Temporal variation in the specific dynamic action of juvenile New Zealand rock lobsters, Jasus edwardsii

To enhance the on-growing of Jasus edwardsii in culture, it is important to understand the feeding physiology of juveniles. In crustaceans, there is a loss of energy and an increase in oxygen consumption (specific dynamic action or SDA) associated with feeding. The present research measured the SDA of juvenile J. edwardsii fed either in the morning or at night held at 15 degrees C. Closed box respirometry was used to measure oxygen consumption (MO(2)) and ammonia excretion in juvenile lobsters. Juveniles exhibited a nocturnal rhythm in both MO(2) and ammonia excretion. The factorial rise in MO(2) (1.58+/-0.03 times) for lobsters fed in the morning was significantly less than lobsters fed at night (1.80+/-0.01 times). Lobsters fed in the morning had a significantly shorter SDA (30+/-1.2 h) response compared to lobsters fed at night (36+/-1 h). Energy loss as a result of digestion was less for lobsters fed in the morning. Therefore, if juvenile J. edwardsii are fed in the morning, they could optimise the energy content of the meal and this could result in increased growth.     

How diet influences energy partitioning in the regular echinoid Psammechinus miliaris; constructing an energy budget

The effect of diet (made from either animal or plant material) on the partitioning of energy in small (8-16 mm test diameter (td)) and large (29-37 mm td) Psammechinus miliaris was examined. Diet significantly affected ingestion, digestion and growth of both size groups. Assimilation rates of the different types of feed varied and they supported differential development of the body parts. Urchins fed on an algal diet showed poorer absorption efficiency, assimilation, gonadal and somatic growth than individuals fed on an artificial sea urchin diet (mixed plant and animal material) or on the animal based diets. Small urchins fed on a diet of salmon food utilised proteins as the primary energy source rather than carbohydrates or lipids as indicated by low O/N atomic ratios, and salmon diet promoted a higher energetic investment in reproductive development in both size classes. A negative energy balance resulted when large urchins were fed on the algal diet. Energy losses due to ammonia excretion were negligible and the metabolic losses of assimilated energy, measured as oxygen consumption, were between 0.2% and 1.5% with the different diets. A diet made of mussel flesh stimulated ingestion, gave the highest assimilation rates and best overall growth performance. Such detailed information should assist in the design of diets for the cultivation of sea urchins.     

Growth, metabolic rate, and digestive enzyme activity in the white shrimp Litopenaeus setiferus early postlarvae fed different diets

Growth rate, soluble-protein content, oxygen consumption, ammonia excretion, and digestive-enzyme activity were studied in Litopenaeus setiferus early postlarvae under four feeding regimens that included combinations of freshly hatched Artemia nauplii, microparticulate commercial diet, and algae. Growth and of postlarvae fed a mixed diet were significantly higher. Artificial diet used alone caused the lowest growth, lowest soluble-protein content, higher ammonia excretion, lowest O:N ratio, and higher proteolytic and amylase activities. The artificial diet stimulated proteolytic activity and ammonia excretion of postlarvae, apparently in response to some deficiency in protein composition of the diet. Based on results in growth, soluble-protein content, enzymatic activity, and metabolic substrate, we determined that partial substitution of Artemia nauplii by artificial diet, with or without addition of algae when rearing early postlarval stages, will benefit the growth and nutritional state of L. setiferus postlarvae.     

Experimental studies on some trophic relationships in juvenile pike, Esox lucius L.

A postprandial increase in ammonia nitrogen excretion and oxygen consumption rates was observed in juvenile pike fed a natural diet or an artificial dry diet. Specific growth rate of natural diet fed pike (2.4%) was lower than that of pike fed the artificial diet (3.1%). Fifty per cent of ingesta was evacuated within 5–6 h in pike of 25 mg body weight and 9–10 h in those weighing 150mg. Daily nitrogen excretion rates were related to body weight. Respiratory quotient and energy retention efficiency were affected by the nature of the diet ingested by pike. Parameters of the energy balance (losses, retention, increment due to feeding) were related to energy intake.     

