Sharpsnout Seabream Research Articles

Morphometric characterization of sharpsnout sea bream (Diplodus puntazzo) and gilthead sea bream (Sparus aurata) spermatozoa using computer-assisted spermatozoa analysis (ASMA)

As part of a larger study on sperm quality and cryopreservation methods, the present study characterized the head morphometry of sharpsnout sea bream (Diplodus puntazzo) and gilthead sea bream (Sparus aurata) spermatozoa, using both scanning electron microscopy (SEM) and computer-assisted morphology analysis (ASMA). The latter method has been used rarely in fish and this is its first application on sharpsnout sea bream and gilthead sea bream spermatozoa. Results obtained using SEM are expensive and time-consuming, while ASMA provides a faster and automated evaluation of morphometric parameters of spermatozoa head. For sharpsnout sea bream spermatozoa, similar head measurement values were obtained using both ASMA and SEM, having a mean ± standard error length of 2.57 ± 0.01 μm vs 2.54 ± 0.02 μm, width of 2.22 ± 0.02 μm vs 2.26 ± 0.04 μm, surface area of 4.44 ± 0.02 μm2 vs 4.50 ± 0.04 μm2 and perimeter of 7.70 ± 0.02 μm vs 7.73 ± 0.04 μm using ASMA and SEM, respectively. Although gilthead sea bream spermatozoa were found to be smaller than those of sharpsnout sea bream, spermatozoal head morphometry parameters were also found to be similar regardless of evaluation method, having a mean head length of 1.97 ± 0.01 μm vs 1.94 ± 0.02 μm, head width of 1.80 ± 0.01 μm vs 1.78 ± 0.02 μm, surface area of 3.16 ± 0.03 μm2 vs 3.18 ± 0.06 μm2 and perimeter of 6.52 ± 0.04 μm vs 6.56 ± 0.08 μm using ASMA and SEM, respectively. The results demonstrate that ASMA can be considered as a reliable technique for spermatozoal morphology analysis, and can be a useful tool for studies on fish spermatozoa, providing quick and objective results.

SHELF LIFE OF NEW CULTURE SPECIE (DIPLODUS PUNTAZZO) IN REFRIGERATOR

ABSTRACT The shelf life of sharp snout sea bream (Diplodus puntazzo) stored in refrigerator was investigated by measurement of sensory, chemical (total volatile basic nitrogen [TVB‐N], trimethylamine [TMA‐N], thiobarbituric acid [TBA] and pH) and microbiological (total viable and psychrophilic count) analysis. According to the sensory and chemical analysis results evaluated, the shelf life of sharp snout sea bream was detected as 10 days for storage at refrigeration temperatures, respectively, as compared with 8 days of sensory analysis results.PRACTICAL APPLICATIONSSharp snout sea bream is one of the important fish species in the aquaculture sector in Turkey. In recent years, the aquaculture sector was mainly interested with the fish species Dicentrarchus labrax and Sparus aurata, but nowadays, a new valuable fish aquaculture is possible in this sector. Diplodus puntazzo, Dentex dentex and Sciena umbra are some of them. The importance of this study came from being the first in the literature that determines the shelf life for these species.

Ultrastructure of Enteromyxum leei (Diamant, Lom, & Dyková, 1994) (Myxozoa), an Enteric Parasite Infecting Gilthead Sea Bream (Sparus aurata) and Sharpsnout Sea Bream (Diplodus puntazzo)

The ultrastructure of the developmental stages of the myxozoan Enteromyxum leei parasitizing gilthead seabream (Sparus aurata) intestine and sharpsnout sea bream (Diplodus puntazzo) intestine and gallbladder are described. The earliest stage observed was a small dense trophozoite located among enterocytes. Proliferative stages, observed intercellularly in the epithelium of the intestine and gallbladder as well as in the lumen, possessed the typical cell-in-cell configuration throughout their development. Secondary cells were seen undergoing division within a common vacuolar membrane that also encompassed pairs of tertiary cells. Cytochemical studies showed that primary cells stored mainly lipids whereas secondary cells stored abundant beta-glycogen granules. Sporogonic development resembled that described for other disporous myxozoans. Within sporogonic stages, nonsporogonic secondary cells were observed accompanying two developing spores. Mature spores had a binucleated sporoplasm in which glycogen stores were abundant and no sporoplasmosomes were found. Our observations are discussed in relation to our knowledge on other myxozoans of the genus Enteromyxum.

