Polar night ecology of a pelagic predator,the chaetognath <Emphasis Type="Italic">Parasagitta elegans</Emphasis>

The annual routines and seasonal ecology of herbivorous zooplankton species are relatively well known due to their tight coupling with their pulsed food source, the primary production. For higher trophic levels of plankton, these seasonal interactions are less well understood. Here, we study the mid-winter feeding of chaetognaths in high-Arctic fjord ecosystems. Chaetognaths are planktivorous predators which comprise high biomass in high-latitude seas. We investigated the common species Parasagitta elegans around the Svalbard archipelago (78–81°N) during the winters of 2012 and 2013. Our samples consisted of individuals (body lengths 9–55 mm) from three fjords, which were examined for gut contents (n = 903), stable isotopes, fatty acid composition, and maturity status (n = 352). About a quarter of the individuals contained gut contents, mainly lipid droplets and chitinous debris, whilst only 4 % contained identifiable prey, chiefly the copepods Calanus spp. and Metridia longa. The δ¹⁵N content of P. elegans, and its average trophic level of 2.9, confirmed its carnivorous position and its fatty acid profile [in particular its high levels of 20:1(n-9) and 22:1(n-11)] confirmed carnivory on Calanus. Observations of undeveloped gonads in many of the larger P. elegans, and the absence of small individuals <10 mm, suggested that reproduction had not started this early in the year. Its average feeding rate across fjords and years was 0.12 prey ind.^?1 day^?1, which is low compared to estimates of spring and summer feeding in high-latitude environments. Our findings suggest reduced feeding activity during winter and that predation by P. elegans had little impact on the mortality of copepods.     

Lipid composition and trophic relationships of krill species in a high Arctic fjord

Our study deals with the lipid biochemistry of the krill community in the ecosystem of the high Arctic Kongsfjord (Svalbard). During the last decades, Kongsfjord experienced a change in krill species composition due to recent increased advection of Atlantic water masses carrying characteristic boreal as well as subtropical-boreal euphausiids into the ecosystem. The lipid biochemistry and trophic relationships of the species recently inhabiting the Arctic water masses are scarcely known, although a change in a krill population may have a significant impact on the ecosystem. A comparison of nutrition and energy storage strategies, stable isotopes, lipid profiles and fatty acid compositions showed remarkable differences between the krill species. These reflected the diverse feeding behaviours and specific adaptations to the environments of their origin: the boreal Meganyctiphanes norvegica and subtropical Nematoscelis megalops appear more carnivorous and have significantly lower mean lipid contents (29 and 10 %, respectively) and a different energy storage pattern (triacylglycerols and polar lipids, respectively) than the arcto-boreal Thysanoessa inermis, which consists of up to 54 % of lipids mainly stored as wax esters (>40 %). These differences may have significant implications for the rapidly changing marine food web of Kongsfjord—especially for higher trophic levels relying on the nutritional input of animal lipids.     

The molecular species of phospholipids of the cold-water soft coral <Emphasis Type="Italic">Gersemia rubiformis</Emphasis> (Ehrenberg, 1834) (Alcyonacea,Nephtheidae)

The chemical structures and contents of 68 molecular species of ethanolamine glycerophospholipids (PE), choline glycerophospholipids (PC), serine glycerophospholipids (PS), and inositol glycerophospholipids (PI) were determined in the asymbiotic soft coral Gercemia rubiformis (Ehrenberg, 1834) from the Sea of Okhotsk by the method of tandem high-resolution mass spectrometry. The major molecular species were 16:1e/20:4 PE, 16:0e/20:4 PC, 20:1/24:5 PS, and 16:0/24:5 PI. This study showed a significant similarity of the polar lipidomes of G. rubiformis and tropical species of alcyonarians with symbiotic microalgae and revealed the basic characteristic of the polar lipidome of these alcyonarians. It was found that the 24:5n-6 and 24:6n-3 acids (chemotaxonomic markers of soft corals) concentrate in the acyl groups of the molecular species of PS and PI, which can be used as molecular lipid markers in the study of the symbiotic and trophic relationships of soft corals.     

