On the record of the Lessepsian migrant Fistularia commersonii (Rüppell, 1835) from the Adriatic Sea

On 7 November and 15 December 2006, two specimens of the Lessepsian migrant Fistularia commersonni were caught in trammel nets off the coastal waters of Tricase Porto (southwestern Adriatic, Italy) and Sveti Andrija (southeastern Adriatic, Croatia), respectively. These represent the first records of this species in the Adriatic Sea

Introduced marine species in Croatian waters (Eastern Adriatic Sea)

The Croatian part of the Adriatic Sea covers more than 35% of the total Croatian territory, which means that monitoring changes in marine ecosystems and the conservation of biodiversity are of great importance. Following global changes, Croatia is experiencing increasing problems due to the introduction of new species that include aliens (due to aquaculture activities and shipping) and species from other Mediterranean subregions that are extending their geographic range. This work provides a checklist of introduced species in Croatian waters. A total of 113 species (15 phytoplankton, 16 zooplankton, 16 macroalgae, 44 zoobenthic and 22 fish species) have been recorded in the eastern part of the Adriatic Sea, of which 61 species are alien and 52 introduced, due to climate change

Call properties and morphology of the sound-producing organ in <i>Ophidion rochei</i> (Ophidiidae)

The anatomical structures of the sound-producing organ in Ophidion rochei males present an important panel of highly derived characters: three pairs of putatively slow sonic muscles; a neural arch that pivots; a rocker bone at the front pole of the swimbladder; a stretchable swimbladder fenestra; a swimbladder plate; and an internal cone that terminates in a pair of membranes in the caudal swimbladder. Male courtship calls are produced nocturnally and consist of trains of 10 to 40 pulses that increase in amplitude and decrease in rate before exhibiting alternating periods of ca. 84 and 111 ms. Each pulse includes an unusual waveform with two parts. Pulse part 1 is a single cycle followed by a longer duration pulse part that exhibits gradual damping. Sounds and morphology suggest two hypotheses on the sound-producing mechanism. The ‘pulley’ hypothesis would require an alternate contraction of the ventral and dorsal muscles to form the two parts of each pulse. The ‘bow’ hypothesis involves a release mechanism with the sustained contraction of the dorsal muscle during all of the call, and the rapid contraction/relaxation of the ventral muscle to form each pulse

Characteristic features of the temperature dependence of the surface impedance in polycrystalline MgB2_2 samples

The real $R_s(T)$ and imaginary $X_s(T)$ parts of the surface impedance $Z_s(T)=R_s(T)+iX_s(T)$ in polycrystalline MgB$_2$ samples of different density with the critical temperature $T_c\approx 38$ K are measured at the frequency of 9.4 GHz and in the temperature range $5\le T<200$ K. The normal skin-effect condition $R_s(T)=X_s(T)$ at $T\ge T_c$ holds only for the samples of the highest density with roughness sizes not more than 0.1 $\mu$m. For such samples extrapolation $T\to 0$ of the linear at $T<T_c/2$ temperature dependences $\lambda_L(T)=X_s(T)/\omega\mu_0$ and $R_s(T)$ results in values of the London penetration depth $\lambda_L(0)\approx 600$ \AA and residual surface resistance $R_{res}\approx 0.8$ m$\Omega$. In the entire temperature range the dependences $R_s(T)$ and $X_s(T)$ are well described by the modified two-fluid model.Comment: 7 pages, 3 figures. Europhysics Letters, accepted for publicatio

Non-linear microwave impedance of short and long Josephson Junctions

The non-linear dependence on applied $ac$ field ($b_{\omega}$) or current ($i_{\omega}$) of the microwave (ac) impedance $R_{\omega}+iX_{\omega}$ of both short and long Josephson junctions is calculated under a variety of excitation conditions. The dependence on the junction width is studied, for both field symmetric (current anti-symmetric) and field anti-symmetric (current symmetric) excitation configurations.The resistance shows step-like features every time a fluxon (soliton) enters the junction, with a corresponding phase slip seen in the reactance. For finite widths the interference of fluxons leads to some interesting effects which are described. Many of these calculated results are observed in microwave impedance measurements on intrinsic and fabricated Josephson junctions in the high temperature superconductors, and new effects are suggested. When a $$ field ($b_{dc}$) or current ($i_{dc}$) is applied, interesting phase locking effects are observed in the ac impedance $Z_{\omega}$. In particular an almost periodic dependence on the dc bias is seen similar to that observed in microwave experiments at very low dc field bias. These results are generic to all systems with a $\cos (\phi)$ potential in the overdamped limit and subjected to an ac drive.Comment: 7 pages, 11 figure

New records of rare species in the Mediterranean Sea (October 2021)

