Ciliates as a food source for marine planktonic copepods

Copepods of the genusEurytemora, isolated from the Patuxent River, a tributary of Chesapeake Bay, were fed suspensions of the ciliateUronema isolated from the Rhode River, a subestuary of Chesapeake Bay. Grazing by copepods was determined by the decrease in numbers of ciliates, which were monitored by both direct counting and particle size analysis. Results from both methods of analysis showed significant reduction in the numbers ofUronema in the suspension whenEurytemora was present. Survival of copepods with ciliates added as food source was significantly longer than without ciliates. Analysis of field samples collected in the fall showed that ciliates comprised approximately 20% of the total plankton biomass at selected sampling sites. The results of the laboratory and field studies indicate that copepods can feed on ciliates and suggest that, in nature, ciliates may comprise an important source of food for copepods.     

Food source availability and interspecific dominance as structural mechanisms of ant-plant-hemipteran multitrophic networks

Extrafloral nectar of plants and honeydew of hemipterans is a food source extensively explored by ants. Although basically a sugary liquid food, nectar and honeydew are composed of different nutrients and offered in distinct ways; thus, ants must interact differently with plants and hemipterans. In this study we assessed the availability and dominance of nectar of extrafloral nectaries and honeydew of sap-sucking hemipterans (i.e., sugar-based resources) as mechanisms regulating interaction frequency and structuring ant-plant-hemipteran networks. We studied 12 plant species (240 shrubs, 20 per species) and 12 hemipteran species (240 aggregations, 20 per species) that interacted with 26 ant species in an area of Rupestrian Fields (Rocky Montane Savannah), Brazil. We observed that the 7 ant species that collected honeydew were a subset of the 25 ant species feeding on nectar, but the highly interacted species Camponotus crassus was the same for both subnetworks. The ant-plant subnetwork exhibited a nested pattern of interaction with a low degree of specialization, while the ant-hemipteran subnetwork exhibited lower nestedness but higher specialization. We found a positive relationship between the offer of EFNs and the number of interactions with ants, probably resulting from reduced competition in plants with high availability of EFNs. However, hemipteran species that were most abundant did not interact with more species of ants, probably because of the numerical dominance of the species tending all hemipteran aggregations, regardless of size. However, segregation between ant species was higher than expected by chance for both plants and hemipterans, confirming a deterministic factor (i.e., competition between ant species) regulating the frequency of interactions. In summary, the availability of ENFs seems to be an important mechanism regulating ant-plant interactions, while numerical dominance seems to be an important mechanism structuring ant-hemipteran interactions.     

Ligula intestinalis infection as a potential source of bias in the bioindication of endocrine disruption in the European chub Leuciscus cephalus

European chub Leuciscus cephalus collected from five localities in the lowland and subalpine regions of Austria were analysed for oestrogenic effects of endocrine-disrupting chemicals and the presence of the plerocercoid of the tapeworm Ligula intestinalis. Of 1494 chub analysed, only seven (six males, one female) were found to be infected with single, but large plerocercoids up to 15 cm in length. Ligula-infected fish showed comparatively immature gonads, as demonstrated by the gonadosomatic index and gamete developmental stages. Plasma levels of the egg precursor protein vitellogenin also showed concentrations ranging below the detection limit. The present results indicate that chub infected with L. intestinalis and exposed to exogenous oestrogenic compounds can result in reduced gonadal maturation and produce false oestrogen-positive diagnoses in male fish. For plasma vitellogenin levels, L. intestinalis infections can result in false oestrogen-negative diagnoses in male and female fish.     

Male mate choice, male availability and egg production as limitations on polyandry in the red-necked phalarope

In sequentially polyandrous birds, a female's second mate faces a substantial risk of cuckoldry due to rapid mate switching and stored sperm. Secondary males are potentially available to females because males arrive asynchronously and/or are recycled into the breeding pool following nest predation. In a study of red-necked phalaropes, Phalaropus lobatus, a sex-role reversed shorebird, we tested the hypotheses that the proportion of females that become polyandrous is proximately limited by: (1) the ability of females to produce eggs, (2) the availability of males as mates and (3) male mate choice. In a colour-banded population in which rates of nest loss were manipulated by researchers, females that produced second clutches required similar lengths of time to complete clutches as those contemporaneously producing first clutches, and increased their egg size relative to their first clutch, making egg limitation unlikely. There was no correlation between an annual measure of males' availability as potential mates following nest losses and the proportion of females that were polyandrous. The majority of males that lost clutches (66%) re-paired with their original female significantly more often than expected by random mate choice (P<0.0001). Although 76% of polyandrous nestings involved renesting males, only 6% (N=46) of renesting males changed mates if their original female was still available. Renesting males that changed mates did not select for or against females that had already produced clutches (NS). Our results suggest that the level of polyandry in this species is not constrained by the females' abilities to produce more eggs or by the number of males recycling back into the breeding pool. Instead, the proportion of females that become polyandrous is limited by males choosing to renest with their original females, thereby decreasing their probability of caring for eggs potentially fertilized by a female's previous mate.     

