An Ecological Study of the Fauna Inhabiting the Sublittoral Marine Alga Saccorhiza polyschides (Lightf.) Batt.

Summary The animals found on the fronds of the laminarian alga Saccorhiza polyschides are described. The sporophytes supported a fauna which was distinct from that of the surrounding rock, but was basically similar to that of other laminarian algae. Several animal species were however, much more abundant on S. polyschides than on other laminarians. A number of species were found to have a localised distribution on the host plant. The distribution of the epifauna on the alga seems to be chiefly the result of factors in the external environment particularly the degree of water movement and of silting. The epifauna varied in abundance and composition at different sites. In localities exposed to excessive water turbulence only a few species survived, although the gastropods Patina pellucida and Lacuna vincta were at their most abundant in such localities. Marked seasonal variations in the composition of the epifauna were found at Port Erin, Isle of Man, over a period of two years. The variations were related to both the seasonal behaviour of the animal species and to the annual cycle of growth and decay exhibited by the host plant. It is clear that the plant and its epifauna are each an important factor in the ecology of the other.

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Zusammenfassung Die Tiere, die auf den Wedeln der Laminaria-Alge Saccorhiza polyschides gefunden wurden, werden beschrieben. Die Sporophyten ern?hrten eine Fauna, die sich von der auf dem benachbarten Gestein unterschied, aber im Grunde der anderer Laminaria-Algen ahnelte. Verschiedene Tierarten waren jedoch viel zahlreicher auf S. polyschides als auf anderen Laminaria. Eine Reihe von Arten fanden sich an einzelnen Stellen auf dem Wirt. Die Verbreitung der Epifauna auf der Alge scheint in erster Linie das Ergebnis von Faktoren der Umwelt zu sein, v.a. des Grades der Wasserbewegung und der Verschlammung. Die Epifauna ver?nderte sich in Fülle and Zusammensetzung an verschiedenen Stellen. In Lokalitaten, die ausserordentlicher Wasserturbulenz ausgesetzt waren, überlebten nur ein paar Arten, obwohl die Gastropoden Patina pellucida und Lacuna vincta in solchen Lokalit?ten am h?ufigsten vorkamen. Deutliche jahreszeitliche Ver?nderungen in der Zusammensetzung der Epifauna fanden sich in Port Erin, auf der Insel Man, über einen Zeitraum von zwei Jahren. Die Ver?nderungen standen im Zusammenhang mit dem jahreszeitlichen Verhalten der Tierarten und dem Jahreszyklus von Wachstum and Zerfall, der von der Wirtpflanze gezeigt wird. Es ist klar, dass die Pflanze and ihre Epifauna beide einen wichtigen Faktor in der ?kologie der Anderen darstellen.

     

Quantitative studies on brown algal phenols. I. Estimation of absolute polyphenol content of Ascophyllum nodosum (L.) Le Jol. and Fucus vesiculosus (L.)

Methods for estimating the absolute polyphenol content of the brown algae Ascophyllum nodosum (L.) Le Jol. and Fucus vesiculosus (L.) have been developed and tested. Polyphenols were extracted almost quantitatively from Ascophyllum nodosum using aqueous acetone, whereas this procedure was somewhat less efficient with Fucus vesiculosus. Colorimetric methods based on the Folin-Denis reagent, Brentamine Fast Red 2G Salt, and vanillin-H₂SO₄ were applied to acetone-free extracts for determination of polyphenol content relative to suitable reference compounds. Gravimetric methods based on hide powder and on haemoglobin were employed to derive ‘estimation factors’ (EFs) which allow calculation of the absolute polyphenol content from the relative polyphenol content. The values calculated for absolute polyphenol content are considered to be reasonably accurate, despite imprecisions in the methods and despite often large standard deviations, and re-emphasize the potential physiological and ecological significance of brown algal polyphenols. Although the precise EFs calculated here are not valid for other brown algae, the methods are considered to be generally applicable to other Phaeophyceae.     

