Enhancement of immunity and disease resistance in the white shrimp,Litopenaeus vannamei,by the probiotic,Bacillus subtilis E20

Effects of Bacillus subtilis E20 isolated from fermented soybean on immune parameters and the disease resistance of the white shrimp (Litopenaeus vannamei) after 98 days of B. subtilis E20 feeding were evaluated in this study. Shrimp fed B. subtilis E20-containing diets at concentrations of 10⁶ (E206), 10⁷ (E207), and 10⁸ (E208) cfu kg^?1, respectively, had significantly increased survival rates of 13.3%, 16.7%, and 20%, compared to the control (fed no probiotic) after being challenged with Vibrio alginolyticus. There were no significant differences in the total hemocyte count, respiratory burst, or superoxide dismutase glutathione peroxidase among all treatments. Shrimp fed a higher concentration of the probiotic (E208) exhibited significant increases in phenoloxidase activity, phagocytic activity, and clearance efficiency compared to control shrimp. In addition, B. subtilis E20 showed a weaker inhibitory effect against the growth of Aeromona hydrophila with around a 0.3-cm inhibitory zone, but showed no inhibitory effects against other selected pathogens, such as white shrimp pathogens: V. alginolyticus and Vibrio vulnificus. These results suggest that the increased resistance of shrimp after B. subtilis E20 consumption occurs through immune modifications, such as increases in phenoloxidase activity, phagocytic activity, and clearance efficiency against V. alginolyticus.     

The effects of dietary supplementation with butyrate and polyhydroxybutyrate on the digestive capacity and intestinal morphology of Pacific White Shrimp (Litopenaeus vannamei)

This study evaluated dietary supplementation with sodium butyrate and polyhydroxybutyrate (PHB) on the enzymatic activity, in vitro nutrient digestibility, and intestinal morphology of Pacific white shrimp (Litopenaeus vannamei). The treatments were: shrimp fed diet supplemented with 2% butyrate, shrimp fed diet supplemented with 2% PHB, and shrimp fed unsupplemented diet. Shrimp fed with PHB-supplemented diet showed higher values of intestinal protease, trypsin, chymotrypsin, and amylase. Shrimp fed with butyrate-supplemented diet showed higher intestinal lipase than unsupplemented shrimp. Butyrate increased hepatopancreatic protease, trypsin, and chymotrypsin activity and in vitro protein digestibility. Shrimp fed with PHB-supplemented diet and butyrate had higher digestibility of polysaccharides and lipids. Shrimp fed with PHB-supplemented diet presented increase in the length, width, and perimeter of intestinal villi. Animals fed with both diets retained overall integrity of their intestinal mucous membrane. The findings show that dietary supplementation with PHB and butyrate can alter intestinal morphology and could improve the digestive capacity of L. vannamei.     

Deep-water shrimp (Pandalus borealis, Krøyer 1838) as indicator organism for fish-farm waste

A feeding experiment was carried out with deep-water shrimp (Pandalus borealis), a common benthic inhabitant of Norwegian fjords. Shrimp were reared in tanks for three months, fed either salmon feed or cod, and the fatty acid profile of their muscle tissue was monitored. The salmon feed pellets and cod had completely different fatty acid compositions, with significant differences in most of the analysed fatty acids, eight of them, 14:0, iso16:0, 16:1n7, 16:2n11, 18:3n3, 20:0, 22:0 and 22:1n11, differing between the two diets by a factor of 10 or more. The levels of the fatty acids in the diets differed also substantially from the levels in the shrimp tissue at the start of the experiment. The shrimp were fed ad libitum and both groups increased significantly in total fatty acid content in the course of the experiment. Nevertheless, the fatty acids made up no more than 6.5 mg g^− 1 muscle tissue, with 88 ± 1% of them bound in polar, membrane lipids. Their composition in the tissue did also change to a certain extent, but the resulting tissue composition did not reflect the fatty acid composition of the diets. Only two fatty acids, 18:2n6 and 18:3n3, clearly followed the dietary level. They are abundant in commercial salmon feed since they are rich in plant oils used as additives to the commercial feed. Determination of fatty acid levels in shrimp tissue may enable shrimp to be used as indicator organisms for the influence of organic fish-farm waste on the food web in adjacent areas.     

