Chemical characteristics and gelling properties of agar from two Philippine Gracilaria spp. (Gracilariales, Rhodophyta)

The chemical structure of agars extracted from Philippine Gracilaria arcuata and G. tenuistipitata were determined by NMR and infrared spectroscopy. Agar with alternating 3-linked 6-O-methyl-β-D-galactopyranosyl and 4-linked 3,6-anhydro-2- O-methyl-α-L-galactopyranosyl units was isolated from G. arcuata, while the agar from G. tenuistipitata possesses the regular agarobiose repeating unit with partial methylation at the 6-position of the D-galactosyl residues. Both agars exhibit sulphate substitution at varying positions in the polymer. Chemical analyses reveal higher 3,6-anhydrogalactose and lower sulphate contents in alkali-modified than in native agar from both samples. Also, alkali modification enhanced agar gel strength and syneresis. Native G. arcuata agar produces a viscous solution (2000 cP at 75 °C) with a high gelling point (>60 °C) that forms a soft gel even after alkali modification (gel strength: <300 g cm⁻²). On the other hand, the agar from G. tenuistipitata exhibits gel qualities typical of most Gracilaria agars. This revised version was published online in June 2006 with corrections to the Cover Date.     

Highly methylated agar from Gracilaria edulis (Gracilariales, Rhodophyta)

The structure and gelling properties of alkali-modified agar from Gracilaria edulis were investigated. ¹H and ¹³C NMR experiments revealed a basic repeating unit of alternating 3-linked 6- O-methyl-β-D-galactopyranose and 4-linked 3,6-anhydro-α-L-galactopyranose. Partial methylation at O-2 of the anhydrogalactose moiety was also revealed. Meanwhile, the O-4 of the methylated galactose residue was detected to exhibit partial sulfation by NMR and FT-IR spectroscopy. The gel strength and syneresis index of the extracted agar were considerably enhanced by the addition of sodium, potassium, and calcium ions. The ion-driven gelation and peculiar sulfate position conferred the agar's similarity to κ-carrageenan. This revised version was published online in July 2006 with corrections to the Cover Date.     

Influence of alkali treatment on agar from Gracilaria cornea from Yucatán, México

The effect of alkali treatments on the yield, rheological and chemical properties of agar from Gracilaria cornea growing along the Yucatáncoast were studied in order to evaluate its potential for industrial use inan attractive economic standpoint. Alkali treatment was carried out with NaOH concentrations of 0.5%, 1%, 3% and 5% in a water bath at 80, 85 and 90 °C. Agar yield, gel strength, gelling and melting temperatures, sulphate, 3,6-anhydro-galactose and ash content weredetermined. The different combinations of NaOH concentration and treatment temperature strongly influenced agar characteristics. There was a variation in the agar content for all NaOH treatments and temperature combinations, ranging between 14.5% to 22.1%. Although the yields obtained for 0.5% NaOH at all temperatures and 1% NaOH at 80 and 85°C were higher than those required by the industry, the physical and chemical characteristics of the agar were similar to those obtained fornative agar from the same species. The gel strengths, sulphate content and gelation hysteresis obtained with agar from the 1% NaOH treatment at 90 °C are in the range required by the food industry. Treatments with 3% and 5% NaOH at all temperatures improved significantly the agar quality giving higher gel strengths (974–1758 g cm ^-2) than those reported for other Gracilaria species. This revised version was published online in August 2006 with corrections to the Cover Date.     

Seasonal accumulation of metals by red alga Gracilaria verrucosa (Huds.) Papens. from Thermaikos Gulf, Greece

Concentrations of Fe, Pb, Cu, Zn and Cd were determined during one season in the red alga Gracilaria verrucosa, sediment and seawater from the Thermaikos Gulf, Greece. This region has been subject to change due to increases in industrial and domestic activities. The relative abundance of metals in G. verrucosa and seawater decreased in the order: Fe>Zn>Pb>Cu>Cd and in the sediment: Pb>Fe>Zn>Cu>Cd. Cadmium concentration in the alga correlated positively with that in seawater. There was positive correlation between Fe concentrations in the alga and those of the Zn and Cu. The concentrations of metals in the alga showed no significant differences between the stations. Lead, Zn and Cu concentrations in the alga were slightly higher at Biamyl, whereas Cd was higher at Perea and Fe at Nea Krini. Seasonal variation of metal concentrations in the alga was significant for Cd and Fe. Copper and Fe increased from winter to summer, whereas Cd was the opposite. Zinc concentrations were minimum and Pb concentrations were maximum during spring. These variations are discussed in relation to tissue age, life cycle, ambient concentrations of metals and other environmental conditions. Cd and Pb concentrations inG. verrucosa in the Thermaikos Gulf were higher and those of Cu and Zn were lower than in other species of the genus. This revised version was published online in August 2006 with corrections to the Cover Date.     

