Scales characterising a high density thin layer of Dinophysis acuta Ehrenberg and its transport within a coastal jet

An investigation into the distribution of Dinophysis spp. in coastal waters off the south coast of Ireland was carried out in July 2007. Dinophysis acuta was present as a sub surface layer containing up to 55,000 cells L⁻¹. The population had a high percentage of viable cells (mean: 89%; median: 94%; n = 24) with a high specific division rate (∼0.55 d⁻¹). The layer, of approximately 5 m thickness, did not coincide with the fluorescence maximum and was present as a patch of horizontal dimension less than 10 km × 7 km. Both conventional and towed undulating CTD used in conjunction with high vertical resolution sampling methods showed the patch of Dinophysis to move with a similar speed and direction as the coastal flow, which ran parallel to the coast in the form of a coastal jet with speed of the order of 6.5–7 km day⁻¹. The implications of the alongshore transport of populations of harmful species in coastal jets for monitoring programmes and predictive models are discussed.     

Climate variability and Dinophysis acuta blooms in an upwelling system

Dinophysis acuta is a frequent seasonal lipophilic toxin producer in European Atlantic coastal waters associated with thermal stratification. In the Galician Rías, populations of D. acuta with their epicentre located off Aveiro (northern Portugal), typically co-occur with and follow those of Dinophysis acuminata during the upwelling transition (early autumn) as a result of longshore transport. During hotter than average summers, D. acuta blooms also occur in August in the Rías, when they replace D. acuminata. Here we examined a 30-year (1985–2014) time series of D. acuta from samples collected by the same method in the Galician Rías. Our main objective was to identify patterns of distribution and their relation with climate variability, and to explain the exceptional summer blooms of D. acuta in 1989–1990. A dome-shaped relationship was found between summer upwelling intensity and D. acuta blooms; cell maxima were associated with conditions where the balance between upwelling intensity and heating, leading to deepened thermoclines, combined with tidal phase (3 days after neap tides) created windows of opportunity for this species. The application of a generalized additive model based on biological (D. acuta inoculum) and environmental predictors (Cumulative June–August upwelling CUI_JJA, average June–August SST_JJA and tidal range) explained more than 70% of the deviance for the exceptional summer blooms of D. acuta, through a combination of moderate (35,000–50,000 m³ s⁻¹ km⁻¹) summer upwelling (CUI_JJA), thermal stratification (SST_JJA > 17 °C) and moderate tidal range (∼2.5 m), provided D. acuta cells (inoculum) were present in July. There was no evidence of increasing trends in D. acuta bloom frequency/intensity nor a clear relationship with NAO or other long-term climatic cycles. Instead, the exceptional summer blooms of 1989–1990 appeared linked to extreme hydroclimatic anomalies (high positive anomalies in SST and NAO index), which affected most of the European Atlantic coast.     

Relationships between body size and some life history parameters

Summary Patterns in life history phenomena may be demonstrated by examining wide ranges of body weight. Positive relationships exist between adult body size and the clutch size of poikilotherms, litter weight, neonate weight life span, maturation time and, for homeotherms at least, brood or gestation time. The complex of these factors reduces r _max in larger animals or, in more physiological terms, r _max is set by individual growth rate. Comparison of neonatal production with ingestion and assimilation suggests that larger mammals put proportionately less effort into reproduction. Declining parental investment and longer development times would result if neonatal weight is scaled allometrically to adult weight and neonatal growth rate to neonatal weight. Body size relations represent general ecological theries and therefore hold considerable promise in the development of predictive ecology.     

psbA based molecular analysis of cross-feeding experiments suggests that Dinophysis acuta does not harbour permanent plastids

Toxic marine dinoflagellate species of the genus Dinophysis Ehrenberg are obligate mixotrophs that require feeding on the ciliate Mesodinium rubrum and light to achieve growth. It is now well known that they harbour plastids of cryptophyte origin, particularly of the genus Teleaulax, Plagioselmis or Geminigera group (TPG clade). Nevertheless, whether these plastids are permanent, or periodically acquired from M. rubrum prey, need additional studies in different phototrophic Dinophysis species. The origin of plastids from Dinophysis acuta Ehrenberg, one of the main agents of diarrhetic shellfish poisoning (DSP) outbreaks in Western Europe, was investigated here. Cross feeding-starvation experiments were carried out with cultures of D. acuta using M. rubrum as prey, the latter fed with two cryptophyte species, Teleaulax amphioxeia Hill and Teleaulax gracilis, belonging to the TPG clade in addition to Falcomonas sp. and Hemiselmis sp. The fate of cryptophyte plastids transferred to D. acuta through its ciliate prey was investigated using the plastid psbA gene as a tracer.     