This Collective Article presents information about 27 taxa belonging to five Phyla (one Ochrophyta, one Cnidaria, three Arthropoda, two Mollusca and twenty Chordata) and extending from the Western Mediterranean Sea to the Levantine Sea and theBlack Sea (Sea of Marmara). The new records were reported from 11 countries as follows: Algeria: occurrence of the Africanstriped grunt Parapristipoma octolineatum; Spain: new records of eight uncommon fish species (Gadella maraldi, Hypleurochilusbananensis, Lobotes surinamensis, Parapristipoma octolineatum, Selene dorsalis, Sphoeroides marmoratus, Tetragonuruscuvieri, and Trachyrincus scabrus) from the Spanish Mediterranean; Italy: new record of the football octopus Ocythoe tuberculatafrom the Southern Tyrrhenian Sea; a rare sighting of a juvenile phase of a moray eel of the genus Gymnothorax, tentativelyidentified as Gymnothorax cf. unicolor in the Ligurian Sea; first record of adult Facciola’s sorcerer Facciolella oxyrhynchus inthe Adriatic Sea; occurrence of the tope shark Galeorhinus galeus in the Northern Adriatic Sea; Libya: first confirmed recordof the pen shell Pinna rudis; first documented record of the palaemonid shrimp Brachycarpus biunguiculatus; first record of thefish Sudis hyalina; Malta: new records of Grant’s rockling, Gaidropsarus granti; multiple concomitant reports of the rare hydromedusanspecies Aequorea forskalea; Croatia: a record of the skipjack tuna Katsuwonus pelamis in the Southern Adriatic Sea;Albania: new record of the bigeye thresher shark Alopias superciliosus; Greece: confirmation of the rare brown alga Sargassumflavifolium occurrence in the Eastern Mediterranean Sea; first record of the scaleless dragonfish Bathophilus nigerrimus; Turkey:first occurrence of the calanoid copepod Pteriacartia josephinae in the Aegean Sea; first documented record of the Cremona’s seaslug Placida cremoniana for the easternmost Mediterranean Sea; new record of the yellow-headed goby Gobius xanthocephalusin the Sea of Marmara; Cyprus: first record of the Liechtenstein’s goby Corcyrogobius liechtensteini; an individual of the Yellowfintuna Thunnus albacares captured with handline by an artisanal fisher; Lebanon: an individual of the Black marlin Istiompaxindica captured in a gill ne

New Mediterranean biodiversity records (March 2016)

In this Collective Article on “New Mediterranean Biodiversity Records”, we present additional records of species found in the Mediterranean Sea. These records refer to eight different countries mainly throughout the northern part of the basin, and include 28 species, belonging to five Phyla. The findings per country include the following species: Spain: Callinectes sapidus and Chelidonura fulvipunctata; Monaco: Aplysia dactylomela; Italy: Charybdis (Charybdis) feriata, Carcharodon carcharias, Seriola fasciata, and Siganus rivulatus; Malta: Pomacanthus asfur; Croatia: Lagocephalus sceleratus and Pomadasys incisus; Montenegro: Lagocephalus sceleratus; Greece: Amathia (Zoobotryon) verticillata, Atys macandrewii, Cerithium scabridum, Chama pacifica, Dendostrea cf. folium, Ergalatax junionae, Septifer cumingii, Syphonota geographica, Syrnola fasciata, Oxyu- richthys petersi, Scarus ghobban, Scorpaena maderensis, Solea aegyptiaca and Upeneus pori; Turkey: Lobotes surinamensis, Ruvettus pretiosus and Ophiocten abyssicolum. In the current article, the presence of Taractes rubescens (Jordan & Evermann, 1887) is recorded for the first time in the Mediterranean from Italy. The great contribution of citizen scientists in monitoring biodiversity records is reflected herein, as 10% of the authors are citizen scientists, and contributed 37.5% of the new findings.peer-reviewe

Ecological commonalities among pelagic fishes: comparison of freshwater ciscoes and marine herring and sprat

Systematic comparisons of the ecology between functionally similar fish species from freshwater and marine aquatic systems are surprisingly rare. Here, we discuss commonalities and differences in evolutionary history, population genetics, reproduction and life history, ecological interactions, behavioural ecology and physiological ecology of temperate and Arctic freshwater coregonids (vendace and ciscoes, Coregonus spp.) and marine clupeids (herring, Clupea harengus, and sprat, Sprattus sprattus). We further elucidate potential effects of climate warming on these groups of fish based on the ecological features of coregonids and clupeids documented in the previous parts of the review. These freshwater and marine fishes share a surprisingly high number of similarities. Both groups are relatively short-lived, pelagic planktivorous fishes. The genetic differentiation of local populations is weak and seems to be in part correlated to an astonishing variability of spawning times. The discrete thermal window of each species influences habitat use, diel vertical migrations and supposedly also life history variations. Complex life cycles and preference for cool or cold water make all species vulnerable to the effects of global warming. It is suggested that future research on the functional interdependence between spawning time, life history characteristics, thermal windows and genetic differentiation may profit from a systematic comparison of the patterns found in either coregonids or clupeids

Relationships among predatory fish, sea urchins and barrens in Mediterranean rocky reefs across a latitudinal gradient

Previous studies conducted on a local scale emphasised the potential of trophic cascades in Mediterranean rocky reefs (involving predatory fish, sea urchins and macroalgae) in affecting the transition between benthic communities dominated by erected macroalgae and barrens (i.e., bare rock with partial cover of encrusting algae). Distribution patterns of fish predators of sea urchins (Diplodus sargus sargus, Diplodus vulgaris, Coris julis and Thalassoma pavo), sea urchins (Paracentrotus lividus and Arbacia lixula) and barrens, and fish predation rates upon sea urchins, were assessed in shallow (3-6 m depth) sublittoral rocky reefs in the northern, central and southern sectors of the eastern Adriatic Sea, i.e., on a large spatial scale of hundreds of kilometres. No dramatic differences were observed in predatory fish density across latitude, except for a lower density of small D. sargus sargus in the northern Adriatic and an increasing density of T pavo from north to south. P. lividus did not show any significant difference across latitude, whereas A. lixula was more abundant in the southern than in the central Adriatic. Barrens were more extended in the southern than in the central and northern sectors, and were related with sea urchin density. Fish predation upon adult sea urchins did not change on a large scale, whereas it was slightly higher in the southern sector for juveniles when predation rates of both urchins were pooled. Results show that: (1) assemblages of predatory fish and sea urchins, and barren extent change across latitude in the eastern Adriatic Sea, (2) the weak relations between predatory fish density and predation rates on urchins reveal that factors other than top-down control can be important over large scale (with the caveat that the study was conducted in fished areas) and (3) patterns of interaction among strongly interacting taxa could change on large spatial scales and the number of species involved