Effect of diet on fatty acid compositions in Sciaenops ocellatus

The role of dietary polyunsaturated fatty acids (PUFAs) on the fatty acid composition of juvenile red drum Sciaenops ocellatus was investigated. Individuals (n = 435) were fed three natural diets (Gulf menhaden Brevoortia patronus, brown shrimp Farfantapenaeus aztecus and Atlantic brief squid Lolliguncula brevis) that had significantly different proximate composition, energy density and PUFA compositions for 40 days. Diets were characterized as containing: high lipid, high protein, high energy and low PUFA (fish‐based), low lipid, low protein, low energy, moderate PUFA (shrimp‐based), and low lipid, high protein, moderate energy and high PUFA levels (squid‐based), respectively. Specimens were collected at days 0, 5, 10, 20 and 40 to evaluate rate of dietary fatty acid composition in tissues. Two‐source mixing models were used to calculate dietary fatty acid accumulation in consumer tissues. Results indicated that juvenile red drum incorporated an average of 35% dietary PUFAs after 5 days. Although relative biomass and dietary proximate composition had an effect upon the dietary fatty acid contribution, red drum averaged 91% incorporation of the five most prevalent PUFAs [18 : 2 (n ? 6), 20 : 4 (n ? 6), 20 : 5 (n ? 3), 22 : 5 (n ? 3) and 22 : 6 (n ? 3)] across all diets after 40 days. Growth varied as a function of diet and rates were higher for individuals fed the squid diet than those fed shrimp or fish diets primarily due to increased levels of protein and PUFAs [including 22 : 6 (n ? 3); 25·8%] in the diet. Red drum fed squid exhibited the greatest increase in average dietary fatty acid contribution by day 5, a trend that continued for the duration of the experiment. Since PUFA composition in red drum was significantly influenced by diet in as few as 5 days and almost completely incorporated into body tissues after 40 days, results from this study support the premise that fatty acids (especially PUFAs) are promising dietary indicators and may be useful for future studies examining trophic relationships of estuarine and marine fishes.     

A genetic linkage map of red drum,Sciaenops ocellatus

Second‐generation, sex‐specific genetic linkage maps were generated for the economically important estuarine‐dependent marine fish Sciaenops ocellatus (red drum). The maps were based on F₁ progeny from each of two single‐pair mating families. A total of 237 nuclear‐encoded microsatellite markers were mapped to 25 linkage groups. The female map contained 226 markers, with a total length of 1270.9 centiMorgans (cM) and an average inter‐marker interval of 6.53 cM; the male map contained 201 markers, with a total length of 1122.9 cM and an average inter‐marker interval of 6.03 cM. The overall recombination rate was approximately equal in the two sexes (♀:♂ = 1.03:1). Recombination rates in a number of linkage intervals, however, differed significantly between the same sex in both families and between sexes within families. The former occurred in 2.4% of mapped intervals, while the latter occurred in 51.2% of mapped intervals. Sex‐specific recombination rates varied within chromosomes, with regions of both female‐biased and male‐biased recombination. Original clones from which the microsatellite markers were generated were compared with genome sequence data for the spotted green puffer, Tetraodon nigroviridis; a total of 43 matches were located in 17 of 21 chromosomes of T. nigroviridis, while seven matches were in unknown portions of the T. nigroviridis genome. The map for red drum provides a new, useful tool for aquaculture, population genetics, and comparative genomics of this economically important marine species.     

Development of the follicle complex and oocyte staging in red drum,sciaenops ocellatus linnaeus, 1776 (perciformes,sciaenidae)