Mixed interactions among life history stages of two harvested related species

Climate change and harvesting can affect the ecosystems'' functioning by altering the population dynamics and interactions among species. Knowing how species interact is essential for better understanding potentially unintended consequences of harvest on multiple species in ecosystems. I analyzed how stage‐specific interactions between two harvested competitors, the haddock (Melanogrammus aeglefinus) and Atlantic cod (Gadus morhua), living in the Barents Sea affect the outcome of changes in the harvest of the two species. Using state‐space models that account for observation errors and stochasticity in the population dynamics, I run different harvesting scenarios and track population‐level responses of both species. The increasing temperature elevated the number of larvae of haddock but did not significantly influence the older age‐classes. The nature of the interactions between both species shifted from predator‐prey to competition around age‐2 to ‐3. Increased cod fishing mortality, which led to decreasing abundance of cod, was associated with an increasing overall abundance of haddock, which suggests compensatory dynamics of both species. From a stage‐specific approach, I show that a change in the abundance in one species may propagate to other species, threatening the exploited species'' recovery. Thus, this study demonstrates that considering interactions among life history stages of harvested species is essential to enhance species'' co‐existence in harvested ecosystems. The approach developed in this study steps forward the analyses of effects of harvest and climate in multi‐species systems by considering the comprehension of complex ecological processes to facilitate the sustainable use of natural resources.     

The early life history stages of riverine fish: ecophysiological and environmental bottlenecks

Fish are good indicators of the environmental health of rivers and their catchments as well as important conservation targets. Bioindication has to be based on an understanding of the requirement of characteristic species with regard to: (a). The match/mismatch between reproductive strategies and environmental conditions. (b). The niche dimensions of critical stages vis-a-vis the key conditions. (c). The availability of microhabitats along the ontogenetic niche profiles, i.e. the connectivity from spawning substrates to early life history microhabitats. The main conditions for the embryonic period are temperature and oxygen supply which are responsible for embryonic mortality, the duration of the period, and size and condition of newly-hatched larvae. For the exogenously feeding larvae the functional of food acquisition, growth and bioenergetics to temperature, food availability and current velocity is decisive. Studies concentrated on Chondrostoma nasus, a target species for monitoring and conservation in large European river systems. Results obtained in experimental studies are compared with those from field studies in order to evaluate the match/mismatch between performances and microhabitat choice and population dynamics in the field. Discrepancies between requirements and field conditions in regulated rivers underline the significance of inshore zones as microhabitats (expressed in the 'Inshore Retention Concept') and the requirement for ecophysiological studies on target species for river restoration and conservation.     

Immunocytochemical localization of ecdysteroids in the life history stages of Schistosoma mansoni

Sporocysts, cercariae and adults of S. mansoni exhibit focal immunoreactivity against anti-ecdysone serum in an indirect immunofluorescence assay. In adult males immunoreactivity is limited to cell bodies and linear connections in the parenchyma surrounding the intestinal caeca. In both unisexual and paired mature females part of the lining of the ootype is reactive, especially near the entrance of the vitelline duct; this demonstrates that females can make ecdysteroids without mal contact. Adult worms cultured completely in vitro show a similar pattern of reactivity. Immunoreactivity is strong in cercariae, but is essentially absent in miracidia.     