PLASTICITY OF JAW AND SKULL MORPHOLOGY IN THE NEOTROPICAL CICHLIDS GEOPHAGUS BRASILIENSIS AND G. STEINDACHNERI

I examined plasticity of jaw and skull morphology induced by feeding different diets in two species of the neotropical cichlid genus Geophagus. The two species possess different modes of development, which affect the size at which young begin feeding. I hypothesized that the difference in size at first feeding could lead to a difference in the amount of change inducible in the two species. The young of the substrate-spawning species, G. brasiliensis, which begin feeding at a smaller size, were predicted to be more plastic than those of the mouthbrooding species, G. steindachneri. The two diets used to induce differences were brine shrimp nauplii and chironomid larvae. Numerous measures of the jaw and skull differed significantly between groups fed the two diets but the amount of plasticity induced was small and would not present a problem for taxonomists. Contrary to my prediction, both the magnitude and pattern of plasticity induced in the two species was similar. Thus, mode of parental care and the size at which young begin feeding do not affect the degree of plasticity. Fish fed brine shrimp nauplii were longer in oral jaw region, but were shorter and shallower in the area behind the oral jaws. An additional group of G. brasiliensis was fed flake food to compare the results of this study to other studies. The differences in measures between fish fed brine shrimp diets and flake food diets were greater than those between fish fed brine shrimp and chironomid larvae. A possible role of plasticity for enhancing rather than retarding morphological evolution is discussed.     

Laboratory study of the grass shrimp feeding preferences

Grass shrimps are very common in various aquatic habitats, and are generally considered omnivorous. But, despite the numerous studies on interspecific trophic interactions, few studies have evaluated their feeding strategy, especially by experimental approaches.In this study, we determined, in the absence of both intra and interspecific competitive interactions, the feeding preferences of the freshwater grass shrimp Palaemonetes antennarius for the most common potential resources in its habitat. Plant and animal items were offered as food to each adult shrimp in multiple-choice laboratory experiments. Resource selection was determined under conditions of low and high food availability and related to the shrimp body size. The role of microbial colonisation in favouring detritivory was also investigated.Results of these experiments showed that P. antennarius consumed only animal items, mostly preferring the isopod Proasellus coxalis. In addition, palatability of the unselected plant remains and non-living prey was not improved by the microbial enrichment. Shrimps also resorted to cannibalism at low ration. By contrast, at high ration they specialised on a narrower range of resources, directing more their feeding efforts towards isopods. The preference ranking of the selected food types was inversely related to the average mass of the prey and varied with the shrimp body size. In particular, the number of live isopods in the diet increased exponentially with the shrimp mass at food high ration, which resulted not to be limiting. In conclusion, food availability influences the food niche of P. antennarius whose feeding strategy in the laboratory is facultative specialisation on dead and live animals rather than omnivory. Ease of handling and/or capture seems to play a role in the food preference ranking.     

Feeding Responses of Hatchery-Reared Gilthead Sea Bream (Sparus aurata L.) to a Commercial Diet and Natural Prey Items

Many fish species have evolved feeding mechanisms and behaviours enabling them to feed on specific prey. However, such mechanisms may not be optimal for feeding on commercial-pelleted diets in aquaculture. Gilthead sea bream chew and occasionally eject pellets or parts of pellets from the mouth when feeding on commercial diets. This may result in an increase in nutritional waste from the intensive culture of this species. In this study we examined the prevalence of this food processing behaviour in two sizes of sea bream, feeding on three types of natural prey items in comparison to a commercial pellet, to give an insight into the circumstances in which excess chewing and ejection of food items from the mouth occurred. These included two hard-textured food items (commercial pellet and hard-shelled prey) and two soft-textured food items (larvae and small crustacean). Both sizes of sea bream frequently consumed the soft-textured food types, however large sea bream also frequently consumed hard-textured pellets. Hard-textured food required longer handling times and elicited more chewing and the ejection of food items from the mouth. These results suggest that future investigations on the food processing behaviour and consequent waste when fed commercial diets differing in texture could give an insight into improving diets and feeding efficiency for intensively cultivated gilthead sea bream.     