Effects of mannan oligosaccharide dietary supplementation on performances of the tropical spiny lobsters juvenile (Panulirus ornatus,Fabricius 1798)

The effects of dietary mannan oligosaccharide (MOS) (Bio-Mos^®, Alltech, USA) on the growth, survival, physiology, bacteria and morphology of the gut and immune response to bacterial infection of tropical rock lobsters (Panulirus ornatus) juvenile were investigated. Dietary inclusion level of MOS at 0.4% was tested against the control diet (trash fish) without MOS inclusion. At the end of 56 days of rearing period, a challenged test was also conducted to evaluate the bacterial infection resistant ability of the lobsters fed the two diets. Lobster juvenile fed MOS diet attained 2.86 ± 0.07 g of total weigh and 66.67 ± 4.76% survival rate which were higher (P < 0.05) than the lobsters fed control diet (2.35 ± 0.14 g total weight and 54.76 ± 2.38% survival rate, respectively) thus providing the higher (P < 0.05) specific growth rate (SGR) and average weekly gain (AWG) of lobsters fed MOS diet. Physiological condition indicators such as wet tail muscle index (Tw/B), wet hepatosomatic index (Hiw) and dry tail muscle index (Td/B) of the lobsters fed MOS supplemented diet were higher (P < 0.05) than that of the lobsters fed the control diet. Bacteria in the gut (both total aerobic and Vibrio spp.) and gut's absorption surface indicated by the internal perimeter/external perimeter ratio were also higher (P < 0.05) when the lobsters were fed MOS diet. Lobsters fed MOS diet were in better immune condition showed by higher THC and GC, and lower bacteraemia. Survival, THC, GC were not different among the lobsters fed either MOS or control diet after 3 days of bacterial infection while bacteraemia was lower in the lobsters fed MOS diet. After 7 days of bacterial infection the lobsters fed MOS diet showed higher survival, THC, GC and lower bacteraemia than the lobsters fed the control diet. The experimental trial demonstrated the ability of MOS to improve the growth performance, survival, physiological condition, gut health and immune responses of tropical spiny lobsters juveniles.     

Agonistic interactions between the invasive green crab, Carcinus maenas (Linnaeus) and juvenile American lobster, Homarus americanus (Milne Edwards)

Invasive organisms have the potential for competition with native organisms. In the Southern Gulf of St. Lawrence, juvenile American lobsters have a potential spatial overlap with adult green crabs. Crustaceans use agonistic behaviour to settle disputes, with the larger organism often winning contests for limited resources such as food and shelter. Two experiments were carried out using adult green crabs (53-76 mm carapace width) and juvenile American lobsters (28-57 mm carapace length). The first experiment used a limited food resource. We found that green crabs were the first to the food in all trials, fed in significantly more trials than lobsters and spent a significantly greater proportion of time with the food. The lobsters were only able to displace the green crabs from the food in 2 of 65 attempts. The second experiment was designed to examine shelter competition; unexpectedly some predation by green crabs on lobsters occurred, which allowed us to test hypotheses about how relative size and shelter use affect predation. Green crabs captured and consumed juvenile lobsters in 6 of 11 trials. The lobsters that survived spent significantly more time in shelter. There was no clear relationship between shelter use and size of lobster. The lobsters that were larger in relation to the green crabs suffered a higher rate of predation, which we believe was due to more conspicuous activity and less use of shelter. It appears that green crabs have the potential to negatively impact native juvenile lobster.     

