scholarly journals Have the eyes of bioluminescent scale worms adapted to see their own light? A comparative study of eyes and vision in Harmothoe imbricata and Lepidonotus squamatus

2021 ◽  
Author(s):  
A. Garm ◽  
S. H. Simonsen ◽  
P. Mendoza-González ◽  
K. Worsaae
Keyword(s):  
Comparative Study ◽  
Temporal Resolution ◽  
North Atlantic ◽  
Gaze Direction ◽  
The Gaze ◽  
Eye Morphology ◽  
The North ◽  
Peak Sensitivity ◽  
The North Atlantic ◽  
Behavioural Experiments

Annelids constitute a diverse phylum with more than 19000 species, exhibiting greatly varying morphologies and lifestyles ranging from sessile detritivores to fast swimming active predators. The lifestyle of an animal is closely linked to its sensory systems not least the visual equipment. Interestingly, many errant annelid species from different families such as the scale worms, Polynoidae, share the same two pairs of eyes on their prostomium. These eyes are typically 100-200 µm in diameter and structurally similar judged from the gross morphology. The polynoids, Harmothoe imbricata and Lepidonotus squamatus from the North Atlantic are both benthic predators preying on small invertebrates but only H. imbricata can produce bioluminescence in their scales. Here we have examined their eye morphology, photoreceptor physiology, and light guided behaviour in order to assess their visual capacity and visual ecology. Whereas the structure and physiology of the two pairs of eyes are remarkably similar within species, the only difference being the gaze direction, the photoreceptor physiology differs between the two species. Both species express a single opsin in their eyes but in H. imbricata the peak sensitivity is green shifted and the temporal resolution is lower, suggesting that the eyes of H. imbricata are adapted to detect their own bioluminescence. The behavioural experiments showed that both species are strictly night active but yielded no support to the hypothesis that H. imbricata are repelled by their own bioluminescence.

scholarly journals Freshwater pearl mussels from northern Sweden serve as long-term, high-resolution stream water isotope recorders

2019 ◽  
Author(s):  
Bernd R. Schöne ◽  
Aliona E. Meret ◽  
Sven M. Baier ◽  
Jens Fiebig ◽  
Jan Esper ◽  
...  
Keyword(s):  
High Resolution ◽  
Carbon Isotope ◽  
Temporal Resolution ◽  
North Atlantic ◽  
Stream Water ◽  
Winter Precipitation ◽  
The Arctic ◽  
Isotope Signature ◽  
The North ◽  
The North Atlantic

Abstract. The stable isotope composition of lacustrine sediments is routinely used to infer Late Holocene changes in precipitation over Scandinavia and ultimately, atmospheric circulation dynamics in the North Atlantic realm. However, such archives provide only low temporal resolution (ca. 15 years) precluding the ability to identify changes on inter-annual and quasi-decadal time-scales. Here we present a new, high-resolution reconstruction using shells of freshwater pearl mussels, Margaritifera margaritifera, from three rivers in north Sweden. We present seasonally to annually resolved, calendar-aligned stable oxygen and carbon isotope data from ten specimens covering the time interval of 1819 to 1998. The studied bivalves formed their shells near equilibrium with the oxygen isotope signature of ambient water and thus reflected hydrological processes in the catchment as well as changes, albeit damped, of the isotope value of local atmospheric precipitation. Shell oxygen isotopes were correlated significantly with the North Atlantic Oscillation index (up to 56 % explained variability) suggesting that moisture from which winter precipitation formed originated predominantly in the North Atlantic during NAO+ years, but in the Arctic during NAO– years. The specific isotope signature of winter precipitation was damped in stream water and this effect was recorded by the shells. Shell stable carbon isotope values did not show consistent ontogenetic trends, but rather oscillated around an average that differed slightly among the studied rivers (ca. −12.00 to −13.00 ‰). Results of this study contribute to an improved understanding of climate dynamics in Scandinavia and the North Atlantic sector and can help to constrain ecological changes in riverine ecosystems. Moreover, long isotope records of precipitation and streamflow are pivotal for improving our understanding and modeling of hydrological, ecological, biogeochemical and atmospheric processes. Our new approach offers a much higher temporal resolution and superior dating control than existing archives.

scholarly journals Freshwater pearl mussels from northern Sweden serve as long-term, high-resolution stream water isotope recorders

2020 ◽  
Vol 24 (2) ◽  
pp. 673-696
Author(s):  
Bernd R. Schöne ◽  
Aliona E. Meret ◽  
Sven M. Baier ◽  
Jens Fiebig ◽  
Jan Esper ◽  
...  
Keyword(s):  
High Resolution ◽  
Carbon Isotope ◽  
Temporal Resolution ◽  
North Atlantic ◽  
Stream Water ◽  
Winter Precipitation ◽  
Northern Sweden ◽  
Isotope Signature ◽  
The North ◽  
The North Atlantic

Abstract. The stable isotope composition of lacustrine sediments is routinely used to infer Late Holocene changes in precipitation over Scandinavia and, ultimately, atmospheric circulation dynamics in the North Atlantic realm. However, such archives only provide a low temporal resolution (ca. 15 years), precluding the ability to identify changes on inter-annual and quasi-decadal timescales. Here, we present a new, high-resolution reconstruction using shells of freshwater pearl mussels, Margaritifera margaritifera, from three streams in northern Sweden. We present seasonally to annually resolved, calendar-aligned stable oxygen and carbon isotope data from 10 specimens, covering the time interval from 1819 to 1998. The bivalves studied formed their shells near equilibrium with the oxygen isotope signature of ambient water and, thus, reflect hydrological processes in the catchment as well as changes, albeit damped, in the isotope signature of local atmospheric precipitation. The shell oxygen isotopes were significantly correlated with the North Atlantic Oscillation index (up to 56 % explained variability), suggesting that the moisture that winter precipitation formed from originated predominantly in the North Atlantic during NAO+ years but in the Arctic during NAO− years. The isotope signature of winter precipitation was attenuated in the stream water, and this damping effect was eventually recorded by the shells. Shell stable carbon isotope values did not show consistent ontogenetic trends, but rather oscillated around an average that ranged from ca. −12.00 to −13.00 ‰ among the streams studied. Results of this study contribute to an improved understanding of climate dynamics in Scandinavia and the North Atlantic sector and can help to constrain eco-hydrological changes in riverine ecosystems. Moreover, long isotope records of precipitation and streamflow are pivotal to improve our understanding and modeling of hydrological, ecological, biogeochemical and atmospheric processes. Our new approach offers a much higher temporal resolution and superior dating control than data from existing archives.