Distribution and diet of demersal Arctic Cod, <Emphasis Type="Italic">Boreogadus saida</Emphasis>, in relation to habitat characteristics in the Canadian Beaufort Sea

Arctic Cod (Boreogadus saida) occur throughout the circumpolar north; however, their distributions at localized scales are not well understood. The seasonal habitat associations and diet preferences across life-history stages of this keystone species are also poorly known, thereby impeding effective regulatory efforts in support of conservation objectives. The distribution of Arctic Cod in the Canadian Beaufort Sea was assessed using bottom trawling in shelf and slope habitats between 20 and 1000 m depths. Highest catch biomasses occurred at 350 and 500 m depth slope stations, coinciding with >0 °C temperatures in the Pacific–Atlantic thermohalocline and Atlantic water mass. Calanus glacialis, Calanus hyperboreus, Themisto libellula, and Themisto abyssorum were identified as key prey species in the diet of Arctic Cod, comprising approximately 86 % of total biomass in guts. Hierarchical cluster analysis with a SIMPROF test identified five statistically significant (p < 0.05) diet groups among gut samples. Arctic Cod shifted from a primarily Calanus diet at shelf stations (<200 m depth) to a Themisto diet in slope habitats (>200 m depth) coinciding with an associated increase in fish standard length with depth. Smaller Arctic Cod fed primarily on Calanus copepods and larger Arctic Cod fed primarily on the larger Themisto species. The habitat and diet associations presented here will inform knowledge of structural and functional relationships in Arctic marine ecosystems, aid in mitigation and conservation efforts, and will enhance our ability to predict the effects of climate change on the local spatial and depth associations of this pivotal marine fish.     

Phospholipid and Fatty Acid Composition of Phosphatidylcholine and Phosphatidylethanolamine in the Black Plaice <Emphasis Type="Italic">Pleuronectes obscura</Emphasis> during Thermoadaptation

The phospholipid (PL) and fatty acid (FA) composition of major membrane lipid constituents, phosphatidylcholine (PC) and phosphatidylethanolamine (PE), as well as the cholesterol/phospholipid (CL/PL) ratio were assayed in the muscles, gills and liver of the black plaice Pleuronectes (Liopsetta) obscura at different ambient temperatures (18, 9 and 0°C). PL and CL were shown to be actively involved in adaptation of the fish to changes in the seawater temperature. As temperature declines, the monounsaturated FA (MUFA) level increases while the polyunsaturated FA (PUFA) fraction in gills and liver PC and PE, on the contrary, decreases, resulting in diminished functional activity of the fish. However, in muscles this correlation is lacking. The PC and PE composition was shown to be organ- and ambient temperature-dependent. Major PC forms are saturated FA (SFA)/PUFA and MUFA/PUFA composed of a relatively small number of major molecular species. A temperature drop results in an increased SFA/PUFA level and decreased MUFA/PUFA and PUFA/PUFA levels in muscles and gills, and this may promote a drop in the viscosity of the outer lipid monolayer of membranes and in their functional activity. In contrast to PC, the PE composition in all organs tested is characterized by a decrease in the SFA/ PUFA level and an increase in MUFA/PUFA and PUFA/PUFA levels. Such changes promote the retention of functional activity of the inner lipid monolayer of membranes and are not synchronized with rearrangements in their outer monolayer. Due to intermolecular transfer of acyl radicals at a constancy of their composition, functional rearrangement of the lipid matrix appears to be achieved through changes in the membrane viscosity. Our data support the idea that different adaptation strategies in fish are driven by certain sets of PL molecular species.     

