Ana Farías

Effect of antibiotic treatment during larval development of the Chilean scallop Argopecten purpuratus

Abstract The requirement for antibiotic use in a culture depends principally on the quality of water available and on the use of strict husbandry of the materials closely related with the culture. The purpose of the present study was to determine the dose of chloramphenicol resulting in better survival and growth rates of Chilean scallops between the early larvae and pediveliger stages cultured in closed systems with manual dosing of food two times per day. Two experiments with antibiotic application during larval development of the Chilean scallop ( Argopecten purpuratus ) were conducted. The experiments were carried out at the early larval stage (86 μm) and at the eyed stage (213 μm). The antibiotic concentration ranged between 0 and 8 mg l −1 chloramphenicol (CHL) per day. The survival and growth rates of the larvae were monitored for 10 days at each stage. In the experiment with eyed larvae, larval settlement and percent metamorphosis were measured. Use of an antibiotic on the early larvae resulted in significantly better growth and survival. Growth rates were 2.3±0.3 and 2.6±0.2% per day when using 2 and 8 mg l −1 CHL per day, respectively, compared with 1.3%±0.2 per day for the larvae without antibiotic. Survival was also better with antibiotic treatment reaching 50% compared with 35% without antibiotic. The metamorphosis was highest using of 8 mg l −1 CHL day −1 , compared with treatment without antibiotic. Between 75 and 79% of the metamorphosed larvae were found settled on the nets in the treatments using 2 and 8 mg l −1 , while only 55.5% were settled in the nets in the treatment without antibiotic. The results of the experiments indicate that concentrations of 2 and 8 mg l −1 CHL demonstrated effective control of larval contamination. Moreover, the condition of the postlarvae was improved by the addition of 8 mg l −1 CHL from eyed larvae to postlarvae.

Reproductive conditioning of Chilean scallop (Argopecten purpuratus) and the pacific oyster (Crassostrea gigas): effects of enriched diets

The quality of diet fed to bivalve broodstock during reproductive conditioning directly affects growth and survival of their larval and postlarval progeny. The objective of the present study was to improve the quality of larval production in the Chilean scallop (Argopecten purpuratus) and the Pacific oyster (Crassostrea gigas) by testing of the effects of different experimentally enriched diets on the conditioning and early development of progeny under laboratory conditions. The diets used included protein-rich microalgae and mixtures of microalgae and lipid emulsions. Quality of D-larvae, pediveligers, and 1-mm postlarvae from the variously fed broodstock was measured to evaluate each diet as indicators of growth and survival of the early life stages. Biochemical analyses were carried out on eggs and larvae to determine the effects of the different diets on these parameters. The main results for the scallops and oysters were that a conditioning diet containing algae rich in protein improved larval growth and survival. This effect did not, however, extend past metamorphosis. Also, the best conditioning diet increased the lipid content of the eggs, as well as the protein content of the D-larvae, although the mechanism for this remains unclear.

Polyunsaturated fatty acids in total lipid and phospholipids of chilean scallop Argopecten purpuratus (L.) larvae: effects of diet and temperature

Abstract The composition of lipids and fatty acids of larval scallop Argopecten purpuratus were determined when cultured at one of two temperatures and using one of the three algal diets. Larvae grown at 12 °C had the lowest values of phosphatidylcholine (PC) and highest values of cholesterol and steryl esters (SE). The ratio of triacylglycerol (TAG)/cholesterol was affected by temperature but not by diet and the lowest values were observed in larvae grown at 12 °C. By using the ratio of TAG/cholesterol as an index of larval condition, the best condition was observed at the begining of the experiment, before feeding, with values of 3.9 and 2.9 in eggs and D-larvae, respectively. The best culture conditions for larval scallop from this point of view was a temperature of 19 °C and a diet of Isochrysis galbana grown at 25 °C while the poorest condition was observed in larvae cultured at 12 °C and 19 °C and fed the mixture of Isochrysis aff galbana (clone T- Iso ) high-protein and Chaetoceros neogracile high-protein (IH/GH diet). However, no significant differences in the growth rate and survival of larvae fed different diets were detected. I. galbana grown at 25 °C had no detectable percentage of arachidonic acid (ARA; 20:4 n −6), but larvae grew well and ARA was detected in PC and phosphatidylethanolamine (PE) in similar quantities to other diets. This suggests ARA may not be essential during early life stages of larval Chilean scallops. Total lipids and PC of larvae were affected by the diet in their ratio of docosahexaenoic acid (DHA; 22:6 n −3)/eicosapentaenoic acid (EPA; 20:5 n −3), but PE composition was highly conserved and was unaffected by diet. DHA/EPA ratio in total lipid and in PC showed highest values when larvae were fed I. galbana grown at 25 °C. Temperature affected the total highly unsaturated fatty acids (HUFA) in total lipids, PC and PE of larvae. In all cases values were lowest when larvae were cultured at 12 °C. In addition, increased temperature increased the ratio of EPA/ARA in PC and decreased the ratio of monounsaturated fatty acids (MUFA)/saturated fatty acids in PE. The ratio of n −6/ n −3 PUFA was constant in total lipid, PE and PC of larval scallops regardless of temperature or diet.