Mid-Cretaceous (Albian-Cenomanian) calcareous nannofossils from Pont du Fahs (northern Tunisia)

1981 ◽  
Vol 118 (2) ◽  
pp. 161-174 ◽  
Author(s):  
Minoo Hojjatzadeh
Keyword(s):  
United States ◽  
Comparative Study ◽  
North Africa ◽  
North Atlantic ◽  
Western Europe ◽  
Calcareous Nannofossils ◽  
Northern Tunisia ◽  
The North ◽  
The North Atlantic

SummaryCalcareous nannofossils from mid-Cretaceous (Albian-Cenomanian) sections at Pont du Fahs (northern Tunisia) allow the recognition of three nannofossil zones-the Prediscosphaera cretacea Zone, the Hayesites albiensis Zone, and the Eiffellithus turriseffeli Zone. A comparative study has been made of the nannofossil assemblages from Pont du Fahs and 14 other sites in North Africa, Western Europe, the North Atlantic and United States.

scholarly journals Influence of bloom dynamics on Particle Export Efficiency in the North Atlantic: a comparative study of radioanalytical techniques and sediment traps

2016 ◽  
Vol 186 ◽  
pp. 198-210 ◽  
Author(s):  
E. Ceballos-Romero ◽  
F.A.C. Le Moigne ◽  
S. Henson ◽  
C.M. Marsay ◽  
R.J. Sanders ◽  
...  
Keyword(s):  
Comparative Study ◽  
North Atlantic ◽  
Sediment Traps ◽  
The North ◽  
The North Atlantic ◽  
Particle Export

The Nebaliacea (Crustacea: Leptostraca) of the Rockall Trough

1983 ◽  
Vol 63 (3) ◽  
pp. 627-631 ◽  
Author(s):  
J. Mauchline ◽  
J. D. Gage
Keyword(s):  
Comparative Study ◽  
North Atlantic ◽  
The North ◽  
Rockall Trough ◽  
The North Atlantic ◽  
The Mediterranean

Three species of leptostracan malacostracous Crustacea occur in the Rockall Trough. The epibenthic Nebalia typhlops, previously recorded at depths of 200–500 m in the north Atlantic but to 1100 m in the Mediterranean, was found at depths of 1990–2925 m. The epibenthic Nebaliella caboti, previously recorded in the northwestern Atlantic at depths of 378 and 2085 m, was caught in the Rockall Trough at 1390–29000 m. The pelagic Nebaliopsis typica only occurred in samples from depths greater than 1500 m. A comparative study of the previously recognized species within the Nebaliacea is required.

The Currents of the North Atlantic

1892 ◽  
Vol 34 (872supp) ◽  
pp. 13940-13941
Author(s):  
Richard Beynon
Keyword(s):  
North Atlantic ◽  
The North ◽  
The North Atlantic

NATO adaptation to current challenges and mechanisms of Ukraine’s cooperation with the North Atlantic Treaty Organization

2019 ◽  
pp. 73-81
Author(s):  
Oleh Poshedin
Keyword(s):  
North Atlantic ◽  
Task Force ◽  
Response Force ◽  
Cyber Attack ◽  
Adaptation Measures ◽  
Joint Force ◽  
Security Environment ◽  
The North ◽  
The North Atlantic ◽  
Area Of Influence

The purpose of the article is to describe the changes NATO undergoing in response to the challenges of our time. Today NATO, as a key element of European and Euro-Atlantic security, is adapting to changes in the modern security environment by increasing its readiness and ability to respond to any threat. Adaptation measures include the components required to ensure that the Alliance can fully address the security challenges it might face. Responsiveness NATO Response Force enhanced by developing force packages that are able to move rapidly and respond to potential challenges and threats. As part of it, was established a Very High Readiness Joint Task Force, a new Allied joint force that deploy within a few days to respond to challenges that arise, particularly at the periphery of NATO’s territory. NATO emphasizes, that cyber defence is part of NATO’s core task of collective defence. A decision as to when a cyber attack would lead to the invocation of Article 5 would be taken by the North Atlantic Council on a case-by-case basis. Cooperation with NATO already contributes to the implementation of national security and defense in state policy. At the same time, taking into account that all decision-making in NATO based on consensus, Ukraine’s membership in the Alliance quite vague perspective. In such circumstances, in Ukraine you often can hear the idea of announcement of a neutral status. It is worth reminding that non-aligned status did not save Ukraine from Russian aggression. Neutral status will not accomplish it either. All talks about neutrality and the impossibility of Ukraine joining NATO are nothing but manipulations, as well as recognition of the Ukrainian territory as Russian Federation area of influence (this country seeks to sabotage the Euro-Atlantic movement of Ukraine). Think about it, Moldova’s Neutrality is enshrined in the country’s Constitution since 1994. However, this did not help Moldova to restore its territorial integrity and to force Russia to withdraw its troops and armaments from Transnistria.

Sign in / Sign up

Export Citation Format

Share Document