Intra-and interspecific variability of fatty acid composition of soft corals

The intra-and interspecific variability of fatty acid (FA) composition of soft corals was examined in the tropical alcyonarian Sarcophyton sp., tropical gorgonian Euplexaura erecta, and boreal alcyonarian Gersemia rubiformis. Characteristic significant differences in the FA composition were found between these species belonging to different taxonomic groups and habitats. We assume that the FA groups 14: 0 + 16: 0 + 18: 3n-6, 16: 2 + 20: 4n-6 + 24: 5n-6, and 18: 1n-7 + 20: 1n-7 + 20: 5n-3 + 24: 6n-3 are characteristic of Sarcophyton sp., E. erecta, and G. rubiformis respectively. There were no significant differences (p > 0.05) between the three soft coral species in the content of oleic, linoleic, and docosahexaenoic acids. The relative content of more than 45% of individual FA did not significantly differ (p > 0.05) between the pairs of species, i.e., intraspecific variations exceeded interspecific ones. The reasons for intraspecific variability of soft coral FA composition are discussed. Control of this variability is needed when using individual FA as chemotaxonomic and food markers.     

Fatty acid composition of fish species with different feeding habits from an Arctic Lake

We compared the composition and content of fatty acids (FAs) in fish with different feeding habits (sardine (least) cisco Coregonus sardinella, goggle-eyed charr (pucheglazka) form of Salvelinus alpinus complex, humpback whitefish Coregonus pidschian, broad whitefish Coregonus nasus, boganid charr Salvelinus boganidae, and northern pike Esox lucius from an Arctic Lake. Feeding habits of the studied fish (planktivore, benthivore, or piscivore) significantly affected the composition of biomarker fatty acids and the ratio of stable isotopes of carbon and nitrogen in their biomass. The hypothesis on a higher content of eicosapentaenoic and docosahexaenoic acids in the fish of higher trophic level (piscivores) when compared within the same taxonomic group (order Salmoniformes) was confirmed.     

Fatty acid composition and lipid content in the copepod <Emphasis Type="Italic">Limnocalanus macrurus</Emphasis> during summer in the southern Bothnian Sea

The lipid reserves and occurrence of the cold-stenothermic, omnivorous copepod Limnocalanus macrurus were studied in the Bothnian Sea (northern Baltic Sea) during spring and summer 2013–2014 with a special emphasis on the fatty acid composition of adults and their potential food. The individual total wax ester (WE) content, determined from the size of oil sacs in the prosoma, ranged on average from 1.3 to 2.6 µg, and showed a decreasing trend towards September. Lipids were dominated by fatty acids 16:0, 18:1(n-9), 18:2(n-6), 20:5(n-3) and 22:6(n-6), forming 56–61% of total fatty acids in June–September. Decreasing abundance of adults and reduction of the lipid storage implied that during summer adults suffered from starvation and, as a result, became eliminated from the population. The lipid content and dietary fatty acid markers suggested that in May, adult L. macrurus utilized the phytoplankton bloom, consisting mainly of diatoms and dinoflagellates, but later, during July–September, consumed either algae or heterotrophic organisms sinking from upper water layers or crustaceans inhabiting the same deeper water layers as L. macrurus. In the face of the climate change, the rising temperatures may force L. macrurus permanently to deeper water levels. If also the food resources are limited, we conclude that the summer season may act as a bottleneck limiting the propagation of L. macrurus and having implications further along the food web.     

Changes in the fatty acid composition of symbiotic dinoflagellates from the hermatypic coral <Emphasis Type="Italic">Echinopora lamellosa</Emphasis> during adaptation to the irradiance level

