Abstract Cover illustration . Cycliophorans have been discovered in the late 1960s. They constitute a group of microscopic commensals that live attached to the mouth parts of clawed lobsters. So far females have been known only from immature individuals. In this issue of the Journal of Morphology (pp. 850–869) Neves and coauthors describe the morphology and ultrastructure of the free and fully mature female of Cycliophora. The cover image shows a free‐swimming female of the undescribed Symbion sp. from Homarus gammarus .
In birds, parasites cause detrimental effects to the individual host, including reduced survival and reproductive output. The level of parasitic infection can vary with a range of factors, including migratory status, body size, sex, and age of hosts, or season. Understanding this baseline variation is important in order to identify the effects of external changes such as climate change on the parasitic load and potential impacts to individuals and populations. In this study, we compared the infection level (prevalence, intensity, and abundance) of gastrointestinal parasites in a total of 457 common eiders (Somateria mollissima) from four different sampling locations (Belcher Islands, Cape Dorset, West Greenland and Newfoundland), and explored the effects of migration, sex and age on levels of parasitism. Across all samples, eiders were infected with one nematode genus, two acanthocephalan genera, three genera of cestodes, and three trematode genera. Migratory phase and status alone did not explain the observed variation in infection levels; the expectation that post-migratory eiders would be more parasitized than pre-migratory eiders, due to the energetic cost of migration, did not fit our results. No effect of age was detected, whereas effects of sex and body size were only detected for certain parasitic taxa and was inconsistent with location. Since gastrointestinal helminths are trophically-transmitted, future studies of the regional and temporal variation in the diet of eiders and the associated variation and infestation level of intermediate hosts might further explain the observed variation of the parasitic load in eiders in different regions.
Aim To analyse the phylogeographical history of intertidal tardigrades in the North Atlantic in order to improve our understanding of geographical differentiation in microscopic organisms, and to understand the potential importance of the Mid-Atlantic Islands as stepping stones between the American and European coasts of the Atlantic Ocean. Location Twenty-four localities from the Mid-Atlantic Islands (Greenland, Iceland and the Faroe Islands) and both sides of the North Atlantic Ocean. Methods A mitochondrial marker (cytochrome c oxidase subunit I) was sequenced from individual tardigrades belonging to the genus Echiniscoides. The existence of cryptic species was detected using generalized mixed Yule coalescence analysis; lineage ages were estimated with relaxed clock methods; and the degree of geographical differentiation was analysed with samova analyses, haplotype networks and Mantel tests. Results Echiniscoides hoepneri, previously known only from Greenland, was recovered throughout the Mid-Atlantic Islands. The Faroe Islands population was isolated from Greenland and Iceland, but overall genetic variation was low. The morphospecies Echiniscoides sigismundi had high genetic variation and consisted of at least two cryptic species. A northern and a southern species were both recovered on both sides of the Atlantic, but only the northern species was found on the Mid-Atlantic Islands. The northern species showed signs of long-term isolation between the Western and Eastern Atlantic, despite the potential of the Mid-Atlantic islands to act as stepping-stones. There was no sign of long-term isolation in the southern species. The Mid-Atlantic individuals of the northern species were of Eastern Atlantic origin, but Greenland and Iceland showed signs of long-term isolation. The genetic pattern found in the southern species is not clearly geographical, and can probably be best explained by secondary contact between former isolated populations. Main conclusions North Atlantic intertidal tardigrades from the genus Echiniscoides showed strong geographical differentiation, and the Mid-Atlantic Islands seemed unimportant as stepping stones across the Atlantic. The geographical variation of the northern species of E. sigismundi suggests post-glacial recolonization from several refugia.
As hunters and gatherers, humans have always exploited a wide variety of natural resources. Hunting, in particular, focuses upon individual species. The relationships between human and game are most often seen as isolated entities, for example, human–bison, human–whale, human–seabird or human–mammoth. However, hunting interactions are embedded in large and complex ecological networks. Seabirds such as the common eider (Somateria mollissima) have been and are still being hunted by both indigenous people of the Arctic and Europeans. Due to anthropogenic pressures, including hunting, several common eider populations have declined during the 20th century, even as much as up to 10-fold. Here, we review the ecological role of the common eider in Arctic networks and the diversity of human–eider interactions, underlining its importance for both humans and nonhumans. We place these interactions in a wider ecological context and discuss how human activities affecting eiders propagate through the Arctic ecological network and can cause far-reaching ecological effects.
Abstract Aim To analyse the importance of climatic and geographical isolation in determining the patterns of speciation and distribution of species within the tardigrade genus Echiniscoides . Location Marine intertidal zone, globally. Methods DNA was extracted from 465 individual tardigrades from 48 localities world‐wide. The tardigrades were divided into clusters using several distance‐based criteria. The phylogeny of these clusters was estimated with Bayesian analyses. The relationships between genetic distance and substrate, climate, and geographical distance were tested with a new improved Mantel test which incorporates phylogenetic uncertainties by analysing the raw tree data instead of the averaged tree. Results Approximately 40 clusters, each probably corresponding to species, were recovered from the genetic analysis; the number of clusters fluctuated depending on the criterion used for cluster delimitation. Each cluster had a limited temperature range and all clusters were confined to single oceans under all realistic criteria for cluster delimitation. Apart from a tropical cluster, each cluster occurred only in one hemisphere. Occurrence on different substrata was not correlated with genetic distance between clusters. Both geographical distance and climate were correlated with genetic distance; however, the correlation between geographical and genetic distance disappeared when the non‐independence of climatic and geographical distance were controlled for. Main conclusions The distribution of individual species of Echiniscoides is limited by climate and geographical distance. Distance does not appear to be a major factor influencing phylogeny in this genus, but ecological speciation along a temperature gradient appears to be important.
Sponges (phylum Porifera) are metazoans which lack muscles and nerve cells, yet perform coordinated behaviours such as whole-body contractions. Previous studies indicate diurnal variability in both the number of contractions and the expression of circadian clock genes. Here, we show that diurnal patterns are present in the contraction-expansion behaviour of the demosponge Tethya wilhelma, by using infrared videography and a simulated night/day cycle including sunrise and sunset mimics. In addition, we show that this behaviour is at least strongly influenced by ambient light intensity and therefore indicates light-sensing capabilities in this sponge species. This is supported by our finding that T. wilhelma consistently contracts at sunrise, and that this pattern disappears both when the sponge is kept in constant darkness and when it is in constant light.
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