Induction of Settlement and Metamorphosis of the Veliger Larvae of the Nudibranch,Onchidoris bilamellata

Summary

Onchidoris bilamellata veligers were reared in the laboratory on a combination of phytoñagellates and diatoms. They attained metamorphic competence after a period of 28 to 32 days at 11°C, or 60 to 80 days at a temperature averaging 7.5° C.

Experimental evidence suggests that settlement is stimulated by a diffusible chemical emanating from living barnacles, whereas metamorphosis is induced by a chemical or mechanochemical cue, which is also associated with barnacles. Settlement and metamorphosis are considered to be separable events in O. bilamellata. The settlement response is reversible and can be repeated; it involves a characteristic behavioral repertoire including descent to the bottom, foot contortions and crawling on the pedal sole. Settlement occurs only in seawater that contains, or had previously contained, living barnacles. Metamorphosis is irreversible and involves the resorption of the velum, loss of the larval shell, and incorporation of the visceral mass into the cephalopedal mass. Metamorphosis is triggered only when physical contact with living or dead barnacles is made (dead barnacles refers to shell and tissue fragments which are only effective in inducing metamorphosis when they are used in combination with seawater that had previously contained living barnacles).

Settlement and metamorphosis in O. bilamellata is compared with that of other nudibranch species, and its unique settlement response is discussed.     

Targeting transgene expression in research,agricultural, and environmental applications: Promoters used in plant transformation

Summary Plant genetic engineering has contributed substantially to the understanding of gene regulation and plant development, in the generation of transgenic organisms for widespread usage in agriculture, and has increased the potential uses of crops for industrial and pharmaceutical purposes. As the application of geneticallly engineered plants has widened, so has the need to develop methods to fine-tune control of transgene expression. The availability of a broad spectrum of promoters that differ in their ability to regulate the temporal and spatial expression patterns of the transgene can dramatically increase the successful application of transgenic technology. Indeed, a variety of promoters in necessary at all levels of genetic engineering in plants, from basic research discoveries, concepts and question to development of economically viable crops and plant commodities, to addressing legitimate concerns raised about the safety and containment of transgenic plants in the environment. This review covers the characterization and usage of a broad range of promoters employed in plant genetic engineering, including the widespread use of plant promoters with viral and plant origin that drive constitutive expression. Also covered are selected tissue-specific promoters from fruit, seed and grain, tubers, flowers, pistils, anther and pollen, roots and root nodules, and leaves and green tissue. Topics also include organellar promoters, and those found in specific cell types, as well as the development and evaluation of inducible (endogenous and exogenous origin) and synthetic plant promoter systems. Discussions on the relevance and potential pitfalls within specific applications are included.     

Viking and Medieval Settlement in the Faroes: People,Place and Environment

Apart from the possible, but unproven presence of some Irish hermits, the Norse colonizers of the Faroe Islands arrived in an unsettled landscape around A.D. 800. The archipelago was essentially unwooded and rich in bird and marine life. The area of land suitable for settlement and farming was relatively meagre and concentrated in coastal areas; inland areas were suitable for shielings (summer pasture) and subsequently more extensive grazing (outfield) activities. Reconstruction of the settlement distribution has not been a well-developed aspect of Faroese historical study. Using archaeological and documentary evidence, we are able to present the first comprehensive distribution map of Norse settlement, which emphasizes an overwhelmingly coastal focus of considerable density. Using historical (including place-names), archaeological, and environmental evidence, we examine the nature and organization of the Viking (early Norse) and medieval (later Norse) settlement. Colonization and economic activity in the islands were strongly influenced by topographic and ecological factors. This, along with social organization, was subject to influences which may have derived, at least in part, from experiences in a Norwegian homeland.     

Birth,Death, and Diversification of Mobile Promoters in Prokaryotes

A previous study of prokaryotic genomes identified large reservoirs of putative mobile promoters (PMPs), that is, homologous promoter sequences associated with nonhomologous coding sequences. Here we extend this data set to identify the full complement of mobile promoters in sequenced prokaryotic genomes. The expanded search identifies nearly 40,000 PMP sequences, 90% of which occur in noncoding regions of the genome. To gain further insight from this data set, we develop a birth–death–diversification model for mobile genetic elements subject to sequence diversification; applying the model to PMPs we are able to quantify the relative importance of duplication, loss, horizontal gene transfer (HGT), and diversification to the maintenance of the PMP reservoir. The model predicts low rates of HGT relative to the duplication and loss of PMP copies, rapid dynamics of PMP families, and a pool of PMPs that exist as a single copy in a genome at any given time, despite their mobility. We report evidence of these “singletons” at high frequencies in prokaryotic genomes. We also demonstrate that including selection, either for or against PMPs, was not necessary to describe the observed data.     

