of highly variable 12 C-rich lipids may skew estimations as they are depleted in 13 C relative to proteins and carbohydrates, consequently masking carbon signals from food sources. Lipid effects on pteropod-specific values requires examining, since accounting for lipids is rarely conducted among the few existing pteropod-related SIA studies. It is currently unclear whether lipid correction is necessary prior to SIA of pteropods. Whole bodies of three species of pteropods (Clio pyramidata f. sulcata, Clione limacina antarctica, and Spongiobranchaea australis) sampled from the Southern Ocean were lipid-extracted chemically to test the effects on δ13 C and δ15 N values (n = 38 individuals in total). We determined the average change in δ13 C values for each treatment, and compared this offset with those from published normalization models. We tested lipid correction effects on isotopic niche dispersion metrics to compare interpretations surrounding food web dynamics. Pteropods with lipids removed had δ13 C values up to 4.5‰ higher than bulk samples. However, lipid extraction also produced higher δ15 N values than bulk samples. Isotopic niche overlaps between untreated pteropods and their potential food sources were significantly different from overlaps generated between lipid-corrected pteropods and their potential food sources. Data converted using several published normalization models did not reveal significant differences among various calculated niche metrics, including standard ellipse and total area. We recommend accounting for lipids via chemical extraction or mathematical normalization before applying SIA to calculate ecological niche metrics, particularly for organisms with moderate to high lipid content such as polar pteropods. Failure to account for lipids may result in misinterpretations of niche dimensions and overlap and, consequently, trophic interactions.

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 609:133-149 (2019) - DOI: https://doi.org/10.3354/meps12837 Lipid and fatty acid turnover of the pteropods Limacina helicina, L. retroversa and Clione limacina from Svalbard waters Lauris Boissonnot1,2,*, Barbara Niehoff1, Benedikt Ehrenfels2,3, Janne E. Søreide2, Wilhelm Hagen4, Martin Graeve1 1Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany 2University Centre in Svalbard, 9171 Longyearbyen, Norway 3University of Bayreuth, Universitätsstrasse 30, 95447 Bayreuth, Germany 4BreMarE Bremen Marine Ecology, Marine Zoology, University of Bremen, 28334 Bremen, Germany *Corresponding author: lauris.boissonnot@gmail.com ABSTRACT: This study aimed at a better understanding of the fatty acid (FA) turnover in Arctic pteropods. Thecosome pteropods, i.e. Limacina helicina (juveniles and adults) and L. retroversa (adults), were collected in summer/autumn in Kongsfjorden and Isfjorden (Svalbard, 78° N) and, for the first time, successfully fed with 13C-labeled algae for 6 d. The gymnosome pteropod Clione limacina was sampled in summer in northern Svalbard and fed with 13C-labeled L. retroversa for 23 d. FA compositions were determined by gas chromatography, and 13C enrichment of FAs was analyzed by compound-specific isotope analysis. Among the thecosomes, maximum lipid turnover occurred in L. retroversa adults (1.3% d-1). L. helicina adults and juveniles showed lower lipid turnover rates (0.1 and 0.2% d-1, respectively). The thecosomes exhibited the ability to assimilate omega-3 FAs (up to 8.0% d-1). The lipid turnover rate of C. limacina averaged at only 0.07% d-1. However, C. limacina clearly showed the unusual capacity of de novo synthesis of odd-chain FAs (up to 1.2% d-1). Lipid turnover rates of pteropods were lower than those reported for Arctic copepods. However, pteropods may play a substantial role in the transfer of lipids to higher trophic levels, especially in autumn, when copepods have descended from the upper layers of the water column. The pteropods also showed the capacity to channel particular compounds such as omega-3 and odd-chain FAs, and therefore could be important for the functional diversity of the Arctic zooplankton community. KEY WORDS: Fatty acid assimilation · Trophic transfer · Omega-3 fatty acids · 13C labeling · Compound-specific isotope analysis · CSIA · Arctic Full text in pdf format PreviousNextCite this article as: Boissonnot L, Niehoff B, Ehrenfels B, Søreide JE, Hagen W, Graeve M (2019) Lipid and fatty acid turnover of the pteropods Limacina helicina, L. retroversa and Clione limacina from Svalbard waters. Mar Ecol Prog Ser 609:133-149. https://doi.org/10.3354/meps12837 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 609. Online publication date: January 17, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