Some physiological and biochemical considerations of larval development in the American lobster,Homarus Americanus Milne Edwards

The weight-specific respiration rates of fed and starved lobsters and the ammonia excretion rates of fed lobsters increased with each larval stage (I through IV) and decreased with the first postlarval stage (V). The rate of change in metabolic rates was greater than the rate of change of body size of the larval stages, indicating an increased energy demand of the later larval stages. There was no significant difference in the O: N ratio for the first three larval stages but a reduction was observed in stage IV and V lobsters, reflecting an increased dependence on protein catabolism for energy.Protein was the principal biochemical constituent of all lobster stages. Significant decreases in lipid content and increases in ash and chitin content of the last larval (IV) and first postlarval (V) stages were detected.     

Exercise effects on chromium excretion of trained and untrained men consuming a constant diet

Chromium excretion of eight trained and five sedentary men was determined on rest days and after exercise to exhaustion at 90% of maximum O2 consumption (VO2max) to determine if degree of physical fitness affects urinary Cr losses. Subjects were fed a constant daily diet containing approximately 9 micrograms Cr/1,000 kcal. VO2max of the trained runners was in the good or above range based on their age and that of the sedentary subjects was average or below. While consuming the control diet, basal urinary Cr excretion of subjects who exercise regularly was significantly lower than that of the sedentary control subjects, 0.09 +/- 0.01 and 0.21 +/- 0.03 microgram/day (mean +/- SE), respectively. When subjects consumed self-chosen diets, basal urinary Cr excretion of the trained subjects was also significantly lower than that of the untrained subjects. Daily urinary Cr excretion of trained subjects was significantly higher on the day of a single exercise bout at 90% VO2max compared with nonexercise days, 0.12 +/- 0.02 and 0.09 +/- 0.01 microgram/day, respectively. Urinary Cr excretion of sedentary subjects was not altered after controlled exercise. These data demonstrate that basal urinary Cr excretion and excretion in response to exercise are related to VO2max and therefore degree of physical fitness.     

Effect of feeding and fasting on excess post-exercise oxygen consumption in juvenile southern catfish (Silurus meridionalis Chen)

The impact of feeding (fed to satiation, 13.85% body mass) on excess post-exercise oxygen consumption (EPOC, chasing for 2.5 min) was investigated in juvenile southern catfish (Silurus meridionalis Chen) (38.62-57.55 g) at 25. Cutlets of freshly killed loach species without viscera, head and tail were used as the test meal, and oxygen consumption (VO(2)) was adjusted to a standard body mass of 1 kg using a mass exponent of 0.75. Resting VO(2) increased significantly above fasting levels (49.89 versus 148.25 mg O(2) h(-)(1)) in 12 h postprandial catfish. VO(2) and ventilation frequency (V(f)) both increased immediately after exhaustive exercise and slowly returned to pre-exercise values in all experimental groups. The times taken for post-exercise VO(2) to return to the pre-exercise value were 20, 25 and 30 min in 12 h, 60 h and 120 h postprandial catfish, respectively. Peak VO(2) levels were 257.36+/-6.06, 219.32+/-6.32 and 200.91+/-5.50 mg O(2) h(-1) in 12 h, 60 h and 120 h postprandial catfish and EPOC values were 13.85+/-4.50, 27.24+/-3.15 and 41.91+/-3.02 mg O(2) in 12 h, 60 h and 120 h postprandial southern catfish, respectively. There were significant differences in both EPOC and peak VO(2) during the post-exercise recovery process among three experimental groups (p<0.05). These results showed that: (1) neither digestive nor exhaustive exercise could elicit maximal VO(2) in southern catfish, (2) both the digestive process and exercise (also the post-exercise recovery process) were curtailed under postprandial exercise, (3) the change of V(f) was smaller than that of VO(2) during the exhaustive exercise recovery process, (4) for a similar increment in VO(2), the change in V(f) was larger during the post-exercise process than during the digestive process.     

