Feeding of freshwater filter-feeders at very low food concentrations: Poor evidence for "threshold feeding" and "optimal foraging" in Daphnia longispina and Eudiaptomus gracilis

The feeding behaviour of two freshwater zooplankton species,the calanoid copepod Eudiaptomus gracilis and the cladoceranDaphnia longispina, at extremely low food concentrations hasbeen studied in order to test whether the animals react as predictedby the models of optimal foraging. Three different sized algae were offered in concentrations downto 1µg C/litre at 7°C during winter and 19°C duringsummer. Ingestion rates were measured by use of a flow-through¹⁴C-technique In contrast to the findings of several authors working withmarine copepods a threshold concentration where the animalsceased filtering could be detected only in one experiment byregression analysis (Daphnia, 19°C, food: Stichococcus).A depression of the filtering rate at low concentrations wasobserved only in Daphnia at 19°C with Stichococcus and Scenedesmusas food. It is supposed that in this case the reduction of thefiltering rate is not a direct response of the filtrator, butis caused by exhaustion due to the experimental conditions. As freshwater zooplankton is very rarely exposed to food abundancesas low as in the marine environment, there seems to be no selectionpressure favouring the evolution of an "optimal forager" behaviour. ⁽¹⁾Supported by Deutsche Forschungsgemeinschaft     

Predator–rodent–plant interactions along a coast–inland gradient in Fennoscandian tundra

Spatial variation in the strength of trophic cascades in arctic tundra has been related to flows of subsidies across ecosystem boundaries. Here, we ask whether the input of marine subsidies in tundra systems would cause spatial variation in the strength of rodent–plant interactions between coastal areas, where predators have access to marine‐derived resources, and non‐subsidized inland areas of northern Fennoscandia. We present a detailed evaluation of predator–rodent–vegetation interactions along a coast‐inland gradient, during the 2011 rodent outbreak and the two following decline years, by using direct assessments of rodent impacts and tracing of marine‐derived nutrients in the food web. Our results revealed that the main rodent predator during summer, the long‐tailed jaeger Stercorarius longicaudus, did not benefit from marine resources while breeding (relative dietary proportion in chicks’ diet = 0–3%). Contrary to this pattern, parasitic jaegers S. parasiticus, bred exclusively near the coast and preyed effectively on both marine resources (41% of chicks’ diet) and rodents (12%). Mammalian predators also showed a higher activity during winter near the coast. Despite overall higher predator numbers, no evidence was found for lower rodent population growth rates during the three monitoring summers and for weaker rodent grazing impacts in the coastal area. Instead, we documented pronounced damages caused by lemmings and voles on bryophytes and vascular plants, especially dwarf shrubs (e.g. Vaccinum myrtillus) all along the coast–inland gradient. Taken together, our results did not support the hypothesis that marine subsidies would trigger a trophic cascade in coastal tundra areas of northern Fennoscandia during a major rodent outbreak, probably due to a relatively low diversity of marine‐subsidized predators in the region. Comparative observational and experimental studies at large spatial scales in various arctic regions are absolutely necessary for a better understanding of factors causing regional variations in the functioning of arctic food webs.     

Zehnfußkrebse – Pioniere der Evolution

Decapod Crustaceans Decapod Crustaceans, which are by origin a marine group that still occurs mainly in the sea, invaded during their evolution also firm land and freshwater habitats. Stress factors associated with those non‐marine environments have successfully been countervailed by long‐lived benthic juvenile and adult life‐history stages, which were able to evolve structural and physiological adaptations. By contrast, the adaptability of the short‐lived planktonic larval stages has been much weaker, remaining physiologically fragile and mostly dependant on planktonic food sources. Terrestrial as well as limnic decapods have evolved various ”export strategies" based on extended migrations. These are performed by the adult females and/or the first larval stage, being aimed at an avoidance of stress conditions during the larval phase. In order to successfully complete the larval phase in freshwater, already the earliest developmental stages must express special structures and physiological functions aiding to the maintenance of osmotic homeostasis and to an independance from planktonic food sources.     