Dormancy of Medicago marina (L.) seed

Medicago marina (L.) is a Mediterranean species whose seeds show strong dormancy that prevents germination. We used an integrated approach of physiological analyses and proteomics to investigate the mechanisms that control M. marina dormancy/germination and that underlie stress tolerance. First, we evaluated the effects on dormancy breaking of the following treatments: mechanical scarification, freezing at −20 °C, storage for 4 months and heating at 100 °C for 1 h. Mechanical scarification and freezing were the most effective treatments in overcoming dormancy. The role of abscisic acid (ABA) in M. marina dormancy was studied by ELISA immuno-enzymatic assay. The ABA content of germinated and non-germinated mature (control) and treated seeds was determined. The level of ABA was higher in treated seeds than in control seeds; the most significant increase occurred in the heated seeds. A comparison of the ABA level in the germinated, control and treated seeds suggests that different mechanisms modulate ABA content in response to different stresses, and that a specific ABA-signalling pathway regulates germination. Proteomic analysis revealed 46 proteins differentially expressed between treated and untreated seeds; 14 of these proteins were subsequently identified by mass spectrometry. Several of the proteins identified are important factors in the stress response, and are involved in such diverse functions as lipid metabolism, protein folding and chromatin protection. Lastly, an analysis of the phosphoproteome maps showed that the function of many proteins in seeds subjected to temperature treatment is modulated through post-translational modifications.     

Quantitative studies on brown algal phenols. II. Seasonal variation in polyphenol content of Ascophyllum nodosum (L.) Le Jol. and Fucus vesiculosus (L.)

The content of extractable polyphenols in the brown algae Ascophyllum nodosum (L.) Le Jol. and Fucus vesiculosus (L.) was measured at ≈28-day intervals for one year. Colorimetric methods based on the Folin-Denis, Brentamine, and vanillin-H₂SO₄ reactions were used to estimate relative contents of polyphenols, and these values were converted to absolute contents using the gravimetric method introduced earlier. Relatively little error was introduced by variations in the qualitative composition of the extracted polyphloroglucinols.There appeared to be a significant temporal correlation between polyphenol content and the reproductive state of the algae. The content of polyphenols in A. nodosum was at a minimum (≈9–10% of dry matter) during the period of maximum fruit body shedding (late May), and reached a maximum (≈12–14% of dry matter) during the ‘winter season’. In F. vesiculosus, the minimum (≈8–10% of dry matter) was one to two months later, just before the period of maximum fertility, and thereafter rose to a maximum (≈11–13% of dry matter) during the period of sterility. These results furthermore suggest that the bulk of the polyphenols are not readily accessible as reserve components, and indicate that modifications may be needed in the ‘chemical defense’ and ‘waste product’ hypotheses concerning the significance of brown algal polyphenols.     

The effect of Stratiotes aloides L. and nutrients on the growth rate of Lemna minor L.

We tried to find the reasons for frequently observed low biomass of Lemna minor among floating rosettes of Stratiotes aloides as opposed to the abundance of Spirodela polyrhiza in these stands. The effect of S. aloides on L. minor was analysed in outdoor culture experiments. The duckweed collected from among dense stands of the floating form of S. aloides (test sites) showed a significantly lower growth rate than that from stands free of the water soldier (control sites). Water from the latter stands was significantly richer in nitrate-nitrogen and ammonium-nitrogen, but not in soluble reactive phosphorus suggesting possible nutrient depletion as a reason for observed differences. Growth rates of L. minor were indeed significantly correlated with in situ concentrations of all dissolved nutrients and showed saturation at around 0.18 mg N-NH₄ dm⁻³ and 0.05 mg SRP dm⁻³ above which the growth rates did not increase significantly. We used stepwise regression to test the combined effect of nutrients and the presence/absence of S. aloides on the growth rate of L. minor. The regression showed a negligible effect of ammonium ions and nitrates on the growth rate of the duckweed. At low concentrations of soluble reactive phosphorus the presence of both the S. aloides and SRP concentrations significantly affected the growth of L. minor. Above saturating SRP concentrations none of the two effects was significant. Results of our experiments seem to suggest that the presence of S. aloides exerts a negative effect on the growth of L. minor only at low concentrations of soluble phosphorus. Since the depletion of nutrients in water by the floating form of S. aloides is unlikely, we point to S. polyrhiza as a superior competitor for nutrients and suggest a possible allelopathic effect of the water soldier on L. minor.     

Growth regulators from the seaweed Chondrus crispus L. (Lyn.)

The level of auxin-like compounds extracted from the seaweed Chondrus crispus L. (Lyn.) is reported. Their presence before and after alkaline hydrolysis is studied to confirm that the bound auxin-like substances are present in algae in greater concentration than the free form.     