High fat diet induced oxidative DNA damage estimated by 8-oxo-7,8-dihydro-2-deoxyguanosine excretion in rats

The role of dietary fats and energy in carcinogenesis has been partly related to oxidative damage to DNA. We have investigated the effect of dietary fat content and saturation on the urinary excretion of 8-oxo-7,8dihydro-2'-deoxyguanosine (8-oxodG) in male and female rats. Groups of Fischer F344 rats (n = 6-10) were fed control chow (3.4% fat) or diets containing 21.8% corn oil or 19.8% coconut oil + 2% corn oil for 12-15 weeks. At the end of the diet intervention period 24h urine was collected for determination of 8-oxodG by HPLC. In the male groups fed control, corn oil and coconut oil diet the excretion of 8-oxodG was 403+/-150, 932+/-198 and 954+/-367pmol/kg 24 h, respectively (p < 0.05). In the female groups fed control and corn oil diet the excretion of 8-oxodG was 752+/-80 and 2206+/-282 pmol/kg 24 h, respectively (p < 0.05). Calculated per whole animal the excretion was 137+/-51, 324+/-70 and 328+/-128 pmol/24 h in the control, corn and coconut oil male groups and 156+/-21 and 464+/-56 pmol/24 h in the control and corn oil female groups, respectively ( p < 0.05). Thus, per animal or per consumed energy there was much less difference in 8-oxodG excretion between the corresponding male and female groups and only significant difference between the high fat groups. There was a close correlation (r = 0.7; p < 0.05) between 8-oxodG excretion and the energy intake. The present study suggests that a high fat diet increases oxidative DNA modification substantially irrespective of the saturation level of the fat. Energy intake appears to be the major determinant of the rate of modification.     

Growth hormone-mediated breakdown of body fat: insulin and leptin responses to GH are modulated by diet composition and caloric intake in old rats.

This work was performed to elucidate whether growth hormone (GH)-mediated loss of adipose tissue and responses in plasma insulin and leptin are modulated by diet composition. 12-month-old rats were first fed a high-fat (HF) diet or a low-fat (LF) diet for 14 weeks. After that, GH or saline was administered to rat groups that were maintained on either HF or LF diets or that were switched from the HF to the LF diet. All 6 groups had free access to food. One additional saline group was pair-fed with the GH group that was switched from the HF to the LF diet. The caloric consumption of this latter group was also translated to yet another GH group receiving restricted amounts of the HF diet. GH was given in a total dose of 4 mg/kg/d for three weeks. After sacrifice, blood was collected and tissues were excised. In groups injected with saline, the weight of excised adipose tissue was 60 +/- 4.7, 41 +/- 3.8 and 50 +/- 4.5 g in animals that continued with the HF diet, LF diet, or that were switched from HF to LF, respectively. Corresponding figures after GH treatment were significantly (p < 0.05) decreased to 38 +/- 2.7, 30 +/- 2.3, and 31 +/- 2.7 g, respectively. Pair-feeding had no effect, whereas only 26 +/- 3.0 g of adipose tissue was retrieved in rats fed restricted amounts of HF diet while receiving GH. In this group, plasma insulin and leptin were also significantly (p < 0.05) depressed compared with other GH groups, especially to the group fed the unrestricted HF diet (203 +/- 35 vs. 1345 +/- 160 pmol/l and 9.3 +/- 1.2 vs. 31 +/- 4.4 micro g/l). In conclusion, this study shows that GH mediates breakdown of adipose tissue under a variety of dietary conditions, and that induction of hyperinsulinemia can be prevented if GH treatment is combined with restricted feeding of a diet which is relatively low in carbohydrates and rich in fat. This will also promote a fall of plasma leptin.     

