The larval development of lateral musculature in gilthead sea bream Sparus aurata and sea bass Dicentrarchus labrax

Fibre-type differentiation of the lateral musculature has been studied in Sparus aurata (L.) and Dicentrarchus labrax (L.) during larval development. Histochemical and ultrastructural techniques show two presumptive muscle layers and two germinative zones of presumptive myoblasts. At hatching, myotomal muscle consists of a monolayer of thin undifferentiated cells near the skin (first germinative zone) overlying another mono-layer of small diameter fibres extending hypaxially and epaxially away from the transverse septum. Below this, there is a much thicker, deep layer of fibres, generally large in diameter and polygonal in shape. The presumptive myoblasts are located between these two layers of fibres in the second germinative zone. Initially, the superficial and deep muscle fibres show high and low myosin ATPase activity, respectively. Both layers grow by generating new fibres from the two mentioned germinative zones. At the end of larval life, the superficial layer changes its histochemical profile from high to low myosin ATPase activity and, at the same time, intermediate or pink muscle fibres can be observed by oxidative activity (the NADH-TR reaction). Morphometric analysis shows a significant increase in mean fibre diameter during successive ages, as shown by the Student's t-test (hypertrophic growth). Skewness and kurtosis values of fibre diameters point to the generation of a new fibre population from the germinative zones (hyperplastic growth).     

Life cycle of Ceratothoa oestroides, a cymothoid isopod parasite from sea bass Dicentrarchus labrax and sea bream Sparus aurata

Ceratothoa oestroides (Risso, 1826) (Isopoda: Cymothoida) is a protandric hermaphrodite parasite on a wide range of wild fish species. In recent years it has become a threat to cage-reared fish facilities, where high fish density provides optimal conditions for transmission. Its impact on fish health and economical gain is significant, varying from growth retardation and decreased immunocompetency to direct loss due to mass mortalities of juvenile fishes. Because of the sheltered location of the parasite in the buccal cavity of fishes, chemotherapeutics are ineffective. An understanding of the C. oestroides life cycle and its behavioral mechanisms could prove constructive tools for the prevention and control of infection. This study describes the reproductive cycle of C. oestroides experimentally induced in different fish hosts and temperature regimes. Sea bream larvae Sparus aurata and 1 yr annular sea bream Diplodus annularis were chosen as experimental models, and were held at 22 and 19.5 degrees C, respectively. The reproductive cycle of S. aurata was not completed within 4 mo (at which point the last larva died of severe anemia and respiratory distress), while that of the annular sea bream was completed successfully after 1 mo.     

Amino acid composition and endocrine control of vitelline envelope proteins in European sea bass (Dicentrarchus labrax) and gilthead sea bream (Sparus aurata)

The vitelline envelopes of European sea bass and gilthead sea bream are both composed of mainly four proteins with the molecular masses of 90, 52, 48, 45 kDa and 75, 50, 48, 44 kDa, respectively. Each protein has an amino acid composition that is characterized by a high content of proline and glutamic acid and a low content of cysteine, similar to the whole vitelline envelope of both species. The amino acid composition suggests that each protein is distinct but related to the other vitelline envelope proteins. The use of homologous antisera shows that both species have vitelline envelope proteins that are induced by estradiol-17β. As males of both species synthesize these proteins after treatment with estradiol-17β, the origin is not restricted to the ovaries. Vitellogenin of both Eurpoean sea bass and gilthead sea bream has the apparent molecular mass of 170 kDa. © 1995 Wiley-Liss, Inc.     