Time and environment explain the current richness distribution of non‐marine turtles worldwide

Ecological, historical, and evolutionary hypotheses are important to explain geographical diversity gradients in many clades, but few studies have combined them into a single analysis allowing a comparison of their relative importance. This study aimed to evaluate the relative importance of ecological, historical, and evolutionary hypotheses in explaining the current global distribution of non‐marine turtles, a group whose distribution patterns are still poorly explored. We used data from distribution range maps of 336 species of non‐marine turtles, environmental layers, and phylogeny to obtain richness estimates of these animals in 2° × 2° cells and predictors related to ecological, evolutionary and historical hypotheses driving richness patterns. Then we used a path analysis to evaluate direct and indirect effects of the predictors on turtle richness. Ancestral area reconstruction was also performed in order to evaluate the influence of time‐for‐speciation in the current diversity of the group. We found that environmental variables had the highest direct effects on non‐marine turtle richness, whereas diversification rates and area available in the last 55 million yr minimally influenced turtle distributions. We found evidence for the time‐for‐speciation effect, since regions colonized early were generally richer than recently colonized regions. In addition, regions with a high number of colonization events had a higher number of turtle species. Our results suggested that ecological processes may influence non‐marine turtle richness independent of diversification rates, but they are probably related to dispersal abilities. However, colonization time was also an important component that must be taken into account. Finally, our study provided additional support for the importance of ecological (climate and productivity) and historical (time‐for‐speciation and dispersal) processes in shaping current biodiversity patterns.     

Movement patterns,home range size and habitat utilization of the bluespine unicornfish, <Emphasis Type="BoldItalic">Naso unicornis</Emphasis> (Acanthuridae) in a Hawaiian marine reserve

Synopsis We quantified bluespine unicornfish, Naso unicornis, movement patterns, home range size and habitat preferences in a small Hawaiian marine reserve. Bluespine unicornfish were site-attached to home ranges situated within the reserve boundaries and their movements were aligned with topographic features. Two different diel movement patterns (‘commuting’ and ‘foraying’) were observed. Commuters made crepuscular migrations of several hundred meters between daytime foraging areas and nighttime refuge holes. Foraying fish did not partake in crepuscular migrations and utilized refuge holes both day and night. Two bluespine unicornfish were also nocturnally active. There was little direct evidence of dispersal from the reserve but differences in bluespine unicornfish abundance and size among reef habitat zones were consistent with ontogenetic habitat shifts. The influence of habitat topography on bluespine unicornfish movements suggests that gross habitat characteristics could be used to predict reef fish movements. This could provide a simple method for setting marine reserve boundaries at sites for which empirical fish movement data are unavailable.     

Isotope evidence for the intensive use of marine foods by Late Upper Palaeolithic humans

We report here on direct evidence for the intensive consumption of marine foods by anatomically modern humans at approximately 12,000 years ago. We undertook isotopic analysis of bone collagen from three humans, dating to the late Palaeolithic, from the site of Kendrick's Cave in North Wales, UK. The isotopic measurements of their bone collagen indicated that ca. 30% of their dietary protein was from marine sources, which we interpret as likely being high trophic level marine organisms such as marine mammals. This indicates that towards the end of the Pleistocene modern humans were pursuing a hunting strategy that incorporated both marine and terrestrial mammals. This is the first occurrence of the intensive use of marine resources, specifically marine mammals, that becomes even more pronounced in the subsequent Mesolithic period.     

Ecological Bases of Hormone--Behavior Interactions: The "Emergency Life History Stage"