Community Attachment: The Complexity and Consequence of the Natural Environment Facet

The primary objective of this paper is to examine more closely the complex nature of the natural environment dimension of community attachment using the narratives of local community members. This work seeks to build and elaborate on previous quantitative analyses that demonstrated two distinct dimensions of community attachment––social and natural environment. The findings reveal several distinct facets of the natural environment dimension of community attachment and demonstrate both a discreet perception of the natural environment in terms of community attachment as well as one that is more embedded within the social context of a particular lifestyle. The findings further demonstrate the need to include consideration of the natural environment in the broader assessment of community attachment and bolster previous quantitative research findings.

Reduced Use of Antibiotic Growth Promoters in Diets Fed to Weanling Pigs: Dietary Tools,Part 2

Diets formulated to maximize performance of weanling pigs need to support the development of intestinal tissue, support intestinal colonization with beneficial, mainly lactic acid-producing bacteria, and support development of the intestinal and overall immune system. This objective is not likely to be achieved using one single strategy, but there is strong evidence that diets formulated with cereal grains other than corn, with a low concentration of crude protein and with the use of direct-fed microbials, will improve intestinal health and performance of weanling pigs. Further improvements may be observed if the grain part of the diet is fermented prior to feeding or if the diet is fed in a liquid form, but the need for specialized equipment limit the implementation of this strategy. Dietary supplements such as essential oils and nucleosides or nucleotides may also be useful, but more research is needed to verify the effects of these substances.     

Proteomic analysis of larvae during development, attachment, and metamorphosis in the fouling barnacle, Balanus amphitrite

The barnacle, Balanus amphitrite, is one of the primary model organisms for rocky-shore ecology studies and biofouling research. This barnacle species has a complex life cycle during which the swimming nauplius molts six times and transforms into a cyprid stage. Cyprids must attach to a surface to metamorphose into a juvenile barnacle. To clarify the overall profile of protein expression during larval development and metamorphosis, 2-DE was used to compare the proteome of the nauplius, the swimming cyprid, the attached cyprid, and the metamorphosed cyprid. The proteome of the swimming cyprid was distinctly different from that of other life stages and had about 400 spots. The proteomes of the attached and metamorphosed cyprids were similar with respect to major proteins but had significantly lower numbers of spots compared to that of swimming larval stages. Obviously, synthesis of most proteins from swimming cyprids was switched off after attachment and metamorphosis. Our advanced MS analysis (MALDI-TOF/TOF MS/MS) allowed us to identify the proteins that were differentially and abundantly expressed in the swimming cyprid. These proteins included signal transduction proteins (adenylate cyclase and calmodulin) and juvenile hormone binding proteins. In summary, for the first time, we have analyzed the global protein expression pattern of fouling marine invertebrate larvae during metamorphosis. Our study provides new insights into the mechanisms of barnacle larval metamorphosis and also provides a foundation for exploring novel targets for antifouling treatments.     

Changes in RNA,DNA, protein contents and growth of turbot Scophthalmus maximus larvae and juveniles

The growth potential of turbot Scophthalmus maximus larvae and juveniles was studied using nucleic acid‐based indices and protein variables. The experiment was carried out from 4 to 60 days post hatching (dph). A significant increase in instantaneous growth rate during metamorphosis and retarded growth rate during post‐metamorphic phase were observed. Ontogenetic patterns of DNA, RNA and protein all showed developmental stage‐specific traits. The RNA:DNA ratio decreased up to 12 dph, then increased rapidly till 19 dph and fluctuated until 35 dph followed by a decline to the end. The RNA:DNA ratio was positively correlated with growth rate of juveniles during the post‐metamorphic phase, whereas this ratio was not a sensitive indicator of growth during the pre‐metamorphic phase and metamorphosis. The protein:DNA ratio showed a similar tendency to the RNA:DNA ratio. Changes of DNA content and protein:DNA ratio revealed that growth of S. maximus performed mainly by hyperplasia from 4 to 12 dph and hypertrophy until 21 dph during the pre‐metamorphic larval phase. Growth was dominantly hypertrophical from the early‐ to mid‐metamorphosing phase and hyperplastic thereafter. The results show that the DNA content and protein:DNA ratio can evaluate growth rates of larval and juvenile S. maximus on a cellular level.     