Enhancement of juvenile Caribbean spiny lobsters: an evaluation of changes in multiple response variables with the addition of large artificial shelters

Shortage of natural crevice shelters may produce population bottlenecks in juvenile Caribbean spiny lobsters (Panulirus argus), a socially gregarious species. We conducted a field experiment to test enhancement of a local population of juvenile P. argus with the addition of artificial shelters (“casitas”) that mimic large crevices (1.1 m² in surface area and 3.8 cm in height). Changes in density and biomass of juvenile lobsters 15–50 mm carapace length (CL) were assessed with a multiple before-after control-impact (MBACI) analysis. Separate analyses were also conducted on small (15–35 mm CL) and large (35.1–50 mm CL) juveniles to assess size-related effects. First, we carried out 13 lobster surveys on nine fixed 1-ha sites over a shallow reef lagoon (“before” period). Then, we deployed ten casitas in each of five sites and left four sites as controls, and conducted 22 further surveys (“after” period). Deployment of casitas resulted in a sixfold increase in juvenile density (76% contributed by small and 24% by large juveniles) and a sevenfold increase in biomass (40 and 60%, respectively). Capture–recapture results revealed that enhancement was achieved not by promoting individual growth but by increasing survival, persistence, and foraging ranges of small and large juveniles. Casitas both mitigated shortage of natural shelter and increased sociality, allowing for cohabitation of smaller, more vulnerable juveniles with larger conspecifics that have greater defensive abilities. Casitas may help enhance local populations of juvenile P. argus in Caribbean seagrass habitats, typically poor in natural crevice shelters. The use of MBACI and the simultaneous assessment of multiple interrelated response variables may be a powerful analytical approach to test shelter limitation in other species and to examine the function of structural habitat in other systems.     

A long-term mesocosm study on the settlement and survival of juvenile European lobster Homarus gammarus L. in four natural substrata

To date, the natural substratum preferences of early benthic phase (EBP) European lobsters (Homarus gammarus) remain largely unknown. This study utilised a large scale mesocosm experiment to determine if the animal favours cobble ground, similar to its American counterpart (Homarus americanus), or has other substratum preferences. Postlarvae were provided with the choice of settling on four natural substrata: sand, coralline algae, mussel shell and cobble. Over a nine month period, the number and size of juveniles on each substratum was recorded, with loss of chelipeds used as an indication of social interaction. After a 30 day period, a non-random distribution of lobsters was observed on the four substrata. Juveniles were more abundant in substrata which provided pre-existing shelter in the form of interstitial spaces, i.e. cobble and mussel shell, than in sand or coralline algae. The survival of individuals from postlarvae to 30 day old juveniles ranged from 5 to 14% with surviving benthic recruits showing a clear mode at 6-8 mm carapace length (CL) in size distribution. The density of lobsters per m(2) of cobble remained relatively constant (18/m(2)) throughout the study period while the density of juveniles on mussel shell decreased significantly (35 to 5/m(2)). The size distribution of lobsters on each substratum also varied with time. By the conclusion of the trial, lobsters found in mussel shell had a mode of 8-10 mm CL within a range of 6-14 mm CL while those in cobble had a mode of 10-12 mm CL within a range of 8-24 mm CL. Overall, the results underline the importance of shelter-providing habitat such as cobble or crevice-type substrata to EBP European lobsters. They also confirm that for a shelter-dwelling animal such as a lobster, the physical structure of the habitat is a key factor in determining both the size and number of its inhabitants.     

The influence of feeding on the metabolic activity of Antarctic krill (Euphausia superba Dana)

Summary The influence of feeding on the metabolic activity of juvenile krill was assessed from 24h experiments in which krill were incubated with various concentrations of diatoms (Chaetoceros calcitrans, Phaeodactylum tricornutum, Thalassiosira eccentrica, Fragilariopsis vanheurkii), newly hatched Artemia nauplii and latex beads. Krill fed on the larger food more efficiently, with reluctant feeding on latex beads. Feeding of krill expressed as clearance rates was poorly correlated with their oxygen uptake rates. Instead, a positive correlation was found between the oxygen uptake rates and ingestion rate (except for latex beads). The result implies that the specific dynamic action is the major cause of the increased oxygen uptake of krill. Krill fed diatoms increased both ammonia and phosphate excretion with increasing ingestion rate, but only phosphate excretion was increased in parallel with ingestion rate for those fed Artemia nauplii. Assuming the daily ration of krill in the field is 5% of the body weight, and the major food source is phytoplankton, oxygen uptake, ammonia excretion and phosphate excretion rates of wild krill are estimated to be 1.6, 4.5 and 7.8, respectively, times the rates of non-feeding krill in 24h laboratory experiments. Krill offered various kinds of food showed different metabolic quotients (O/N, N/P and O/P ratios). While no functional relationship was seen between the metabolic quotient and the ingestion rate of krill fed Artemia nauplii, those fed Fragilariopsis showed a progressive decrease in O/N, N/P, and O/P ratios as their ingestion rates increased.     