Egg and sperm production and quality of sharpsnout sea bream (Diplodus puntazzo) in captivity

Egg production from captive-reared sharpsnout sea bream (Diplodus puntazzo) was monitored during the spawning seasons of 2003 to 2005, and sperm production during 2003. Spawning took place between September and December under water temperatures of 21.0–18.5 °C. Daily fecundity varied without a consistent trend and peak egg production occurred in October. Mean (±S.E.M.) number of spawning days per month was 20±3 in 2003, and 14±3 in 2004 and 2005. A significant (ANOVA, DNMR, P<0.01) drop was observed in mean total annual relative fecundity from 4.9±0.08 million eggs kg−1 female body weight in 2003, to 2.4±0.07 million eggs kg−1 in 2004 and 2005. Mean monthly fertilization success also dropped significantly from 81±1% in 2003 to 76±2% in 2004 and 78±2% in 2005. Annual hatching success did not vary significantly and was around 86±2%. Finally, 5 day larval survival decreased significantly from 85±2% in 2003 to 44±3% in 2004. The first spermiating males were found in August and sperm production continued until December. Mean total volume of expressible sperm was maximal in November (3±1 ml kg−1) and the gonadosomatic index (GSI) ranged between 0.6 and 2.0% in spermiating fish, reaching its peak in September–November. Sperm motility (%) remained unchanged during the season, whereas motility duration (6.2±1.7 min) and sperm density (2.7±0.2×1010 spermatozoa ml−1) peaked in October. Mean sperm survival ranged between 9 and 13 days during most of the spawning season, and decreased significantly to 5 days in December. The study suggests that egg production is stable for the first 3 months of the spawning season, with relatively unchanged egg quality. On the contrary, sperm production and quality peaks in the middle of the reproductive season in October.

Activity of the Digestive Protease, Chymotrypsin, in Larvae of the Cultured Sharpsnout Sea Bream (Diplodus puntazzo)

Specific and total activity of the digestive protease, chymotrypsin, was studied in cultured sharp- snout sea bream larvae (Diplodus puntazzo) for 35 days from hatching and in a variety of pH lev- els. Activity was detected upon hatching (2.8±0.34 mm total length), before the onset of exoge- nous feeding. Specific chymotrypsin activity exponentially increased from mouth opening on day 3 until day 25, then dropped until the end of the experiment. Total chymotrypsin activity sharply increased to day 10, then continued to increase, but slightly, until the end of the experiment. As expected, pH strongly affected both specific and total chymotryptic activity in the digestive tracts of larvae. Both were significantly lower when pH was acidic (1.5, 3.0, 4.0) than when it was alka- line (8.0, 9.0, 10.0) although there were no significant differences within either the acidic or the alkaline range. Our results indicate that chymotrypsin activity is capable of digesting protein before mouth opening and may be a valuable tool for better understanding the nutritional capa- bilities of young larvae.

Gonadal development and spawning cycle in the digynic hermaphrodite sharpsnout seabream Diplodus puntazzo (Sparidae) off the Canary Islands, northwest of Africa

Summary Diplodus puntazzo is a species characterized by a rudimentary hermaphroditism, with a low level of protandry. The study found that the overall sex ratio was one male to 2.03 females, diverging significantly from 1 : 1, and that there was a ratio of one male to 0.11 transitional fish. The sex ratio varied with season: during the reproductive period the ratio was 1 : 1.86 (male : female), significantly lower than in the non-reproductive period in which the sex ratio was approximately 1 : 2.26. Both sexes had similar size distributions; however, females were predominant in all size intervals, especially in the larger ones. No significant difference in mean total length (TL) between females (330 mm), males (319 mm) or transitionals (321 mm) was found. The smallest functional female and male analysed were 159 and 157 mm TL, and the largest were 520 and 510 mm TL, respectively. No significant difference in length at first level of maturity, attained at the second year of life, was found between males (281 mm) and females (292 mm), respectively. A protracted spawning season was identified for the species: from September to February, with a peak in November. GSI values followed the same pattern for males and females, with values of females being similar to those of males; the highest values occurred between September and December, with a maximum in November. Occurrence of transitional fish was significantly higher during the month with highest values of GSI than in the resting period. The study found that vitellogenesis did not begin synchronously for all females, and the simultaneous presence of oocytes in all stages of development indicated an asynchronous mode of ovarian development. The presence of postovulatory, together with tertiary yolk vesicle oocytes, indicated that the species is a multiple spawner.