Feeding Responses of Hatchery-Reared Gilthead Sea Bream (Sparus aurata L.) to a Commercial Diet and Natural Prey Items

Many fish species have evolved feeding mechanisms and behaviours enabling them to feed on specific prey. However, such mechanisms may not be optimal for feeding on commercial-pelleted diets in aquaculture. Gilthead sea bream chew and occasionally eject pellets or parts of pellets from the mouth when feeding on commercial diets. This may result in an increase in nutritional waste from the intensive culture of this species. In this study we examined the prevalence of this food processing behaviour in two sizes of sea bream, feeding on three types of natural prey items in comparison to a commercial pellet, to give an insight into the circumstances in which excess chewing and ejection of food items from the mouth occurred. These included two hard-textured food items (commercial pellet and hard-shelled prey) and two soft-textured food items (larvae and small crustacean). Both sizes of sea bream frequently consumed the soft-textured food types, however large sea bream also frequently consumed hard-textured pellets. Hard-textured food required longer handling times and elicited more chewing and the ejection of food items from the mouth. These results suggest that future investigations on the food processing behaviour and consequent waste when fed commercial diets differing in texture could give an insight into improving diets and feeding efficiency for intensively cultivated gilthead sea bream.     

Size-biased predation by the gila topminnow poeciliopsis occidentalis (Baird and Girard)

The objective of this study is to document under both field and laboratory conditions the phenomenon of size-biased feeding by the Gila topminnow, Poeciliopsis occidentalis, and to shed light on the mechanisms responsible for this process. Adult female Gila topminnows feed in Monkey Spring, Santa Cruz County, Arizona, on a variety of food items, but Hyalella azteca is an important element of its invertebrate diet. The size of the amphipods ingested by female topminnows is a function of the size of the fish, with larger fish taking larger prey. There is also a strong preference for topminnows to select large amphipods from within the size limits imposed by the width of the mouth.The correlation between fish size and prey size was also seen in the laboratory, utilizing Daphnia similis and food pellets as prey. The tendency to select large prey from a range of available sizes was prominent with both Daphnia and pellets. The feeding period in the laboratory is characterized by two distinct phases. During the first phase, feeding is rapid and nonselective. As the feeding progresses, the rate of feeding drops dramatically and selectivity increases.More complex laboratory feeding experiments gave equivocal results. When fish were presented pellets of two sizes at different densities and at different ratios of small to large, size biased feeding was not clearly evident. Both predator and prey densities, agonistic behavior, and reaction distance should be explored more thoroughly as next steps in attempts to mimic feeding behavior in nature.Extracted from a Ph. D. thesis written by the junior author     

Change in food ingestion induces rapid shifts in the diversity of microbiota associated with cutaneous mucus of Atlantic salmon Salmo salar

To test the hypothesis that a switch in diet might cause changes in the abundance and composition of mucous‐dwelling microorganisms, a short‐term experiment was conducted with Atlantic salmon Salmo salar. Fish were fed on three different diets: pelleted S. salar feed, macroinvertebrates or pellets supplemented with an antibiotic. A fourth group of fish was deprived of food throughout the trial. Seven days after manipulating diets, significant differences were found in microbial density and community composition (quantified by different morphologically distinct colonies), particularly between fed and unfed animals. Moreover, food deprivation caused a rapid decrease in the number of epidermal mucous cells of the lateral skin, which may indicate a decrease in mucous secretion and explain differences in the diversity of mucous‐dwelling microbiota observed in the fish. This is the first report of an effect of feeding regime on the abundance of microbial communities associated with cutaneous mucus of fishes.     

Compensatory growth,condition and food utilization in barbel Barbus barbus juveniles reared at different feeding periodicities with a dry diet

In a 40 day experiment, barbel Barbus barbus juveniles were fed a dry diet continuously, or food was withheld for 2, 5 or 10 days, and then resumed feeding. Improved feed utilization efficiency allowed fish deprived of food for 2 or 5 days to fully compensate for body mass loss. Short‐term food deprivation as a method of preventing negative effects of overfeeding in intensive rearing of juvenile B. barbus is proposed.     