Effects of habitat edges on American lobster abundance and survival

Habitat edges frequently possess distinct ecological conditions that affect interactions such as competition and predation. Within a species' preferred habitat, the structural complexity and resource availability of adjacent habitats may influence the effect of edges on ecological processes. In nearshore waters of New England, American lobsters (Homarus americanus) inhabit fragmented cobble reefs that often are bordered by unvegetated sediment and occasionally by seagrass. We determined whether proximity to cobble patch edges, microhabitat characteristics within cobble habitat, and the type of habitat adjacent to cobble patches (seagrass or unvegetated sediment) influence the density and survival of juvenile and adult American lobsters in Narragansett Bay, Rhode Island, USA. We surveyed naturally occurring cobble patches and artificial cobble reefs to determine how the odds of finding lobsters varied with distance from the edge and habitat type. Additionally, we tethered lobsters at different distances from the edge inside and outside of cobble patches to determine how lobster relative survival varied with edge proximity and habitat type. In cobble habitat, the odds of finding large lobsters (adolescents and adults > 40 mm carapace length (CL)) were highest near patch edges regardless of adjacent habitat type, whereas smaller lobsters (e.g. emergent juveniles 15-25 mm CL) were more abundant in patch interiors when seagrass bordered cobble patches. The odds of finding lobsters also increased with the relative amount of cobble cover within patches. In predation experiments, lobster relative survival after 6 h was lowest outside of cobble and increased toward cobble patch interiors, but after 24 h this trend disappeared or reversed. Seagrass appeared to offer greater refuge for lobsters than did unvegetated sediment. Our results suggest that proximity to patch edges influences lobster distribution and survival, and that edge effects on lobsters vary with life history phase and with the type of habitat adjacent to cobble patches.     

Short- and long-term dietary effects on disease and mortality in American lobster Homarus americanus

The American lobster Homarus americanus fishery is heavily dependent on the use of fish as bait to entice lobsters into traps. There is concern that this food supplementation is nutritionally insufficient for lobsters, but previous experiments reported conflicting results. We conducted a long-term feeding experiment in which 1 yr old American lobsters were fed one of 7 diets for a period of 352 d, a time that allowed the lobsters to molt thrice. The diets consisted of fresh frozen herring, a 'wild' diet (rock crab, mussel, and Spirulina algae), a formulated artificial diet for shrimp, paired combinations of these 3 diets or a diet formulated at the New England Aquarium (Artemia, fish and krill meal, Spirulina algae, soy lecithin, vitamins and minerals). The lobsters fed the diet of 100% fish had higher initial molting rates, but within the period of this experiment all either contracted shell disease or died. Mixed diets resulted in higher survival and a lower probability of mortality. This research demonstrated a critical time component to diet studies in lobsters. Short- and long-term impacts of diet differ. In the long term, continual high consumption rates of fish by the lobsters promote poor health in all lobsters, not just those of market size. The use of fish as bait may make lobsters more susceptible to the stress associated with environmental fluctuation, thereby leading to increased disease and mortality. This nutritional stress can be used to develop a laboratory model of shell disease in American lobsters.     