Energy intake and macronutrient selection in sharpsnout seabream ( Diplodus puntazzo) challenged with fat dilution and fat deprivation using encapsulated diets

Sharpsnout seabream fed pure macronutrient capsules were challenged to fat dilution and fat deprivation in order to investigate the effects of fat level on energy intake regulation and macronutrient selection by fish, as they lack oropharyngeal chemosensory information from the diet. During the control phase, the fish were fed three individually encapsulated macronutrients, from which they composed a diet containing 67.36% protein (P), 19.08% carbohydrates (CH) and 13.57% fat (F), in terms of macronutrient weight intake percentage. During the second phase of the experiment, a lipid content reduction in F capsules from 55.0% to 13.4% did not significantly modify this selection pattern, energy ingestion or the number of capsules ingested of each macronutrient. During the third phase, in which they were subjected to fat deprivation, starting on almost the first day, the fish increased their total energy intake and total ingested number of capsules. These results reveal that fish are capable of distinguishing and selecting each of the three macronutrients contained in gelatine capsules, and that fish selection of a balanced diet from pure macronutrients is remarkably stable. Fish are capable of sustaining their macronutrient selection pattern and energy intake with very low amounts of fat in their diets (Phase 2). A certain instability in the initial P, CH and energy intake was only observed when fat was totally deprived (Phase 3), which resulted in higher values than those observed in Phase 1. In order to examine any possible effects of diet encapsulation, digestibility assays were performed in a second experiment. The fish were divided into two experimental groups and fed the same complete commercial diet, the only difference being the way it was presented to each group (pelleted or encapsulated). No statistical differences between the experimental groups were found with regards to both apparent digestibility coefficients and fish growth.

Histopathology and cellular response in Enteromyxum leei (Myxozoa) infections of Diplodus puntazzo (Teleostei)

Enteromyxum leei is an intestinal parasite responsible for serious outbreaks in Mediterranean sharpsnout sea bream Diplodus puntazzo. E. leei infection was experimentally transmitted to healthy D. puntazzo (R) by cohabitation with infected donor fish. Haematological changes and histopathological damage were evaluated in relation to the course of infection. The prevalence of infection in R fish was 100% from day 10 post-exposure (p.e.) onwards, and the infection intensity and histopathological damage increased progressively. Different developmental stages were found in the infected intestines, including proliferative (stages 1–3) and sporogonic (stages 4 and 5) stages. Intestinal damage consisted of vacuolation, necrosis, detachment and sloughing of epithelium, and was correlated with the progression of the infection and with the development of the parasite. Sporogonic stages appeared from day 20 p.e. onwards. Initially, D. puntazzo seems to counteract the infection through the increase in leucocyte numbers, respiratory burst activity, haematopoietic activity and MMC. Two types of eosinophilic granular cells (EGC1 and EGC2) were detected in the intestinal epithelium and lamina propria. EGC1 numbers decreased with the progression of infection, whereas an increase in EGC2 occurred, mainly in the lamina propria. The involvement of the cellular immunity in the response of D. puntazzo to E. leei was demonstrated. The depletion of this response at a certain point of the infection could contribute to the high virulence of this myxozoan in this fish species.

