Tracking the marine migration routes of South Pacific silver eels

It is still a mystery how catadromous eels find their way through the seemingly featureless open ocean to their spawning areas. Three catadromous Pacific eels (2 Anguilla marmorata, 1 A. megastoma) from the Archipelago of Vanuatu were tagged with pop-up satellite archival transmitters, and their migration tracks towards their presumed spawning area approximately 870 km northeast of the point of release were reconstructed in order to evaluate their movements in relation to oceanographic conditions. We used the timing of diel vertical migrations to derive the eels’ positions. The 2 A. marmorata exhibited steep-angled turns resulting in a zig-zag migration path along the east−west axis, while the A. megastoma took a relatively straight course towards the presumed spawning area. They migrated with a speed over ground of 21−23 km d−1. In this region, the eastward flow of the South Equatorial Counter Current (SECC, ~5°−10°S) separates the westward flowing South Equatorial Current (SEC; ~0°−5°S and 10°−18°S) into 2 branches. During shallower nighttime migration depths around 150 m, eels crossed a variable flow field through the southern branch of the westward SEC with westward propagating mesoscale eddies and the eastward SECC, but stayed south of the stronger northern branch of the SEC, possibly increasing retention time of larvae within this area. The eels headed towards a tongue of high-salinity Subtropical Underwater (STUW). The eels did not move beyond a salinity front of 35.9−36.0 at a depth of 100−200 m, which may have provided cues for orientation towards the spawning area

Die schulgeschichtliche Entwicklung von Berufsorientierung und Politischer Bildung in Österreich im Vergleich

Berufsorientierung und Politische Bildung. Zwei Begriffe, die in letzter Zeit sehr stark in Mode gekommen sind und die in der Schule stark verankert sein sollten, denkt man. Doch sind sie das wirklich? In dieser Diplomarbeit werden die Begriffe Politische Bildung und Berufsorientierung zuerst theoretisch beleuchtet, bevor sich ihrer schulgeschichtlichen Entwicklung in den Lehrplänen in Österreich gewidmet wird. Es werden Unterschiede in den verschiedenen Schulstufen aufgezeigt sowie wird auf den Unterschied zwischen Verbindliche Übung und Unterrichtsprinzip eingegangen. Es werden außerdem Governance- Überlegungen zu den beiden thematischen Feldern angestellt. Abschließend wird ein Vergleich der Stellung von Berufsorientierung und Politischer Bildung in österreichischen Schulen gezogen, sowie Schwächen in der Umsetzung in der Praxis aufgezeigt und mögliche Verbesserungsvorschläge genannt

Short- and long-term advantages of an alternative ontogenetic pathway

peer reviewedWe documented hypotheses on the evolution of developmental heterochronies by estimating short- and long-term advantages of alternative morphs. In this respect, we compared food energy intakes and body condition between paedomorphic and metamorphic Alpine newts (Triturus alpestris, Caudata, Amphibia) in four populations. Because we found a strong correlation between fat reserves and body condition, we used this last parameter as an indicator of long-term gains. In all studied sites, paedomorphic females showed higher body condition than metamorphic ones. Paedomorphic males were also at advantage in two populations. Paedomorphs exhibited higher energy intakes than metamorphs in two populations and similar gains in two others. Our results support unifying theories that predict the occurrence of facultative paedomorphosis in varied habitats as paedomorphs exhibited better energy balance than metamorphs. This work shows the need for considering integrative parameters such as body condition in the comparative study of performances when studying developmental heterochronies. (C) 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 77, 105-112

Doprinos poznavanju faune tulara (Insecta: Trichoptera) jezera Leqinat i obližnjih potoka na području Bjeshkët e Nemuna (Kosovo)

Adult caddisflies were collected with entomological nets and ultraviolet light traps during August and September 2018 in Leqinat Lake, Drelaj Lake and five adjacent streams in Bjeshkët e Nemuna in Kosovo. Within the current study we found three first records for the caddisfly fauna of Kosovo: Limnephilus flavospinosus, Limnephilus flavicornis and Oligotricha striata. The genus Oligotricha is reported for the first time from Kosovo. We also found few rare species which have been reported only from few localities in the Balkan Peninsula such as: Plectrocnemia mojkovacensis, Rhyacophila balcanica and Drusus tenellus.Odrasli tulari prikupljani su pomoću entomološke mrežice i UV svjetlosnih zamki tijekom kolovoza i rujna 2018. na jezerima Leqinat i Drelaj te pet obližnjih potoka, na području Bjeshkët e Nemuna na Kosovu. Tijekom istraživanja zabilježili smo tri prva nalaza za faunu tulara Kosova: Limnephilus flavospinosus, Limnephilus flavicornis i Oligotricha striata. Po prvi puta za Kosovo je zabilježen rod Oligotricha. Također smo našli neke rijetke vrste zabilježenih na samo nekoliko lokaliteta na Balkanu, npr.: Plectrocnemia mojkovacensis, Rhyacophila balcanica i Drusus tenellus

Hydrographic features of anguillid spawning areas: potential signposts for migrating eels