SYNOPSIS. Superimposed upon seasonal changes in morphology,physiology and behavior, are facultative responses to unpredictableevents known as labile (i.e., short-lived) perturbation factors(LPFs). These responses include behavioral and physiologicalchanges that enhance survival and collectively make up the "emergency"life history stage. There is considerable evidence that glucocorticosteroids,and other hormones in the hypothalamo—pituitary—adrenal(HPA) cascade, initiate and orchestrate the emergency life historystage within minutes to hours. This stage has a number of sub—stagesthat promote survival and avoid potential deleterious effectsof stress that may result from chronically elevated levels ofcirculating glucocorticosteroids over days and weeks. Thesesub—stages may include: redirection of behavior from anormal life history stage to increased foraging, irruptivetypemigration during the day, enhanced restfulness at night, andelevated gluconeogenesis. Once the perturbation passes, glucocorticosteroidsmay also promote recovery. Additional evidence from birds indicatesthat glucocorticosteroid responses to a standardized capture,handling and restraint protocol are modulated both on seasonaland individual levels. Field work reveals that these changesin responsiveness to LPFs have ecological bases, such as reproductivestate, body condition etc., that in turn indicate differenthormonal control mechanisms in the HPA cascade.     

Coalescent and biophysical models of stepping‐stone gene flow in neritid snails

Marine species in the Indo‐Pacific have ranges that can span thousands of kilometres, yet studies increasingly suggest that mean larval dispersal distances are less than historically assumed. Gene flow across these ranges must therefore rely to some extent on larval dispersal among intermediate ‘stepping‐stone’ populations in combination with long‐distance dispersal far beyond the mean of the dispersal kernel. We evaluate the strength of stepping‐stone dynamics by employing a spatially explicit biophysical model of larval dispersal in the tropical Pacific to construct hypotheses for dispersal pathways. We evaluate these hypotheses with coalescent models of gene flow among high‐island archipelagos in four neritid gastropod species. Two of the species live in the marine intertidal, while the other two are amphidromous, living in fresh water but retaining pelagic dispersal. Dispersal pathways predicted by the biophysical model were strongly favoured in 16 of 18 tests against alternate hypotheses. In regions where connectivity among high‐island archipelagos was predicted as direct, there was no difference in gene flow between marine and amphidromous species. In regions where connectivity was predicted through stepping‐stone atolls only accessible to marine species, gene flow estimates between high‐island archipelagos were significantly higher in marine species. Moreover, one of the marine species showed a significant pattern of isolation by distance consistent with stepping‐stone dynamics. While our results support stepping‐stone dynamics in Indo‐Pacific species, we also see evidence for nonequilibrium processes such as range expansions or rare long‐distance dispersal events. This study couples population genetic and biophysical models to help to shed light on larval dispersal pathways.     

源于微生物的海鞘天然产物

海洋动物是具有生物活性海洋天然产物的重要来源。海鞘中含有丰富的微生物类群,如细菌、放线菌、真菌和蓝细菌。越来越多的直接或间接证据表明,一些从海鞘中分离的天然产物并不是海鞘本身产生的,而是由其共生微生物产生的。本文对近些年来的海鞘天然产物的微生物来源的研究方法进行综述,包括可培养细菌的分离、不可培养细菌的粗提物检测、宏基因组学、全基因组测序等直接方法,以及化合物结构比对的间接方法。通过对海鞘-微生物共生体中天然产物生物合成来源的研究,不仅可以从根本上解决动物药源的问题,而且可为研究海鞘与微生物共生关系提供有力证据。     

Protracted oxygenation across the Cambrian–Ordovician transition: A key initiator of the Great Ordovician Biodiversification Event?

Fluctuations in marine oxygen concentrations have been invoked as a primary driver for changes in biodiversity throughout Earth history. Expansions in reducing marine conditions are commonly invoked as key causal mechanisms for mass extinctions, while increases in marine oxygenation are becoming an increasingly common causal mechanism invoked for biodiversification events. Here we utilize a multiproxy approach to constrain local and global marine paleoredox conditions throughout the late Cambrian–Early Ordovician from two drill core successions in Baltoscandia. Local paleoredox proxies such as manganese concentrations and iron speciation reveal that both sites in the Baltic paleobasin had persistently anoxic and predominantly euxinic (anoxic and sulfidic) bottom water conditions throughout the study interval. Corresponding trace metal datasets indicate nuanced contraction and expansion of global anoxic and euxinic conditions along continental margins during the late Cambrian–Early Ordovician. Lastly, thallium isotope data from these locally reducing sections suggest a global expansion of oxygenated shelf and deeper marine environments from the late Cambrian into the Early Ordovician. This evidence for increasingly oxic marine environments coincides with increases in burrowing depth and tiering in marine animals, as well as diversification of body fossils throughout this ~8-million-year interval. The collective geochemical datasets provide some of the first direct paleoredox evidence for an increase in marine oxygen concentrations as a key mechanism for the Ordovician radiation of marine life.     