The composition of fatty acids (FAs) of symbiotic dinoflagellates isolated from the hermatypic coral Echinoporal lamellosa adapted to the irradiance of 95, 30, 8, and 2% PAR was studied. Polar lipids and triacylglycerols (TAG) differed between them in FA composition. Polar lipids were enriched in unsaturated FAs, whereas TAG, in saturated FAs. Light exerted a substantial influence on the FA composition in both polar lipids and TAG. The elevation of irradiance resulted in the accumulation of 16:0 acid in both lipid groups and 16:1(n-7) acid in TAG. It seems likely that de novo synthesis of 16:0 acid occurred actively in the cells of symbiotic dinoflagellates in high light. Since these processes are energy-consuming ones, they utilize excessive energy. When light intensity declined, 18:4(n-3) and 20:5(n-3) acids accumulated in polar lipids, which was accompanied by the increase in the content of chlorophyll a in the cells of zooxanthellae, whereas the levels of 22:6(n-3) and 20:4(n-6) acids reduced. Although the relative content of particular FAs varied substantially in dependence of irradiance, the balance between the sum of saturated and unsaturated FAs changed insignificantly. We concluded that the role of photoadaptation could not be limited only to changes in the degree of lipid unsaturation and membrane fluidity. It is supposed that light-induced changes in the FA composition reflect the interrelation between photosynthesis and FA biosynthesis.     

The thermotropic behavior and fatty radical composition of major phospholipids of the tanner crab <Emphasis Type="Italic">Chionoecetes bairdi</Emphasis> Rathbun, 1924

This study examines the fatty radical (FR) composition and heat-induced crystalline to liquidcrystalline phase transitions of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) from the gills, hepatopancreas, gonads, and muscle of the tanner crab Chionoecetes bairdi, which was collected in the summer at a near-bottom water temperature of 2.8°C. The location of the PC and PE thermograms below 2.8°C indicates the functionally optimal liquid crystalline state of the membrane lipid matrix. The proximity of the thermogram profiles of PC and PE from the different organs and tissues of C. bairdi and significant overlapping of the temperature areas of transitions (symbatic behavior) correlate with a similar composition of major FR and their total parameters in PC and PE. The obtained data point to the effective adaptation of the bairdi crab to low water temperatures and to the need for adaptive changes in the FR composition or change of habitat with increasing temperature. The thermotropic behavior of muscle PC, in which the greater part of the thermogram is in the temperature range from 2.8 to 32°C, suggests a potential for the tanner crab to adapt to increased temperatures.     

The composition of fatty acids in the endosperm and embryo lipids of <Emphasis Type="Italic">Pinus sibirica</Emphasis> and <Emphasis Type="Italic">P. sylvestris</Emphasis> seeds

The fatty acid (FA) composition of storage lipids in the seed endosperms and embryos of two pine species, Pinus sibirica and P. sylvestris, and possible biosynthetic pathways of these acids were studied by the GLC method. Linoleic acid predominated in the embryo and endosperm lipids of both P. sibirica (43.5 and 42.6%) and P. sylvestris (44.8 and 46.8%); this was evidently determined by a high expression of the gene encoding stearoyl-Δ9 acyl-lipid desaturase and the fad2 gene encoding microsomal ω6 acyl-lipid desaturase. P. sibirica lipids of the embryo and endosperm contained more oleic acid (22.0 and 24.0%, respectively) than corresponding P. sylvestris lipids (18.7 and 14%). Storage lipids of conifer seeds contain Δ5-unsaturated FAs: taxoleic (18:2Δ5,9), ephedrenic (18:2Δ5,11), pinoleenic (18:3Δ5,9,12), skiadonic (18:3Δ5,11, 14), and coniferonic (18:4Δ5,9,12,15). In the endosperm and embryos of P. sylvestris, the content of pinolenic acid was higher (22.1 and 19.6%) than in P. sibirica seeds (19.1 and 18.6%).     

The combined effects of blue light and dilution rate on lipid class and fatty acid composition of <Emphasis Type="Italic">Tisochrysis lutea</Emphasis>

The lipid class and the fatty acid compositions of microalgae highly influence bivalve larval and post-larval development. Light is an essential environmental factor for microalgal culture, and quantity and quality of light may induce changes in the biochemical composition of the algae. The objective of this study was to investigate the effect of light spectrum (blue vs. white light) on lipid class and fatty acid compositions of Tisochrysis lutea cultured in a chemostat. Two different dilution rates (D) were assayed for each light spectrum: 0.2 and 0.7 day^?1. Triacylglycerol (TAG), sterol, and hydrocarbon (HC) content increased sharply at low D. The proportion of alkenones was significantly reduced under blue light. Polyunsaturated fatty acids (PUFA), and particularly n-3 PUFA, content in phospholipids (PL) increased under blue light compared to white light at low D. Thus, blue light raised 22:6(n-3) levels in total lipids of T. lutea at low D. The cultivation of T. lutea in a chemostat at low D under blue light may improve nutritional value as feed for bivalve larvae by modifying the PUFA profile, especially increasing 22:6(n-3).     