Effects of total replacement of fish oil by vegetable oils on n-3 and n-6 polyunsaturated fatty acid desaturation and elongation in sharpsnout seabream (Diplodus puntazzo) hepatocytes and enterocytes

The main aim of this work was to determine the impact of total dietary fish oil replacement by vegetable oils on the fatty acid metabolism of sharpsnout seabream hepatocytes and digestive tract enterocytes. Three isonitrogenous (48% crude protein) and isoenergetic (23 MJ/kg) experimental diets were formulated using three different lipid sources: fish oil (FO), rich in n-3 HUFAs; soybean oil (SO), rich in linoleic acid (LA), and linseed oil (LO), especially rich in linolenic acid (LNA). These diets were fed, three times a day to apparent satiation, to triplicate groups of 30 sharpsnout seabream (with an initial average weight of 14.9 g) for nine months at 23.5±1.2 °C. Inclusion of vegetable oils in sharpsnout seabream diet did not have any quantitative nutritional effects on desaturation/elongation of [1-14C] LNA and [1-14C] LA in isolated hepatocytes and total digestive tract enterocytes. Most of the radioactivity found in tissue lipid extracts (94% and 86% for hepatocytes and enterocytes, respectively) using silver nitrate thin-layer chromatography was recovered as [1-14C] C18 PUFA, clearly showing the lack of any significant desaturase/elongase activity in these cells. Only the high levels of HUFA in fish tissues pointed to the existence of some kind of regulatory mechanism, presumably based on HUFA bioaccumulation and C18 PUFA oxidation. Moreover, direct measurements of β-oxidation rates yielded very low values in all cases, the only significant difference being a higher oxidation rate in hepatocytes from fish fed LO versus FO diet.

Digestive enzyme activities in larvae of sharpsnout seabream ( Diplodus puntazzo)

The ontogenesis and specific activities of pancreatic and intestinal enzymes were investigated in sharpsnout sea bream, Diplodus puntazzo, during larval development until the end of weaning on day 50. The green-water technique was carried out for larval rearing in triplicate. Trypsin was first detected as early as hatching and sharply increased related to age and exogenous feeding until day 25, but a sharp decrease was observed towards the end of the experiment. Amylase was determined 2 days after hatching (DAH) and sharply increased to 10 DAH. Afterwards, slight decreases were found between 10 and 20 DAH and then slow alterations were continued until end of the experiment. Lipase was measured for the first time on day 4, and then slight increase was found to 25 DAH. After this date, slow variations were maintained until end of the experiment. Pepsin was firstly assayed 32 DAH related with stomach formation and sharply increased to 40 DAH. Then it was fluctuated until end of the experiment. Enzymes of brush border membranes, alkaline phosphatase and aminopeptidase N, showed similar pattern on specific activities during the first 10 days. Thereafter, while specific activity of alkaline phosphatase slightly decreased to 15 DAH and fluctuated until 20 DAH, aminopeptidase N activity slowly declined to 20 DAH. Afterwards, activity of alkaline phosphatase and aminopeptidase N were sharply increased to 30 DAH, showing maturation of the intestinal digestive process and also these activities continued to slight increase until end of the experiment. The specific activity of cytosolic peptidase, leucine-alanine peptidase sharply increased to on day 8, then suddenly declined to 12 DAH and further decreased until 20 DAH. After this date, in contrast to enzymes of brush border membranes, it sharply decreased to 25 DAH and continued to gradually decline until the end of the experiment. These converse expressions were indicative of a maturation of enterocytes and the transition to an adult mode of digestion.

Sharpsnout sea bream ( Diplodus puntazzo) humoral immune response against the parasite Enteromyxum leei (Myxozoa)

The humoral innate immune response of sharpsnout seabream Diplodus puntazzo against the myxozoan Enteromyxum leei was studied. Enteromyxosis was transmitted by cohabitation and a group of uninfected fish served as control. At 5, 12, 19, 26, 40 and 55 days post-exposure (p.e.), control and recipient fish were sampled to determine the prevalence of infection and some humoral innate immune parameters (antiprotease, antitumoral and peroxidase activities). Prevalence of infection was high from day 12 p.e. and reached 100% at days 40 and 55, when intensity of infection was medium to severe. The antiprotease activity was significantly increased in E. leei-exposed fish with respect to control fish at days 12 and 19 p.e. The serum antitumoral activity was slightly lower in recipient than in control fish at all sampling times, except at 40 days p.e., though no statistically significant differences were observed. Serum peroxidases were higher in all recipient fish than in control ones, with the highest stimulation index at 40 days p.e. Within recipient fish, no differences were detected between sampling times in any of the measured activities. The possible implication of these immune factors in the high susceptibility of D. puntazzo to this enteromyxosis is discussed.