The Golgi as a potential membrane source for autophagy

In macroautophagy (hereafter autophagy), a morphological hallmark is the formation of double-membrane vesicles called autophagosomes that sequester and deliver cytoplasmic components to the lysosome/vacuole for degradation. This process begins with an initial sequestering compartment, the phagophore, which expands into the mature autophagosome. A tremendous amount of work has been carried out to elucidate the mechanism of how the autophagosome is formed. However, an important missing piece in this puzzle is where the membrane comes from. Independent lines of evidence have shown that pre-existing organelles may continuously supply lipids to support autophagosome formation. In our analysis, we identified several components of the late stage secretory pathway that may redirect Golgi-derived membrane to autophagosome formation in response to starvation conditions.     

The source of the nutrients required for egg production in zebra finches Poephila guttata

The source of nutrients used for egg formation are poorly known for most bird species. This study of the zebra finch Poephila guttata showed that food intake did not increase during egg production, but the decline in female body reserves of protein and fat were sufficient to account for most of the nutrients in a clutch of four eggs. Female birds significantly reduced their activity levels during ova enlargement, which may play a role in diverting resources to egg production. Birds increased their intake of calcium-rich food items when eggs were being laid, and this intake accounted for all the calcium needed for eggshell formation. The zebra finch depends heavily on stored body reserves for egg formation, which is probably unusual in small passerines.     

The Golgi as a potential membrane source for autophagy

In macroautophagy (hereafter autophagy), a morphological hallmark is the formation of double-membrane vesicles called autophagosomes that sequester and deliver cytoplasmic components to the lysosome/vacuole for degradation. This process begins with an initial sequestering compartment, the phagophore, which expands into the mature autophagosome. A tremendous amount of work has been carried out to elucidate the mechanism of how the autophagosome is formed. However, an important missing piece in this puzzle is where the membrane comes from. Independent lines of evidence have shown that preexisting organelles may continuously supply lipids to support autophagosome formation. In our analysis, we identified several components of the late stage secretory pathway that may redirect Golgi-derived membrane to autophagosome formation in response to starvation conditions.Key words: lysosome, membrane biogenesis, protein targeting, secretory pathway, stress, vacuole, yeast     

The potential for hybridization in freshwater copepods

The importance of hybridization and hybrid zones in pelagic systems is largely unknown, in part because planktonic species are generally assumed to be reproductively isolated. However, lakes in their entirety represent potential hybrid zones throughout which sympatric species may mate and hybridize. Recent field evidence for the existence of intermediate phenotypes together with behavioral observations of heterospecific matings suggest that hybridization may be much more common than previously thought in these systems. This study examines the potential for hybridization of two related copepod species, Diaptomus minutus and D. pygmaeus, that co-occur in lakes throughout the northeastern United States. Field and experimental laboratory data were collected to: (1) compare the spatial and temporal occurrence of these two congeners in a single lake; (2) quantify the extent to which mating errors occur insitu; (3) examine the species specific mating cues that potentially affect the probability of hybridization; and (4) determine the potential for gametic compatibility and hybrid viability of these two species. D. minutus and D. pygmaeus are spatially and temporally sympatric, and the timing of their reproductive activity can be coincident insitu. One-directional mating errors occur frequently in both the laboratory and the field (e.g., upto 70% of D.minutus females in situ may carry spermatophores from D.pygmaeus males). Very low but successful production of hybrids also occurs, demonstrating that their gametes are indeed compatible and their hybrids are sometimes viable. These results underscore the potential for hybridization to play a greater role in speciation and contribute more to phenotypic diversity in aquatic crustacean communities than previously shown. Received: 25 March 1996 / Accepted: 4 April 1997     

Marine algae as a potential pharmaceutical source for anti-allergic therapeutics

The prevalence of allergic diseases such as asthma, atopic dermatitis, and allergic rhinitis has increased during the last two decades and contributed a great deal to morbidity and an appreciable mortality in the world. Until now, few novel efficacious drugs have been discovered to treat, control or even cure these diseases with a low adverse-effect profile. Meanwhile, glucocorticoids are still the mainstay for the treatment of allergic disease. Therefore, it is necessary to isolate novel anti-allergic agents from natural resources. Recently, marine algae have received much attention as they are a valuable source of chemically diverse bioactive compounds with numerous health benefit effects. This review focuses on anti-allergic agents derived from marine algae and presents an overview of their pharmaceutical potential in the treatment of allergic disorders.     

Commercial potential for Haematococcus microalgae as a natural source of astaxanthin

As a result of high production costs, commercial products from microalgae must command high prices. Astaxanthin produced by Haematococcus is a product that has become a commercial reality through novel and advanced technology. Cultivation methods have been developed to produce Haematococcus containing 1.5-3.0% astaxanthin by dry weight, with potential applications as a pigment source in aquaculture, poultry feeds and in the worldwide nutraceutical market.     