Ventilation and Its Effect on "Infinite Pool" Exchangers

SYNOPSIS. Unlike internal exchange surfaces, the skin contactsan "infinite pool" of air or water with which exchange of gases,water, ions, and other solutes may occur. Even though the "infinitepool" may be well mixed, an unstirred diffusion boundary layeris always present about the skin and may constitute a significantresistance to exchange. The thickness of the diffusion boundarylayer (as approximated by the fluid dynamic boundary layer)is related to the flow of the respiratory medium, viscosityand density of the medium, and the morphology of the exchangesurface. Oxygen microelectrode studies suggest that, in mostcircumstances, the diffusion boundary layer in water is at leastas thick as the blood-respiratory medium distance in amphibianskin. Accordingly, the movement of water about the skin {i.e.,skin ventilation) should have pronounced effects on cutaneousexchange, especially at low "free stream" velocities. Mountingphysiological evidence suggests that: (1) skin ventilation canaugment cutaneous gas exchange; and (2) some vertebrates activelyventilate their skins, especially in aquatic hypoxia. The ubiquityand significance of diffusion boundary layers are central toa general understanding of cutaneous exchange and all surface-mediatedexchange processes.     

Diversity of the Bacterial Communities Associated with the Azooxanthellate Deep Water Octocorals <Emphasis Type="Italic">Leptogorgia minimata</Emphasis>, <Emphasis Type="Italic">Iciligorgia schrammi</Emphasis>, and <Emphasis Type="Italic">Swiftia exertia</Emphasis>

This study examined the microbiota associated with the marine azooxanthellate octocorals Leptogorgia minimata, Swiftia exertia, and Iciligorgia schrammi collected from moderate depths (45 m). Traditional aerobic plate culture, fluorescence in situ hybridization (FISH), and molecular identification of the 16S rDNA region were used for this purpose. In general, cultures were found to be selective for Gammaproteobacteria, Alphaproteobacteria, and Firmicutes. Interestingly, FISH counts for Firmicutes in the whole coral (holobiont) were near the detection limit of this assay, representing less than 6% of the total detectable microbiota in all counts. Proteobacteria, especially Alpha- and Gammaproteobacteria, made up the majority of the total microbiota in the holobionts. In addition, the absence of zooxanthellae in these three corals was confirmed by the use of polymerase chain reaction (PCR) and dinoflagellate-specific primers, and spectrophotometric chlorophyll pigment measurements. No evidence of zooxanthellae could be found in any of the corals by either of these techniques. This is the first study examining the microbiota marine octocorals, which grow at moderate depth (40 to 100 m) in the absence of direct sunlight. Thomas B. Brück and Wolfram M. Brück have made equal contributions to this publication.     

Marine reserves indirectly affect fine‐scale habitat associations,but not overall densities,of small benthic fishes

Many large, fishery‐targeted predatory species have attained very high relative densities as a direct result of protection by no‐take marine reserves. Indirect effects, via interactions with targeted species, may also occur for species that are not themselves targeted by fishing. In some temperate rocky reef ecosystems, indirect effects have caused profound changes in community structure, notably the restoration of predator–urchin–macroalgae trophic cascades. Yet, indirect effects on small benthic reef fishes remain poorly understood, perhaps because of behavioral associations with complex, refuge‐providing habitats. Few, if any, studies have evaluated any potential effects of marine reserves on habitat associations in small benthic fishes. We surveyed densities of small benthic fishes, including some endemic species of triplefin (Tripterygiidae), along with fine‐scale habitat features in kelp forests on rocky reefs in and around multiple marine reserves in northern New Zealand over 3 years. Bayesian generalized linear mixed models were used to evaluate evidence for (1) main effects of marine reserve protection, (2) associations with habitat gradients, including complexity, and (3) differences in habitat associations inside versus outside reserves. No evidence of overall main effects of marine reserves on species richness or densities of fishes was found. Both richness and densities showed strong associations with gradients in habitat features, particularly habitat complexity. In addition, some species exhibited reserve‐by‐habitat interactions, having different associations with habitat gradients inside versus outside marine reserves. Two species (Ruanoho whero and Forsterygion flavonigrum) showed stronger positive associations with habitat complexity inside reserves. These results are consistent with the presence of a behavioral risk effect, whereby prey fishes are more strongly attracted to habitats that provide refuge from predation in areas where predators are more abundant. This work highlights the importance of habitat structure and the potential for fishing to affect behavioral interactions and the interspecific dynamic attributes of community structure beyond simple predator–prey consumption and archetypal trophic cascades.     

