Ecological studies on streptocephalus dichotomus baird

Summary Streptocephalus dichotomus occurs in a wide variety of shallow andThe maximum period during which these animals occur was 18Studies on both seasonal and day time variations of the physicoThe rate of increase in the population is more or less identical inThe length frequency distribution in the different ponds showsSex ratio does not appear to follow any definite pattern at anyFemales start to bear eggs when 1.7 cm long and the maximumTwo genera, Branchinella kugenumaensis and S. dichotomus were seenThis work formed a part of the thesis submitted for the award of the Degree of     

Changes in biochemical composition and energy utilization during metamorphosis of leptocephalous larvae of the bonefish (Albula)

Synopsis Energy use and changes in whole-body content of lipid, protein, nitrogen, carbohydrate and ash were followed during metamorphosis of leptocephalous larvae of the bonefish (Albula). During metamorphosis, which requires about 8–12 days, larvae lost about 3–4 mg of lipid, or about 50% of the total lipid content. Lipid levels, calculated on a dry weight basis, showed no discernible trends, with values ranging from 138–185 mg (g dry wt)^–1. Protein content was 8.4 mg per larva and showed no significant change. However, protein levels increased from 147 to 329 mg (g dry wt)^–1. Nitrogen content decreased slightly from about 3.5 to 3.2 mg per larva. A comparison of protein and nitrogen values, expressed as % dry weight, showed that, in larvae which were just beginning to metamorphose, 70% of the total nitrogen was non-protein nitrogen (NPN). The NPN decreased to 58% of the total nitrogen towards the end of metamorphosis. Carbohydrate content fell from about 3.5 to 0.6 mg per larva, which represents an 83% loss. Carbohydrate levels also fell from about 81 to 32 mg (g dry wt)^–1. In addition, most of the carbohydrate appears to be bound to protein. Ash content decreased by 52%, from 4.6 to 2.2 mg per larva. Caloric content fell slightly from about 182 to 141 calories per larva whereas caloric density showed no discernible trends, with values ranging from 4.180 to 4.725 kcal (g dry wt)^–1. These results indicate that metamorphosing leptocephali, which apparently do not feed, probably derive most of their energy requirements from metabolizing endogenous lipid and carbohydrate stores formed during the premetamorphic interval.     

Proximate biochemical composition and caloric content calculated from elemental CHN analysis: a stoichiometric concept

Summary Carbohydrate, lipid, and protein compositions are stoichiometrically related to organic CHN (carbon, hydrogen, nitrogen) contents. Elemental CHN analyses of total biomass and ash, therefore, provide a basis for the calculation of proximate biochemical composition and bomb caloric value. The classical nitrogen to protein conversion factor (6.25) should be replaced by 5.8±0.13. A linear relation exists between the mass fraction of non-protein carbon and the carbohydrate and lipid content. Residual water in dry organic matter can be estimated with the additional information derived from hydrogen measurements.The stoichiometric CHN method and direct biochemical analysis agreed within 10% of ash-free dry biomass (for muscle, liver and fat tissue of silver carp; gut contents composed of detritus and algae; commercial fish food). The detrital material, however, had to be corrected for non-protein nitrogen.A linear relationship between bomb caloric value and organic carbon fractions was derived on the basis of thermodynamic and stoichiometric principles, in agreement with experimental data published for bacteria, algae, protozoa and invertebrates. The highly automatic stoichiometric CHN method for the separation of nutrient contents in biomass extends existing ecophysiological concepts for the construction of balanced carbon and nitrogen, as well as biochemical and energy budgets. Offprint requests to: Institut für Zoologie, Abt. Zoophysiologie, Universität Innsbruck, Peter-Mayr-Str. 1A, A-6020 Innsbruck, Austria     

Anostraca of the Indian Subcontinent

There are 15 species of Anostraca belonging to 6 genera on the Indian Subcontinent. These are:Artemia sp. (reportedly a bisexual form of undetermined species);Artemia parthenogenetica Bowen & Sterling, 1978;Branchinecta orientalis Sars, 1901;Branchinella hardingi (Qadri & Baqai, 1956);Branchinella kugenumaensis (Ishikawa, 1895);Branchinella ornata Daday, 1910;Branchipodopsis acanthopenes (Malhotra & Duda, 1970);Branchipodopsis affinis Sars, 1901;Branchipus schaefferi Fischer, 1834;Chirocephalus priscus (Daday, 1910);Streptocephalus dichotomus Baird, 1860;Streptocephalus echinus Bond, 1934;Streptocephalus longimanus Bond, 1934;Streptocephalus simplex Gurney, 1906;Streptocephalus spinifer Gurney, 1906.Comparing numbers of species for southern India with other reasonably well studied areas, demonstrated that anostracan species richness is higher in the climatically more varied temperate regions than it is in the more uniform tropics. Tropical South India has six species compared to 13 in Arizona (USA), 19 in California (USA), 10 in Morocco, and 14 in Italy.     