Pelagic egg development in red drum, Sciaenops ocellatus, is described using tiered staging. Based on mitosis and meiosis, there are five periods: Mitosis of Oogonia, Active Meiosis I, Arrested Meiosis I, Active Meiosis II, and Arrested Meiosis II. The Periods are divided into six stages: Mitotic Division of Oogonia, Chromatin Nucleolus, Primary Growth, Secondary Growth, Oocyte Maturation and Ovulation. The Chromatin Nucleolus Stage is divided into four steps: Leptotene, Zygotene, Pachytene, and Early Diplotene. Oocytes in the last step possess one nucleolus, dispersed chromatin with forming lampbrush chromosomes and lack basophilic ooplasm. The Primary Growth Stage, characterized by basophilic ooplasm and absence of yolk in oocytes, is divided into five steps: One‐Nucleolus, Multiple Nucleoli, Perinucleolar, Oil Droplets, and Cortical Alveolar. During primary growth, the Balbiani body develops from nuage, enlarges and disperses throughout the ooplasm as both endoplasmic reticulum and Golgi develop within it. Secondary growth or vitellogenesis has three steps: Early Secondary Growth, Late Secondary Growth and Full‐Grown. The Oocyte Maturation Stage, including ooplasmic and germinal vesicle maturation, has four steps: Eccentric Germinal Vesicle, Germinal Vesicle Migration, Germinal Vesicle Breakdown and Resumption of Meiosis when complete yolk hydration occurs. The period is Arrested Meiosis II. When folliculogenesis is completed, the ovarian follicle, an oocyte and encompassing follicle cells, is surrounded by a basement membrane and developing theca, all forming a follicle complex. After ovulation, a newly defined postovulatory follicle complex remains attached to the germinal epithelium. It is composed of a basement membrane that separates the postovulatory follicle from the postovulatory theca. Arrested Meiosis I encompasses primary and secondary growth (vitellogenesis) and includes most of oocyte maturation until the resumption of meiosis (Active Meiosis II). The last stage, Ovulation, is the emergence of the oocyte from the follicle when it becomes an egg or ovum. J. Morphol. 2012. © 2012 Wiley Periodicals, Inc.     

Microsatellite DNA markers for kinship analysis and genetic mapping in red drum,Sciaenops ocellatus (Sciaenidae,Teleostei)

Thirty‐eight nuclear‐encoded microsatellites were isolated from the marine fish Sciaenops ocellatus (red drum). The species is of economic importance in the southeastern United States, and declines in abundance have led to augmentation of the ‘wild’ fishery with hatchery‐raised fingerlings. The microsatellites will be useful for studies designed to assess larval/juvenile recruitment of hatchery‐raised individuals at varying spatial and temporal scales and for assessment of genetic components contributing to variation in performance and survival of hatchery‐produced fingerlings in the wild. The microsatellites also will prove useful as ‘anchor’ loci in constructing a genetic map.     

Allozyme differentiation within and between red drum (Sciaenops ocellatus) from the Gulf of Mexico and Atlantic Ocean

Nine polymorphic nuclear-gene (allozyme) loci were surveyed among 491 red drum ( Sciaenops ocellatus ) sampled in 1988 and 1989 from nearshore localities in the northern Gulf of Mexico (Gulf) and the Atlantic coast of the southeastern United States (Atlantic). Data were combined with those from a previous study to generate a data set of 762 individuals representing 11 sample localities in the Gulf and 175 individuals representing five sample localities in the Atlantic. The combined data set included individuals from the 1986 and 1987 year classes and permitted rigorous testing of both temporal and spatial genetic heterogeneity. Average heterozygosity-per-locus values (estimated using 33 assumed monomorphic loci) were 0·048 (Gulf red drum) and 0·046 (Atlantic red drum). Tests of heterogeneity in allele frequencies between year classes at individual localities and across regions (Gulf and Atlantic) were non-significant. Tests of spatial (geographic) heterogeneity indicated that red drum are weakly subdivided: genetically-differentiated subpopulations occur in the northern Gulf and along the south-eastern Atlantic coast. Genetic data were consistent with the hypothesis that red drum within the Gulf and along the Atlantic coast comprise singie subpopulalions. Genetic differences between Gulf and Atlantic red drum seem likeiy to stem from historical or recent interactions between dispersal and impediments to gene flow.     

Ontogeny of routine swimming speed and startle responses in red drum, with a comparison of responses to acoustic and visual stimuli

Routine swimming speed of larval red drum Sciaenops ocellatus increased throughout development but most rapidly for larvae >10 mm L _T. Red drum of all sizes swam faster than predicted by published summary equations based on other species, possibly due to more advanced development at a given length. Frequency and magnitude of startle responses increased over the larval period for both types of stimuli with most of the improvement taking place before larvae reached 8 mm L _T. Time to response for an acoustic and visual stimulus decreased early in the larval period but levelled off after 10 mm L _T. Response distance and response speed for both stimuli generally increased throughout the larval period, but response duration remained constant. Visually stimulated responses were generally longer in duration and distance covered than acoustically stimulated responses, while mean response speeds were similar.     