Somatic indexes, chemical-nutritive characteristics and metal content in caught and reared sharpsnout seabream (iplodus puntazzo)

The aim of this study was to compare some somatic indexes, chemical-nutritive characteristics and the contents of some metals (Pb, Cu, Cr and Zn) in the whole body and fillet from caught and reared sharpsnout seabream (Diplodus puntazzo). The fish came from three different conditions: reared in marine cages (R), captured in a natural lagoon (L) and in the Mediterranean sea (S). Thirty fish per group, divided into three weight categories (100±15.3, 200±18.7 and 300±20.4g), were used for the trial.Reared sharpsnout seabream showed higher amounts of celomatic fat (3.41%, 2.43%, 0.21%, respectively for R, L and S) and total lipid (13.86%, 11.23% and 5.06% respectively for R, L and S), and lower moisture (64.14%, 65.54%, 71.53%) and protein (17.73, 19.03 and 19.17%) than those caught in the lagoon and sea. The whole body of reared fish contained lower amounts of lead (0.70, 0.75 and 0.97mg/kg, respectively for R, L and S), copper (0.15, 0.38, 0.25mg/kg) chrome (2.19, 3.52, 3.77mg/kg) and higher zinc contents (63.47, 53.42, 47.31mg/kg) than caught fish.Fatty acids from sharpsnout seabream fillets showed a high lipid quality as confirmed also by low values of Thrombogenic index (0.36, 0.30 and 0.22, respectively for L, S, R) and Atherogenic index (0.47, 0.42 and 0.33, respectively for L, S, R). Reared sharpsnout seabream showed lower saturated fatty acid values (26.44%, 32.21%, 34.85%, respectively for R, S, L) and higher oleic acid amount (21.61%, 19.15%, 11.99%, respectively for R, L and S). The subjects captured in the sea had a higher arachidonic acid content (5.44%, 1.76%, 0.59%, respectively for S, L, R).In the weight categories, the 100g subjects, showed higher incidence of viscera (VSI: 4.32%, 3.12% and 2.92%, respectively for 100, 200 and 300g) and liver (HIS: 2.20%, 1.97%, and 1.77%, respectively for 100, 200 and 300g), higher moisture (69.49%, 67.03%, 64.69%) and lower lipid rate (7.64%, 10.18%, 12.32%).

Fishmeal replacement by alfalfa protein concentrate in sharp snout sea bream Diplodus puntazzo

Fishmeal replacement by alfalfa protein concentrate in sharp snout sea bream Diplodus puntazzo

Mono- and duoculture of juvenile sharpsnout seabream Diplodus puntazzo (Cetti) and gilthead seabream Sparus aurata L. in a recirculated water system

Although the growth of intensively reared sharpsnout seabream Diplodus puntazzo (DP) has been suggested to improve in duoculture with gilthead seabream Sparus aurata (SA), the stocking ratio for most effective duoculture rearing has not been investigated. For this purpose, juvenile D. puntazzo (1.68±0.011 g) and S. aurata (1.43±0.007 g) were reared in duplicated groups of 165 specimens each, in two monoculture (100% DP, 100% SA) and four duoculture combinations (80% DP–20% SA, 60% DP–40% SA, 40% DP–60% SA, 20% DP–80% SA) for 96 days under recirculated water system conditions. Both species exhibited the highest growth when stocked at 20% and the poorest growth when stocked at 80%. For each species, no major differences for coefficient of weight variation and carcass proximate composition were detected. As the percentage of stocked S. aurata increased, D. puntazzo aggressiveness and weight variability of whole population were reduced, while total biomass, food consumption and food conversion ratio were increased. The results obtained are discussed in relation to fish behaviour and social interactions. From the fish farming point of view, it is indicated that under the present experimental conditions, juvenile S. aurata should be reared in monoculture and D. puntazzo in duoculture 40% DP–60% SA.