Hatching and Postembryonic Development of Streptocephalus Dichotomus Baird (Crustacea : Anostraca)

Summary Hatching and postembryonic development of Streptocephalus dichotomus have been studied. Only dried eggs hatched in the laboratory. Hatching is influenced by desiccation and temperature. Drying for 10 or 20 days and temperature of 30° C seem to be favourable for S. dichotomus eggs to hatch. In S. dichotomus immersion in water up to 120 cm depth has no effect on hatching.Fifteen larval stages are involved in postembryonic development and sex differentiation appears at the eighth larval stages and becomes more pronounced in later stages. S. dichotomus takes 28 days to attain its adult structure in the laboratory at room temperature.This work formed part of the thesis submitted to the University of Madras for the award of the Degree of Doctor of Philosophy in 1970.     

Analysis of protein,carbohydrate and lipid in rotifers

Protein, carbohydrate and lipid amounts were determined for several rotifer species collected directly from the field. Brachionus calyciflorus was the most abundant species; therefore making possible more data for it. An increase in protein content of this species occurred when its concentration in food (µg protein/ml) also increased. Keratella tropica showed a similar pattern, but Asplanchna brightwelli did not.Carbohydrate proved to be the main form of storage in rotifers. In Brachionus calyciflorus females bearing no egg, 8% of the total biomass was carbohydrate; in females bearing one egg, 15% carbohydrate was found. Lipid does not appear to be used for storage since no increase in the amount of lipid was detected in females bearing eggs or embryos. This suggests that lipid has a structural function. Finally, a relationship between rotifer body volume and protein content at a given food concentration was obtained. The cladoceran Daphnia magna follows the same pattern.     

Lipid contents of five species of notothenioid fish from high-Antarctic waters and ecological implications

Comprehensive data are presented on the total lipid contents of five species of notothenioid fish collected during summer 1991 in the Weddell Sea and the Lazarev Sea south of 69°S. The species were selected based on their different modes of life, benthic, benthopelagic and pelagic, to examine how the life style — among other factors — affects the proximate composition of these high-Antarctic fishes. Lipid contents of whole specimens showed an extremely wide range from 3.1 to 67.5% of dry weight (%DW), with corresponding carbon/nitrogen (C/N) ratios between 3.4 and 11.3. Lowest lipid contents were found in the benthic species Bathydraco marri and Dolloidraco longedorsalis with means of 11.0 and 11.9 %DW. The benthopelagic Trematomus lepidorhinus had an intermediate mean lipid content of 20.8 %DW, and the pelagic species Pleuragramma antarcticum and Aethotaxis mitopteryx were richest in lipid with means of 47.0 %DW and 60.8 %DW. There was a pronounced ontogenetic lipid accumulation with increasing size discernible in the lipid-rich species, especially in P. antarcticum. No clear relationship was found between lipid content and sex or maturity in A. mitopteryx and T. lepidorhinus, only the males of B. marri had higher lipid contents than the females. Lipid contents and water contents were inversely correlated. In conclusion, the mode of life of these species was clearly reflected by their lipid contents and lipids seem to have an important function, particularly as buoyancy aids in the pelagic species, which like all notothenioids lack a swim-bladder.     

Egg envelopes of Streptocephalus dichotomus Baird: A structural and histochemical study

The origin, ultrastructure and histochemical properties of the egg membranes in the South Indian anostracan, Streptocephalus dichotomus have been studied. The egg morphology and the ultrastructure of the tertiary membrane of this phyllopod crustacean have been examined both by scanning and transmission electron microscopy. Scanning electron microscopic observations on the egg surface reveal the characteristic ridges on the egg surface with pores. Similarly, the tertiary egg shell of S. dichotomus consists of two distinct layers, an outer cortex and an inner alveolar layer. There are specific differences in the structure and in the relationship of one layer to the other. The alveolar layer is characterised by large lipid droplets and an alveolar mesh. These two layers termed as tertiary layers are secreted by maternal shell glands. The outer tertiary egg layers are phenolically tanned, the precursor materials for tanning being derived from shell gland secretions.     