Nitrogen excretion of adult sheep fed silages made of a mixed sward or of pure unfertilised grass alone and in combination with barley

Four adult rumen-fistulated wether sheep were fed silages combined with barley. The silages consisted of 48% grasses, 28% legumes and 24% other forbs (GCF) or of pure grass (G). The swards received no mineral fertiliser. The dry matter (DM) and fibre contents were lower in GCF than in G. Crude protein content of DM in GCF and G were 145 g/kg and 102 g/kg respectively. DM content as ash, lipids and non-fibrous carbohydrates were rather similar in both silages. About 40g DM were offered per kg BW0.75 and day either as silage alone or as a mixture of silage and barley (60:40). Faecal N excretion was greater with GCF than with G. The proportion of faecal bacterial and endogenous debris N reached 75 and 73% when GCF or G was fed, respectively. Undigested dietary N represented about 20%, and water soluble N accounted for 5-6% of faecal N. GCF caused more urinary N than G. Barley reduced urinary N excretion when supplemented to GCF. No dietary influence on urinary non-urea nitrogenous compounds was shown. GCF caused higher urinary urea N excretion than G and barley reduced this fraction when replacing part of GCF. Based on the urinary urea N proportions, it is concluded that N intake exceeded N requirement for any of the four diets fed. Dietary supplementation of ruminally fermentable carbohydrates can reduce urinary N excretion and this improves the efficiency of utilisation of N in N-unfertilised biodiverse grassland/ruminant farming systems.     

Protein synthesis, RNA concentrations, nitrogen excretion, and metabolism vary seasonally in the Antarctic holothurian Heterocucumis steineni (Ludwig 1898)

Seasonal changes in protein and nitrogen metabolism have not previously been reported in any Antarctic suspension-feeding species that ceases feeding for extended periods in winter. To provide comparison with data reported on Nacella concinna, a species that continues to feed in winter, we have measured feeding activity; oxygen consumption; ammonia, urea, and fluorescamine-positive substance (FPS) excretion; O : N ratios; body wall protein synthesis; RNA to protein ratios; and RNA activity at three times during the year in an Antarctic suspension-feeding holothurian. Feeding activity ceased for 4 mo during winter, and oxygen consumption rates decreased from 8.79+/-0.43 micro mol h(-1) to 4.48+/-0.34 micro mol h(-1). Ammonia excretion also decreased during winter from 2,600+/-177 nmol N h(-1) to 974+/-70 nmol N h(-1), but urea excretion rates increased from 178+/-36 nmol N h(-1) to 281+/-110 nmol N h(-1), while FPS excretion rates remained unchanged throughout the year with a seasonal mean of 88+/-13 nmol N h(-1). Oxygen to nitrogen ratios ranged between 6 and 10, suggesting that proteins were used as the primary metabolic substrate. Body wall protein synthesis rates decreased from 0.35%+/-0.03% d(-1) in summer to 0.23% d(-1) in winter, while RNA to protein ratios decreased from 33.10+/-1.0 microg RNA mg(-1) protein in summer to 27.88+/-1.3 microg RNA mg(-1) protein in winter, and RNA activity was very low, ranging between 0.11+/-0.01 mg protein mg(-1) RNA d(-1) in summer and 0.06+/-0.01 mg protein mg(-1) RNA d(-1) in winter. Heterocucumis steineni shows a larger seasonal decrease in oxygen consumption and ammonia excretion between February (summer) and July (winter) than N. concinna, while the proportional decrease in protein synthesis rates is similar in both species.     

Induction of cholesteryl ester transfer protein in adipose tissue and plasma of the fructose-fed hamster