On microalgal settlements and the sluggish development of marine biofouling in Port Blair waters,Andamans

Settlement of microalgae was investigated on Perspex®, aluminium and zinc coupons immersed in Port Blair Bay waters for over 3 months. Commencement of fouling was exceptionally slow, and few microalgae were found until 14 days. Settlement occurred thereafter, and 47 microalgal species contributed to the fouling. The dominant forms belonged to the genera Navicula and Nitzschia, whereas Coscinodiscus eccentricus, Gyrosigma balticum and Trichodesmium erythraeum also accounted for high proportions of the settlements. The dominance of Nitzschia sigma was particularly marked on zinc coupons, suggesting an ability by the organism to resist toxicity. Settlement of both centric and pennate diatoms was observed in the early and mid periods, and absolute dominance of the pennate diatoms subsequently. The fouling mass was low even after 103 days, and it is speculated that strong ultraviolet radiation might be the prime reason for the sluggish development of marine biofouling in these oceanic island waters.     

The Embryonic Origin of Neurosensory Cells and the Role of Nerve Cells in Metamorphosis in Phialidium gregarium (Cnidaria,Hydrozoa)

Summary

The embryonic origin of the nervous system in Phialidium gregarium was investigated. Entoderm-free planulae, surgically produced by bisection at mid-gastrulation, and normal planulae were examined by light and electron microscopy to determine their cellular composition. The cell types that occur in the epidermis of the normal planula were described. The entoderm-free planulae were found to be devoid of interstitial cells and their derivatives, the nematocytes and ganglion cells. Neurosensory cells were present, however, indicating that they are derivatives of the ectodermal epithelium.

The role of nerve elements in the initiation of metamorphosis was also examined. Normal and entoderm-free planulae treated for four hours with 0.4% colchicine at two, three, or four days of development fail to undergo cesium-induced metamorphosis. Since such treatment in other hydrozoans eliminates interstitial cells and their derivatives [1-3], it might be argued that ganglion cells are necessary to initiate metamorphosis. The observation that entoderm-free planulae, devoid of interstitial cell derivatives, are capable of responding to induction by bacteria or cesium, however, indicates that in Phialidium the colchicine effect is on other cell types. The results are compared with findings for other Cnidaria.     

Settlement preferences in coral-reef fishes: Effects on patterns of adult and juvenile distributions,individual fitness and population structure

Abstract Coral-reef fishes exhibit a wide range of habitat preferences at settlement. However, the consequences of these preferences to fitness and population dynamics are poorly known. We critically evaluate evidence for these consequences from recent studies of settlement preferences, and note that most studies have concentrated on only a few common taxa. We recommend that this taxonomic base be broadened, and that settlement preferences be incorporated into future studies of the link between larval supply and population dynamics of reef fishes.     

Genetic polymorphism and trade-offs in the early life-history strategy of the Pacific oyster, Crassostrea gigas (Thunberg, 1795): a quantitative genetic study

We investigated genetic variability and genetic correlations in early life-history traits of Crassostrea gigas. Larval survival, larval development rate, size at settlement and metamorphosis success were found to be substantially heritable, whereas larval growth rate and juvenile traits were not. We identified a strong positive genetic correlation between larval development rate and size at settlement, and argue that selection could optimize both age and size at settlement. However, trade-offs, resulting in costs of metamorphosing early and large, were suggested by negative genetic correlations or covariances between larval development rate/size at settlement and both metamorphosis success and juvenile survival. Moreover, size advantage at settlement disappeared with time during the juvenile stage. Finally, we observed no genetic correlations between larval and juvenile stages, implying genetic independence of life-history traits between life-stages. We suggest two possible scenarios for the maintenance of genetic polymorphism in the early life-history strategy of C. gigas.     

Attachment styles and emotional content, stress, and conflict in dreams of romantic partners.

Expanding on previous research investigating the link between dreams and attachment, participants in committed dating relationships were recruited to fill out dream diaries for 1 week. It was hypothesized that when dreaming about romantic partners (attachment figures), dream content would vary by attachment style, such that insecurely attached individuals would experience a different quality of dream, emotionally and cognitively. At Time 1, participants completed a self-report measure of attachment style, and then completed a dream diary at home each morning for 7 days. Dreams that contained romantic partners were coded by double-blind research assistants for emotional content, with a focus on attachment-related emotions and stressful expressions. Anxious-attached and avoidant-attached participants experienced significantly more stress and conflict, and scored significantly higher on specific emotions such as anxiety and jealousy in such dreams. Secure scores did not correlate with any specific or general emotion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