A modified stepping-stone model of population structure in red drum, Sciaenops ocellatus (Sciaenidae), from the northern Gulf of Mexico

Genetic studies of population or stock structure in exploited marine fishes typically are designed to determine whether geographic boundaries useful for conservation and management planning are identifiable. Implicit in many such studies is the notion that subpopulations or stocks, if they exist, have fixed territories with little or no gene exchange between them. Herein, we review our long-term genetic studies of red drum (Sciaenops ocellatus), an estuarine-dependent sciaenid fish in the Gulf of Mexico and western Atlantic Ocean. Significant differences in frequencies of mitochondrial DNA haplotypes and of alleles at nuclear-encoded microsatellites occur among red drum sampled across the northern Gulf of Mexico. The spatial distribution of the genetic variation, however, follows a pattern of isolation-by-distance consistent with the hypothesis that gene flow occurs among subpopulations and is an inverse (and continuous) function of geographic distance. However, successful reproduction and recruitment of red drum depend on estuarine habitats that have geographically discrete boundaries. We hypothesize that population structure in red drum follows a modified one-dimensional, linear stepping-stone model where gene exchange occurs primarily (but not exclusively) between adjacent bays and estuaries distributed linearly along the coastline. Gene flow does occur among estuaries that are not adjacent but probabilities of gene exchange decrease as a function of geographic distance. Implications of our hypothesis are discussed in terms of inferences drawn from patterns of isolation-by-distance and relative to conservation and management of estuarine-dependent species like red drum. Based on estimates of the ratio of genetic effective population size and census size in red drum, observed patterns of gene flow in red drum may play a significant role in recruitment.     

Studies on the Fatty Liver Diseases of Sciaenops ocellatus Caused by Different Ether Extract Levels in Diets

An experiment was conducted to study fatty liver disease caused by different ether extract levels in diets of juvenile Sciaenops ocellatus.Juvenile S.ocellatus(n=1,260;initial body weight approximately 2.73 g) were divided into nine treatment groups (triplicate groups per treatment) and fed in aquatic cases by a recirculated filtered rearing system;the temperature of the aquatic cases was maintained at 23.2±2.0°for 8 weeks.Nine kinds of diets containing different protein (38,42,46%) and ether extract levels (4,8,12%) were used.Results showed that the relative growth ratio and survival ratio of the fish fed on medium lipid diets (8%) or high ether extract diets (12%)were significantly lower than those of the fish fed on low ether extract diets (4%) (p<0.05).There was a positive correlation between the ether extract contents in hepatopancreas of fish and the ether extract contents of diets.At the end of the experimental period,the fish of the nine experimental groups suffered from different degrees of fatty liver disease and serious illness,and death occurred in a large number offish fed on medium (8%) and high ether extract diets (12%) from the third test week;mortality was highest in the fifth test week.The ill S.ocellatus showed symptoms of loss of appetite,lack of movement,black skin,and weight loss and eventually died.The main pathological change in ill fish was fatty liver disease.Their hepatopancreas were swollen and pale,accompanied by fatty degeneration,fatty necrosis of hepatocytes,and atrophy of the pancreas.Ultrastructural changes showed the presence of many lipid droplets and granules in the mitochondria,endoplasmic reticulum,and cell plasm of hepatocytes.Study results indicated that all the nine kinds of diets with different lipid or protein levels could cause nutritional fatty liver disease in juvenile S.ocellatus.The pathological severity and serious level of fatty liver disease in the tested fish positively correlated with the contents of the ether extract,but not with those of protein,in test diets.The increase in the level of ether extract in test diets was responsible for the direct cause of illness or death in juvenile S.ocellatus.     