Comprehensive investigation of ectoparasite community and abundance across life history stages of avian host

Fitness consequences of ectoparasitism are expressed over the lifetime of their hosts in relation to variation in composition and abundance of the entire ectoparasite community and across all host life history stages. However, most empirical studies have focused on parasite species-specific effects and only during some life history stages. We conducted a systematic, year-long survey of an ectoparasite community in a wild population of house finches Carpodacus mexicanus Müller in south-western Arizona, with a specific focus on ecological and behavioral correlates of ectoparasite prevalence and abundance. We investigated five ectoparasite species: two feather mite genera – both novel for house finches – Strelkoviacarus (Analgidae) and Dermoglyphus (Dermoglyphidae), the nest mite Pellonyssus reedi (Macronyssidae), and the lice Menacanthus alaudae (Menoponidae) and Ricinus microcephalus (Ricinidae). Mite P. reedi and louse Menacanthus alaudae abundance peaked during host breeding season, especially in older birds, whereas feather mite abundance peaked during molt. Overall, breeding birds had more P. reedi than non-breeders, molting males had greater abundance of feather mites than molting females and non-molting males, and young males had more feather mites than older males. We discuss these results in relation to natural history of ectoparasites under study and suggest that ectoparasites might synchronize their life cycles to those of their hosts. Pronounced differences in relative abundance of ectoparasite species among host's life history stages have important implications for evolution of parasite-specific host defenses.     

The evolution of migration and some life history parameters in marine fishes

Synopsis Migration is a common phenomenon in marine fishes but the consequences with respect to life history variation have been little explored. Migration both influences the evolution of other traits and is contigent upon the evolution of other behavioural and demographic characters. The interaction between such factors is illustrated by considering the relationship between the cost of migration in relation to fecundity and the advantages and disadvantages of schooling, a phenomenon hypothesized to favour the evolution of migration. These analyses predict that migratory species will be relatively large, mature late and at a relatively large size and grow relatively fast. Data from north temperate marine fish support these predictions.     

The use of a mucus trap by Dinophysis acuta for the capture of Mesodinium rubrum prey under culture conditions

A capture mechanism observed in a culture of the dinoflagellate Dinophysis acuta when preying on the ciliate Mesodinium rubrum (also sometimes referred to as Myrionecta rubra) is described. The dinoflagellate released cohesive clumps of mucilage into the culture media. When M. rubrum cells came into contact with this mucilage, they were immediately immobilized, but remained alive for a short period of time. Observations of D. acuta cells ‘visiting and probing’ trapped M. rubrum cells were made and at a critical point D. acuta cells removed individual M. rubrum cells from the mucus to swim away with them. The removal of M. rubrum from the mucus coincided with the cells losing all their cilia and becoming swollen, presumably signifying the death of the cell. These changes may enable the D. acuta peduncle to penetrate the ciliate cell cortex. It is hypothesized that toxins produced by D. acuta play a role in the immobilization process within the mucilage trap.     

Fine-scale genetic structure of life history stages in the food-deceptive orchid Orchis purpurea

In natural plant populations, fine-scale spatial genetic structure can result from limited gene flow, selection pressures or historical events, but the role of each factor is in general hard to discern. One way to investigate the origination of spatial genetic structure within a plant population consists of comparing spatial genetic structure among different life history stages. In this study, spatial genetic structure of the food-deceptive orchid Orchis purpurea was determined across life history stages in two populations that were regenerating after many years of population decline. Based on demographic analyses (2001-2004), we distinguished between recruits and adult plants. For both sites, there was no difference in the proportion of polymorphic loci and expected heterozygosity between life history stages. However, spatial autocorrelation analyses showed that spatial genetic structure increased in magnitude with life history stage. Weak or no spatial genetic structure was observed for recruits, whereas adult plants showed a pattern that is consistent with that found in other species with a predominantly outcrossing mating system. The observed differences between seedlings and adults are probably a consequence of changes in management of the two study sites and associated demographic changes in both populations. Our results illustrate that recurrent population crashes and recovery may strongly affect genetic diversity and fine-scale spatial genetic structure of plant populations.     

Seasonal variability of lipophilic toxins during a Dinophysis acuta bloom in Western Iberia: Differences between picked cells and plankton concentrates