Effects of total replacement of fish oil by vegetable oils in the diets of sharpsnout seabream ( Diplodus puntazzo)

The aim of this study was to determine the impact of dietary replacement of fish oil by vegetable oils on sharpsnout seabream growth, nutritive utilization, somatic parameters, body composition, feed digestibility, and muscle fatty acid profile, as well as to make an estimate of its economic repercussions. To this end, three isonitrogenous (48% crude protein) and isoenergetic (23 MJ/kg) experimental diets were formulated, using three different lipid sources: fish oil (FO), soybean oil (SO) and linseed oil (LO). These diets were fed to triplicate groups of 30 sharpsnout seabream with an initial average weight of 14.9 g, three times a day to apparent satiation, over 92 days at 24.6 ± 1.1 °C. Our results show that the replacement of fish oil with soybean or linseed oil in sharpsnout seabream diets does not affect growth or feed utilization after three months of feeding. Fish on an SO diet exhibited higher hepatosomatic indices, whereas fillet percentages were significantly lower in fish that had been fed an FO diet. Apparent digestibility coefficients for dry matter, crude protein and crude lipid were significantly lower in fish that had consumed an LO diet. The muscle fatty acid composition reflected that of the diet. Consumption of vegetable oils reduced the muscle content of ARA (arachidonic acid), EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) to a lower degree than their corresponding reductions in the diet after fish oil replacement, which highlights their importance. Vegetable oils also increased the muscle content of linoleic and linolenic acids. In terms of economic performance, the SO diet was the least expensive diet, and had the best economic conversion ratio.

Age and growth of the sharpsnout seabream Diplodus puntazzo (Cetti, 1777) inhabiting the Canarian archipelago, estimated by reading otoliths and by backcalculation

The yearly nature in growth increment formation in the otoliths of Diplodus puntazzo aged 1–10 years from the Canary Islands was validated. Each translucent zone in the otoliths represented an annulus with a year's growth represented by an opaque and its adjacent hyaline zone. Lengths at age were described by the specialised von Bertalanffy growth model ( L ∞ = 541 mm, k = 0.182 year −1, and t 0 = −2.531 years), the Schnute growth model ( y 1 = 171 mm, y 2 = 509 mm, a = 0.022, b = 2.59) and the seasonalised von Bertalanffy growth model ( L ∞ = 546 mm, k = 0.176 year −1, t 0 = −2.21 years, C = 0.712, t s = 0.798). Individuals grow fast during the first year of life, attaining approximately 45% of their maximum length. The body proportional hypothesis and the power length–radius relationship used to backcalculate the growth trajectories showed that the growth backcalculation model could be used to provide reasonable estimates of growth in this species. A power relationship ( a = 36.19 and v = 1.705) was estimated between the total length and the otolith radius. Backcalculated lengths were similar to those predicted by the growth models. Growth parameters estimated from the backcalculated lengths at age were: L ∞ = 508 mm, k = 0.197 year −1, t 0 = −1.731 years. Data on length and age used to estimate the parameters of the von Bertalanffy growth model showed that males and females have similar growth rates.

Effects of partial replacement of fish meal by soybean meal in sharpsnout seabream ( Diplodus puntazzo) diet

We have studied the possible use of soybean meal (SM) in sharpsnout seabream diets by progressively increasing its inclusion level (0%, 20%, 40% and 60%) at the expense of fish meal in isonitrogenous (45%) and isoenergetic formulated (20 MJ/kg) diets. Fish of two different sizes (48 g and 195 g of initial weight) were kept in seawater tanks (26 °C on average) and fed to satiety until they reached a weight of 118 g and 340 g, after 64 and 91 days respectively. Feed consumption increased along with the soybean meal content of the diet, the differences becoming statistically significant in smaller animals as from 40% of inclusion. In larger animals, the diet containing the highest level of soybean meal produced the lowest final weight. As the soybean meal content increased, feeding efficiency and protein utilization of the diet decreased, an effect probably due to the smaller digestibility coefficient observed for these diets. Based on the results of the sensory test, flesh quality was very little affected, albeit fish feeding on diets with partial replacement of fish meal tended to be somewhat softer. Despite extending the fattening period required to reach the same final weight, the economic analysis indicates that inclusion of soybean meal in the diet reduces feeding costs.