Characterization of hepatic low-K(m) outer-ring deiodination in red drum (Sciaenops ocellatus)

The more biologically active thyroid hormone 3,5,3'-triiodothyronine (T(3)), is primarily derived from peripheral deiodination of thyroxine (T(4)). We characterized hepatic deiodination for a commercially important, warm water teleost fish, the red drum (Sciaenops ocellatus). Low K(m) outer-ring deiodination (ORD) activity was determined by production of free iodide ((125)I) upon incubation of hepatic microsomes with radiolabeled T(4). HPLC analysis demonstrated that (125)I, and T(3) were produced in equal amounts, thereby validating 125I as a measure of T(3) production. A small amount of 3,3',5'-triiodothyronine (reverse T(3)) was also produced by inner-ring deiodination. Production of (125)I was linear over a range of 0--100 microg protein/ml and for incubations of 30 min--4 h. Maximal ORD activity was measured at pH 6.6, 50 mM dithiothreitol (DTT) and an incubation temperature of 20 degrees C. Double reciprocal plots demonstrated that the average apparent K(m) was 5.1 nM and the average V(max) was 3.7 pmol T(4) converted/h per mg protein. ORD was not inhibited by propylthiouracil but was 50% inhibited by 90 microM of iodoacetic acid and 7 microM of gold thioglucose. The substrate analog preference was T(4) = tetraiodoacetic acid = reverse T(3) > triiodoacetic acid > T(3). In relation to other tissues, ORD for liver>gill>intestine>kidney. Similar hepatic deiodination activity was present in adult wild, aquacultured and laboratory-reared red drum, but in adult wild red drum the optimum temperature was higher. Red drum hepatic low-K(m) deiodination activity appears to most closely resemble rainbow trout hepatic and mammalian Type II deiodination. Evidence of inner-ring T(4) deiodination suggests a more active hepatic iodothyronine catabolic pathway than in other teleost species.     

Habitat-related predation on juvenile wild-caught and hatchery-reared red drum Sciaenops ocellatus (Linnaeus)

We examined the patterns of habitat-specific mortality for newly settled red drum (Sciaenops ocellatus) using an experimental mesocosm approach. Experiments were designed to analyze prey vulnerability and fish rearing-type (wild-caught or hatchery-reared) in estuarine habitats of varying structural complexity including marsh (Spartina alterniflora Loisel), oyster reef (Crassostrea virginica Gmelin), seagrass (Halodule wrightii Aschers), and nonvegetated sand bottom. We used two different predators, pinfish (Lagodon rhomboides Linnaeus) and spotted seatrout (Cynoscion nebulosus Cuvier). For both predators, vulnerability of wild-caught red drum was significantly lower in structurally complex habitats such as seagrass and oyster reef; the highest vulnerability was associated with the nonvegetated bottom. This habitat effect was not apparent for hatchery-reared prey. In trials using a combination of both rearing-types, there was no significant habitat effect on prey selection, but hatchery-reared red drum suffered higher overall mortality than wild-caught fish from pinfish predators. In these trials, spotted seatrout did not select for either prey type. Differences we observed in prey vulnerability were likely caused by behavioral differences between wild-caught and hatchery-reared red drum. Our results reinforce the conclusion that structural complexity in estuarine habitats increases survival of newly settled fishes. Our data also suggest that hatchery-reared red drum may be more vulnerable to predation than natural fishes, and that survival of stocked fish may be enhanced through habitat-related behavior modification.     

Hypoxia tolerance decreases with body size in red drum Sciaenops ocellatus

Mass‐specific oxygen consumption rate, i.e. standard metabolic rate (R_s) and critical oxygen tension (P_crit) of red drum Sciaenops ocellatus were measured and scaled over a 2500‐fold range in mass (M_F; 0·26–686 g). R_s conformed to well established models (R_s = 3·73·91 M_F^?0·21; r² = 0·86) while P_crit increased over the size range (P_crit = 3·15 log₁₀M_F + 16·19; r² = 0·44). This relationship may be ecologically advantageous as it would allow smaller S. ocellatus to better utilize hypoxic zones as habitat and refuge from predators.     