Studies on nitrate reductase activity in Laminariadigitata (Huds.) Lamour. I. Longitudinal and transverse profiles of nitrate reductase activity within the thallus

The distribution of the enzyme nitrate reductase (NR) within the thallus of the brown alga Laminaria digitata (Huds.) Lamour is described for plants sampled from the east coast of Scotland in May and June when growth rates are at a maximum. Highest NR activities (≈ 0.2 μmol NO₃^? reduced·g^?1 wet wt·h^?1) occurred in the mature blade. NR activities declined towards the basal meristematic region of the blade. Activities in the stipe and holdfast were also low, being between 0.05 and 0.07 μmol NO₃^? reduced·g^?1 wet wt·h^?1. The activities of the enzyme glutamine synthetase (GS), which is important in the assimilation of NH₄⁺, showed a similar distribution within the blade to those of NR.The transverse profile of NR activity in the stipe exhibited a decline from the outer to the inner tissues. Maximum activities (0.13 μmol NO₃^? reduced·g^?1 wet wt·h^?1) occurred in the meristoderm, while those of the cortex and medulla were 0.04 and 0.01 μmol NO₃^? reduced·g^?1 wet wt·h^?1 respectively.These data indicate that most of the NO₃^? assimilation occurs in the mature blade rather than in the meristematic tissue where there is a high nitrogen demand for growth. The data are consistent with the maintenance of meristematic growth by the internal transport of organic nitrogen from the mature blade.     

Regeneration of the penis in Balanus balanoides (L.)

In Balanus balanoides (L.) the penis is ‘lost’ each autumn. The regeneration of the penis is described. The primordium contains mesenchyme. The pedicel structures develop early as thickened areas of the exoskeleton and give rise to the characteristic structural features of the mature pedicel. Tissue differentiation begins in the pedicel and later extends to the penis proper which becomes annulated. The ductus eventually opens by a terminal invagination of the exoskeleton.     

Effects of salinity on leaf growth and survival of the Mediterranean seagrass Posidonia oceanica (L.) Delile

The main aim of this study was to estimate the effects of salinity variation on the Mediterranean seagrass Posidonia oceanica (L.) Delile and its attached epiphytes. Leaf growth and survival of this plant were tested in several short-term (15 days) mesocosms experiments under controlled conditions between February 2001 and November 2001. Plants collected from shallow meadows at Alicante (SE Spain), with an ambient salinity of 36.8-38.0 psu, were placed in tanks of 300 L with an additional overhead light and exposed to different salinity treatments (ranging from 25 to 57 psu) during 15 days. To estimate the mortality and growth recuperation, in some experiments shoots were returned to control salinity (38 psu). Leaf growth was measured in the laboratory where epiphytic fauna and flora were removed from leaves, with a razor blade, to determine their biomass.P. oceanica was negatively influenced by increased salinity. Shoots showed a significant decrease in growth and survival, whereas epiphyte biomass did not show a clear response because of their high variability. Maximum leaf growth occurred between 25 and 39 psu. In addition, plants suffered considerable mortality at salinities above 42 psu and below 29 psu, with 100% mortality at 50 psu. In salinities between 39 and 46 psu, surviving plants were able to regain their original growth rate when returned to normal seawater salinity (38 psu). These results suggest that P. oceanica is one of the most sensitive seagrasses to salinity increments it is more tolerant to salinity reductions (25.0-36.4 psu), perhaps due to the terrestrial origin of seagrasses.     

Hoarding by honeybees (Apis mellifera L.)

The food hoarding by groups of fifty bees kept in small cages and provided with sugar syrup was studied. Less food was stored in a new comb than in an old one, whether the old comb had been used for storing food or rearing brood, and there was less in drone than in worker combs. The presence of light, larvae and the odour of honey discouraged storage of syrup, but the presence of a queen encouraged it. The amount stored also varied with the environmental temperature, the age of the bees concerned and with their previous physiological and behavioural experience including food deprivation and length of confinement. Increased food in honeystomachs sometimes compensated for less stored in combs.     

Effects of water depth and seed provenance on the growth of wild rice (Zizania aquatica L.)

Annual wild rice (Zizania aquatica L.), a species of conservation concern, is an ecologically and culturally important aquatic grass found in stands in the near shore habitats of lakes and rivers in the Midwest and along the eastern coast of North America. This study examined the effects of water depth and seed provenance on the early growth of three Indiana wild rice stands (collected from two lakes) under greenhouse conditions in 2009. Plants were grown at water depths of 46 cm, 23 cm, 0 cm, or −15 cm and harvested either at the first floating leaf stage or at 48 days after transplanting. Wild rice growth was affected by both water depth and seed provenance. The dry weight of roots, stems, leaves, and inflorescences, total biomass, number of tillers, number of leaves, and total leaf area were the lowest in the −15 cm treatment. These vegetative growth parameters also decreased with increasing water depth from the 0 cm treatment. Differences in growth between seed sources were found, supporting the hypothesis that genetic differences among relatively isolated wild rice stands may influence the success of efforts to conserve this species.     