Chemical composition of antarctic zooplankton during austral fall and winter

Water level, ash content, proximate (protein, lipid, carbohydrate and chitin) and elemental (carbon and nitrogen) composition were analyzed in twentythree species of Antarctic Zooplankton collected during the austral fall (1986) and winter (1988) from the Scotia/Weddell Sea region. Extremes in water level, ash content and organic components were typified by copepods and gelatinous forms. Ostracods and polychaetes were generally similar in composition to copepods, being only slightly higher in water level and ash content. Chaetognaths exhibited a composition intermediate in character with some components similar in value to that shown by crustaceans (i.e. protein) while other components were more in the range of values seen in gelatinous forms (i.e. water level and ash content). Protein was the major proximate component and measured values (as % Afdw) were fairly uniform among non-gelatinous species (x=33.9±6.9). Lipid levels were variable, with high values (>30% AFDW) only found for the copepods Calanoides acutus, Calanus propinquus and Euchaeta antarctica. Carbohydrate values were low in all species examined. Chitin was measured in crustacean species only. With the exception of C. acutus (x=2.5% AFDW chitin), values were similar among species with mean values being slightly higher in fall (x=11.8±2.5) than in winter (x=6.7±1.8). Among non-gelatinous species, the ratio of carbon to nitrogen was positively correlated with the lipid to protein ratio, underscoring the compositional association between elemental and proximate components in these groups. In gelatinous species, the relationship between carbon:nitrogen and lipid:protein was inconsistent and less pronounced. Caloric content was estimated from recovered organic matter for nongelatinous species. As a function of wet weight and dry weight, values reflected differences in water level and ash content among individual species. As a function of ashfree dry weight, values were similar among all species (x=3.6±0.9 kcal/g).Seasonal comparisons were possible for 12 of the 23 species. Among crustaceans, changes in water level and organic components were variable reflecting dissimilar trophic, reproductive or ecological habits among different species. Essentially no change in composition between fall and winter was observed for diapause species (e.g. Calanoides acutus and Rhincalanus gigas) as well as for omnivorous/ carnivorous species (e.g. Gaetanus tenuispinus). Conversely, large compositional changes were evident for Calanus propinquus, a small-particle grazer that relies heavily on lipid reserves. Chaetognaths and some gelatinous species exhibited a considerable decrease in ash content from fall to winter which, for most cases, was mirrored by some degree of increase in lipid level. At present, however, scant data are available to help explain the observed patterns of compositional change within non-crustacean species.     

Seasonal changes in organic composition and caloric content of an Arctic marine amphipod, Onisimus (= Boeckosimus) affinis H.J. Hansen

Protein, lipid, carbohydrate, chitin, ash, and caloric energy contents of the Arctic marine benthic amphipod Onisimus (= Boeckosimus) affinis H.J. Hansen were determined at intervals over two and one half years. The lipid content exhibited the most pronounced seasonal change, from a minimum of about 14–17% of dry wt to a maximum of 25–27% of dry wt. An increase in lipid content in the spring coincided with the reproductive period of the species. Lipid and caloric content decreased during the summer to levels that were maintained through the winter, indicating that the animals do not store significant nutritional reserves for use during the winter. The dry weight proportions of other components were: protein 27.7–38.3%; carbohydrate 1.8–4.0%; chitin 7.8–8.2%; ash 21.3–27.2%. Caloric content varied between 3.29 and 4.18 cal/mg dry wt.     

Compositional profiles of Rhodosporidium toruloides cells under nutrient limitation

Lipid production by the red yeast Rhodosporidium toruloides was explored under nutrient limitation. To determine the compositional profiles of R. toruloides cells, samples were prepared using a continuous cultivation process under nutrient limitation and analyzed via several methods, including Fourier transform infrared spectroscopy and elemental analysis. Under nitrogen limitation, as the dilution rate increased, the cellular lipid content decreased but the carbohydrate and protein contents increased. Under carbon limitation, the cellular lipid, protein, and carbohydrate contents remained relatively constant at the different dilution rates. Moreover, the cellular elemental composition was essentially identical under nitrogen and carbon limitation at a high dilution rate of 0.20 h⁻¹. We also analyzed the consumed carbon to nitrogen (C/N) under different nutrition conditions. The results indicated that the consumed C/N had a major influence on cell metabolism and product formation, which contributed to our understanding of the physiological characteristics of R. toruloides.