Mineral composition in fillets of sea bass (Dicentrarchus labrax) and sea bream (Sparus aurata): a comparison of cultured and wild fish

The objective of this study was to determine some of the trace mineral elements in four commercial feeds commonly available in Turkey for marine culture and in fillets of cultured and wild sea bass (Dicentrarchus labrax) and sea bream (Sparus aurata). The feeds and cultured fish were from four different fish farms operating in the same region but with four slightly different feeds. Concentrations of Iron (Fe), Zinc (Zn), Manganese (Mn), Copper (Cu), Lead (Pb), Cobalt (Co), Nickel (Ni), Chromium (Cr), and Cadmium (Cd) were analyzed in the feeds and fillets of cultured as well as wild fish. Significant differences in the mineral concentrations existed within feed groups, cultured fish groups as well as between cultured and wild fish. Fe, Zn, and Mn in the feeds, Fe, Co, and Zn in sea bass and Fe, Zn and Co in sea bream were predominant among the nine analyzed minerals. Fe, Zn, Mn, Cr, and Ni contents in the fillets of wild sea bass were significantly, (P < 0.05) lower than those of the cultured sea bass groups. Co, Cr, Pb, and Ni in the fillets of wild sea bream were also significantly (P < 0.05) lower than those of cultured sea bream groups. These differences in trace elements in the cultured and wild fish were probably related to differences in their dietary mineral concentrations.     

Lateral line deformities in wild and farmed sea bass (Dicentrarchus labrax,L.) and sea bream (Sparus aurata,L.)

The lateral line of aquaculture fishes has rarely been studied although it is a very important anatomical organ that could serve as an inexpensive and easy tool to distinguish farmed from wild individuals. In the present study, lateral line deformities were examined in both wild and farmed sea bass (Dicentrarchus labrax) and sea bream (Sparus aurata) specimens to try to detail all possible differences between them. In order to do so, the morphology of the trunk lateral line in wild and farmed adults was examined whereby two major deformities were observed in both species: the ‘scale pocket’ deformity (14–40% incidence in all groups) where the specialized scales are missing but the canal underneath is present and the scale print is obvious, and the ‘somatic scales’ deformity (14–56% incidence in farmed individuals only) where the missing lateral line is covered with normal somatic scales. Histological examination confirmed the macroscopic observations in that the lateral line mechanism was present – although damaged – beneath the scale pocket deformity and completely absent beneath the somatic scales deformity. It is argued that the scale pocket deformity is a result of an accident during the life of the fish whereas the somatic scales deformity is an actual deformity in development.     

Cellular responses in the skin of the gilthead sea bream Sparus aurata L. and the sea bass Dicentrarchus labrax (L.) exposed to high ammonia

Adult gilthead sea bream Sparus aurata and sea bass Dicentrarchus labrax were exposed for 24 and 48 h, respectively, to two concentrations of ammonia each (mean values of 3·34 and 13·10 mg l(-1) TA-N in S. aurata; 2·99 and 11·90 mg l(-1) TA-N in D. labrax). Light microscopy and computerized morphometry were used to evaluate ammonia-induced alterations in skin structure during exposure and following recovery in normal water. In S. aurata, ammonia exposure induced a concentration-dependent increase in the number (hyperplasia) of neutral mucous cells (mc), with peak values at 24 h recovery after exposure. An increase in the dispersion of melanosomes in skin melanocytes was also observed in the dermis and occasionally in the epidermis of S. aurata, with peak values at 24 h of ammonia exposure. Exposure of D. labrax to ammonia had, likewise, concentration-dependent effects on mucous secretion. Of the two types of mc in this species, there was an increase in the number of the neutral mc and a reduction in the much more numerous acid mc, with peak values at 24 and 48 h, respectively, of ammonia exposure. The more intense mucous secretion in D. labrax compared to S. aurata could be related to the lower tolerance to ammonia in D. labrax, as reported elsewhere. Finally, the increase in melanosome dispersion was less evident in D. labrax, due to highly variable control values. These morphological alterations to the skin could be useful indicators of non-specific stress in cultured fishes.     