This work describes and compares the seasonal variability of toxin profiles and content, estimated by LC–MS analyses, in picked cell of Dinophysis acuta Ehrenberg, in plankton concentrates rich in this species, and in extracellular lipophilic toxins collected by adsorbent resins during weekly sampling in a Galician ría (Western Iberia) from October 2005 to January 2006. Picked cells of D. acuta—which exhibited a fairly stable OA:DTX2 ratio, close to 3:2, but a variable okadaates:PTX2 ratio—showed a 9-fold variation in cell toxin quota, which was partly related to cellular volume, with maximum values (19 pg cell⁻¹) observed during the exponential decline of the population. Large differences in toxin profiles and content were observed between picked cells and plankton concentrates (up to 73 pg cell⁻¹ in the latter), that were most conspicuous after the bloom decline. The toxin profile of picked cells was more similar to that observed in the adsorbent resins than to the profiles of plankton concentrates. Their continued detection several weeks after the disappearance of Dinophysis spp. indicates that these toxins may take a long time to be degraded. It is concluded that analyses of picked-cells are essential to determine the contribution of each species of Dinophysis to a toxic outbreak. Estimates of cellular toxin content from plankton concentrates can lead to considerable overestimates after Dinophysis blooms decay due to extracellular toxins that persist in the water column, possibly bound to organic aggregates and detritus, and are retained (>0.22 μm) in the filters.     

Inducibility of life history changes by fish kairomone in various developmental stages of Daphnia

Life history changes in Daphnia galeata as a response to part-timeexposure to fish-exuded chemical (FEC) were studied in laboratoryexperiments. Exposure to FEC during one of the juvenile instarsdid not induce significant changes in life history parametersin D.galeata primiparae. Exposure in the first two instars injuvenile development induced earlier maturation, smaller primiparaeand the production of smaller eggs. Exposure in the third andfourth juvenile instars resulted in smaller primiparae withsmaller eggs. The adult daphnids, when exposed to FEC, reducedsomatic growth and produced more and smaller offspring. Resultsof other experiments presented here indicate that the perceptionof fish chemical signal by daphnids is not mediated by the ingestionof a chemically modified diet.     

Interaction of filipin with junctional membrane at different stages of the junction's life history

The relationship of filipin-sterol complexes to tight and gap junctions during their formation, maturation, internalization, and degradation was studied in separate cell lines. Filipin-sterol complexes tended to be excluded from mature junctions in tight junction forming COLO 316 cells and gap junction forming SW-13 cells. Once internalized, unlabeled junctional membrane appeared to fuse with heavily labeled vesicles, presumably lysosomes. Although the absence of filipin-sterol complexes from junctional membrane does not necessarily reflect the absolute sterol content of this membrane, the fact that filipin-sterol complexes are largely excluded from these areas indicates that this membrane is different from surrounding membrane. The absence of filipin-sterol complexes also permits the visualization of 'mixing' of this specialized unlabeled membrane domain with other filipin labeled membrane systems.     

Effects of predator-released chemicals on some life history parameters of Daphnia pulex

The effects of chemicals released by fish and Chaoborus larvae on some life history traits in Daphnia pulex were studied in an in situ enclosure experiment. The mean size of Daphnia individuals was smaller in the presence of fish-released cues. Also the minimal size of an egg bearing female in the presence of fish exudates was smaller than in the population exposed to the chemicals released by Chaoborus larvae as well as in the control population. Fish-released chemicals caused the increase in clutch size in Daphnia. There were no statistically significant differences between the studied life history parameters of the control and Chaoborus treatments. The results are discussed in reference to recent laboratory research.     

Experimental and observational studies of seasonal interactions between overlapping life history stages in a migratory bird

Prior to reproduction, migratory animals are at the juxtaposition of three life history stages in which they must finish the non-breeding stage, initiate and complete migration, and prepare for the onset of breeding. However, how these stages interact with one another is not fully understood. We provide evidence that, for migratory birds that begin breeding development prior to departure from non-breeding sites, the level of breeding preparation can drive migration phenology, a critical behavioral determinant of reproductive success. Specifically, male American redstart (Setophaga ruticilla) plasma androgen levels, which increase in males during the period leading into migration, were positively correlated with energetic condition. We empirically tested the hypothesis that elevated androgen simultaneously supports migratory and breeding preparation in a hormone manipulation field experiment. Males with testosterone implants showed advanced preparation for migration and breeding, and ultimately departed on migration earlier than controls. It is assumed that early departure leads to early arrival at breeding areas, which increases breeding success. Collectively, our observational and experimental results demonstrate how overlapping life history stages can interact to influence important components of an individual's fitness. This highlights the critical need for understanding population processes across the full life cycle of an organism to better understand the ecological and evolutionary origins of complex life history events.