Summer egg production rates of paracalanid copepods in subtropical waters adjacent to Australia's North West Cape

The biological oceanography of waters adjacent to Australia's North West Cape (21° 49 S, 114° 14 E) was studied during the austral summers of 1997/98 and 1998/99. We measured egg production rate (EPR) by the small paracalanid copepods that dominated the calanoid community. Bottle incubation experiments were conducted at a shallow (20 m) station in the mouth of Exmouth Gulf, and at a shelf-break station (80 m). In 1997/98, we measured EPR by Paracalanus aculeatus, P. indicus, Acrocalanus gracilis and Bestiolina similis, but in 1998/99, we concentrated on P. indicus. Maximal observed EPRs by Paracalanus and Acrocalanus species were 30 eggs female^–1 d^–1, but B. similis attained only 17 eggs female^–1 d^–1. Sporadic measurements of EPR by P. aculeatus minor (maximum 4 eggs female^–1 d^–1) and Parvocalanus crassirostris ( 9 eggs female^–1 d^–1) were also made. However, maximal EPRs were seldom achieved and were often less than 10 eggs female^–1 d^–1. There was no difference between EPR of either P. indicus or B. similis in 1997/98 and 1998/99, despite differences in temperature. Trophic resources severely limit copepod egg production in this area. We suggest that variability and skewness of egg production data derived from individual incubations may be used to judge the degree of food limitation of the population and the variability in feeding success between individuals. The dominance of small copepods and the invariance in their EPR suggest that pulses in physical forcing and subsequent primary production will be severely damped by trophodynamic processes before reaching larval fish.     

Clutch size in parasitoids: the egg production rate as a constraint

Summary In many species of insect parasitoids, adult females mature eggs as they search their environment for hosts. In such species, the number of mature eggs, at the point of finding a host, is a function of the interhost time and the rate of egg maturation. Assuming that interhost search times are variable, we use a version of the marginal value theorem to derive a decision rule for optimizing the time spent exploiting individual hosts; this indirectly determines clutch size. We find that a threshold search time exists above which a female should simply lay her currently mature eggs and depart from the host. However, when the search time has been less than the threshold, a female should oviposit, but then remain on the host to mature and lay additional eggs, until the threshold time is reached.     

Seasonal cycles in population abundances and egg production rates in the planktonic copepods Centropages typicus and Acartia clausi

Laboratory studies on the seasonal cycling of egg productionrates for Centropages typicus and Acartia clausi did not reflectseasonal changes in densities for these species at sea. Maximumegg production rates occurred from autumn to spring when populationabundances at sea were low. In late spring, an increment inpopulation numbers was followed by a drastic decline in eggdeposition which continued into summer. The percentage lossdue to mortality, calculated using egg data and total numberof copepodid stages CIII and CIV recorded at sea {small tilde}2weeks later, indicated greatest mortality (80–99%) fromeggs to copepodids during periods of high breeding intensity.These results suggest that high and low density phases in populationnumbers may be the outcome of variations in reproductive potentialand survival rates of eggs and immature stages rather than reproductivepotential per se.     

Adipocytes as a new source of catecholamine production

Catecholamines are an important regulator of lipolysis in adipose tissue. Here we show that rat adipocytes, isolated from mesenteric adipose tissue, express genes of catecholamine biosynthetic enzymes and produce catecholamines de novo. Administration of tyrosine hydroxylase inhibitor, alpha-methyl-p-tyrosine, in vitro significantly reduced concentration of catecholamines in isolated adipocytes. We hypothesize that the sympathetic innervation of adipose tissues is not the only source of catecholamines, since adipocytes also have the capacity to produce both norepinephrine and epinephrine.     

Coffee oil as a potential feedstock for biodiesel production

A preliminary evaluation of the feasibility of producing biodiesel using oil extracted from defective coffee beans was conducted as an alternative means of utilizing these beans instead of roasting for consumption of beverage with depreciated quality. Direct transesterifications of triglycerides from refined soybean oil (reference) and from oils extracted from healthy and defective coffee beans were performed. Type of alcohol employed and time were the reaction parameters studied. Sodium methoxide was used as alkaline catalyst. There was optimal phase separation after reactions using both soybean and healthy coffee beans oils when methanol was used. This was not observed when using the oil from defective beans which required further processing to obtain purified alkyl esters. Nevertheless, coffee oil was demonstrated to be a potential feedstock for biodiesel production, both from healthy and defective beans, since the corresponding oils were successfully converted to fatty acid methyl and ethyl esters.     

Vitreous humour as a potential DNA source for postmortem human identification

PURPOSE: The aim of this study was the assessment of vitreous humor as a potential DNA for forensic human postmortem identification. MATERIAL AND METHODS: Vitreous humor samples were collected using two alternative approaches from 25 corpses of either sex during autopsies. DNA was extracted by standard organic method. Recovered DNA was quantitiated fluorometrically. AmpFlSTR SGM Plus kit and ABI 310 Genetic Analyzer (Applera) were used to obtain genetic profiles. RESULTS: Different DNA yields were quantitated in vitreous body depending on cause of death and sampling approach. CONCLUSION: Vitreous humor is a potential DNA for forensic human postmortem identification depending on a sampling method used.