Organismic determinants and their effect on growth and regeneration in Gracilaria gracilis

The growth of Gracilaria gracilis (Stackhouse) Steentoft, Irvine et Farnham was examined by studying the effect of organismic determinants such as thallus length, position along the thallus and branching. Knowledge of these factors is essential in order to increase production from suspended seaweed rafts seeded with vegetative G. gracilis fragments. Seeding netlons with seaweed material freshly collected from subtidal populations provided up to 30% higher relative growth rates than seaweed maintained on the netlons for successive months. Initial seedstock length greatly affected growth rates and yields such that 30-cm thalli fragments resulted in growth rates 14% higher than for 10-cm fragments. This difference is suggested to be due to the higher contribution to overall biomass by growth of lateral branches. Comparisons of the growth of apical and basal fragments suggest that growth takes place over the entire length of the thallus, but that the apex contributes more to overall elongation than does the proximal part. The removal of apical meristems resulted in an enhanced branching frequency with production of four times as many branches as intact fragments. Evidence is also provided for extensive morphological differentiation following long periods of rapid growth. These thalli have very high frequency of branching, are hollow due to the disintegration of medullary cells and are considered to be completely senescent. These factors have implications for the successful cultivation of G. gracilis on commercial mariculture systems. This revised version was published online in July 2006 with corrections to the Cover Date.     

Yield, chemical composition and gel strength of agarocolloids of Gracilaria gracilis, Gracilariopsis longissima and the newly reported Gracilaria cf. vermiculophylla from Roscoff (Brittany, France)

Agarocolloids were extracted from field samples of Gracilaria gracilis, Gracilariopsis longissima and the newly reported Gracilaria cf. vermiculophylla harvested at different periods of the year near Roscoff (France). Native and alkali modified extracts were characterized by GLC, HPLC and FT-IR spectroscopy. The main components of agarocolloids isolated by freeze-thawing method, were 3,6-anhydrogalactose and galactose. In addition, minor components (6-O-methyl-galactose, 4-O-methyl-galactose and sulfate groups ranging from 4.4 up to 6.6% [w/w]) were detected. The highest rate of 6-O-methylgalactose was observed in agarocolloids from vermiculophylla (14 mole%). Sulfates were mainly branched on C4 of the D-galactose in gracilis and Gs. longissima agarocolloids. G. vermiculophylla agaroids isolated by EtOH and NaCl precipitations from the syneresis water were characterized by a high sulfation on C6 of galactose and a low sulfation on C2 of 3,6-anhydrogalactose. Native agarocolloid gel strengths from Gracilaria species were clearly higher than those of Gracilariopsis. Alkali treatments reduced the sulfate levels but increased slightly the gel strengths. An approximation of the polymer sizes carried out with colorimetric assays indicated that the polymer sizes were higher in G. gracilis than observed in Gs. longissima. This revised version was published online in June 2006 with corrections to the Cover Date.     

Comparison of growth rate in culture,dry matter content,agar content and agar quality of two New Zealand red seaweeds,Gracilaria chilensis Bird,McLachlanet Oliveira andGracilaria truncata Kraft

Plant growth rates and agar characteristics were compared for two agarophytes,Gracilaria chilensis (Gracilariales, Rhodophyta) andG. truncata, so that the suitability ofG. truncata for mariculture could be assessed.G. chilensis plants grew steadily in the laboratory culture system at rates of 5–8% day^-1 (mean Relative Growth Rate) throughout the 6 week experimental period, with no decline in health.G. truncata plants grew at rates of 2–4% day^-1 for 5 weeks, but during the sixth week their apical tips became necrotic and growth rates fell to zero. There was no significant difference in the dry matter content (as a percentage of their wet weight) between the two species ofGracilaria, with values falling in the range of 16–19%. Slightly higher agar yields were obtained from alkali-treatedG. chilensis (17–20% dry matter) than from untreatedG. truncata (16–18%) although the agar fromG. truncata formed softer gels from which it was more difficult to recover. The gel strength of untreated agar extracted fromG. chilensis was very low (ca. 100 g cm^-2 for a 1% gel) but when an alkali treatment step was included in the extraction process, it increased to 520 g cm^-2 for a 1% gel. Contrary to an earlier report, untreatedG. truncata agar also had a very low gel strength (ca. 100 g cm^-2 for a 1.5% gel), but it rose to only 167 g cm^-2 after alkaline treatment.     