Abstract The locomotory musculature of the pteropod Clione limacina includes slow‐twitch, fatigue‐resistant muscle fibers and fast‐twitch fatigable fibers. Dorsal musculature produces a dorsal bend of the wing, while ventral musculature produces a ventral bend. During the change to fast swimming, ~10% of the slow‐twitch fibers, including both dorsal and ventral fibers, exhibit fast repetitive firing that greatly exceeds the in‐phase excitation of the appropriate wing musculature. The normal wing‐beat frequency for fast swimming is 2–4 Hz, while repetitive firing occurs at 11 Hz. A component of fast‐swimming control is excitation of Pd‐SW neurons of the pedal ganglion. These cells are serotonin immunoreactive, and they innervate the slow‐twitch musculature of the wing. Induced excitation of a Pd‐SW neuron was capable of triggering repetitive firing in some slow‐twitch muscle cells. Repetitive firing in a subset of muscle fibers of the swim musculature could represent a contribution to wing stiffening, which has been documented to occur during the change to fast swimming.

Hyperiidean amphipods are a major prey for fish and seabirds. In the Southern Ocean, they are particularly abundant, with distributions ranging from the Polar Frontal Zone to Antarctic shelf waters. The species Hyperiella dilatata has previously been reported to show a peculiar anti-predatory behaviour: It captures chemically protected, gymnosome pteropods in the water column and carries them on its dorsum, like a backpack. We report this association at four oceanic sampling sites between latitudes 45° and 71° S. Molecular barcodes of both hosts and pteropods are provided and compared with those of other hyperiidean and pteropod specimens. Morphological identifications as well as molecular analyses show a so far undocumented association of Hyperiella antarctica with the pteropod Spongiobranchaea australis in the Polar Frontal Zone (Lazarev Sea). H. dilatata carried Clione limacina antarctica specimens in the Weddell Sea, as recorded previously for the Ross Sea. Lengths of the abducted pteropods varied between 1 and 5 mm, with the biggest pteropod measuring more than half the host’s size. One of the abducting amphipods was a female carrying eggs. The formation of such tandem is known to be very efficient as protection from visually hunting icefish in the crystal-clear coastal waters around the Antarctic continent; however, in the open ocean, this behaviour was so far undocumented. Here, we develop hypotheses on its origin and function.

Abstract The abundance and horizontal distribution of three pteropod species,Limacina helicina, Limacina retroversaandClione limacinawere examined in the western entrance of the Barents Sea (Polar Front region) in August 2011. Sixteen samples were collected from 8 sampling sites located along a latitudinal transect. The southern part of the study area (south of 73°N) was dominated byL. retroversa, whileL. helicinawas mostly observed north of 73°N. Surface water temperature differences between the coldest and the warmest station were around 8°C. The highest density ofL. retroversawas found in the south, near the Norwegian coast (nearly 52 000 ind. 1000 m−3), while the highest density ofL. helicinawas observed in the region of the Arctic water masses (nearly 13 000 ind. 1000 m−3). The sampled population of pteropods comprised mainly juvenile stages. Redundancy analysis (RDA) of the relationships between environmental factors (mean and surface salinity, mean temperature, sampling depth, chlorophyll concentration) and the population structure showed that mean temperature was the most important factor in the study area, explaining 70.5% of the pteropod community variation.

Abstract In the pteropod mollusc Clione limacina Phipps 1774, individuals possess an open circulatory system that fills their body cavities and functions as a hydrostatic skeleton. Individuals of C. limacina demonstrate two distinct swimming behaviors, slow and fast swimming, and their wings are supported by their hydrostatic skeleton. We investigated the circulation of fluid within the body cavities of individuals of C. limacina by injecting dye into the hemocoelic compartments to visualize flow during both slow swimming and serotonin‐induced fast swimming. Hemocoelic fluid was observed to have a defined pattern of flow: rostrally from the heart into the wings and head, then following a dorsal pathway caudally into the body and tail before being taken up by the heart again. During patterned attack behavior, the neck constricted in width as the head's buccal cones were hydraulically inflated with hemocoelic fluid.

Assembly of a reference transcriptome for the gymnosome pteropod Clione limacina and profiling responses to short-term CO2 exposure

Macrozooplankton of the Arctic – The Kara Sea in relation to environmental conditions