Rearing and Growth of the Octopus Robsonella fontaniana (Cephalopoda: Octopodidae) From Planktonic Hatchlings to Benthic Juveniles

Globally, octopus larviculture is one of the challenges faced in the attempt to diversify aquaculture and achieve cephalopod farming. Currently, only juveniles of Octopus vulgaris, Octopus joubini, and Enteroctopus dofleini have been obtained at an experimental level. This is the first study to look at the characteristics of planktonic and benthic Robsonella fontaniana juveniles in an effort to analyze the morphometric changes occurring during their planktonic and benthic phases and to explore the feasibility of obtaining settlement under controlled conditions. The morphometric measurements varied exponentially over time and did not show different tendencies before and after settlement. Mantle growth in relation to total length fit a logarithmic regression, whereas arm length and eye diameter increased linearly with respect to total length throughout the entire paralarval and juvenile periods. This suggests that the size of the mantle decreases with age in proportion to the total octopus length, whereas the organs more directly involved in catching prey tend to increase in direct proportion to the total length. The present study shows that R. fontaniana can be reared from hatching through the final paralarval stage on a diet of Lithodes santolla (king crab) zoeae; after settlement, the juveniles can be reared on a diet of crab such as Petrolisthes.

The effect of dietary protein content on growth and biochemical composition of Chilean scallop Argopecten purpuratus (L.) postlarvae and spat

Abstract This study shows the effect of three different levels of dietary protein content on the performance of postlarvae (1.8 mm) and spat (6.3 mm) of the Chilean scallop, Argopecten purpuratus. The postlarvae showed significant differences in growth and survival, with better growth when fed the high protein diet (N+). The biochemical composition of the postlarvae showed only significant differences in the content of total carbohydrate, with the highest values in postlarvae fed the normal protein diet (N±) and the lowest values in starved postlarvae. There were no significant differences in growth nor survival of spat fed the test diets. The biochemical composition of the spat was significantly different in protein content, with the highest level in spat fed the N+ diet, while the lipid content increased marginally significantly in spat fed the normal diet. The carbohydrate content in spat did not change. These results show that postlarvae and spat follow a different pattern of energy metabolism, because the diet N+ only increased the growth in early postlarval stages and lost its effect in the later stages of development. This paper discusses the threshold age at which the metabolic pathway changes, coinciding with the change from the sessile life attached by the byssus to the typical unattached and free swimming life of A. purpuratus. It also highlights the efficiency and possible use in commercial hatcheries of high protein diets.

Physiological energetics of the green abalone, Haliotis fulgens, fed on a balanced diet.

A regression of different physiological responses against body size enables populations or stock cultures of various size ranges to be compared. Thus, the aim of the present work was to evaluate the physiological responses from juvenile green abalone (Haliotis fulgens), grouped according to size, in a standard controlled culture condition within their optimal range to create the balanced growth equation within an allometric relation, providing a basic framework for physiological research into H. fulgens. Feed intake, absorption efficiency, respiration and excretion were measured as functions of dry tissue weight (DTW) in juvenile abalone acclimated on a balanced diet. The daily feed intake (I) was related to body mass by the relationship I (mg day−1)=24.25W0.59. Absorption efficiency averaged 87% and was independent of body size. The equation relating daily respiration rate (R) to body mass was R (ml O2 day−1)=12.013W0.704, including night correction. The rate of ammonia excretion (U) was related to dry tissue weight by the equation U (μmol N–NH4 day−1)=43.57W0.85. The energetic value of food was 18.8 J mg−1. The low feeding activity (<1% of abalone live weight per day) was compensated for by a relatively high absorption efficiency and a depression of 23% in the metabolic rate during diurnal activity. Gross and net growth efficiencies were constant throughout the size range, with average values of 36.4% and 41.5%, respectively. Values of the O/N ratio, with an average of 31.5, showed a higher use of proteins from the diet as an energy source for the size range studied.