A first report on the shrimp <Emphasis Type="Italic">Pontonia</Emphasis> sp. and other potential symbionts in the mantle cavity of the penshell <Emphasis Type="Italic">Pinna carnea</Emphasis> in the Dominican Republic

Examination of the mantle cavity of 310 penshells Pinna carnea, collected from seagrass beds in southwestern Dominican Republic, revealed the presence of four species from three phyla as potential symbionts. The shrimp Pontonia sp. was found in 178 penshells, the cardinalfish Astrapogon stellatus in 18, an anemone (order Actiniaria) in two, and a pea crab (family Pinnotheridae) in one. The penshell likely provides these organisms with a refuge from predators. It also provides nutrition for shrimp as they consumed food trapped in the mucus secreted by the penshell host. All of the cardinalfish, and 91% of the shrimp, were found in penshells measuring >150 mm in hinge length. At approximately 150 mm, the shells of P. carnea thicken and so flatten less when the valves are closed. As a result, larger penshells provide more mantle-cavity space for accommodating organisms. Shrimp and cardinalfish size increased with the size of the host penshell. The positive relationship between shrimp size and penshell size, a prevalence of male-female pairs of shrimp and other field observations, suggest that a long-term association exists between shrimp and penshells, and that the mating system of the shrimp involves social monogamy.     

Feeding rhythms and diet of Farfantepenaeus paulensis under pen culture in Patos Lagoon estuary, Brazil

The feeding habits of Farfantepenaeus paulensis under pen culture in the Patos Lagoon estuary (Brazil) were studied. A total of 1074 shrimp had their stomach contents analyzed. Samples were taken bi-hourly over a 24 h period at about 10 day intervals during 2 months. F. paulensis did not exhibit strict feeding periodicity (except at D_21-22 and D_32-33). Thus, the offering of feed pellets during daylight is recommended but the rates of feeding must be further investigated. F. paulensis showed an omnivorous feeding behavior. Despite daily supply of feed pellets, natural food comprised the major part of the shrimp stomach contents. Among prey organisms, polychaetes and tanaids were the main groups recorded. Consumption of detritus and plant material decreased as shrimp grew. Intake of feed pellets increased significantly in the second month of culture (i.e. 5 g mean shrimp weight), thus it might be possible to reduce the initial input of commercial feed.     

Utilization of shrimp industry waste in the formulation of tilapia (Oreochromis niloticus Linnaeus) feed

A rapid expansion of fisheries is demanding an adequate supply of efficient, nutritious and inexpensive fish feed, because feed contributes highly to the cost of fish production. Shrimp head, a waste product from the shrimp export industry qualifies as an economical, abundant and good quality protein source for fish feeds. In the present work, shrimp head silage powder, which contained approximately 40% protein, was used as a substitute for fish flour. Four feeds, in the form of pellets, were prepared by substituting shrimp head silage for fish flour at 0%, 33.3%, 66.6% and 100% dietary levels. Other ingredients such as corn, soy, bovine blood, cassava and corn cob flours, soy oil, vitamin premix, salt, and other components also were used in the formulation. A commercial fish feed was used as the control. The proximate composition of these feeds did not differ significantly at p>0.05, except for the protein content of the control feed, which was about 30.6% versus 35.4-36.9% protein in the other diets. No significant differences (p>0.05 level) in weight and length of juveniles fed with the different feeds during a period of 60 days were observed. In all cases, an excellent correlation (0.9950-0.9996) between weight and length of juveniles was observed. No significant difference in growth of juveniles fed on R1, R2, R3, or R4, or the control feed, was observed. Similarly, the proximate analyses of the flesh of juveniles did not present significant differences (p>0.05). The result of the study indicates that the shrimp head silage could replace fish flour as an ingredient in tilapia feed with economic advantages and without sacrificing the quality of the feed.     