磁性附着体用于牙列缺损修复的临床观察及对牙周微生态的影响

目的:研究磁性附着体用于牙列缺损修复的临床效果及对牙周微生态的影响。方法:选取2014年8月至2015年8月我院接诊的80例牙列缺损患者作为研究对象,按照随机数表法分为观察组40例和对照组40例。对照组采用常规修复,观察组采用磁性附着体治疗,观察两组患者治疗后固定力、咀嚼效力、舒适程度、语言功能、外观及牙周微生态。结果:治疗后,观察组固定力、咀嚼效力大于对照组[(4.07±0.38)N vs(3.10±0.29)N,(0.80±0.23)%vs(0.59±0.21)%],两组比较差异具有统计学意义(P0.05);观察组舒适程度、语言功能、外观均优于对照组[(4.21±0.45)score vs(3.10±0.42)score,(4.79±0.50)score vs(3.90±0.42)score,(3.98±0.61)score vs(2.76±0.56)score],两组比较差异具有统计学意义(P0.05);观察组PLI、PD显著小于对照组[(1.34±0.31)°vs(1.49±0.43)°,(1.53±0.29)mm vs(1.67±0.32)mm],两组比较差异具有统计学意义(P0.05)。结论:磁性附着体治疗牙列缺损疗效显著,能够减少对牙周组织的损伤,提高舒适度和咀嚼功能。     

Analysis of Genes and Proteins in Acidithiobacillus ferrooxidans During Growth and Attachment on Pyrite Under Different Conditions

Microbes are able to enhance the sulfide mineral decomposition, which lead to the formation of AMD. Attachment of bacterial cells to the mineral surface is an important process for pyrite oxidation by Acidithiobacillus ferrooxidans. The selective advantage of bacterial adhesion is considered to favor the surface localization of bacterial populations as nutritionally favorable. Environmental factors determine cell accumulation or dissociation of attachment. In our study, the amount of sessile cells increased rapidly during the initial stage of attachment on pyrite. Planktonic cells showed high activity leading to the accumulation of large colonies on the pyrite surface. We found three proteins to be up-regulated significantly. Additionally, by matching the sequences of the three proteins to the Pfam database, we found that they are related to adhesion, pili biosynthesis and movement. When we replaced pyrite with glass to provide an inert surface that abolished electrostatic forces, we found that cell attachment was maintained under nutrient-rich conditions but drastically reduced under conditions of limited nutrients or the presence of the inhibitor homoserinelactone. Our results are consistent with the idea that starvation may lead to inhibition of attachment by an unknown mechanism that allows bacteria to search for nutrient-rich habitats.     

Metamorphosis in the paired species of lampreys, Lampetra fluviatilis (L.) and Lampetra planeri (Bloch): 2. Quantitative data for body proportions, weights, lengths and sex ratios

Representatives of the various Stages (1–9) in the metamorphosis and short adult life of the brook lamprey, Lampetra planeri , were used to provide quantitative data to describe the pattern of changes that take place during this period of the life cycle. During the transformation of the oral hood into an oral disc, this ventral region of the snout first declines in length before increasing markedly. The branchial region declines in length and remains relatively smaller than in the ammocoete, a feature probably correlated with the concomitant internal changes in the pharynx which permit a change from a unidirectional to a tidal respiratory flow. The eye increases in size only through the initial Stages (1–5). The main period of fin enlargement occurs rather later in metamorphosis than the above changes.
During maturation the two initially separate dorsal fins increase further in height and eventually become separated only by a notch. Differences between the two sexes are found in the relative size of the disc and fins, the larger structures of the male probably being related to their greater activity in spawning behaviour. Measurements on metamorphosed L. fluviatilis confirm that in this species the eye and disc are relatively larger than in L. planeri. Data are presented which illustrate that in collections taken during the metamorphosis of both species the males are smaller and slightly more numerous than the females and that transformation is initiated at a longer length in L. planeri than in L. fluviatilis .     

Seasonal settlement and succession of fouling communities in Kalpakkam, east coast of India

Seasonal distribution and community succession of macrofoulants were studied using concrete panels in the coastal waters of Kalpakkam, east coast of India, for a period of two years. The panels were suspended at 1 m, 4 m and 7 m depths and categorised into short-term and long-term exposures. A high total of 105 fouling taxa were recorded. The major fouling organisms observed were hydroids, barnacles, mussels, anthozoans and ascidians. Considerable faunistic and biomass variations were noticed both with respect to season and depth. The month of panel exposure had a significant influence on the succession of fouling communities. On the short-term panels, the maximum fouling biomass was 64 kg m^–2 in 30 days at 4 m depth, whereas on the long-term panels, it was 250 kg m^–2 after 216 days at 4 m depth. A comparison with the biomass values reported from elsewhere shows that biomass build-up in Kalpakkam coastal waters is one of the highest ever reported. Such a very high biomass accumulation is due to the extremely dense settlement of mussels, especially the green mussel,Perna viridis (L).     