Population Fluctuation of Three Parasitic Nematodes in Florida Citrus

In Florida, Tylenchulus semipenetrans on citrus has two high and two low population levels each year. High levels occur in April-May and November-December, and low levels, in February-March and August-September. Population increases occur about 4-5 weeks after the spring and fall flush of root growth. Populations of Pratylenchus coffeae on citrus varied widely, and were not related to season. Populations of P. brachyurus showed seasonal variation with a high in June-July and a low in March-May. Males of T. semipenetrans and P. coffeae were found throughout the year, whereas males of P. brachyurus were rare and were found only during November and December.     

PROTOPLAST ISOLATION AND CELL DIVISION IN THE AGAR-PRODUCING SEAWEED GRACILARIA (RHODOPHYTA)1

Methods were developed for the isolation of large numbers of healthy protoplasts from two species of the agarophyte Gracilaria; G. tikvahiae McLachlan and G. lemaneiformis (Bory) Weber-van Bosse. This is the first report of protoplast isolation and cell division in a commercially important, phycocolloid-producing red seaweed, as well as for a member of the Florideophycidae. The optimal enzyme composition for cell wall digestion and protoplast viability consisted of 3% Onozuka R-10, 3% Macerozyme R-10, 1% agarase and 0.5% Pectolyase Y- 23 dissolved in a 60% seawater osmoticum containing 1.0 M mannitol. The complete removal of the cell wall was confirmed by several different methods, including electron microscopic examination, and the absence of Calcofluor White (for cellulose) and TBO (for sulfated polysaccharide) staining. Spontaneous protoplast fusion was observed on several occasions. Protoplast viability was dependent upon the strain and age of the parent material, as well as the mannitol concentration of the enzyme osmoticum. Cell wall regeneration generally occurred in 2-6 days; cell division in 5-10 days. Protoplast-produced cell masses up to the 16-32 cell stage have been grown in culture. However, efforts to regenerate whole plants have been unsuccessful to date.     

Inhibition of Ectocarpus siliculosus infestations with copper chloride in tank cultures of Gracilaria gracilis

This study investigated copper chloride as an inhibitor of infestations of Ectocarpus siliculosus in Gracilariagracilis (Stackhouse) Steentoft, Irvine and Farnham grown in outdoor tank cultures. Copper at concentrations of 400 and 800 μg L^-1 Cu²⁺ inhibited E. siliculosusin one experiment. A reduction in the specific growth rates of G. gracilis was found for both concentrations of copper chloride in two experiments. G. gracilis recovered completely with in three weeks in one experiment, while no recovery was found in the other. Three and 5 weeks after treatment with low and high concentrations of copper chloride respectively the specific growth rates of G. gracilis was higher than that of the control in one experiment. A feeding experiment was conducted to determine the effect of copper-treated G. gracilis, used as fodder, on the growth rates of Haliotes midae (abalone) of two size classes. An isolated occurrence of growth rate inhibition of H. midae could be demonstrated in both size classes 3 months after the startof the experiment. This revised version was published online in August 2006 with corrections to the Cover Date.     

Seasonal changes in the chemical and gelling characteristics of agar from Gracilaria verrucosa collected in Turkey

The chemical and gelling properties of agar from G. verrucosa collected from Izmit bay in Turkey at different months of the year were studied. Purification of agar was performed by using amylase treatment and isopropyl alcohol precipitation. The phycocolloid content was between 24.0–43.0% of the algal dry weight and was maximum in summer collected algae. Relative total sulfate and 3,6-anhydrogalactose content in the agar were determined from the ratios of infrared spectroscopy band intensities at 1250/2920 cm^–1 and 930/2920 cm^–1, respectively. 3,6-anhydrogalactose and sulfate contents were the highest in agar from algae collected from June until November and January until July, respectively. The gel strength of native agar were the highest from in autumn collected algae and increased to about 1250 N m^–2 after alkali treatment. Thus, this study demonstrated that G. verrucosa from Turkey produces an agar with optimal chemical and gelling properties after alkali-treatment in fall and winter collected algae and may be used for industrial agar production.     