Dominance Acquisition During Mammalian Social Development: The "Inheritance" of Maternal Rank

We first review the suite of general problems mammals confrontduring their social development, and then focus on the specificproblem of how group-living mammals acquire their social rank.In particular, we examine maternal rank "inheritance" (MRI)in those mammals for which maternal rank is the primary determinantof female rank. This occurs in many primates and in spottedhyenas. Young primates and spotted hyenas usually attain theiradult status in two stages: they first attain ranks correlatedwith those of their mothers in peer interactions, and subsequentlychallenge and outrank older conspecifics subordinate to theirmothers. Observational learning may be necessary, but is notsufficient, for MRI. In some primates, but not hyenas, youngstersappear to learn their ranks from direct aggression against themby higher-ranking adults. Third-party support appears to promoteMRI in all species examined: the probability and style of maternalinterventions on behalf of infants often vary with rank, andboth kin and nonkin frequently form coalitions that may assistjuveniles during rank reversals.     

Biology of extinction risk in marine fishes

We review interactions between extrinsic threats to marine fishes and intrinsic aspects of their biology that determine how populations and species respond to those threats. Information is available on the status of less than 5% of the world's approximately 15500 marine fish species, most of which are of commercial importance. By 2001, based on data from 98 North Atlantic and northeast Pacific populations, marine fishes had declined by a median 65% in breeding biomass from known historic levels; 28 populations had declined by more than 80%. Most of these declines would be sufficient to warrant a status of threatened with extinction under international threat criteria. However, this interpretation is highly controversial, in part because of a perception that marine fishes have a suite of life history characteristics, including high fecundity and large geographical ranges, which might confer greater resilience than that shown by terrestrial vertebrates. We review 15 comparative analyses that have tested for these and other life history correlates of vulnerability in marine fishes. The empirical evidence suggests that large body size and late maturity are the best predictors of vulnerability to fishing, regardless of whether differences among taxa in fishing mortality are controlled; there is no evidence that high fecundity confers increased resilience. The evidence reviewed here is of direct relevance to the diverse criteria used at global and national levels by various bodies to assess threat status of fishes. Simple life history traits can be incorporated directly into quantitative assessment criteria, or used to modify the conclusions of quantitative assessments, or used as preliminary screening criteria for assessment of the approximately 95% of marine fish species whose status has yet to be evaluated either by conservationists or fisheries scientists.     

Differential sunlight sensitivity of picophytoplankton from surface Mediterranean Coastal Waters

We tested the sensitivity of coastal picophytoplankton exposed to natural sunlight in short-term experiments. Cell abundance and cell-specific chlorophyll fluorescence were significantly reduced in Prochlorococcus spp. but not in Synechococcus, whereas picoeukaryotes had an intermediate response. These results are the first direct evidence of a differential sensitivity to sunlight of these ubiquitous marine members of unicellular phytoplankton.     