Metamorphosis in the paried species of lampreys, Lampetra fluviatilis (L.) and Lampetra Planeri (Bloch): I. A description of the timing and stages

A large number of larval, metamorphosing and adult nonarasitic lampreys, lampetra planeri, were collected from three different rivers and placed in a morphological series. The characteristic changes were then described and used to propose a sequence of Stages (1–9). The first signs of metamorphosis (Stages 1–2), which could occasionaly be found as early as late June, are characterized by the eruption and enlargement of the eyes. This is followed by rapid transformation of the the oral hood into an oral disc, and changes in the shape of the pharyngeal region (Stages 2–5). Pronounced alterations in body pigmentation, enlargement of the fins and the development of teeth occur during Stages 4 to 6. The vast modifications involved in Stages 2 to 6 take place relatively repidly in the period between approximately mid-July and mid-September. The subsequent changes which occur more slowly, eventually lead to the production of immature (Stage 7) and sexually mature adults (Stage 8). Mature males are characterized by the presence of a urinogenital papilla, while the females posses a post-cloacal fin-like fold and greatly distended trunk. Spawning took place between late March and late April with the spent animals (Stage 9) dying soon afterwards. The above sequence of Stages was then compared with those found in a smaller sample of the parasitic and ancestral species L. fluviatilis. The early metamorphosing stages in both species are apparently indistinguishable but clear differences atart to appear at Stage 5 when the body surface of L. fluviatilis is assuming a distinct silvery sheen. This trend becomes more marked in Stages 6 and 7, at wich time the river lamprey also has a more pronounced eye and disc and a slimmer trunk. Stage 7 in L. fluviatilis represents animals migrating to the sea in either the autumn or spring to commence their trophic phase. On the other hand this Stage in L. planeri may be regarded as representing a massive contraction of adult Stages and is in many ways similar to the early upstream migrants of parasitic species.     

Development of feeding structures in larval fish with different life histories: winter flounder and Atlantic cod

The size at which feeding structures developed and shifts in head proportions occurred, differed between Atlantic cod Gadus morhua and winter flounder Pseudopleuronectes americanus. The sequence and timing of the development of feeding structures may not be dependent on size, but may occur because they are necessary to meet specific requirements offish larvae feeding in the plankton. In early larval stages development of feeding structures was similar in number and type and was necessary for first-feeding in both species. In later stages, significant differences between species occurred in the timing of the development of feeding structures. In cod differentiation of new structures and changes in head proportions occurred at about two-thirds of the way through larval life, which coincided with an increase in growth. In flounder changes in feeding morphology did not occur during the symmetrical larval stage, but occurred only after metamorphosis to the asymmetrical demersal juvenile stage. Differences between cod and flounder in the size at which feeding structures develop may reflect life history adaptations expressed in the duration of the pelagic larval stage, as well as differences in juvenile habitat and feeding ecology.     

Fouling of an anion exchange chromatography operation in a monoclonal antibody process: Visualization and kinetic studies

Fouling of chromatographic resins over their operational lifetimes can be a significant problem for commercial bioseparations. In this article, scanning electron microscopy (SEM), batch uptake experiments, confocal laser scanning microscopy (CLSM) and small‐scale column studies were applied to characterize a case study where fouling had been observed during process development. The fouling was found to occur on an anion exchange (AEX) polishing step following a protein A affinity capture step in a process for the purification of a monoclonal antibody. Fouled resin samples analyzed by SEM and batch uptake experiments indicated that after successive batch cycles, significant blockage of the pores at the resin surface occurred, thereby decreasing the protein uptake rate. Further studies were performed using CLSM to allow temporal and spatial measurements of protein adsorption within the resin, for clean, partially fouled and extensively fouled resin samples. These samples were packed within a miniaturized flowcell and challenged with fluorescently labeled albumin that enabled in situ measurements. The results indicated that the foulant has a significant impact on the kinetics of adsorption, severely decreasing the protein uptake rate, but only results in a minimal decrease in saturation capacity. The impact of the foulant on the kinetics of adsorption was further investigated by loading BSA onto fouled resin over an extended range of flow rates. By decreasing the flow rate during BSA loading, the capacity of the resin was recovered. These data support the hypothesis that the foulant is located on the particle surface, only penetrating the particle to a limited degree. The increased understanding into the nature of the fouling can help in the continued process development of this industrial example. Biotechnol. Bioeng. 2013; 110:2425–2435. © 2013 Wiley Periodicals, Inc.