The fatty-acid composition and nutrition of deep-sea holothurians from the Sea of Okhotsk

The results of a comparative study of the fatty-acid composition in eight species of holothurians that were collected in the Sea of Okhotsk in the area of the Kuril Islands (depths of 90–560 m) are presented. It is shown that interspecific differences in the fatty-acid compositions of the holothurians were consistent with the isotope composition (δ¹³C and δ¹⁵N) and the structural features of the tentacles and the lifestyle of holothurians, as indicators of trophic resources used by these holothurians. According to the results of the cluster analysis, the holothurians were divided into three groups. The first group included suspension-feeding dendrochirotides Eupentacta pusilla and Pseudocnus fallax with a high content of the fatty acid 20:5(n-3), which is a marker of diatoms, and with the δ¹⁵N values that are typical of consumers of suspended organic matter. The second group consisted of the dendrochirotides Psolus chitonoides and Psolidium sp. with a much lower content of 20:5 (n-3) and higher contents of 20:4 (n-6) and 22:6 (n-3), as well as high values of δ¹⁵N, which are typical of surface deposit-feeders. The third group consisted of surface and subsurface depositfeeders, Chiridota sp., Molpadia orientalis, Pseudostichopus mollis, and Synallactes nozawai. Very high contents of 20: 4 (n-6) and 21: 4 (n-7) were typical of the third group and the highest values of δ¹⁵N, indicating feeding on repeatedly recycled organic matter.     

Seasonal variations of the photosynthetic activity and pigment concentrations in different reproductive phases of <Emphasis Type="Italic">Gigartina skottsbergii</Emphasis> (Rhodophyta,Gigartinales) in the Magellan region,sub-Antarctic Chile

Seasonal environmental changes may significantly influence macroalgal diversity and biomass. Cryptogam species richness increases towards the poles, especially in sub-Antarctic environments. Yet, subpolar seaweed biodiversity and ecophysiology remain understudied even though it is essential for the management and sustainability of endemic species of significant economic interest (e.g., Gigartina skottsbergii). We evaluate the seasonality and ecophysiology of the different life phases of the rhodophyte G. skottsbergii by analyzing variation in fluorescence yield and photosynthetic pigment composition. There were significant seasonal differences in maximum relative electron transport rate (rETR_max) between gametophyte and tetrasporophyte phase, and between reproductive and vegetative specimens. Photosynthetic efficiency (α) was not significantly different between reproductive states of G. skottsbergii. We found significant differences in mean concentrations of allophycocyanin (APC), phycocyanin (PC), and chlorophyll a (Chl a) between gametophyte and tetrasporophyte phases. Results obtained provide new insight into seasonal acclimation patterns of an ecologically important species, which can be used for the design of appropriate management and cultivation strategies of G. skottsbergii towards the restoration of natural populations in fragile, subpolar regions where some of the last, relatively undisturbed communities of G. skottsbergii still remain.     