Identification and molecular analysis of a ferritin subunit from red drum (Sciaenops ocellatus)

Ferritin is a conserved iron binding protein existing ubiquitously in prokaryotes and eukaryotes. In this study, the gene encoding a ferritin M subunit homologue (SoFer1) was cloned from red drum (Sciaenops ocellatus) and analyzed at expression and functional levels. The open reading frame of SoFer1 is 531 bp and preceded by a 5′-untranslated region that contains a putative Iron Regulatory Element (IRE) preserved in many ferritins. The deduced amino acid sequence of SoFer1 possesses both the ferroxidase center of mammalian H ferritin and the iron nucleation site of mammalian L ferritin. Expression of SoFer1 was tissue specific and responded positively to experimental challenges with Gram-positive and Gram-negative fish pathogens. Treatment of red drum liver cells with iron, copper, and oxidant significantly upregulated the expression of SoFer1 in time-dependent manners. To further examine the potential role of SoFer1 in antioxidation, red drum liver cells transfected transiently with SoFer1 were prepared. Compared to control cells, SoFer1 transfectants exhibited reduced production of reactive oxygen species following H₂O₂ challenge. Finally, to examine the iron binding potential of SoFer1, SoFer1 was expressed in and purified from Escherichia coli as a recombinant protein. Iron-chelating analysis showed that purified recombinant SoFer1 was capable of iron binding. Taken together, these results suggest that SoFer1 is likely to be a functional ferritin involved in iron sequestration, host immune defence against bacterial infection, and antioxidation.     

The interplay of ontogeny and scaling in the interactions of fish larvae and their predators

In this review and synthesis, new data from field and laboratory experiments on red drum, Sciaenops ocellatus , larvae as prey to larger fishes are presented to illustrate two approaches to the study of developmental effects on predation. Various sizes and species of predatory fishes imposed very different levels of mortality on experimental populations of red drum larvae. Differences in predator size explained little of the overall variation in mortality rates. In the laboratory, responsiveness of red drum to a single size and species of predatory fish was relatively low through much of the developmental period but increased steadily. Response effectiveness improved and the predator's capture success decreased once the prey exceeded 20 mm in length. General ontogenetic trends in the behavioural interaction of various larvae and their piscine predators are described by combining 22 data sets on a scale of roughly comparable ontogenetic state. This scale, together with absolute and relative measures of predator and prey size, are used to assess the roles of ontogeny and scaling in the predation interaction. Ontogeny is shown to be a significant contributor to changes in responsiveness, response effectiveness, and capture success. The influence of scaling always took the form of an interaction with ontogeny and not a main effect.     

Infectious gastroenteritis caused by Vibrio harveyi (V. carchariae) in cultured red drum, Sciaenops ocellatus

Summary An outbreak of serious mortality among the cultured red drum Sciaenops ocellatus (L.) characterized by a swollen intestine containing transparent yellow fluid (ascites and gastroenteritis) occurred in July 2000 in Taiwan. A motile strain Rd 0700 was isolated from head kidney and/or the intestinal yellow fluid on tryptone soya agar (TSA) supplemented with 2% (w/v) NaCl and/or thiosulfate citrate bile salt (TCBS) sucrose agar plates. Applying biochemical characteristics, this strain was characterized and identified as Vibrio harveyi (V. carchariae). The bacteria could be re‐isolated from kidney, liver, and the transparent yellow fluid of swollen intestine of fish after bacterial challenge. The LD₅₀ values of the organism and its extracellular products (ECP) were 2.9×10⁷ colony forming units (CFU) and 3.85 μg protein g^?1 fish body weight, respectively. All moribund/dead fish exhibited gastroenteritis except those killed within 12 h. This is a first report showing that intraperitoneal (i.p.) injection of the ECP from V. carchariae is lethal to red drum and can reproduce gastroenteritis in the fish.     

Natural variation in elemental composition of sagittae from red drum

Concentrations of calcium, strontium, sodium, and potassium were measured along chronological transects of sectioned sagittae from adult red drum ( Sciaenops ocellatus ), using a wavelength-dispersive electron microprobe. Coarse sampling involved triplicate measurements at the centre of each opaque (winter) and translucent (summer) zone. Fine sampling was performed in duplicate at equidistant points (15 μm apart) spanning four opaque zones (3 years of life). Concentrations of strontium generally increased with distance from the core (age). Other elements showed no consistent long-term trends. Sodium and potassium showed consistent differences between winter and summer otolith zones for ages 6 to 15, but calcium and strontium did not show this seasonal difference. Sampling through these zones on a finer spatial scale confirmed the winter/summer differences as cyclic trends. There was general concordance between annual variation in sodium and potassium concentrations in otoliths and concurrent trends in sea temperature, but significant departures in agreement suggested that temperature was not the immediate determinant of sodium and potassium incorporation. It is suggested that the roughly seasonal patterns of variation in otolith sodium and potassium concentrations may be a result of reproductive activity.     