Ultrastructure of the peritoneal exudate cells of seawater teleosts,seabream (Sparus aurata) and sea bass (Dicentrarchus labrax)

The peritoneal exudates of seabream and sea bass consist of granulocytes, lymphocytes and macrophages. These cells show conspicuous ultrastructural differences from the same cell-types of blood and head-kidney, which have not been reported previously. Peritoneal exudate granulocytes differ from their corresponding circulating or head-kidney forms in the following way: (a) they are larger in size, and (b) their abundant cytoplasmic granules have some new ultrastructural features, and a new granule population might also be present. Likewise, lymphocytes also show a noticeable difference; they contain a sparse population of small dense cytoplasmic granules. Monocytes, macrophages, and transitional forms between these two cell-types, are also found. The percentage of peritoneal exudate cell-types is different in seabream and sea bass. Macrophages in sea bass represent the most abundant peritoneal exudate cell-type. However, seabream shows lower percentages of macrophages than granulocytes.     

Cloning and analysis of expression of a gilthead sea bream (Sparus aurata) Mx cDNA

In the current work, we have cloned and sequenced the full cDNA for a Mx protein in the gilthead sea bream (Sparus aurata) by RACE PCR. The Mx cDNA of 2182 bp contained an open reading frame of 1857 bp that codes for a protein of 618 aa. Within the coding sequence, characteristic features of Mx proteins were found, such as a tripartite guanosine-5'-triphosphate (GTP)-binding motif (GXXXSGKS/T, DXXG and T/NKXD), the signature of the dynamin family, LPRG(S/K)GIVTR, and a sequence that codes for a leucine zipper at the C-terminal region of the protein. An RT-PCR was optimised to estimate the level of expression of Mx protein in sea bream. Through this method we determined that Mx is constitutively expressed in head kidney, liver, spleen, heart, gills, muscle and brain of healthy sea bream. Intramuscular challenge of sea bream with polyinosinic:polycytidylic acid (Poly I:C) up-regulated Mx expression in liver, head kidney, spleen and muscle. Constitutive expression was also found in isolated head kidney macrophages and blood leukocytes. This expression was significantly up-regulated by addition of Poly I:C. Mx was not constitutively expressed in the sea bream established cell line, SAF-1, but Poly I:C and nodavirus were also capable of inducing Mx expression in this cell line.     

Epidemiology of Cryptosporidium molnari in Spanish gilthead sea bream (Sparus aurata L.) and European sea bass (Dicentrarchus labrax L.) cultures: from hatchery to market size

A long-term epidemiological study of Cryptosporidium molnari in aquacultured European sea bass (ESB) and gilthead sea bream (GSB) was performed in different types of facilities on the Atlantic, Cantabric, and Mediterranean coasts. Four types of studies were carried out. In study A, fish raised from juveniles to marketable size (ongrowing stage) were periodically sampled in three different types of cultures. Studies B and C focused on hatchery and nursery facilities. In study D, occasional samplings were performed during mortality or morbidity outbreaks. As a general trend, C. molnari was more prevalent in GSB than in ESB. Data on the distribution pattern of C. molnari in total sampled GSB (studies A, B, and D) had a variance higher than the mean (overdispersion). In GSB (study A), the type of ongrowing system (sea cages, earth ponds, or indoor tanks) was found to have no significant effect. There was a significant relationship between the presence of the parasite and both fish weight and season. The highest infection values were recorded in spring. Prevalence and intensity had convex weight profiles, with a peak in 30- to 100-g fish. In study D, the prevalence of infection was higher in fish recently introduced in sea cages and in preongrowing systems. In studies B and C, fish were almost never infected before entering the postlarval and nursery facilities. The parasite seems to enter the host mainly through the water in production steps with less stringent water treatment. Recirculation systems and fish cannibalism could contribute to oocyst concentration and dispersion in aquaculture facilities.     