The mechanism of ultraplanktonic entrapment in anuran larvae

Tadpoles of several different genera were fed graded suspensions of uniform polystyrene particles to determine the lower size limit of particles that could be ingested. Certain tadpoles can extract suspended particles as small as 0.126 μ in diameter from the water. In terms of particle size, this is an efficiency comparable to the best mechanical sieves that can currently be produced by man. A mechanism for ultrasplanktonic entrapment is proposed on the basis of scanning electron micrographs of the secretory ridges in the branchial food traps of Rana catesbeiana before and after feeding. Xenopus tadpoles in yeast suspensions modify their clearance and buccal pumping rates in response to varying food concentrations. This may be an adaptation for maintaining a constant input of food mass to the tissues that extract the food from the water. Variability in the lower size limit of filterable particles among tadpoles of different genera correlates with the availability of suspended matter in the microhabitat where these tadpoles may be found.     

Influence of diet on sex differentiation of Hippolyte inermis Leach (Decapoda: Natantia) in the field

The gut contents of the shrimp Hippolyte inermis were investigated for 1 year along a depth transect through a seagrass bed. Besides size, sex and weight of all individuals were recorded. The diets of immature and adult individuals were compared to detect any influence of food on sex development, since previous investigations indicated a correlation of the life cycle of this protandric species with the abundance of algal food in the environment, and laboratory experiments demonstrated the effect of diatoms of the genus Cocconeis on the direct development of females. Results indicated that the shrimp is an opportunistic herbivore, able to feed on both plant and animal items, with a preference for macroalgae and diatoms present on the leaves of Posidonia oceanica. Small females, deriving from direct differentiation, had a diet significantly different from that of males. The difference was due to a larger abundance of microalgae in the guts of young females. The influence of microalgal food on the sex reversal mechanism of this species, previously detected through laboratory experiments, was demonstrated to control the life cycle of H. inermis in the field.     

Organic matter processing by the shrimp Palaemonetes sp.: Isotopic and elemental effects

Aquatic crustaceans often play a major role in organic matter (OM) transformation and recycling through their feeding and excretory activities. In this study, we measured the isotopic and elemental composition of organic matter fed to Palaemonetes sp. shrimp and the fecal pellets they produced. Nitrogen (N) content of the food (8.2 ± 0.2%, mean ± SD) was significantly higher than the fecal pellets (2.0 ± 0.9%), a pattern that also applied to the carbon (C) content of food (46.7 ± 1.0%) and fecal pellets (14.3 ± 6.8%). We also found a significant decrease in the N content of undigested, macerated food (6.1 ± 0.9 %) relative to food that had been soaked in artificial seawater (ASW) and artificial seawater that had previously contained shrimp (CASW) in the absence of feeding shrimp. We found no significant difference in N or C isotopic composition between the dry food, ASW- and CASW-soaked control food, and fecal pellets. We did, however, observe a significant increase in δ¹⁵N of the undigested, macerated food (δ¹⁵N = 6.3 ± 0.6‰) relative to both the dry flake food (δ¹⁵N = 5.6 ± 0.2‰) and controls incubated in the absence of shrimp in either ASW (δ¹⁵N = 5.6 ±0.3‰) or CASW (δ¹⁵N = 5.8 ± 0.1‰). Our results differ from previous findings of isotopic alteration of OM during processing by crustaceans (copepods), suggesting that isotopic changes related to feeding might be either taxon- or food-specific. This study also provides information on the influence of grazers/shredders on both the elemental and isotopic composition of POM, suggesting that larger aquatic shredders can influence the chemical composition of particles by either physical manipulation of the POM (release of DOM) or by facilitating microbial colonization of the POM.     

Adrenalectomy Reduces Adiposity by Decreasing Feed Efficiency,Not Direct Effects on White Adipose Tissue