PERMANENT GENETIC RESOURCES: Cross-family amplification: microsatellites isolated from Macropodidae are polymorphic in Potoroidae

The superfamily Macropodoidea consists of two families - the Macropodidae and Potoroidae. Cross-species amplification and polymorphism of microsatellite loci is widely recognized within the macropodid family; however, the success of macropodid loci in potoroid species has not been as widely published. In this study, we tested the amplification and polymorphism of 17 cross-species microsatellite loci isolated from macropodids and potoroids in Bettongia lesueur (a potoroid). Success varied between loci and was not predicted by genetic distance from the species of isolation.     

Saline groundwater as an aquaculture medium: physiological studies on the red drum, Sciaenops ocellatus

Physiological responses of the euryhaline red drum, Sciaenops ocellatus, to chloride salt addition, low salinity, and high sulfate concentration were measured. Survival was increased by addition of calcium chloride (CaCl₂) or magnesium chloride (MgCl₂) to dilute artificial seawater (0.2 ppt salinity). Although survival and routine metabolic rates were greater in MgCl₂ treatments, growth and feed efficiency were greater in CaCl₂ treatments. Marginal metabolic scope increased when CaCl₂ or MgCl₂ were added to dilute artificial seawater. There was a strong positive linear relationship (p=0.0001, r=0.91) between fish survival and salinity of artificial seawater dilutions over the salinity range 0.1 to 3.0 ppt. Monovalent ion concentrations in red drum plasma varied; whereas, divalent ion concentrations were relatively constant. Survival and growth were not affected by high sulfate concentrations (2000 mg l^-1) in 3.0 ppt artificial seawater supplemented with either sodium sulfate or magnesium sulfate. Routine metabolic rate and marginal metabolic scope of red drum exposed to high sulfate concentrations were slightly, but not significantly, lower than those of red drum in 3 ppt artificial seawater.     

An experimental assessment of genetic tagging and founder representation in hatchery-reared red drum (Sciaenops ocellatus) used in stock enhancement

Multiplexed microsatellite markers were evaluated as genetic tags for red drum ( Sciaenops ocellatus ) juveniles used in stock enhancement. Offspring were generated from spawns of nine sets of five broodfish (three dams and two sires) in individual brood tanks. Intensive sampling, by trawling, at 2, 7, 8, 10 and 11 days after release of ∼192 500 hatchery-raised fingerlings resulted in recovery of a total of 310 fingerlings. All parents and recovered offspring were genotyped for variation at 30 microsatellites combined for simultaneous assay in six multiplex panels. An optimal combination employing three of the six multiplex panels allowed unambiguous parentage assignment of all recovered offspring. Only 21 of 52 possible dam x sire combinations were represented among recovered offspring. The founder equivalent ( f _e) of the recovered offspring was 8.7 vs the expected f _e of 36.0 (95% CI = 33.3–38.4) if reproductive success was randomly distributed among breeders. The significantly lower founder equivalent translated into reduced genetic diversity among the recovered offspring and may reflect differing contributions of individual broodfish to spawning events, differing productivity among brood tanks, and/or variable survival of families during early larval and/or juvenile stages.     

PERMANENT GENETIC RESOURCES: Consensus primers of cyp73 genes discriminate willow species and hybrids (Salix, Salicaceae)

Consensus primers, based on exon sequences of the cyp73 gene family coding for cinnamate 4-hydroxylase (C4H) of the lignin biosynthesis pathway, were designed for the tetraploid willow species Salix alba and Salix fragilis. Diagnostic alleles at species level were observed among introns of three cyp73 genes and allowed unambiguous detection of the first generation and introgressed hybrids in populations. Progeny analysis of a female S. alba with a male introgressed hybrid confirmed the codominant inheritance of each intron. Sequences of the diagnostic alleles of both species were similar to those found in the hybrids.