     

A seasonal study of the red seaweeds Solieria tenera and three species of Gracilaria from Jamaica

Three species of Gracilaria viz G. cervicornis, G. domingensis, G. verrucosa and Solieria tenera (Gigartinales, Rhodophyta) have been studied for their monthly variation in dry wt yields, ash, soluble carbohydrate, protein, lipid and insoluble carbohydrate contents for one year. The dry wt yields were higher in G. domingensis. Soluble carbohydrate and ash contents showed an inverse relationship in all the species. Protein content was lower, below 5% of the dry wt for all the species. A comparison of protein:carbohydrate ratios showed a similarity between morphologically similar G. domingensis and G. cervicornis in that there was less variation in the ratio. From this, it is assumed that flattened morphology probably is more efficient in maintaining nutrient balance to keep up the growth rates.     

Nitrogen excretion in Streptocephalus Dichotomus Baird (Crustacea: Anostraca)

Summary The total nitrogen excreted by Streptocephalus dichotomus is 1.5177 mg/g/day for males and 1.3875 mg/g/day for females at 30°C.The main excretory product of S. dichotomus is ammonia (75.3%). The rate of excretion of ammonia increased with increase in temperature up to 30°C and at 33°C it decreased.Analyses of covariance revealed that the F ratios are not significant in the case of rate of total nitrogen excretion between the two sexes at 30°C and in the case of rate of ammonia excretion between the two sexes or when comparison is made within the sexes at the different temperatures between 20° and 30°C.This work formed part of the thesis submitted to the University of Madras for the award of the Degree of Doctor of Philosophy in 1970.     

Carbon accumulation in <Emphasis Type="Italic">Rhodotorula glutinis</Emphasis> induced by nitrogen limitation

Background

Oleaginous microorganisms, such as bacterium, yeast and algal species, can represent an alternative oil source for biodiesel production. The composition of their accumulated lipid is similar to the lipid of an oleaginous plant with a predominance of unsaturated fatty acid. Moreover this alternative to conventional biodiesel production does not create competition for land use between food and oleo-chemical industry supplies. Despite this promising potential, development of microbial production processes are at an early stage. Nutritional limited conditions, such as nitrogen limitation, with an excess of carbon substrate is commonly used to induce lipid accumulation metabolism. Nitrogen limitation implies modification of the carbon-to-nitrogen ratio in culture medium, which impacts on carbon flow distribution in the metabolic network.

Results

The goal of the present study is to improve our knowledge of carbon flow distribution in oleaginous yeast metabolism by focusing carbon distribution between carbohydrate and lipid pools in order to optimize microbial lipid production. The dynamic effects of limiting nitrogen consumption flux according to carbon flow were studied to trigger lipid accumulation in the oleaginous yeast Rhodotorula glutinis. With a decrease of the specific nitrogen consumption rate from 0.052 Nmol.Cmol_X^?1.h^?1 to 0.003 Nmol.Cmol_X^?1.h^?1, a short and transitory intracellular carbohydrate accumulation occurred before the lipid accumulation phase. This phenomenon was studied in fed-batch culture under optimal operating conditions, with a mineral medium and using glucose as carbon source. Two different strategies of decreasing nitrogen flow on carbohydrate accumulation were investigated: an instantaneous decrease and a progressive decrease of nitrogen flow.

Conclusions

Lipid production performance in these fed-batch culture strategies with R. glutinis were higher than those reported in the previous literature; the catalytic specific lipid production rate was 0.07 Cmol_lip.Cmol_X*^?1.h^?1. Experimental results suggested that carbohydrate accumulation was an intrinsic phenomenon connected to the limitation of growth by nitrogen when the nitrogen-to-carbon ratio in the feed flow was lower than 0.045 Nmol.Cmol^?1. Carbohydrate accumulation corresponded to a 440% increase of carbohydrate content. These results suggest that microbial lipid production can be optimized by culture strategy and that carbohydrate accumulation must be taken account for process design.

     

Composition and energy density of eggs from two species of freshwater turtle with twofold ranges in egg size

Lipid, protein, ash, carbohydrate and water content and energy density of eggs were measured from different clutches over a range of egg size in two species of freshwater turtle. Dry egg contents consisted of protein (54-60%), lipid (25-31%) and ash (5-6%) while carbohydrate was found to be negligible (<1%). Albumen consisted principally of water ( approximately 98%), and the dry component was composed of protein (47-51%), ash (19-26%) and lipid (18-21%), but contributed only a small amount ( approximately 2%) to overall dry egg contents. Energy density of dry albumen (15-17 kJ/g) was significantly lower than for dry yolk (26-27 kJ/g). Yolk consisted of 62-70% water, and the dry component was composed of protein (54-61%), lipid (25-31%) and ash (5-6%). Fractional concentrations of water, lipid, protein and ash and energy density remained constant over the range of egg size in Emydura signata eggs. In contrast, an increase in the yolk to albumen ratio and a decrease in water content of yolk as egg size increased caused the composition and energy density of Chelodina expansa eggs to vary systematically with egg size.     