Sporangiospore lipids of the mycelial fungus <Emphasis Type="Italic">Mucor ramannianus</Emphasis> incapable of dimorphic growth

Members of the species Mucor ramannianus are believed to be monomorphic. They grow only as a mycelium and are not capable of growth as budding cells, i.e., of dimorphic growth. In our study, we investigated the lipid composition of M. ramannianus sporangiospores, which retained the capability of initiating mycelial growth in the course of long-term cultivation of the spore-forming mycelium. It was demonstrated that sporangiospores contained high concentrations of triacylglycerides (TAG) in their reserve lipids and high concentrations of phosphatidylcholine (PC) in their membrane lipids; low concentrations of methylated ergosterol precursors were detected among sterols. On the basis of the data presented, in order to evaluate the potential of mucor fungi for yeastlike growth, it has been suggested to analyze the qualitative and quantitative characteristics of their sporangiospore lipids and to consider the following criteria as the criteria of sporangiospore capacity for giving rise to yeastlike growth upon spore germination: (1) the phosphatidylethanolamine/phosphatidylcholine (PE/PC) ratio; (2) the level of ergosterol and the ratio between the methylated and demethylated sterols; as well as (3) the ratios between phospholipids and glycolipids (PL/GL) and (4) between etherified and free sterols (ES/FS).     

High level of tetracosapolyenoic fatty acids in the cold-water mollusk <Emphasis Type="Italic">Tochuina</Emphasis><Emphasis Type="Italic">tetraquetra</Emphasis> is a result of the nudibranch feeding on soft corals

Fatty acid (FA) markers are used to trace predator–prey relationships in the marine environment. Soft corals contain tetracosapolyenoic acids (TPA), namely 24:5n-6 and 24:6n-3, which are considered as octocoral FA markers. The nudibranch mollusks are known to feed on soft corals. To check whether TPA are transferred from soft corals to nudibranch mollusks during their nutrition, we determined and compared FA compositions of total lipids of Tochuina tetraquetra and soft corals (Acanella sp., Anthomastus rylovi, Gersemia fruticosa, and Paragorgia arborea) collected together near the Kuril Islands (the depths of 80–550 m). FA compositions of T. tetraquetra, Acanella sp. and A. rylovi were described for the first time. In Acanella sp., G. fruticosa, A. rylovi, and P. arborea, the average contents of TPA were 6.5, 13.4, 5.9, and 12.0 % of total FAs, whereas the 24:5n-6/24:6n-3 ratio was 1.0, 1.4, 5.4, and 2.6, respectively. The high level of TPA (21.7 %) found in T. tetraquetra indicates that 24:5n-6 and 24:6n-3 are transferred from soft corals to the mollusks during their feeding and accumulated in mollusk tissues. The most possible feed source of the mollusk is suggested to be G. fruticosa and/or Acanella sp., because the 24:5n-6/24:6n-3 ratios in T. tetraquetra and these soft corals were similar. Thus, the TPA could be used as FA markers to estimate a proportion of soft corals in feeding of cold-water nudibranch mollusks.     

Fungicidal activity of cellobiose lipids from culture broth of yeast <Emphasis Type="Italic">Cryptococcus humicola</Emphasis> and <Emphasis Type="Italic">Pseudozyma fusiformata</Emphasis>

Cellobiose lipids of yeast fungi Cryptococcus huminola and Pseudozyma fusiformata have similar fungicidal activities against different yeast, including pathogenic Cryptococcus and Candida species. Basidiomycetic yeast reveals maximum sensitivity to these preparations; e.g., cells of cryptococcus Filobasidiella neoformans almost completely die after 30-min incubation in a glycolipid solution at a concentration of 0.02 mg/ml. The same effect toward ascomycetous yeast, including pathogenic Candida species, is achieved only at five to eight times higher concentrations of glycolipids. The cellobiose lipid from P. fusiformata, which, unlike glycolipid from Cr. humicola, has hydroxycaproic acid residue as O-subtituent of cellobiose and additional 15-hydroxy group in aglycone, inhibits the growth of the studied mycelial fungi more efficiently than the cellobiose lipid from Cr. humicola.     