EVALUATING THE EFFECTS OF FORMULATED MOIST DIETS ON JUVENILES OF PATAGONIAN OCTOPUS ENTEROCTOPUS MEGALOCYATHUS (GOULD 1852)

ABSTRACT The aim of this study was to evaluate the performance of Patagonian octopus fed with moist diets formulated with several local feed ingredients. All formulated diets were based on crab paste (70%) and the experimental feed ingredient (30%). Experiment 1 assayed salmon meal, prime sardine meal, and wheat gluten, using fresh fish as a control; experiment 2 assayed prime fish meal and macroalgal meal against crab paste alone as a control. The ingestion rate was lower than expected for all diets except those of fresh fish, crab paste alone, and crab paste plus prime sardine meal. No significant differences were found in the observed digestibility of the diets, indicating, in general, low digestibility, even for fresh fish. The highest protease values were observed for crab paste plus prime sardine meal in both experiments. The better growth of Enteroctopus. megalocyathus was obtained when these were fed fresh fish, which was associated with the greater consumption observed in this diet, as neither the digestibility nor the enzymatic activities of the hepatopancreas were related to this greater growth.

Sibling cannibalism on the small octopus Robsonella fontaniana (d'Orbigny, 1834) paralarvae

Abstract Several experiments were conducted to determine if cannibalism or other aggressive behaviour occurs during the planktonic stage of the small octopus Robsonella fontaniana. Paralarvae from the same egg mass were treated under different rearing densities, with and without the presence of food, different water volume and confronted with the development of a feeding habit. Observation of aggressive and cannibalistic behaviour among sibling paralarvae was present in the majority of groups and treatments. However, in the largest water volume with the lowest density maintained (2 paralarvas/500 ml) no sign of aggressive behaviour was observed with or without the presence of food. The degree of cannibalism observed during this study fluctuated within 12.5–65.5%, with attacks starting between the 7th and 10th day, and where the time at which experiments finished (last single individual within recipient) was observed 8 days after attacks began. Paralarvae put under a feeding regime of 5 days did not show differences in all measured parameters between those that were continuously fed and the ones which were deprived of food.

Chapter 9 Nutrition in Pectinids

Summary Fulfilment of the nutritional requirements of pectinids in the reproductive conditioning, larval culture, and postlarval culture phases is determined by the levels and quality of the proteins and lipids in the diets utilised in their culture. The protein content of the microalgal diet affects the time to reach maturity, the fecundity of the females, and the energy balance in the broodstock, showing that diets high in protein favour all these parameters and also improve the quality of the larvae. An increase in the protein content of microalgal food by manipulation of their culture medium significantly increases larval growth and also favours improved growth of the postlarval juveniles to the 5mm size. Pectinid larvae show greater growth and survival when the diets contain high levels of DHA/PA together with low values for EPA/HUFA, with EPA being less important because the larvae are efficient in desaturation beginning with the linolenic acid (18:3n−3), and also seem to have the capacity for obtaining ARA from linoleic acid (18:3n−6). The microalgal diet for pectinids in the larval phase may be substituted up to 40% by lipid emulsions enriched with EPA and DHA, while in the postlarval phase to 2 mm this substitution may be up to 20% of the microalgal diet without damaging growth and survival in this phase. The carbohydrates begin to be important in late juvenile stages, which may be related to availability of enzymes in the digestive system where amylases only appear after the scallops reach the 5 mm size. Pectinids at all stages are assured of adequate levels of vitamins and pigments when fed with microalgae. Micronutrients in the marine environment of the scallops readily provide their mineral requirements by direct absorption from seawater.

Variation of Fatty Acids in Isochrysis galbana (T-Iso) and Tetraselmis suecica, Cultured under Different Nitrate Availabilities

The use of high protein microalgae obtained by increasing the content of nitrate in the culture medium is recommended to improve the performance of broodstock, larvae and juveniles in bivalve hatchery. However, the effect of these concentrations of nitrate on the composition of fatty acids in microalgae is not known and it is relevant to assess possible changes in its nutritional properties for filtering bivalves. The results of nitrate increase in Isochrysis aff. galbana (clone T-Iso) showed that in the high nitrate medium, T-Iso is high in protein and carbohydrate and low in ash, and also exhibits higher values of polyunsaturated fatty acids (PUFA), especially n-3PUFA. The best culture medium for Tetraselmis suecica would also be the one high in nitrate because of it is high in protein and lipid and low in ash, although the best values PUFA were observed in the standard nitrate medium. T-Iso was characterized by its tendency to increase the level of n-3 PUFA with the increase of nitrate, while T.suecica was characterized by no effect of nitrate on the contents of n-3 PUFA of the cells nor a PUFA pattern related to the increase or decrease of nitrate.