First record of the family Thamnocephalidae (Crustacea: Anostraca) from Southeast Asia and description of a new species of Branchinella

During a two-year investigation of freshwater microcrustaceans in Thailand, an undescribed species of fairy shrimp of the genus Branchinella Sayce, 1903 in the family Thamnocephalidae, was discovered. This is the first record of the genus and the family from Southeast Asia and the second anostracan reported from Thailand. The new species, Branchinella thailandensis n. sp. appears to be morphologically intermediate between B. kugenumaensis (Ishikawa, 1895) from Japan and east China, and B. madurai Raj, 1951 from India and Pakistan. B. thailandensis n. sp. was collected from several temporary ponds in 11 provinces of the northeast and the central Thailand, often co-occurring with Streptocephalus sirindhornae Sanoamuang, Murugan, Weekers & Dumont, 2000.     

Chemical composition of the wound plug and entire plants for species of the coenocytic green alga, Caulerpa

Levels of ash, NaOH-soluble protein, lipid, and TCA-soluble carbohydrate were determined tor seven species of the green alga Caulerpa, for both the entire plant and wound plugs produced by cutting the rhizomes or blades. Insoluble carbohydrate was estimated by subtraction. Wound plugs had higher ash levels and a distinctly higher level of total carbohydrate. Both entire plants and wound plugs had low levels of lipid and protein. Carbohydrate is the major component of the wound plug in Caulerpa in contrast to protein reported for Bryopsis.     

Sclerotial development, melanin production and lipid peroxidation bySclerotium rolfsii

Melanin pigments constituted 13.9% (W/W) of sclerotial walls ofSclerotium rolfsii. The lipid and ash contents in sclerotial walls were twice those in hyphal walls of the fungus. Progress in culture age and maturation of sclerotia were always accompanied by increased levels of lipid peroxidation products and melanin. Lipid peroxidation and melanin formation may thus proceed in parallel during sclerotial biogenesis and maturation. Both these processes are strongly affected by Fe²⁺ and by antioxidant vitamins (ascorbic acid), microelements (selenium) and mercapto compounds (glutathione). Myceliogenic germination and lytic activityvia melanin production can thus be affected by (anti)oxidants that could potentially be used for controlling sclerotia-producing fungi without using traditional toxic fungicides.     

Food,feeding and digestion in streptocephalus dichotomus baird (Crustacea: Anostraca)

Summary Gut analysis of Streptocephalus dichotomus revealed that the main source of food is phytoplankton. S. dichotomus is a non-selective filter feeder, taking in all the food-items carried in the feeding currents and passed through the midventral groove. The feeding currents are produced by the thoracic limbs.Feeding experiments have shown that the time taken for the passage of food is directly proportional to the number of days of starvation. Food intake of males did not significantly differ from that of females when fresh animals were used, as well as animals used after one day of starvation.Fresh males as well as females took in significantly more food than starved animals.The digestive enzymes such as carbohydrases, proteases and lipases are present in the gut. The optimal pH for amylase ranged between, 5.8 to 6.6, for protease 7.4 to 8.0 and for lipase 5.2 to 6.5.This work formed a part of the thesis submitted to the University of Madras, in 1970 for the award of the Degree of Doctor of Philosophy.     

Changes in protein, lipid, and carbohydrate content during starvation in the fresh-water limpetAncylus fluviatils (Basommatophora)

Summary The fresh-water limpetAncylus fluviatilis, living in European brooks, was found to have relatively greater carbohydrate and lipid fractions in winter than in summer. During starvation in the winter stage, lipid reserves are diminished first, followed by the carbohydrate reserves. Protein is degraded at nearly equal rates throughout the experiments. Specimens suffering from starvation are not found in the field during winter. Lipid reserves are mainly deposited in the midgut gland, whereas the carbohydrate reserves are distributed more equally among different tissues.A. fluviatilis must feed continuously during the winter period. The results are discussed in relation to data from other Basommatophora.