Rearing temperature enhances hepatic glucokinase but not glucose-6-phosphatase activities in European sea bass (Dicentrarchus labrax) and gilthead sea bream (Sparus aurata) juveniles fed with the same level of glucose

The aim of this work was to elucidate if the previous results observed in hepatic glucokinase (GK) and glucose-6-phosphatase (G6Pase) activities in European sea bass and gilthead sea bream are due to temperature per se or to differences in feed intake at different water temperatures. For that purpose triplicate groups of fish (30 g initial body weight) were kept at 18 degrees C or 25 degrees C during two weeks and fed a fixed daily ration of a glucose-free or 20% glucose diet. At the end of the experimental period, plasma glucose levels in both species were not influenced by water temperature but were higher in fish fed the glucose diet. Higher hepatic GK activity was observed in the two fish species fed the glucose diet than the glucose-free diet. In the glucose fed groups, GK activity was higher at 25 degrees C than at 18 degrees C. Glucose-6-phosphatase activities in both species were not influenced by water temperature. In European sea bass and in contrast to gilthead sea bream it was observed an effect of dietary composition on G6Pase activities with surprising higher activities recorded in fish fed the glucose diet than in fish fed the glucose-free diet. Overall, our data strongly suggest that European sea bass and gilthead sea bream are apparently capable to strongly regulate glucose uptake by the liver but not glucose synthesis, which is even enhanced by dietary glucose in European sea bass. Within limits, increasing water temperature enhances liver GK but not G6Pase activities, suggesting that both species are more able to use dietary carbohydrates at higher rearing temperatures.     

Patterns of gastric evacuation, digesta characteristics and pH changes along the gastrointestinal tract of gilthead sea bream (Sparus aurata L.) and European sea bass (Dicentrarchus labrax L.)

A comparative study of gastric evacuation rates (GERs) and digesta content, moisture and pH values along the gastrointestinal tract was performed between gilthead sea bream and European sea bass. In order to distinguish species-specific differences from diet-elicited effects, all parameters were determined under either a fishmeal diet or a carob seed germ meal diet that contained high levels of total and soluble non-starch polysaccharides. GERs were significantly different between species and they were not affected by diet. Similarly, species-specific patterns were revealed in the distribution of digesta and water content along the gastrointestinal tract. In sea bream, stomach digesta and water content decreased with time, whereas in sea bass stomach retained the highest digesta and water content throughout the sampling period. The anterior and distal intestine exhibited the lowest accommodating capacities of digesta and water in either species. Overall, sea bream performed stomach digestion at lower hydration levels and higher pH compared with sea bass. Diet affected stomach moisture in both species and pH of stomach digesta in sea bass and of all intestinal sections in sea bream. The results obtained indicated that water and inorganic ion exchanges through the gut may differentiate between the species and warrant further investigation.     

Cymothoid isopod parasites in aquaculture: a review and case study of a Turkish sea bass (Dicentrarchus labrax) and sea bream (Sparus auratus) farm.

This paper reviews the occurrence of cymothoid isopod parasitism in aquaculture, reports the first case of infection by a cymothoid isopod (Ceratothoa oestroides) in Turkish aquaculture, and analyses its effects on sea bass Dicentrarchus labrax. Analyses revealed that C. oestroides negatively affects the weights and lengths of sea bass hosts. These effects have been previously underestimated because host age has not been accounted for. The analysis of condition factors as a means of assessing parasite effects is therefore likely to be misleading. Infection of fish of all ages by all cymothoid stages indicates that sea bass are not intermediate hosts but that C. oestroides has effected a complete host shift.     

Apoptosis in sea bream Sparus aurata eggs

In the present study, the sea-bream Sparus aurata, a pelagic egg spawner, was used as experimental model, in order to establish the occurrence of apoptosis in vertebrates with external reproduction. The same female ovulates floating and nonfloating eggs, but only the former, after fertilization, proceed to embryo development. The eggs were divided into floating and nonfloating and both were analyzed for the presence of several apoptosis markers. The results here reported provide evidence that the nonfloating cells present severe shrinkage and highly express both FAS receptor and FAS ligand on their surface. Furthermore, DNA fragmentation and mitochondria swelling were found, suggesting that the nonfloating eggs were cells programmed to die.     