EDENS, N. K., A. MOSHIRFAR, G. M. POTTER, S. K. FRIED, AND T. W. CASTONGUAY. Adrenalectomy reduces adiposity by decreasing feed efficiency, not direct effects on white adipose tissue. Obes Res. Objective: This study was conducted to establish the effects of adrenalectomy (ADX) on adipose tissue metabolism in male Sprague—Dawley rats fed a standard chow diet. Research Methods and Procedures: The effects of adrenalectomy on adipose cell size, lipoprotein lipase activity, and basal and insulin-stimulated glucose conversion to lipid and lipolysis were measured. Results: ADX decreased body weight gain during the postoperative period in the absence of changes in food intake; feed efficiency was decreased significantly. ADX decreased adipocyte size by 30%. ADX increased adipocyte response to the effect of submaximal concentrations of insulin on lipid synthesis and lipolysis. ADX decreased maximally insulin-stimulated lipid synthesis, but this effect was accounted for by decreased adipocyte size. In contrast, ADX had no effect on maximally insulin-inhibited lipolysis. ADX did not affect heparin-releasable LPL. The small effect of ADX on residual extractable adipose tissue LPL activity was accounted for by decreased fat cell size. Discussion: ADX decreased adiposity in the absence of changes in food intake, lipoprotein lipase activity, and adipocyte lipid metabolism. The effect is best attributed to decreased feed efficiency.     

Dietary vitamin C and its derivatives affect immune responses in grass shrimp, Penaeus monodon

Effects of L-ascorbic acid (AA) and its four derivatives, namely L-ascorbyl-2-sulfate (C2S), L-ascorbyl-2-polyphosphate (C2PP), L-ascorbyl-2-monophosphate-Na (C2MP-Na) and L-ascorbyl-2-monophosphate-Mg (C2MP-Mg) on the immune responses of juvenile grass shrimp, Penaeus monodon, were studied. The vitamin C deprived diet together with diets supplemented with either adequate or high (five times adequate) levels of AA, C2S, C2PP, C2MP-Na and C2MP-Mg were each fed to triplicate groups of shrimp (mean initial weight: 0.37 +/- 0.01 g) for 8 weeks. Significantly (P<0.01) higher weight gain (WG), feed efficiency (FE), survival, total haemocyte count (THC), superoxide anion (O2) production ratio and phenoloxidase (PO) activity were observed in shrimp fed diets supplemented with adequate and high levels of ascorbate than shrimp fed the vitamin C deprived diet, regardless of the ascorbate source. Among the ascorbate sources, shrimp fed C2MP-Mg and C2PP containing diets had higher THC than shrimp fed AA, C2S and C2MP-Na containing diets, regardless of the supplementation level. Shrimp fed adequate levels of C2MP-Mg and C2PP and high levels of C2MP-Mg containing diets had higher O2 production ratios than shrimp fed AA and C2S containing diets. Shrimp fed adequate levels of C2MP-Mg and C2PP and high levels of C2PP containing diets had higher PO activity than shrimp fed AA, C2S and C2MP-Na containing diets. These data suggest that dietary ascorbate enhances immune responses in P. monodon and different ascorbate sources may affect the immune responses differently.     

Weak meiofaunal trophic linkages in Crangon crangon and Carcinus maenus

To document the relative importance of meiofauna as prey for juvenile Crangon crangon and Carcinus maenus, short interval (1.5-2 h) collections were made in the muddy Lynher Estuary (Plymouth, Great Britain) and in the sandy-bottom Ythan Estuary (Aberdeenshire, Scotland) in 1990. Gut passage times of Crangon fed flaked fish food and fluorescent tracer in the laboratory at 13 °C ranged from 4 to 20 h. Wild shrimp exhibited feeding periodicity, with guts fullest during high tide in both locations. Visual and immunological gut contents analyses revealed that meiofaunal nematodes and harpacticoid copepods were present only in recently settled shrimp from 8 to 12 mm total length on muddy bottoms. Larger shrimp collectively consumed up to 33 different macrobenthic prey types. Shrimp were fullest at night (mean gut contents weight = 8% wet body weight, Lynher) or at dawn (6%, Ythan). The Lynher Carcinus gut contents—from animals 8 to 30 mm carapace width, examined visually only—contained mostly fluids, green benthic algae, sediment particles, and masses of unidentifiable prey remains plus digestion-resistant hard parts visually identifiable as macrobenthic in origin. None of the 203 crabs examined from the 24-h collection contained meiofaunal prey. Crangon shrimp probably eat meiofaunal prey for only a brief period of time after their initial settlement to the bottom. Evidence for significant top-down impacts on meiofauna from these two abundant shallow-water predators was weak. More trophic studies are needed on newly settled epibenthic predators to test the hypothesis that biological control of shallow-water meiofauna is important.