Studies in the biochemistry of cirripede eggs. IV. The free Amino-acid pool in the eggs of Balanus balanoides (L.) and B. balanus (L.) during development

Changes in the ‘free’ amino acids, betaine, and trimethylamine oxide during the development of the eggs of Balanus balanoides (L.) and B. balanus (L.) have been determined; the results are given in terms of μM/g dry wt, μM/g water, and μM/10⁶ eggs. The amino acids are derived from the yolk proteins the net composition of which is known. Free amino acids are present in considerable quantity, as is commonly the case with crustacean tissue. Changes in the individual amino acids are discussed. B. balanus eggs contain large, and relatively constant, amounts of sarcosine; its function is unknown but large quantities are present in the more highly evolved cirripedes so far examined. A possible relation between betaine glycine, and sarcosine relative to choline metabolism is considered. Large amounts of taurine are present. There is a striking increase in β-alanine in the late stages of development; in B. balanoides it comes to be the most, and in B. balanus the third most common amino acid; its possible involvement in purine metabolism is considered. The relation between the amounts of the various entities in the eggs and in the bodies of the adult are examined.     

In vitro characterization of the Ac locus in white clover (Trifolium repens L.)

Microsomal fractions from developing shoots of adult white clover plants (of genotype AcAc) and cotyledons of dark germinated clover seedlings can synthesize 2-hydroxy-2-methylpropanenitrile and 2-hydroxy-2-methylbutanenitrile, the aglycone precursors of the cyanogenic glucosides, linamarin and lotaustralin, from various precursors in the presence of NADPH. l-Valine, 2-methylpropanal oxime, and 2-methylpropanenitrile are converted to 2-hydroxy-2-methylpropanenitrile and are detected as cyanide and acetone. l-Isoleucine and 2-methylbutanal oxime are converted to 2-hydroxy-2-methylbutanenitrile and are detected as cyanide and 2-butanone. At least two steps in these conversions are missing in microsomes from plants of genotype acac.     

Effect of gamma irradiation on OKRA (Abelmoschus esculentus L.)

The investigation was carried out to evaluate the effect of different doses of gamma rays (100, 200, 300, 400, 500 Gy and zero doses as control) on various morphological aspects of Abelmoschus esculentus. A comparison of the results of different doses with control showed that gamma irradiation significantly affected various parameters. Days to germination were almost the same as compared to control, but 400 Gy took minimum days to germination. Germination % was 100% both in control and the irradiated plants. 100 Gy took minimum days for flower initiation as compared to control and other doses. Fruit initiation early occurred in 100Gy as compared to other doses, and fruit maturation occurred early in 300 Gy as compared to control. Plant height was significantly increased at 500 Gy as compared to control. Number of fruits per plant was significantly decreased at 200 Gy as compared to control. Fruit length decreased in all doses but in control fruit length was maximum. Number of seeds per fruit was maximum at control, fresh and dry weights of seeds were increased in control as compared to other doses. The number of nodes decreased in all doses but in the control the numbers of nodes were maximum. Branches were increased in100Gy as compare to 200, 300,400,500 Gy as well in control. Numbers of leaves were increased in 300 Gy as compared to other doses.     

Brown shrimp (Crangon crangon, L.) functional response to density of different sized juvenile bivalves Macoma balthica (L.)

Variability in infaunal bivalve abundance in the Wadden Sea is largely determined by recruitment variability. Post-settlement, but pre-recruitment bivalve mortality is high and related to the occurrence of their most abundant predator, the brown shrimp Crangon crangon. To investigate if the mortality patterns of newly settled bivalves can be explained by the foraging behavior of brown shrimp, we carried out experiments on shrimp functional response to three size classes of juveniles of the Baltic Tellin Macoma balthica. The functional response curves for all three prey sizes (0.62 mm, 0.73 mm, and 0.85 mm) were the hyperbolic Holling's type II. The attack rate was highest for the smallest prey size (a = 0.31, medium and large prey a = 0.22); the handling time was longest for the largest prey size (T_h = 29 s, small and medium prey T_h = 15 s). Thus, a large body size is advantageous for the bivalves over the whole density range. Knowledge of individual foraging behavior is needed to model predation mortality of bivalves. The consumption rates in the experiment were theoretically high enough to account for M. balthica mortality in the field.     

The effect of rutin on growth,fecundity and food utilization in Acheta domesticus (L.)

Growth of larvae of Acheta domesticus to the adult stage on an artificial diet was improved significantly by the addition of 0.1% rutin to the diet. Fecundity was also increased. These results cannot be explained by a stimulation of feeding by rutin. They appear to be due to an effect on the utilization of the food, brought about possibly by an action on gut movement, on gut transport or on the microbiol flora.