Ontogeny of the endocrine pancreas in sea bass (Dicentrarchus labrax)

Summary The development of the endocrine pancreas of the teleost sea bass (Dicentrarchus labrax, L.) was examined from hatching to 61 days, using the peroxidase-antiperoxidase technique for light microscopy. Mammalian and bonito insulin (mI and bI)-, salmo somatostatin-25 (SST-25)-, somatostatin-14 (SST-14a and b)-, glucagon-, bovine pancreatic polypeptide (PP)-, peptide tyrosine-tyrosine (PYY)- and salmo neuropeptide Y (NPY)-like immunoreactivity was demonstrated. Four ontogenetic stages were established according to the organization and immunostaining of the endocrine cells. One cell strand or primordial cord showing mI/bI- and SST-25/SST-14a-like immunoreactivity was first found at hatching in the dorsal epithelium of the anterior zone of the midgut (stage 1). One primitive islet, comprising outer SST-25/SST-14a- and inner mI/bI- and SST-14a/ SST-14b-immunoreactive cells, was found in 2- to 5-day-old larvae (stage 2). One single islet, in which glucagon-immunoreactive cells appear in the periphery, was found in larvae from 9 to 20 days after hatching (stage 3). One big islet containing, in addition, PP-immunoreactive cells in the outer region and slender cell processes which showed PYY-like immunoreactivity, was found from 25 to 61 days after hatching. During this period, primordial islets, composed of SST-25- and bI-immunoreactive cells, and clustered or isolated pancreatic endocrine cells, close to the pancreatic duct, as well as small and intermediate islets (secondary islets), in which glucagon, PP, PYY and NPY seem to be co-localized, were progressively found (stage 4). The origin of the endocrine pancreas of sea bass, and the ontogenetic and phylogenetic significance, are discussed.     

Embryonic development of the sea bass Dicentrarchus labrax

The embryonic development of the sea bass Dicentrarchus labrax during the endotrophic period is discussed. An 8 cells stage, not reported for other studied species, results from two rapid successive cleavages. Blastula occurs at the eighth division when the embryo is made of 128 cells. During gastrulation, the infolded blastoderm creates the endomesoblastic layer. The Kupffer??s vesicle is reported to drive the left/right patterning of brain, heart and digestive tract. Heart formation starts at 8 pairs of somites, differentiation of myotomes and sclerotomes starts at the stage 18 pairs of somites; main parts of the digestive tract are entirely formed at 25 pairs of somites. At 28 pairs of somites, a rectal region is detected, however, the digestive tube is closed at both ends, the jaw appears the fourth day after hatching, but the mouth is not opened before the fifth day. Although cardiac beating and blood circulation are observed, gills are not reported in newly hatched individuals; eye melanization appears concomitant with exotrophic behavior.     

Vitamin E in early stages of sea bass (Dicentrarchus labrax) development

This study reports titration of vitamin E levels in the sea bass (Dicentrarchus labrax) using high-pressure liquid chromatography. The first part of the work is devoted to vitamin E detection in: (1) plasma of maturing females and males characterized by different body sizes; (2) seminal fluid and eggs; and (3) developing embryos of sea bass fed with vitamin E. In the second part of the study, variations of vitamin E levels during larval development are analyzed. The results show a direct correlation between plasma vitamin E content and body size for both adult male and female sea bass. High vitamin E levels were found in seminal fluid, in eggs before and after fertilization, and in embryos during development and at hatching, whereas vitamin E level was low in dead embryos and in embryos with limited survival. During larval development, the vitamin E content decreased slowly but steadily during the first four days of larval growth; subsequently, it progressively increased from day 9 to day 40. In teratogenic larvae, vitamin E content was significantly higher than in normal larvae. This study provides evidence on how vitamin E exerts an antioxidant defense in sea bass reproduction.