Catadromous anguillid eels (genus Anguilla) migrate from their freshwater or estuarine habitats to marine spawning areas. Evidence from satellite tagging studies indicates that tropical and temperate eel species exhibit pronounced diel vertical migrations, from between 150-300 m nighttime depths to 600-800 m during the day. Collections of eggs and larvae of Japanese eels A. japonica suggest they may spawn at these upper nighttime migration depths. How anguillid eels navigate through the ocean and find their spawning areas remains unknown; thus, this study describes the salinity, temperature and geostrophic currents between 0 and 800 m depths within 2 confirmed and 3 hypothetical anguillid spawning areas during likely spawning seasons. Within the 4 ocean gyres in which these spawning areas are located, many eels would encounter subducted 'Subtropical Underwater' water masses during their nighttime ascents that could provide odor plumes as signposts. Four of the spawning areas are located near the western margins of where subducted water masses form cores of elevated salinities (similar to 35.0 to 36.8) around 150 m depths, and one is located near the center of subduction. Low salinity surface waters and fronts are present in some of the areas above the high-salinity cores. Spawning may occur at temperatures between 16 and 24 degrees C where the thermocline locally deepens. At spawning depths, weak westward currents (similar to 0 to 0.1 m s(-1)) prevail, and eastward surface countercurrents are present. Anguillid eels possess acute sensory capabilities to detect these hydrographic features as potential signposts, guiding them to their spawning areas

Genetic and migratory evidence for sympatric spawning of tropical pacific eels from Vanuatu

The spawning areas of tropical anguillid eels in the South Pacific are poorly known, and more information about their life histories is needed to facilitate conservation. We genetically characterized 83 out of 84 eels caught on Gaua Island (Vanuatu) and tagged 8 eels with pop-up satellite transmitters. Based on morphological evidence, 32 eels were identified as Anguilla marmorata, 45 as A. megastoma and 7 as A. obscura. Thirteen of these eels possessed a mitochondrial DNA sequence (control region, 527 bp) or nuclear haplotype (GTH2b, 268 bp) conflicting with their species designation. These individuals also had multi-locus genotypes (6 microsatellite loci) intermediate between the species, and 9 of these eels further possessed heterozygote genotypes at species-diagnostic nuclear single nucleotide polymorphisms (SNPs). We classified these individuals as possibly admixed between A. marmorata and A. megastoma. One A. marmorata and one A. megastoma migrated 634 and 874 km, respectively, towards the border between the South Equatorial Current and the South Equatorial Counter Current. Both species descended from around 200 m depth at night to 750 m during the day. Lunar cycle affected the upper limit of migration depths of both species. The tags remained attached for 3 and 5 mo and surfaced <300 km from the pop-up location of a previously tagged A. marmorata. A salinity maximum at the pop-up locations corresponding to the upper nighttime eel migration depths may serve as a seamark of the spawning area. The similar pop-up locations of both species and the evidence for admixture suggest that these tropical eels share a sympatric spawning area

High genetic diversity and lack of pronounced population structure in five species of sympatric Pacific eels

Understanding the population structure of tropical anguillids residing in the Pacific is vital for their conservation management. Here, the population genetic structure of five sympatric freshwater eels (Anguilla marmorata Quoy &amp; Gaimard, A. megastoma Kaup, A. obscura Steindachner, A. reinhardtii Günther and A. australis Richardson) across 11 western South Pacific (WSP) islands was investigated based on partial nucleotide sequences of the mtDNA control region and the nuclear GTH2b genes of 288 newly collected samples jointly with existing sequences. WSP anguillids are characterised by overall high levels of genetic diversity. Both mtDNA and nuclear sequences provided no evidence for distinct geographic clines or barriers in any of the species across the WSP. The occurrence of admixed individuals between A. marmorata and A. megastoma was confirmed, and a new possible occurrence of a further species was revealed (A. interioris Whitley on Bougainville Island). All species showed evidence for demographic population growth in the Pleistocene, and a subsequent population reduction for A. megastoma. Common spawning grounds and mixing of larvae by ocean currents could promote the lack of pronounced isolation by distance, a finding that has significant implications for the future management of anguillids in the area

Stable species boundaries despite ten million years of hybridisation in tropical eels

Genomic evidence is increasingly underpinning that hybridization between taxa is commonplace, challenging our views on the mechanisms that maintain their boundaries. Here, we focus on seven catadromous eel species (genus Anguilla) and use genome-wide sequence data from more than 450 individuals sampled across the tropical Indo-Pacific, morphological information, and three newly assembled draft genomes to compare contemporary patterns of hybridization with signatures of past introgression across a time-calibrated phylogeny. We show that the seven species have remained distinct for up to 10 million years and find that the current frequencies of hybridization across species pairs contrast with genomic signatures of past introgression. Based on near-complete asymmetry in the directionality of hybridization and decreasing frequencies of later-generation hybrids, we suggest cytonuclear incompatibilities, hybrid breakdown, and purifying selection as mechanisms that can support species cohesion even when hybridization has been pervasive throughout the evolutionary history of clades