Cholesteryl ester transfer protein (CETP) plays a pivotal role in the reverse transport of cholesterol and in the remodeling of circulating lipoproteins. While plasma and adipose tissue levels of CETP are affected by a variety of metabolic conditions, the extent of the effects of dietary factors, other than high cholesterol feeding, are not well understood. To further explore this paradigm, male Golden Syrian hamsters were fed for 4 weeks with a 60%-enriched fructose diet (F) and were compared to a matched group of animals fed with a normal chow diet (N). After feeding for 4 weeks, plasma insulin concentrations were lower in animals fed fructose than in control animals (F: 3.3+/-0.8 vs N: 7.4+/-1.9 ng/mL; p<0.03), but there was no significant difference in plasma glucose concentrations between the two groups (F: 138+/-7 vs N: 148+/-10 mg/dL; p>0.05). Fructose-fed animals showed significant increases in plasma triglyceride (F: 269+/-22 vs N: 165+/-22 mg/dL; p<0.01) and plasma cholesterol (F: 150+/-10 vs N: 113+/-6 mg/dL; p<0.02) concentrations compared with control animals. Total CETP activity and immunoreactive mass were higher in the plasma of fructose-fed animals that in that of controls (F: 1036+/-70 vs N: 826+/-43 pmol/h/mL, p<0.04 and F: 24.5+/-3.1 vs N: 37.5+/-4.3 AU, p<0.02, respectively). Adipose tissue CETP mRNA levels, assessed by the very sensitive ribonuclease protection assay, were 53% higher in fructose-fed animals than in controls (F: 14.1+/-2.0 vs N: 9.2+/-1.0 AU over a rRNA control; p<0.04). Adipose tissue CETP activity and immunoreactive mass also showed a statistically significant increase in the fructose-fed hamsters compared with those fed a normal diet (p<0.04). In conclusion, fructose feeding in Syrian hamsters induces a mixed dyslipidemia. These metabolic changes are accompanied by a significant increase in CETP levels, both in plasma and in adipose tissue. This phenomenon suggests that the increase in the expression of adipose tissue CETP may be caused either by the ambient hypercholesterolemia resulting from fructose feeding or by an attenuation of a possible inhibitory effect of plasma insulin concentrations on the expression of adipose tissue CETP in this feeding paradigm.     

Larval growth and survival of Echinometra lucunter (Echinoidea: Echinometridae) fed with microalgae Chaetoceros gracilis and Isochrysis galbana

Thirty sexually mature sea urchins (Echinometra lucunter; diameter 45.8 +/- 17.5 mm) were collected at Macanao, Margarita Island, Venezuela (11 degrees 48'29" N / 64 degrees 13'10" W). They were injected potassium chloride (50 M) directly into the celomic cavity. After two minutes 90% spawned (17 females and 10 males), the others never spawned. Fertilization was 87.0 +/- 12.6% (1:100 oocytes/sperm) at 29 +/- 2 degrees C. The fertile eggs were placed in three treatment gropsu with nine containers (18 liters; 2 eggs/ml) each, all with bottom aeration. Treatments were: Chaetoceros gracilis; Isochrysis galbana, and a mixture of both microalgae (respectively: 20 000 and 60,000 cell/ml for each microalgae, 1:1 for the mixture). Salinity, pH, temperature and larval survival were determinated daily. The study ended when the post-metamorphic phase was completed. The embryonic development time was 16.3 +/- 0.2 h until the prism stage at pH 8.4 +/- 0.1; 38 +/- 1 psu and 28 +/- 1.4 degrees C. The two-arms larval stage was reached at 24 h: 33 min, with a total length of 190 +/- 16.3 microm fed on C. gracilis, 152 +/- 19.0 microm with I. galbana and 182.4 +/- 14.1 microm with the mixture. The larvae next to metamorphosis reabsorbed the arms and had the characteristic shape of juvenile urchins at 12 days with 670.2 +/- 22.2 microm fed on C. gracilis, 665 +/- 12.1 microm fed on I. galbana and 670 +/- 14.1 microm fed on the mixture. The accumulated survival to the juvenile stage was 14.7 +/- 3.8% when fed on C. gracilis, higher than the other treatments (5.4 +/- 1.2; 14.0 +/- 2.6). E. lucunter is an excellent prospect to be commercially cultured because of its short embryonic (16 hours) and larval development time (12 days) and good survival rate when fed on monoculture (C. gracilis and I. galbana) or mixed diet (we recommend C. gracilis).