Trophic variability of Arctic fishes in the Canadian Beaufort Sea: a fatty acids and stable isotopes approach

Trophic ecology of most demersal Arctic fishes remains one of the major knowledge gaps for understanding food web dynamics and connectivity among ecosystems. In this study, fatty acids (FA) and stable isotopes (SI) were used to study the feeding ecology of seven species (n = 106) of the most abundant benthic fishes (eelpouts, sculpins and agonids) in the Canadian Beaufort Sea from shallow (20–75 m), slope (200–350 m) and deep (500–1000 m) habitats. Both FA and SI results revealed among- and within-species variability in diet composition. Correspondence analysis of FA signatures identified high within-species variability in diet, resulting in high overlap among species. Calanus-derived FA were present in all species (Calanus markers up to 13 % of total FA) and were particularly important in Ribbed Sculpin, Adolf’s and Longear Eelpout collected in deep habitats, suggesting a strong contribution of pelagic-derived FA to benthic fish communities. Incorporation of this signal in the benthos may result from either direct consumption of deep overwintering copepods (i.e., off-bottom feeding) or through detrital accumulation in benthic invertebrate prey. Mean SI values differed among species and indicated that a large range of trophic positions (δ¹⁵N varied from 14.09 to 17.71 ‰ for Canadian Eelpout and Adolf’s Eelpout, respectively) and carbon dietary sources are preyed upon (δ¹³C range from ?21.13 to ?23.85 ‰ for Longear Eelpout and Ribbed Sculpin, respectively). SI analyses suggested that most species examined were low- to mid-trophic generalist benthic carnivores, with the exception of Ribbed Sculpin, which was a low-trophic pelagic predator.     

The effect of temperature on growth and lipid and fatty acid composition on marine microalgae used for biodiesel production

Cultivation temperature is one of the major factors affecting the growth and lipid accumulation of microalgae. In this study, the effects of temperature on the growth, lipid content, fatty acid composition and biodiesel properties of the marine microalgae Chaetoceros sp. FIKU035, Tetraselmis suecica FIKU032 and Nannochloropsis sp. FIKU036 were investigated. These species were cultured at different temperatures (25, 30, 35 and 40 °C). The results showed that the specific growth rate, biomass and lipid content of all microalgae decreased with increasing temperature. With regards to fatty acids, the presence of saturated fatty acids (SFAs) in T. suecica FIKU032 and Nannochloropsis sp. FIKU036 decreased with increasing temperature, in contrast with polyunsaturated fatty acids (PUFAs). Moreover, Chaetoceros sp. FIKU035 was the only species that could grow at 40 °C. The highest lipid productivity was observed in Chaetoceros sp. FIKU035 when cultivated at 25 °C (66.73 ± 1.34 mg L^?1 day^?1) and 30 °C (61.35 ± 2.89 mg L^?1 day^?1). Moreover, the biodiesel properties (cetane number, cold filter plugging point, kinematic viscosity and density) of the lipids obtained from this species were in accordance with biodiesel standards. This study indicated that Chaetoceros sp. FIKU035 can be considered as a suitable species for biodiesel production in outdoor cultivation.     

Food resource partitioning of the <Emphasis Type="Italic">Mustelus lunulatus</Emphasis> and <Emphasis Type="Italic">Mustelus henlei</Emphasis> (Elasmobranchii: Carcharhiniformes)

The feeding habits and trophic ecology of Mustelus lunulatus and Mustelus henlei in the central coast of the Colombian Pacific were evaluated and compared to determine whether there was trophic niche overlap or resource partitioning between these two sympatric shark species. A total of 59 prey items were identified and grouped into 10 taxonomic categories. Mustelus lunulatus fed in large proportion on Stomatopoda and Brachyura, whereas M. henlei fed almost exclusively on Teleostei. Dendrobranchiata, Cephalopoda, Anomura and Polychaeta complemented the diets of both species. There were significant differences in diet between the two species, and there was an ontogenetic diet shift in Mustelus lunulatus, with Stomatopoda being the main prey item of juveniles and Brachyura the main prey item of adults. Dietary overlap (by sex and size) was low between species, but it was high for each species, with significant overlap between juveniles and adults of M. lunulatus and M. henlei, and between males and females of M. henlei. There were differences in the trophic levels of the species, sexes and sizes. This study suggests there is food resource partitioning, and differing ecological function of the two Mustelus species in the food web of the study area.