Meta-analysis reveals an extreme “decline effect” in the impacts of ocean acidification on fish behavior

Ocean acidification—decreasing oceanic pH resulting from the uptake of excess atmospheric CO₂—has the potential to affect marine life in the future. Among the possible consequences, a series of studies on coral reef fish suggested that the direct effects of acidification on fish behavior may be extreme and have broad ecological ramifications. Recent studies documenting a lack of effect of experimental ocean acidification on fish behavior, however, call this prediction into question. Indeed, the phenomenon of decreasing effect sizes over time is not uncommon and is typically referred to as the “decline effect.” Here, we explore the consistency and robustness of scientific evidence over the past decade regarding direct effects of ocean acidification on fish behavior. Using a systematic review and meta-analysis of 91 studies empirically testing effects of ocean acidification on fish behavior, we provide quantitative evidence that the research to date on this topic is characterized by a decline effect, where large effects in initial studies have all but disappeared in subsequent studies over a decade. The decline effect in this field cannot be explained by 3 likely biological explanations, including increasing proportions of studies examining (1) cold-water species; (2) nonolfactory-associated behaviors; and (3) nonlarval life stages. Furthermore, the vast majority of studies with large effect sizes in this field tend to be characterized by low sample sizes, yet are published in high-impact journals and have a disproportionate influence on the field in terms of citations. We contend that ocean acidification has a negligible direct impact on fish behavior, and we advocate for improved approaches to minimize the potential for a decline effect in future avenues of research.     

Evidence of anthropogenic trauma in marine mammals stranded along the central California coast, 2003–2015

A total of 11,162 stranded marine mammals was admitted to a rehabilitation center on the central California coast between January 2003 and September 2015. Six hundred seventeen animals (6%) had evidence of anthropogenic trauma (AT). California sea lions comprised the majority (83%) of AT cases, particularly by entanglement in marine debris (n = 277) and gunshot injuries (n = 165). Guadalupe fur seals had the highest prevalence of entanglement in marine debris. Cetaceans were primarily affected by boat collisions (n = 19). The highest numbers of overall strandings were recorded in 2009 (n = 1,690) and 2015 (n = 1,666); 2009 also had the highest total number (n = 137) and prevalence (8%) of AT cases. Prevalence of fishing tackle cases increased compared to similar data from 1986 to 1998 while prevalence of gunshot cases decreased, and other causes remained static. Cases of fisheries interactions were further examined and characterized, and when direct fisheries interactions were separated from other causes of AT, fisheries interactions accounted for 50% (n = 310) of all AT cases during the study period. Direct fisheries interactions were the most common type of AT observed among stranded marine mammals in central California. Tracking AT trends is important to further understand possible causes and inform mitigation efforts.     

海洋共附生微生物天然产物生物合成基因研究进展

对海洋无脊椎动物天然产物的研究表明,很多种活性物质的真正生产者是与其共生或附生的未培养微生物.克隆这些未培养微生物中特定活性物质的生物合成基因,不仅为活性物质的来源提供遗传学证据,也使通过异源表达相关生物合成基因来大量获取目标化合物成为可能.本文综述了来源于海绵、海鞘、苔藓虫、深海管状蠕虫和深海沉积物中共附生微生物天然产物生物合成基因簇的研究进展.     

Cardiac telocytes are double positive for CD34/PDGFR‐α

Telocytes (TCs) are a distinct type of interstitial cells, which are featured with a small cellular body and long and thin elongations called telopodes (Tps). TCs have been widely identified in lots of tissues and organs including heart. Double staining for CD34/PDGFR‐β (Platelet‐derived growth factor receptor β) or CD34/Vimentin is considered to be critical for TC phenotyping. It has recently been proposed that CD34/PDGFR‐α (Platelet‐derived growth factor receptor α) is actually a specific marker for TCs including cardiac TCs although the direct evidence is still lacking. Here, we showed that cardiac TCs were double positive for CD34/PDGFR‐α in primary culture. CD34/PDGFR‐α positive cells (putative cardiac TCs) also existed in mice ventricle and human cardiac valves including mitral valve, tricuspid valve and aortic valve. Over 87% of cells in a TC‐enriched culture of rat cardiac interstitial cells were positive for PDGFR‐α, while CD34/PDGFR‐α double positive cells accounted for 30.25% of the whole cell population. We show that cardiac TCs are double positive for CD34/PDGFR‐α. Better understanding of the immunocytochemical phenotypes of cardiac TCs might help using cardiac TCs as a novel source in cardiac repair.