Macronutrient selection through post-ingestive signals in sharpsnout seabream fed gelatine capsules and challenged with protein dilution

Sharpsnout seabream ability for macronutrient self-selection was studied using gelatine capsules containing pure macronutrients. In particular, the existence of non-oropharyngeal chemosensory pathways involved on protein (P), fat (F) and carbohydrate (CH) selection, as well as sharpsnout seabream response to dietary protein dilution were investigated. In a sequence of experimental phases, sharpsnout seabream were fed a pelleted complete diet, an encapsulated complete diet or a combination of separately encapsulated pure macronutrients. In order to induce associative learning, capsules containing a given macronutrient were paired with a particular colour. The animals composed a diet containing 62.7% P, 21.3% CH and 16.0% F, in terms of macronutrient percentage intake, and this selection pattern was maintained throughout all experimental phases. In a second experiment, individually kept sharpsnout seabream were challenged with protein dilution. After protein capsules were diluted (from 91.9% P to 56.3% P) with cellulose, the animals increased their protein intake to compensate for dilution in such a way that their energy intake was not significantly modified (17.4 kJ/100 g BW vs. 17.6 kJ/100 g BW after dilution). These results show that sharpsnout seabream feeding on encapsulated diets are able to select and maintain a particular diet composition, as well as sustain their energy intake, without using the diet's oropharyngeal chemosensory properties. Moreover, they were also able to maintain their protein intake after dilution, which highlights the importance of this macronutrient in this omnivorous species.

Experimental transmission of Enteromyxum leei Diamant, Lom and Dykova, 1994 in sharpsnout sea bream, Diplodus puntazzo C. and the effect on some innate immune parameters

Enteromyxum leei has been implicated in outbreaks in sharpsnout sea bream, causing a serious economic impact on Mediterranean fish farming. Information about transmission and life cycles of marine myxosporea is limited to only a few fish species. In the present study, direct transmission of the infection was achieved by cohabitation of infected and healthy Diplodus puntazzo C. for the first time. The progress of the infection was monitored by the detection of different developmental stages of the parasite in the posterior intestine. Infected fish with E. leei were firstly observed in day 5 (prevalence of 20%). The total prevalence reached 100% in day 19 and was maintained in this high level until the end of the experimental period (day 55). In addition, the initial intensity of the different parasite stages was low, but on day 26 the intensity of trophozoites was suddenly increased, followed by the increased intensity of sporoblasts and mature spores. Also, the experimental transmission of E. leei in recovered D. puntazzo previously treated for parasite elimination proved to be unsuccessful, suggesting of a possible development of protective immunity against the parasite.

Meristic character counts and incidence of skeletal anomalies in the wild Diplodus puntazzo (Cetti, 1777) of an area of the south-eastern Mediterranean Sea

The sharpsnout seabream (Diplodus puntazzo, Cetti 1777) is a species rarely found in coastal areas of Sicily, but is important in Mediterranean aquaculture. In order to detect the number of meristic characters and the main types of body deformation, 588 specimens of sharpsnout seabream were collected from a coastal zone of south-east Sicily (Licata, AG—Italy). Different sized classes were examined and the relationship between size and the number of meristic characters (number of fin rays) was found. The number of vertebrae, anal fin hard rays and dorsal fin hard rays was constant and did not vary with size. Seventeen types of skeletal and fin anomalies were observed, but no grave anomalies were found, such as the absence of a swimbladder, lordosis, kyphosis and calculi in the terminal tract of the urinary duct. The most prevalent anomalies were associated with the fins, especially E7 (pectoral fin rays), F7 (anal fin rays) and I7 (dorsal fin soft rays). There was no correlation between frequency of anomaly and size class. The malformation index was 4.54.