利用红外相机视频数据进行库姆塔格沙漠地区野骆驼集群行为研究的可行性

野骆驼(Camelus ferus)生性机警, 且栖息于远离人迹、自然条件极端恶劣的荒漠、半荒漠地区, 其种群动态和行为生态学研究一直较为缺乏。本研究通过在库姆塔格沙漠地区进行不同季节的野外观测和连续水源地红外相机监测, 对野骆驼的集群行为进行了研究。2011-2013年, 在库姆塔格沙漠地区进行了8次野外调查, 共记录野骆驼64群, 个体430峰。非繁殖季节野骆驼集群大小平均为2.94±0.67峰; 而繁殖季节野骆驼集群大小平均为10.74±3.08峰。野外观测数据证明了野骆驼集群行为存在季节性差异, 倾向于冬季繁殖季节的集群。并于2012年10月至2013年9月期间, 在11个水源地设置11台红外相机, 共记录野骆驼281群745峰。与野外调查结果相比, 红外相机数据表明繁殖期间和非繁殖期间野骆驼集群大小没有显著差异(t = 0.322, P = 0.748)。水源地的地形因素、红外相机监测视角和监测时间的限制可能是造成这一差异的原因。但是两种方法的结果均表明野骆驼在阿尔金山北麓比西湖地区容易形成较大的集群; 同时, 繁殖季节野骆驼最大集群的规模要大于非繁殖季节。尽管利用红外相机进行动物集群行为研究存在一定的局限性, 但与传统基于野外调查的方法相比, 无论是经济上还是实用性方面, 利用红外相机都为我们开展动物行为学研究提供了新的手段。     

Seasonal variation in plasma lipids and lipases in young healthy humans

Although intermediate metabolism is known to follow circadian rhythms, little information is available on the variation in lipase activities (lipoprotein and hepatic lipase, LPL and HL, respectively) and lipids throughout the year.

In a cross-sectional study, we collected and analysed blood from 245 healthy students (110 men and 135 women) between 18 and 25 years old from the University of Barcelona throughout the annual campaign (March, May, October and December) of the blood bank. All subjects gave their written informed consent to participate. All blood samples were taken after breakfast at 8:00 and 11:00 am.

Plasma glucose, total plasma protein, triacylglycerides (TAG), free fatty acids (FFA), free cholesterol and esterified cholesterol (FC and TC, respectively), cholesterol in low-density lipoproteins (cLDL), cholesterol in high-density lipoproteins (cHDL), phospholipids (PL) and lipase activities (LPL and HL) were determined. Cosinor analysis was used to evaluate the presence (significance of fit cosine curve to data and variance explained by rhythm) and characteristics of possible 12-month rhythms (acrophase, MESOR and amplitude).

Statistically significant seasonal rhythms were detected for all the variables studied except proteins, with most of them peaking in the winter season. The lowest value for cLDL and the HL occurs in summer, while for cHDL and the LPL it is in winter.

These findings demonstrate for the first time that in physiological conditions, plasma LPL and HL activities and lipids follow seasonal rhythms. The metabolic significance of this pattern is discussed.     

Individual, nightly, and seasonal variation in calling behavior of the gray tree frog, Hyla versicolor: implications for energy expenditure

We investigated individual, nightly, and seasonal variationin calling behavior of a population of gray tree frogs (Hylaversicolor) from Connecticut, USA. Repeated recordings of individualmales on seven nights revealed significant differences amongmales in calling rate on all but one night and differences innumber of pulses per call and number of pulses produced perhour (pulse effort) on four nights. Most males reduced callingactivity late at night (after 2230 h), but some maintained arelatively steady rate of call production before dropping outof the chorus. Data collected for 26 individuals recorded onthree or more nights throughout the breeding season revealedsignificant differences among males in calling rate, numberof pulses per call, and pulse effort, but repeatabilities forall three variables were low (0.17, 0.35, and 0.12, respectively).The highest repeatability was for number of pulses per call,a variable strongly influenced by proximity to calling neighbors,probably because males often interacted with neighbors at similardistances on several successive nights. Males tended to reducethe number of pulses per call as the season progressed and thedistance between neighbors decreased, but they showed no clearseasonal change in calling rate or pulse effort. There was asubstantial seasonal decline in the number of hours of chorusactivity, resulting in a median decrease of 43% in nightly energyexpenditure by calling males.